\par
\section{Prototypes and descriptions of {\tt FrontMtx} methods}
\label{section:FrontMtx:proto}
\par
This section contains brief descriptions including prototypes
of all methods that belong to the {\tt FrontMtx} object.
\par
\subsection{Basic methods}
\label{subsection:FrontMtx:proto:basics}
\par
As usual, there are four basic methods to support object creation,
setting default fields, clearing any allocated data, and free'ing
the object.
\par
%=======================================================================
\begin{enumerate}
%-----------------------------------------------------------------------
\item
\begin{verbatim}
FrontMtx * FrontMtx_new ( void ) ;
\end{verbatim}
\index{FrontMtx_new@{\tt FrontMtx\_new()}}
This method simply allocates storage for the {\tt FrontMtx} structure 
and then sets the default fields by a call to 
{\tt FrontMtx\_setDefaultFields()}.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
void FrontMtx_setDefaultFields ( FrontMtx *frontmtx ) ;
\end{verbatim}
\index{FrontMtx_setDefaultFields@{\tt FrontMtx\_setDefaultFields()}}
The structure's fields are set to default values:
{\tt nfront}, {\tt neqns}, {\tt nentD}, {\tt nentL}, {\tt nentU}  and
{\tt nlocks} are set to zero.
Five scalars are set to their default values,
\begin{center}
\begin{tabular}{lcl}
{\tt type}         & = &  {\tt SPOOLES\_REAL} \\
{\tt symmetryflag} & = &  {\tt SPOOLES\_SYMMETRIC} \\
{\tt sparsityflag} & = &  {\tt FRONTMTX\_DENSE\_FRONTS} \\
{\tt pivotingflag} & = &  {\tt SPOOLES\_NO\_PIVOTING} \\
{\tt dataMode}     & = &  {\tt FRONTMTX\_1D\_MODE}
\end{tabular}
\end{center}
and the structure's pointers are set to {\tt NULL}.
% {\tt tree},
% {\tt frontETree},
% {\tt symbfacIVL},
% {\tt frontsizesIV},
% {\tt rowadjIVL},
% {\tt coladjIVL},
% {\tt lowerblockIVL},
% {\tt upperblockIVL},
% {\tt p\_mtxDJJ},
% {\tt p\_mtxUJJ},
% {\tt p\_mtxUJN},
% {\tt p\_mtxLJJ},
% {\tt p\_mtxLNJ},
% {\tt lowerhash},
% {\tt upperhash} and
% {\tt lock}
% are set to {\tt NULL} .
\par \noindent {\it Error checking:}
If {\tt frontmtx} is {\tt NULL},
an error message is printed and the program exits.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
void FrontMtx_clearData ( FrontMtx *frontmtx ) ;
\end{verbatim}
\index{FrontMtx_clearData@{\tt FrontMtx\_clearData()}}
This method clears the object and free's any owned data
by invoking the {\tt \_clearData()} methods for its internal
{\tt IV} and {\tt IVL} objects, ({\it not} including
the {\tt frontETree} and {\tt symbfacIVL} objects that are not
owned by this {\tt FrontMtx} object).
If the {\tt lock} pointer is not {\tt NULL}, the lock is destroyed
via a call to {\tt Lock\_free()} and its storage is then
free'd.
There is a concluding call to {\tt FrontMtx\_setDefaultFields()}.
\par \noindent {\it Error checking:}
If {\tt frontmtx} is {\tt NULL},
an error message is printed and the program exits.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
void FrontMtx_free ( FrontMtx *frontmtx ) ;
\end{verbatim}
\index{FrontMtx_free@{\tt FrontMtx\_free()}}
This method releases any storage by a call to 
{\tt FrontMtx\_clearData()} and then free the space for {\tt frontmtx}.
\par \noindent {\it Error checking:}
If {\tt frontmtx} is {\tt NULL},
an error message is printed and the program exits.
%-----------------------------------------------------------------------
\end{enumerate}
\par
\subsection{Instance methods}
\label{subsection:FrontMtx:proto:instance}
\par
%=======================================================================
\begin{enumerate}
%-----------------------------------------------------------------------
\item
\begin{verbatim}
int FrontMtx_nfront ( FrontMtx *frontmtx ) ;
\end{verbatim}
\index{FrontMtx_nfront@{\tt FrontMtx\_nfront()}}
This method returns the number of fronts in the matrix.
\par \noindent {\it Error checking:}
If {\tt frontmtx} is {\tt NULL},
an error message is printed and the program exits.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
int FrontMtx_neqns ( FrontMtx *frontmtx ) ;
\end{verbatim}
\index{FrontMtx_neqns@{\tt FrontMtx\_neqns()}}
This method returns the number of equations in the matrix.
\par \noindent {\it Error checking:}
If {\tt frontmtx} is {\tt NULL},
an error message is printed and the program exits.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
Tree * FrontMtx_frontTree ( FrontMtx *frontmtx ) ;
\end{verbatim}
\index{FrontMtx_frontTree@{\tt FrontMtx\_frontTree()}}
This method returns the {\tt Tree} object for the fronts.
\par \noindent {\it Error checking:}
If {\tt frontmtx} is {\tt NULL},
an error message is printed and the program exits.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
void FrontMtx_initialFrontDimensions ( FrontMtx *frontmtx, int J,
                          int *pnD, int *pnL, int *pnU, int *pnbytes ) ;
\end{verbatim}
\index{FrontMtx_initialFrontDimensions@{\tt FrontMtx\_initialFrontDimensions()}}
This method fills the four pointer arguments with the number of 
internal rows and columns, number of rows in the lower block,
number of columns in the upper block, and number of bytes for a
{\tt Chv} object to hold the front.
in front {\tt J}.
\par \noindent {\it Error checking:}
If {\tt frontmtx} is {\tt NULL},
or if {\tt J} is not in {\tt [0,nfront)},
or if any of the four pointer arguments are NULL,
an error message is printed and the program exits.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
int FrontMtx_frontSize ( FrontMtx *frontmtx, int J ) ;
\end{verbatim}
\index{FrontMtx_frontSize@{\tt FrontMtx\_frontSize()}}
This method returns the number of internal rows and columns
in front {\tt J}.
\par \noindent {\it Error checking:}
If {\tt frontmtx} or {\tt frontsizesIV} is {\tt NULL},
or if {\tt J} is not in {\tt [0,nfront)},
an error message is printed and the program exits.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
void FrontMtx_setFrontSize ( FrontMtx *frontmtx, int J, int size ) ;
\end{verbatim}
\index{FrontMtx_setFrontsize@{\tt FrontMtx\_setFrontSize()}}
This method sets the number of internal rows and columns
in front {\tt J} to be {\tt size}.
This method is used during factorizations with pivoting enabled
since we cannot tell ahead of time how many rows and columns in a
front will be eliminated.
\par \noindent {\it Error checking:}
If {\tt frontmtx} or {\tt frontsizesIV} is {\tt NULL},
or if {\tt J} is not in {\tt [0,nfront)},
or if ${\tt size} < 0$,
an error message is printed and the program exits.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
void FrontMtx_columnIndices ( FrontMtx *frontmtx, int J,
                              int *pncol, int **pindices ) ;
\end{verbatim}
\index{FrontMtx_columnIndices@{\tt FrontMtx\_columnIndices()}}
This method fills {\tt *pncol} with the number of columns
and {\tt *pindices} with a pointer to the column indices for front
{\tt J}.
\par \noindent {\it Error checking:}
If {\tt frontmtx}, {\tt pncol} or {\tt pindices} is {\tt NULL},
or if {\tt J} is not in {\tt [0,nfront)},
an error message is printed and the program exits.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
void FrontMtx_rowIndices ( FrontMtx *frontmtx, int J,
                           int *pnrow, int **pindices ) ;
\end{verbatim}
\index{FrontMtx_rowIndices@{\tt FrontMtx\_rowIndices()}}
This method fills {\tt *pnrow} with the number of rows
and {\tt *pindices} with a pointer to the row indices for front
{\tt J}.
\par \noindent {\it Error checking:}
If {\tt frontmtx}, {\tt pnrow} or {\tt pindices} is {\tt NULL},
or if {\tt J} is not in {\tt [0,nfront)},
an error message is printed and the program exits.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
SubMtx * FrontMtx_diagMtx ( FrontMtx *frontmtx, int J ) ;
\end{verbatim}
\index{FrontMtx_diagMtx@{\tt FrontMtx\_diagMtx()}}
This method returns a pointer to the object that contains
submatrix $D_{J,J}$.
\par \noindent {\it Error checking:}
If {\tt frontmtx} is {\tt NULL},
or if {\tt J} is not in {\tt [0,nfront)},
an error message is printed and the program exits.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
SubMtx * FrontMtx_upperMtx ( FrontMtx *frontmtx, int J, int K ) ;
\end{verbatim}
\index{FrontMtx_upperMtx@{\tt FrontMtx\_upperMtx()}}
This method returns a pointer to the object that contains
submatrix $U_{J,K}$.
If $K = nfront$, then the object containing $U_{J,\bnd{J}}$ is
returned.
\par \noindent {\it Error checking:}
If {\tt frontmtx} is {\tt NULL},
or if {\tt J} is not in {\tt [0,nfront)},
or if {\tt K} is not in {\tt [0,nfront]},
an error message is printed and the program exits.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
SubMtx * FrontMtx_lowerMtx ( FrontMtx *frontmtx, int K, int J ) ;
\end{verbatim}
\index{FrontMtx_lowerMtx@{\tt FrontMtx\_lowerMtx()}}
This method returns a pointer to the object that contains
submatrix $L_{K,J}$.
If $K = nfront$, then the object containing $L_{\bnd{J},J}$ is
returned.
\par \noindent {\it Error checking:}
If {\tt frontmtx} is {\tt NULL},
or if {\tt J} is not in {\tt [0,nfront)},
or if {\tt K} is not in {\tt [0,nfront]},
an error message is printed and the program exits.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
void FrontMtx_lowerAdjFronts ( FrontMtx *frontmtx, int J, 
                               int *pnadj, int **padj ) ;
\end{verbatim}
\index{FrontMtx_lowerAdjFronts@{\tt FrontMtx\_lowerAdjFronts()}}
This method fills {\tt *pnadj} with the number of fronts adjacent to 
{\tt J} in $L$ and fills {\tt *padj} with a pointer to the first
entry of a vector containing the ids of the adjacent fronts.
\par \noindent {\it Error checking:}
If {\tt frontmtx}, {\tt pnadj} or {\tt ppadj} is {\tt NULL},
or if {\tt J} is not in {\tt [0,nfront)},
an error message is printed and the program exits.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
void FrontMtx_upperAdjFronts ( FrontMtx *frontmtx, int J, 
                               int *pnadj, int **padj ) ;
\end{verbatim}
\index{FrontMtx_upperAdjFronts@{\tt FrontMtx\_upperAdjFronts()}}
This method fills {\tt *pnadj} with the number of fronts adjacent to 
{\tt J} in $U$ and fills {\tt *padj} with a pointer to the first
entry of a vector containing the ids of the adjacent fronts.
\par \noindent {\it Error checking:}
If {\tt frontmtx}, {\tt pnadj} or {\tt ppadj} is {\tt NULL},
or if {\tt J} is not in {\tt [0,nfront)},
an error message is printed and the program exits.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
int FrontMtx_nLowerBlocks ( FrontMtx *frontmtx ) ;
\end{verbatim}
\index{FrontMtx_nLowerBlocks@{\tt FrontMtx\_nLowerBlocks()}}
This method returns the number of nonzero $L_{K,J}$ submatrices.
\par \noindent {\it Error checking:}
If {\tt frontmtx} is {\tt NULL},
an error message is printed and the program exits.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
int FrontMtx_nUpperBlocks ( FrontMtx *frontmtx ) ;
\end{verbatim}
\index{FrontMtx_nUpperBlocks@{\tt FrontMtx\_nUpperBlocks()}}
This method returns the number of nonzero $U_{J,K}$ submatrices.
\par \noindent {\it Error checking:}
If {\tt frontmtx} is {\tt NULL},
an error message is printed and the program exits.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
IVL * FrontMtx_upperBlockIVL ( FrontMtx *frontmtx ) ;
\end{verbatim}
\index{FrontMtx_upperBlockIVL@{\tt FrontMtx\_upperBlockIVL()}}
This method returns a pointer to the {\tt IVL} object that holds
the upper blocks.
\par \noindent {\it Error checking:}
If {\tt frontmtx} is {\tt NULL},
an error message is printed and the program exits.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
IVL * FrontMtx_lowerBlockIVL ( FrontMtx *frontmtx ) ;
\end{verbatim}
\index{FrontMtx_lowerBlockIVL@{\tt FrontMtx\_lowerBlockIVL()}}
This method returns a pointer to the {\tt IVL} object that holds
the lower blocks.
\par \noindent {\it Error checking:}
If {\tt frontmtx} is {\tt NULL},
an error message is printed and the program exits.
%-----------------------------------------------------------------------
\end{enumerate}
\par
\subsection{Initialization methods}
\label{subsection:FrontMtx:proto:initialization}
\par
%=======================================================================
\begin{enumerate}
%-----------------------------------------------------------------------
\item
\begin{verbatim}
void FrontMtx_init ( FrontMtx *frontmtx, ETree *frontETree, 
          IVL *symbfacIVL, int type, int symmetryflag, int sparsityflag,
          int pivotingflag, int lockflag, int myid, IV *ownersIV, 
          SubMtxManager *manager, int msglvl, FILE *msgFile ) ;
\end{verbatim}
\index{FrontMtx_init@{\tt FrontMtx\_init()}}
This method initializes the object, allocating and initializing the 
internal objects as necessary.
See the previous section on data structures for the meanings of the
{\tt type}, {\tt symmetryflag}, {\tt sparsityflag} and 
{\tt pivotingflag} parameters.
The {\tt lockflag} parameter has the following meaning.
\begin{itemize}
\item {\tt 0} --- the {\tt Lock} object is not allocated 
                  or initialized.
\item {\tt 1} --- the {\tt Lock} object is allocated and initialized 
                  to synchronize only threads in this process.
\item {\tt 2} --- the {\tt Lock} object is allocated and initialized 
                  to synchronize threads in this and other processes.
\end{itemize}
If {\tt lockflag} is not {\tt 0}, the lock is allocated and
initialized.
\par
This method allocates as much storage as possible.
When pivoting is not enabled and dense fronts are stored 
the structure of the factor matrix is fixed and given by the 
{\tt frontETree} object.
The diagonal $D_{J,J}$, 
upper triangular $U_{J,J}$ and $U_{J,\bnd{J}}$ matrices,
and lower triangular $L_{J,J}$ and $L_{\bnd{J},J}$ matrices
are allocated.
\par
The {\tt myid} and {\tt ownersIV} parameters are used in
a distributed environment where we specify which process
owns each front. When we can preallocate data structures
(when there is no pivoting and dense fronts are stored) we
need each process to determine what parts of the data it
can allocate and set up. In a serial or multithreaded 
environment, use {\tt ownersIV = NULL}.
\par \noindent {\it Error checking:}
If {\tt frontmtx}, {\tt frontETree} or {\tt symbfacIVL} is {\tt NULL},
or if {\tt type}, {\tt symmetryflag}, {\tt sparsityflag} 
or {\tt pivotingflag} are not valid,
or if {\tt lockflag} is not {\tt 0}, {\tt 1} or {\tt 2},
or if {\tt ownersIV} is not {\tt NULL} and {\tt myid < 0},
an error message is printed and the program exits.
%-----------------------------------------------------------------------
\end{enumerate}
\par
\subsection{Utility Factorization methods}
\label{subsection:FrontMtx:proto:utility-factor}
\par
The following methods are called by all the factor methods
--- serial, multithreaded and MPI.
\par
%=======================================================================
\begin{enumerate}
%-----------------------------------------------------------------------
\item
\begin{verbatim}
void FrontMtx_initializeFront ( FrontMtx *frontmtx, Chv *frontJ, int J ) ;
\end{verbatim}
\index{FrontMtx_initializeFront@{\tt FrontMtx\_initializeFront()}}
This method is called to initialize a front.
The number of internal rows and columns is found from the front
{\tt ETree} object and the row and column indices are obtained 
from the symbolic factorization {\tt IVL} object.
The front {\tt Chv} object is initialized via a call to 
{\tt Chv\_init()}, and the column indices and row indices (when
nonsymemtric) are copied.
Finally the front's entries are zeroed via a call to 
{\tt Chv\_zero()}.
\par \noindent {\it Error checking:}
None presently.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
char FrontMtx_factorVisit ( FrontMtx *frontmtx, Pencil *pencil, int J,
   int myid, int owners[], Chv *fronts[], int lookahead, double tau,
   double droptol, char status[], IP *heads[], IV *pivotsizesIV, DV *workDV, 
   int parent[], ChvList *aggList, ChvList *postList, ChvManager *chvmanager, 
   int stats[], double cpus[], int msglvl, FILE *msgFile ) ;
\end{verbatim}
\index{FrontMtx_factorVisit@{\tt FrontMtx\_factorVisit()}}
This method is called during the serial, multithreaded and MPI
factorizations when front {\tt J} is visited during the bottom-up
traversal of the tree.
\par \noindent {\it Error checking:}
None presently.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
Chv * FrontMtx_setupFront ( FrontMtx *frontmtx, Pencil *pencil, int J,
                         int myid, int owners[], ChvManager *chvmanager,
                         double cpus[], int msglvl, FILE *msgFile ) ;
\end{verbatim}
\index{FrontMtx_setupFront@{\tt FrontMtx\_setupFront()}}
This method is called by {\tt FrontMtx\_visitFront()} to initialize
the front's {\tt Chv} object and load original entries if applicable.
\par \noindent {\it Error checking:}
None presently.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
IP ** FrontMtx_factorSetup ( FrontMtx *frontmtx, IV *frontOwnersIV,
                             int myid, int msglvl, FILE *msgFile ) ;
\end{verbatim}
\index{FrontMtx_factorSetup@{\tt FrontMtx\_factorSetup()}}
This method is called by the serial, multithreaded and MPI
factorizations methods to initialize a data structure that contains
the front-to-front updates that this thread or processor will perform.
The data structure is a vector of pointers to {\tt IP} objects that
holds the heads of list of updates for each front.
\par \noindent {\it Error checking:}
None presently.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
int * FrontMtx_nactiveChild ( FrontMtx *frontmtx, char *status, int myid ) ;
\end{verbatim}
\index{FrontMtx_nactiveChild@{\tt FrontMtx\_nactiveChild()}}
This method is called by the multithreaded and MPI factorizations
to create an integer vector that contains the number of active
children of each front with respect to this thread or processor.
\par \noindent {\it Error checking:}
If {\tt frontmtx} or {\tt status} is {\tt NULL},
or if ${\tt myid} < 0$,
an error message is printed and the program exits.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
Ideq * FrontMtx_setUpDequeue ( FrontMtx *frontmtx, int owners[], int myid, 
                               char status[], IP *heads[], char activeFlag,
                               char inactiveFlag, int msglvl, FILE *msgFile ) ;
\end{verbatim}
\index{FrontMtx_nactiveChild@{\tt FrontMtx\_nactiveChild()}}
This method is called by the multithreaded and MPI factorizations
to create and return an integer dequeue object to schedule the bottom-up
traversal of the front tree.
\par \noindent {\it Error checking:}
If {\tt frontmtx}, {\tt owners} or {\tt status} is {\tt NULL},
or if ${\tt myid} < 0$,
an error message is printed and the program exits.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
void FrontMtx_loadActiveLeaves ( FrontMtx *frontmtx, char status[],
                                 char activeFlag, Ideq *dequeue ) ;
\end{verbatim}
\index{FrontMtx_loadActiveLeaves@{\tt FrontMtx\_loadActiveLeaves()}}
This method is called by the multithreaded and MPI factor and solve
methods to load the dequeue with the active leaves in the front
tree with respect to the thread or processor.
\par \noindent {\it Error checking:}
None presently.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
ChvList * FrontMtx_postList ( FrontMtx *frontmtx, IV *frontOwnersIV,
                              int lockflag ) ;
\end{verbatim}
\index{FrontMtx_postList@{\tt FrontMtx\_postList()}}
This method is called by the multithreaded and MPI factor 
methods to create and return a list object to hold postponed
chevrons and help synchronize the factorization.
\par \noindent {\it Error checking:}
None presently.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
ChvList * FrontMtx_aggregateList ( FrontMtx *frontmtx,
                                   IV *frontOwnersIV, int lockflag ) ;
\end{verbatim}
\index{FrontMtx_aggregateList@{\tt FrontMtx\_aggregateList()}}
This method is called by the multithreaded factor 
methods to create and return a list object to hold aggregate
fronts and help synchronize the factorization.
There is an analogous {\tt FrontMtx\_MPI\_aggregateList()} method
for the MPI environment.
\par \noindent {\it Error checking:}
If {\tt frontmtx} or {\tt frontOwnersIV} is {\tt NULL},
or if {\tt lockflag} is invalid,
an error message is printed and the program exits.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
void FrontMtx_loadEntries ( Chv *frontJ, DPencil *pencil, 
                            int msglvl, FILE *msgFile) ;
\end{verbatim}
\index{FrontMtx_loadEntries@{\tt FrontMtx\_loadEntries()}}
This method is called to load the original entries into a front.
\par \noindent {\it Error checking:}
If {\tt frontJ} is {\tt NULL},
or if {\tt msglvl > 0} and {\tt msgFile} is {\tt NULL},
an error message is printed and the program exits.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
void FrontMtx_update ( FrontMtx *frontmtx, Chv *frontJ, IP *heads[], 
                       char status[], DV *tempDV, int msglvl, FILE *msgFile) ;
\end{verbatim}
\index{FrontMtx_update@{\tt FrontMtx\_update()}}
This method is called to update the current front stored in {\tt frontJ}
from all descendent fronts.
(For the multithreaded and MPI factorizations, updates come from
all owned descendent fronts.)
The {\tt heads[]} vector maintains the linked list of completed 
fronts that still have ancestors to update.
The {\tt tempDV} object is used as working storage by the {\tt Chv}
update methods, its size is automatically resized.
When pivoting is disabled, the maximum size of the {\tt tempDV}
object is three times the maximum number of internal rows and columns
in a front.
\par \noindent {\it Error checking:}
None presently.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
Chv * FrontMtx_assemblePostponedData ( FrontMtx *frontmtx, Chv *frontJ, 
           ChvList *postponedlist, ChvManager *chvmanager, int *pndelay) ;
\end{verbatim}
\index{FrontMtx_assemblePostponedData@{\tt FrontMtx\_assemblePostponedData()}}
This method is called to assemble any postponed data 
from its children fronts into the current front.
{\tt frontJ} contains the updates from the descendents.
Any postponed data is found in the list in {\tt postponedlist}.
If this list is empty, a new front is created to hold the aggregate
updates and the postponed data, and 
the {\tt chvmanager} object receives the aggregate and postponed {\tt
Chv} objects.
The number of delayed rows and columns is returned in {\tt *pndelay}
--- this is used during the factorization of the front that
follows immediately.
\par \noindent {\it Error checking:}
None presently.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
FrontMtx_storePostponedData ( FrontMtx *frontmtx, Chv *frontJ, 
    int npost, int K, ChvList *postponedlist, ChvManager *chvmanager ) ;
\end{verbatim}
\index{FrontMtx_storePostponedData@{\tt FrontMtx\_storePostponedData()}}
This method is used to store any postponed rows and columns from
the current front {\tt frontJ} into a {\tt Chv} object obtained
from the {\tt chvmanager} object and place it into the list of
postponed objects for {\tt K}, its parent, found in the {\tt
postponedlist} object.
The {\tt frontJ} object is unchanged by this method.
\par \noindent {\it Error checking:}
None presently.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
FrontMtx_storeFront ( FrontMtx *frontmtx, Chv *frontJ, IV *pivotsizesIV,
                      double droptol, int msglvl, FILE *msgFile ) ;
\end{verbatim}
\index{FrontMtx_storeFront@{\tt FrontMtx\_storeFront()}}
This method is used to store the eliminated rows and columns of the
current front {\tt frontJ} into the factor matrix storage.
\par \noindent {\it Error checking:}
None presently.
%-----------------------------------------------------------------------
\end{enumerate}
\par
\subsection{Serial Factorization method}
\label{subsection:FrontMtx:proto:factor}
There are two factorization methods: the first is for factoring
a matrix $A$ stored in a {\tt DInpMtx} object, the second factors
a linear combination $A + \sigma B$ stored in a {\tt DPencil} object.
\par
%=======================================================================
\begin{enumerate}
%-----------------------------------------------------------------------
\item
\begin{verbatim}
Chv * FrontMtx_factorInpMtx ( FrontMtx *frontmtx, InpMtx *inpmtx, double tau, 
                   double droptol, ChvManager *chvmanager, int *perror, 
                   double cpus[], int stats[],  int msglvl, FILE *msgFile ) ;
Chv * FrontMtx_factorPencil ( FrontMtx *frontmtx, Pencil *pencil, double tau, 
                   double droptol, ChvManager *chvmanager, int *perror, 
                   double cpus[], int stats[],  int msglvl, FILE *msgFile ) ;
\end{verbatim}
\index{FrontMtx_factorInpMtx@{\tt FrontMtx\_factorInpMtx()}}
\index{FrontMtx_factorPencil@{\tt FrontMtx\_factorPencil()}}
These two serial factorization methods factor a matrix $A$ 
(stored in {\tt inpmtx}) or
a matrix pencil $A + \sigma B$ (stored in {\tt pencil}).
The {\tt tau} parameter is used when pivoting is enabled, each
entry in $U$ and $L$ (when nonsymmetric) will have magnitude less
than or equal to {\tt tau}.
The {\tt droptol} parameter is used when the fronts are stored in
a sparse format, each entry in $U$ and $L$ (when nonsymmetric) 
will have magnitude greater than or equal to {\tt droptol}.
\par
The return value is a pointer to the first element in a list of
{\tt Chv} objects that contain the rows and columns that were
not able to be eliminated.
In all present cases, this should be {\tt NULL}; we have left this
return value as a hook to future factorizations via stages.
The {\tt perror} parameter is an address that is filled with an
error code on return.
If the factorization has completed, then {\tt *perror} is a
negative number.
If {\tt *perror} is in the range {\tt [0,nfront)}, then an error
has been detected at front {\tt *perror}.
On return, the {\tt cpus[]} vector is filled with the following
information.
\begin{itemize}
\item
{\tt cpus[0]} --- time spent initializing the fronts.
\item
{\tt cpus[1]} --- time spent loading the original entries.
\item
{\tt cpus[2]} --- time spent accumulating updates from descendents.
\item
{\tt cpus[3]} --- time spent assembling postponed data.
\item
{\tt cpus[4]} --- time spent to factor the fronts.
\item
{\tt cpus[5]} --- time spent to extract postponed data.
\item
{\tt cpus[6]} --- time spent to store the factor entries.
\item
{\tt cpus[7]} --- miscellaneous time.
\item
{\tt cpus[8]} --- total time in the method.
\end{itemize}
On return, the {\tt stats[]} vector is filled with the following
information.
\begin{itemize}
\item
{\tt stats[0]} --- number of pivots.
\item
{\tt stats[1]} --- number of pivot tests.
\item
{\tt stats[2]} --- number of delayed rows and columns.
\item
{\tt stats[3]} --- number of entries in $D$.
\item
{\tt stats[4]} --- number of entries in $L$.
\item
{\tt stats[5]} --- number of entries in $U$.
\end{itemize}
\par \noindent {\it Error checking:}
If {\tt frontmtx}, {\tt pencil}, {\tt cpus} or {\tt stats} 
is {\tt NULL},
or if {\tt msglvl > 0} and {\tt msgFile} is {\tt NULL},
an error message is printed and the program exits.
%-----------------------------------------------------------------------
\end{enumerate}
\par
\subsection{QR factorization utility methods}
\label{subsection:FrontMtx:proto:utilityQR}
\par
%=======================================================================
\begin{enumerate}
%-----------------------------------------------------------------------
\item
\begin{verbatim}
void FrontMtx_QR_setup ( FrontMtx *frontmtx, InpMtx *mtxA, IVL **prowsIVL,
                         int **pfirstnz, int msglvl, FILE *msgFile ) ;
\end{verbatim}
\index{FrontMtx_QR_setup@{\tt FrontMtx\_QR\_setup()}}
This method sets up the {\tt rowsIVL} and {\tt firstnz[]} data
structures.
The address of {\tt rowsIVL} is placed in {\tt *prowsIVL}
and the address of {\tt firstnz} is placed in {\tt *pfirstnz}.
List {\tt J} of {\tt rowsIVL} contains the rows of $A$ that will be
assembled into front {\tt J}.
The leading column with a nonzero entry in row {\tt j} is found in
{\tt firstnz[j]}.
\par \noindent {\it Error checking:}
If {\tt frontmtx}, {\tt mtxA}, {\tt prowsIVL} or {\tt pfirstnz} 
is {\tt NULL},
or if {\tt msglvl > 0} and {\tt msgFile} is {\tt NULL},
an error message is printed and the program exits.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
void FrontMtx_QR_factorVisit ( FrontMtx *frontmtx, int J, InpMtx *mtxA, 
     IVL *rowsIVL, int firstnz[], ChvList *updList, ChvManager *chvmanager,
     char status[], int colmap[], DV *workDV, double cpus[], 
     double *pfacops, int msglvl, FILE *msgFile ) ;
\end{verbatim}
\index{FrontMtx_QR_factorVisit@{\tt FrontMtx\_QR\_factorVisit()}}
This method visits front {\tt J} during the $QR$ factorization.
The number of operations to reduce the staircase matrix to upper
trapezoidal or triangular form is incremented in {\tt *pfacops}.
\par \noindent {\it Error checking:}
If {\tt frontmtx}, {\tt mtxA}, {\tt rowsIVL}, {\tt firstnz},
{\tt updlist}, {\tt chvmanager}, {\tt status}, {\tt colmap},
{\tt workDV}, {\tt cpus} or {\tt pfacops} is {\tt NULL},
or if {\tt msglvl > 0} and {\tt msgFile} is {\tt NULL},
an error message is printed and the program exits.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
A2 * FrontMtx_QR_assembleFront ( FrontMtx *frontmtx, int J, InpMtx *mtxA, 
             IVL *rowsIVL, int firstnz[], int colmap[], Chv *firstchild,
             DV *workDV, int msglvl, FILE *msgFile ) ;
\end{verbatim}
\index{FrontMtx_QR_assembleFront@{\tt FrontMtx\_QR\_assembleFront()}}
This method creates an {\tt A2} object to hold the front,
assembles any original rows of $A$ and any update
matrices from the children into the front,
and then returns the front.
The rows and update matrices are assembled into staircase form,
so no subsequent permutations of the rows is necessary.
\par \noindent {\it Error checking:}
If {\tt frontmtx}, {\tt mtxA}, {\tt rowsIVL}, {\tt firstnz},
{\tt colmap} or {\tt workDV} is {\tt NULL},
or if {\tt msglvl > 0} and {\tt msgFile} is {\tt NULL},
an error message is printed and the program exits.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
void FrontMtx_QR_storeFront ( FrontMtx *frontmtx, int J, A2 *frontJ,
                              int msglvl, FILE *msgFile ) ;
\end{verbatim}
\index{FrontMtx_QR_storeFront@{\tt FrontMtx\_QR\_storeFront()}}
This method takes as input {\tt frontJ}, the front in trapezoidal
or triangular form.
It scales the strict upper triangle or trapezoid by the diagonal
entries, then squares the diagonal entries.
(This transforms $R^TR$ into $(U^T + I)D(I+U)$
or $R^HR$ into $(U^H + I)D(I+U)$ for our solves.)
It then stores the entries into the factor matrix.
\par \noindent {\it Error checking:}
If {\tt frontmtx} or {\tt frontJ} is {\tt NULL},
or if {\tt msglvl > 0} and {\tt msgFile} is {\tt NULL},
an error message is printed and the program exits.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
Chv * FrontMtx_QR_storeUpdate ( FrontMtx *frontmtx, int J, A2 *frontJ,
                                ChvManager *chvmanager, int msglvl, FILE *msgFile ) ;
\end{verbatim}
\index{FrontMtx_QR_storeUpdate@{\tt FrontMtx\_QR\_storeUpdate()}}
This method takes as input {\tt frontJ}, the front in trapezoidal
or triangular form.
It extracts the update matrix, stores the entries in a {\tt Chv} object,
and returns the {\tt Chv} object.
entries, then squares the diagonal entries.
\par \noindent {\it Error checking:}
If {\tt frontmtx}, {\tt frontJ} or {\tt chvmanager} is {\tt NULL},
or if {\tt msglvl > 0} and {\tt msgFile} is {\tt NULL},
an error message is printed and the program exits.
%-----------------------------------------------------------------------
\end{enumerate}
\par
\subsection{Serial $QR$ Factorization method}
\label{subsection:FrontMtx:proto:factorQR}
\par
%=======================================================================
\begin{enumerate}
%-----------------------------------------------------------------------
\item
\begin{verbatim}
void FrontMtx_QR_factor ( FrontMtx *frontmtx, InpMtx *mtxA, 
                          ChvManager *chvmanager, double cpus[], 
                          double *pfacops,  int msglvl, FILE *msgFile ) ;
\end{verbatim}
\index{FrontMtx_QR_factor@{\tt FrontMtx\_QR\_factor()}}
This method computes the
$(U^T+I)D(I+U)$ factorization of $A^TA$ if $A$ is real
or
$(U^H+I)D(I+U)$ factorization of $A^HA$ if $A$ is complex.
The {\tt chvmanager} object manages the working storage.
On return, the {\tt cpus[]} vector is filled as follows.
\begin{itemize}
\item 
{\tt cpus[0]} -- setup time, time to compute the {\tt rowsIVL} 
and {\tt firstnz[]} objects
\item 
{\tt cpus[1]} -- time to initialize and load the staircase matrices
\item 
{\tt cpus[2]} -- time to factor the matrices
\item 
{\tt cpus[3]} -- time to scale and store the factor entries
\item 
{\tt cpus[4]} -- time to store the update entries
\item 
{\tt cpus[5]} -- miscellaneous time
\item 
{\tt cpus[6]} -- total time
\end{itemize}
On return, {\tt *pfacops} contains the number of floating point
operations done by the factorization.
\par \noindent {\it Error checking:}
If {\tt frontmtx}, {\tt frontJ} or {\tt chvmanager} is {\tt NULL},
or if {\tt msglvl > 0} and {\tt msgFile} is {\tt NULL},
an error message is printed and the program exits.
%-----------------------------------------------------------------------
\end{enumerate}
\par
\subsection{Postprocessing methods}
\label{subsection:FrontMtx:proto:postprocess}
\par
%=======================================================================
\begin{enumerate}
%-----------------------------------------------------------------------
\item
\begin{verbatim}
void FrontMtx_postProcess ( FrontMtx *frontmtx, int msglvl, FILE *msgFile ) ;
\end{verbatim}
\index{FrontMtx_postProcess@{\tt FrontMtx\_postProcess()}}
This method does post-processing chores after the factorization is
complete.
If pivoting was enabled, the method
permutes the row and column adjacency objects,
permutes the lower and upper matrices,
and updates the block adjacency objects.
The chevron submatrices $L_{\bnd{J},J}$ and $U_{J,\bnd{J}}$
are split into $L_{K,J}$ and $U_{J,K}$ 
where $K \cap \bnd{J} \ne \emptyset$.
\par \noindent {\it Error checking:}
If {\tt frontmtx} is {\tt NULL},
or if {\tt msglvl} > 0 and {\tt msgFile} is {\tt NULL}, 
an error message is printed and the program exits.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
void FrontMtx_permuteUpperAdj ( FrontMtx *frontmtx, 
                                int msglvl, FILE *msgFile ) ;
void FrontMtx_permuteLowerAdj ( FrontMtx *frontmtx, 
                                int msglvl, FILE *msgFile ) ;
\end{verbatim}
\index{FrontMtx_permuteUpperAdj@{\tt FrontMtx\_permuteUpperAdj()}}
\index{FrontMtx_permuteLowerAdj@{\tt FrontMtx\_permuteLowerAdj()}}
These methods are called during the postprocessing step, 
where they permute the upper and lower adjacency structures so that
vertices in $\bnd{J}$ are in ascending order with respect to the
indices in $K \cup \bnd{K}$, where $K$ is the parent of $J$.
\par \noindent {\it Error checking:}
If {\tt frontmtx} is {\tt NULL},
or if {\tt msglvl} > 0 and {\tt msgFile} is {\tt NULL}, 
an error message is printed and the program exits.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
void FrontMtx_permuteUpperMatrices ( FrontMtx *frontmtx, 
                                     int msglvl, FILE *msgFile ) ;
void FrontMtx_permuteLowerMatrices ( FrontMtx *frontmtx, 
                                     int msglvl, FILE *msgFile ) ;
\end{verbatim}
\index{FrontMtx_permuteUpperMatrices@{\tt FrontMtx\_permuteUpperMatrices()}}
\index{FrontMtx_permuteLowerMatrices@{\tt FrontMtx\_permuteLowerMatrices()}}
These methods are called during the postprocessing step, 
where they permute the upper $U_{J,\bnd{J}}$ and lower $L_{\bnd{J},J}$
submatrices so that
the columns in $U_{J,\bnd{J}}$ and rows in $L_{\bnd{J},J}$
are in ascending order with the columns and rows of the final
matrix.
\par \noindent {\it Error checking:}
If {\tt frontmtx} is {\tt NULL},
or if {\tt msglvl} > 0 and {\tt msgFile} is {\tt NULL}, 
an error message is printed and the program exits.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
void FrontMtx_splitUpperMatrices ( FrontMtx *frontmtx, int msglvl, FILE *msgFile ) ;
void FrontMtx_splitLowerMatrices ( FrontMtx *frontmtx, int msglvl, FILE *msgFile ) ;
\end{verbatim}
\index{FrontMtx_splitUpperMatrices@{\tt FrontMtx\_splitUpperMatrices()}}
\index{FrontMtx_splitLowerMatrices@{\tt FrontMtx\_splitLowerMatrices()}}
These methods are called during the postprocessing step, 
where they split the chevron submatrices $L_{\bnd{J},J}$ 
and $U_{J,\bnd{J}}$ into $L_{K,J}$ and $U_{J,K}$ 
where $K \cap \bnd{J} \ne \emptyset$.
\par \noindent {\it Error checking:}
If {\tt frontmtx} is {\tt NULL},
or if {\tt msglvl} > 0 and {\tt msgFile} is {\tt NULL}, 
an error message is printed and the program exits.
%-----------------------------------------------------------------------
\end{enumerate}
\par
\subsection{Utility Solve methods}
\label{subsection:FrontMtx:proto:utility-solve}
\par
The following methods are called by all the solve methods
--- serial, multithreaded and MPI.
\par
%=======================================================================
\begin{enumerate}
%-----------------------------------------------------------------------
\item
\begin{verbatim}
SubMtx ** FrontMtx_loadRightHandSide ( FrontMtx *frontmtx, DenseMtx *mtxB, 
                      int owners[], int myid, SubMtxManager *mtxmanager,
                      int msglvl, FILE *msgFile ) ;
\end{verbatim}
\index{FrontMtx_loadRightHandSide@{\tt FrontMtx\_loadRightHandSide()}}
This method creates and returns a vector of pointers to {\tt
SubMtx} objects that hold pointers to the right hand side
submatrices owned by the thread or processor.
\par \noindent {\it Error checking:}
None presently.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
void FrontMtx_forwardVisit ( FrontMtx *frontmtx, int J, int nrhs, 
   int *owners, int myid, SubMtxManager *mtxmanager, SubMtxList *aggList,
   SubMtx *p_mtx[], char frontIsDone[], IP *heads[], SubMtx *p_agg[],
   char status[], int msglvl, FILE *msgFile) ;
\end{verbatim}
\index{FrontMtx_forwardVisit@{\tt FrontMtx\_forwardVisit()}}
This method is used to visit front {\tt J} during the forward solve,
$(U^T + I)Y = B$, $(U^H + I)Y = B$ or $(L + I)Y = B$.
\par \noindent {\it Error checking:}
None presently.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
void FrontMtx_diagonalVisit ( FrontMtx *frontmtx, int J, int owners[],
   int myid, SubMtx *p_mtx[], char frontIsDone[], SubMtx *p_agg[],
   int msglvl, FILE *msgFile ) ;
\end{verbatim}
\index{FrontMtx_diagonalVisit@{\tt FrontMtx\_diagonalVisit()}}
This method is used to visit front {\tt J} during the diagonal solve,
$DZ = Y$.
\par \noindent {\it Error checking:}
None presently.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
void FrontMtx_backwardVisit ( FrontMtx *frontmtx, int J, int nrhs,
   int *owners, int myid, SubMtxManager *mtxmanager, SubMtxList *aggList,
   SubMtx *p_mtx[], char frontIsDone[], IP *heads[], SubMtx *p_agg[],
   char status[], int msglvl, FILE *msgFile ) ;
\end{verbatim}
\index{FrontMtx_backwardVisit@{\tt FrontMtx\_backwardVisit()}}
This method is used to visit front {\tt J} during the backward solve,
$(U + I)Y = B$.
\par \noindent {\it Error checking:}
None presently.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
void FrontMtx_storeSolution ( FrontMtx *frontmtx, int owners[], int myid, 
                              SubMtxManager *mtxmanager, SubMtx *p_mtx[],
                              DenseMtx *mtxX, int msglvl, FILE *msgFile ) ;
\end{verbatim}
\index{FrontMtx_storeSolution@{\tt FrontMtx\_storeSolution()}}
This method stores the solution in the {\tt solmtx} dense matrix object.
\par \noindent {\it Error checking:}
None presently.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
IP ** FrontMtx_forwardSetup ( FrontMtx *frontmtx, int msglvl, FILE *msgFile ) ;
\end{verbatim}
\index{FrontMtx_forwardSetup@{\tt FrontMtx\_forwardSetup()}}
This method is used to set up a data structure of {\tt IP} objects
that hold the updates of the form
$Y_J := Y_J - U_{I,J}^T X_I$,
$Y_J := Y_J - U_{I,J}^H X_I$ or
$Y_J := Y_J - L_{J,I} X_I$
that will be performed by this thread or processor.
\par \noindent {\it Error checking:}
None presently.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
IP ** FrontMtx_backwardSetup ( FrontMtx *frontmtx, int msglvl, FILE *msgFile ) ;
\end{verbatim}
\index{FrontMtx_backwardSetup@{\tt FrontMtx\_backwardSetup()}}
This method is used to set up a data structure of {\tt IP} objects
that hold the updates of the form
$Z_J := Z_J - U_{J,K} X_K$
that will be performed by this thread or processor.
\par \noindent {\it Error checking:}
None presently.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
void FrontMtx_loadActiveRoots ( FrontMtx *frontmtx, char status[],
                                char activeFlag, Ideq *dequeue ) ;
\end{verbatim}
\index{FrontMtx_loadActiveRoots@{\tt FrontMtx\_loadActiveRoots()}}
This method loads the active roots for a thread or a processor into
the dequeue for the backward solve.
\par \noindent {\it Error checking:}
None presently.
%-----------------------------------------------------------------------
\end{enumerate}
\par
\subsection{Serial Solve method}
\label{subsection:FrontMtx:proto:solve-serial}
\par
\begin{enumerate}
%=======================================================================
\item
\begin{verbatim}
void FrontMtx_solve ( FrontMtx *frontmtx, DenseMtx *mtxX, DenseMtx *mtxB, 
         SubMtxManager *mtxmanager, double cpus[], int msglvl, FILE *msgFile ) ;
\end{verbatim}
\index{FrontMtx_solve@{\tt FrontMtx\_solve()}}
This method is used to solve one of three linear systems of equations
---
$(U^T + I)D(I + U) X = B$,
$(U^H + I)D(I + U) X = B$ or
$(L + I)D(I + U) X = B$.
Entries of $B$ are {\it read} from {\tt mtxB} and 
entries of $X$ are written to {\tt mtxX}.
Therefore, {\tt mtxX} and {\tt mtxB} can be the same object.
(Note, this does not hold true for an MPI factorization with pivoting.)
The {\tt mtxmanager} object manages the working storage using the solve.
On return the {\tt cpus[]} vector is filled with the following.
\begin{itemize}
\item
{\tt cpus[0]} --- set up the solves
\item
{\tt cpus[1]} --- fetch right hand side and store solution
\item
{\tt cpus[2]} --- forward solve
\item
{\tt cpus[3]} --- diagonal solve
\item
{\tt cpus[4]} --- backward solve
\item
{\tt cpus[5]} --- total time in the method.
\end{itemize}
\par \noindent {\it Error checking:}
If {\tt frontmtx}, {\tt mtxB} or {\tt cpus} 
is {\tt NULL},
or if {\tt msglvl} > 0 and {\tt msgFile} is {\tt NULL},
an error message is printed and the program exits.
%=======================================================================
\end{enumerate}
\par
\subsection{Serial $QR$ Solve method}
\label{subsection:FrontMtx:proto:QRsolve-serial}
\par
\begin{enumerate}
%=======================================================================
\item
\begin{verbatim}
void FrontMtx_QR_solve ( FrontMtx *frontmtx, InpMtx *mtxA, DenseMtx *mtxX, 
                         DenseMtx *mtxB, SubMtxManager *mtxmanager,
                         double cpus[], int msglvl, FILE *msgFile ) ;
\end{verbatim}
\index{FrontMtx_QR_solve@{\tt FrontMtx\_QR\_solve()}}
This method is used to minimize $\|B - AX\|_F$, where
$A$ is stored in {\tt mtxA},
$B$ is stored in {\tt mtxB},
and $X$ will be stored in {\tt mtxX}.
The {\tt frontmtx} object contains a
$(U^T+I)D(I+U)$ factorization of $A^TA$ if $A$ is real
or
$(U^H+I)D(I+U)$ factorization of $A^HA$ if $A$ is complex.
We solve the seminormal equations
$(U^T+I)D(I+U)X = A^TB$ or $(U^H+I)D(I+U)X = A^HB$
for $X$.
The {\tt mtxmanager} object manages the working storage 
used in the solves.
On return the {\tt cpus[]} vector is filled with the following.
\begin{itemize}
\item
{\tt cpus[0]} --- set up the solves
\item
{\tt cpus[1]} --- fetch right hand side and store solution
\item
{\tt cpus[2]} --- forward solve
\item
{\tt cpus[3]} --- diagonal solve
\item
{\tt cpus[4]} --- backward solve
\item
{\tt cpus[5]} --- total time in the solve method.
\item
{\tt cpus[6]} --- time to compute $A^TB$ or $A^HB$.
\item
{\tt cpus[7]} --- total time.
\end{itemize}
\par \noindent {\it Error checking:}
If {\tt frontmtx}, {\tt mtxA}, {\tt mtxX}, {\tt mtxB} or {\tt cpus} 
is {\tt NULL},
or if {\tt msglvl} > 0 and {\tt msgFile} is {\tt NULL},
an error message is printed and the program exits.
%=======================================================================
\end{enumerate}
\par
\subsection{Utility methods}
\label{subsection:FrontMtx:proto:utility}
\par
%=======================================================================
\begin{enumerate}
%-----------------------------------------------------------------------
\item
\begin{verbatim}
IV * FrontMtx_colmapIV ( FrontMtx *frontmtx ) ;
IV * FrontMtx_rowmapIV ( FrontMtx *frontmtx ) ;
\end{verbatim}
\index{FrontMtx_colmapIV@{\tt FrontMtx\_colmapIV()}}
\index{FrontMtx_rowmapIV@{\tt FrontMtx\_rowmapIV()}}
These methods construct and return an {\tt IV} object that map the
rows and columns to the fronts that contains them.
\par \noindent {\it Error checking:}
None presently.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
IV * FrontMtx_ownedRowsIV ( FrontMtx *frontmtx, int myid, IV *ownersIV,
                            int msglvl, FILE *msgFile ) ;
IV * FrontMtx_ownedColumnsIV ( FrontMtx *frontmtx, int myid, IV *ownersIV,
                            int msglvl, FILE *msgFile ) ;
\end{verbatim}
\index{FrontMtx_ownedColumns@{\tt FrontMtx\_ownedColumns()}}
\index{FrontMtx_ownedRows@{\tt FrontMtx\_ownedRows()}}
These methods construct and return {\tt IV} objects that 
contain the ids of the rows and columns that belong to fronts that
are owned by processor {\tt myid}.
If {\tt ownersIV} is {\tt NULL}, an {\tt IV} object is returned
that contains {\tt \{0,1,2,3, ..., nfront-1\}}.
\par \noindent {\it Error checking:}
If {\tt frontmtx} is {\tt NULL}, 
an error message is printed and the program exits.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
IVL * FrontMtx_makeUpperBlockIVL ( FrontMtx *frontmtx, IV *colmapIV ) ;
IVL * FrontMtx_makeLowerBlockIVL ( FrontMtx *frontmtx, IV *rowmapIV ) ;
\end{verbatim}
\index{FrontMtx_makeUpperBlockIVL@{\tt FrontMtx\_makeUpperBlockIVL()}}
\index{FrontMtx_makeLowerBlockIVL@{\tt FrontMtx\_makeLowerBlockIVL()}}
These methods construct and return {\tt IVL} objects that 
contain the submatrix structure of the lower and upper factors.
The {\tt IV} objects map the rows and columns of the matrix to the
fronts in the factor matrix that contain them.
\par \noindent {\it Error checking:}
If {\tt frontmtx}, {\tt colmapIV} or {\tt rowmapIV} are {\tt NULL}, 
an error message is printed and the program exits.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
void FrontMtx_inertia ( FrontMtx *frontmtx, int *pnneg, int *pnzero, int *pnpos ) ;
\end{verbatim}
\index{FrontMtx_inertia@{\tt FrontMtx\_inertia()}}
This method determines the inertia of a symmetric matrix
based on the $(U^T + I)D(I + U)$ factorization.
The number of negative eigenvalues is returned in {\tt *pnneg},
the number of zero eigenvalues is returned in {\tt *pnzero},
and the number of positive eigenvalues is returned in {\tt *pnpos}.
\par \noindent {\it Error checking:}
If {\tt frontmtx}, {\tt pnneg}, {\tt pnzero} 
or {\tt pnpos} is {\tt NULL}, 
or if ${\tt symmetryflag} \ne 0$
an error message is printed and the program exits.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
int FrontMtx_nSolveOps ( FrontMtx *frontmtx ) ;
\end{verbatim}
\index{FrontMtx_nSolveOps@{\tt FrontMtx\_nSolveOps()}}
This method computes and return the number of floating point
operations for a solve with a single right hand side.
\par \noindent {\it Error checking:}
If {\tt frontmtx} is {\tt NULL}, 
or if {\tt type} or {\tt symmetryflag} are invalid,
an error message is printed and the program exits.
%-----------------------------------------------------------------------
\end{enumerate}
\par
\subsection{IO methods}
\label{subsection:FrontMtx:proto:IO}
\par
%=======================================================================
\begin{enumerate}
%-----------------------------------------------------------------------
\item
\begin{verbatim}
int FrontMtx_readFromFile ( FrontMtx *frontmtx, char *fn ) ;
\end{verbatim}
\index{FrontMtx_readFromFile@{\tt FrontMtx\_readFromFile()}}
\par
This method reads a {\tt FrontMtx object} from a file.
It tries to open the file and if it is successful, 
it then calls {\tt FrontMtx\_readFromFormattedFile()} or
{\tt FrontMtx\_readFromBinaryFile()}, 
closes the file
and returns the value returned from the called routine.
\par \noindent {\it Error checking:}
If {\tt frontmtx} or {\tt fn} are {\tt NULL}, 
or if {\tt fn} is not of the form
{\tt *.frontmtxf} (for a formatted file) 
or {\tt *.frontmtxb} (for a binary file),
an error message is printed and the method returns zero.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
int FrontMtx_readFromFormattedFile ( FrontMtx *frontmtx, FILE *fp ) ;
\end{verbatim}
\index{FrontMtx_readFromFormattedFile@{\tt FrontMtx\_readFromFormattedFile()}}
\par
This method reads a {\tt FrontMtx} object from a formatted file.
If there are no errors in reading the data, 
the value {\tt 1} is returned.
If an IO error is encountered from {\tt fscanf}, zero is returned.
\par \noindent {\it Error checking:}
If {\tt frontmtx} or {\tt fp} are {\tt NULL} 
an error message is printed and zero is returned.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
int FrontMtx_readFromBinaryFile ( FrontMtx *frontmtx, FILE *fp ) ;
\end{verbatim}
\index{FrontMtx_readFromBinaryFile@{\tt FrontMtx\_readFromBinaryFile()}}
This method reads a {\tt FrontMtx} object from a binary file.
If there are no errors in reading the data,
the value {\tt 1} is returned.
If an IO error is encountered from {\tt fread}, zero is returned.
\par \noindent {\it Error checking:}
If {\tt frontmtx} or {\tt fp} are {\tt NULL} an error message
is printed and zero is returned.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
int FrontMtx_writeToFile ( FrontMtx *frontmtx, char *fn ) ;
\end{verbatim}
\index{FrontMtx_writeToFile@{\tt FrontMtx\_writeToFile()}}
\par
This method writes a {\tt FrontMtx object} to a file.
It tries to open the file and if it is successful,
it then calls {\tt FrontMtx\_writeFromFormattedFile()} or
{\tt FrontMtx\_writeFromBinaryFile()},
closes the file
and returns the value returned from the called routine.
\par \noindent {\it Error checking:}
If {\tt frontmtx} or {\tt fn} are {\tt NULL},
or if {\tt fn} is not of the form
{\tt *.frontmtxf} (for a formatted file)
or {\tt *.frontmtxb} (for a binary file),
an error message is printed and the method returns zero.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
int FrontMtx_writeToFormattedFile ( FrontMtx *frontmtx, FILE *fp ) ;
\end{verbatim}
\index{FrontMtx_writeToFormattedFile@{\tt FrontMtx\_writeToFormattedFile()}}
\par
This method writes a {\tt FrontMtx} object to a formatted file.
If there are no errors in writing the data,
the value {\tt 1} is returned.
If an IO error is encountered from {\tt fprintf}, zero is returned.
\par \noindent {\it Error checking:}
If {\tt frontmtx} or {\tt fp} are {\tt NULL} an error message
is printed and zero is returned.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
int FrontMtx_writeToBinaryFile ( FrontMtx *frontmtx, FILE *fp ) ;
\end{verbatim}
\index{FrontMtx_writeToBinaryFile@{\tt FrontMtx\_writeToBinaryFile()}}
\par
This method writes a {\tt FrontMtx} object to a binary file.
If there are no errors in writing the data,
the value {\tt 1} is returned.
If an IO error is encountered from {\tt fwrite}, zero is returned.
\par \noindent {\it Error checking:}
If {\tt frontmtx} or {\tt fp} are {\tt NULL} an error message
is printed and zero is returned.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
int FrontMtx_writeForHumanEye ( FrontMtx *frontmtx, FILE *fp ) ;
\end{verbatim}
\index{FrontMtx_writeForHumanEye@{\tt FrontMtx\_writeForHumanEye()}}
\par
This method writes a {\tt FrontMtx} object to a file in a human
readable format.
The method {\tt FrontMtx\_writeStats()} is called to write out the
header and statistics.
The value {\tt 1} is returned.
\par \noindent {\it Error checking:}
If {\tt frontmtx} or {\tt fp} are {\tt NULL} an error message
is printed and zero is returned.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
int FrontMtx_writeStats ( FrontMtx *frontmtx, FILE *fp ) ;
\end{verbatim}
\index{FrontMtx_writeStats@{\tt FrontMtx\_writeStats()}}
\par
The header and statistics are written to a file.
The value {\tt 1} is returned.
\par \noindent {\it Error checking:}
If {\tt frontmtx} or {\tt fp} are {\tt NULL} an error message
is printed and zero is returned.
%-----------------------------------------------------------------------
\item
\begin{verbatim}
int FrontMtx_writeForMatlab ( FrontMtx *frontmtx, char *Lname, char *Dname,
                              char *Uname, FILE *fp ) ;
\end{verbatim}
\index{FrontMtx_writeForMatlab@{\tt FrontMtx\_writeForMatlab()}}
\par
This method writes out the factor matrix entries in a
Matlab-readable form.
{\tt Lname} is a string for the lower triangular matrix,
{\tt Dname} is a string for the diagonal matrix,
and {\tt Uname} is a string for the upper triangular matrix.
\par \noindent {\it Error checking:}
If {\tt frontmtx}, {\tt Lname}, {\tt Dname}, {\tt Uname} 
or {\tt fp} are {\tt NULL},
 an error message is printed and zero is returned.
%-----------------------------------------------------------------------
\end{enumerate}
\par