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/* ---------------------------------------------------------------------
*
* -- ScaLAPACK routine (version 1.0) --
* University of Tennessee, Knoxville, Oak Ridge National Laboratory,
* and University of California, Berkeley.
* November 17, 1996
*
* ---------------------------------------------------------------------
*/
/*
* Include files
*/
#include "pblas.h"
void psamax_( n, amax, indx, X, ix, jx, desc_X, incx )
/*
* .. Scalar Arguments ..
*/
int * incx, * indx, * ix, * jx, * n;
float * amax;
/* ..
* .. Array Arguments ..
*/
int desc_X[];
float X[];
{
/*
* Purpose
* =======
*
* PSAMAX computes the global index of the maximum element in absolute
* value of a distributed vector sub( X ). The global index is returned
* in INDX and the value is returned in AMAX,
*
* where sub( X ) denotes X(IX,JX:JX+N-1) if INCX = M_X,
* X(IX:IX+N-1,JX) if INCX = 1 and INCX <> M_X.
*
* Notes
* =====
*
* Each global data object is described by an associated description
* vector. This vector stores the information required to establish
* the mapping between an object element and its corresponding process
* and memory location.
*
* Let A be a generic term for any 2D block cyclicly distributed array.
* Such a global array has an associated description vector descA.
* In the following comments, the character _ should be read as
* "of the global array".
*
* NOTATION STORED IN EXPLANATION
* --------------- -------------- --------------------------------------
* DT_A (global) descA[ DT_ ] The descriptor type. In this case,
* DT_A = 1.
* CTXT_A (global) descA[ CTXT_ ] The BLACS context handle, indicating
* the BLACS process grid A is distribu-
* ted over. The context itself is glo-
* bal, but the handle (the integer
* value) may vary.
* M_A (global) descA[ M_ ] The number of rows in the global
* array A.
* N_A (global) descA[ N_ ] The number of columns in the global
* array A.
* MB_A (global) descA[ MB_ ] The blocking factor used to distribu-
* te the rows of the array.
* NB_A (global) descA[ NB_ ] The blocking factor used to distribu-
* te the columns of the array.
* RSRC_A (global) descA[ RSRC_ ] The process row over which the first
* row of the array A is distributed.
* CSRC_A (global) descA[ CSRC_ ] The process column over which the
* first column of the array A is
* distributed.
* LLD_A (local) descA[ LLD_ ] The leading dimension of the local
* array. LLD_A >= MAX(1,LOCr(M_A)).
*
* Let K be the number of rows or columns of a distributed matrix,
* and assume that its process grid has dimension p x q.
* LOCr( K ) denotes the number of elements of K that a process
* would receive if K were distributed over the p processes of its
* process column.
* Similarly, LOCc( K ) denotes the number of elements of K that a
* process would receive if K were distributed over the q processes of
* its process row.
* The values of LOCr() and LOCc() may be determined via a call to the
* ScaLAPACK tool function, NUMROC:
* LOCr( M ) = NUMROC( M, MB_A, MYROW, RSRC_A, NPROW ),
* LOCc( N ) = NUMROC( N, NB_A, MYCOL, CSRC_A, NPCOL ).
* An upper bound for these quantities may be computed by:
* LOCr( M ) <= ceil( ceil(M/MB_A)/NPROW )*MB_A
* LOCc( N ) <= ceil( ceil(N/NB_A)/NPCOL )*NB_A
*
* Because vectors may be seen as particular matrices, a distributed
* vector is considered to be a distributed matrix.
*
*
* Arguments
* =========
*
* N (global input) pointer to INTEGER
* The number of components of the distributed vector sub( X ).
* N >= 0.
*
* AMAX (global output) pointer to REAL
* The absolute value of the largest entry of the distributed
* vector sub( X ) only in the scope of sub( X ).
*
* INDX (global output) pointer to INTEGER
* The global index of the maximum element in absolute value of
* the distributed vector sub( X ) only in its scope.
*
* X (local input) REAL array containing the local
* pieces of a distributed matrix of dimension of at least
* ( (JX-1)*M_X + IX + ( N - 1 )*abs( INCX ) )
* This array contains the entries of the distributed vector
* sub( X ).
*
* IX (global input) pointer to INTEGER
* The global row index of the submatrix of the distributed
* matrix X to operate on.
*
* JX (global input) pointer to INTEGER
* The global column index of the submatrix of the distributed
* matrix X to operate on.
*
* DESCX (global and local input) INTEGER array of dimension 8.
* The array descriptor of the distributed matrix X.
*
* INCX (global input) pointer to INTEGER
* The global increment for the elements of X. Only two values
* of INCX are supported in this version, namely 1 and M_X.
*
* =====================================================================
*
* .. Local Scalars ..
*/
char * rbtop, * rctop, * cbtop, * cctop;
int ictxt, iix, info, ixcol, ixrow, jjx, locindex, maxpos,
mone=-1, mycol, myrow, nn, np, nprow, npcol, nq, nz,
one=1, two=2;
float work[2];
/* ..
* .. External Functions ..
*/
void blacs_gridinfo_();
void igebr2d_();
void igebs2d_();
void sgamx2d_();
void pbchkvect();
void pberror_();
char * ptop();
F_VOID_FCT pstreecomb_();
F_VOID_FCT scombamax_();
F_INTG_FCT numroc_();
F_INTG_FCT isamax_();
/* ..
* .. Executable Statements ..
*
* Get grid parameters
*/
ictxt = desc_X[CTXT_];
blacs_gridinfo_( &ictxt, &nprow, &npcol, &myrow, &mycol );
/*
* Test the input parameters
*/
info = 0;
if( nprow == -1 )
info = -(700+CTXT_+1);
else
pbchkvect( *n, 1, *ix, *jx, desc_X, *incx, 7, &iix, &jjx, &ixrow,
&ixcol, nprow, npcol, myrow, mycol, &info );
if( info )
{
pberror_( &ictxt, "PSAMAX", &info );
return;
}
/*
* Quick return if possible.
*/
*indx = 0;
*amax = ZERO;
if( *n == 0 ) return;
/*
* Find the maximum value and its index
*/
if( ( *incx == 1 ) && ( desc_X[M_] == 1 ) && ( *n == 1 ) )
{
if( ( myrow == ixrow ) && ( mycol == ixcol ) )
{
*indx = *jx;
*amax = X[iix-1+(jjx-1)*desc_X[LLD_]];
}
return;
}
if( *incx == desc_X[M_] )
{
if( myrow == ixrow )
{
nz = (*jx-1) % desc_X[NB_];
nn = *n + nz;
nq = numroc_( &nn, &desc_X[NB_], &mycol, &ixcol, &npcol );
if( mycol == ixcol )
nq -= nz;
rbtop = ptop( BROADCAST, ROW, TOPGET );
if( *rbtop == CTOPDEF )
{
if( nq > 0 )
{
locindex = jjx-1 + isamax_( &nq,
&X[iix-1+(jjx-1)*desc_X[LLD_]],
&desc_X[LLD_] );
work[0] = X[iix-1 + (locindex-1)*desc_X[LLD_]];
work[1] = (float) INDXL2G( locindex, desc_X[NB_],
mycol, desc_X[CSRC_], npcol );
}
else
{
work[0] = ZERO;
}
pstreecomb_( &ictxt, C2F_CHAR( ROW ), &two, work, &mone,
&mycol, scombamax_ );
*amax = work[0];
*indx = ( *amax == ZERO ) ? ( *jx ) : ( (int) work[1] );
}
else
{
rctop = ptop( COMBINE, ROW, TOPGET );
if( nq > 0 )
{
locindex = jjx-1 + isamax_( &nq,
&X[iix-1+(jjx-1)*desc_X[LLD_]],
&desc_X[LLD_] );
*amax = X[iix-1 + (locindex-1)*desc_X[LLD_]];
}
else
{
*amax = ZERO;
}
sgamx2d_( &ictxt, C2F_CHAR( ROW ), C2F_CHAR( rctop ), &one,
&one, amax, &one, &np, &maxpos, &one, &mone, &myrow );
if( *amax != ZERO )
{
if( mycol == maxpos )
{
*indx = INDXL2G( locindex, desc_X[NB_], mycol,
desc_X[CSRC_], npcol );
igebs2d_( &ictxt, C2F_CHAR( ROW ), C2F_CHAR( rbtop ), &one,
&one, indx, &one );
}
else
{
igebr2d_( &ictxt, C2F_CHAR( ROW ), C2F_CHAR( rbtop ), &one,
&one, indx, &one, &myrow, &maxpos );
}
}
else
{
*indx = *jx;
}
}
}
}
else
{
if( mycol == ixcol )
{
nz = (*ix-1) % desc_X[MB_];
nn = *n + nz;
np = numroc_( &nn, &desc_X[MB_], &myrow, &ixrow, &nprow );
if( myrow == ixrow )
np -= nz;
cbtop = ptop( BROADCAST, COLUMN, TOPGET );
if( *cbtop == CTOPDEF )
{
if( np > 0 )
{
locindex = iix-1 + isamax_( &np,
&X[iix-1+(jjx-1)*desc_X[LLD_]],
&one );
work[0] = X[locindex-1 + (jjx-1)*desc_X[LLD_]];
work[1] = (float) INDXL2G( locindex, desc_X[MB_],
myrow, desc_X[RSRC_], nprow );
}
else
{
work[0] = ZERO;
}
pstreecomb_( &ictxt, C2F_CHAR( COLUMN ), &two, work, &mone,
&mycol, scombamax_ );
*amax = work[0];
*indx = ( *amax == ZERO ) ? ( *ix ) : ( (int) work[1] );
}
else
{
cctop = ptop( COMBINE, COLUMN, TOPGET );
if( np > 0 )
{
locindex = iix-1 + isamax_( &np,
&X[iix-1+(jjx-1)*desc_X[LLD_]],
&one );
*amax = X[locindex-1 + (jjx-1)*desc_X[LLD_]];
}
else
{
*amax = ZERO;
}
sgamx2d_( &ictxt, C2F_CHAR( COLUMN ), C2F_CHAR( cctop ), &one,
&one, amax, &one, &maxpos, &nq, &one, &mone, &mycol );
if( *amax != ZERO )
{
if( myrow == maxpos )
{
*indx = INDXL2G( locindex, desc_X[MB_], myrow,
desc_X[RSRC_], nprow );
igebs2d_( &ictxt, C2F_CHAR( COLUMN ), C2F_CHAR( cbtop ), &one,
&one, indx, &one );
}
else
{
igebr2d_( &ictxt, C2F_CHAR( COLUMN ), C2F_CHAR( cbtop ), &one,
&one, indx, &one, &maxpos, &mycol );
}
}
else
{
*indx = *ix;
}
}
}
}
}
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