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SUBROUTINE PCLACGV( N, X, IX, JX, DESCX, INCX )
*
* -- ScaLAPACK auxiliary routine (version 1.7) --
* University of Tennessee, Knoxville, Oak Ridge National Laboratory,
* and University of California, Berkeley.
* May 1, 1997
*
* .. Scalar Arguments ..
INTEGER INCX, IX, JX, N
* ..
* .. Array Arguments ..
INTEGER DESCX( * )
COMPLEX X( * )
* ..
*
* Purpose
* =======
*
* PCLACGV conjugates a complex vector of length N, sub( X ), where
* sub( X ) denotes X(IX,JX:JX+N-1) if INCX = DESCX( M_ ) and
* X(IX:IX+N-1,JX) if INCX = 1, and
*
* 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
* --------------- -------------- --------------------------------------
* DTYPE_A(global) DESCA( DTYPE_ )The descriptor type. In this case,
* DTYPE_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 distribute
* the rows of the array.
* NB_A (global) DESCA( NB_ ) The blocking factor used to distribute
* 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 viewed as a subclass of matrices, a
* distributed vector is considered to be a distributed matrix.
*
* Arguments
* =========
*
* N (global input) INTEGER
* The length of the distributed vector sub( X ).
*
* X (local input/local output) COMPLEX pointer into the
* local memory to an array of dimension (LLD_X,*).
* On entry the vector to be conjugated
* x( i ) = X(IX+(JX-1)*M_X +(i-1)*INCX ), 1 <= i <= N.
* On exit the conjugated vector.
*
* IX (global input) INTEGER
* The row index in the global array X indicating the first
* row of sub( X ).
*
* JX (global input) INTEGER
* The column index in the global array X indicating the
* first column of sub( X ).
*
* DESCX (global and local input) INTEGER array of dimension DLEN_.
* The array descriptor for the distributed matrix X.
*
* INCX (global input) INTEGER
* The global increment for the elements of X. Only two values
* of INCX are supported in this version, namely 1 and M_X.
* INCX must not be zero.
*
* =====================================================================
*
* .. Parameters ..
INTEGER BLOCK_CYCLIC_2D, CSRC_, CTXT_, DLEN_, DTYPE_,
$ LLD_, MB_, M_, NB_, N_, RSRC_
PARAMETER ( BLOCK_CYCLIC_2D = 1, DLEN_ = 9, DTYPE_ = 1,
$ CTXT_ = 2, M_ = 3, N_ = 4, MB_ = 5, NB_ = 6,
$ RSRC_ = 7, CSRC_ = 8, LLD_ = 9 )
* ..
* .. Local Scalars ..
INTEGER I, ICOFFX, ICTXT, IIX, IOFFX, IROFFX, IXCOL,
$ IXROW, JJX, LDX, MYCOL, MYROW, NP, NPCOL,
$ NPROW, NQ
* ..
* .. External Subroutines ..
EXTERNAL BLACS_GRIDINFO, INFOG2L
* ..
* .. External Functions ..
INTEGER NUMROC
EXTERNAL NUMROC
* ..
* .. Intrinsic Functions ..
INTRINSIC CONJG, MOD
* ..
* .. Executable Statements ..
*
* Get grid parameters.
*
ICTXT = DESCX( CTXT_ )
CALL BLACS_GRIDINFO( ICTXT, NPROW, NPCOL, MYROW, MYCOL )
*
* Figure local indexes
*
CALL INFOG2L( IX, JX, DESCX, NPROW, NPCOL, MYROW, MYCOL,
$ IIX, JJX, IXROW, IXCOL )
*
LDX = DESCX( LLD_ )
IF( INCX.EQ.DESCX( M_ ) ) THEN
*
* sub( X ) is rowwise distributed.
*
IF( MYROW.NE.IXROW )
$ RETURN
ICOFFX = MOD( JX-1, DESCX( NB_ ) )
NQ = NUMROC( N+ICOFFX, DESCX( NB_ ), MYCOL, IXCOL, NPCOL )
IF( MYCOL.EQ.IXCOL )
$ NQ = NQ - ICOFFX
*
IF( NQ.GT.0 ) THEN
IOFFX = IIX+(JJX-1)*LDX
DO 10 I = 1, NQ
X( IOFFX ) = CONJG( X( IOFFX ) )
IOFFX = IOFFX + LDX
10 CONTINUE
END IF
*
ELSE IF( INCX.EQ.1 ) THEN
*
* sub( X ) is columnwise distributed.
*
IF( MYCOL.NE.IXCOL )
$ RETURN
IROFFX = MOD( IX-1, DESCX( MB_ ) )
NP = NUMROC( N+IROFFX, DESCX( MB_ ), MYROW, IXROW, NPROW )
IF( MYROW.EQ.IXROW )
$ NP = NP - IROFFX
*
IF( NP.GT.0 ) THEN
IOFFX = IIX+(JJX-1)*LDX
DO 20 I = IOFFX, IOFFX+NP-1
X( I ) = CONJG( X( I ) )
20 CONTINUE
END IF
*
END IF
*
RETURN
*
* End of PCLACGV
*
END
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