# FreeBSD Manual Pages

PSLAQGE(l) ) PSLAQGE(l)NAMEPSLAQGE - equilibrate a general M-by-N distributed matrix sub( A ) = A(IA:IA+M-1,JA:JA+N-1) using the row and scaling factors in the vectors R and CSYNOPSISSUBROUTINE PSLAQGE( M, N, A, IA, JA, DESCA, R, C, ROWCND, COLCND, AMAX, EQUED ) CHARACTER EQUED INTEGER IA, JA, M, N REAL AMAX, COLCND, ROWCND INTEGER DESCA( * ) REAL A( * ), C( * ), R( * )PURPOSEPSLAQGE equilibrates a general M-by-N distributed matrix sub( A ) = A(IA:IA+M-1,JA:JA+N-1) using the row and scaling factors in the vectors R and C. Notes ===== Each global data object is described by an associated description vec- tor. This vector stores the information required to establish the map- ping 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 as- sume that its process grid has dimension p x q. LOCr( K ) denotes the number of elements of K that a process would re- ceive 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_AARGUMENTSM (global input) INTEGER The number of rows to be operated on i.e the number of rows of the distributed submatrix sub( A ). M >= 0. N (global input) INTEGER The number of columns to be operated on i.e the number of col- umns of the distributed submatrix sub( A ). N >= 0. A (local input/local output) REAL pointer into the local memory to an array of dimension (LLD_A,LOCc(JA+N-1)) con- taining on entry the M-by-N matrix sub( A ). On exit, the equi- librated distributed matrix. See EQUED for the form of the equilibrated distributed submatrix. IA (global input) INTEGER The row index in the global array A indicating the first row of sub( A ). JA (global input) INTEGER The column index in the global array A indicating the first column of sub( A ). DESCA (global and local input) INTEGER array of dimension DLEN_. The array descriptor for the distributed matrix A. R (local input) REAL array, dimension LOCr(M_A) The row scale factors for sub( A ). R is aligned with the dis- tributed matrix A, and replicated across every process column. R is tied to the distributed matrix A. C (local input) REAL array, dimension LOCc(N_A) The column scale factors of sub( A ). C is aligned with the distributed matrix A, and replicated down every process row. C is tied to the distributed matrix A. ROWCND (global input) REAL The global ratio of the smallest R(i) to the largest R(i), IA <= i <= IA+M-1. COLCND (global input) REAL The global ratio of the smallest C(i) to the largest C(i), JA <= j <= JA+N-1. AMAX (global input) REAL Absolute value of largest distributed submatrix entry. EQUED (global output) CHARACTER Specifies the form of equilibration that was done. = 'N': No equilibration = 'R': Row equilibration, i.e., sub( A ) has been pre- multiplied by diag(R(IA:IA+M-1)), = 'C': Column equilibration, i.e., sub( A ) has been post- multiplied by diag(C(JA:JA+N-1)), = 'B': Both row and column equilibration, i.e., sub( A ) has been replaced by diag(R(IA:IA+M-1)) * sub( A ) * diag(C(JA:JA+N-1)).PARAMETERSTHRESH is a threshold value used to decide if row or column scaling should be done based on the ratio of the row or column scaling factors. If ROWCND < THRESH, row scaling is done, and if COLCND < THRESH, column scaling is done. LARGE and SMALL are threshold values used to decide if row scaling should be done based on the absolute size of the largest matrix ele- ment. If AMAX > LARGE or AMAX < SMALL, row scaling is done. ScaLAPACK version 1.7 13 August 2001 PSLAQGE(l)

NAME | SYNOPSIS | PURPOSE | ARGUMENTS | PARAMETERS

Want to link to this manual page? Use this URL:

<https://www.freebsd.org/cgi/man.cgi?query=pslaqge&manpath=FreeBSD+12.1-RELEASE+and+Ports>