SUBROUTINE PDLASET( UPLO, M, N, ALPHA, BETA, A, IA, JA, DESCA ) * * -- ScaLAPACK auxiliary routine (version 1.7) -- * University of Tennessee, Knoxville, Oak Ridge National Laboratory, * and University of California, Berkeley. * May 1, 1997 * * .. Scalar Arguments .. CHARACTER UPLO INTEGER IA, JA, M, N DOUBLE PRECISION ALPHA, BETA * .. * .. Array Arguments .. INTEGER DESCA( * ) DOUBLE PRECISION A( * ) * .. * * Purpose * ======= * * PDLASET initializes an M-by-N distributed matrix sub( A ) denoting * A(IA:IA+M-1,JA:JA+N-1) to BETA on the diagonal and ALPHA on the * offdiagonals. * * 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 * * Arguments * ========= * * UPLO (global input) CHARACTER * Specifies the part of the distributed matrix sub( A ) to be * set: * = 'U': Upper triangular part is set; the strictly lower * triangular part of sub( A ) is not changed; * = 'L': Lower triangular part is set; the strictly upper * triangular part of sub( A ) is not changed; * Otherwise: All of the matrix sub( A ) is set. * * M (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 * columns of the distributed submatrix sub( A ). N >= 0. * * ALPHA (global input) DOUBLE PRECISION * The constant to which the offdiagonal elements are to be * set. * * BETA (global input) DOUBLE PRECISION * The constant to which the diagonal elements are to be set. * * A (local output) DOUBLE PRECISION pointer into the local memory * to an array of dimension (LLD_A,LOCc(JA+N-1)). This array * contains the local pieces of the distributed matrix sub( A ) * to be set. On exit, the leading M-by-N submatrix sub( A ) * is set as follows: * * if UPLO = 'U', A(IA+i-1,JA+j-1) = ALPHA, 1<=i<=j-1, 1<=j<=N, * if UPLO = 'L', A(IA+i-1,JA+j-1) = ALPHA, j+1<=i<=M, 1<=j<=N, * otherwise, A(IA+i-1,JA+j-1) = ALPHA, 1<=i<=M, 1<=j<=N, * IA+i.NE.JA+j, * and, for all UPLO, A(IA+i-1,JA+i-1) = BETA, 1<=i<=min(M,N). * * 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. * * ===================================================================== * * .. 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, IAA, IBLK, IN, ITMP, J, JAA, JBLK, JN, JTMP * .. * .. External Subroutines .. EXTERNAL PDLASE2 * .. * .. External Functions .. LOGICAL LSAME INTEGER ICEIL EXTERNAL ICEIL, LSAME * .. * .. Intrinsic Functions .. INTRINSIC MIN, MOD * .. * .. Executable Statements .. * IF( M.EQ.0 .OR. N.EQ.0 ) $ RETURN * IF( M.LE.( DESCA( MB_ ) - MOD( IA-1, DESCA( MB_ ) ) ) .OR. $ N.LE.( DESCA( NB_ ) - MOD( JA-1, DESCA( NB_ ) ) ) ) THEN CALL PDLASE2( UPLO, M, N, ALPHA, BETA, A, IA, JA, DESCA ) ELSE * IF( LSAME( UPLO, 'U' ) ) THEN IN = MIN( ICEIL( IA, DESCA( MB_ ) ) * DESCA( MB_ ), IA+M-1 ) CALL PDLASE2( UPLO, IN-IA+1, N, ALPHA, BETA, A, IA, JA, $ DESCA ) DO 10 I = IN+1, IA+M-1, DESCA( MB_ ) ITMP = I-IA IBLK = MIN( DESCA( MB_ ), M-ITMP ) JAA = JA + ITMP CALL PDLASE2( UPLO, IBLK, N-ITMP, ALPHA, BETA, $ A, I, JAA, DESCA ) 10 CONTINUE ELSE IF( LSAME( UPLO, 'L' ) ) THEN JN = MIN( ICEIL( JA, DESCA( NB_ ) ) * DESCA( NB_ ), JA+N-1 ) CALL PDLASE2( UPLO, M, JN-JA+1, ALPHA, BETA, A, IA, JA, $ DESCA ) DO 20 J = JN+1, JA+N-1, DESCA( NB_ ) JTMP = J-JA JBLK = MIN( DESCA( NB_ ), N-JTMP ) IAA = IA + JTMP CALL PDLASE2( UPLO, M-JTMP, JBLK, ALPHA, BETA, A, IAA, $ J, DESCA ) 20 CONTINUE ELSE IF( M.LE.N ) THEN IN = MIN( ICEIL( IA, DESCA( MB_ ) ) * DESCA( MB_ ), $ IA+M-1 ) CALL PDLASE2( UPLO, IN-IA+1, N, ALPHA, BETA, A, IA, $ JA, DESCA ) DO 30 I = IN+1, IA+M-1, DESCA( MB_ ) ITMP = I-IA IBLK = MIN( DESCA( MB_ ), M-ITMP ) CALL PDLASE2( UPLO, IBLK, I-IA, ALPHA, ALPHA, A, I, $ JA, DESCA ) CALL PDLASE2( UPLO, IBLK, N-I+IA, ALPHA, BETA, A, I, $ JA+I-IA, DESCA ) 30 CONTINUE ELSE JN = MIN( ICEIL( JA, DESCA( NB_ ) ) * DESCA( NB_ ), $ JA+N-1 ) CALL PDLASE2( UPLO, M, JN-JA+1, ALPHA, BETA, A, IA, $ JA, DESCA ) DO 40 J = JN+1, JA+N-1, DESCA( NB_ ) JTMP = J-JA JBLK = MIN( DESCA( NB_ ), N-JTMP ) CALL PDLASE2( UPLO, J-JA, JBLK, ALPHA, ALPHA, A, IA, $ J, DESCA ) CALL PDLASE2( UPLO, M-J+JA, JBLK, ALPHA, BETA, A, $ IA+J-JA, J, DESCA ) 40 CONTINUE END IF END IF * END IF * RETURN * * End of PDLASET * END