SUBROUTINE SGEMV ( TRANS, M, N, ALPHA, A, LDA, X, INCX, $ BETA, Y, INCY ) **************************************************************************** * * * DATA PARALLEL BLAS based on MPL * * * * Version 1.0 1/9-92 , * * For MasPar MP-1 computers * * * * para//ab, University of Bergen, NORWAY * * * * These programs must be called using F90 style array syntax. * * Note that the F77 style calling sequence has been retained * * in this version for compatibility reasons, be aware that * * parameters related to the array dimensions and shape therefore may * * be redundant and without any influence. * * The calling sequence may be changed in a future version. * * Please report any BUGs, ideas for improvement or other * * comments to * * adm@parallab.uib.no * * * * Future versions may then reflect your suggestions. * * The most current version of this software is available * * from netlib@nac.no , send the message `send index from maspar' * * * * REVISIONS: * * * **************************************************************************** implicit none * .. Scalar Arguments .. REAL ALPHA, BETA INTEGER INCX, INCY, LDA, M, N CHARACTER*1 TRANS * .. Array Arguments .. real, array(:,:) :: a real, array(:) :: x, y intent(in) :: a, x intent(inout) :: y * .. * * Purpose * ======= * * SGEMV performs one of the matrix-vector operations * * y := alpha*A*x + beta*y, or y := alpha*A'*x + beta*y, * * where alpha and beta are scalars, x and y are vectors and A is an * m by n matrix. * * Parameters * ========== * * TRANS - CHARACTER*1. * On entry, TRANS specifies the operation to be performed as * follows: * * TRANS = 'N' or 'n' y := alpha*A*x + beta*y. * * TRANS = 'T' or 't' y := alpha*A'*x + beta*y. * * TRANS = 'C' or 'c' y := alpha*A'*x + beta*y. * * Unchanged on exit. * * M - INTEGER. * On entry, M specifies the number of rows of the matrix A. * M must be at least zero. * Unchanged on exit. * * N - INTEGER. * On entry, N specifies the number of columns of the matrix A. * N must be at least zero. * Unchanged on exit. * * ALPHA - REAL. * On entry, ALPHA specifies the scalar alpha. * Unchanged on exit. * * A - REAL array of DIMENSION ( LDA, n ). * Before entry, the leading m by n part of the array A must * contain the matrix of coefficients. * Unchanged on exit. * * LDA - INTEGER. * On entry, LDA specifies the first dimension of A as declared * in the calling (sub) program. LDA must be at least * max( 1, m ). * Unchanged on exit. * * X - REAL array of DIMENSION at least * ( 1 + ( n - 1 )*abs( INCX ) ) when TRANS = 'N' or 'n' * and at least * ( 1 + ( m - 1 )*abs( INCX ) ) otherwise. * Before entry, the incremented array X must contain the * vector x. * Unchanged on exit. * * INCX - INTEGER. * On entry, INCX specifies the increment for the elements of * X. INCX must not be zero. * Unchanged on exit. * * BETA - REAL. * On entry, BETA specifies the scalar beta. When BETA is * supplied as zero then Y need not be set on input. * Unchanged on exit. * * Y - REAL array of DIMENSION at least * ( 1 + ( m - 1 )*abs( INCY ) ) when TRANS = 'N' or 'n' * and at least * ( 1 + ( n - 1 )*abs( INCY ) ) otherwise. * Before entry with BETA non-zero, the incremented array Y * must contain the vector y. On exit, Y is overwritten by the * updated vector y. * * INCY - INTEGER. * On entry, INCY specifies the increment for the elements of * Y. INCY must not be zero. * Unchanged on exit. * * * Level 2 Blas routine. * * -- Written on 22-October-1986. * Jack Dongarra, Argonne National Lab. * Jeremy Du Croz, Nag Central Office. * Sven Hammarling, Nag Central Office. * Richard Hanson, Sandia National Labs. * * * .. Parameters .. REAL ONE , ZERO PARAMETER ( ONE = 1.0E+0, ZERO = 0.0E+0 ) * .. Local Arrays .. real, array(m) :: yloc real, array(n) :: xloc * .. Local Scalars .. REAL TEMP INTEGER INFO, KX, KY, LENX, LENY * .. External Functions .. LOGICAL LSAME EXTERNAL LSAME * .. External Subroutines .. EXTERNAL XERBLA * .. Intrinsic Functions .. INTRINSIC MAX INTRINSIC spread INTRINSIC sum * .. * .. Executable Statements .. * * Test the input parameters. * INFO = 0 IF ( .NOT.LSAME( TRANS, 'N' ).AND. $ .NOT.LSAME( TRANS, 'T' ).AND. $ .NOT.LSAME( TRANS, 'C' ) )THEN INFO = 1 ELSE IF( M.LT.0 )THEN INFO = 2 ELSE IF( N.LT.0 )THEN INFO = 3 ELSE IF( LDA.LT.MAX( 1, M ) )THEN INFO = 6 ELSE IF( INCX.EQ.0 )THEN INFO = 8 ELSE IF( INCY.EQ.0 )THEN INFO = 11 END IF IF( INFO.NE.0 )THEN CALL XERBLA( 'SGEMV ', INFO ) RETURN END IF * * Quick return if possible. * IF( ( M.EQ.0 ).OR.( N.EQ.0 ).OR. $ ( ( ALPHA.EQ.ZERO ).AND.( BETA.EQ.ONE ) ) ) return * * Set LENX and LENY, the lengths of the vectors x and y, and set * up the start points in X and Y. * IF( LSAME( TRANS, 'N' ) )THEN LENX = N LENY = M ELSE LENX = M LENY = N END IF IF( INCX.GT.0 )THEN KX = 1 ELSE KX = 1 - ( LENX - 1 )*INCX END IF IF( INCY.GT.0 )THEN KY = 1 ELSE KY = 1 - ( LENY - 1 )*INCY END IF * * Start the operations. * * First form yloc := beta*y(ky : 1+(leny-1)*incy : incy). * IF( LSAME( TRANS, 'N' ) )THEN IF (BETA .NE. ONE) THEN IF( INCY.EQ.1 )THEN IF( BETA.EQ.ZERO )THEN YLOC = ZERO ELSE YLOC = BETA * Y(1:LENY) END IF ELSE IF( BETA.EQ.ZERO )THEN YLOC = ZERO ELSE YLOC = BETA * Y(KY : KY+INCY*(LENY-1) : INCY) END IF END IF ELSE IF( INCY.EQ.1 )THEN YLOC = Y(1:LENY) ELSE YLOC = Y(KY : KY+INCY*(LENY-1) : INCY) END IF ENDIF * IF( INCX.EQ.1 )THEN XLOC = X(1:LENX) ELSE XLOC = X(KX : KX+INCX*(LENX-1) : INCX) END IF xloc = xloc * alpha ELSE IF (BETA .NE. ONE) THEN IF( INCY.EQ.1 )THEN IF( BETA.EQ.ZERO )THEN XLOC = ZERO ELSE XLOC = BETA * Y(1:LENY) END IF ELSE IF( BETA.EQ.ZERO )THEN XLOC = ZERO ELSE XLOC = BETA * Y(KY : KY+INCY*(LENY-1) : INCY) END IF END IF ELSE IF( INCY.EQ.1 )THEN XLOC = Y(1:LENY) ELSE XLOC = Y(KY : KY+INCY*(LENY-1) : INCY) END IF ENDIF * IF( INCX.EQ.1 )THEN YLOC = X(1:LENX) ELSE YLOC = X(KX : KX+INCX*(LENX-1) : INCX) END IF yloc = yloc * alpha END IF * IF( LSAME( TRANS, 'N' ) )THEN * * Form y := alpha*A*x + y. * yloc = yloc + matmul( a(1:m,1:n), xloc ) if( incy.eq.1 )then y(1:leny) = yloc else y(ky : ky+incy*(leny-1) : incy) = yloc end if ELSE * * Form y := alpha*A'*x + y. * xloc = xloc + matmul( transpose(a(1:m,1:n)), yloc ) if( incy.eq.1 )then y(1:leny) = xloc else y(ky : ky+incy*(leny-1) : incy) = xloc end if END IF * RETURN * * End of SGEMV . * END