dgemv.c

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/* DGEMV.F -- translated by f2c (version 19941215).
   You must link the resulting object file with the libraries:
        -lf2c -lm   (in that order)
*/

#include "f2c.h"
#include "cblasimpexp.h"


/* *********************************************************************** */

/*     File of the DOUBLE PRECISION  Level-2 BLAS. */
/*     =========================================== */

/*     SUBROUTINE DGEMV ( TRANS, M, N, ALPHA, A, LDA, X, INCX, */
/*    $                   BETA, Y, INCY ) */

/*     SUBROUTINE DGBMV ( TRANS, M, N, KL, KU, ALPHA, A, LDA, X, INCX, */
/*    $                   BETA, Y, INCY ) */

/*     SUBROUTINE DSYMV ( UPLO, N, ALPHA, A, LDA, X, INCX, */
/*    $                   BETA, Y, INCY ) */

/*     SUBROUTINE DSBMV ( UPLO, N, K, ALPHA, A, LDA, X, INCX, */
/*    $                   BETA, Y, INCY ) */

/*     SUBROUTINE DSPMV ( UPLO, N, ALPHA, AP, X, INCX, BETA, Y, INCY ) */

/*     SUBROUTINE DTRMV ( UPLO, TRANS, DIAG, N, A, LDA, X, INCX ) */

/*     SUBROUTINE DTBMV ( UPLO, TRANS, DIAG, N, K, A, LDA, X, INCX ) */

/*     SUBROUTINE DTPMV ( UPLO, TRANS, DIAG, N, AP, X, INCX ) */

/*     SUBROUTINE DTRSV ( UPLO, TRANS, DIAG, N, A, LDA, X, INCX ) */

/*     SUBROUTINE DTBSV ( UPLO, TRANS, DIAG, N, K, A, LDA, X, INCX ) */

/*     SUBROUTINE DTPSV ( UPLO, TRANS, DIAG, N, AP, X, INCX ) */

/*     SUBROUTINE DGER  ( M, N, ALPHA, X, INCX, Y, INCY, A, LDA ) */

/*     SUBROUTINE DSYR  ( UPLO, N, ALPHA, X, INCX, A, LDA ) */

/*     SUBROUTINE DSPR  ( UPLO, N, ALPHA, X, INCX, AP ) */

/*     SUBROUTINE DSYR2 ( UPLO, N, ALPHA, X, INCX, Y, INCY, A, LDA ) */

/*     SUBROUTINE DSPR2 ( UPLO, N, ALPHA, X, INCX, Y, INCY, AP ) */

/*     See: */

/*        Dongarra J. J., Du Croz J. J., Hammarling S.  and Hanson R. J.. */
/*        An  extended  set of Fortran  Basic Linear Algebra Subprograms. */

/*        Technical  Memoranda  Nos. 41 (revision 3) and 81,  Mathematics */
/*        and  Computer Science  Division,  Argonne  National Laboratory, */
/*        9700 South Cass Avenue, Argonne, Illinois 60439, US. */

/*        Or */

/*        NAG  Technical Reports TR3/87 and TR4/87,  Numerical Algorithms */
/*        Group  Ltd.,  NAG  Central  Office,  256  Banbury  Road, Oxford */
/*        OX2 7DE, UK,  and  Numerical Algorithms Group Inc.,  1101  31st */
/*        Street,  Suite 100,  Downers Grove,  Illinois 60515-1263,  USA. */

/* *********************************************************************** */

/* Subroutine */ int __IMPEXP__ dgemv_(trans, m, n, alpha, a, lda, x, incx, beta, y, 
        incy, trans_len)
char *trans;
integer *m, *n;
doublereal *alpha, *a;
integer *lda;
doublereal *x;
integer *incx;
doublereal *beta, *y;
integer *incy;
ftnlen trans_len;
{
    /* System generated locals */
    integer a_dim1, a_offset, i__1, i__2;

    /* Local variables */
    static integer info;
    static doublereal temp;
    static integer lenx, leny, i, j;
    extern logical lsame_();
    static integer ix, iy, jx, jy, kx, ky;
    extern /* Subroutine */ int xerbla_();

/*     .. Scalar Arguments .. */
/*     .. Array Arguments .. */
/*     .. */

/*  Purpose */
/*  ======= */

/*  DGEMV  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  - DOUBLE PRECISION. */
/*           On entry, ALPHA specifies the scalar alpha. */
/*           Unchanged on exit. */

/*  A      - DOUBLE PRECISION 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      - DOUBLE PRECISION 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   - DOUBLE PRECISION. */
/*           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      - DOUBLE PRECISION 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 .. */
/*     .. Local Scalars .. */
/*     .. External Functions .. */
/*     .. External Subroutines .. */
/*     .. Intrinsic Functions .. */
/*     .. */
/*     .. Executable Statements .. */

/*     Test the input parameters. */

    /* Parameter adjustments */
    a_dim1 = *lda;
    a_offset = a_dim1 + 1;
    a -= a_offset;
    --x;
    --y;

    /* Function Body */
    info = 0;
    if (! lsame_(trans, "N", 1L, 1L) && ! lsame_(trans, "T", 1L, 1L) && ! 
            lsame_(trans, "C", 1L, 1L)) {
        info = 1;
    } else if (*m < 0) {
        info = 2;
    } else if (*n < 0) {
        info = 3;
    } else if (*lda < max(1,*m)) {
        info = 6;
    } else if (*incx == 0) {
        info = 8;
    } else if (*incy == 0) {
        info = 11;
    }
    if (info != 0) {
        xerbla_("DGEMV ", &info, 6L);
        return 0;
    }

/*     Quick return if possible. */

    if (*m == 0 || *n == 0 || *alpha == 0. && *beta == 1.) {
        return 0;
    }

/*     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", 1L, 1L)) {
        lenx = *n;
        leny = *m;
    } else {
        lenx = *m;
        leny = *n;
    }
    if (*incx > 0) {
        kx = 1;
    } else {
        kx = 1 - (lenx - 1) * *incx;
    }
    if (*incy > 0) {
        ky = 1;
    } else {
        ky = 1 - (leny - 1) * *incy;
    }

/*     Start the operations. In this version the elements of A are */
/*     accessed sequentially with one pass through A. */

/*     First form  y := beta*y. */

    if (*beta != 1.) {
        if (*incy == 1) {
            if (*beta == 0.) {
                i__1 = leny;
                for (i = 1; i <= i__1; ++i) {
                    y[i] = 0.;
/* L10: */
                }
            } else {
                i__1 = leny;
                for (i = 1; i <= i__1; ++i) {
                    y[i] = *beta * y[i];
/* L20: */
                }
            }
        } else {
            iy = ky;
            if (*beta == 0.) {
                i__1 = leny;
                for (i = 1; i <= i__1; ++i) {
                    y[iy] = 0.;
                    iy += *incy;
/* L30: */
                }
            } else {
                i__1 = leny;
                for (i = 1; i <= i__1; ++i) {
                    y[iy] = *beta * y[iy];
                    iy += *incy;
/* L40: */
                }
            }
        }
    }
    if (*alpha == 0.) {
        return 0;
    }
    if (lsame_(trans, "N", 1L, 1L)) {

/*        Form  y := alpha*A*x + y. */

        jx = kx;
        if (*incy == 1) {
            i__1 = *n;
            for (j = 1; j <= i__1; ++j) {
                if (x[jx] != 0.) {
                    temp = *alpha * x[jx];
                    i__2 = *m;
                    for (i = 1; i <= i__2; ++i) {
                        y[i] += temp * a[i + j * a_dim1];
/* L50: */
                    }
                }
                jx += *incx;
/* L60: */
            }
        } else {
            i__1 = *n;
            for (j = 1; j <= i__1; ++j) {
                if (x[jx] != 0.) {
                    temp = *alpha * x[jx];
                    iy = ky;
                    i__2 = *m;
                    for (i = 1; i <= i__2; ++i) {
                        y[iy] += temp * a[i + j * a_dim1];
                        iy += *incy;
/* L70: */
                    }
                }
                jx += *incx;
/* L80: */
            }
        }
    } else {

/*        Form  y := alpha*A'*x + y. */

        jy = ky;
        if (*incx == 1) {
            i__1 = *n;
            for (j = 1; j <= i__1; ++j) {
                temp = 0.;
                i__2 = *m;
                for (i = 1; i <= i__2; ++i) {
                    temp += a[i + j * a_dim1] * x[i];
/* L90: */
                }
                y[jy] += *alpha * temp;
                jy += *incy;
/* L100: */
            }
        } else {
            i__1 = *n;
            for (j = 1; j <= i__1; ++j) {
                temp = 0.;
                ix = kx;
                i__2 = *m;
                for (i = 1; i <= i__2; ++i) {
                    temp += a[i + j * a_dim1] * x[ix];
                    ix += *incx;
/* L110: */
                }
                y[jy] += *alpha * temp;
                jy += *incy;
/* L120: */
            }
        }
    }

    return 0;

/*     End of DGEMV . */

} /* dgemv_ */

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