251 lines
6.8 KiB
C
251 lines
6.8 KiB
C
#include "blaswrap.h"
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#ifdef __cplusplus
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extern "C" {
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#endif
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#include "f2c.h"
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/* Subroutine */ int dgemv_(char *trans, integer *m, integer *n, doublereal *
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alpha, doublereal *a, integer *lda, doublereal *x, integer *incx,
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doublereal *beta, doublereal *y, integer *incy)
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{
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/* System generated locals */
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integer a_dim1, a_offset, i__1, i__2;
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/* Local variables */
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static integer info;
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static doublereal temp;
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static integer lenx, leny, i__, j;
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extern logical lsame_(char *, char *);
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static integer ix, iy, jx, jy, kx, ky;
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extern /* Subroutine */ int xerbla_(char *, integer *);
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#define a_ref(a_1,a_2) a[(a_2)*a_dim1 + a_1]
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/* Purpose
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=======
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DGEMV performs one of the matrix-vector operations
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y := alpha*A*x + beta*y, or y := alpha*A'*x + beta*y,
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where alpha and beta are scalars, x and y are vectors and A is an
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m by n matrix.
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Parameters
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==========
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TRANS - CHARACTER*1.
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On entry, TRANS specifies the operation to be performed as
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follows:
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TRANS = 'N' or 'n' y := alpha*A*x + beta*y.
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TRANS = 'T' or 't' y := alpha*A'*x + beta*y.
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TRANS = 'C' or 'c' y := alpha*A'*x + beta*y.
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Unchanged on exit.
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M - INTEGER.
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On entry, M specifies the number of rows of the matrix A.
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M must be at least zero.
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Unchanged on exit.
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N - INTEGER.
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On entry, N specifies the number of columns of the matrix A.
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N must be at least zero.
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Unchanged on exit.
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ALPHA - DOUBLE PRECISION.
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On entry, ALPHA specifies the scalar alpha.
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Unchanged on exit.
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A - DOUBLE PRECISION array of DIMENSION ( LDA, n ).
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Before entry, the leading m by n part of the array A must
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contain the matrix of coefficients.
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Unchanged on exit.
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LDA - INTEGER.
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On entry, LDA specifies the first dimension of A as declared
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in the calling (sub) program. LDA must be at least
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max( 1, m ).
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Unchanged on exit.
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X - DOUBLE PRECISION array of DIMENSION at least
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( 1 + ( n - 1 )*abs( INCX ) ) when TRANS = 'N' or 'n'
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and at least
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( 1 + ( m - 1 )*abs( INCX ) ) otherwise.
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Before entry, the incremented array X must contain the
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vector x.
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Unchanged on exit.
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INCX - INTEGER.
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On entry, INCX specifies the increment for the elements of
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X. INCX must not be zero.
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Unchanged on exit.
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BETA - DOUBLE PRECISION.
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On entry, BETA specifies the scalar beta. When BETA is
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supplied as zero then Y need not be set on input.
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Unchanged on exit.
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Y - DOUBLE PRECISION array of DIMENSION at least
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( 1 + ( m - 1 )*abs( INCY ) ) when TRANS = 'N' or 'n'
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and at least
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( 1 + ( n - 1 )*abs( INCY ) ) otherwise.
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Before entry with BETA non-zero, the incremented array Y
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must contain the vector y. On exit, Y is overwritten by the
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updated vector y.
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INCY - INTEGER.
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On entry, INCY specifies the increment for the elements of
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Y. INCY must not be zero.
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Unchanged on exit.
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Level 2 Blas routine.
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-- Written on 22-October-1986.
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Jack Dongarra, Argonne National Lab.
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Jeremy Du Croz, Nag Central Office.
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Sven Hammarling, Nag Central Office.
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Richard Hanson, Sandia National Labs.
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Test the input parameters.
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Parameter adjustments */
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a_dim1 = *lda;
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a_offset = 1 + a_dim1 * 1;
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a -= a_offset;
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--x;
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--y;
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/* Function Body */
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info = 0;
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if (! lsame_(trans, "N") && ! lsame_(trans, "T") && ! lsame_(trans, "C")
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) {
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info = 1;
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} else if (*m < 0) {
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info = 2;
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} else if (*n < 0) {
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info = 3;
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} else if (*lda < max(1,*m)) {
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info = 6;
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} else if (*incx == 0) {
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info = 8;
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} else if (*incy == 0) {
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info = 11;
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}
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if (info != 0) {
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xerbla_("DGEMV ", &info);
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return 0;
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}
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/* Quick return if possible. */
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if (*m == 0 || *n == 0 || *alpha == 0. && *beta == 1.) {
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return 0;
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}
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/* Set LENX and LENY, the lengths of the vectors x and y, and set
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up the start points in X and Y. */
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if (lsame_(trans, "N")) {
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lenx = *n;
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leny = *m;
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} else {
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lenx = *m;
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leny = *n;
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}
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if (*incx > 0) {
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kx = 1;
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} else {
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kx = 1 - (lenx - 1) * *incx;
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}
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if (*incy > 0) {
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ky = 1;
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} else {
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ky = 1 - (leny - 1) * *incy;
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}
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/* Start the operations. In this version the elements of A are
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accessed sequentially with one pass through A.
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First form y := beta*y. */
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if (*beta != 1.) {
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if (*incy == 1) {
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if (*beta == 0.) {
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i__1 = leny;
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for (i__ = 1; i__ <= i__1; ++i__) {
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y[i__] = 0.;
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/* L10: */
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}
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} else {
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i__1 = leny;
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for (i__ = 1; i__ <= i__1; ++i__) {
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y[i__] = *beta * y[i__];
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/* L20: */
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}
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}
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} else {
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iy = ky;
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if (*beta == 0.) {
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i__1 = leny;
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for (i__ = 1; i__ <= i__1; ++i__) {
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y[iy] = 0.;
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iy += *incy;
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/* L30: */
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}
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} else {
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i__1 = leny;
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for (i__ = 1; i__ <= i__1; ++i__) {
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y[iy] = *beta * y[iy];
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iy += *incy;
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/* L40: */
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}
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}
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}
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}
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if (*alpha == 0.) {
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return 0;
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}
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if (lsame_(trans, "N")) {
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/* Form y := alpha*A*x + y. */
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jx = kx;
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if (*incy == 1) {
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i__1 = *n;
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for (j = 1; j <= i__1; ++j) {
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if (x[jx] != 0.) {
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temp = *alpha * x[jx];
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i__2 = *m;
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for (i__ = 1; i__ <= i__2; ++i__) {
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y[i__] += temp * a_ref(i__, j);
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/* L50: */
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}
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}
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jx += *incx;
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/* L60: */
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}
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} else {
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i__1 = *n;
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for (j = 1; j <= i__1; ++j) {
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if (x[jx] != 0.) {
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temp = *alpha * x[jx];
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iy = ky;
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i__2 = *m;
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for (i__ = 1; i__ <= i__2; ++i__) {
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y[iy] += temp * a_ref(i__, j);
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iy += *incy;
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/* L70: */
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}
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}
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jx += *incx;
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/* L80: */
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}
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}
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} else {
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/* Form y := alpha*A'*x + y. */
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jy = ky;
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if (*incx == 1) {
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i__1 = *n;
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for (j = 1; j <= i__1; ++j) {
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temp = 0.;
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i__2 = *m;
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for (i__ = 1; i__ <= i__2; ++i__) {
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temp += a_ref(i__, j) * x[i__];
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/* L90: */
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}
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y[jy] += *alpha * temp;
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jy += *incy;
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/* L100: */
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}
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} else {
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i__1 = *n;
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for (j = 1; j <= i__1; ++j) {
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temp = 0.;
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ix = kx;
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i__2 = *m;
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for (i__ = 1; i__ <= i__2; ++i__) {
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temp += a_ref(i__, j) * x[ix];
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ix += *incx;
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/* L110: */
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}
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y[jy] += *alpha * temp;
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jy += *incy;
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/* L120: */
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}
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}
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}
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return 0;
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/* End of DGEMV . */
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} /* dgemv_ */
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#undef a_ref
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#ifdef __cplusplus
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}
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#endif
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