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Open Source Computer Vision Library
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300 lines
7.0 KiB
300 lines
7.0 KiB
15 years ago
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#include "clapack.h"
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/* Subroutine */ int sgemv_(char *trans, integer *m, integer *n, real *alpha,
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real *a, integer *lda, real *x, integer *incx, real *beta, real *y,
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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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integer i__, j, ix, iy, jx, jy, kx, ky, info;
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real temp;
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integer lenx, leny;
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extern logical lsame_(char *, char *);
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extern /* Subroutine */ int xerbla_(char *, integer *);
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/* .. Scalar Arguments .. */
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/* .. */
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/* .. Array Arguments .. */
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/* .. */
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/* Purpose */
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/* ======= */
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/* SGEMV 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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/* Arguments */
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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 - REAL . */
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/* On entry, ALPHA specifies the scalar alpha. */
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/* Unchanged on exit. */
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/* A - REAL 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 - REAL 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 - REAL . */
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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 - REAL 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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/* .. Parameters .. */
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/* .. */
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/* .. Local Scalars .. */
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/* .. */
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/* .. External Functions .. */
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/* .. */
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/* .. External Subroutines .. */
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/* .. */
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/* .. Intrinsic Functions .. */
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/* .. */
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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;
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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_("SGEMV ", &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.f && *beta == 1.f) {
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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.f) {
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if (*incy == 1) {
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if (*beta == 0.f) {
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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.f;
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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.f) {
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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.f;
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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.f) {
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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.f) {
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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[i__ + j * a_dim1];
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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.f) {
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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[i__ + j * a_dim1];
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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.f;
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i__2 = *m;
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for (i__ = 1; i__ <= i__2; ++i__) {
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temp += a[i__ + j * a_dim1] * 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.f;
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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[i__ + j * a_dim1] * 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 SGEMV . */
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} /* sgemv_ */
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