#include "clapack.h"
/* Subroutine */ int dgemv_(char *_trans, integer *_m, integer *_n, doublereal *
_alpha, doublereal *a, integer *_lda, doublereal *x, integer *_incx,
doublereal *_beta, doublereal *y, integer *_incy)
{
/* .. 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. */
/* Arguments */
/* ========== */
/* 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 .. */
/* .. */
/* Test the input parameters. */
char trans = lapack_toupper(_trans[0]);
integer i, j, m = *_m, n = *_n, lda = *_lda, incx = *_incx, incy = *_incy;
integer leny = trans == 'N' ? m : n, lenx = trans == 'N' ? n : m;
doublereal alpha = *_alpha, beta = *_beta;
integer info = 0;
if (trans != 'N' && trans != 'T' && trans != 'C')
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_("SGEMV ", &info);
return 0;
}
if( incy < 0 )
y -= incy*(leny - 1);
if( incx < 0 )
x -= incx*(lenx - 1);
/* Start the operations. In this version the elements of A are */
/* accessed sequentially with one pass through A. */
if( beta != 1. )
{
if( incy == 1 )
{
if( beta == 0. )
for( i = 0; i < leny; i++ )
y[i] = 0.;
else
for( i = 0; i < leny; i++ )
y[i] *= beta;
}
else
{
if( beta == 0. )
for( i = 0; i < leny; i++ )
y[i*incy] = 0.;
else
for( i = 0; i < leny; i++ )
y[i*incy] *= beta;
}
}
if( alpha == 0. )
;
else if( trans == 'N' )
{
if( incy == 1 )
{
for( i = 0; i < n; i++, a += lda )
{
doublereal s = x[i*incx];
if( s == 0. )
continue;
s *= alpha;
for( j = 0; j <= m - 4; j += 4 )
{
doublereal t0 = y[j] + s*a[j];
doublereal t1 = y[j+1] + s*a[j+1];
y[j] = t0; y[j+1] = t1;
t0 = y[j+2] + s*a[j+2];
t1 = y[j+3] + s*a[j+3];
y[j+2] = t0; y[j+3] = t1;
}
for( ; j < m; j++ )
y[j] += s*a[j];
}
}
else
{
for( i = 0; i < n; i++, a += lda )
{
doublereal s = x[i*incx];
if( s == 0. )
continue;
s *= alpha;
for( j = 0; j < m; j++ )
y[j*incy] += s*a[j];
}
}
}
else
{
if( incx == 1 )
{
for( i = 0; i < n; i++, a += lda )
{
doublereal s = 0;
for( j = 0; j <= m - 4; j += 4 )
s += x[j]*a[j] + x[j+1]*a[j+1] + x[j+2]*a[j+2] + x[j+3]*a[j+3];
for( ; j < m; j++ )
s += x[j]*a[j];
y[i*incy] += alpha*s;
}
}
else
{
for( i = 0; i < n; i++, a += lda )
{
doublereal s = 0;
for( j = 0; j < m; j++ )
s += x[j*incx]*a[j];
y[i*incy] += alpha*s;
}
}
}
return 0;
/* End of DGEMV . */
} /* dgemv_ */