optimized lapack' SVD for noticeably better performance on small matrices
This commit is contained in:
Vadim Pisarevsky
204
3rdparty/lapack/sgemv_custom.c
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204
3rdparty/lapack/sgemv_custom.c
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#include "clapack.h"
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#include <assert.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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/* .. 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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/* Test the input parameters. */
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/* Function Body */
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char trans = lapack_toupper(_trans[0]);
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integer i, j, m = *_m, n = *_n, lda = *_lda, incx = *_incx, incy = *_incy;
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integer leny = trans == 'N' ? m : n, lenx = trans == 'N' ? n : m;
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real alpha = *_alpha, beta = *_beta;
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integer info = 0;
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if (trans != 'N' && trans != 'T' && trans != 'C')
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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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if (info != 0)
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{
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xerbla_("SGEMV ", &info);
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return 0;
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}
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if( incy < 0 )
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y -= incy*(leny - 1);
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if( incx < 0 )
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x -= incx*(lenx - 1);
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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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if( beta != 1.f )
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{
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if( incy == 1 )
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{
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if( beta == 0.f )
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for( i = 0; i < leny; i++ )
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y[i] = 0.f;
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else
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for( i = 0; i < leny; i++ )
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y[i] *= beta;
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}
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else
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{
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if( beta == 0.f )
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for( i = 0; i < leny; i++ )
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y[i*incy] = 0.f;
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else
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for( i = 0; i < leny; i++ )
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y[i*incy] *= beta;
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}
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}
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if( alpha == 0.f )
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;
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else if( trans == 'N' )
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{
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for( i = 0; i < n; i++, a += lda )
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{
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real s = x[i*incx];
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if( s == 0.f )
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continue;
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s *= alpha;
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for( j = 0; j <= m - 4; j += 4 )
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{
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real t0 = y[j] + s*a[j];
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real t1 = y[j+1] + s*a[j+1];
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y[j] = t0; y[j+1] = t1;
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t0 = y[j+2] + s*a[j+2];
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t1 = y[j+3] + s*a[j+3];
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y[j+2] = t0; y[j+3] = t1;
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}
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for( ; j < m; j++ )
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y[j] += s*a[j];
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}
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}
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else
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{
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for( i = 0; i < n; i++, a += lda )
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{
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real s = 0;
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for( j = 0; j <= m - 4; j += 4 )
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s += x[j]*a[j] + x[j+1]*a[j+1] + x[j+2]*a[j+2] + x[j+3]*a[j+3];
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for( ; j < m; j++ )
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s += x[j]*a[j];
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y[i*incy] += alpha*s;
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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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