MAGMA  1.2.0
MatrixAlgebraonGPUandMulticoreArchitectures
 All Classes Namespaces Files Functions Variables Typedefs Enumerations Enumerator Macros Groups
Macros | Functions
slatrd.cpp File Reference
#include "common_magma.h"
#include <cblas.h>
Include dependency graph for slatrd.cpp:

Go to the source code of this file.

Macros

#define PRECISION_s
#define A(i, j)   (a+(j)*lda + (i))
#define W(i, j)   (w+(j)*ldw + (i))
#define dA(i, j)   (da+(j)*ldda + (i))
#define dW(i, j)   (dw+(j)*lddw + (i))

Functions

magma_int_t magma_slatrd (char uplo, magma_int_t n, magma_int_t nb, float *a, magma_int_t lda, float *e, float *tau, float *w, magma_int_t ldw, float *da, magma_int_t ldda, float *dw, magma_int_t lddw)

Macro Definition Documentation

#define A (   i,
  j 
)    (a+(j)*lda + (i))

Definition at line 19 of file slatrd.cpp.

#define dA (   i,
  j 
)    (da+(j)*ldda + (i))

Definition at line 22 of file slatrd.cpp.

#define dW (   i,
  j 
)    (dw+(j)*lddw + (i))

Definition at line 23 of file slatrd.cpp.

#define PRECISION_s

Definition at line 17 of file slatrd.cpp.

#define W (   i,
  j 
)    (w+(j)*ldw + (i))

Definition at line 20 of file slatrd.cpp.

Function Documentation

magma_int_t magma_slatrd ( char  uplo,
magma_int_t  n,
magma_int_t  nb,
float *  a,
magma_int_t  lda,
float *  e,
float *  tau,
float *  w,
magma_int_t  ldw,
float *  da,
magma_int_t  ldda,
float *  dw,
magma_int_t  lddw 
)

Definition at line 26 of file slatrd.cpp.

References A, blasf77_saxpy(), blasf77_sdot, blasf77_sgemv(), blasf77_sscal(), dA, dW, lapack_testing::f, lapackf77_lsame, lapackf77_slacgv(), lapackf77_slarfg(), magma_queue_create(), magma_queue_destroy(), magma_queue_sync(), MAGMA_S_NEG_ONE, MAGMA_S_ONE, MAGMA_S_REAL, MAGMA_S_SET2REAL, MAGMA_S_ZERO, magma_sgetmatrix_async(), magma_ssetvector(), magma_ssymv(), MagmaLower, MagmaTransStr, MagmaUpper, min, uplo, and W.

{
/* -- MAGMA (version 1.2.0) --
Univ. of Tennessee, Knoxville
Univ. of California, Berkeley
Univ. of Colorado, Denver
May 2012
Purpose
=======
SLATRD reduces NB rows and columns of a real symmetric matrix A to
symmetric tridiagonal form by an orthogonal similarity
transformation Q' * A * Q, and returns the matrices V and W which are
needed to apply the transformation to the unreduced part of A.
If UPLO = 'U', SLATRD reduces the last NB rows and columns of a
matrix, of which the upper triangle is supplied;
if UPLO = 'L', SLATRD reduces the first NB rows and columns of a
matrix, of which the lower triangle is supplied.
This is an auxiliary routine called by SSYTRD.
Arguments
=========
UPLO (input) CHARACTER*1
Specifies whether the upper or lower triangular part of the
symmetric matrix A is stored:
= 'U': Upper triangular
= 'L': Lower triangular
N (input) INTEGER
The order of the matrix A.
NB (input) INTEGER
The number of rows and columns to be reduced.
A (input/output) REAL array, dimension (LDA,N)
On entry, the symmetric matrix A. If UPLO = 'U', the leading
n-by-n upper triangular part of A contains the upper
triangular part of the matrix A, and the strictly lower
triangular part of A is not referenced. If UPLO = 'L', the
leading n-by-n lower triangular part of A contains the lower
triangular part of the matrix A, and the strictly upper
triangular part of A is not referenced.
On exit:
if UPLO = 'U', the last NB columns have been reduced to
tridiagonal form, with the diagonal elements overwriting
the diagonal elements of A; the elements above the diagonal
with the array TAU, represent the orthogonal matrix Q as a
product of elementary reflectors;
if UPLO = 'L', the first NB columns have been reduced to
tridiagonal form, with the diagonal elements overwriting
the diagonal elements of A; the elements below the diagonal
with the array TAU, represent the orthogonal matrix Q as a
product of elementary reflectors.
See Further Details.
LDA (input) INTEGER
The leading dimension of the array A. LDA >= (1,N).
E (output) REAL array, dimension (N-1)
If UPLO = 'U', E(n-nb:n-1) contains the superdiagonal
elements of the last NB columns of the reduced matrix;
if UPLO = 'L', E(1:nb) contains the subdiagonal elements of
the first NB columns of the reduced matrix.
TAU (output) REAL array, dimension (N-1)
The scalar factors of the elementary reflectors, stored in
TAU(n-nb:n-1) if UPLO = 'U', and in TAU(1:nb) if UPLO = 'L'.
See Further Details.
W (output) REAL array, dimension (LDW,NB)
The n-by-nb matrix W required to update the unreduced part
of A.
LDW (input) INTEGER
The leading dimension of the array W. LDW >= max(1,N).
Further Details
===============
If UPLO = 'U', the matrix Q is represented as a product of elementary
reflectors
Q = H(n) H(n-1) . . . H(n-nb+1).
Each H(i) has the form
H(i) = I - tau * v * v'
where tau is a real scalar, and v is a real vector with
v(i:n) = 0 and v(i-1) = 1; v(1:i-1) is stored on exit in A(1:i-1,i),
and tau in TAU(i-1).
If UPLO = 'L', the matrix Q is represented as a product of elementary
reflectors
Q = H(1) H(2) . . . H(nb).
Each H(i) has the form
H(i) = I - tau * v * v'
where tau is a real scalar, and v is a real vector with
v(1:i) = 0 and v(i+1) = 1; v(i+1:n) is stored on exit in A(i+1:n,i),
and tau in TAU(i).
The elements of the vectors v together form the n-by-nb matrix V
which is needed, with W, to apply the transformation to the unreduced
part of the matrix, using a symmetric rank-2k update of the form:
A := A - V*W' - W*V'.
The contents of A on exit are illustrated by the following examples
with n = 5 and nb = 2:
if UPLO = 'U': if UPLO = 'L':
( a a a v4 v5 ) ( d )
( a a v4 v5 ) ( 1 d )
( a 1 v5 ) ( v1 1 a )
( d 1 ) ( v1 v2 a a )
( d ) ( v1 v2 a a a )
where d denotes a diagonal element of the reduced matrix, a denotes
an element of the original matrix that is unchanged, and vi denotes
an element of the vector defining H(i).
===================================================================== */
char uplo_[2] = {uplo, 0};
static magma_int_t i;
float c_neg_one = MAGMA_S_NEG_ONE;
float c_one = MAGMA_S_ONE;
float c_zero = MAGMA_S_ZERO;
#if defined(PRECISION_z) || defined(PRECISION_c)
float value = MAGMA_S_ZERO;
#endif
static magma_int_t ione = 1;
static magma_int_t i_n, i_1, iw;
static float alpha;
float *f = (float *)malloc(n*sizeof(float ));
if (n <= 0) {
return 0;
}
static cudaStream_t stream;
magma_queue_create( &stream );
if (lapackf77_lsame(uplo_, "U")) {
/* Reduce last NB columns of upper triangle */
for (i = n-1; i >= n - nb ; --i) {
i_1 = i + 1;
i_n = n - i - 1;
iw = i - n + nb;
if (i < n-1) {
/* Update A(1:i,i) */
#if defined(PRECISION_z) || defined(PRECISION_c)
lapackf77_slacgv(&i_n, W(i, iw+1), &ldw);
#endif
blasf77_sgemv("No transpose", &i_1, &i_n, &c_neg_one, A(0, i+1), &lda,
W(i, iw+1), &ldw, &c_one, A(0, i), &ione);
#if defined(PRECISION_z) || defined(PRECISION_c)
lapackf77_slacgv(&i_n, W(i, iw+1), &ldw);
lapackf77_slacgv(&i_n, A(i, i+1), &lda);
#endif
blasf77_sgemv("No transpose", &i_1, &i_n, &c_neg_one, W(0, iw+1), &ldw,
A(i, i+1), &lda, &c_one, A(0, i), &ione);
#if defined(PRECISION_z) || defined(PRECISION_c)
lapackf77_slacgv(&i_n, A(i, i+1), &lda);
#endif
}
if (i > 0) {
/* Generate elementary reflector H(i) to annihilate A(1:i-2,i) */
alpha = *A(i-1, i);
lapackf77_slarfg(&i, &alpha, A(0, i), &ione, &tau[i - 1]);
e[i-1] = MAGMA_S_REAL( alpha );
MAGMA_S_SET2REAL(*A(i-1, i), 1.);
/* Compute W(1:i-1,i) */
// 1. Send the block reflector A(0:n-i-1,i) to the GPU
magma_ssetvector( i, A(0, i), 1, dA(0, i), 1 );
magma_ssymv(MagmaUpper, i, c_one, dA(0, 0), ldda,
dA(0, i), ione, c_zero, dW(0, iw), ione);
// 2. Start putting the result back (asynchronously)
magma_sgetmatrix_async( i, 1,
dW(0, iw), lddw,
W(0, iw) /*test*/, ldw, stream );
if (i < n-1) {
blasf77_sgemv(MagmaTransStr, &i, &i_n, &c_one, W(0, iw+1), &ldw,
A(0, i), &ione, &c_zero, W(i+1, iw), &ione);
}
// 3. Here is where we need it // TODO find the right place
magma_queue_sync( stream );
if (i < n-1) {
blasf77_sgemv("No transpose", &i, &i_n, &c_neg_one, A(0, i+1), &lda,
W(i+1, iw), &ione, &c_one, W(0, iw), &ione);
blasf77_sgemv(MagmaTransStr, &i, &i_n, &c_one, A(0, i+1), &lda,
A(0, i), &ione, &c_zero, W(i+1, iw), &ione);
blasf77_sgemv("No transpose", &i, &i_n, &c_neg_one, W(0, iw+1), &ldw,
W(i+1, iw), &ione, &c_one, W(0, iw), &ione);
}
blasf77_sscal(&i, &tau[i - 1], W(0, iw), &ione);
#if defined(PRECISION_z) || defined(PRECISION_c)
cblas_sdot_sub(i, W(0, iw), ione, A(0, i), ione, &value);
// blasf77_sdot(&value, &i, W(0, iw), &ione, A(0, i), &ione);
alpha = tau[i - 1] * -.5f * value;
#else
alpha = tau[i - 1] * -.5f * blasf77_sdot(&i, W(0, iw), &ione, A(0, i), &ione);
#endif
blasf77_saxpy(&i, &alpha, A(0, i), &ione,
W(0, iw), &ione);
}
}
} else {
/* Reduce first NB columns of lower triangle */
for (i = 0; i < nb; ++i)
{
/* Update A(i:n,i) */
i_n = n - i;
#if defined(PRECISION_z) || defined(PRECISION_c)
lapackf77_slacgv(&i, W(i, 0), &ldw);
#endif
blasf77_sgemv("No transpose", &i_n, &i, &c_neg_one, A(i, 0), &lda,
W(i, 0), &ldw, &c_one, A(i, i), &ione);
#if defined(PRECISION_z) || defined(PRECISION_c)
lapackf77_slacgv(&i, W(i, 0), &ldw);
lapackf77_slacgv(&i, A(i ,0), &lda);
#endif
blasf77_sgemv("No transpose", &i_n, &i, &c_neg_one, W(i, 0), &ldw,
A(i, 0), &lda, &c_one, A(i, i), &ione);
#if defined(PRECISION_z) || defined(PRECISION_c)
lapackf77_slacgv(&i, A(i, 0), &lda);
#endif
if (i < n-1)
{
/* Generate elementary reflector H(i) to annihilate A(i+2:n,i) */
i_n = n - i - 1;
alpha = *A(i+1, i);
lapackf77_slarfg(&i_n, &alpha, A(min(i+2,n-1), i), &ione, &tau[i]);
e[i] = MAGMA_S_REAL( alpha );
MAGMA_S_SET2REAL(*A(i+1, i), 1.);
/* Compute W(i+1:n,i) */
// 1. Send the block reflector A(i+1:n,i) to the GPU
magma_ssetvector( i_n, A(i+1, i), 1, dA(i+1, i), 1 );
magma_ssymv(MagmaLower, i_n, c_one, dA(i+1, i+1), ldda, dA(i+1, i), ione, c_zero,
dW(i+1, i), ione);
// 2. Start putting the result back (asynchronously)
magma_sgetmatrix_async( i_n, 1,
dW(i+1, i), lddw,
W(i+1, i), ldw, stream );
blasf77_sgemv(MagmaTransStr, &i_n, &i, &c_one, W(i+1, 0), &ldw,
A(i+1, i), &ione, &c_zero, W(0, i), &ione);
blasf77_sgemv("No transpose", &i_n, &i, &c_neg_one, A(i+1, 0), &lda,
W(0, i), &ione, &c_zero, f, &ione);
blasf77_sgemv(MagmaTransStr, &i_n, &i, &c_one, A(i+1, 0), &lda,
A(i+1, i), &ione, &c_zero, W(0, i), &ione);
// 3. Here is where we need it
magma_queue_sync( stream );
if (i!=0)
blasf77_saxpy(&i_n, &c_one, f, &ione, W(i+1, i), &ione);
blasf77_sgemv("No transpose", &i_n, &i, &c_neg_one, W(i+1, 0), &ldw,
W(0, i), &ione, &c_one, W(i+1, i), &ione);
blasf77_sscal(&i_n, &tau[i], W(i+1,i), &ione);
#if defined(PRECISION_z) || defined(PRECISION_c)
/* Comment:
To do - move to cblas in cases like this. The commented
out version works with MKL but is not a standard interface
for other BLAS zdoc implementations
*/
cblas_sdot_sub(i_n, W(i +1, i), ione,
A(i +1, i), ione, &value);
//blasf77_sdot(&value, &i_n, W(i+1,i), &ione, A(i+1, i), &ione);
alpha = tau[i]* -.5f * value;
#else
alpha = tau[i]* -.5f* blasf77_sdot(&i_n, W(i+1,i), &ione, A(i+1, i), &ione);
#endif
blasf77_saxpy(&i_n, &alpha, A(i+1, i), &ione, W(i+1,i), &ione);
}
}
}
free(f);
magma_queue_destroy( stream );
return 0;
} /* slatrd_ */

Here is the call graph for this function:

Here is the caller graph for this function: