p?symv

Computes a distributed matrix-vector product using a symmetric matrix.

Syntax

Fortran:

call pssymv(uplo, n, alpha, a, ia, ja, desca, x, ix, jx, descx, incx, beta, y, iy, jy, descy, incy)

call pdsymv(uplo, n, alpha, a, ia, ja, desca, x, ix, jx, descx, incx, beta, y, iy, jy, descy, incy)

C:

void pssymv (char *uplo , MKL_INT *n , float *alpha , float *a , MKL_INT *ia , MKL_INT *ja , MKL_INT *desca , float *x , MKL_INT *ix , MKL_INT *jx , MKL_INT *descx , MKL_INT *incx , float *beta , float *y , MKL_INT *iy , MKL_INT *jy , MKL_INT *descy , MKL_INT *incy );

void pdsymv (char *uplo , MKL_INT *n , double *alpha , double *a , MKL_INT *ia , MKL_INT *ja , MKL_INT *desca , double *x , MKL_INT *ix , MKL_INT *jx , MKL_INT *descx , MKL_INT *incx , double *beta , double *y , MKL_INT *iy , MKL_INT *jy , MKL_INT *descy , MKL_INT *incy );

Include Files

  • C: mkl_pblas.h

Description

The p?symv routines perform a distributed matrix-vector operation defined as

sub(y)  := alpha*sub(A)*sub(x) + beta*sub(y),

where:

alpha and beta are scalars,

sub(A) is a n-by-n symmetric distributed matrix, sub(A)=A(ia:ia+n-1, ja:ja+n-1) ,

sub(x) and sub(y) are distributed vectors.

sub(x) denotes X(ix, jx:jx+n-1) if incx = m_x, and X(ix: ix+n-1, jx) if incx = 1,

sub(y) denotes Y(iy, jy:jy+n-1) if incy = m_y, and Y(iy: iy+n-1, jy) if incy = 1.

Input Parameters

uplo

(global) CHARACTER*1. Specifies whether the upper or lower triangular part of the symmetric distributed matrix sub(A) is used:

If uplo = 'U' or 'u', then the upper triangular part of the sub(A) is used.

If uplo = 'L' or 'l', then the low triangular part of the sub(A) is used.

n

(global) INTEGER. Specifies the order of the distributed matrix sub(A), n 0.

alpha

(global)REAL for pssymv

DOUBLE REAL for pdsymv

Specifies the scalar alpha.

a

(local)REAL for pssymv

DOUBLE REAL for pdsymv

Array, size (lld_a, LOCq(ja+n-1)). This array contains the local pieces of the distributed matrix sub(A).

Before entry when uplo = 'U' or 'u', the n-by-n upper triangular part of the distributed matrix sub(A) must contain the upper triangular part of the symmetric distributed matrix and the strictly lower triangular part of sub(A) is not referenced, and when uplo = 'L' or 'l', the n-by-n lower triangular part of the distributed matrix sub(A) must contain the lower triangular part of the symmetric distributed matrix and the strictly upper triangular part of sub(A) is not referenced.

ia, ja

(global) INTEGER. The row and column indices in the distributed matrix A indicating the first row and the first column of the submatrix sub(A), respectively.

desca

(global and local) INTEGER array of dimension 9. The array descriptor of the distributed matrix A.

x

(local)REAL for pssymv

DOUBLE REAL for pdsymv

Array, size at least (jx-1)*m_x + ix+(n-1)*abs(incx)).

This array contains the entries of the distributed vector sub(x).

ix, jx

(global) INTEGER. The row and column indices in the distributed matrix X indicating the first row and the first column of the submatrix sub(x), respectively.

descx

(global and local) INTEGER array of dimension 9. The array descriptor of the distributed matrix X.

incx

(global) INTEGER. Specifies the increment for the elements of sub(x). Only two values are supported, namely 1 and m_x. incx must not be zero.

beta

(global)REAL for pssymv

DOUBLE REAL for pdsymv

Specifies the scalar beta. When beta is set to zero, then sub(y) need not be set on input.

y

(local)REAL for pssymv

DOUBLE REAL for pdsymv

Array, size at least (jy-1)*m_y + iy+(n-1)*abs(incy)).

This array contains the entries of the distributed vector sub(y).

iy, jy

(global) INTEGER. The row and column indices in the distributed matrix Y indicating the first row and the first column of the submatrix sub(y), respectively.

descy

(global and local) INTEGER array of dimension 9. The array descriptor of the distributed matrix Y.

incy

(global) INTEGER. Specifies the increment for the elements of sub(y). Only two values are supported, namely 1 and m_y. incy must not be zero.

Output Parameters

y

Overwritten by the updated distributed vector sub(y).

For more complete information about compiler optimizations, see our Optimization Notice.