p?gemv

Developer Reference for Intel® oneAPI Math Kernel Library for Fortran

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ID 766686

Date 12/16/2022

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p?gemv

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

Syntax

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

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

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

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

Include Files

mkl_pblas.h

Description

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

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

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

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

where

alpha and beta are scalars,

sub(A) is a m-by-n submatrix, sub(A) = A(ia:ia+m-1, ja:ja+n-1),

sub(x) and sub(y) are subvectors.

When trans = 'N' or 'n', 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+m-1) if incy = m_y, and Y(iy: iy+m-1, jy) if incy = 1.

When trans = 'T' or 't', or 'C', or 'c', sub(x) denotes X(ix, jx:jx+m-1) if incx = m_x, and X(ix: ix+m-1, jx) if incx = 1,sub(y) denotes Y(iy, jy:jy+n-1) if incy = m_y, and Y(iy: iy+m-1, jy) if incy = 1.

Input Parameters

trans

(global) CHARACTER*1. Specifies the operation:

if trans= 'N' or 'n', then sub(y) := alpha*sub(A)'*sub(x) + beta*sub(y);

if trans= 'T' or 't', then sub(y) := alpha*sub(A)'*sub(x) + beta*sub(y);

if trans= 'C' or 'c', then sub(y) := alpha*conjg(subA)')*sub(x) + beta*sub(y).

m

(global) INTEGER. Specifies the number of rows of the distributed matrix sub(A), m≥0.

n

(global) INTEGER. Specifies the number of columns of the distributed matrix sub(A), n≥0.

alpha

(global)REAL for psgemv

DOUBLE PRECISION for pdgemv

COMPLEX for pcgemv

DOUBLE COMPLEX for pzgemv

Specifies the scalar alpha.

a

(local)REAL for psgemv

DOUBLE PRECISION for pdgemv

COMPLEX for pcgemv

DOUBLE COMPLEX for pzgemv

Array, size (lld_a, LOCq(ja+n-1)). Before entry this array must contain the local pieces of the distributed matrix sub(A).

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 psgemv

DOUBLE PRECISION for pdgemv

COMPLEX for pcgemv

DOUBLE COMPLEX for pzgemv

Array, size (jx-1)*m_x + ix+(n-1)*abs(incx)) when trans = 'N' or 'n', and (jx-1)*m_x + ix+(m-1)*abs(incx)) otherwise.

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 psgemv

DOUBLE PRECISION for pdgemv

COMPLEX for pcgemv

DOUBLE COMPLEX for pzgemv

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

y

(local)REAL for psgemv

DOUBLE PRECISION for pdgemv

COMPLEX for pcgemv

DOUBLE COMPLEX for pzgemv

Array, size (jy-1)*m_y + iy+(m-1)*abs(incy)) when trans = 'N' or 'n', and (jy-1)*m_y + iy+(n-1)*abs(incy)) otherwise.

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).

Parent topic: PBLAS Level 2 Routines

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Developer Reference for Intel® oneAPI Math Kernel Library for Fortran

p?gemv