p?axpy

Computes a distributed vector-scalar product and adds the result to a distributed vector.

Syntax

call psaxpy(n, a, x, ix, jx, descx, incx, y, iy, jy, descy, incy)

call pdaxpy(n, a, x, ix, jx, descx, incx, y, iy, jy, descy, incy)

call pcaxpy(n, a, x, ix, jx, descx, incx, y, iy, jy, descy, incy)

call pzaxpy(n, a, x, ix, jx, descx, incx, y, iy, jy, descy, incy)

Include Files

The C interfaces for this function are specified in the mkl_pblas.h include file.

Description

The p?axpy routines perform the following operation with distributed vectors: sub(y) := sub(y) + a*sub(x)

where:

a is a scalar;

sub(x) and sub(y) are n-element 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

n

(global) INTEGER. The length of distributed vectors, n≥0.

a

(local) REAL for psaxpy

DOUBLE PRECISION for pdaxpy

COMPLEX for pcaxpy

DOUBLE COMPLEX for pzaxpy

Specifies the scalar a.

x

(local) REAL for psaxpy

DOUBLE PRECISION for pdaxpy

COMPLEX for pcaxpy

DOUBLE COMPLEX for pzaxpy

Array, DIMENSION (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 8. 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.

y

(local) REAL for psaxpy

DOUBLE PRECISION for pdaxpy

COMPLEX for pcaxpy

DOUBLE COMPLEX for pzaxpy

Array, DIMENSION (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 8. 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 sub(y) := sub(y) + a*sub(x).