cblas_?spmv

Developer Reference for Intel® oneAPI Math Kernel Library for C

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ID 766684

Date 3/22/2024

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cblas_?spmv

Computes a matrix-vector product with a symmetric packed matrix.

Syntax

void cblas_sspmv (const CBLAS_LAYOUT Layout, const CBLAS_UPLO uplo, const MKL_INT n, const float alpha, const float *ap, const float *x, const MKL_INT incx, const float beta, float *y, const MKL_INT incy);

void cblas_dspmv (const CBLAS_LAYOUT Layout, const CBLAS_UPLO uplo, const MKL_INT n, const double alpha, const double *ap, const double *x, const MKL_INT incx, const double beta, double *y, const MKL_INT incy);

Include Files

mkl.h

Description

The ?spmv routines perform a matrix-vector operation defined as

y := alpha*A*x + beta*y,

where:

alpha and beta are scalars,

x and y are n-element vectors,

A is an n-by-n symmetric matrix, supplied in packed form.

Input Parameters

Layout

Specifies whether two-dimensional array storage is row-major (CblasRowMajor) or column-major (CblasColMajor).

uplo

Specifies whether the upper or lower triangular part of the matrix A is supplied in the packed array ap.

If uplo = CblasUpper, then the upper triangular part of the matrix A is supplied in the packed array ap .

If uplo = CblasLower, then the low triangular part of the matrix A is supplied in the packed array ap .

n

Specifies the order of the matrix A. The value of n must be at least zero.

alpha

Specifies the scalar alpha.

ap

Array, size at least ((n*(n + 1))/2).

For Layout = CblasColMajor:

Before entry with uplo = CblasUpper, the array ap must contain the upper triangular part of the symmetric matrix packed sequentially, column-by-column, so that ap[0] contains A_{1, 1}, ap[1] and ap[2] contain A_{1, 2} and A_{2, 2} respectively, and so on. Before entry with uplo = CblasLower, the array ap must contain the lower triangular part of the symmetric matrix packed sequentially, column-by-column, so that ap[0] contains A_{1, 1}, ap[1] and ap[2] contain A_{2, 1} and A_{3, 1} respectively, and so on.

For Layout = CblasRowMajor:

Before entry with uplo = CblasUpper, the array ap must contain the upper triangular part of the symmetric matrix packed sequentially, row-by-row, ap[0] contains A_{1, 1}, ap[1] and ap[2] contain A_{1, 2} and A_{1, 3} respectively, and so on. Before entry with uplo = CblasLower, the array ap must contain the lower triangular part of the symmetric matrix packed sequentially, row-by-row, so that ap[0] contains A_{1, 1}, ap[1] and ap[2] contain A_{2, 1} and A_{2, 2} respectively, and so on.

x

Array, size at least (1 + (n - 1)*abs(incx)). Before entry, the incremented array x must contain the n-element vector x.

incx

Specifies the increment for the elements of x.

The value of incx must not be zero.

beta

Specifies the scalar beta.

When beta is supplied as zero, then y need not be set on input.

y

Array, size at least (1 + (n - 1)*abs(incy)). Before entry, the incremented array y must contain the n-element vector y.

incy

Specifies the increment for the elements of y.

The value of incy must not be zero.

Output Parameters

y: Overwritten by the updated vector y.

Parent topic: BLAS Level 2 Routines

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Developer Reference for Intel® oneAPI Math Kernel Library for C

cblas_?spmv

Syntax

Include Files

Description

Input Parameters

Output Parameters