?symv

Developer Reference for Intel® oneAPI Math Kernel Library for C

Download PDF

ID 766684

Date 10/15/2026

Version

Public

?symv

Computes a matrix-vector product for a symmetric matrix.

Syntax

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

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

Include Files

mkl.h

Description

The ?symv 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.

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 array a is used.

If uplo = CblasUpper , then the upper triangular part of the array a is used.

If uplo = CblasLower , then the low triangular part of the array a is used.

n

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

alpha

REAL for ssymv DOUBLE PRECISION for dsymv Specifies the scalar alpha .

a

REAL for ssymv DOUBLE PRECISION for dsymv Array, size (lda, n)lda*n .

Before entry with uplo = CblasUpper , the leading n -by- n upper triangular part of the array a must contain the upper triangular part of the symmetric matrix A and the strictly lower triangular part of a is not referenced. Before entry with uplo = CblasLower , the leading n -by- n lower triangular part of the array a must contain the lower triangular part of the symmetric matrix A and the strictly upper triangular part of a is not referenced.

lda

Specifies the leading dimension of a as declared in the calling (sub)program. The value of lda must be at least max(1, n) .

x

REAL for ssymv DOUBLE PRECISION for dsymv 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

REAL for ssymv DOUBLE PRECISION for dsymv Specifies the scalar beta . When beta is supplied as zero, then y need not be set on input.

y

REAL for ssymv DOUBLE PRECISION for dsymv 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 .

BLAS 95 Interface Notes

There exist FORTRAN 77 and FORTRAN 95 interfaces for this routine. See the Intel® oneMKL Fortran Developer Reference for details.

Select Your Language

Using Intel.com Search

Quick Links

Recent Searches

Advanced Search

Only search in

Developer Reference for Intel® oneAPI Math Kernel Library for C

?symv

Syntax

Include Files

Description

Input Parameters

Output Parameters

BLAS 95 Interface Notes