cblas_?syr

Performs a rank-1 update of a symmetric matrix.

Syntax

void cblas_ssyr (const CBLAS_LAYOUT Layout, const CBLAS_UPLO uplo, const MKL_INT n, const float alpha, const float *x, const MKL_INT incx, float *a, const MKL_INT lda);

void cblas_dsyr (const CBLAS_LAYOUT Layout, const CBLAS_UPLO uplo, const MKL_INT n, const double alpha, const double *x, const MKL_INT incx, double *a, const MKL_INT lda);

Include Files

  • mkl.h

Description

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

A := alpha*x*x' + A ,

where:

alpha is a real scalar,

x is an n-element vector,

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

Specifies the scalar alpha.

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.

a

Array, size 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).

Output Parameters

a

With uplo = CblasUpper, the upper triangular part of the array a is overwritten by the upper triangular part of the updated matrix.

With uplo = CblasLower, the lower triangular part of the array a is overwritten by the lower triangular part of the updated matrix.

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