cblas_?syr2k

Performs a symmetric rank-2k update.

Syntax

void cblas_ssyr2k (const CBLAS_LAYOUT Layout, const CBLAS_UPLO uplo, const CBLAS_TRANSPOSE trans, const MKL_INT n, const MKL_INT k, const float alpha, const float *a, const MKL_INT lda, const float *b, const MKL_INT ldb, const float beta, float *c, const MKL_INT ldc);

void cblas_dsyr2k (const CBLAS_LAYOUT Layout, const CBLAS_UPLO uplo, const CBLAS_TRANSPOSE trans, const MKL_INT n, const MKL_INT k, const double alpha, const double *a, const MKL_INT lda, const double *b, const MKL_INT ldb, const double beta, double *c, const MKL_INT ldc);

void cblas_csyr2k (const CBLAS_LAYOUT Layout, const CBLAS_UPLO uplo, const CBLAS_TRANSPOSE trans, const MKL_INT n, const MKL_INT k, const void *alpha, const void *a, const MKL_INT lda, const void *b, const MKL_INT ldb, const void *beta, void *c, const MKL_INT ldc);

void cblas_zsyr2k (const CBLAS_LAYOUT Layout, const CBLAS_UPLO uplo, const CBLAS_TRANSPOSE trans, const MKL_INT n, const MKL_INT k, const void *alpha, const void *a, const MKL_INT lda, const void *b, const MKL_INT ldb, const void *beta, void *c, const MKL_INT ldc);

Include Files

  • mkl.h

Description

The ?syr2k routines perform a rank-2k matrix-matrix operation for a symmetric matrix C using general matrices A and B. The operation is defined as

C := alpha*A*B' + alpha*B*A' + beta*C,

or

C := alpha*A'*B + alpha*B'*A + beta*C,

where:

alpha and beta are scalars,

C is an n-by-n symmetric matrix,

A and B are n-by-k matrices in the first case, and k-by-n matrices in the second case.

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 c is used.

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

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

trans

Specifies the operation:

if trans=CblasNoTrans, then C := alpha*A*B'+alpha*B*A'+beta*C;

if trans=CblasTrans, then C := alpha*A'*B +alpha*B'*A +beta*C;

if trans=CblasConjTrans, then C := alpha*A'*B +alpha*B'*A +beta*C.

n

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

k

On entry with trans=CblasNoTrans, k specifies the number of columns of the matrices A and B, and on entry with trans=CblasTrans or trans=CblasConjTrans, k specifies the number of rows of the matrices A and B. The value of k must be at least zero.

alpha

Specifies the scalar alpha.

a
 

trans=CblasNoTrans

trans=CblasConjTrans

Layout = CblasColMajor

Array, size lda*k.

Before entry, the leading n-by-k part of the array a must contain the matrix A.

Array, size lda*n.

Before entry, the leading k-by-n part of the array a must contain the matrix A.

Layout = CblasRowMajor

Array, size lda*n.

Before entry, the leading k-by-n part of the array a must contain the matrix A.

Array, size lda*k.

Before entry, the leading n-by-k part of the array a must contain the matrix A.

lda

Specifies the leading dimension of a as declared in the calling (sub)program.

 

trans=CblasNoTrans

trans=CblasConjTrans

Layout = CblasColMajor

lda must be at least max(1, n).

lda must be at least max(1, k)

Layout = CblasRowMajor

lda must be at least max(1, k)

lda must be at least max(1, n).

b
 

trans=CblasNoTrans

trans=CblasConjTrans

Layout = CblasColMajor

Array, size ldb*k.

Before entry, the leading n-by-k part of the array b must contain the matrix B.

Array, size ldb*n.

Before entry, the leading k-by-n part of the array b must contain the matrix B.

Layout = CblasRowMajor

Array, size lda*n.

Before entry, the leading k-by-n part of the array b must contain the matrix B.

Array, size lda*k.

Before entry, the leading n-by-k part of the array b must contain the matrix B.

ldb

Specifies the leading dimension of a as declared in the calling (sub)program.

 

trans=CblasNoTrans

trans=CblasConjTrans

Layout = CblasColMajor

ldb must be at least max(1, n).

ldb must be at least max(1, k)

Layout = CblasRowMajor

ldb must be at least max(1, k)

ldb must be at least max(1, n).

beta

Specifies the scalar beta.

c

Array, size ldc* n. Before entry with uplo = CblasUpper, the leading n-by-n upper triangular part of the array c must contain the upper triangular part of the symmetric matrix and the strictly lower triangular part of c is not referenced.

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

ldc

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

Output Parameters

c

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

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

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