Developer Reference for Intel® oneAPI Math Kernel Library for C
?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
-
REAL for ssyr2k DOUBLE PRECISION for dsyr2k COMPLEX for csyr2k DOUBLE COMPLEX for zsyr2k Specifies the scalar alpha .
- a
-
REAL for ssyr2k DOUBLE PRECISION for dsyr2k COMPLEX for csyr2k DOUBLE COMPLEX for zsyr2k Array, size (lda, ka) , where ka is k when trans= 'N' or 'n' , and is n otherwise. Before entry with trans= 'N' or 'n' , the leading n -by- k part of the array a must contain the matrix A , otherwise the leading k -by- n part of the array a must contain the matrix A .
- lda
-
Specifies the leading dimension of a as declared in the calling (sub)program.
When trans= 'N' or 'n'trans= 'N' or 'n' , then lda must be at least max(1, n) , otherwise lda must be at least max(1, k) .
- b
-
REAL for ssyr2k DOUBLE PRECISION for dsyr2k COMPLEX for csyr2k DOUBLE COMPLEX for zsyr2k Array, size (ldb, kb) , where kb is k when trans= 'N' or 'n' , and is n otherwise. Before entry with trans= 'N' or 'n' , the leading n -by- k part of the array b must contain the matrix B , otherwise the leading k -by- n part of the array b must contain the matrix B .
- ldb
-
Specifies the leading dimension of a as declared in the calling (sub)program.
When trans= 'N' or 'n' , then ldb must be at least max(1, n) , otherwise ldb must be at least max(1, k) .
- beta
-
REAL for ssyr2k DOUBLE PRECISION for dsyr2k COMPLEX for csyr2k DOUBLE COMPLEX for zsyr2k Specifies the scalar beta .
- c
-
REAL for ssyr2k DOUBLE PRECISION for dsyr2k COMPLEX for csyr2k DOUBLE COMPLEX for zsyr2k
Array, size (ldc, n)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.
BLAS 95 Interface Notes
There exist FORTRAN 77 and FORTRAN 95 interfaces for this routine. See the Intel® oneMKL Fortran Developer Reference for details.