• NAME
• SYNOPSIS
• F95 INTERFACE
• C INTERFACE
• PURPOSE
• ARGUMENTS

NAME

dsyr2k - perform one of the symmetric rank 2k operations C := alpha*A*B' + alpha*B*A' + beta*C or C := alpha*A'*B + alpha*B'*A + beta*C

SYNOPSIS

  SUBROUTINE DSYR2K( UPLO, TRANSA, N, K, ALPHA, A, LDA, B, LDB, BETA, 
 *      C, LDC)
  CHARACTER * 1 UPLO, TRANSA
  INTEGER N, K, LDA, LDB, LDC
  DOUBLE PRECISION ALPHA, BETA
  DOUBLE PRECISION A(LDA,*), B(LDB,*), C(LDC,*)

  SUBROUTINE DSYR2K_64( UPLO, TRANSA, N, K, ALPHA, A, LDA, B, LDB, 
 *      BETA, C, LDC)
  CHARACTER * 1 UPLO, TRANSA
  INTEGER*8 N, K, LDA, LDB, LDC
  DOUBLE PRECISION ALPHA, BETA
  DOUBLE PRECISION A(LDA,*), B(LDB,*), C(LDC,*)

F95 INTERFACE

  SUBROUTINE SYR2K( UPLO, [TRANSA], [N], [K], ALPHA, A, [LDA], B, [LDB], 
 *       BETA, C, [LDC])
  CHARACTER(LEN=1) :: UPLO, TRANSA
  INTEGER :: N, K, LDA, LDB, LDC
  REAL(8) :: ALPHA, BETA
  REAL(8), DIMENSION(:,:) :: A, B, C

  SUBROUTINE SYR2K_64( UPLO, [TRANSA], [N], [K], ALPHA, A, [LDA], B, 
 *       [LDB], BETA, C, [LDC])
  CHARACTER(LEN=1) :: UPLO, TRANSA
  INTEGER(8) :: N, K, LDA, LDB, LDC
  REAL(8) :: ALPHA, BETA
  REAL(8), DIMENSION(:,:) :: A, B, C

C INTERFACE

#include <sunperf.h>

void dsyr2k(char uplo, char transa, int n, int k, double alpha, double *a, int lda, double *b, int ldb, double beta, double *c, int ldc);

void dsyr2k_64(char uplo, char transa, long n, long k, double alpha, double *a, long lda, double *b, long ldb, double beta, double *c, long ldc);

PURPOSE

dsyr2k K performs one of the symmetric rank 2k operations 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 and A and B are n by k matrices in the first case and k by n matrices in the second case.

ARGUMENTS

• UPLO (input)
  On entry, UPLO specifies whether the upper or lower triangular part of the array C is to be referenced as follows:

  UPLO = 'U' or 'u' Only the upper triangular part of C is to be referenced.

  UPLO = 'L' or 'l' Only the lower triangular part of C is to be referenced.

  Unchanged on exit.

• TRANSA (input)
  On entry, TRANSA specifies the operation to be performed as follows:

  TRANSA = 'N' or 'n' C : = alpha*A*B' + alpha*B*A' + beta*C.

  TRANSA = 'T' or 't' C : = alpha*A'*B + alpha*B'*A + beta*C.

  TRANSA = 'C' or 'c' C : = alpha*A'*B + alpha*B'*A + beta*C.

  Unchanged on exit.

• N (input)
  On entry, N specifies the order of the matrix C. N must be at least zero. Unchanged on exit.

• K (input)
  On entry with TRANSA = 'N' or 'n', K specifies the number of columns of the matrices A and B, and on entry with TRANSA = 'T' or 't' or 'C' or 'c', K specifies the number of rows of the matrices A and B. K must be at least zero. Unchanged on exit.

• ALPHA (input)
  On entry, ALPHA specifies the scalar alpha. Unchanged on exit.

• A (input)
  k when TRANSA = 'N' or 'n', and is n otherwise. Before entry with TRANSA = '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. Unchanged on exit.

• LDA (input)
  On entry, LDA specifies the first dimension of A as declared in the calling (sub) program. When TRANSA = 'N' or 'n' then LDA must be at least max( 1, n ), otherwise LDA must be at least max( 1, k ). Unchanged on exit.

• B (input)
  k when TRANSA = 'N' or 'n', and is n otherwise. Before entry with TRANSA = '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. Unchanged on exit.

• LDB (input)
  On entry, LDB specifies the first dimension of B as declared in the calling (sub) program. When TRANSA = 'N' or 'n' then LDB must be at least max( 1, n ), otherwise LDB must be at least max( 1, k ). Unchanged on exit.

• BETA (input)
  On entry, BETA specifies the scalar beta. Unchanged on exit.

• C (input/output)
  Before entry with UPLO = 'U' or 'u', 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. On exit, the upper triangular part of the array C is overwritten by the upper triangular part of the updated matrix.

  Before entry with UPLO = 'L' or 'l', 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. On exit, the lower triangular part of the array C is overwritten by the lower triangular part of the updated matrix.

• LDC (input)
  On entry, LDC specifies the first dimension of C as declared in the calling (sub) program. LDC must be at least max( 1, n ). Unchanged on exit.