DSYRK(l) BLAS routine DSYRK(l)
NAME
DSYRK - perform one of the symmetric rank k operations C := alpha*A*A' + beta*C,
SYNOPSIS
SUBROUTINE DSYRK ( UPLO, TRANS, N, K, ALPHA, A, LDA, BETA, C, LDC )
CHARACTER*1 UPLO, TRANS
INTEGER N, K, LDA, LDC
DOUBLE PRECISION ALPHA, BETA
DOUBLE PRECISION A( LDA, * ), C( LDC, * )
PURPOSE
DSYRK performs one of the symmetric rank k operations
or
C := alpha*A'*A + beta*C,
where alpha and beta are scalars, C is an n by n symmetric matrix and A is an n by k matrix in the first case and a k by n matrix
in the second case.
PARAMETERS
UPLO - CHARACTER*1.
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.
TRANS - CHARACTER*1.
On entry, TRANS specifies the operation to be performed as follows:
TRANS = 'N' or 'n' C := alpha*A*A' + beta*C.
TRANS = 'T' or 't' C := alpha*A'*A + beta*C.
TRANS = 'C' or 'c' C := alpha*A'*A + beta*C.
Unchanged on exit.
N - INTEGER.
On entry, N specifies the order of the matrix C. N must be at least zero. Unchanged on exit.
K - INTEGER.
On entry with TRANS = 'N' or 'n', K specifies the number of columns of the matrix A, and on entry with TRANS =
'T' or 't' or 'C' or 'c', K specifies the number of rows of the matrix A. K must be at least zero. Unchanged on exit.
ALPHA - DOUBLE PRECISION.
On entry, ALPHA specifies the scalar alpha. Unchanged on exit.
A - DOUBLE PRECISION array of DIMENSION ( 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. Unchanged on exit.
LDA - INTEGER.
On entry, LDA specifies the first dimension of A as declared in the calling (sub) program. When TRANS = 'N' or 'n' then LDA
must be at least max( 1, n ), otherwise LDA must be at least max( 1, k ). Unchanged on exit.
BETA - DOUBLE PRECISION.
On entry, BETA specifies the scalar beta. Unchanged on exit.
C - DOUBLE PRECISION array of DIMENSION ( LDC, n ).
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 - INTEGER.
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.
Level 3 Blas routine.
-- Written on 8-February-1989. Jack Dongarra, Argonne National Laboratory. Iain Duff, AERE Harwell. Jeremy Du Croz, Numerical
Algorithms Group Ltd. Sven Hammarling, Numerical Algorithms Group Ltd.
BLAS routine 16 October 1992 DSYRK(l)