Poster of Linux kernelThe best gift for a Linux geek
DTRSM

DTRSM

Section: BLAS routine (3) Updated: 16 October 1992
Local index Up
 

NAME

DTRSM - solve one of the matrix equations op( A )*X = alpha*B, or X*op( A ) = alpha*B,  

SYNOPSIS

SUBROUTINE DTRSM
( SIDE, UPLO, TRANSA, DIAG, M, N, ALPHA, A, LDA, B, LDB )

    
CHARACTER*1 SIDE, UPLO, TRANSA, DIAG

    
INTEGER M, N, LDA, LDB

    
DOUBLE PRECISION ALPHA

    
DOUBLE PRECISION A( LDA, * ), B( LDB, * )
 

PURPOSE

DTRSM solves one of the matrix equations

where alpha is a scalar, X and B are m by n matrices, A is a unit, or non-unit, upper or lower triangular matrix and op( A ) is one of


   op( A ) = A   or   op( A ) = A'.

The matrix X is overwritten on B.

 

PARAMETERS

SIDE - CHARACTER*1.
On entry, SIDE specifies whether op( A ) appears on the left or right of X as follows:

SIDE = 'L' or 'l' op( A )*X = alpha*B.

SIDE = 'R' or 'r' X*op( A ) = alpha*B.

Unchanged on exit.

UPLO - CHARACTER*1.
On entry, UPLO specifies whether the matrix A is an upper or lower triangular matrix as follows:

UPLO = 'U' or 'u' A is an upper triangular matrix.

UPLO = 'L' or 'l' A is a lower triangular matrix.

Unchanged on exit.

TRANSA - CHARACTER*1. On entry, TRANSA specifies the form of op( A ) to be used in the matrix multiplication as follows:

TRANSA = 'N' or 'n' op( A ) = A.

TRANSA = 'T' or 't' op( A ) = A'.

TRANSA = 'C' or 'c' op( A ) = A'.

Unchanged on exit.

DIAG - CHARACTER*1.
On entry, DIAG specifies whether or not A is unit triangular as follows:

DIAG = 'U' or 'u' A is assumed to be unit triangular.

DIAG = 'N' or 'n' A is not assumed to be unit triangular.

Unchanged on exit.

M - INTEGER.
On entry, M specifies the number of rows of B. M must be at least zero. Unchanged on exit.
N - INTEGER.
On entry, N specifies the number of columns of B. N must be at least zero. Unchanged on exit.
ALPHA - DOUBLE PRECISION.
On entry, ALPHA specifies the scalar alpha. When alpha is zero then A is not referenced and B need not be set before entry. Unchanged on exit.
A - DOUBLE PRECISION array of DIMENSION ( LDA, k ), where k is m
when SIDE = 'L' or 'l' and is n when SIDE = 'R' or 'r'. Before entry with UPLO = 'U' or 'u', the leading k by k upper triangular part of the array A must contain the upper triangular matrix and the strictly lower triangular part of A is not referenced. Before entry with UPLO = 'L' or 'l', the leading k by k lower triangular part of the array A must contain the lower triangular matrix and the strictly upper triangular part of A is not referenced. Note that when DIAG = 'U' or 'u', the diagonal elements of A are not referenced either, but are assumed to be unity. Unchanged on exit.
LDA - INTEGER.
On entry, LDA specifies the first dimension of A as declared in the calling (sub) program. When SIDE = 'L' or 'l' then LDA must be at least max( 1, m ), when SIDE = 'R' or 'r' then LDA must be at least max( 1, n ). Unchanged on exit.
B - DOUBLE PRECISION array of DIMENSION ( LDB, n ).
Before entry, the leading m by n part of the array B must contain the right-hand side matrix B, and on exit is overwritten by the solution matrix X.
LDB - INTEGER.
On entry, LDB specifies the first dimension of B as declared in the calling (sub) program. LDB must be at least max( 1, m ). 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.


 

Index

NAME
SYNOPSIS
PURPOSE
PARAMETERS

This document was created by man2html, using the manual pages.
Time: 21:45:21 GMT, April 16, 2011