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AIX Version 4.3 Base Operating System and Extensions Technical Reference, Volume 2
STRSM, DTRSM, CTRSM, or ZTRSM Subroutine
Purpose
Solves certain matrix equations.
Library
BLAS Library (libblas.a)
FORTRAN Syntax
SUBROUTINE STRSM(SIDE, UPLO, TRANSA, DIAG,
M, N, ALPHA, A, LDA, B, LDB)
CHARACTER*1 SIDE,UPLO,TRANSA,DIAG
INTEGER M,N,LDA,LDB
REAL ALPHA
REAL A(LDA,*), B(LDB,*)
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,*)
SUBROUTINE CTRSM(SIDE, UPLO, TRANSA, DIAG,
M, N, ALPHA, A, LDA, B, LDB)
CHARACTER*1 SIDE,UPLO,TRANSA,DIAG
INTEGER M,N,LDA,LDB
COMPLEX ALPHA
COMPLEX A(LDA,*), B(LDB,*)
SUBROUTINE ZTRSM(SIDE, UPLO, TRANSA, DIAG,
M, N, ALPHA, A, LDA, B, LDB)
CHARACTER*1 SIDE,UPLO,TRANSA,DIAG
INTEGER M,N,LDA,LDB
COMPLEX*16 ALPHA
COMPLEX*16 A(LDA,*), B(LDB,*)
Description
The STRSM, DTRSM, CTRSM, or ZTRSM subroutine solves one of the matrix equations:
- op( A ) * X = alpha * B
- X * op( A ) = alpha * B
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 either op( A ) = A or op( A ) = A'. The matrix X is overwritten on B.
Parameters
SIDE |
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 |
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 |
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 |
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 |
On entry, M specifies the number of rows of B; M must be at least 0; unchanged on exit. |
N |
On entry, N specifies the number of columns of B; N must be at least 0; unchanged on exit. |
ALPHA |
On entry, ALPHA specifies the scalar alpha. When alpha is 0 then A is not referenced and B need not be set before entry; unchanged on exit. |
A |
An array of dimension ( LDA, k ), where k is M when SIDE = 'L' or 'l' and is N when SIDE = 'R' or 'r'. On 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; on 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. When DIAG = 'U' or 'u', the diagonal elements of A are not referenced, but are assumed to be unity; unchanged on exit. |
LDA |
On entry, LDA specifies the first dimension of A as declared in the calling (sub) program. When SIDE = 'L' or 'l', LDA must be at least max( 1, M ); when SIDE = 'R' or 'r', LDA must be at least max( 1, N ); unchanged on exit. |
B |
An array of dimension ( LDB, N ); on 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 |
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. |
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