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Technical Reference: Base Operating System and Extensions , Volume 2
Solves certain matrix
equations.
BLAS Library
(libblas.a)
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,*)
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 nonunit, upper or lower triangular matrix, and op( A ) is
either op( A ) = A or op( A ) =
A'. The matrix X is overwritten on B.
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 righthand 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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