F06YJF (DTRSM) (PDF version)
F06 Chapter Contents
F06 Chapter Introduction
NAG Library Manual

NAG Library Routine Document

F06YJF (DTRSM)

Note:  before using this routine, please read the Users' Note for your implementation to check the interpretation of bold italicised terms and other implementation-dependent details.

+ Contents

    1  Purpose
    7  Accuracy
    9  Example

1  Purpose

F06YJF (DTRSM) performs one of the matrix-matrix operations
BαA-1B, BαA-TB, BαBA-1  or BαBA-T,
where A is a real triangular matrix, B is an m by n real matrix, and α is a real scalar. A-T denotes AT-1  or equivalently A-1T .
No test for singularity or near-singularity of A is included in this routine. Such tests must be performed before calling this routine.

2  Specification

SUBROUTINE F06YJF ( SIDE, UPLO, TRANSA, DIAG, M, N, ALPHA, A, LDA, B, LDB)
INTEGER  M, N, LDA, LDB
REAL (KIND=nag_wp)  ALPHA, A(LDA,*), B(LDB,*)
CHARACTER(1)  SIDE, UPLO, TRANSA, DIAG
The routine may be called by its BLAS name dtrsm.

3  Description

None.

4  References

None.

5  Parameters

1:     SIDE – CHARACTER(1)Input
2:     UPLO – CHARACTER(1)Input
3:     TRANSA – CHARACTER(1)Input
4:     DIAG – CHARACTER(1)Input
5:     M – INTEGERInput
6:     N – INTEGERInput
7:     ALPHA – REAL (KIND=nag_wp)Input
8:     A(LDA,*) – REAL (KIND=nag_wp) arrayInput
Note: the second dimension of the array A must be at least max1,M if SIDE='L' and at least max1,N if SIDE='R'.
On entry: the triangular matrix A; A is m by m if SIDE='L', or n by n if SIDE='R'.
  • If UPLO='U', A is upper triangular and the elements of the array below the diagonal are not referenced.
  • If UPLO='L', A is lower triangular and the elements of the array above the diagonal are not referenced.
  • If DIAG='U', the diagonal elements of A are assumed to be 1, and are not referenced.
9:     LDA – INTEGERInput
On entry: the first dimension of the array A as declared in the (sub)program from which F06YJF (DTRSM) is called.
Constraints:
  • if SIDE='L', LDA max1,M ;
  • if SIDE='R', LDA max1,N .
10:   B(LDB,*) – REAL (KIND=nag_wp) arrayInput/Output
Note: the second dimension of the array B must be at least max1,N.
On entry: the m by n matrix B.
If ALPHA=0, B need not be set.
On exit: the updated matrix B.
11:   LDB – INTEGERInput
On entry: the first dimension of the array B as declared in the (sub)program from which F06YJF (DTRSM) is called.
Constraint: LDB max1,M .

6  Error Indicators and Warnings

None.

7  Accuracy

Not applicable.

8  Further Comments

None.

9  Example

None.

F06YJF (DTRSM) (PDF version)
F06 Chapter Contents
F06 Chapter Introduction
NAG Library Manual

© The Numerical Algorithms Group Ltd, Oxford, UK. 2012