NAG FL Interface
f06zjf (ztrsm)

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1 Purpose

f06zjf performs one of the matrix-matrix operations
BαA-1B , BαA-TB , BαA-HB , BαBA-1 , BαBA-T   or BαBA-H ,  
where A is a complex triangular matrix, B is an m×n complex matrix, and α is a complex scalar. A-T denotes (AT)-1 or equivalently (A-1)T ; A-H denotes (AH)-1 or equivalently (A-1)H .
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

Fortran Interface
Subroutine f06zjf ( side, uplo, transa, diag, m, n, alpha, a, lda, b, ldb)
Integer, Intent (In) :: m, n, lda, ldb
Complex (Kind=nag_wp), Intent (In) :: alpha, a(lda,*)
Complex (Kind=nag_wp), Intent (Inout) :: b(ldb,*)
Character (1), Intent (In) :: side, uplo, transa, diag
C Header Interface
#include <nag.h>
void  f06zjf_ (const char *side, const char *uplo, const char *transa, const char *diag, const Integer *m, const Integer *n, const Complex *alpha, const Complex a[], const Integer *lda, Complex b[], const Integer *ldb, const Charlen length_side, const Charlen length_uplo, const Charlen length_transa, const Charlen length_diag)
The routine may be called by the names f06zjf, nagf_blas_ztrsm or its BLAS name ztrsm.

3 Description

None.

4 References

None.

5 Arguments

1: side Character(1) Input
On entry: specifies whether B is operated on from the left or the right.
side='L'
B is pre-multiplied from the left.
side='R'
B is post-multiplied from the right.
Constraint: side='L' or 'R'.
2: uplo Character(1) Input
On entry: specifies whether A is upper or lower triangular.
uplo='U'
A is upper triangular.
uplo='L'
A is lower triangular.
Constraint: uplo='U' or 'L'.
3: transa Character(1) Input
On entry: specifies whether the operation involves A-1, A-T or A-H.
transa='N'
The operation involves A-1.
transa='T'
The operation involves A-T.
transa='C'
The operation involves A-H.
Constraint: transa='N', 'T' or 'C'.
4: diag Character(1) Input
On entry: specifies whether A has nonunit or unit diagonal elements.
diag='N'
The diagonal elements are stored explicitly.
diag='U'
The diagonal elements are assumed to be 1, and are not referenced.
Constraint: diag='N' or 'U'.
5: m Integer Input
On entry: m, the number of rows of the matrix B; the order of A if side='L'.
Constraint: m0.
6: n Integer Input
On entry: n, the number of columns of the matrix B; the order of A if side='R'.
Constraint: n0.
7: alpha Complex (Kind=nag_wp) Input
On entry: the scalar α.
8: a(lda,*) Complex (Kind=nag_wp) array Input
Note: the second dimension of the array a must be at least max(1,m) if side='L' and at least max(1,n) if side='R'.
On entry: the triangular matrix A; A is m×m if side='L', or n×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 Integer Input
On entry: the first dimension of the array a as declared in the (sub)program from which f06zjf is called.
Constraints:
  • if side='L', lda max(1,m) ;
  • if side='R', lda max(1,n) .
10: b(ldb,*) Complex (Kind=nag_wp) array Input/Output
Note: the second dimension of the array b must be at least max(1,n).
On entry: the m×n matrix B.
If alpha=0, b need not be set.
On exit: the updated matrix B.
11: ldb Integer Input
On entry: the first dimension of the array b as declared in the (sub)program from which f06zjf is called.
Constraint: ldb max(1,m) .

6 Error Indicators and Warnings

None.

7 Accuracy

Not applicable.

8 Parallelism and Performance

Background information to multithreading can be found in the Multithreading documentation.
f06zjf is threaded by NAG for parallel execution in multithreaded implementations of the NAG Library.
Please consult the X06 Chapter Introduction for information on how to control and interrogate the OpenMP environment used within this routine. Please also consult the Users' Note for your implementation for any additional implementation-specific information.

9 Further Comments

None.

10 Example

None.