NAG FL Interface
f06ycf (dsymm)

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1 Purpose

f06ycf performs one of the matrix-matrix operations
CαAB + βC   or   CαBA + βC ,  
where A is a real symmetric matrix, B and C are m×n real matrices, and α and β are real scalars.

2 Specification

Fortran Interface
Subroutine f06ycf ( side, uplo, m, n, alpha, a, lda, b, ldb, beta, c, ldc)
Integer, Intent (In) :: m, n, lda, ldb, ldc
Real (Kind=nag_wp), Intent (In) :: alpha, a(lda,*), b(ldb,*), beta
Real (Kind=nag_wp), Intent (Inout) :: c(ldc,*)
Character (1), Intent (In) :: side, uplo
C Header Interface
#include <nag.h>
void  f06ycf_ (const char *side, const char *uplo, const Integer *m, const Integer *n, const double *alpha, const double a[], const Integer *lda, const double b[], const Integer *ldb, const double *beta, double c[], const Integer *ldc, const Charlen length_side, const Charlen length_uplo)
The routine may be called by the names f06ycf, nagf_blas_dsymm or its BLAS name dsymm.

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 the upper or lower triangular part of A is stored.
uplo='U'
The upper triangular part of A is stored.
uplo='L'
The lower triangular part of A is stored.
Constraint: uplo='U' or 'L'.
3: m Integer Input
On entry: m, the number of rows of the matrices B and C; the order of A if side='L'.
Constraint: m0.
4: n Integer Input
On entry: n, the number of columns of the matrices B and C; the order of A if side='R'.
Constraint: n0.
5: alpha Real (Kind=nag_wp) Input
On entry: the scalar α.
6: a(lda,*) Real (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 symmetric matrix A; A is m×m if side='L', or n×n if side='R'.
  • If uplo='U', the upper triangular part of A must be stored and the elements of the array below the diagonal are not referenced.
  • If uplo='L', the lower triangular part of A must be stored and the elements of the array above the diagonal are not referenced.
7: lda Integer Input
On entry: the first dimension of the array a as declared in the (sub)program from which f06ycf is called.
Constraints:
  • if side='L', lda max(1,m) ;
  • if side='R', lda max(1,n) .
8: b(ldb,*) Real (Kind=nag_wp) array Input
Note: the second dimension of the array b must be at least max(1,n).
On entry: the m×n matrix B.
9: ldb Integer Input
On entry: the first dimension of the array b as declared in the (sub)program from which f06ycf is called.
Constraint: ldb max(1,m) .
10: beta Real (Kind=nag_wp) Input
On entry: the scalar β.
11: c(ldc,*) Real (Kind=nag_wp) array Input/Output
Note: the second dimension of the array c must be at least max(1,n).
On entry: the m×n matrix C.
If beta=0.0, c need not be set.
On exit: the updated matrix C.
12: ldc Integer Input
On entry: the first dimension of the array c as declared in the (sub)program from which f06ycf is called.
Constraint: ldc 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.
f06ycf 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.