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'

'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'

'L'

3: $m$ – Integer Input

On entry:

m

, the number of rows of the matrices

B

and

C

; the order of

A

side ='L'

Constraint:

m \geq 0

4: $n$ – Integer Input

On entry:

n

, the number of columns of the matrices

B

and

C

; the order of

A

side ='R'

Constraint:

n \geq 0

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)

side ='L'

and at least

\max (1, n)

side ='R'

On entry: the symmetric matrix

A

;

A

m \times m

side ='L'

, or

n \times n

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 $side ='L'$ , $lda \geq \max (1, m)$ ;
if $side ='R'$ , $lda \geq \max (1, n)$ .

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 \times 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 \geq \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 \times n

matrix

C

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 \geq \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.