NAG Toolbox: nag_matop_real_gen_matmul (f01ck)

Purpose

Syntax

Description

References

Parameters

Compulsory Input Parameters

1:     $\mathrm{b}\left(\mathbf{n},\mathbf{m}\right)$ – double array

The $n$ by $m$ matrix $B$.

2:     $\mathrm{c}\left(\mathbf{m},\mathbf{p}\right)$ – double array

The $m$ by $p$ matrix $C$.

3:     $\mathrm{opt}$ – int64int32nag_int scalar

The value of opt determines which array is to contain the final result.

$\mathbf{opt}=1$

a must be distinct from b and c and, on exit, contains the result. b and c need not be distinct in this case.

$\mathbf{opt}=2$

b must be distinct from c and on exit, contains the result. a is not used in this case and need not be distinct from b or c.

$\mathbf{opt}=3$

c must be distinct from b and on exit, contains the result. a is not used in this case and need not be distinct from b or c.

Constraint: $1\le \mathbf{opt}\le 3$.

Optional Input Parameters

1:     $\mathrm{n}$ – int64int32nag_int scalar

Default: the first dimension of the array b.

$n$, the number of rows of the array $A$ and of the array $B$.

Constraints:

• if $\mathbf{opt}=3$, $\mathbf{n}=\mathbf{m}$;
• otherwise $\mathbf{n}\ge 1$.

2:     $\mathrm{p}$ – int64int32nag_int scalar

Default: the second dimension of the array c.

$p$, the number of columns of the array $A$ and of the array $C$.

Constraints:

• if $\mathbf{opt}=2$, $\mathbf{p}=\mathbf{m}$;
• otherwise $\mathbf{p}\ge 1$.

3:     $\mathrm{m}$ – int64int32nag_int scalar

Default: the first dimension of the array c and the second dimension of the array b. (An error is raised if these dimensions are not equal.)

$m$, the number of columns of the array $B$ and rows of the array $C$.

Constraints:

• if $\mathbf{opt}=2$, $\mathbf{m}=\mathbf{p}$;
• if $\mathbf{opt}=3$, $\mathbf{m}=\mathbf{n}$;
• if $\mathbf{opt}\ne 1$, $\mathbf{m}\le \mathit{iz}$;
• otherwise $\mathbf{m}\ge 1$.

Output Parameters

1:     $\mathrm{a}\left(\mathbf{n},\mathbf{p}\right)$ – double array

If $\mathbf{opt}=1$, a contains the result of the matrix multiplication.

2:     $\mathrm{b}\left(\mathbf{n},\mathbf{m}\right)$ – double array

If $\mathbf{opt}=2$, b contains the result of the multiplication.

3:     $\mathrm{c}\left(\mathbf{m},\mathbf{p}\right)$ – double array

If $\mathbf{opt}=3$, c contains the result of the multiplication.

4:     $\mathrm{ifail}$ – int64int32nag_int scalar

$\mathbf{ifail}=\mathbf{0}$ unless the function detects an error (see Error Indicators and Warnings).

Error Indicators and Warnings

   $\mathbf{ifail}=1$

On entry, m or p or $\mathbf{n}\le 0$.

   $\mathbf{ifail}=2$

$\mathbf{opt}=2$ and $\mathbf{m}\ne \mathbf{p}$.

   $\mathbf{ifail}=3$

$\mathbf{opt}=3$ and $\mathbf{n}\ne \mathbf{m}$.

   $\mathbf{ifail}=4$

$\mathbf{opt}\ne 1$ and $\mathit{iz}<\mathbf{m}$.

   $\mathbf{ifail}=-99$

An unexpected error has been triggered by this routine. Please contact NAG.

   $\mathbf{ifail}=-399$

Your licence key may have expired or may not have been installed correctly.

   $\mathbf{ifail}=-999$

Dynamic memory allocation failed.

Accuracy

Further Comments

Example

Open in the MATLAB editor: f01ck_example

function f01ck_example


fprintf('f01ck example results\n\n');

% Matrices B and C
b = [0, 1, 2;
     1, 2, 3];
c = [0, 1;
     1, 2;
     2, 3];

% Calculate A = BC
opt = int64(1);
[a, b, c, ifail] = f01ck(b, c, opt);

disp('Martix A');
disp(a);

f01ck example results

Martix A
     5     8
     8    14