NAG AD Library
f06pa (dgemv)

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1 Purpose

f06pa is the AD Library version of the primal routine f06paf (dgemv). Based (in the C++ interface) on overload resolution, f06pa can be used for primal, tangent and adjoint evaluation. It supports tangents and adjoints of first order.

2 Specification

Fortran Interface
Subroutine f06pa_AD_f ( ad_handle, trans, m, n, alpha, a, lda, x, incx, beta, y, incy, ifail)
Integer, Intent (In) :: m, n, lda, incx, incy
Integer, Intent (Inout) :: ifail
ADTYPE, Intent (In) :: alpha, a(lda,*), x(*), beta
ADTYPE, Intent (Inout) :: y(*)
Character (1), Intent (In) :: trans
Type (c_ptr), Intent (Inout) :: ad_handle
Corresponding to the overloaded C++ function, the Fortran interface provides five routines with names reflecting the type used for active real arguments. The actual subroutine and type names are formed by replacing AD and ADTYPE in the above as follows:
when ADTYPE is Real(kind=nag_wp) then AD is p0w
when ADTYPE is Type(nagad_a1w_w_rtype) then AD is a1w
when ADTYPE is Type(nagad_t1w_w_rtype) then AD is t1w
C++ Header Interface
#include <dco.hpp>
#include <nagad.h>
namespace nag {
namespace ad {
void f06pa ( void *&ad_handle, const char *trans, const Integer &m, const Integer &n, const ADTYPE &alpha, const ADTYPE a[], const Integer &lda, const ADTYPE x[], const Integer &incx, const ADTYPE &beta, ADTYPE y[], const Integer &incy, Integer &ifail)
The function is overloaded on ADTYPE which represents the type of active arguments. ADTYPE may be any of the following types:
Note: this function can be used with AD tools other than dco/c++. For details, please contact NAG.

3 Description

f06pa is the AD Library version of the primal routine f06paf (dgemv).
f06paf (dgemv) computes the matrix-vector product for a real general matrix or its transpose. For further information see Section 3 in the documentation for f06paf (dgemv).

4 References

5 Arguments

In addition to the arguments present in the interface of the primal routine, f06pa includes some arguments specific to AD.
A brief summary of the AD specific arguments is given below. For the remainder, links are provided to the corresponding argument from the primal routine. A tooltip popup for all arguments can be found by hovering over the argument name in Section 2 and in this section.
1: ad_handle – Pointer to AD Data Input/Output
On entry: a handle to the AD configuration data object, as created by x10aa.
2: trans – character Input
3: m – Integer Input
4: n – Integer Input
5: alphaADTYPE Input
6: a(lda, *) – ADTYPE array Input
7: lda – Integer Input
8: x(*) – ADTYPE array Input
9: incx – Integer Input
10: betaADTYPE Input
11: y(*) – ADTYPE array Input/Output
12: incy – Integer Input
13: ifail – Integer Input/Output
On entry: must be set to 0, -1  or  1. On exit: any errors are indicated as described in Section 6.

6 Error Indicators and Warnings

There are no specific error codes from f06paf (dgemv), however f06pa can return:
An unexpected AD error has been triggered by this routine. Please contact NAG.
See Section 4.8.2 in the NAG AD Library Introduction for further information.
The routine was called using a mode that has not yet been implemented.
On entry: ad_handle is nullptr.
This check is only made if the overloaded C++ interface is used with arguments not of type double.
A C++ exception was thrown.
The error message will show the details of the C++ exception text.
Dynamic memory allocation failed for AD.
See Section 4.8.1 in the NAG AD Library Introduction for further information.

7 Accuracy

Not applicable.

8 Parallelism and Performance

f06pa is not threaded in any implementation.

9 Further Comments


10 Example

The following examples are variants of the example for f06paf (dgemv), modified to demonstrate calling the NAG AD Library.

10.1 Adjoint modes

Language Source File Data Results
Fortran f06pa_a1w_fe.f90 f06pa_a1w_fe.d f06pa_a1w_fe.r
C++ f06pa_a1w_hcppe.cpp f06pa_a1w_hcppe.d f06pa_a1w_hcppe.r

10.2 Tangent modes

Language Source File Data Results
Fortran f06pa_t1w_fe.f90 f06pa_t1w_fe.d f06pa_t1w_fe.r
C++ f06pa_t1w_hcppe.cpp f06pa_t1w_hcppe.d f06pa_t1w_hcppe.r

10.3 Passive mode

Language Source File Data Results
Fortran f06pa_p0w_fe.f90 f06pa_p0w_fe.d f06pa_p0w_fe.r
C++ f06pa_p0w_hcppe.cpp f06pa_p0w_hcppe.d f06pa_p0w_hcppe.r