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++ Interface

#include <dco.hpp>
#include <nagad.h>
namespace nag {
namespace ad {

void f06pa (

handle_t &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:
double,
dco::ga1s<double>::type,
dco::gt1s<double>::type

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 – nag::ad::handle_t Input/Output: On entry: a configuration object that holds information on the differentiation strategy. Details on setting the AD strategy are described in AD handle object in the NAG AD Library Introduction.
2: trans – character Input
3: m – Integer Input
4: n – Integer Input
5: alpha – ADTYPE Input
6: a(lda, $*$ ) – ADTYPE array Input
7: lda – Integer Input
8: x( $*$ ) – ADTYPE array Input
9: incx – Integer Input
10: beta – ADTYPE Input
11: y( $*$ ) – ADTYPE array Input/Output: Please consult Overwriting of Inputs in the NAG AD Library Introduction.
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:

$ifail = - 89$: An unexpected AD error has been triggered by this routine. Please contact NAG.
See Error Handling in the NAG AD Library Introduction for further information.

$ifail = - 199$: The routine was called using a strategy that has not yet been implemented.
See AD Strategies in the NAG AD Library Introduction for further information.

$ifail = - 444$: A C++ exception was thrown.
The error message will show the details of the C++ exception text.

$ifail = - 899$: Dynamic memory allocation failed for AD.
See Error Handling 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

None.

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

NAG Library Manual, Mark 30.1

Interfaces: FL CL CPP AD

NAG AD Library Introduction

F06 (Blas) Chapter Contents

F06 (Blas) Chapter Introduction (FL)

f06pa: FL CL CPP AD

NAG AD Libraryf06pa (dgemv)

▸▿ Contents

1 Purpose