NAG AD Library
s01ba (log_shifted)

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1 Purpose

s01ba is the AD Library version of the primal routine s01baf. Based (in the C++ interface) on overload resolution, s01ba can be used for primal, tangent and adjoint evaluation. It supports tangents and adjoints of first order.

2 Specification

Fortran Interface
Subroutine s01ba_AD_f ( ad_handle, x, lnx1, ifail)
Integer, Intent (Inout) :: ifail
ADTYPE, Intent (In) :: x
ADTYPE, Intent (Out) :: lnx1
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 s01ba ( handle_t &ad_handle, const ADTYPE &x, ADTYPE &lnx1, 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

s01ba is the AD Library version of the primal routine s01baf.
s01baf returns a value of the shifted logarithmic function, ln(1+x), via the function name. For further information see Section 3 in the documentation for s01baf.

4 References

Lyusternik L A, Chervonenkis O A and Yanpolskii A R (1965) Handbook for Computing Elementary Functions p. 57 Pergamon Press

5 Arguments

In addition to the arguments present in the interface of the primal routine, s01ba 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.
Note that the primal routine is a function whereas s01ba_a1w_f, is a subroutine, where the function value is returned in the additional output parameter, lnx1.
1: ad_handlenag::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: xADTYPE Input
3: lnx1ADTYPE Output
On exit: the value of the shifted logarithmic function, ln(1+x).
4: ifail – Integer Input/Output

6 Error Indicators and Warnings

s01ba preserves all error codes from s01baf and in addition can return:
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.
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.
A C++ exception was thrown.
The error message will show the details of the C++ exception text.
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

s01ba is not threaded in any implementation.

9 Further Comments


10 Example

The following examples are variants of the example for s01baf, modified to demonstrate calling the NAG AD Library.
Description of the primal example.
The example program reads values of the argument x from a file, evaluates the function at each value of x and prints the results.

10.1 Adjoint modes

Language Source File Data Results
Fortran s01ba_a1w_fe.f90 s01ba_a1w_fe.d s01ba_a1w_fe.r
C++ s01ba_a1w_hcppe.cpp s01ba_a1w_hcppe.d s01ba_a1w_hcppe.r

10.2 Tangent modes

Language Source File Data Results
Fortran s01ba_t1w_fe.f90 s01ba_t1w_fe.d s01ba_t1w_fe.r
C++ s01ba_t1w_hcppe.cpp s01ba_t1w_hcppe.d s01ba_t1w_hcppe.r

10.3 Passive mode

Language Source File Data Results
Fortran s01ba_p0w_fe.f90 s01ba_p0w_fe.d s01ba_p0w_fe.r
C++ s01ba_p0w_hcppe.cpp s01ba_p0w_hcppe.d s01ba_p0w_hcppe.r