# NAG AD Librarys01ba_a1w_f (log_shifted_a1w)

Note: a1w denotes that first order adjoints are computed in working precision; this has the corresponding argument type nagad_a1w_w_rtype. Also available is the t1w (first order tangent linear) mode, the interface of which is implied by replacing a1w by t1w throughout this document. Additionally, the p0w (passive interface, as alternative to the FL interface) mode is available and can be inferred by replacing of active types by the corresponding passive types. The method of codifying AD implementations in the routine name and corresponding argument types is described in the NAG AD Library Introduction.

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## 1Purpose

s01ba_a1w_f is the adjoint version of the primal routine s01baf.

## 2Specification

Fortran Interface
 Subroutine s01ba_a1w_f ( ad_handle, x, lnx1, ifail)
 Integer, Intent (Inout) :: ifail Type (nagad_a1w_w_rtype), Intent (In) :: x Type (nagad_a1w_w_rtype), Intent (Out) :: lnx1 Type (c_ptr), Intent (Inout) :: ad_handle
 void s01ba_a1w_f_ ( void *&ad_handle, const nagad_a1w_w_rtype &x, nagad_a1w_w_rtype &lnx1, Integer &ifail)
The routine may be called by the names s01ba_a1w_f or nagf_specfun_log_shifted_a1w. The corresponding t1w and p0w variants of this routine are also available.

## 3Description

s01ba_a1w_f is the adjoint version of the primal routine s01baf.
s01baf returns a value of the shifted logarithmic function, $\mathrm{ln}\left(1+x\right)$, via the function name. For further information see Section 3 in the documentation for s01baf.

## 4References

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

## 5Arguments

In addition to the arguments present in the interface of the primal routine, s01ba_a1w_f 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_handle – Type (c_ptr) Input/Output
On entry: a handle to the AD configuration data object, as created by x10aa_a1w_f.
2: Input
3: Output
On exit: the value of the shifted logarithmic function, $\mathrm{ln}\left(1+x\right)$.
4: ifail – Integer Input/Output

## 6Error Indicators and Warnings

s01ba_a1w_f preserves all error codes from s01baf and in addition can return:
${\mathbf{ifail}}=-89$
See Section 4.8.2 in the NAG AD Library Introduction for further information.
${\mathbf{ifail}}=-899$
Dynamic memory allocation failed for AD.
See Section 4.8.1 in the NAG AD Library Introduction for further information.

Not applicable.

## 8Parallelism and Performance

s01ba_a1w_f is not threaded in any implementation.

None.

## 10Example

The following examples are variants of the example for s01baf, modified to demonstrate calling the NAG AD Library.

### 10.1Adjoint mode (a1w)

 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

### 10.2Tangent mode (t1w)

 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

### 10.3Passive mode (p0w)

 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