NAG AD Library
e01aa_a1w_f (dim1_aitken_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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1 Purpose

e01aa_a1w_f is the adjoint version of the primal routine e01aaf.

2 Specification

Fortran Interface
Subroutine e01aa_a1w_f ( ad_handle, a, b, c, n1, n2, n, x, ifail)
Integer, Intent (In) :: n1, n2, n
Integer, Intent (Inout) :: ifail
Type (nagad_a1w_w_rtype), Intent (In) :: x
Type (nagad_a1w_w_rtype), Intent (Inout) :: a(n+1), b(n+1)
Type (nagad_a1w_w_rtype), Intent (Out) :: c(n*(n+1)/2)
Type (c_ptr), Intent (Inout) :: ad_handle
C++ Header Interface
#include <nagad.h>
void e01aa_a1w_f_ ( void *&ad_handle, nagad_a1w_w_rtype a[], nagad_a1w_w_rtype b[], nagad_a1w_w_rtype c[], const Integer &n1, const Integer &n2, const Integer &n, const nagad_a1w_w_rtype &x, Integer &ifail)
The routine may be called by the names e01aa_a1w_f or nagf_interp_dim1_aitken_a1w. The corresponding t1w and p0w variants of this routine are also available.

3 Description

e01aa_a1w_f is the adjoint version of the primal routine e01aaf.
e01aaf interpolates a function of one variable at a given point x from a table of function values yi evaluated at equidistant or non-equidistant points xi, for i=1,2,,n+1, using Aitken's technique of successive linear interpolations. For further information see Section 3 in the documentation for e01aaf.

4 References

Fröberg C E (1970) Introduction to Numerical Analysis Addison–Wesley

5 Arguments

In addition to the arguments present in the interface of the primal routine, e01aa_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.
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: a(n+1) – Type (nagad_a1w_w_rtype) array Input/Output
3: b(n+1) – Type (nagad_a1w_w_rtype) array Input/Output
4: c(n×(n+1)/2) – Type (nagad_a1w_w_rtype) array Output
5: n1 – Integer Input
6: n2 – Integer Input
7: n – Integer Input
8: xType (nagad_a1w_w_rtype) Input
9: 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 e01aaf, however e01aa_a1w_f 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.
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

e01aa_a1w_f is not threaded in any implementation.

9 Further Comments


10 Example

The following examples are variants of the example for e01aaf, modified to demonstrate calling the NAG AD Library.

10.1 Adjoint mode (a1w)

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10.2 Tangent mode (t1w)

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10.3 Passive mode (p0w)

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