NAG AD Library
f11db (real_gen_precon_ilu_solve)

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1 Purpose

f11db is the AD Library version of the primal routine f11dbf. Based (in the C++ interface) on overload resolution, f11db can be used for primal, tangent and adjoint evaluation. It supports tangents and adjoints of first order.

2 Specification

Fortran Interface
Subroutine f11db_AD_f ( ad_handle, trans, n, a, la, irow, icol, ipivp, ipivq, istr, idiag, check, y, x, ifail)
Integer, Intent (In) :: n, la, irow(la), icol(la), istr(n+1), idiag(n)
Integer, Intent (Inout) :: ipivp(n), ipivq(n), ifail
ADTYPE, Intent (In) :: a(la), y(n)
ADTYPE, Intent (Out) :: x(n)
Character (1), Intent (In) :: trans, check
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 f11db ( handle_t &ad_handle, const char *trans, const Integer &n, const ADTYPE a[], const Integer &la, const Integer irow[], const Integer icol[], Integer ipivp[], Integer ipivq[], const Integer istr[], const Integer idiag[], const char *check, const ADTYPE y[], ADTYPE x[], 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

f11db is the AD Library version of the primal routine f11dbf.
f11dbf solves a system of linear equations involving the incomplete LU preconditioning matrix generated by f11daf. For further information see Section 3 in the documentation for f11dbf.

4 References

5 Arguments

In addition to the arguments present in the interface of the primal routine, f11db 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_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: trans – character Input
3: n – Integer Input
4: a(la) – ADTYPE array Input
5: la – Integer Input
6: irow(la) – Integer array Input
7: icol(la) – Integer array Input
8: ipivp(n) – Integer array Input
9: ipivq(n) – Integer array Input
10: istr(n+1) – Integer array Input
11: idiag(n) – Integer array Input
12: check – character Input
13: y(n) – ADTYPE array Input
14: x(n) – ADTYPE array Output
15: ifail – Integer Input/Output

6 Error Indicators and Warnings

f11db preserves all error codes from f11dbf 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

f11db is not threaded in any implementation.

9 Further Comments


10 Example

The following examples are variants of the example for f11dbf, modified to demonstrate calling the NAG AD Library.
Description of the primal example.
This example reads in a sparse nonsymmetric matrix A and a vector y. It then calls f11da, with lfill=−1 and dtol=0.0, to compute the complete LU decomposition
Finally it calls f11db to solve the system

10.1 Adjoint modes

Language Source File Data Results
Fortran f11db_a1w_fe.f90 f11db_a1w_fe.d f11db_a1w_fe.r
C++ f11db_a1w_hcppe.cpp f11db_a1w_hcppe.d f11db_a1w_hcppe.r

10.2 Tangent modes

Language Source File Data Results
Fortran f11db_t1w_fe.f90 f11db_t1w_fe.d f11db_t1w_fe.r
C++ f11db_t1w_hcppe.cpp f11db_t1w_hcppe.d f11db_t1w_hcppe.r

10.3 Passive mode

Language Source File Data Results
Fortran f11db_p0w_fe.f90 f11db_p0w_fe.d f11db_p0w_fe.r
C++ f11db_p0w_hcppe.cpp f11db_p0w_hcppe.d f11db_p0w_hcppe.r