/*
 * File:    ~/numerical/test_nag.c
 *
 * Author:  Chuck Gartland (6-99)
 *
 * C test program for using NAG Library on the HP-UX 10.*,
 * Linux, and SunOS 4.1 machines on the Kent Math/CS Network.
 *
 * Library locations:
 *
 *   HP-UX:       /local/opt/fortran/lib/libnag.a
 *   Linux, Sun:  /usr/local/lib/libnag.a
 *
 * Compiling alternatives:  There are several different ways
 *   to accomplish this, but I believe the easiest path
 *   is to compile the C driver (and any other C programs) separately
 *   and then invoke the linker/loader from Fortran
 *   (in order to get the proper Fortran runtime libraries and load path).
 *
 *   Note the different naming conventions in the source code below.
 *   You may need to do some commenting/uncommenting to get things to work
 *   properly on your particular platform.
 *
 *   HP-UX:  (the HP Fortran compiler will handle a C program properly)
 *   -----
 *     1) directing the loader to search extra directory
 *
 *       % fort77 test_nag.c -L/local/opt/fortran/lib -lnag
 *
 *     2) using full path name or link to the library archive
 *
 *       % f77 test_nag.c /local/opt/fortran/lib/libnag.a
 *
 *     or
 *
 *       % ln -s /local/opt/fortran/lib/libnag.a nag.a
 *       % f77 test_nag.c nag.a
 *
 *     See man pages for "f77/fort77", "ld", and "ln".
 *
 *   Linux, Sun:
 *   ----------
 *     % cc -c test_nag.c
 *     % f77 test_nag.o -lnag
 *
 *     See man pages for "cc" and "f77".
 *
 *   NOTE - In calling a Fortran sub-program from C, one must
 *          be attentive to certain language differences.
 *          In particular, Fortran stores arrays by columns
 *          ("column major" order); whereas C stores them by rows
 *          ("row major" order).  Also, Fortran passes all arguments
 *          by reference (pointer).
 *
 *          To see the difference, compare this program with
 *          the companion Fortran version "test_la.f".
 *
 *          See also the information available through "lrom"
 *          (the HP CD-ROM on-line manual browser) in
 *
 *            Series 700 10.* Manuals (B, C, & J Class)
 *              HP C Programmer's Guide
 *                Ch 5. Programming for Portability
 *                  Calling Other Languages
 *                    Calling Fortran
 *
 * Test prob: [ 1 2 3 ][x]   [ 6] ,  w/ true sol'n  [1]
 *            [ 4 5 6 ][y] = [15]                   [1]
 *            [ 7 8 0 ][z]   [15]                   [1]
 *
 */

#include <stdio.h>

double A[4][5] = { { 1., 4., 7., 0., 0. },         /* deliberately chosen    */
                   { 2., 5., 8., 0., 0. },         /* larger dimensions      */
                   { 3., 6., 0., 0., 0. },         /* to illustrate the role */
                   { 0., 0., 0., 0., 0. } } ;      /* of 'ia'                */

double b[3] = { 6., 15., 15. } ;

double wkspce[3] ;

extern void f04arf() ;                                                 /* HP */
/* extern void f04arf_() ; */                                  /* Linux, Sun */

main()                                                          /* HP, Linux */
/* MAIN_() */                                                         /* Sun */
{
  int ia = 5, n = 3, ifail = 0 ;

  /* solve Ax=b system */
  f04arf( A, &ia, b, &n, b, wkspce, &ifail ) ;                         /* HP */
  /* f04arf_( A, &ia, b, &n, b, wkspce, &ifail ) ; */          /* Linux, Sun */

  printf( " ifail = %2d \n", ifail ) ;

  printf( " b(1) = %.15e \n", b[0] ) ;
  printf( " b(2) = %.15e \n", b[1] ) ;
  printf( " b(3) = %.15e \n", b[2] ) ;
}

/*
 * Appended sample output:
 *
 * ifail =  0 
 * b(1) = 9.999999999999996e-01 
 * b(2) = 1.000000000000000e+00 
 * b(3) = 1.000000000000000e+00 
 *
 */