tradvec_example.cpp

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//                           Sacado Package
//                 Copyright (2006) Sandia Corporation
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// Questions? Contact David M. Gay (dmgay@sandia.gov) or Eric T. Phipps
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// tradvec_example
//
//  usage:
//     tradvec_example
//
//  output:
//     prints the results of differentiating two simple functions and their
//     sum with reverse mode AD using functions Outvar_Gradcomp and
//     Weighted_GradcompVec in the Sacado::RadVec::ADvar class.
 
/* Simple test of Outvar_Gradcomp and Weighted_GradcompVec. */
 
#include "Sacado_tradvec.hpp"
#include <stdio.h>
 
#ifdef _MSC_VER
# define snprintf _snprintf
#endif
 
typedef Sacado::RadVec::ADvar<double> ADVar;
 
 ADVar
foo(double d, ADVar x, ADVar y)
{ return d*x*y; }
 
 ADVar
goo(double d, ADVar x, ADVar y)
{ return d*(x*x + y*y); }
 
 struct
ExpectedAnswer {
  const char *name;
  double v; // value of name
  double dvdx;  // partial w.r.t. x
  double dvdy;  // partial w.r.t. y
  };
 
 static ExpectedAnswer expected[4] = {
  { "a", 6., 3., 2. },
  { "b", 13., 4., 6. },
  { "c", 19., 7., 8. },
  { "(a + b + c)", 38., 14., 16. }};
 
 int
botch(ExpectedAnswer *e, const char *partial, double got, double wanted)
{
  char buf[32];
  const char *what;
 
  what = e->name;
  if (partial) {
    snprintf(buf, sizeof(buf), "d%s/d%s", what, partial);
    what = buf;
    }
  fprintf(stderr, "Expected %s = %g, but got %g\n", what, wanted, got);
  return 1;
  }
 
 int
acheck(int k, double d, double v, double dvdx, double dvdy)
{
  ExpectedAnswer *e = &expected[k];
  int nbad = 0;
 
  /* There should be no round-off error in this simple example, so we */
  /* use exact comparisons, rather than, say, relative differences. */
 
  if (v != d*e->v)
    nbad += botch(e, 0, v, d*e->v);
  if (dvdx != d*e->dvdx)
    nbad += botch(e, "x", dvdx, d*e->dvdx);
  if (dvdy != d*e->dvdy)
    nbad += botch(e, "y", dvdy, d*e->dvdy);
  return nbad;
  }
 
 int
main(void)
{
  double d, z[4];
  int i, nbad;
 
  static ADVar a, b, c, x, y, *v[3] = {&a, &b, &c};
  static ADVar **V[4] = {v, v+1, v+2, v};
  static size_t np[4] = {1, 1, 1, 3};
  static double w[3] = { 1., 1., 1. };
  static double *W[4] = {w, w, w, w};
 
  nbad = 0;
  for(d = 1.; d <= 2.; ++d) {
    printf("\nd = %g\n", d);
    x = 2;
    y = 3;
    a = foo(d,x,y);
    b = goo(d,x,y);
    c = a + b;
 
    ADVar::Outvar_Gradcomp(a);
    printf("a = %g\n", a.val());
    printf("da/dx = %g\n", x.adj());
    printf("da/dy = %g\n", y.adj());
    nbad += acheck(0, d, a.val(), x.adj(), y.adj());
    z[0] = a.val();
 
    ADVar::Outvar_Gradcomp(b);
    printf("b = %g\n", b.val());
    printf("db/dx = %g\n", x.adj());
    printf("db/dy = %g\n", y.adj());
    nbad += acheck(1, d, b.val(), x.adj(), y.adj());
    z[1] = b.val();
 
    ADVar::Outvar_Gradcomp(c);
    printf("c = %g (should be a + b)\n", c.val());
    printf("dc/dx = %g\n", x.adj());
    printf("dc/dy = %g\n", y.adj());
    nbad += acheck(2, d, c.val(), x.adj(), y.adj());
    z[2] = c.val();
    z[3] = z[0] + z[1] + z[2];
 
    ADVar::Weighted_GradcompVec(4,np,V,W);
    for(i = 0; i < 4; ++i) {
      printf("w %d:\td/dx = %g\td/dy = %g\n", i, x.adj(i), y.adj(i));
      nbad += acheck(i, d, z[i], x.adj(i), y.adj(i));
      }
    }
  if (nbad == 0)
    printf("\nExample passed!\n");
  else
    printf("\nSomething is wrong, example failed!\n");
  return nbad > 0;
  }