home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
Language/OS - Multiplatform Resource Library
/
LANGUAGE OS.iso
/
cpp_libs
/
hlvector.lha
/
hl_vector
/
vali.cc
< prev
next >
Wrap
C/C++ Source or Header
|
1993-08-08
|
5KB
|
203 lines
// This may look like C code, but it is really -*- C++ -*-
//
// Verification of the Aitken-Lagrange Interpolation
//
#include "LinAlg.h"
#include "math_num.h"
#include <ostream.h>
/*
*------------------------------------------------------------------------
* Set of the test functions to interpolate
*/
static double (*F)(const double x);
static double f_exp(const double x)
{
return exp(-x);
}
static double f_sinexp(const double x)
{
return sin(x) * exp(-x/10);
}
/*
*------------------------------------------------------------------------
* Set of tests for the interpolation over the uniform grid
*/
// Verify that interpolation exactly at a node
// really gives the function value at the node
static void test_u_exact(const double s, const int ia, const int ib)
{
cout << "\nCheck to see that interpolation at a node gives an exact"
" result\n";
cout << "\nUniform grid " << form("[%g:%g] with the step %g",s*ia,s*ib,s);
Vector y(ia,ib);
Vector y_int(ia,ib);
register int i;
for(i=y.q_lwb(); i<=y.q_upb(); i++)
y(i) = (*F)(s*i);
for(i=y_int.q_lwb(); i<=y_int.q_upb(); i++)
y_int(i) = ali(s*i,s*ia,s,y);
assert(y == y_int);
cout << "\nDone\n";
}
// Check the precision for interpolation
// at arbitrary points
static void test_u(const double s, const int ia, const int ib)
{
cout << "\nCheck the precision of the interpolation at arbitrary points\n";
cout << "\nUniform grid " << form("[%g:%g] with the step %g",s*ia,s*ib,s);
Vector y(ia,ib);
register int i;
for(i=y.q_lwb(); i<=y.q_upb(); i++)
y(i) = (*F)(s*i);
cout << "\nPoint Exact function value Interpolated Error\n";
register double q;
for(q=(ia-1)*s; q < (ib+2)*s; q += 1.1*s)
{
double yexact = (*F)(q);
double yint = ali(q,ia*s,s,y);
cout << form("%4.2g\t%12.6g\t\t%12.6g %12.6g\n",q,yexact,yint,
abs(yexact-yint));
}
cout << "\nDone\n";
}
/*
*------------------------------------------------------------------------
* Set of tests for the interpolation over the non-uniform grid
*/
// Verify that interpolation exactly at a node
// really gives the function value at the node
static void test_n_exact(const Vector& x)
{
cout << "\nCheck to see that interpolation at a node gives an exact"
" result\n";
Vector y(x);
Vector y_int(x);
register int i;
for(i=y.q_lwb(); i<=y.q_upb(); i++)
y(i) = (*F)(x(i));
for(i=y_int.q_lwb(); i<=y_int.q_upb(); i++)
y_int(i) = ali(x(i),x,y);
assert(y == y_int);
cout << "\nDone\n";
}
// Check the precision for interpolation
// at arbitrary points
static void test_n(const Vector& x,const double s, const int ia, const int ib)
{
cout << "\nCheck the precision of the interpolation at arbitrary points\n";
Vector y(x);
register int i;
for(i=y.q_lwb(); i<=y.q_upb(); i++)
y(i) = (*F)(x(i));
cout << "\nPoint Exact function value Interpolated Error\n";
register double q;
for(q=ia*s; q < ib*s; q += s)
{
double yexact = (*F)(q);
double yint = ali(q,x,y);
cout << form("%4.2g\t%12.6g\t\t%12.6g %12.6g\n",q,yexact,yint,
abs(yexact-yint));
}
cout << "\nDone\n";
}
// Check the precision for interpolation
// on example in the book
static void test_n_book(void)
{
cout << "\nCheck the precision of the interpolation at arbitrary points\n";
cout << "\nExample from Fig. 4.11 of the book"
"\n\tNumerical Methods and Software,"
"\n\tby D.Kahaner, C.Moler, and S.Nash - Prentice Hall, 1989\n";
REAL xy[2][11] =
{ {0, 2, 3, 5, 6, 8, 9, 11, 12, 14, 15}, // abscissae
{10, 10, 10, 10, 10, 10, 10.5, 15, 50, 60, 85} // ordinates
};
Vector x(0,sizeof(xy[0])/sizeof(xy[0][0])-1);
Vector y(x);
register int i;
for(i=0; i<sizeof(xy[0])/sizeof(xy[0][0]); i++)
x(i) = xy[0][i], y(i) = xy[1][i];
cout << "\n\t\tInterpolation nots";
cout << "\nx ";
for(i=x.q_lwb(); i<=x.q_upb(); i++)
cout << form("%6.2g ",x(i));
cout << "\ny ";
for(i=y.q_lwb(); i<=y.q_upb(); i++)
cout << form("%6.2g ",y(i));
cout << "\n\nPoint Interpolated value\n";
register double q;
for(q=0; q <= 16; q += 16/50.)
cout << form("%7.4g %12.6g\n",q,ali(q,x,y));
cout << "\nDone\n";
}
/*
*------------------------------------------------------------------------
* Root module
*/
main()
{
cout << "\n\n\t\tVerification of the Aitken-Lagrange interpolation\n";
cout << "\n------------- Interpolation over the table with uniform grid";
cout << "\nFunction to interpolate: exp(-x)\n";
F = f_exp;
const double s = 0.1;
test_u_exact(s,1,10);
test_u(s,1,10);
printf("\n------------- Interpolation over the table with non-uniform grid");
printf("\nFunction to interpolate: sin(x) * exp(-x/10)\n");
F = f_sinexp;
register int i;
Vector nodes(2,51);
for(i=nodes.q_lwb(); i<=11; i++)
nodes(i) = (i-1.)/10;
for(i=12; i<=nodes.q_upb(); i++)
nodes(i) = (i-6.)/5;
cout << "\nGrids 0.1 .. 1 have the mesh 0.1, and 1..9 have the mesh 0.2\n";
test_n_exact(nodes);
test_n(nodes,0.27,0,15);
test_n_book();
}