65 lines
1.4 KiB
C
65 lines
1.4 KiB
C
|
|
/* Driver for routine orthog */
|
|
|
|
#include <stdio.h>
|
|
#include <math.h>
|
|
#define NRANSI
|
|
#include "nr.h"
|
|
#include "nrutil.h"
|
|
|
|
#define NP 64
|
|
|
|
float func(float x)
|
|
{
|
|
return 1.0/SQR(1.0+x);
|
|
}
|
|
|
|
int main(void)
|
|
{
|
|
int i,n;
|
|
float amu0,check,xx,*a,*b,*x,*w,*anu,*alpha,*beta;
|
|
|
|
a=vector(1,NP);
|
|
b=vector(1,NP);
|
|
x=vector(1,NP);
|
|
w=vector(1,NP);
|
|
anu=vector(1,2*NP);
|
|
alpha=vector(1,2*NP-1);
|
|
beta=vector(1,2*NP-1);
|
|
|
|
/* Test with w[x] = -log x */
|
|
for (;;) {
|
|
printf("Enter N\n");
|
|
if (scanf("%d",&n) == EOF) break;
|
|
alpha[1]=0.5;
|
|
beta[1]=1.0;
|
|
for (i=2;i<=2*n-1;i++) {
|
|
alpha[i]=0.5;
|
|
beta[i]=1.0/(4.0*(4.0-1.0/((i-1)*(i-1))));
|
|
}
|
|
anu[1]=1.0;
|
|
anu[2] = -0.25;
|
|
for (i=2;i<=2*n-1;i++) anu[i+1] = -anu[i]*i*(i-1)/(2.0*(i+1)*(2*i-1));
|
|
orthog(n,anu,alpha,beta,a,b);
|
|
amu0=1.0;
|
|
gaucof(n,a,b,amu0,x,w);
|
|
printf("%3s %10s %14s\n","#","x(i)","w(i)");
|
|
for (i=1;i<=n;i++) printf("%3d %14.6e %14.6e\n",i,x[i],w[i]);
|
|
for (check=0.0,i=1;i<=n;i++) check += w[i];
|
|
printf("\nCheck value: %15.7e should be: %15.7e\n",check,amu0);
|
|
/* demonstrate the use of ORTHOG for an integral */
|
|
for (xx=0.0,i=1;i<=n;i++) xx += w[i]*func(x[i]);
|
|
printf("\nIntegral from orthog: %12.6f\n",xx);
|
|
printf("Actual value: %12.6f\n",log(2.0));
|
|
}
|
|
free_vector(beta,1,2*NP-1);
|
|
free_vector(alpha,1,2*NP-1);
|
|
free_vector(anu,1,2*NP);
|
|
free_vector(w,1,NP);
|
|
free_vector(x,1,NP);
|
|
free_vector(b,1,NP);
|
|
free_vector(a,1,NP);
|
|
return 0;
|
|
}
|
|
#undef NRANSI
|