add numerical recipes library

lib/nr/ansi/examples/xfourn.c

@@ -0,0 +1,58 @@
+
+/* Driver for routine fourn */
+
+#include <stdio.h>
+#define NRANSI
+#include "nr.h"
+#include "nrutil.h"
+
+#define NDIM 3
+#define NDAT2 1024
+
+int main(void)
+{
+	int isign;
+	long idum=(-23);
+	unsigned long i,j,k,l,ndum=2,*nn;
+	float *data1,*data2;
+
+	nn=lvector(1,NDIM);
+	data1=vector(1,NDAT2);
+	data2=vector(1,NDAT2);
+	for (i=1;i<=NDIM;i++) nn[i]=(ndum <<= 1);
+	for (i=1;i<=nn[3];i++)
+		for (j=1;j<=nn[2];j++)
+			for (k=1;k<=nn[1];k++) {
+				l=k+(j-1)*nn[1]+(i-1)*nn[2]*nn[1];
+				l=(l<<1)-1;
+				/* real part of component */
+				data2[l]=data1[l]=2*ran1(&idum)-1;
+				/* imaginary part of component */
+				l++;
+				data2[l]=data1[l]=2*ran1(&idum)-1;
+			}
+	isign=1;
+	fourn(data2,nn,NDIM,isign);
+	/* here would be any processing to be done in Fourier space */
+	isign = -1;
+	fourn(data2,nn,NDIM,isign);
+	printf("Double 3-dimensional transform\n\n");
+	printf("%22s %24s %20s\n",
+		"Double transf.","Original data","Ratio");
+	printf("%10s %13s %12s %13s %11s %13s\n\n",
+		"real","imag.","real","imag.","real","imag.");
+	for (i=1;i<=4;i++) {
+		k=2*(j=2*i);
+		l=k+(j-1)*nn[1]+(i-1)*nn[2]*nn[1];
+		l=(l<<1)-1;
+		printf("%12.2f %12.2f %10.2f %12.2f %14.2f %12.2f\n",
+			data2[l],data2[l+1],data1[l],data1[l+1],
+			data2[l]/data1[l],data2[l+1]/data1[l+1]);
+	}
+	printf("\nThe product of transform lengths is: %4lu\n",nn[1]*nn[2]*nn[3]);
+	free_vector(data2,1,NDAT2);
+	free_vector(data1,1,NDAT2);
+	free_lvector(nn,1,NDIM);
+	return 0;
+}
+#undef NRANSI