xfourfs.c

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/* Driver for routine fourfs */

#include <stdio.h>
#include <math.h>
#define NRANSI
#include "nr.h"
#include "nrutil.h"

#define SWAP(a,b) {iswap=(a);(a)=(b);(b)=iswap;}
#define FSWAP(a,b) {flswap=(a);(a)=(b);(b)=flswap;}

#define NX 8
#define NY 32
#define NZ 4
#define NDAT (2*NX*NY*NZ)

#define TEMPFILE1 "frfstmp1"
#define TEMPFILE2 "frfstmp2"
#define TEMPFILE3 "frfstmp3"
#define TEMPFILE4 "frfstmp4"

#if defined(MSDOS) || defined(_MSDOS) || defined(_MSDOS_) || defined(__MSDOS__)
#define BINREADWRITE "wb+"
#else
#define BINREADWRITE "w+"
#endif

char *fnames[4]={TEMPFILE1,TEMPFILE2,TEMPFILE3,TEMPFILE4};

int main(void)
{
	int cc,nnv=3,nwrite;
	long idum=(-23);
	unsigned long dim[4],i,j,k,l,ll,iswap;
	float diff,smax,sum,sum1=0.0,sum2=0.0,tot,*data1,*data2,*data1p,*data2p;
	FILE *flswap,*file[5];

	data1=vector(1,NDAT);
	data2=vector(1,NDAT);
	dim[1]=NX;
	dim[2]=NY;
	dim[3]=NZ;
	tot=(float)NX*(float)NY*(float)NZ;
	for (j=1;j<=4;j++)
		if ((file[j]=fopen(fnames[j-1],BINREADWRITE)) == NULL)
			nrerror("Couldn't open temporary file");
	for (i=1;i<=dim[3];i++)
		for (j=1;j<=dim[2];j++)
			for (k=1;k<=dim[1];k++) {
				l=k+(j-1)*dim[1]+(i-1)*dim[2]*dim[1];
				l=(l<<1)-1;
				data2[l]=data1[l]=2*ran1(&idum)-1;
				l++;
				data2[l]=data1[l]=2*ran1(&idum)-1;
			}
	nwrite=NDAT >> 1;
	cc=fwrite(&data1[1],sizeof(float),nwrite,file[1]);
	if (cc != nwrite) nrerror("write error in xfourfs");
	cc=fwrite(&data1[nwrite+1],sizeof(float),nwrite,file[2]);
	if (cc != nwrite) nrerror("write error in xfourfs");
	rewind(file[1]);
	rewind(file[2]);
	printf("**************** now doing fourfs *********\n");
	fourfs(file,dim,nnv,1);
	for (j=1;j<=4;j++) rewind(file[j]);
	cc=fread(&data1[1],sizeof(float),nwrite,file[3]);
	if (cc != nwrite) nrerror("read error in xfourfs");
	cc=fread(&data1[nwrite+1],sizeof(float),nwrite,file[4]);
	if (cc != nwrite) nrerror("read error in xfourfs");
	printf("**************** now doing fourn *********\n");
	fourn(data2,dim,nnv,1);
	sum=smax=0.0;
	for (i=1;i<=dim[3];i++)
		for (j=1;j<=dim[2];j++)
			for (k=1;k<=dim[1];k++) {
				l=k+(j-1)*dim[1]+(i-1)*dim[2]*dim[1];
				l=(l<<1)-1;
				ll=i+(j-1)*dim[3]+(k-1)*dim[3]*dim[2];
				ll=(ll<<1)-1;
				diff=sqrt(SQR(data2[ll]-data1[l])+SQR(data2[ll+1]-data1[l+1]));
				sum2 += SQR(data1[l])+SQR(data1[l+1]);
				sum += diff;
				if (diff > smax) smax=diff;
			}
	sum2=sqrt(sum2/tot);
	sum=sum/tot;
	printf("(r.m.s.) value, (max,ave) discrepancy= %12.7f %12.7f %12.7f\n",
		sum2,smax,sum);
	/* now check the inverse transforms */
	SWAP(dim[1],dim[3]);
	/* This step swap step is conceptually a reversal, but for
	three dimensions a swap accomplishes that. */
	FSWAP(file[1],file[3])
	FSWAP(file[4],file[2])
	for (j=1;j<=4;j++) rewind(file[j]);
	printf("**************** now doing fourfs *********\n");
	fourfs(file,dim,nnv,-1);
	for (j=1;j<=4;j++) rewind(file[j]);
	cc=fread(&data1[1],sizeof(float),nwrite,file[3]);
	if (cc != nwrite) nrerror("read error in xfourfs");
	cc=fread(&data1[nwrite+1],sizeof(float),nwrite,file[4]);
	if (cc != nwrite) nrerror("read error in xfourfs");
	SWAP(dim[1],dim[3]);
	printf("**************** now doing fourn *********\n");
	fourn(data2,dim,nnv,-1);
	sum=smax=0.0;
	data1p=data1;
	data2p=data2;
	for (j=1;j<=NDAT;j+=2) {
		sum1 += SQR(data2p[1])+SQR(data2p[2]);
		diff=sqrt(SQR(data2p[1]-data1p[1])+SQR(data2p[2]-data1p[2]));
		sum += diff;
		if (diff > smax) smax=diff;
		data1p += 2;
		data2p += 2;
	}
	sum=sum/tot;
	sum1=sqrt(sum1/tot);
	printf("(r.m.s.) value, (max,ave) discrepancy= %12.7f %12.7f %12.7f\n",
		sum1,smax,sum);
	printf("ratio of r.m.s. values, expected ratio= %12.6f %12.6f\n",
		sum1/sum2,sqrt(tot));
	for (j=1;j<=4;j++)
		if (fclose(file[j]) == EOF) nrerror("Couldn't close temporary file");
	free_vector(data2,1,NDAT);
	free_vector(data1,1,NDAT);
	for (j=1;j<=4;j++)
		if (remove(fnames[j-1])) nrerror("Couldn't delete temporary file");
	return 0;
}
#undef NRANSI