/*
* Portions Copyright (c) 2009 Nokia Corporation and/or its subsidiary(-ies).
* All rights reserved.
* This component and the accompanying materials are made available
* under the terms of "Eclipse Public License v1.0"
* which accompanies this distribution, and is available
* at the URL "http://www.eclipse.org/legal/epl-v10.html".
*
* Initial Contributors:
* Nokia Corporation - initial contribution.
*
* Contributors:
*
* Description: 
* The original NIST Statistical Test Suite code is placed in public domain.
* (http://csrc.nist.gov/groups/ST/toolkit/rng/documentation_software.html) 
* 
* This software was developed at the National Institute of Standards and Technology by 
* employees of the Federal Government in the course of their official duties. Pursuant
* to title 17 Section 105 of the United States Code this software is not subject to 
* copyright protection and is in the public domain. The NIST Statistical Test Suite is
* an experimental system. NIST assumes no responsibility whatsoever for its use by other 
* parties, and makes no guarantees, expressed or implied, about its quality, reliability, 
* or any other characteristic. We would appreciate acknowledgment if the software is used.
*/

#include "openc.h"
#include "../include/externs.h"
#include "../include/utilities.h"
#include "../include/cephes.h"

/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
         D I S C R E T E  F O U R I E R  T R A N S F O R M  T E S T 
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
void  __ogg_fdrffti(int n, double* wsave, int* ifac);
void  __ogg_fdrfftf(int n, double* X, double* wsave, int* ifac);

void
DiscreteFourierTransform(int n)
{
	double     p_value, upperBound, percentile, N_l, N_o, d;
	double*    m = NULL;
	double*    X = NULL;
	double*    wsave = NULL;
	int*       ifac = NULL;
	int		i, count;
	
	if ( ((X = (double*) calloc(n,sizeof(double))) == NULL) ||
		 ((wsave = (double *)calloc(2*n+15,sizeof(double))) == NULL) ||
		 ((ifac = (int *)calloc(15,sizeof(int))) == NULL) ||
		 ((m = (double*)calloc(n/2+1, sizeof(double))) == NULL) ) {
			fprintf(stats[7],"\t\tUnable to allocate working arrays for the DFT.\n");
			if( X != NULL )
				free(X);
			if( wsave != NULL )
				free(wsave);
			if( ifac != NULL )
				free(ifac);
			if( m != NULL )
				free(m);
			return;
	}
	for ( i=0; i<n; i++ )
		X[i] = 2*(int)epsilon[i] - 1;
	
	__ogg_fdrffti(n, wsave, ifac);		/* INITIALIZE WORK ARRAYS */
	__ogg_fdrfftf(n, X, wsave, ifac);	/* APPLY FORWARD FFT */
	
	m[0] = sqrt(X[0]*X[0]);	    /* COMPUTE MAGNITUDE */
	
	for ( i=0; i<n/2; i++ ) {	   	    /* DISPLAY FOURIER POINTS */
		m[i+1] = sqrt(pow(X[2*i+1],2)+pow(X[2*i+2],2)); 
	}
	count = 0;				       /* CONFIDENCE INTERVAL */
	upperBound = sqrt(2.995732274*n);
	for ( i=0; i<n/2; i++ )
		if ( m[i] < upperBound )
			count++;
	percentile = (double)count/(n/2)*100;
	N_l = (double) count;       /* number of peaks less than h = sqrt(3*n) */
	N_o = (double) 0.95*n/2.0;
	d = (N_l - N_o)/sqrt(n/2.0*0.95*0.05);
	p_value = erfc(fabs(d)/sqrt(2.0));

	fprintf(stats[TEST_FFT], "\t\t\t\tFFT TEST\n");
	fprintf(stats[TEST_FFT], "\t\t-------------------------------------------\n");
	fprintf(stats[TEST_FFT], "\t\tCOMPUTATIONAL INFORMATION:\n");
	fprintf(stats[TEST_FFT], "\t\t-------------------------------------------\n");
	fprintf(stats[TEST_FFT], "\t\t(a) Percentile = %f\n", percentile);
	fprintf(stats[TEST_FFT], "\t\t(b) N_l        = %f\n", N_l);
	fprintf(stats[TEST_FFT], "\t\t(c) N_o        = %f\n", N_o);
	fprintf(stats[TEST_FFT], "\t\t(d) d          = %f\n", d);
	fprintf(stats[TEST_FFT], "\t\t-------------------------------------------\n");

	fprintf(stats[TEST_FFT], "%s\t\tp_value = %f\n\n", p_value < ALPHA ? "FAILURE" : "SUCCESS", p_value);
	fprintf(results[TEST_FFT], "%f\n", p_value);

	free(X);
	free(wsave);
	free(ifac);
	free(m);
}