/*

* 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"  

/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

                A P P R O X I M A T E  E N T R O P Y   T E S T

 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

void

ApproximateEntropy(int m, int n)

{

	int				i, j, k, r, blockSize, seqLength, powLen, index;

	double			sum, numOfBlocks, ApEn[2], apen, chi_squared, p_value;

	unsigned int	*P;

	fprintf(stats[TEST_APEN], "\t\t\tAPPROXIMATE ENTROPY TEST\n");

	fprintf(stats[TEST_APEN], "\t\t--------------------------------------------\n");

	fprintf(stats[TEST_APEN], "\t\tCOMPUTATIONAL INFORMATION:\n");

	fprintf(stats[TEST_APEN], "\t\t--------------------------------------------\n");

	fprintf(stats[TEST_APEN], "\t\t(a) m (block length)    = %d\n", m);

	seqLength = n;

	r = 0;

	for ( blockSize=m; blockSize<=m+1; blockSize++ ) {

		if ( blockSize == 0 ) {

			ApEn[0] = 0.00;

			r++;

		}

		else {

			numOfBlocks = (double)seqLength;

			powLen = (int)pow(2, blockSize+1)-1;

			if ( (P = (unsigned int*)calloc(powLen,sizeof(unsigned int)))== NULL ) {

				fprintf(stats[TEST_APEN], "ApEn:  Insufficient memory available.\n");

				return;

			}

			for ( i=1; i<powLen-1; i++ )

				P[i] = 0;

			for ( i=0; i<numOfBlocks; i++ ) { /* COMPUTE FREQUENCY */

				k = 1;

				for ( j=0; j<blockSize; j++ ) {

					k <<= 1;

					if ( (int)epsilon[(i+j) % seqLength] == 1 )

						k++;

				}

				P[k-1]++;

			}

			/* DISPLAY FREQUENCY */

			sum = 0.0;

			index = (int)pow(2, blockSize)-1;

			for ( i=0; i<(int)pow(2, blockSize); i++ ) {

				if ( P[index] > 0 )

					sum += P[index]*log(P[index]/numOfBlocks);

				index++;

			}

			sum /= numOfBlocks;

			ApEn[r] = sum;

			r++;

			free(P);

		}

	}

	apen = ApEn[0] - ApEn[1];

	chi_squared = 2.0*seqLength*(log(2) - apen);

	p_value = cephes_igamc(pow(2, m-1), chi_squared/2.0);

	fprintf(stats[TEST_APEN], "\t\t(b) n (sequence length) = %d\n", seqLength);

	fprintf(stats[TEST_APEN], "\t\t(c) Chi^2               = %f\n", chi_squared);

	fprintf(stats[TEST_APEN], "\t\t(d) Phi(m)	       = %f\n", ApEn[0]);

	fprintf(stats[TEST_APEN], "\t\t(e) Phi(m+1)	       = %f\n", ApEn[1]);

	fprintf(stats[TEST_APEN], "\t\t(f) ApEn                = %f\n", apen);

	fprintf(stats[TEST_APEN], "\t\t(g) Log(2)              = %f\n", log(2.0));

	fprintf(stats[TEST_APEN], "\t\t--------------------------------------------\n");

	if ( m > (int)(log(seqLength)/log(2)-5) ) {

		fprintf(stats[TEST_APEN], "\t\tNote: The blockSize = %d exceeds recommended value of %d\n", m,

			MAX(1, (int)(log(seqLength)/log(2)-5)));

		fprintf(stats[TEST_APEN], "\t\tResults are inaccurate!\n");

		fprintf(stats[TEST_APEN], "\t\t--------------------------------------------\n");

	}

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

	fprintf(results[TEST_APEN], "%f\n", p_value);

}