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/*
 * Created on 12/02/2005
 *
 * JRandTest package
 *
 * Copyright (c) 2005, Zur Aougav, [email protected]
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without modification, 
 * are permitted provided that the following conditions are met:
 * 
 * Redistributions of source code must retain the above copyright notice, this list 
 * of conditions and the following disclaimer. 
 * 
 * Redistributions in binary form must reproduce the above copyright notice, this 
 * list of conditions and the following disclaimer in the documentation and/or 
 * other materials provided with the distribution. 
 * 
 * Neither the name of the JRandTest nor the names of its contributors may be 
 * used to endorse or promote products derived from this software without specific 
 * prior written permission. 
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND 
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR 
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON 
 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package com.fasteasytrade.jrandtest.tests;

import java.util.Map;
import java.util.logging.Logger;

import com.fasteasytrade.jrandtest.utils.Format;
import com.fasteasytrade.jrandtest.utils.Stat;

/**
 * The BitStream test.
 * 
 * The file under test is viewed as a stream of bits. Call them b1,b2,... .
 * Consider an alphabet with two \"letters\", 0 and 1 and think of the
 * stream of bits as a succession of 20-letter "words", overlapping. Thus
 * the first word is b1b2...b20, the second is b2b3...b21, and so on. The
 * bitstream test counts the number of missing 20-letter (20-bit) words in
 * a string of 2^21 overlapping 20-letter words. There are 2^20 possible 20
 * letter words. For a truly random string of 2^21+19 bits, the number of
 * missing words j should be (very close to) normally distributed with mean
 * 141,909 and sigma 428. Thus (j-141909)/428 should be a standard normal
 * variate (z score) that leads to a uniform [0,1) p value. The test is
 * repeated twenty times.
 * 
 * @author Zur Aougav
 */
public class Overlapping20TuplesBitstream extends Base {

    final private Logger log = Logger.getLogger(getClass().getName());

    @Override
    public ResultStatus test(Map details) {
        final int nb_pw = 20, power = 21, no_obs = 20;
        final int no_bits = (int)Math.pow(2, power - 5);
        final int no_wds = (int)Math.pow(2, power);
        final int dim = (int)Math.pow(2, nb_pw - 5);
        int mask = (int)Math.pow(2, nb_pw) - 1;
        final double mean = Math.pow(2, nb_pw) * Math.exp(-Math.pow(2, power - nb_pw));
        final double std = 428;

        //int w20;
        long w20;
        int w32;
        int i, j, k, l, u, no_mswds = 0;
        int[] bitmask = new int[32];
        int[] wds = new int[dim];
        double z;

        /*
        for (i = 0; i < 32; ++i)
        {
        	bitmask[i] = (int)pow(2, i);
        }
        */
        bitmask[0] = 1;
        for (i = 1; i < 32; ++i) {
            bitmask[i] = bitmask[i - 1] << 1;
        }

        log.info("\t (" + nb_pw + " bits/word, " + no_wds + " words");
        log.info(" " + no_obs + " bitstreams.");
        log.info(" No. missing words \n\t  should average " + Format.d4(mean));
        log.info(" with sigma=" + Format.d4(std) + ".)\n");
        log.info("\t----------------------------------------------------------------");
        log.info("\tBitstream\tNo. missing words\tz-score\t\tp-value\n");

        rs.openInputStream();

        //w20 = uni();
        w20 = 0xffffffffL & rs.readInt();

        /*
         * main loop
         */
        for (i = 1; i <= no_obs; i++) {
            for (j = 0; j < dim; j++) {
                wds[j] = 0;
            }

            for (j = 0; j < no_bits; ++j) {
                w32 = rs.readInt();
                if (!rs.isOpen()) {
                    log.info("\nError: end of file too early... End processing.\n\n");
                    break;
                }

                for (k = 1; k <= 32; ++k) {
                    w20 <<= 1;
                    w20 += (w32 & 1);
                    w20 &= mask;
                    l = (int)(w20 & 31);
                    u = (int)(w20 >>> 5);
                    wds[u] |= bitmask[l];
                    w32 >>>= 1;
                }
            }

            if (!rs.isOpen()) {
                break;
            }

            /*
             * count no. of empty cells (=no. missing words)
             */
            no_mswds = 0;
            for (j = 0; j < dim; j++) {
                for (k = 0; k < 32; k++) {
                    if ((wds[j] & bitmask[k]) == 0) {
                        ++no_mswds;
                    }
                }
            }

            z = (no_mswds - mean) / std;
            log.info("\t   " + i + "\t\t" + no_mswds + " \t\t\t" + Format.d4(z) + "\t\t" + Format.d4(1 - Stat.Phi(z)) + "\n");
        }

        rs.closeInputStream();

        log.info("\t----------------------------------------------------------------");
        return ResultStatus.UNKNOWN;
    }
}