#!/bin/sh
#
#  check-zzuf-r-ratio - zzuf RNG statistic tests
#
#  Copyright © 2002—2015 Sam Hocevar <sam@hocevar.net>
#
#  This program is free software. It comes without any warranty, to
#  the extent permitted by applicable law. You can redistribute it
#  and/or modify it under the terms of the Do What the Fuck You Want
#  to Public License, Version 2, as published by the WTFPL Task Force.
#  See http://www.wtfpl.net/ for more details.
#

. "$(dirname "$0")/functions.inc"

checkflip()
{
    r=$1
    expect=$2
    mib=20
    try=3
    s2=$seed
    new_test "$mib MiB of zeroes, ratio $r"
    echo " expecting $expect"
    checkflip_internal $1 $2 $mib $try $s2
}

checkflip_internal()
{
    r=$1
    expect=$2
    mib=$3
    try=$4
    s2=$5
    rmax=-1
    rmin=-1
    rtot=0
    printf " got"
    for x in 0 1 2 3 4; do
        ret=`dd if=/dev/zero bs=1048576 count=$mib 2>/dev/null | $ZZUF -s $s2 -r $r | "$ZZERO"`
        if [ "$rmax" = -1 -o "$ret" -gt "$rmax" ]; then rmax=$ret; fi
        if [ "$rmin" = -1 -o "$ret" -lt "$rmin" ]; then rmin=$ret; fi
        rtot=`expr $rtot + $ret || true`
        printf " $ret"
        s2=`expr $s2 + 1`
    done
    echo ""
    rmean=`expr '(' $rtot + 2 ')' / 5 || true`
    delta=`expr $rmean - $expect || true`
    printf " min/avg/max $rmin/$rmean/$rmax .........."
    if [ "$delta" -gt -5 -a "$delta" -lt 5 ]; then
        pass_test " ok"
    elif [ $(($rmean * 8)) -lt $(($expect * 7)) \
               -o $(($rmean * 7)) -gt $(($expect * 8)) ]; then
        if [ $try -gt 0 ]; then
            # Hack: if we failed with that seed, just try another one.
            # Kinda defeats the purpose of the test, but well, that's
            # how randomness works, you cannot win each time.
            echo " trying again"
            checkflip_internal $1 $2 $3 $(($3 - 1)) "$3$s2"
        else
            fail_test " FAILED"
        fi
    else
        pass_test " ok"
    fi
}

start_test "zzuf -r test"

# if X flips are performed on N bits set to 0, the average number of bits
# set to 1 is: N / 2 * (1 - pow(1 - 2 / N, X)
checkflip 0.000000001 0
checkflip 0.00000001  1
checkflip 0.0000001  16
checkflip 0.000001  167
checkflip 0.00001  1677
checkflip 0.0001  16775
checkflip 0.001  167604
checkflip 0.01  1661055
checkflip 0.1  15205967

stop_test