// Copyright (c) 2011-2013, Pacific Biosciences of California, Inc.
//
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// Author: David Alexander, and complement array from Mark Chaisson

#include <ConsensusCore/Utils.hpp>

#include <cassert>
#include <cstdlib>


union FloatInt
{
  int i;
  float f;
};


int FloatAsInt(float A)
{
  union FloatInt u;
  u.f = A;
  return u.i;
}


// Floating point comparison method from Bruce Dawson's site
// (http://www.cygnus-software.com/papers/comparingfloats/comparingfloats.htm)
bool AlmostEqual(float A, float B, int maxUlps)
{
    // Make sure maxUlps is non-negative and small enough that the
    // default NAN won't compare as equal to anything.
    assert(maxUlps > 0 && maxUlps < 4 * 1024 * 1024);
    int aInt = FloatAsInt(A);
    // Make aInt lexicographically ordered as a twos-complement int
    if (aInt < 0)
        aInt = 0x80000000 - aInt;
    // Make bInt lexicographically ordered as a twos-complement int
    int bInt = FloatAsInt(B);
    if (bInt < 0)
        bInt = 0x80000000 - bInt;
    int intDiff = abs(aInt - bInt);
    if (intDiff <= maxUlps)
        return true;
    return false;
}
