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uniform_real_distribution: fix boundary so values are really [a,b) instead of [a,b] #596

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uniform_real_distribution: fix boundary so values are really [a,b) instead of [a,b] #596

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d9af08b
Make sure a < b
jagerman Apr 24, 2016
81b826d
Use nextafter to shift result off upper bound
jagerman Apr 24, 2016
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6 changes: 5 additions & 1 deletion include/boost/compute/random/uniform_real_distribution.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -36,10 +36,12 @@ class uniform_real_distribution

/// Creates a new uniform distribution producing numbers in the range
/// [\p a, \p b).
/// Requires a < b
uniform_real_distribution(RealType a = 0.f, RealType b = 1.f)
: m_a(a),
m_b(b)
{
BOOST_ASSERT(a < b);
}

/// Destroys the uniform_real_distribution object.
Expand Down Expand Up @@ -69,7 +71,9 @@ class uniform_real_distribution
{
BOOST_COMPUTE_FUNCTION(RealType, scale_random, (const uint_ x),
{
return LO + (convert_RealType(x) / MAX_RANDOM) * (HI - LO);
// Use nextafter to shift the result slightly towards LO to avoid being able to get a
// value of exactly HI.
return nextafter(LO + (convert_RealType(x) / MAX_RANDOM) * (HI - LO), LO);
});

scale_random.define("LO", detail::make_literal(m_a));
Expand Down