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roundToInt<float>

General JUCE discussion
#1

juce_core/maths/juce_MathsFunctions.h

 

inline int floatToUInt(float x)
{
    unsigned int e = (0x7F + 31) - ((* (unsigned int*) &x & 0x7F800000) >> 23);
    unsigned int m = 0x80000000 | (* (unsigned int*) &x << 8);
    return int((m >> e) & -(e < 32));
}

inline int roundToIntFloat(float x)
{
    // round
    if (x >= 0)
        return floatToUInt(x + 0.5f);
    return -floatToUInt(0.5f - x);
}

// specialise
template <>
inline int roundToInt<float>(const float value) noexcept
{
    return roundToIntFloat(value);
}

Been trying it in my builds, mainly to avoid unnecessary use of double.

 

#2

Isn't there juce::roundFloatToInt() that does that job already?

Edit: Though I'm not sure if the result is the same with what you did and what juce does with .5 values.

#3

So is that equivalent but faster? I vaguely remember seeing where someone had benchmarked all the float->int techniques and found that on newer CPUs it's better just to do it with a cast..

BTW got to be careful with that old "* (unsigned int*) &x" trick - it produces broken code on some compilers with optimisations enabled, so best to always use a union instead.

#4

std::trunc(), anyone?

http://en.cppreference.com/w/cpp/numeric/math/trunc

#5

[img]http://s3-eu-west-1.amazonaws.com/stvle/28b064538b6b35984f9629c7b4472ef3.png[/img]

 

#6

Blimey, I don't remember now.. I just vaguely remember changing it a while ago for some reason - I think because I read some benchmarks or something..