[Octave-bug-tracker] [bug #59149] [octave forge] (signal) Resampling from 22050 to 48000 Hz introduces strange and unexpected artifacts

[anonymous]

Follow-up Comment #29, bug #59149 (project octave):

It turns out that this problem is completely independent of Octave.

Here's a very small test that shows the effect of -ffast-math.


#include <iostream>

int main()
{
        double a = 1.0, b = (a + 1e-3) - 1e-3;
        if (a==b)
                std::cout << "Equal\n";
        else
                std::cout << "Unequal\n";
}


With -ffast-math they're equal. Without it they're unequal.

The use of == with floating point is unwise, but somehow -ffast-math makes the
intended logic work properly.

The quick workaround that a user can do to get usable results is to use
-ffast-math when building packages that use == on doubles. The better fix for
the package is to change "a==b" with "abs(a-b) <= 1e-4" or a similar
tolerance, which will then work without -ffast-math.

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