Re: PHP 5.4.11 tests: floating point diff

>> My understanding of floating point calculations is that -0 and 0 are >> equivalent, so I can safely ignore the failures. I wanted to first >> check to make sure that is actually true. > > > No, they are not the same thing for several purposes. For instance, they > have different serializations. See also: > > $ php > <?php $nz = fmod(-2,2); var_dump(atan2(0., $nz), atan2($nz, $nz)); > float(3.1415926535898) > float(-3.1415926535898) > > So I think you should investigate the cause of the problem (different > results), rather than ignoring the differences. Possibly the difference lies > in the Intel math library; in that case, you can either separate the tests > in two or just ignore the test when compiling with the Intel compiler. Are the rules for double-precision floats the same in this regard? I have confirmed that fmod(-2, 2) returns positive zero in icc. I have asked on their forum if there is a flag or something I can enable to fix this; it might be a bug. Note that fmodf (for floats, not doubles) correctly returns -0.