[Rd] Hyperbolic tangent different results on Windows and Mac
Jeroen Ooms
jeroenooms at gmail.com
Wed Mar 22 14:12:18 CET 2017
This looks like a bug in mingw-w64 CRT. The problem can be produced
with C++ without R:
#include <iostream>
#include <cmath>
#include <complex>
int main(){
std::cout << std::fixed;
std::complex<double> z(356, 0);
std::cout << "tanh" << z << " = " << std::tanh(z)
<< " (tanh(356) = " << std::tanh(356) << ")\n";
}
On OS-X we get:
tanh(356.000000,0.000000) = (1.000000,-0.000000) (tanh(356) = 1.000000)
But on Windows we get:
tanh(356.000000,0.000000) = (nan,0.000000) (tanh(356) = 1.000000)
I was also able to reproduce the problem with gcc 6.3 in msys2 so it
has not been fixed upstream. You should file a bug report for
mingw-w64.
FWIF, we have run into NaN edge-case bugs before with mingw-w64.
- https://sourceforge.net/p/mingw-w64/mingw-w64/ci/6617ebd5fc6b790c80071d5b1d950e737fc670e1/
- https://github.com/wch/r-source/commit/e9aaf8fdeddf27c2a9078cd214a41475c8ff6f40
I am cc'ing Ray Donnelly who is an expert on mingw-w64.
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