From: Johan Råde (rade_at_[hidden])
Date: 2006-10-05 07:42:33
I have put together optimized implementations
of the following functions:
template<class T> int fpclassify(T x);
template<class T> bool isfinite(T x);
template<class T> bool isinf(T x);
template<class T> bool isnan(T x);
template<class T> bool isnormal(T x);
template<class T> bool signbit(T x);
template<class T> T copysign(T x, T y);
template<class T> T changesign(T x);
Here T is required to be float, double or long double.
--------------------
The code has been tested with
Windows / VC7.1 / i386
Mac / GCC 4.0 / powerpc
Linux / GCC 3.3 / i386, amd64, ia64, powerpc, mips, hppa
The code should work with most platforms
that support the IEEE754 standard.
--------------------
Many of these functions have also been
implemented by John Maddock.
The difference is that my implementation
is optimized for speed.
Here are some timing numbers on VC 7.1:
float Råde Maddock Native
fpclassify 8 57 -
isfinite 5 57 -
isnormal 6 59 -
isinf 5 57 -
isnan 6 57 -
double Råde Maddock Native
fpclassify 13 52 29
isfinite 11 56 17
isnormal 14 56 -
isinf 10 52 -
isnan 4 52 19
The times are in clock cycles for a single call,
based on an average of 10,000,000 calls
with random input.
--------------------
The code is available in the vault,
at "Home/Math - Numerics/fpclassify.zip".
Many thanks to Håkan Ardö who tested the code on Linux
and Olivier Verdie who tested the code on Mac.
--Johan Råde