Re: [boost] Optimized portable isnan, isfinite, fpclassify etc

6 Oct 2006

      Johan Råde wrote:
...
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:
...
The times are in clock cycles for a single call,
based on an average of 10,000,000 calls
with random input.
I think the timings for my latest code should be a bit better than that as 
I've started forwarding to native versions where applicable.

Even so, I think this is a good idea and worth persuing.  Unfortunately I 
don't think your code is as portable as you think it is: I'm attaching below 
some failed test runs of your code with Intel (Win32 and Linux), HP aCC and 
g++ (HP-UX).  The difficulty is that once you crank up the optimisation 
levels, code like this tends to break, and since it's reason-for-existance 
is to improve performance, that's a problem :-(

I have some specific comments on the code:

1) I'm a bit uneasy about the #undef's of the std macros: let's say a user 
includes this header indirectly (because it's used by another Boost header, 
say my math stuff), they might be a bit miffed if the the macros they were 
expecting to be defined have been undef'ed like this.

2) I'm a little surprised at seeing memcpy used to shift 4 bytes, given the 
slightly-hairy nature of what you're doing here, I don't think a 
reinterpret_cast to uint32 is unreasonable in comparison.  But that's just 
my opinion :-)

3) With respect to the #error Unknown endianness, perhaps we can forward to 
a slower-but safer alternative in this case?

4) I'm fairly sure the declarations:

template<> const boost::uint32_t mask<float>::exponent  = 0x7f800000;
template<> const boost::uint32_t mask<double>::exponent = 0x7ff00000;
template<> const boost::uint32_t mask<long double>::exponent

will cause ODR violations / linker errors when the header is used from 
multiple TU's.

5) isinf needs to handle the situation where T doesn't have infinities, or 
perhaps even doesn't have / can't have numeric_limits support (NTL::RR for 
example).

6) Does the implementaton of isnan:

template<class T> bool isnan(T x)
{
    return !(x <= std::numeric_limits<T>::infinity());
}

work for negative NaN's ?  I'm thinking of compilers that perform 
non-standard-IEEE comparisons using faster comparisons of bit-patterns 
rather than fully-unordered NaN's.

OK where does this leave us.

Looks like the way forward might be some kind of merger of our 
implementations: using the slow-but-safe version as a fallback for where the 
fast-and-hairy-version doesn't work?

The difficulty is doing it without the code turning into a spagetty of #if 
logic.

I wonder if something like:

template <class T>
T isnan(T x)
{
   return isnan_imp(x, typename classify_traits<T>::type());
}

where classify_traits<T>::type is some kind of type that encapsulates:

Endianness.
Is it a real float.
Does it have numeric limits support.
Any compiler specific information - like "use fast if possible", or "always 
use safe version".

The we could use compile time dispatch to the right implementation, and all 
the hairy logic and #if code would be isolated to classify_traits (or 
whatever it's called).

Does this sound plausible, and/or something you might be interested in 
persuing?

Thanks,

John.

ps heres the failure logs:

Intel 9.1, Win32, VC-8 mode:

$ icl /O2  /EHs  -I../../../develop/boost test.cpp
Intel(R) C++ Compiler for 32-bit applications, Version 9.1    Build 
20060519Z
Copyright (C) 1985-2006 Intel Corporation.  All rights reserved.
30 DAY EVALUATION LICENSE

-out:test.exe
test.obj

John Maddock@fuji /cygdrive/c/data/boost/fpclassify/fpclassify/test
$ ./test
little endian
sizeof(long double) = 8
mask<long double>::exponent = 7ff00000

Failed test isnan(x)
Failed test fpclassify(x) == FP_NAN
Failed test isnan(x)
Failed test fpclassify(x) == FP_NAN
Failed test isnan(x)
Failed test fpclassify(x) == FP_NAN
Failed test isnan(x)
Failed test fpclassify(x) == FP_NAN
Failed test !isinf(x)
Failed test isnan(x)
Failed test fpclassify(x) == FP_NAN
Failed test isnan(x)
Failed test fpclassify(x) == FP_NAN
Failed test !isinf(x)
Failed test isnan(x)
Failed test fpclassify(x) == FP_NAN
Failed test isnan(x)
Failed test fpclassify(x) == FP_NAN
Failed test !isinf(x)
Failed test isnan(x)
Failed test fpclassify(x) == FP_NAN
Failed test isnan(x)
Failed test fpclassify(x) == FP_NAN
Failed test !isinf(x)
Failed test isnan(x)
Failed test fpclassify(x) == FP_NAN
Failed test isnan(x)
Failed test fpclassify(x) == FP_NAN
Failed test isnan(changesign(c))
Failed test isnan(changesign(changesign(c)))
Failed test isnan(changesign(c))
Failed test isnan(changesign(changesign(c)))
Failed test isnan(changesign(c))
Failed test isnan(changesign(changesign(c)))

HP aCC, HP-UX, Itanium:

aCC -AA -O3 -I ~ *.cpp
maddock@td176> ./a.out
little endian
sizeof(long double) = 16
mask<long double>::exponent = 0

Failed test fpclassify(x) == FP_ZERO
Failed test signbit(x)
Failed test isnormal(x)
Failed test fpclassify(x) == FP_NORMAL
Failed test signbit(x)
Failed test isnormal(x)
Failed test fpclassify(x) == FP_NORMAL
Failed test isnormal(x)
Failed test fpclassify(x) == FP_NORMAL
Failed test signbit(x)
Failed test isnormal(x)
Failed test fpclassify(x) == FP_NORMAL
Failed test !signbit(x)
Failed test isfinite(x)
Failed test isnormal(x)
Failed test fpclassify(x) == FP_NORMAL
Failed test isfinite(x)
Failed test isnormal(x)
Failed test fpclassify(x) == FP_NORMAL
Failed test !isfinite(x)
Failed test fpclassify(x) == FP_INFINITE
Failed test signbit(x)
Failed test !isfinite(x)
Failed test fpclassify(x) == FP_INFINITE
Failed test !isfinite(x)
Failed test fpclassify(x) == FP_NAN
Failed test !isfinite(x)
Failed test fpclassify(x) == FP_NAN
Failed test !isfinite(x)
Failed test fpclassify(x) == FP_NAN
Failed test !isfinite(x)
Failed test fpclassify(x) == FP_NAN
Failed test isfinite(x)
Failed test isfinite(x)
Failed test fpclassify(x) == FP_ZERO
Failed test isfinite(x)
Failed test signbit(x)
Failed test isfinite(x)
Failed test isfinite(x)
Failed test isnormal(x)
Failed test fpclassify(x) == FP_NORMAL
Failed test signbit(x)
Failed test isfinite(x)
Failed test isnormal(x)
Failed test fpclassify(x) == FP_NORMAL
Failed test isfinite(x)
Failed test isnormal(x)
Failed test fpclassify(x) == FP_NORMAL
Failed test signbit(x)
Failed test isfinite(x)
Failed test isnormal(x)
Failed test fpclassify(x) == FP_NORMAL
Failed test !signbit(x)
Failed test isfinite(x)
Failed test isnormal(x)
Failed test fpclassify(x) == FP_NORMAL
Failed test isfinite(x)
Failed test isnormal(x)
Failed test fpclassify(x) == FP_NORMAL
Failed test fpclassify(x) == FP_INFINITE
Failed test signbit(x)
Failed test fpclassify(x) == FP_INFINITE
Failed test fpclassify(x) == FP_NAN
Failed test fpclassify(x) == FP_NAN
Failed test fpclassify(x) == FP_NAN
Failed test fpclassify(x) == FP_NAN
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test changesign(a[i]) == -a[i]
Failed test changesign(-a[i]) == a[i]
Failed test !signbit(changesign(-a[i]))
Failed test changesign(a[i]) == -a[i]
Failed test changesign(-a[i]) == a[i]
Failed test !signbit(changesign(-a[i]))
Failed test changesign(a[i]) == -a[i]
Failed test changesign(-a[i]) == a[i]
Failed test !signbit(changesign(-a[i]))
Failed test changesign(a[i]) == -a[i]
Failed test changesign(-a[i]) == a[i]
Failed test !signbit(changesign(-a[i]))
Failed test changesign(b) == b
Failed test changesign(a[i]) == -a[i]
Failed test changesign(-a[i]) == a[i]
Failed test !signbit(changesign(-a[i]))
Failed test changesign(a[i]) == -a[i]
Failed test changesign(-a[i]) == a[i]
Failed test !signbit(changesign(-a[i]))
Failed test changesign(a[i]) == -a[i]
Failed test changesign(-a[i]) == a[i]
Failed test !signbit(changesign(-a[i]))
Failed test changesign(a[i]) == -a[i]
Failed test changesign(-a[i]) == a[i]
Failed test !signbit(changesign(-a[i]))
Failed test changesign(b) == b

G++, HP-UX, Itanium:

maddock@td176> g++
g++: no input files
maddock@td176> g++ -I ~ -O3 *.cpp
maddock@td176> ./a.out
little endian
sizeof(long double) = 16
mask<long double>::exponent = 0

Failed test fpclassify(x) == FP_ZERO
Failed test signbit(x)
Failed test isnormal(x)
Failed test fpclassify(x) == FP_NORMAL
Failed test signbit(x)
Failed test isnormal(x)
Failed test fpclassify(x) == FP_NORMAL
Failed test isnormal(x)
Failed test fpclassify(x) == FP_NORMAL
Failed test signbit(x)
Failed test isnormal(x)
Failed test fpclassify(x) == FP_NORMAL
Failed test !signbit(x)
Failed test isfinite(x)
Failed test isnormal(x)
Failed test fpclassify(x) == FP_NORMAL
Failed test isfinite(x)
Failed test isnormal(x)
Failed test fpclassify(x) == FP_NORMAL
Failed test !isfinite(x)
Failed test fpclassify(x) == FP_INFINITE
Failed test signbit(x)
Failed test !isfinite(x)
Failed test fpclassify(x) == FP_INFINITE
Failed test !isfinite(x)
Failed test fpclassify(x) == FP_NAN
Failed test !isfinite(x)
Failed test fpclassify(x) == FP_NAN
Failed test !isfinite(x)
Failed test fpclassify(x) == FP_NAN
Failed test !isfinite(x)
Failed test fpclassify(x) == FP_NAN
Failed test isfinite(x)
Failed test isfinite(x)
Failed test fpclassify(x) == FP_ZERO
Failed test isfinite(x)
Failed test signbit(x)
Failed test isfinite(x)
Failed test isfinite(x)
Failed test isnormal(x)
Failed test fpclassify(x) == FP_NORMAL
Failed test signbit(x)
Failed test isfinite(x)
Failed test isnormal(x)
Failed test fpclassify(x) == FP_NORMAL
Failed test isfinite(x)
Failed test isnormal(x)
Failed test fpclassify(x) == FP_NORMAL
Failed test signbit(x)
Failed test isfinite(x)
Failed test isnormal(x)
Failed test fpclassify(x) == FP_NORMAL
Failed test !signbit(x)
Failed test isfinite(x)
Failed test isnormal(x)
Failed test fpclassify(x) == FP_NORMAL
Failed test isfinite(x)
Failed test isnormal(x)
Failed test fpclassify(x) == FP_NORMAL
Failed test fpclassify(x) == FP_INFINITE
Failed test signbit(x)
Failed test fpclassify(x) == FP_INFINITE
Failed test fpclassify(x) == FP_NAN
Failed test fpclassify(x) == FP_NAN
Failed test fpclassify(x) == FP_NAN
Failed test fpclassify(x) == FP_NAN
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, y) == x
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), y) == x
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test copysign(x, changesign(y)) == changesign(x)
Failed test copysign(changesign(x), changesign(y)) == changesign(x)
Failed test changesign(a[i]) == -a[i]
Failed test changesign(-a[i]) == a[i]
Failed test !signbit(changesign(-a[i]))
Failed test changesign(a[i]) == -a[i]
Failed test changesign(-a[i]) == a[i]
Failed test !signbit(changesign(-a[i]))
Failed test changesign(a[i]) == -a[i]
Failed test changesign(-a[i]) == a[i]
Failed test !signbit(changesign(-a[i]))
Failed test changesign(a[i]) == -a[i]
Failed test changesign(-a[i]) == a[i]
Failed test !signbit(changesign(-a[i]))
Failed test changesign(b) == b
Failed test changesign(a[i]) == -a[i]
Failed test changesign(-a[i]) == a[i]
Failed test !signbit(changesign(-a[i]))
Failed test changesign(a[i]) == -a[i]
Failed test changesign(-a[i]) == a[i]
Failed test !signbit(changesign(-a[i]))
Failed test changesign(a[i]) == -a[i]
Failed test changesign(-a[i]) == a[i]
Failed test !signbit(changesign(-a[i]))
Failed test changesign(a[i]) == -a[i]
Failed test changesign(-a[i]) == a[i]
Failed test !signbit(changesign(-a[i]))
Failed test changesign(b) == b

Intel 9.1, Linux, Itanium:

maddock@td178.testdrive.hp.com> icc -I ~ -O3 -fast -fp-model fast=2 
*.cpp -stat
ic
IPO: performing single-file optimizations
IPO: generating object file /tmp/ipo_iccbMO6qR.o
maddock@td178.testdrive.hp.com> ./a.out
little endian
sizeof(long double) = 16
mask<long double>::exponent = 7fff0000

Failed test fpclassify(x) == FP_NAN
Failed test fpclassify(x) == FP_NAN
Failed test fpclassify(x) == FP_NAN
Failed test fpclassify(x) == FP_NAN
Failed test fpclassify(x) == FP_NAN
Failed test fpclassify(x) == FP_NAN
Failed test fpclassify(x) == FP_NAN
Failed test fpclassify(x) == FP_NAN
Failed test isnormal(x)
Failed test fpclassify(x) == FP_NORMAL
Failed test isnormal(x)
Failed test fpclassify(x) == FP_NORMAL
Failed test fpclassify(x) == FP_NAN
Failed test fpclassify(x) == FP_NAN
Failed test fpclassify(x) == FP_NAN
Failed test fpclassify(x) == FP_NAN