On 06/15/2010 09:36 PM, piotrm wrote:
Apologies if this is not the right place to inquire about this, cannot seem to find any other outlet:
Hi piotrm,
you should check out the library documentation.
Is it correct behavior for floating point calculations to be done differently once ppl.hh is included in a c++ program as well as the printing of floats? Here is an example of what I'm referring to:
#include <cstdio>
int main() { double a = 0.50000000000000011102230246251565404236316680908203125; double b = 0.5f / a; printf("%0.60f %f %0.60f %f\n", a, a, b, b); return 0; }
This prints (for me)
0.500000000000000111022302462515654042363166809082031250000000 0.500000 0.999999999999999777955395074968691915273666381835937500000000 1.000000
If I include ppl, as in below:
#include <cstdio> #include "ppl.hh"
int main() { double a = 0.50000000000000011102230246251565404236316680908203125; double b = 0.5f / a; printf("%0.60f %f %0.60f %f\n", a, a, b, b); return 0; }
I get the following
0.500000000000000111022302462515654042363166809082031250000000 0.500000 0.999999999999999888977697537484345957636833190917968750000000 0.:00000
Notice the strange way the b is printed the second time. I also found instances where numbers that are close to 0.01 get printed as 0.00:000
Is this perhaps an installation issue on my part? I noticed this using the OCaml interface, that is, use of ppl changed the behavior of the float types in OCaml in the same way the behavior is changed in C++ above.
See the documentation of
void Parma_Polyhedra_Library::set_rounding_for_PPL() void Parma_Polyhedra_Library::restore_pre_PPL_rounding() void Parma_Polyhedra_Library::initialize() void Parma_Polyhedra_Library::finalize()
Use also `man libppl' to see the role played by the PPL_NO_AUTOMATIC_INITIALIZATION macro. All the best,
Roberto