Arkaitz Bitorika <arkaitz.bitorika <at> gmail.com> writes:
> I've verified that the function causes the exception when embedded in
> the program but not when used from a simple C program with just a main
> () function. The successful version iterates 31 times over the for
> loop while the crashing one fails the 30th time that it does "pinf *=
> mul".
>
> Now we know exactly where the crash is, but no idea how to fix it ;).
Hi,
I just found this old thread, and it looks like I've got the very same problem:
Turns out that Borland C++ Builder (which I'm using, and you are most probably
as well) can't get to infinity by multiplying a number with 1E10 over and over,
but throws an exception instead when ecceeding number space:
On 22 Apr 2006, at 20:12, Andrew Straw wrote:
> static double
> pinf_init(void)
> {
> double mul = 1e10;
> double tmp = 0.0;
> double pinf;
>
> pinf = mul;
> for (;;) {
> pinf *= mul;
> if (pinf == tmp) break;
> tmp = pinf;
> }
> return pinf;
> }
My proposal is to ask the numpy people to patch numpy as follows:
Don't multiply, but instead create pinf according to IEEE 754 specifications:
char inf_string[9] = "\x00\x00\x00\x00\x00\x00\xF0\x7F";
double pinf = ((double*)inf_string)[0];
This will get rid of the overflow for little endian machines. For big endian
architectures, just reverse the byte order in inf_string.
I already submitted a bug report to their bugtracker.
Cheers,
Thomas
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