Re: [vox-tech] c program in linux vs sgi

[jdneMAPSwmil@dcn.davis.ca.us]

On Sat, 18 Nov 2000, Qinghua Zhong wrote:

> hello, I am trying to compile and run one program in linux and sgi.
> some problems come up and I don't understand.

> 1) when I am running the program in linux, there is a "core" file created,
> but never happen in sgi. so if I have a big calculation, core is very
> large and it stop running in linux because of "core dumped".

Sounds like a portability problem.  Hard to diagnose from this
description. Try running gdb under linux to find the problem code, and
learn how to avoid that portability problem in the future.

> 2) if condition problem-->never happend in sgi machines again.

I don't understand this phrase.

>    x is 0.55 (double variable)
>    y is 55 (int variable), z is 100 (int variable)
>    (x == (double) y / (double) z) returns false.
>    how come?

It is rarely a good idea to compare floating point values directly, since
round-off error can make numbers that appear to be the same, not the same.  
I suspect that in your case, x is equal to 0.55 plus some very very small
difference from (double)55/100, but you just typed what was printed on
your screen.  Putting a literal constant 0.55 in place of x, gcc on linux
shows this test returning true for me.

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