On Apr 23, 2011, at 9:54 PM, Michael D. Berger wrote: On my CentOS 5 box, in a C++ program that does much arithmetic,
including numerous matrix multiplications, I have a situation in
in which the result depends on the nature of nearby I/O. Thus,
with all arithmetic done with type double, and where values
are mostly in the range [-1.0e0,+1.0e0] or nearby, I do:
cerr << "some stuff" << endl;
mat3 = matmult(mat1,mat2);
I get a difference of the order 1.0e-15 depending on whether the
cerr line does or does not end in "endl" as shown.
I am imagining that there is some "randomness" in the roundoff
that depends on the I/O situation. Is this credible? Any other
suggestions?
Thanks for your help,
Mike.
Mike, I think I'm understanding your problem. This just sounds like a floating point rounding issue.
You've read the floating point bible already?
Todd |
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