This particular problem is less striking on 64-bits.

We do have a problem with floats on 64 bits, in that our only floats are tagged. This means that floats on 64-bit platforms are 61-bits, while floats on 32-bit platforms are 64 bits. So this is something that needs to stay on our list to do.

Terry

On Mon, 24 Sep 2007 paul@duologues.net wrote:

For most practical problems, this issue can be postponed for a very long time by going to the 64 bit version. Correct?

From: Bart Demoen Bart.Demoen@cs.kuleuven.ac.be Date: 9/24/07 7:17Subject: Re: [Xsb-development] Arithmetic evaluation bug in the CVS HEAD version of XSB

(Bart, do you have a practical example in which it was critical to have that one, rather special, negative integer? :-).

Of course, oodles of them :-)

I was just trying to cook up examples that give unexpected behaviour. I had started from a predicate a/2:

a(X,Y) :- X < Y .

and did queries like ?- a(large_neg_int,large_pos_int), e.g:

| ?- a(-2147483647,3).

no

for instance.

What I later pasted in my mail was some sort of abbreviation of some of the queries. I didn't even notice it was showing some different weird behaviour. I now realize that toplevel queries of </2 can behave differently from compiled goals. The problem with compiled </2 is that XSB compiles X < Y to X-Y < 0 (or something like that - when there is (undetected ?) overflow in the -/2, things go wrong.

Cheers

Bart Demoen

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