Re: [boost] Results of Cray SV1 regression tests

From: Dave Abrahams (dave_at_[hidden])
Date: 2003-02-05 10:24:09

On Wednesday, February 05, 2003 10:11 AM [GMT+1=CET],
Matthias Troyer <troyer_at_[hidden]> wrote:

> I am looking into it but already have a conjecture. When using signed
> 64 bit integers the Cray compiler (with optimization turned on) uses
> the floating point units to actually perform the operations in 46 bit
> arithmetic. This speeds up things but causes compatibility problems. In
> the case of the jam sources we could avoid this "optimization" by using
> unsigned types. Is it possible to use an unsigned integer here to avoid
> similar problems?

Just to be clear, we didn't avoid an optimization by using unsigned types.
We avoided undefined behavior due to overflow in signed integers, or
conversions from unsigned->signed.

-- 
Dave Abrahams
Boost Consulting
http://www.boost-consulting.com