Marc:

High-end P4, Athlon, etc., as well as Athlon 64, have 64-bit floating-point instructions pretty much the same as any other RISC (I don't mean the fused multiply-add of IBM's Power). This is accessed through the SSE2 instruction set on Intel, and similar things on AMD's Athlon.

Some algorithms in _num.scm (for converting strings to and from floating-point numbers, for example) rely on proper 64-bit floating-point arithmetic. Gambit simulates this by setting the rounding precision to 64-bits on x86's 80-bit floating-point stack, but there is still the possibility of double rounding, especially for denormalized numbers, because of the extended exponent range of 80-bit numbers on the floating-point stack.

I'm thinking it might be a good thing for Gambit's configure script to test for the availability of SSE2 or the similar thing for AMD and to set those options when building Gambit with gcc.

Brad