On 12/18/2015 12:19 AM, Ola Fosheim Gr wrote:
On Friday, 18 December 2015 at 07:30:52 UTC, drug wrote:
What I mean about order of operations is that if you go
a = b*a+c*c + e;
the compiler is free to rewrite that as
float __tmp0 = a*b;
float __tmp1 = c*c;
and then do either of
float __tmp2 = __tmp0+__tmp1;
a = __tmp2 + e;
OR
float __tmp2 = __tmp0+e;
a = __tmp2+__tmp1;
I see, thanks to all!
I don't think this can be right, unless you use some kind of fast-math
optimizer.
But:
Modern C++ compilers try to support ieee754-2008, which is needed to get
reproducible results. D is based on the older 1985 version, and there is
no announced effort to make it modern.
Thank you for the reference. If the Wikipedia article is precise in
language, it is just a recommendation:
"Clause 10: Expression evaluation
This clause is new; it recommends how language standards should specify
the semantics of sequences of operations, and points out the subtleties
of literal meanings and optimizations that change the value of a result."
https://en.wikipedia.org/wiki/IEEE_754_revision#Clause_10:_Expression_evaluation
Ali
