On Friday, 5 August 2016 at 09:24:49 UTC, Walter Bright wrote:
On 8/5/2016 12:43 AM, Ilya Yaroshenko wrote:
You are wrong that there are far fewer of those cases. This is
naive point of
view. A lot of netlib math functions require exact IEEE
arithmetic. Tinflex
requires it. Python C backend and Mir library require exact
IEEE arithmetic.
Atmosphere package requires it, Atmosphere is used as
reference code for my
publication in JMS, Springer. And the most important case: no
one top scientific
laboratory will use a language without exact IEEE arithmetic
by default.
A library has a lot of algorithms in it, a library requiring
exact IEEE arithmetic doesn't mean every algorithm in it does.
None of the Phobos math library functions require it, and as
far as I can tell they are correct out to the last bit.
No. For example std.math.log requires it! But you don't care
about other compilers which not use yl2x and about making it
template (real version slows down code for double and float).
And besides, all these libraries presumably work, or used to
work, on the x87, which does not provide exact IEEE arithmetic
for intermediate results without a special setting, and that
setting substantially slows it down.
x87 FPU is deprecated. We have more significant performance
issues with std.math. For example, it is x87 oriented, is slows
down the code for double and float. Many functions are not
inlined. This 2 are real performance problems.
By netlib do you mean the Cephes functions? I've used them, and
am not aware of any of them that require reduced precision.
Yes and many of its functions requires IEEE. For example log2.c
for doubles:
z = x - 0.5;
z -= 0.5;
y = 0.5 * x + 0.5;
This code requires IEEE. The same code appears in our std.math :P
