On Friday, 5 August 2016 at 09:40:59 UTC, Ilya Yaroshenko wrote:
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).
Yep.
1) There are some function (exp, pow, log, round, sqrt) for which
using llvm_intrinsincs significantly increases your performance.
It's a simple benchmark and might be flawed, but I hope it shows
the point.
Code is here:
https://gist.github.com/wilzbach/2b64e10dec66a3153c51fbd1e6848f72
ldmd -inline -release -O3 -boundscheck=off test.d
fun: pow
std.math.pow = 15 secs, 914 ms, 102 μs, and 8 hnsecs
core.stdc.pow = 11 secs, 590 ms, 702 μs, and 5 hnsecs
llvm_pow = 13 secs, 570 ms, 439 μs, and 7 hnsecs
fun: exp
std.math.exp = 6 secs, 85 ms, 741 μs, and 7 hnsecs
core.stdc.exp = 16 secs, 267 ms, 997 μs, and 4 hnsecs
llvm_exp = 2 secs, 22 ms, and 876 μs
fun: exp2
std.math.exp2 = 3 secs, 117 ms, 624 μs, and 2 hnsecs
core.stdc.exp2 = 2 secs, 973 ms, and 243 μs
llvm_exp2 = 2 secs, 451 ms, 628 μs, and 9 hnsecs
fun: sin
std.math.sin = 1 sec, 805 ms, 626 μs, and 7 hnsecs
core.stdc.sin = 17 secs, 743 ms, 33 μs, and 5 hnsecs
llvm_sin = 2 secs, 95 ms, and 178 μs
fun: cos
std.math.cos = 2 secs, 820 ms, 684 μs, and 5 hnsecs
core.stdc.cos = 17 secs, 626 ms, 78 μs, and 1 hnsec
llvm_cos = 2 secs, 814 ms, 60 μs, and 5 hnsecs
fun: log
std.math.log = 5 secs, 584 ms, 344 μs, and 5 hnsecs
core.stdc.log = 16 secs, 443 ms, 893 μs, and 3 hnsecs
llvm_log = 2 secs, 13 ms, 291 μs, and 1 hnsec
fun: log2
std.math.log2 = 5 secs, 583 ms, 777 μs, and 7 hnsecs
core.stdc.log2 = 2 secs, 800 ms, 848 μs, and 5 hnsecs
llvm_log2 = 2 secs, 165 ms, 849 μs, and 6 hnsecs
fun: sqrt
std.math.sqrt = 799 ms and 917 μs
core.stdc.sqrt = 864 ms, 834 μs, and 7 hnsecs
llvm_sqrt = 439 ms, 469 μs, and 2 hnsecs
fun: ceil
std.math.ceil = 540 ms and 167 μs
core.stdc.ceil = 971 ms, 533 μs, and 6 hnsecs
llvm_ceil = 562 ms, 490 μs, and 2 hnsecs
fun: round
std.math.round = 3 secs, 52 ms, 567 μs, and 3 hnsecs
core.stdc.round = 958 ms and 217 μs
llvm_round = 590 ms, 742 μs, and 7 hnsecs
2) As mentioned before they can yield _different_ results
https://dpaste.dzfl.pl/c0ab5131b49d
