On Friday, 20 June 2014 at 12:32:39 UTC, Nick Treleaven wrote:
Hi,
A Perlin noise benchmark was quoted in this reddit thread:
http://www.reddit.com/r/rust/comments/289enx/c0de517e_where_is_my_c_replacement/cibn6sr
It apparently shows the 3 main D compilers producing slower
code than Go, Rust, gcc, clang, Nimrod:
https://github.com/nsf/pnoise#readme
I initially wondered about std.random, but got this response:
"Yeah, but std.random is not used in that benchmark, it just
initializes 256 random vectors and permutates 256 sequential
integers. What spins in a loop is just plain FP math and array
read/writes. I'm sure it can be done faster, maybe D compilers
are bad at automatic inlining or something. "
Obviously this is only one person's benchmark, but I wondered
if people would like to check their code and suggest reasons
for the speed deficit.
I saw this thread when searching for something on the site, been
a few months since anyone posted-
I fixed the D flags, gdc is now about 15% faster than the second
fastest in the benchmark(C - gcc) which obviously puts D in first.
some notes:
LDC is missing _tons_ of inline opportunities, killing it in
comparison to GDC. I think GDC inlined pretty much everything.
LDC is about 50% slower.
Also, AFAICT there's no fast-math switch for LDC(enabling this
for GDC might actually be compromising it though : ) )
I think LDC turns the floor in std.math into the same as the stdc
one, but GDC does not. std.math.floor is still abysmally slow, I
thought it was because it was still using reals but that does not
seem to be the case. GDC slows to a crawl(10-20x slower) if you
replace the stdc floor with the one in std.math(just remove the
alias)
I thought this might be interesting to someone(i.e, LDC/GDC folks
or phobos math folks)
bye.
