On 12/22/2010 11:04 PM, Andreas Mayer wrote:
To see what performance advantage D would give me over using a scripting
language, I made a small benchmark. It consists of this code:
auto L = iota(0.0, 10000000.0);
auto L2 = map!"a / 2"(L);
auto L3 = map!"a + 2"(L2);
auto V = reduce!"a + b"(L3);
It runs in 281 ms on my computer.
The same code in Lua (using LuaJIT) runs in 23 ms.
That's about 10 times faster. I would have expected D to be faster. Did I do
something wrong?
The first Lua version uses a simplified design. I thought maybe that is unfair
to ranges, which are more complicated. You could argue ranges have more
features and do more work. To make it fair, I made a second Lua version of the
above benchmark that emulates ranges. It is still 29 ms fast.
The full D version is here: http://pastebin.com/R5AGHyPx
The Lua version: http://pastebin.com/Sa7rp6uz
Lua version that emulates ranges: http://pastebin.com/eAKMSWyr
Could someone help me solving this mystery?
Or is D, unlike I thought, not suitable for high performance computing? What
should I do?
I changed the code to this:
auto L = iota(0, 10000000);
auto L2 = map!"a / 2.0"(L);
auto L3 = map!"a + 2"(L2);
auto V = reduce!"a + b"(L3);
and ripped the caching out of std.algorithm.map. :-)
This made it go from about 1.4 seconds to about 0.4 seconds on my
machine. Note that I did no rigorous or scientific testing.
Also, if you really really need the performance you can change it all to
lower level code, should you want to.
