On Monday, 4 March 2013 at 04:49:20 UTC, Andrei Alexandrescu
wrote:
You're measuring the speed of a couple of tight loops. The
smallest differences in codegen between them will be on the
radar. Use straight for loops or "foreach (i; 0 .. limit)" for
those loops...
Thanks Andrei!
I validated your analysis by doing a straight port of the C code
to D, even using the same memory layout (matching malloc calls).
The port was trivial, which was very reassuring. As evidence, I
had to tweak only 8 lines othe C to make compiled under gdc. The
mmult() function in the D version remained identical to that in
the C version.
Even more reassuring was that the performance of the resulting D
matched the C to within 1% tolerance (about 200-500 msec seconds
slower on the D side; presumably due to runtime init).
$time ./gdc_compiled_ported_cpp_version
-1015380632 859379360 -367726792 -1548829944
real 1m32.418s
user 1m32.370s
sys 0m0.020s
$
It's a great feeling, knowing the bare metal is available if need
be.
Thanks guys!
-J
