On Fri, 26 Aug 2011 13:43:23 -0400, Christian Köstlin
<christian.koest...@gmail.com> wrote:
Hi guys,
i started the thread:
http://stackoverflow.com/questions/7202710/fastest-way-of-reading-bytes-in-d2
on stackoverflow, because i ran into kind of a problem.
i wanted to read data from a file (or even better from a stream, but
lets stay with file), byte-by-byte. the whole thing was part of my
protobuf implementation for d2, and there you have to look at each byte
to read out the varints. i was very proud of my implementation until i
benchmarked it first against java (ok ... i was a little slower than
java) and then against c++ (ok ... this was a complete different game).
after some optimizing i got better, but was still way slower than c++.
so i started some small microbenchmarks regarding fileio:
https://github.com/gizmomogwai/performance in c++, java and d2.
could you help me improve on the d2 performance? i am sure, that i am
missing something fundamental, because i thing it should be at least
possible be equal or better than java.
thanks in advance
Two things:
First, there is a large difference:
C++ version:
int read() {...}
D version:
int read(ubyte *bufferptr) {...}
This may not be optimized as well. You should make it the same.
Second, use -inline, it will help tremendously.
I'd bet money that the largest slowdown is the function calls. Inlining
makes things run so much faster it's not even funny.
Also, note that FILE* is *already buffered*, there is no reason to do
anything but fgetc. In fact, it would probably be faster.
-Steve
