d2 file input performance

[dennis luehring]

Am 26.08.2011 19:43, schrieb Christian Köstlin:
> 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
>
> christian

i would change the test szenario a little bit

1. use a ramdisk - so stuff like location on disk, fragmentation, driver 
speed will reducued down to a little bit of noise

2. make your szenario much bigger

3. would be interesting to see for example to cumulated every 1000 
benchmarks-steps or something like that - to see caching coming in etc.

running 10.000 times

time for 1. 1000 steps xyzw
time for 2. 1000 steps xyzw
time for 3. 1000 steps xyzw
time for 4. 1000 steps xyzw
overall time ... xyz
...