From: Janos Vegh (vegh.janos_at_[hidden])
Date: 2006-08-26 15:54:55
On 8/26/06, me22 <me22.ca_at_[hidden]> wrote:
>
>
> main has to return int; Your code isn't legal C++. Also, it seems
> like you end up using memory in the vector after only reserving it,
> not resizing it.
Yes, a forgotten int, my mistake.
After reserving the memory, I guess I can write the memory locations.
I think neither of the above affects the subject.
Your empty cycle time makes it obvious you're not even doing the most
> rudimentary of optimizations.
My goal was to measure the time of the empty processing,
in order to estimate the time of the net calculation,
rather than to find out that for no operation I need no time.
Here's what I get in g++ (g++ (GCC) 4.1.1 (Gentoo 4.1.1)) after making
> a few changes while using -O3 -DNDEBUG as arguments to the compiler
> (though -DNDEBUG didn't make any signifigant difference):
>
> Empty cycle
> real 0m0.003s
> user 0m0.000s
> sys 0m0.000s
>
> STL=1, SIMPLE=1, size=1000
> real 0m1.357s
> user 0m1.168s
> sys 0m0.008s
>
> STL=1, size=1000
> real 0m1.337s
> user 0m1.172s
> sys 0m0.016s
>
> STL=1, ITERATOR=1, size=1000
> real 0m1.315s
> user 0m1.172s
> sys 0m0.012s
>
> STL=1, AT=1, size=1000
> real 0m1.357s
> user 0m1.176s
> sys 0m0.004s
>
> I really don't see an issue here.
>
> I neither, except that it looks like that in the case of AT checking the
lower and upper
limits of the index needs no extra time(??).
Otherwise, on my system
$ g++ -oeffic2.exe effic2.cpp
$ time ./effic2.exe
STL=1, SIMPLE=1, ITERATOR=0, AT=0, size=1000
real 0m4.775s
user 0m4.476s
sys 0m0.080s
$ g++ -o3 -oeffic2.exe effic2.cpp
$ time ./effic2.exe
STL=1, SIMPLE=1, ITERATOR=0, AT=0, size=1000
real 0m4.749s
user 0m4.496s
sys 0m0.060s
and
$ g++ -o3 -oeffic2.exe effic2.cpp
$ time ./effic2.exe
STL=1, SIMPLE=0, ITERATOR=0, AT=0, size=1000
real 0m33.413s
user 0m32.076s
sys 0m0.100s
$ g++ -oeffic2.exe effic2.cpp
$ time ./effic2.exe
STL=1, SIMPLE=0, ITERATOR=0, AT=0, size=1000
real 0m34.554s
user 0m33.668s
sys 0m0.060s
and
$ g++ -oeffic2.exe effic2.cpp
$ time ./effic2.exe
STL=1, SIMPLE=0, ITERATOR=0, AT=1, size=1000
real 1m26.753s
user 1m24.301s
sys 0m0.080s
$ g++ -o3 -oeffic2.exe effic2.cpp
$ time ./effic2.exe
STL=1, SIMPLE=0, ITERATOR=0, AT=1, size=1000
real 1m29.311s
user 1m27.035s
sys 0m0.050s
After that you were so kind to run my test on your Linux,
maybe I need to ask MingW people about this problem.
Anyhow, thanks for replying and sorry for bothering the list with my problem
Janos