Performance in csharp, scientific simulation

[Steve Walker]

Re: Performance in csharp, scientific simulation

In message <1122300034.553 506.321160@z14g 2000cwz.googleg roups.com>,
Michael Gorbach <mgorbach@gmail .com> writes[color=blue]
>Thanks everyone for the great responses. I love this newsgroup!
>Steve, yes I do know about mono and i will use it if i dont port, but
>its speed is questionable. At best, it will run as fast as microsoft
>.net, at worst there will be a performance hit.[/color]

Sniffing round the net, Mono currently appears to be a little slower
than Microsoft's implementation, but I'd expect the gap to close.

--
Steve Walker

[Jon Skeet [C# MVP]]

Re: Performance in csharp, scientific simulation

Michael Gorbach <mgorbach@gmail .com> wrote:[color=blue]
> Thanks everyone for the great responses. I love this newsgroup!
> Steve, yes I do know about mono and i will use it if i dont port, but
> its speed is questionable. At best, it will run as fast as microsoft
> .net, at worst there will be a performance hit.[/color]

That depends on what you do with it. When some colleagues were
investigating performance comparisons, they found that for many things
..NET was faster than Mono, but for some others Mono was faster than
..NET.

--
Jon Skeet - <skeet@pobox.co m>

http://www.pobox.com/~skeet

If replying to the group, please do not mail me too

[Dov]

Re: Performance in csharp, scientific simulation

I am learning C# and I am writing scientific software. What I did
find so far is that when the data is in arrays, the differences between
C# and the equivalent C++/C codes are very small.

I tried (1) a Monte-Carlo simulation, and (2) translated from C a
routine that solves a system of linear equations (simq from the CEPHES
package) and benchmarked a large system with the coefficients
initialized by random number generator. The C/C++ & C# versions ended
with the same result and nearly the same time.

However, when I translated part of the Stepanov benchmark ( a C++
benchmark that measures abstraction penalty ) I did find a major
performance hit. I suspect that the current C# optimizer is currently
not yet developed enough to deal with high level of abstraction. Of
course, I am a C# beginner and perhaps I can learn to translate better.

I think that if you are a little careful in performance-critical
parts of your code, you can achieve nearly C speeds.

Dov

Michael Gorbach wrote:[color=blue]
> I was asked this summer to write a monte carlo code to simulation
> magnetic nanoparticles. For the nonphysicists, basicly it is a
> simulation where most of the time is taken up by looping through each
> pair in an array of 500 or so particles, in order to calculate
> interaction potential. I wrote what i have so far in csharp because i
> wanted to learn it and though it would give me some good experience. I
> am now beginning to understand that .net and managed code in general
> lags far behind performance wise. Eventually i am probably going to
> have to port to c++, unmanaged, because the simulation code will need
> to run on linux as well.
> My question is this:
> What can i do in my chsarp code right now to speed up the performance.
> The main method that is run hundreds of times a second basicly involves
> calculating a vector dot product (using my own vector class), and an
> exponential. Would marking the method unsafe speed anything up>[/color]

[Dov Bai]

Re: Performance in csharp, scientific simulation

I am learning C# and I am writing scientific software. What I did
find so far is that when the data is in arrays, the differences between

C# and the equivalent C++/C codes are very small.


I tried (1) a Monte-Carlo simulation, and (2) translated from C a
routine that solves a system of linear equations (simq from the CEPHES
package) and benchmarked a large system with the coefficients
initialized by random number generator. The C/C++ & C# versions ended
with the same result and nearly the same time.


However, when I translated part of the Stepanov benchmark ( a C++
benchmark that measures abstraction penalty ) I did find a major
performance hit. I suspect that the current C# optimizer is currently
not yet developed enough to deal with high level of abstraction. Of
course, I am a C# beginner and perhaps I can learn to translate better.



I think that if you are a little careful in performance-critical
parts of your code, you can achieve nearly C speeds.


Dov


Michael Gorbach wrote:[color=blue]
> I was asked this summer to write a monte carlo code to simulation
> magnetic nanoparticles. For the nonphysicists, basicly it is a
> simulation where most of the time is taken up by looping through each
> pair in an array of 500 or so particles, in order to calculate
> interaction potential. I wrote what i have so far in csharp because i
> wanted to learn it and though it would give me some good experience. I
> am now beginning to understand that .net and managed code in general
> lags far behind performance wise. Eventually i am probably going to
> have to port to c++, unmanaged, because the simulation code will need
> to run on linux as well.
> My question is this:
> What can i do in my chsarp code right now to speed up the performance.
> The main method that is run hundreds of times a second basicly involves
> calculating a vector dot product (using my own vector class), and an
> exponential. Would marking the method unsafe speed anything up>[/color]

[Michael Gorbach]

Re: Performance in csharp, scientific simulation

My particles are stored in a class Nanoparticle, which contains a
member of a Vector class i created. The dot product operator is done by
the * operator which i overloaded for the Vector class. It simply uses
a for loop over the coordinates to do the dot product.

[Dov Bai]

Re: Performance in csharp, scientific simulation

And that is probably the source of your slowdown - you have created at
least two levels of abstraction above your particles: (1) The Vector
class, and (2) overloading the Vector operations (e.g. the * operator).

Dov

[Michael Gorbach]

Re: Performance in csharp, scientific simulation

What is the simplest way to do that without created this slowdown?

[Dov Bai]

Re: Performance in csharp, scientific simulation

Where performance is critical, try to use built-in data structures. For
example, if you have 3D particles use two dimensional jagged arrays
(e.g. double [][] ) to store the coordinates. The size of the first
dimension is the number of particles and of the the second dimension is
3 (for x, y, z).

Dov

Michael Gorbach wrote:[color=blue]
> What is the simplest way to do that without created this slowdown?[/color]