Hello D-World,

I've written a small terraingenerator in D based on the Hill-Algorithm.

To generate a terrain I only need to call the method generateTerrain(...) which returns a float-Array containing the height of each pixel (2D Array mapped with a 1D array with length resolution^2).

What I'd like to do:
Generate #treads seperate maps in a own thread and combine and normalize them afterwards.

I have little to no experience working with multiple threads. I tried it once in java for University but did not really get working.

What I imagine as solution (I know it won't work this way, but to give you a better idea):

for(int i = 0; i < #threads; i++){
    runInThread(generateTerrain(...));
}

Greetings and thanks in advance Konstantin

> What I imagine as solution (I know it won't work this way, but to give you a better idea):
>
> for(int i = 0; i < #threads; i++){
>     runInThread(generateTerrain(...));
> }

Are you looking for parallel? http://dlang.org/library/std/parallelism/parallel.html

> Are you looking for parallel? http://dlang.org/library/std/parallelism/parallel.html

I have seen this, but I'm not sure how to use it.

Maybe:

float[][] maps = new float[#threads][resolution * resolution];

foreach(i, ref elem; parallel(maps)){
    elem = generateTerrain(...);
}

Does this look right?

On Thursday, 9 October 2014 at 10:10:20 UTC, Konstantin wrote:
>> Are you looking for parallel? http://dlang.org/library/std/parallelism/parallel.html
>
> I have seen this, but I'm not sure how to use it.
>
> Maybe:
>
> float[][] maps = new float[#threads][resolution * resolution];
>
> foreach(i, ref elem; parallel(maps)){
>     elem = generateTerrain(...);
> }
>
> Does this look right?

Yeah, it is.

On 10/09/2014 03:10 AM, Konstantin wrote:
>> Are you looking for parallel?
>> http://dlang.org/library/std/parallelism/parallel.html
>
> I have seen this, but I'm not sure how to use it.

I have the following chapter with some examples:

  http://ddili.org/ders/d.en/parallelism.html

If concurrency is more suited to your application, then there is the following as well:

  http://ddili.org/ders/d.en/concurrency.html

Ali

On Thu, 2014-10-09 at 11:29 +0000, Sag Academy via Digitalmars-d-learn wrote:
> On Thursday, 9 October 2014 at 10:10:20 UTC, Konstantin wrote:
> >> Are you looking for parallel? http://dlang.org/library/std/parallelism/parallel.html
> >
> > I have seen this, but I'm not sure how to use it.
> >
> > Maybe:
> >
> > float[][] maps = new float[#threads][resolution * resolution];
> >
> > foreach(i, ref elem; parallel(maps)){
> >     elem = generateTerrain(...);
> > }
> >
> > Does this look right?
> 
> Yeah, it is.

Or maybe not. The code above is fine per se, but only tackles the generation phase, there will be later phases. It may be that other parts of http://dlang.org/library/std/parallelism.html used slightly differently would be better for describing more of the problem. taskPool has a lot of interesting capabilities, including parallel reduce which gives a full map–reduce type scatter–gather approach: OP did mention that there was a generation then integration activity overall.

Of course, if absolute performance is required things get a bit more tricky avoiding overheads.

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