Dynamic Closure + Lazy Arguments = Performance Killer?

[Jason House]

Steven Schveighoffer Wrote:

> "Jason House" wrote
> > Jason House Wrote:
> >
> >> Gregor Richards Wrote:
> >>
> >> > Jason House wrote:
> >> > > I ported some monte carlo simulation code from Java to D2, and 
> >> > > performance is horrible.
> >> > >
> >> > > 34% of the execution time is used by std.random.uniform. To my great 
> >> > > surprise, 25% of the execution  time is memory allocation (and 
> >> > > collection) from that random call. The only candidate source I see is 
> >> > > a call to ensure with lazy arguments. The memory allocation occurs at 
> >> > > the start of the UniformDistribution call. I assume this is dynamic 
> >> > > closure kicking in.
> >> > >
> >> > > Can anyone verify that this is the case?
> >> > >
> >> > > 600000 memory allocations per second really kills performance!
> >> >
> >> > Java has a much better garbage collector than D, as it doesn't need to
> >> > be conservative.
> >> >
> >> >   - Gregor Richards
> >>
> >> The code is written to explicitly avoid memory allocation, especially in 
> >> tight loops. Without this dynamic closure, the garbage collecor would 
> >> never run. This case is especially pathetic since the call to ensure will 
> >> never trigger.
> >>
> >> This is part of a mini language shootout. The Java version I cloned runs 
> >> 4x faster. This is only one piece of a much bigger problem.
> >
> > I was wrong about the 4x thing. I have bad hardware. After fixing the 
> > accidental allocation and running both the D and Java version on the same 
> > box, they're only 1% different.
> 
> When you say 'fixing the accidental allocation' you mean removing the case 
> where a dynamic closure was allocated?
> 
> I just want to make sure that is clear.
> 
> -Steve

Yes. You are right. The allocation of the dynamic closure was the only performance problem, and consumed 25% of my execution time.  I called it accidental because Andrei was unaware that he had done it.