pi benchmark on ldc and dmd

[Andrew Wiley]

On Mon, Aug 1, 2011 at 8:38 PM, Adam D. Ruppe <destructionator at gmail.com>wrote:

> bearophile wrote:
> > In such situations it's never enough to compare the D code compiled
> > with DMD to the D code compiled with LDC. You also need a reference
> > point, like a C version compiled with GCC (here using GMP bignums).
> > Such reference points are necessary to anchor performance
> > discussions to something.
>
> Actually, I don't think that would be relevant here.
>
> The thread started with someone saying the DMD backend is garbage
> and should be abandoned.
>
> I'm sick and tired of hearing people say that. The Digital Mars
> code has many, many advantages over the others*.
>
> But, it was challenged specifically on the optimizer, so to
> check that out, I wanted all other things to be equal.
>
> Same code, same front end, same computer, as close to same runtime
> and library is possible with different compilers. The only
> difference should be the backend so we can draw conclusions about
> it without other factors skewing the results.
>
>
> So for this, I just wanted to compare dmd backend to ldc and
> gdc backend so I didn't worry too much about absolute numbers
> or other languages. (Actually, one of the reasons I picked the
> pi one was after the embarrassing defeat in floating point, I was
> hoping dmd could score a second victory and I could follow up
> on that "prove it" post with satisfaction. Alas, the facts didn't
> work out that way. Though, I still do find dmd to beat g++
> on a lot of real world code - things like slices actually make
> a sizable difference.)
>
> But regardless, it was just about comparing backends, not
> doing language comparisons.
>
> ===
>
> * To name a huge one. Today was the first time I ever got ldc
> or gdc to actually work on my computer, and it took a long, long
> time to do it. I've tried in the past, and failed, so this was
> a triumph. Big success.
>
> I was waiting over an hour just for gcc+gdc to compile! In the
> time it takes for gcc's configure script to run, you can make
> clean, build dmd, druntime and phobos.
>
> It's a huge hassle to get the code together too. I had to go
> to *four* different sites to get gdc's stuff together (like 80
> MB of crap, compressed!), and two different ones to get even the
> ldc binary to work. Pain in my ASS.
>
>
> And this is on Linux too. I pity the fool who tries to do this
> on Windows, knowing how so much linux software treats their
> Windows "ports".
>
>
> I'd like to contrast to dmd: unzip and play with wild abandon.
>

Yes, GDC takes forever and a half to build. That's true of anything in GCC,
and it's just because they don't trust the native C compiler at all. LDC
builds in under a half hour, even on my underpowered ARM SoC, so I don't see
how you could be having trouble there.
As for Windows, Daniel Green (hopefully I'm remembering right) has been
posting GDC binaries.

I do respect that DMD generates reasonably fast executables recklessly fast,
but it also doesn't exist outside x86 and x86_64 and the debug symbols (at
least on Linux) are just hilariously bad.

Now if I could just get GDC to pad structs correctly on ARM...
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