On Sun, Feb 09, 2003 at 04:56:28PM -0500, Dave Keller wrote:
>
> >This is why I think i have alot of reluctance to move to Java; C is by far
> >my prefered strongly-typed, "non-scripting" language. But I am a
> >dinosaur...
> >
> >
> Nothing wrong with that, C is an excellent language and there is still
> plenty of C development going on. If C is the right tool for the job,
> then by all means use it.
>
> Speaking of C, I was wondering if anybody has done any experimenting
> with using C/C++ and JNI for computational and/or resource intensive
> tasks. Since BioJava is based on interfaces, it seems you could replace
> sequence implementations and objects that perform calculations on
> sequences with C implementations.
I'll put in a mild bite on this one. Many years ago, I wrote
a little tool which did some naive (but rather computationally
intensive -- or at least it felt that way on the hardware
available at the time ;-). It had an AWT frontend, a main loop
doing the actual calculations, and some graphing routines grafted
on the back. You know the kind of thing...
Anyway, version 1 was pure Java all the way through. It was
a little slow, so I re-wrote the whole of the main loop in C,
and called it through JNI. I got something like a 3-4 times
speedup at the time, which, right then, was useful to me.
However, there are a few points to note about this:
- At the time I was using the very first (probably counts as
an alpha) port of JDK1.2 to Linux. This included the
dearly departed `sunwjit' compiler, which was *nowhere near*
as fast as the current VMs (especially Hotspot server). I'm
actually tempted now to dig it all out, see if I can still
get the JNI bits to compile, and post new benchmarks. Maybe
tommorow.
- You only got speed benefits if you shunted the whole loop
across to C. Native-coding the body didn't help at all,
and maybe even made things worse (I can't remember now).
But JNI calls were, at the time, seriously expensive.
The cost of Java -> C calling makes me suspect that naively
making native implementations of the BioJava stuff is unlikely
to be worthwhile in the vast majority of cases. That said,
I believe that JNI costs are substantially lower in JDK1.4.x,
so it's something which might be worth reconsidering now.
Does anyone have *recent* JNI experience, and want to comment
on this?
Thomas.
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