So now we're on a microbenchmarking spree

[oNyx]

Uh uh diggin up a dead thread

There is a little glitch in the Test class. public void math() uses a long for the result (instead of a double). The massive amount of casting makes it ~25% slower than it has to be. Before it was 1:6 and now it's about 1:4.5.

Well, Math got faster and FMath isn't "17.6 times faster than Math" anymore, but it's still faster and might be a measurable difference in your application.

[erikd]

Hmmm, I'm quite sure I fixed that when I measured it. I print the results and they were approx. the same. Lemme run it again  

[erikd]

I checked and re-ran the benchmark.
On the client, I'm getting FMath being ~6.2 times as fast, on the server about ~22.8 times as fast.

This is on 1.4.2_03

[EDIT:]
BTW, it's of course not really a comparitive test since Math obviously has far greater precision but it might indicate what kind of performance you could gain by settling for slightly inaccurate results.
That said, I suggest to always use Math, and switch to something like FMath if (after profiling) it's clear that Math causes a major bottleneck and that FMath's inaccuracies are within bounds of acceptability.

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[oNyx]

[...]
That said, I suggest to always use Math, and switch to something like FMath if (after profiling) it's clear that Math causes a major bottleneck and that FMath's inaccuracies are within bounds of acceptability.

Yea, of corse

In my current case I'll only have one class wich uses some basic math relativly often. Therefore I can just try it out without too much hassle.

One thing wich is rather odd: with C/C++ lookup tables are slower then doing it the proper way, because lookup tables needs to execute more commands. Well, it's more inaccurate than the über accurate java way in double precision. I wish there would be a float math lib and a hotspot compiler wich knows about it, too.

That would be pretty awesome

[erikd]

I think many things are slower to do using look-up tables these days (CPU's being much faster than memory), unless they are very processor intensive tasks. Especially in java, because of its bounds checks.
In the old days I used look-up tables everywhere. Now only in some circumstances.
And yes, a fast, less accurate Math lib like you described (or a even a switch) would be awesome.
I wish nobody noticed java's slight 'inaccuracy' with sin/cos in 1.3