Re: Random crashes with ABC enabled
- From: Michael <mike.lynch@xxxxxxx>
- To: luajit@xxxxxxxxxxxxx
- Date: Thu, 27 Mar 2014 06:48:45 -0500
If your array really is "native" then #arr in your for loop should be #arr-1.
Denis Golovan <denis.golovan@xxxxxxxxx> wrote:
>Hi
>
>I'd like to share something I cannot call a relevant bug report. Unfortunately.
>I could not create a small example to reproduce. But it happens rather often.
>
>Still I decided to give some info on the issue. Maybe it can be useful.
>
>Due to nature of my usage, I tend to use large native arrays I loop
>over with a small amount of calculations per element. "Number
>crunching", as it is usually called.
>
>After some time I saw a real necessity in increasing "loopunroll"
>parameter. It allowed me to bring my initial speed back (difference
>about 100x). It was related to deeply nested functions inside my loops
>where only a really small subset of paths is used. The compiler agreed
>to unroll and optimize my loops again.
>
>Unfortunately I began to notice some strange things after increasing
>"loopunroll" parameter.
>Sometimes immediately, sometimes after several minutes of
>calculations, my program starts crashing in places where I access
>native arrays in a loop. Those are pretty innocent looking loops like
>:
>
>for i=0,#arr do
> if arr[i] then -- native boolean array access
> ...
> end
>end
>
>It looks like "arr" (which is just a wrapper for a pointer to a native
>array first element) points nowhere or "i" index goes into a large
>negative value.
>
>Currently I use a following code for setting parameters (some of them
>are surely an overkill), but it helps to reduce the bug frequency
>while still having a decent calculation speed.
>
>jit.opt.start("maxmcode=10240", "maxtrace=3000", "maxside=400",
>"maxsnap=3000", "maxirconst=2000",
> "hotloop=5", "hotexit=20", "instunroll=25",
>"loopunroll=100", "callunroll=25")
>jit.opt.start(3)
>jit.opt.start("-abc") -- without this one if happens really often
>jit.flush()
>
>I've upgraded to 2.0.3, but still no luck.
>
>Could you suggest something?
>
>P.S. I am under Linux x86 arch.
>
>BR,
>Denis
>
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