Re: __index returns truncated to one, why?
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- Subject: Re: __index returns truncated to one, why?
- From: Sean Conner <sean@...>
- Date: 2014年4月10日 19:57:14 -0400
It was thus said that the Great Geoff Leyland once stated:
> On 11/04/2014, at 11:14 am, Sean Conner <sean@conman.org> wrote:
>
> > It was thus said that the Great Geoff Leyland once stated:
> >
> >> I’ve just had a “real world” situation where reducing temporary table
> >> creation halved the time it took to perform a computation. Granted, the
> >> original code was probably a bit wasteful with them, and algorithmic
> >> improvements made a bigger difference, but temporary tables were a
> >> measurable factor.
>
> > I'd be interested to know of the CPU, CPU speed
>
> $ uname -v
> Darwin Kernel Version 13.1.0: Thu Jan 16 19:40:37 PST 2014; root:xnu-24229020~2/RELEASE_X86_64
> $ sysctl -n machdep.cpu.brand_string
> Intel(R) Core(TM) i7-2675QM CPU @ 2.20GHz
>
> > and type (general terms) of computation
>
> Approximate phrase search using dynamic programs for approximate phrase
> and word matching[1]. For each invocation of the approximate match both
> the phrase matcher and the word matcher allocated tables to hold the
> stages and states of their relevant DPs. Now I keep a single “static”
> table around and reuse it on each invocation.
>
> It’s relevant that I run the same tool on more limited hardware where I
> was running out of memory, so I called collectgarbage once per query.
> Getting memory use to the point that it wasn’t a problem meant I could
> stop doing that, and that also contributed to time savings.
>
> > Also, the actual difference.
>
> Original run time was about a minute for a test data set, and “luajit
> -jp=v…” showed about half the time was in the GC. Cleaning up table
> allocations roughly halved the run times and reduced GC time to about 5%.
> Fixing a one-line thinko and tuning a parameter reduced the number of
> matches necessary to the point that it now takes a couple of seconds.[2]
Thanks. Wow. Okay. That is quite significant.
I also like that you profiled before changing the code.
-spc
> [1] I know there are alternative methods for this.
> [2] I don’t think this is a case of me making the code fast, more that it’s less slow.
- References:
- Re: __index returns truncated to one, why?, steve donovan
- Re: __index returns truncated to one, why?, Duncan Cross
- Re: __index returns truncated to one, why?, Sean Conner
- Re: __index returns truncated to one, why?, Thiago L.
- Re: __index returns truncated to one, why?, steve donovan
- Re: __index returns truncated to one, why?, Javier Guerra Giraldez
- Re: __index returns truncated to one, why?, Andrew Starks
- Re: __index returns truncated to one, why?, Geoff Leyland
- Re: __index returns truncated to one, why?, Sean Conner
- Re: __index returns truncated to one, why?, Geoff Leyland