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Re: Why are long functions slower?

From: Bernhard M. Wiedemann
Subject: Re: Why are long functions slower?
Date: Mon, 16 Oct 2017 11:29:41 +0200
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On 2017-10-15 20:53, Eduardo A. Bustamante López wrote:
> I have some questions:
> 1. Which specific versions of 4.3 and 4.4?
> 2. Did you compile bash from source? (if so, what did you use for CFLAGS and 
> the configure script parameters? are you
>    using bash's malloc or the system malloc?)
> 3. ... Or did you use a distro package? (if so, can you provide links to the 
> specific packages used?)

I was testing with the openSUSE Tumbleweed packages, which is probably
compiled with -O2 and pretty standard configure options:
around line 429

> 4. Do you have precise timing information? How specifically did you test? How 
> many iterations? etc

I used the reproducer script in my previous email, containing two
similar functions (one short, one long) that both do nothing in a loop
with N=30000
and was comparing the timing of those two on the same bash version.

e.g. for bash-4.3 on a 2.80GHz Core i7 I get

real    0m0.271s
user    0m0.270s
sys     0m0.003s

real    0m0.482s
user    0m0.483s
sys     0m0.000s

interestingly, the number of colons has a much larger impact on runtime
than the number of spaces.

Thanks for looking into that.

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