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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 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 |
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:
https://build.opensuse.org/package/view_file/openSUSE:Factory/bash/bash.spec
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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