Re: GNU Parallel Bug Reports Parallel is slower and results a bit different

[Ole Tange]

On Thu, Feb 23, 2012 at 4:46 PM, Jose Pablo Barrantes
<address@hidden> wrote:

> whenever I try the following:
>
> address@hidden time find . -name '*.el' | parallel ls -la | wc -l
> 5345
>
> real 0m13.176s
> user 0m40.714s
> sys 0m16.039s
> address@hidden time find . -name '*.el' | xargs  ls -la | wc -l
> 5347
>
> real 0m0.177s
> user 0m0.117s
> sys 0m0.120s
>
> as you can see, with parallel it's significantly slower and results are a
> bit different. I'm I doing something wrong?

Startup

GNU parallel is slow at starting up - around 250 ms. Half of the
startup time on the local computer is spent finding the maximal length
of a command line. Setting -s will remove this part of the startup
time.

Job startup

Starting a job takes around 3 ms. This can be a big overhead if the
job takes very few ms to run. Often you can group small jobs together
using -X which will make the overhead less.

Using --ungroup the 3 ms can be lowered to around 2 ms.


/Ole