On Wed, 2007-01-03 at 17:49 -0500, Ian C. Blenke wrote:
> Eben King wrote:
>
> > On Wed, 3 Jan 2007, Mike Branda wrote:
> >
> >> So I've been playing with ImageMagick to batch process psd files into
> >> flattened jpgs. I have a bash script that runs a for loop with
> >> "convert" on a directory. What I have noticed is that in xosview on my
> >> Dual Intel Hyper Threaded box ( shows up as 4 cpu's cause of the HT ),
> >> only one ( or one half? ) CPU is doing all the work. Makes sense
> >> because of the whole user space kernel space thing and I don't really
> >> need both CPU's working on pieces of the same image anyway.
> >>
> >> What I would like though is a way to fork multiple children in the loop
> >> to start additional instances of convert until 4 are active. Then wait
> >> until one exits and then start on the next image. 4 active converts
> >> always until all the images are processed.
> >
>
> I'm sure we've been through this before. Isn't this in the FAQ yet? If
> not, it probably should be.
>
> The easiest way is with parallelized xargs:
>
> $ find . -name '*.jpg' | sed -e 's/.jpg$//' | xargs -P4 -l1 -i
> convert {}.jpg {}.png
>
> The -P flag for xargs is a _wonderful_ thing to learn. Do it now, it
> will forever save you time. I use it daily in our huge farm of linux
> servers, makes for far more bearable adminning.
>
> The other ways (already suggested) are to script something with
> subshells and a queue, or wrap it in a Makefile and use make -j4.
>
> - Ian C. Blenke <ian@blenke.com> <icblenke@nks.net> http://ian.blenke.com/
Ian,
Thanks for the input. I searched my local list history from 2004 for
xargs and only found a few things. I'll read up on it.
Mike
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