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/
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