Threading Question

[fmw42]

I am curious, in a script, if I want just one convert command to use 1 thread, is there any difference between

MAGICK_THREAD_LIMIT=1 convert ....

and

convert -limit thread 1 ....

Is the former limited to that one convert command or does it continue to the rest of the script?

[magick]

There is no difference. Both set the thread resource limit to 1 such that all algorithms in ImageMagick run in a single thread regardless of the number of cores the host supports.

[fmw42]

But are both limited to one command line within a script?

[anthony]

Unless you actually 'export' the MAGICK_THREAD_LIMIT setting then it will only effect the command it is attached to.

That is

Code: Select all

  MAGICK_THREAD_LIMIT=1
  convert ....

will not effect convert

Code: Select all

  MAGICK_THREAD_LIMIT=1 convert ...
  convert ...

will only effect the first convert

While

Code: Select all

  export MAGICK_THREAD_LIMIT=1
  convert ...

or

Code: Select all

MAGICK_THREAD_LIMIT=1
export MAGICK
convert ....

effects every convert command that follows.

Using the option -limit thread 1 will only effect operations that follow it.

However their is no +limit (reset setting) form for this setting. One of the few setting without a + reset form. You can however either give it a 'number' or the string "unlimited". Though if that is the right 'reset' value for 'thread' I have no idea.