[squeak-dev] Multiple Images executing simultaneously

Peter Crowther peter at ozzard.org
Wed Sep 21 11:06:22 UTC 2016

Squeak is single-threaded, and I don't expect that to change as too much in
the image relies on it.  Therefore, assuming your simulation is CPU-bound
(pretty much a given for most neural network work), you should be able to
run about as many Squeak images as you have threads on your processor.
There are a few nuances to that - Intel hyperthreading causing contention
for parts of cores, CPU cache size and hence bandwidth to/from RAM, that
kind of thing - but it mostly works.

Incidentally, this behaviour isn't specific to Squeak or to a particular
version of MacOS, and it's not a happy accident.  Processor designers and
operating system developers have spent many years making sure this
happens.  The same thing would probably be true for any other
single-threaded CPU-limited code you wrote and ran, on any "modern" (last
20 years) OS.  So it's pretty safe to rely on it.


- Peter

On 19 September 2016 at 19:31, Andrew Coward <landrewcoward at shaw.ca> wrote:

> I am using the all-in-one image to carry out neural network simulations
> with different parameters using a MacBook Pro 2 GHx Intel Core i7 with OSX
> 10.11.6. Each simulation can take up to 36 hours to complete.
> I have found it is possible to have 7 or more different images all
> executing at the same time. Each image runs at the same speed as when only
> one image is running. Obviously a huge benefit.
> This works in either Smalltalk 4.4 or 5.0.
> Each image has a different name, and one oddity is that sometimes when
> opening an image I get the message “cannot find application”. However,
> changing the name of the image, for example by inserting spaces at the end,
> eventually gets to an image that will open (so far 1 to 4 spaces have
> always been sufficient).
> Does anyone know if this ability to run multiple images is a “happy
> accident”  or an intended feature of Smalltalk that will be preserved in
> future releases of Smalltalk and OS ?
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