[Vm-dev] VM packaging for Cog transition

[David T. Lewis]

Bert and others have raised the question of how best to package the
Cog VM and traditional interpreter VM for the next round of VM releases
in December. Cog is a significant advance, and the Squeak board would
like this to be fully supported for the Squeak 4.2 release; clearly it
is a priority for Pharo as well. Meanwhile we have a responsibility for
Etoys, Scratch, OLPC etc to provide VMs that do not break those systems.

So - how best to do this?

For unix VMs, Bert has suggested this:

> Maybe we need a "squeak-interp" and "squeak-cog" binary, with "squeak"
> symlinking to either one (using the alternatives system) or "squeak"
> being a script choosing the right VM based on the image version. But
> we should present a coherent story to the packagers. As well as to
> Squeak users.

Personally I am inclined to think it would be best for this next release
not to automate the selection of VM, but instead have users make an
explicit selection. I say this for two reasons:

1) From a marketing point of view, it is good if users can directly experience
the improvement from Cog. So the message might be to first run in the standard
way (squeak-interp) to get a very cool system that is quite fast, then activate
turbo mode (squeak-cog) to get a system that is very noticeably 3X faster.

2) From a technical and support point of view, there may be various cases
where it will be necessary to say "sorry, you will need to run squeak-interp
if you want to do that." When that happens, it would be best if we do not need
to explain e.g. how to edit a shell script to force it to run squeak-interp.

The above is just my $.02 to get the discussion started. What do others think?

Dave