On 18/01/2013 6:29 AM, David Barbour wrote:
> It seems controlling use of local state is important if we both want
> rich abstraction - i.e. where composite networks can be abstracted - and
> live programming.
There are models that can deal with systems only involving local state
(eg. the Actor model).
max.msp provides a reasonable example of the utility of this for live
programming.
> (cf.
> http://awelonblue.wordpress.com/2012/10/21/local-state-is-poison/)
From the post:
"""If you think global shared state is bad, you’re doing it wrong. To
achieve large scale, robust, resilient, maintainable, extensible,
eternal systems, we must transition away from local state and shove
essential state into global, shared spaces where it can be represented
independently of program logic."""
The problem with the position taken by that post is that it assumes an
absolutist model of the world, which according to current scientific
opinion is not realistic. There is only local state and local time.
On a single CPU you can pretend that you're in an absolutist universe,
but in distributed concurrent systems that's not the case (even the ones
involving 4 cores in your laptop). Trying to pretend that global state
exists by forcing it through a "persistent substrate" just creates a
bottleneck. Of course there are pragmatic reasons to do this sometimes,
but to suggest that this is the way forward seems misguided to me.
Ross.
Received on Thu Jan 17 2013 - 20:43:27 GMT