[squeak-dev] Is DNU cached?

If
    obj foobar.
looksup #foobar and fails with DNU, will the next
    obj foobar
repeat the foobar, or is the DNU cached so no repeat lookup (unless cache
invalidated)?

Is it likely to be the same in e.g. Gemstone ST?

Thanks - Sophie

On 04.05.2008, at 21:39, itsme213 wrote:

> If
>    obj foobar.
> looksup #foobar and fails with DNU, will the next
>    obj foobar
> repeat the foobar, or is the DNU cached so no repeat lookup (unless  
> cache
> invalidated)?

It is not cached in Squeak.

> Is it likely to be the same in e.g. Gemstone ST?


In general, even if it was "cached", you should be unable to tell.

- Bert -

10 years back I got trapped in a snow storm in Boston, and spent the  
evening exploring the existing caching algorithm for method lookup
which hasn't changed much over the years. I was curious if the  
behavior now (well 10 years back)  was the same as what was documented  
in the Green Book,
and how Morphic affected things.  I found no real difference between  
my numbers and the documented Green Book numbers, so working on the
caching won't buy much.

But, I note you would notice it if you turned caching off.

On May 4, 2008, at 12:39 PM, itsme213 wrote:

--
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John M. McIntosh <[hidden email]>
Corporate Smalltalk Consulting Ltd.  http://www.smalltalkconsulting.com
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Hi Sophie,
 the DNU is cached in the global lookup cache, but not used unless you explicitly send a #doesNotUnderstand: message. (ie: 1 doesNotUnderstand: ....)
 I sent a fix to the list four years ago but it never went to the VM code. The mail is: http://lists.squeakfoundation.org/pipermail/squeak-dev/2004-December/086322.html

 Bye,
 Hernan.