Re: task-safe hash table?

[tmoran@acm.org]

> > I think you might be able to get part way by consulting the original
> > Booch components.
>
> The 95 BCs were going to have Synchronized and Guarded extensions, but
   The app I had in mind was the k-nucleotide shootout benchmark, which
uses a hash table, running on a multi-core cpu.  If lookups are read-only,
and are much more frequent than writes, one should be able to do them
concurrently.  Since a lookup in a hash table is, presumably, pretty fast,
the overhead of making it Protected would probably kill the gain.  But one
ought to be able to arrange things so a concurrent lookup that comes back
with a hit is correct, ie most of the time, while one that comes back "we
need to add this" would be rare enough that interlocking for a second
check and possible add wouldn't cancel the wall clock savings.  So this
is a very specific test to see what Ada tasking, on a modern chip, buys
you on this particular app.  (I already know it's a win on the word count
and on a sort.) I'm just hearing too many people say "multi-core is dumb
because nobody knows how to do concurrent programming".