[firstname.lastname@example.org: Re: PEGs]
dave.long at bluewin.ch
Thu Jan 1 10:51:16 EST 2009
> One approach to implementing this, which I've also been thinking of
> maintaining Bicicleta intermediate results, would be to use a value-
> hashtable for the memoization table, along with a garbage collector.
> Any value that is needed again while it's still in the nursery will
> need to be recomputed, but most values will be reaped because at the
> time of the next minor collection, the only reference to them will
> be in
> the value-weak hashtable. A few won't be --- the ones whose values
> currently referenced from some parsing rule currently being tried ---
> and those will be promoted.
> I think this design may be useful for laziness in general, but I
> tried it yet, despite having come up with it a year or two ago.
A design that I'd like to try sometime would be to try an "Elephant"-
like language, in which all values would, in principle, be
recoverable from a logfile. This could eliminate GC, as frequently
used values would tend to be instantiated in a cache, and values that
are never referenced again would cost just their portion of storage,
presumably amortized by bulk sequential i/o patterns.
Any idea how mutation rates compare for various workloads with main
memory and/or disk bandwidths?
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