On Fri, Apr 13, 2012 at 2:24 PM, Nathaniel Smith <n...@pobox.com> wrote: > On Fri, Apr 13, 2012 at 9:27 PM, Dag Sverre Seljebotn > <d.s.seljeb...@astro.uio.no> wrote: >> Ah, I didn't think about 6-bit or huffman. Certainly helps. >> >> I'm almost +1 on your proposal now, but a couple of more ideas: >> >> 1) Let the key (the size_t) spill over to the next specialization entry if >> it is too large; and prepend that key with a continuation code (two size-ts >> could together say "iii)-d\0\0" on 32 bit systems with 8bit encoding, using >> - as continuation). The key-based caller will expect a continuation if it >> knows about the specialization, and the prepended char will prevent spurios >> matches against the overspilled slot. >> >> We could even use the pointers for part of the continuation... > > I am really lost here. Why is any of this complicated encoding stuff > better than interning? Interning takes one line of code, is incredibly > cheap (one dict lookup per call site and function definition), and it > lets you check any possible signature (even complicated ones involving > memoryviews) by doing a single-word comparison. And best of all, you > don't have to think hard to make sure you got the encoding right. ;-) > > On a 32-bit system, pointers are smaller than a size_t, but more > expressive! You can still do binary search if you want, etc. Is the > problem just that interning requires a runtime calculation? Because I > feel like C users (like numpy) will want to compute these compressed > codes at module-init anyway, and those of us with a fancy compiler > capable of computing them ahead of time (like Cython) can instruct > that fancy compiler to compute them at module-init time just as > easily?
Good question. The primary disadvantage of interning that I see is memory locality. I suppose if all the C-level caches of interned values were co-located, this may not be as big of an issue. Not being able to compare against compile-time constants may thwart some optimization opportunities, but that's less clear. It also requires coordination common repository, but I suppose one would just stick a set in some standard module (or leverage Python's interning). - Robert _______________________________________________ cython-devel mailing list cython-devel@python.org http://mail.python.org/mailman/listinfo/cython-devel
