On Aug 28, 2009, at 10:57 PM, Chas Emerick wrote:

>
> In the course of doing some profiling tonight, I hit on a hotspot in
> some particularly multimethod- and isa?-heavy code.  It didn't take me
> long to find that the bases and supers support fns for isa? were at
> the root of the issue, with bases in particular taking more time in
> aggregate than the bodies of the multimethods themselves.
>
> A quick fix for this was to memoize bases and supers.  Given that
> these fns are concerned only with Classes (and not the dynamic
> hierarchies, etc), this would seem to be safe in general.

As a quick followup to this, here's a simple macro that folks can use  
to apply this optimization with a minimum of fuss in a given context:

(defmacro with-fast-multimethods
   [& body]
   `(binding [clojure.core/supers (memoize clojure.core/supers)
              clojure.core/bases (memoize clojure.core/bases)]
      ~...@body))

- Chas

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