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3e9b89d4b5
Changes creating huge diffs, like file splits, have been delayed for readability . Also fix description of `and`.
48 lines
1.2 KiB
Plaintext
48 lines
1.2 KiB
Plaintext
;; FIXME lib/memoize.mal
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;; Memoize any function.
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;; Implement `memoize` using an atom (`mem`) which holds the memoized results
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;; (hash-map from the arguments to the result). When the function is called,
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;; the hash-map is checked to see if the result for the given argument was already
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;; calculated and stored. If this is the case, it is returned immediately;
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;; otherwise, it is calculated and stored in `mem`.
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;; Adapted from http://clojure.org/atoms
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(def! memoize
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(fn* [f]
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(let* [mem (atom {})]
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(fn* [& args]
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(let* [key (str args)]
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(if (contains? @mem key)
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(get @mem key)
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(let* [ret (apply f args)]
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(do
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(swap! mem assoc key ret)
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ret))))))))
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nil
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;; Benchmarks for memoize.mal
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(load-file "../lib/heavy_computations.mal") ; fib
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;; FIXME (load-file "../lib/memoize.mal")
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(load-file "../lib/perf.mal") ; time
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(def! N 32)
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;; Benchmark naive 'fib'
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(println "fib N=" N ": without memoization:")
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(time (fib N))
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;; "Elapsed time: 14402 msecs"
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;; Benchmark memoized 'fib'
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(def! fib (memoize fib))
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(println "fib N=" N ": with memoization:")
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(time (fib N))
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;; "Elapsed time: 1 msecs"
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