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;; The Computer Language Benchmarks Game
;; contributed by Andy Fingerhut
;; The function 'dot' is based on suggestions and improvements made by
;; these people posting to the Clojure Google group in April, 2009:
;; dmitri.sotnikov, William D. Lipe, Paul Stadig, michael.messinides
;; David Sletten, John Harrop
;; change by Marko Kocic
;; reduced code size by removing functions already present in Clojure
;; change by Andy Fingerhut
;; Use Java primitive double arrays instead of Clojure sequences in a
;; few inner loops. This is a parallel version, identical to the
;; sequential version except using pmap in compute-rows.
(ns mandelbrot
(:import ( BufferedOutputStream)))
(set! *warn-on-reflection* true)
;; Handle slight difference in function name between Clojure 1.2.0 and
;; 1.3.0-alpha* ability to use type hints to infer fast bit
;; operations.
(defmacro my-unchecked-add-int [& args]
(if (and (== (*clojure-version* :major) 1)
(== (*clojure-version* :minor) 2))
`(unchecked-add ~@args)
`(unchecked-add-int ~@args)))
(defmacro my-unchecked-dec-int [& args]
(if (and (== (*clojure-version* :major) 1)
(== (*clojure-version* :minor) 2))
`(unchecked-dec ~@args)
`(unchecked-dec-int ~@args)))
(defmacro my-unchecked-divide-int [& args]
(if (and (== (*clojure-version* :major) 1)
(== (*clojure-version* :minor) 2))
`(unchecked-divide ~@args)
`(unchecked-divide-int ~@args)))
(defmacro my-unchecked-inc-int [& args]
(if (and (== (*clojure-version* :major) 1)
(== (*clojure-version* :minor) 2))
`(unchecked-inc ~@args)
`(unchecked-inc-int ~@args)))
(def max-iterations 50)
(def limit-square (double 4.0))
(defn dot [r i]
(let [f2 (double 2.0)
limit-square (double limit-square)
iterations-remaining (int max-iterations)
pr (double r)
pi (double i)]
;; The loop below is similar to the one in the Perl subroutine dot
;; in mandelbrot.perl, with these name correspondences:
;; pr <-> Cr, pi <-> Ci, zi <-> Zi, zr <-> Zr, zr2 <-> Tr, zi2 <-> Ti
(loop [zr (double 0.0)
zi (double 0.0)
i (int (my-unchecked-inc-int iterations-remaining))]
(let [zr2 (* zr zr)
zi2 (* zi zi)]
(if (and (not (zero? i))
(< (+ zr2 zi2) limit-square))
(recur (+ (- zr2 zi2) pr)
(+ (* (* f2 zr) zi) pi)
(my-unchecked-dec-int i))
(zero? i))))))
(defn index-to-val [i scale-fac offset]
(+ (* i scale-fac) offset))
(defn ubyte [val]
(if (>= val 128)
(byte (- val 256))
(byte val)))
(defn compute-row [#^doubles x-vals y]
(let [y (double y)
n (int (alength x-vals))
num-bytes-out (int (my-unchecked-divide-int (my-unchecked-add-int n 7) 8))
#^bytes result (byte-array num-bytes-out)
zero (int 0)
one (int 1)]
(loop [i (int zero)
b (int zero)
num-filled-bits zero
result-idx (int zero)]
(if (== i n)
(when (not (zero? num-filled-bits))
(let [last-byte-val
(byte (ubyte (bit-shift-left b (- 8 num-filled-bits))))]
(aset result result-idx last-byte-val)))
;; else
(let [new-bit (int (if (dot (aget x-vals i) y) one zero))
new-b (int (my-unchecked-add-int (bit-shift-left b one) new-bit))]
(if (== num-filled-bits 7)
(let [byte-val (byte (ubyte new-b))]
(aset result result-idx byte-val)
(recur (my-unchecked-inc-int i)
(my-unchecked-inc-int result-idx)))
(recur (my-unchecked-inc-int i)
(my-unchecked-inc-int num-filled-bits)
(defn compute-rows [size]
(let [two-over-size (double (/ 2.0 size))
x-offset (double -1.5)
y-offset (double -1.0)
x-vals (double-array size (map #(index-to-val % two-over-size x-offset)
(range size)))
y-vals (double-array size (map #(index-to-val % two-over-size y-offset)
(range size)))]
(pmap #(compute-row x-vals (aget y-vals %))
(range size))))
(defn do-mandelbrot [size]
(let [rows (compute-rows size)]
(printf "P4\n")
(printf "%d %d\n" size size)
(let [ostream (BufferedOutputStream. System/out)]
(doseq [r rows]
(. ostream write r 0 (count r)))
(. ostream close))
(defn -main [& args]
(let [size (. Integer valueOf (nth args 0) 10)]
(do-mandelbrot size)