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/* |
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* Written by Doug Lea with assistance from members of JCP JSR-166 |
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* Expert Group and released to the public domain, as explained at |
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* http://creativecommons.org/licenses/publicdomain |
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*/ |
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|
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import java.util.*; |
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|
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/** |
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* Estimates time per iteration of collection iterators. Preloads |
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* most elements, but adds about 1/8 of them dynamically to preclude |
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* overly clever optimizations. The array of collections has |
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* approximately exponentially different lengths, so chek both short |
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* and long iterators. Reports include times for adds and other |
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* checks, so overestimate times per iteration. |
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*/ |
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|
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public final class IteratorLoops { |
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static final int DEFAULT_SIZE = 16384; |
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static final int DEFAULT_TRIALS = 2; |
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static final int NC = 16; // number of collections must be power of 2 |
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static volatile long mismatches = 0; |
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static int randomSeed = 3122688; |
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|
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public static void main(String[] args) throws Exception { |
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Class klass = Class.forName(args[0]); |
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int n = (args.length <= 1)? DEFAULT_SIZE : Integer.parseInt(args[1]); |
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int t = (args.length <= 2)? DEFAULT_TRIALS : Integer.parseInt(args[2]); |
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|
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System.out.print("Class: " + klass.getName()); |
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System.out.print(" ~iters: " + (long)n * (long)n); |
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System.out.print(" trials: " + t); |
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System.out.println(); |
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|
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Collection<Integer>[] colls = |
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(Collection<Integer>[])new Collection[NC]; |
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|
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for (int k = 0; k < colls.length; ++k) |
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colls[k] = (Collection<Integer>)klass.newInstance(); |
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|
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for (int i = 0; i < t; ++i) |
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new IteratorLoops(colls).oneRun(n); |
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|
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if (mismatches != 0) |
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throw new Error("Bad checksum :" + mismatches); |
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} |
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|
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private int elementCount; |
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private final Collection<Integer>[] cs; |
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|
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IteratorLoops(Collection<Integer>[] colls) { |
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cs = colls; |
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elementCount = 0; |
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} |
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|
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void oneRun(int n) { |
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preload(n); |
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long startTime = System.nanoTime(); |
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long count = traversals(n); |
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double elapsed = (double)(System.nanoTime() - startTime); |
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double npi = elapsed / count; |
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double secs = elapsed / 1000000000; |
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System.out.printf("%7.1f ns/iter %8.3fs run time\n", npi, secs); |
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} |
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|
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long traversals(int n) { |
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long count = 0; |
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long check = 0; |
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for (int i = 0; i < n; i++) { |
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check += elementCount; |
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count += counts(); |
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maybeAdd(); |
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} |
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if (count != check) |
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mismatches = count; |
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return count; |
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} |
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|
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int counts() { |
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int count = 0; |
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for (int k = 0; k < cs.length; ++k) { |
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for (Iterator it = cs[k].iterator(); it.hasNext();) { |
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if (it.next() != null) |
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++count; |
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} |
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} |
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return count; |
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} |
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|
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void maybeAdd() { |
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int r = randomSeed; |
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r ^= r << 6; |
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r ^= r >>> 21; |
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r ^= r << 7; |
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randomSeed = r; |
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if ((r >>> 29) == 0) |
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cs[r & (cs.length-1)].add(new Integer(elementCount++)); |
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} |
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|
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void preload(int n) { |
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for (int i = 0; i < cs.length; ++i) |
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cs[i].clear(); |
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int k = (n - n / 8) / 2; |
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ArrayList<Integer> al = new ArrayList<Integer>(k+1); |
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for (int i = 0; i < cs.length; ++i) { |
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if (k > 0) { |
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for (int j = 0; j < k; ++j) |
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al.add(new Integer(elementCount++)); |
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cs[i].addAll(al); |
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al.clear(); |
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} |
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k >>>= 1; |
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} |
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// let GC settle down |
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try { Thread.sleep(500); } catch(Exception ex) { return; } |
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} |
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|
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|
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} |
