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Evaluation
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Indeed.
Here's a microbenchmark:
import java.util.*;
import java.nio.*;
import java.util.concurrent.*;
import java.util.regex.Pattern;
public class SwapMicroBenchmark {
abstract static class Job {
private final String name;
public Job(String name) { this.name = name; }
public String name() { return name; }
public abstract void work() throws Throwable;
}
private static void collectAllGarbage() {
final java.util.concurrent.CountDownLatch drained
= new java.util.concurrent.CountDownLatch(1);
try {
System.gc(); // enqueue finalizable objects
new Object() { protected void finalize() {
drained.countDown(); }};
System.gc(); // enqueue detector
drained.await(); // wait for finalizer queue to drain
System.gc(); // cleanup finalized objects
} catch (InterruptedException e) { throw new Error(e); }
}
/**
* Runs each job for long enough that all the runtime compilers
* have had plenty of time to warm up, i.e. get around to
* compiling everything worth compiling.
* Returns array of average times per job per run.
*/
private static long[] time0(Job ... jobs) throws Throwable {
final long warmupNanos = 10L * 1000L * 1000L * 1000L;
long[] nanoss = new long[jobs.length];
for (int i = 0; i < jobs.length; i++) {
collectAllGarbage();
long t0 = System.nanoTime();
long t;
int j = 0;
do { jobs[i].work(); j++; }
while ((t = System.nanoTime() - t0) < warmupNanos);
nanoss[i] = t/j;
}
return nanoss;
}
private static void time(Job ... jobs) throws Throwable {
long[] warmup = time0(jobs); // Warm up run
long[] nanoss = time0(jobs); // Real timing run
long[] milliss = new long[jobs.length];
double[] ratios = new double[jobs.length];
final String nameHeader = "Method";
final String millisHeader = "Millis";
final String ratioHeader = "Ratio";
int nameWidth = nameHeader.length();
int millisWidth = millisHeader.length();
int ratioWidth = ratioHeader.length();
for (int i = 0; i < jobs.length; i++) {
nameWidth = Math.max(nameWidth, jobs[i].name().length());
milliss[i] = nanoss[i]/(1000L * 1000L);
millisWidth = Math.max(millisWidth,
String.format("%d", milliss[i]).length());
ratios[i] = (double) nanoss[i] / (double) nanoss[0];
ratioWidth = Math.max(ratioWidth,
String.format("%.3f", ratios[i]).length());
}
String format = String.format("%%-%ds %%%dd %%%d.3f%%n",
nameWidth, millisWidth, ratioWidth);
String headerFormat = String.format("%%-%ds %%%ds %%%ds%%n",
nameWidth, millisWidth, ratioWidth);
System.out.printf(headerFormat, "Method", "Millis", "Ratio");
// Print out absolute and relative times, calibrated against first job
for (int i = 0; i < jobs.length; i++)
System.out.printf(format, jobs[i].name(), milliss[i], ratios[i]);
}
private static String keywordValue(String[] args, String keyword) {
for (String arg : args)
if (arg.startsWith(keyword))
return arg.substring(keyword.length() + 1);
return null;
}
private static int intArg(String[] args, String keyword, int defaultValue) {
String val = keywordValue(args, keyword);
return val == null ? defaultValue : Integer.parseInt(val);
}
private static Pattern patternArg(String[] args, String keyword) {
String val = keywordValue(args, keyword);
return val == null ? null : Pattern.compile(val);
}
private static Job[] filter(Pattern filter, Job[] jobs) {
if (filter == null) return jobs;
Job[] newJobs = new Job[jobs.length];
int n = 0;
for (Job job : jobs)
if (filter.matcher(job.name()).find())
newJobs[n++] = job;
// Arrays.copyOf not available in JDK 5
Job[] ret = new Job[n];
System.arraycopy(newJobs, 0, ret, 0, n);
return ret;
}
private static void deoptimize(int sum) {
if (sum == 42)
System.out.println("the answer");
}
/**
* Usage: [iterations=N] [size=N] [filter=REGEXP]
*/
public static void main(String[] args) throws Throwable {
final int iterations = intArg(args, "iterations", 10000);
final int size = intArg(args, "size", 1024);
final Pattern filter = patternArg(args, "filter");
final Random rnd = new Random();
final ByteBuffer b = ByteBuffer.allocateDirect(8*size);
for (int i = 0; i < b.limit(); i++)
b.put(i, (byte) rnd.nextInt());
Job[] jobs = {
new Job("swap char BIG_ENDIAN") {
public void work() throws Throwable {
b.order(ByteOrder.BIG_ENDIAN);
CharBuffer x = b.asCharBuffer();
for (int i = 0; i < iterations; i++) {
int sum = 0;
for (int j = 0, end = x.limit(); j < end; j++)
sum += x.get(j);
deoptimize(sum);}}},
new Job("swap char LITTLE_ENDIAN") {
public void work() throws Throwable {
b.order(ByteOrder.LITTLE_ENDIAN);
CharBuffer x = b.asCharBuffer();
for (int i = 0; i < iterations; i++) {
int sum = 0;
for (int j = 0, end = x.limit(); j < end; j++)
sum += x.get(j);
deoptimize(sum);}}},
new Job("swap short BIG_ENDIAN") {
public void work() throws Throwable {
b.order(ByteOrder.BIG_ENDIAN);
ShortBuffer x = b.asShortBuffer();
for (int i = 0; i < iterations; i++) {
int sum = 0;
for (int j = 0, end = x.limit(); j < end; j++)
sum += x.get(j);
deoptimize(sum);}}},
new Job("swap short LITTLE_ENDIAN") {
public void work() throws Throwable {
b.order(ByteOrder.LITTLE_ENDIAN);
ShortBuffer x = b.asShortBuffer();
for (int i = 0; i < iterations; i++) {
int sum = 0;
for (int j = 0, end = x.limit(); j < end; j++)
sum += x.get(j);
deoptimize(sum);}}},
new Job("swap int BIG_ENDIAN") {
public void work() throws Throwable {
b.order(ByteOrder.BIG_ENDIAN);
IntBuffer x = b.asIntBuffer();
for (int i = 0; i < iterations; i++) {
int sum = 0;
for (int j = 0, end = x.limit(); j < end; j++)
sum += x.get(j);
deoptimize(sum);}}},
new Job("swap int LITTLE_ENDIAN") {
public void work() throws Throwable {
b.order(ByteOrder.LITTLE_ENDIAN);
IntBuffer x = b.asIntBuffer();
for (int i = 0; i < iterations; i++) {
int sum = 0;
for (int j = 0, end = x.limit(); j < end; j++)
sum += x.get(j);
deoptimize(sum);}}},
new Job("swap long BIG_ENDIAN") {
public void work() throws Throwable {
b.order(ByteOrder.BIG_ENDIAN);
LongBuffer x = b.asLongBuffer();
for (int i = 0; i < iterations; i++) {
int sum = 0;
for (int j = 0, end = x.limit(); j < end; j++)
sum += x.get(j);
deoptimize(sum);}}},
new Job("swap long LITTLE_ENDIAN") {
public void work() throws Throwable {
b.order(ByteOrder.LITTLE_ENDIAN);
LongBuffer x = b.asLongBuffer();
for (int i = 0; i < iterations; i++) {
int sum = 0;
for (int j = 0, end = x.limit(); j < end; j++)
sum += x.get(j);
deoptimize(sum);}}}
};
time(filter(filter, jobs));
}
}
with results on sparc:
for f in -client -server; do mergeBench dolphin redundant jr -dsa -da $f SwapMicroBenchmark.java filter=LITTLE; done
==> javac -Xlint:all SwapMicroBenchmark.java
==> java -dsa -da -client SwapMicroBenchmark filter=LITTLE
Method Millis Ratio vs. dolphin
swap char LITTLE_ENDIAN 1736 1.000 0.974
swap short LITTLE_ENDIAN 1827 1.052 1.025
swap int LITTLE_ENDIAN 959 0.553 0.823
swap long LITTLE_ENDIAN 836 0.482 0.787
Merged results for dolphin vs. redundant running jr -dsa -da -server SwapMicroBenchmark.java filter=LITTLE
==> javac -Xlint:all SwapMicroBenchmark.java
==> java -dsa -da -server SwapMicroBenchmark filter=LITTLE
Method Millis Ratio vs. dolphin
swap char LITTLE_ENDIAN 172 1.000 1.000
swap short LITTLE_ENDIAN 195 1.133 0.920
swap int LITTLE_ENDIAN 132 0.769 0.608
swap long LITTLE_ENDIAN 183 1.063 0.729
and on x86:
for f in -client -server; do mergeBench dolphin redundant jr -dsa -da $f SwapMicroBenchmark.java filter=BIG; done
Merged results for dolphin vs. redundant running jr -dsa -da -client SwapMicroBenchmark.java filter=BIG
==> javac -Xlint:all SwapMicroBenchmark.java
==> java -dsa -da -client SwapMicroBenchmark filter=BIG
Method Millis Ratio vs. dolphin
swap char BIG_ENDIAN 628 1.000 1.000
swap short BIG_ENDIAN 655 1.043 0.997
swap int BIG_ENDIAN 328 0.522 0.924
swap long BIG_ENDIAN 234 0.373 0.893
Merged results for dolphin vs. redundant running jr -dsa -da -server SwapMicroBenchmark.java filter=BIG
==> javac -Xlint:all SwapMicroBenchmark.java
==> java -dsa -da -server SwapMicroBenchmark filter=BIG
Method Millis Ratio vs. dolphin
swap char BIG_ENDIAN 69 1.000 1.000
swap short BIG_ENDIAN 81 1.166 0.835
swap int BIG_ENDIAN 49 0.702 0.681
swap long BIG_ENDIAN 73 1.056 0.658
Posted Date : 2007-08-13 00:28:16.0
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