Hi,
At some point in time I needed to handle lzw compressing/uncompressing in the client so I found https://gist.github.com/revolunet/843889 Chrome Firefox IE
Js 544/61 626/78 795/171The numbers are compressing/uncompressing
1000 iterations with a random string multiplied 10 times
1000 iterations with a random string multiplied 10 times
I am using a single permutation with collapse-all. Can this be the culprit?
Any idea what to change in order to increase the performance in the java code?
Here is the code
package com.biovista.lib.gwt.client;
import com.google.gwt.core.client.JavaScriptObject;
public class Util {
private static final char DICT_SIZE = 256;
public static class JsMap<T> extends JavaScriptObject {
protected JsMap() {
}
public final native void put(String key, T value) /*-{
this[key] = value;
}-*/;
public final native boolean containsKey(String key) /*-{
return (key in this);
}-*/;
public final native T get(String key) /*-{
return this[key];
}-*/;
public static JsMap createInstance() {
return (JsMap) createObject();
}
}
public static class JsList<T> extends JavaScriptObject {
protected JsList() {
}
public final native void add(T value) /*-{
this.push(value);
}-*/;
public final native int size() /*-{
return this.length;
}-*/;
public final native T get(char index) /*-{
return this[index];
}-*/;
public static JsList createInstance() {
return (JsList) createArray();
}
}
public static String compressLZW(String text) {
// Build the dictionary.
// final Map<String, Character> map = new HashMap<String, Character>(
// DICT_SIZE);
final JsMap<Character> map = JsMap.createInstance();
for (char i = 0; i < DICT_SIZE; i++) {
map.put("" + i, i);
}
char dict_size = DICT_SIZE;
String w = "";
final StringBuilder result = new StringBuilder();
for (char c : text.toCharArray()) {
final String wc = w + c;
if (map.containsKey(wc))
w = wc;
else {
result.append(map.get(w));
// Add wc to the dictionary.
map.put(wc, dict_size++);
w = "" + c;
}
}
// Output the code for w.
if (!w.equals(""))
result.append(map.get(w));
return result.toString();
}
/** uncompress a string. */
public static String uncompressLZW(String compressed_text) {
// Build the dictionary.
// final List<String> rmap = new ArrayList<String>(DICT_SIZE);
final JsList<String> rmap = JsList.createInstance();
for (char i = 0; i < DICT_SIZE; i++) {
rmap.add("" + i);
}
final char[] compressed = compressed_text.toCharArray();
String w = "" + compressed[0];
final StringBuilder result = new StringBuilder(w);
for (int i = 1; i < compressed.length; i++) {
final char k = compressed[i];
final String entry = k < rmap.size() ? rmap.get(k) : w
+ w.charAt(0);
result.append(entry);
// Add w+entry[0] to the dictionary.
rmap.add(w + entry.charAt(0));
w = entry;
}
return result.toString();
}
// LZW-compress a string
public static native String lzwCompress(String s) /*-{
var dict = {};
var data = (s + "").split("");
var out = [];
var currChar;
var phrase = data[0];
var code = 256;
for (var i = 1; i < data.length; i++) {
currChar = data[i];
if (dict[phrase + currChar] != null) {
phrase += currChar;
} else {
out.push(phrase.length > 1 ? dict[phrase] : phrase
.charCodeAt(0));
dict[phrase + currChar] = code;
code++;
phrase = currChar;
}
}
out.push(phrase.length > 1 ? dict[phrase] : phrase.charCodeAt(0));
for (var i = 0; i < out.length; i++) {
out[i] = String.fromCharCode(out[i]);
}
return out.join("");
}-*/;
// Decompress an LZW-encoded string
public static native String lzwDecompress(String s) /*-{
var dict = {};
var data = (s + "").split("");
var currChar = data[0];
var oldPhrase = currChar;
var out = [ currChar ];
var code = 256;
var phrase;
for (var i = 1; i < data.length; i++) {
var currCode = data[i].charCodeAt(0);
if (currCode < 256) {
phrase = data[i];
} else {
phrase = dict[currCode] ? dict[currCode]
: (oldPhrase + currChar);
}
out.push(phrase);
currChar = phrase.charAt(0);
dict[code] = oldPhrase + currChar;
code++;
oldPhrase = phrase;
}
return out.join("");
}-*/;
public static void benchmark() {
final int N = 1000;
final int M = 10;
final String test1 = "opaopaopaopa236747862348 hfjsgfhjsd g4782q65 87324658764 8 37g fj hdshfjdhjsb hjsgfbhjgb hjdf sjjhsgd 87345y 783256 8736 8573587 68327563";
String test = "";
for (int i = 0; i < M; i++) {
test += test1;
}
// log.info("old compress " + lzwCompress(test));
// log.info("new compress " + compressLZW(test));
// log.info("old uncompress " + lzwDecompress(lzwCompress(test)));
// log.info("new uncompress " + uncompressLZW(compressLZW(test)));
long t1 = System.currentTimeMillis();
for (int i = 0; i < N; i++) {
lzwCompress(test);
}
long t2 = System.currentTimeMillis();
for (int i = 0; i < N; i++) {
compressLZW(test);
}
long t3 = System.currentTimeMillis();
log.info("Compressing: old " + (t2 - t1) + " vs new " + (t3 - t2));
final String test_c = compressLZW(test);
t1 = System.currentTimeMillis();
for (int i = 0; i < N; i++) {
lzwDecompress(test_c);
}
t2 = System.currentTimeMillis();
for (int i = 0; i < N; i++) {
uncompressLZW(test_c);
}
t3 = System.currentTimeMillis();
log.info("UnCompressing: old " + (t2 - t1) + " vs new " + (t3 - t2));
if (!(lzwDecompress(lzwCompress(test)).equals(test))) {
log.error("old failure");
}
if (!(uncompressLZW(compressLZW(test)).equals(test))) {
log.error("new failure");
}
}
}
--
Vassilis Virvilis
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