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POPerformance comparison of immutable string concatenation between Java and Python
 

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  1. POPerformance comparison of immutable string concatenation between Java and Python
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    <p>UPDATES: thanks a lot to Gabe and Glenn for the detailed explanation. The test is wrote not for language comparison benchmark, just for my studying on VM optimization technologies. </p> <p>I did a simple test to understand the performance of string concatenation between Java and Python. </p> <p>The test is target for the default immutable String object/type in both languages. So I don't use StringBuilder/StringBuffer in Java test.</p> <p>The test simply adds strings for 100k times. Java consumes ~32 seconds to finish, while Python only uses ~13 seconds for Unicode string and 0.042 seconds for non Unicode string.</p> <p>I'm a bit surprise about the results. I thought Java should be faster than Python. What optimization technology does Python leverage to achieve better performance? Or String object is designed too heavy in Java?</p> <p>OS: Ubuntu 10.04 x64 JDK: Sun 1.6.0_21 Python: 2.6.5</p> <p>Java test did use -Xms1024m to minimize GC activities.</p> <p>Java code:</p> <pre><code>public class StringConcateTest { public static void test(int n) { long start = System.currentTimeMillis(); String a = ""; for (int i = 0; i &lt; n; i++) { a = a.concat(String.valueOf(i)); } long end = System.currentTimeMillis(); System.out.println(a.length() + ", time:" + (end - start)); } public static void main(String[] args) { for (int i = 0; i &lt; 10; i++) { test(1000 * 100); } } </code></pre> <p>}</p> <p>Python code:</p> <pre><code>import time def f(n): start = time.time() a = u'' #remove u to use non Unicode string for i in xrange(n): a = a + str(i) print len(a), 'time', (time.time() - start)*1000.0 for j in xrange(10): f(1000 * 100) </code></pre>
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    1. COYou have a unhealthy interest in doing things *the wrong way* :p
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      1. USJochen Ritzel
    2. COIf stock Python string are implemented as Java's StringBuffer than I'd expect the results you got. A better test might be to implement the best code on each platform.
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      1. USTony Ennis
    3. COhow did Java do w/ StringBuilder?
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