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POPort of Random generator from C to Java?
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  1. POPort of Random generator from C to Java?
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    copied!<p>George Marsaglia has written an excellent random number generator that is extremely fast, simple, and has a much higher period than the Mersenne Twister. Here is the code with a description:</p> <p><a href="http://school.anhb.uwa.edu.au/personalpages/kwessen/shared/Marsaglia03.html" rel="noreferrer">good C random number generator</a></p> <p>I wanted to port the CMWC4096 code to Java, but it uses several unsigned datatypes so I am not sure how to do this properly. Here is the full C code:</p> <pre><code>/* choose random initial c&lt;809430660 and */ /* 4096 random 32-bit integers for Q[] */ static unsigned long Q[4096],c=362436; unsigned long CMWC4096(void) { unsigned long long t, a=18782LL; static unsigned long i=4095; unsigned long x,r=0xfffffffe; i = (i+1) &amp; 4095; t = a*Q[i] + c; c = (t&gt;&gt;32); x = t + c; if (x &lt; c) { x++; c++; } return (Q[i] = r - x); } </code></pre> <p>Can anyone port this to Java? How does this work when you only have signed numbers available?</p> <p><strong>EDIT:</strong> Thanks everybody for the quick answers! For the first 100 million numbers this java code seems to produce the same result as the C code. It is 3 times faster than Java's java.util.Random.</p> <pre><code>public class ComplimentaryMultiplyWithCarryRandom { /** * Choose 4096 random 32-bit integers */ private long[] Q; /** * choose random initial c&lt;809430660 */ private long c = 362436; private int i; public ComplimentaryMultiplyWithCarryRandom() { Random r = new Random(1); Q = new long[4096]; // TODO initialize with real random 32bit values for (int i = 0; i &lt; 4096; ++i) { long v = r.nextInt(); v -= Integer.MIN_VALUE; Q[i] = v; } i = 4095; } int next() { i = (i + 1) &amp; 4095; long t = 18782 * Q[i] + c; c = t &gt;&gt;&gt; 32; long x = (t + c) &amp; 0xffffffffL; if (x &lt; c) { ++x; ++c; } long v = 0xfffffffeL - x; Q[i] = v; return (int) v; } } </code></pre>
 

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