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POSaturated addition of two signed Java 'long' values
 

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    <p>How can one add two <code>long</code> values in Java so that if the result overflows then it is clamped to the range <code>Long.MIN_VALUE</code>..<code>Long.MAX_VALUE</code>?</p> <p>For adding ints one can perform the arithmetic in <code>long</code> precision and cast the result back to an <code>int</code>, e.g.:</p> <pre><code>int saturatedAdd(int x, int y) { long sum = (long) x + (long) y; long clampedSum = Math.max((long) Integer.MIN_VALUE, Math.min(sum, (long) Integer.MAX_VALUE)); return (int) clampedSum; } </code></pre> <p>or</p> <pre><code>import com.google.common.primitives.Ints; int saturatedAdd(int x, int y) { long sum = (long) x + (long) y; return Ints.saturatedCast(sum); } </code></pre> <p>but in the case of <code>long</code> there is no larger primitive type that can hold the intermediate (unclamped) sum.</p> <p>Since this is Java, I cannot use <a href="https://stackoverflow.com/questions/121240/saturating-addition-in-c">inline assembly</a> (in particular SSE's saturated add instructions.)</p> <p>It can be implemented using <code>BigInteger</code>, e.g.</p> <pre><code>static final BigInteger bigMin = BigInteger.valueOf(Long.MIN_VALUE); static final BigInteger bigMax = BigInteger.valueOf(Long.MAX_VALUE); long saturatedAdd(long x, long y) { BigInteger sum = BigInteger.valueOf(x).add(BigInteger.valueOf(y)); return bigMin.max(sum).min(bigMax).longValue(); } </code></pre> <p>however performance is important so this method is not ideal (though useful for testing.)</p> <p>I don't know whether avoiding branching can significantly affect performance in Java. I assume it can, but I would like to benchmark methods both with and without branching.</p> <p>Related: <a href="https://stackoverflow.com/questions/121240/saturating-addition-in-c">How to do saturating addition in C?</a></p>
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    1. COActually you can use the assembly, provided that you wrap it in JNI, or JNA. It'd be great to see a performance-wise between the proposed solutions.
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