ReduceTask::closestPowerOf2 is inefficient
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Key: HADOOP-3398
URL: https://issues.apache.org/jira/browse/HADOOP-3398
Project: Hadoop Core
Issue Type: Bug
Components: mapred
Reporter: Chris Douglas
Priority: Trivial
Fix For: 0.18.0
Attachments: 3398-0.patch
ReduceTask computes the "closest power of 2" using loops
{code}
private static int getClosestPowerOf2(int value) {
final int hob = Integer.highestOneBit(value);
return Integer.numberOfTrailingZeros(hob) +
Math.min((hob >>> 1) & value, 1);
int power = 0;
int approx = 1;
while (approx < value) {
++power;
approx = (approx << 1);
}
if ((value - (approx >> 1)) < (approx - value)) {
--power;
}
return power;
}
{code}
This could be improved.
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