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estimated_histogram: Implement percentile()

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This commit is contained in:
Tomasz Grabiec
2017-07-26 12:22:07 +02:00
parent 1bc305ed7b
commit 5602be72fa
1 changed files with 16 additions and 18 deletions
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34
utils/estimated_histogram.hh
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@@ -280,34 +280,32 @@ public:
}
return 0;
}
#endif
/**
* @param percentile
* @return estimated value at given percentile
*/
public long percentile(double percentile)
{
assert percentile >= 0 && percentile <= 1.0;
int lastBucket = buckets.length() - 1;
if (buckets.get(lastBucket) > 0)
throw new IllegalStateException("Unable to compute when histogram overflowed");
int64_t percentile(double perc) const {
assert(perc >= 0 && perc <= 1.0);
auto last_bucket = buckets.size() - 1;
if (buckets[last_bucket] > 0) {
throw std::runtime_error("Unable to compute when histogram overflowed");
}
long pcount = (long) Math.floor(count() * percentile);
if (pcount == 0)
return 0;
long elements = 0;
for (int i = 0; i < lastBucket; i++)
{
elements += buckets.get(i);
if (elements >= pcount)
return bucketOffsets[i];
auto pcount = int64_t(std::floor(count() * perc));
int64_t elements = 0;
for (size_t i = 0; i < last_bucket; i++) {
if (buckets[i]) {
elements += buckets[i];
if (elements >= pcount) {
return bucket_offsets[i];
}
}
}
return 0;
}
#endif
/**
* @return the mean histogram value (average of bucket offsets, weighted by count)
*/