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38 lines
1.2 KiB
Scala
38 lines
1.2 KiB
Scala
package com.twitter.ann.common
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import com.twitter.util.Return
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import com.twitter.util.Throw
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import com.twitter.util.Try
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import com.twitter.util.logging.Logging
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// Memoization with a twist
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// New epoch reuse K:V pairs from previous and recycle everything else
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class MemoizedInEpochs[K, V](f: K => Try[V]) extends Logging {
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private var memoizedCalls: Map[K, V] = Map.empty
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def epoch(keys: Seq[K]): Seq[V] = {
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val newSet = keys.toSet
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val keysToBeComputed = newSet.diff(memoizedCalls.keySet)
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val computedKeysAndValues = keysToBeComputed.map { key =>
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info(s"Memoize ${key}")
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(key, f(key))
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}
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val keysAndValuesAfterFilteringFailures = computedKeysAndValues
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.flatMap {
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case (key, Return(value)) => Some((key, value))
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case (key, Throw(e)) =>
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warn(s"Calling f for ${key} has failed", e)
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None
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}
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val keysReusedFromLastEpoch = memoizedCalls.filterKeys(newSet.contains)
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memoizedCalls = keysReusedFromLastEpoch ++ keysAndValuesAfterFilteringFailures
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debug(s"Final memoization is ${memoizedCalls.keys.mkString(", ")}")
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keys.flatMap(memoizedCalls.get)
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}
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def currentEpochKeys: Set[K] = memoizedCalls.keySet
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}
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