diff options
author | Matei Zaharia <matei@eecs.berkeley.edu> | 2013-11-25 20:48:37 -0800 |
---|---|---|
committer | Matei Zaharia <matei@eecs.berkeley.edu> | 2013-11-25 20:48:37 -0800 |
commit | 0e2109ddb2f27d8a6a9f125206674273b03d1f5e (patch) | |
tree | b6336a2c902c3f5586cebc4e65d59b58b7d17c50 /core | |
parent | c46067f096f03b6d07ea1ba65c185b851f8a8d8e (diff) | |
parent | 466fd06475d8ed262c456421ed2dceba54229db1 (diff) | |
download | spark-0e2109ddb2f27d8a6a9f125206674273b03d1f5e.tar.gz spark-0e2109ddb2f27d8a6a9f125206674273b03d1f5e.tar.bz2 spark-0e2109ddb2f27d8a6a9f125206674273b03d1f5e.zip |
Merge pull request #204 from rxin/hash
OpenHashSet fixes
Incorporated ideas from pull request #200.
- Use Murmur Hash 3 finalization step to scramble the bits of HashCode
instead of the simpler version in java.util.HashMap; the latter one
had trouble with ranges of consecutive integers. Murmur Hash 3 is used
by fastutil.
- Don't check keys for equality when re-inserting due to growing the
table; the keys will already be unique.
- Remember the grow threshold instead of recomputing it on each insert
Also added unit tests for size estimation for specialized hash sets and maps.
Diffstat (limited to 'core')
-rw-r--r-- | core/src/main/scala/org/apache/spark/util/collection/OpenHashSet.scala | 107 | ||||
-rw-r--r-- | core/src/test/scala/org/apache/spark/util/collection/OpenHashMapSuite.scala | 16 | ||||
-rw-r--r-- | core/src/test/scala/org/apache/spark/util/collection/OpenHashSetSuite.scala | 20 | ||||
-rw-r--r-- | core/src/test/scala/org/apache/spark/util/collection/PrimitiveKeyOpenHashMapSuite.scala (renamed from core/src/test/scala/org/apache/spark/util/collection/PrimitiveKeyOpenHashSetSuite.scala) | 14 |
4 files changed, 103 insertions, 54 deletions
diff --git a/core/src/main/scala/org/apache/spark/util/collection/OpenHashSet.scala b/core/src/main/scala/org/apache/spark/util/collection/OpenHashSet.scala index 4592e4f939..40986e3731 100644 --- a/core/src/main/scala/org/apache/spark/util/collection/OpenHashSet.scala +++ b/core/src/main/scala/org/apache/spark/util/collection/OpenHashSet.scala @@ -79,6 +79,7 @@ class OpenHashSet[@specialized(Long, Int) T: ClassManifest]( protected var _capacity = nextPowerOf2(initialCapacity) protected var _mask = _capacity - 1 protected var _size = 0 + protected var _growThreshold = (loadFactor * _capacity).toInt protected var _bitset = new BitSet(_capacity) @@ -115,7 +116,29 @@ class OpenHashSet[@specialized(Long, Int) T: ClassManifest]( * @return The position where the key is placed, plus the highest order bit is set if the key * exists previously. */ - def addWithoutResize(k: T): Int = putInto(_bitset, _data, k) + def addWithoutResize(k: T): Int = { + var pos = hashcode(hasher.hash(k)) & _mask + var i = 1 + while (true) { + if (!_bitset.get(pos)) { + // This is a new key. + _data(pos) = k + _bitset.set(pos) + _size += 1 + return pos | NONEXISTENCE_MASK + } else if (_data(pos) == k) { + // Found an existing key. + return pos + } else { + val delta = i + pos = (pos + delta) & _mask + i += 1 + } + } + // Never reached here + assert(INVALID_POS != INVALID_POS) + INVALID_POS + } /** * Rehash the set if it is overloaded. @@ -126,7 +149,7 @@ class OpenHashSet[@specialized(Long, Int) T: ClassManifest]( * to a new position (in the new data array). */ def rehashIfNeeded(k: T, allocateFunc: (Int) => Unit, moveFunc: (Int, Int) => Unit) { - if (_size > loadFactor * _capacity) { + if (_size > _growThreshold) { rehash(k, allocateFunc, moveFunc) } } @@ -161,37 +184,6 @@ class OpenHashSet[@specialized(Long, Int) T: ClassManifest]( def nextPos(fromPos: Int): Int = _bitset.nextSetBit(fromPos) /** - * Put an entry into the set. Return the position where the key is placed. In addition, the - * highest bit in the returned position is set if the key exists prior to this put. - * - * This function assumes the data array has at least one empty slot. - */ - private def putInto(bitset: BitSet, data: Array[T], k: T): Int = { - val mask = data.length - 1 - var pos = hashcode(hasher.hash(k)) & mask - var i = 1 - while (true) { - if (!bitset.get(pos)) { - // This is a new key. - data(pos) = k - bitset.set(pos) - _size += 1 - return pos | NONEXISTENCE_MASK - } else if (data(pos) == k) { - // Found an existing key. - return pos - } else { - val delta = i - pos = (pos + delta) & mask - i += 1 - } - } - // Never reached here - assert(INVALID_POS != INVALID_POS) - INVALID_POS - } - - /** * Double the table's size and re-hash everything. We are not really using k, but it is declared * so Scala compiler can specialize this method (which leads to calling the specialized version * of putInto). @@ -204,34 +196,49 @@ class OpenHashSet[@specialized(Long, Int) T: ClassManifest]( */ private def rehash(k: T, allocateFunc: (Int) => Unit, moveFunc: (Int, Int) => Unit) { val newCapacity = _capacity * 2 - require(newCapacity <= (1 << 29), "Can't make capacity bigger than 2^29 elements") - allocateFunc(newCapacity) - val newData = new Array[T](newCapacity) val newBitset = new BitSet(newCapacity) - var pos = 0 - _size = 0 - while (pos < _capacity) { - if (_bitset.get(pos)) { - val newPos = putInto(newBitset, newData, _data(pos)) - moveFunc(pos, newPos & POSITION_MASK) + val newData = new Array[T](newCapacity) + val newMask = newCapacity - 1 + + var oldPos = 0 + while (oldPos < capacity) { + if (_bitset.get(oldPos)) { + val key = _data(oldPos) + var newPos = hashcode(hasher.hash(key)) & newMask + var i = 1 + var keepGoing = true + // No need to check for equality here when we insert so this has one less if branch than + // the similar code path in addWithoutResize. + while (keepGoing) { + if (!newBitset.get(newPos)) { + // Inserting the key at newPos + newData(newPos) = key + newBitset.set(newPos) + moveFunc(oldPos, newPos) + keepGoing = false + } else { + val delta = i + newPos = (newPos + delta) & newMask + i += 1 + } + } } - pos += 1 + oldPos += 1 } + _bitset = newBitset _data = newData _capacity = newCapacity - _mask = newCapacity - 1 + _mask = newMask + _growThreshold = (loadFactor * newCapacity).toInt } /** - * Re-hash a value to deal better with hash functions that don't differ - * in the lower bits, similar to java.util.HashMap + * Re-hash a value to deal better with hash functions that don't differ in the lower bits. + * We use the Murmur Hash 3 finalization step that's also used in fastutil. */ - private def hashcode(h: Int): Int = { - val r = h ^ (h >>> 20) ^ (h >>> 12) - r ^ (r >>> 7) ^ (r >>> 4) - } + private def hashcode(h: Int): Int = it.unimi.dsi.fastutil.HashCommon.murmurHash3(h) private def nextPowerOf2(n: Int): Int = { val highBit = Integer.highestOneBit(n) diff --git a/core/src/test/scala/org/apache/spark/util/collection/OpenHashMapSuite.scala b/core/src/test/scala/org/apache/spark/util/collection/OpenHashMapSuite.scala index ca3f684668..63e874fed3 100644 --- a/core/src/test/scala/org/apache/spark/util/collection/OpenHashMapSuite.scala +++ b/core/src/test/scala/org/apache/spark/util/collection/OpenHashMapSuite.scala @@ -2,8 +2,20 @@ package org.apache.spark.util.collection import scala.collection.mutable.HashSet import org.scalatest.FunSuite - -class OpenHashMapSuite extends FunSuite { +import org.scalatest.matchers.ShouldMatchers +import org.apache.spark.util.SizeEstimator + +class OpenHashMapSuite extends FunSuite with ShouldMatchers { + + test("size for specialized, primitive value (int)") { + val capacity = 1024 + val map = new OpenHashMap[String, Int](capacity) + val actualSize = SizeEstimator.estimate(map) + // 64 bit for pointers, 32 bit for ints, and 1 bit for the bitset. + val expectedSize = capacity * (64 + 32 + 1) / 8 + // Make sure we are not allocating a significant amount of memory beyond our expected. + actualSize should be <= (expectedSize * 1.1).toLong + } test("initialization") { val goodMap1 = new OpenHashMap[String, Int](1) diff --git a/core/src/test/scala/org/apache/spark/util/collection/OpenHashSetSuite.scala b/core/src/test/scala/org/apache/spark/util/collection/OpenHashSetSuite.scala index 4e11e8a628..4768a1e60b 100644 --- a/core/src/test/scala/org/apache/spark/util/collection/OpenHashSetSuite.scala +++ b/core/src/test/scala/org/apache/spark/util/collection/OpenHashSetSuite.scala @@ -1,9 +1,27 @@ package org.apache.spark.util.collection import org.scalatest.FunSuite +import org.scalatest.matchers.ShouldMatchers +import org.apache.spark.util.SizeEstimator -class OpenHashSetSuite extends FunSuite { + +class OpenHashSetSuite extends FunSuite with ShouldMatchers { + + test("size for specialized, primitive int") { + val loadFactor = 0.7 + val set = new OpenHashSet[Int](64, loadFactor) + for (i <- 0 until 1024) { + set.add(i) + } + assert(set.size === 1024) + assert(set.capacity > 1024) + val actualSize = SizeEstimator.estimate(set) + // 32 bits for the ints + 1 bit for the bitset + val expectedSize = set.capacity * (32 + 1) / 8 + // Make sure we are not allocating a significant amount of memory beyond our expected. + actualSize should be <= (expectedSize * 1.1).toLong + } test("primitive int") { val set = new OpenHashSet[Int] diff --git a/core/src/test/scala/org/apache/spark/util/collection/PrimitiveKeyOpenHashSetSuite.scala b/core/src/test/scala/org/apache/spark/util/collection/PrimitiveKeyOpenHashMapSuite.scala index dfd6aed2c4..2220b4f0d5 100644 --- a/core/src/test/scala/org/apache/spark/util/collection/PrimitiveKeyOpenHashSetSuite.scala +++ b/core/src/test/scala/org/apache/spark/util/collection/PrimitiveKeyOpenHashMapSuite.scala @@ -2,8 +2,20 @@ package org.apache.spark.util.collection import scala.collection.mutable.HashSet import org.scalatest.FunSuite +import org.scalatest.matchers.ShouldMatchers +import org.apache.spark.util.SizeEstimator -class PrimitiveKeyOpenHashSetSuite extends FunSuite { +class PrimitiveKeyOpenHashMapSuite extends FunSuite with ShouldMatchers { + + test("size for specialized, primitive key, value (int, int)") { + val capacity = 1024 + val map = new PrimitiveKeyOpenHashMap[Int, Int](capacity) + val actualSize = SizeEstimator.estimate(map) + // 32 bit for keys, 32 bit for values, and 1 bit for the bitset. + val expectedSize = capacity * (32 + 32 + 1) / 8 + // Make sure we are not allocating a significant amount of memory beyond our expected. + actualSize should be <= (expectedSize * 1.1).toLong + } test("initialization") { val goodMap1 = new PrimitiveKeyOpenHashMap[Int, Int](1) |