public BytesBytesMultiHashMap(int initialCapacity, float loadFactor, int wbSize, long memUsage) {
if (loadFactor < 0 || loadFactor > 1) {
throw new AssertionError("Load factor must be between (0, 1].");
}
assert initialCapacity > 0;
initialCapacity =
(Long.bitCount(initialCapacity) == 1)
? initialCapacity
: nextHighestPowerOfTwo(initialCapacity);
// 8 bytes per long in the refs, assume data will be empty. This is just a sanity check.
int maxCapacity =
(memUsage <= 0)
? DEFAULT_MAX_CAPACITY
: (int) Math.min((long) DEFAULT_MAX_CAPACITY, memUsage / 8);
if (maxCapacity < initialCapacity || initialCapacity <= 0) {
// Either initialCapacity is too large, or nextHighestPowerOfTwo overflows
initialCapacity =
(Long.bitCount(maxCapacity) == 1) ? maxCapacity : nextLowestPowerOfTwo(maxCapacity);
}
validateCapacity(initialCapacity);
startingHashBitCount = 63 - Long.numberOfLeadingZeros(initialCapacity);
this.loadFactor = loadFactor;
refs = new long[initialCapacity];
writeBuffers = new WriteBuffers(wbSize, MAX_WB_SIZE);
resizeThreshold = (int) (initialCapacity * this.loadFactor);
}
private void expandAndRehashImpl(long capacity) {
long expandTime = System.currentTimeMillis();
final long[] oldRefs = refs;
validateCapacity(capacity);
long[] newRefs = new long[(int) capacity];
// We store some hash bits in ref; for every expansion, we need to add one bit to hash.
// If we have enough bits, we'll do that; if we don't, we'll rehash.
// LOG.info("Expanding the hashtable to " + capacity + " capacity");
int newHashBitCount = hashBitCount + 1;
// Relocate all assigned slots from the old hash table.
int maxSteps = 0;
for (int oldSlot = 0; oldSlot < oldRefs.length; ++oldSlot) {
long oldRef = oldRefs[oldSlot];
if (oldRef == 0) {
continue;
}
// TODO: we could actually store a bit flag in ref indicating whether this is a hash
// match or a probe, and in the former case use hash bits (for a first few resizes).
// int hashCodeOrPart = oldSlot | Ref.getNthHashBit(oldRef, startingHashBitCount,
// newHashBitCount);
writeBuffers.setReadPoint(getFirstRecordLengthsOffset(oldRef, null));
// Read the value and key length for the first record.
int hashCode =
(int)
writeBuffers.readNByteLong(
Ref.getOffset(oldRef) - writeBuffers.readVLong() - writeBuffers.readVLong() - 4,
4);
int probeSteps = relocateKeyRef(newRefs, oldRef, hashCode);
maxSteps = Math.max(probeSteps, maxSteps);
}
this.refs = newRefs;
this.largestNumberOfSteps = maxSteps;
this.hashBitCount = newHashBitCount;
this.resizeThreshold = (int) (capacity * loadFactor);
metricExpandsMs += (System.currentTimeMillis() - expandTime);
++metricExpands;
}
