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LUCENE-10130: small optimizations to SparseFixedBitSet set() codepath

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Don't spend so many cycles updating ramBytesUsed when setting each bit.
Avoid recomputing some shifts that the caller already computes.
This commit is contained in:
Robert Muir 2021-10-02 08:30:54 -04:00
parent d395435fa8
commit 3dee08a09a
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1 changed files with 12 additions and 11 deletions
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23
lucene/core/src/java/org/apache/lucene/util/SparseFixedBitSet.java
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@ -149,13 +149,13 @@ public class SparseFixedBitSet extends BitSet {
} else if (index == 0) {
// if the index is 0, it means that we just found a block of 4096 bits
// that has no bit that is set yet. So let's initialize a new block:
insertBlock(i4096, i64, i);
insertBlock(i4096, i64bit, i);
return false;
} else {
// in that case we found a block of 4096 bits that has some values, but
// the sub-block of 64 bits that we are interested in has no value yet,
// so we need to insert a new long
insertLong(i4096, i64, i, index);
insertLong(i4096, i64bit, i, index);
return false;
}
}
@ -184,32 +184,32 @@ public class SparseFixedBitSet extends BitSet {
} else if (index == 0) {
// if the index is 0, it means that we just found a block of 4096 bits
// that has no bit that is set yet. So let's initialize a new block:
insertBlock(i4096, i64, i);
insertBlock(i4096, i64bit, i);
} else {
// in that case we found a block of 4096 bits that has some values, but
// the sub-block of 64 bits that we are interested in has no value yet,
// so we need to insert a new long
insertLong(i4096, i64, i, index);
insertLong(i4096, i64bit, i, index);
}
}
private void insertBlock(int i4096, int i64, int i) {
indices[i4096] = 1L << i64; // shifts are mod 64 in java
private void insertBlock(int i4096, long i64bit, int i) {
indices[i4096] = i64bit;
assert bits[i4096] == null;
bits[i4096] = new long[] {1L << i}; // shifts are mod 64 in java
++nonZeroLongCount;
ramBytesUsed += SINGLE_ELEMENT_ARRAY_BYTES_USED;
}
private void insertLong(int i4096, int i64, int i, long index) {
indices[i4096] |= 1L << i64; // shifts are mod 64 in java
private void insertLong(int i4096, long i64bit, int i, long index) {
indices[i4096] |= i64bit;
// we count the number of bits that are set on the right of i64
// this gives us the index at which to perform the insertion
final int o = Long.bitCount(index & ((1L << i64) - 1));
final int o = Long.bitCount(index & (i64bit - 1));
final long[] bitArray = bits[i4096];
if (bitArray[bitArray.length - 1] == 0) {
// since we only store non-zero longs, if the last value is 0, it means
// that we alreay have extra space, make use of it
// that we already have extra space, make use of it
System.arraycopy(bitArray, o, bitArray, o + 1, bitArray.length - o - 1);
bitArray[o] = 1L << i;
} else {
@ -220,7 +220,8 @@ public class SparseFixedBitSet extends BitSet {
newBitArray[o] = 1L << i;
System.arraycopy(bitArray, o, newBitArray, o + 1, bitArray.length - o);
bits[i4096] = newBitArray;
ramBytesUsed += RamUsageEstimator.sizeOf(newBitArray) - RamUsageEstimator.sizeOf(bitArray);
// we may slightly overestimate size here, but keep it cheap
ramBytesUsed += (newBitArray.length - bitArray.length) << 3;
}
++nonZeroLongCount;
}