rmuir commented on PR #14031:
URL: https://github.com/apache/lucene/pull/14031#issuecomment-2512993292
We can iterate on last patch and save a few more bytes (302b) if we just
pull out into a static final constant instead, too:
```
---
a/lucene/core/src/java21/org/apache/lucene/internal/vectorization/PanamaVectorUtilSupport.java
+++
b/lucene/core/src/java21/org/apache/lucene/internal/vectorization/PanamaVectorUtilSupport.java
@@ -75,6 +75,9 @@ final class PanamaVectorUtilSupport implements
VectorUtilSupport {
}
}
+ // cached vector sizes for smaller method bodies
+ private static final int FLOAT_SPECIES_LENGTH = FLOAT_SPECIES.length();
+
// the way FMA should work! if available use it, otherwise fall back to
mul/add
private static FloatVector fma(FloatVector a, FloatVector b, FloatVector
c) {
if (Constants.HAS_FAST_VECTOR_FMA) {
@@ -99,7 +102,7 @@ final class PanamaVectorUtilSupport implements
VectorUtilSupport {
float res = 0;
// if the array size is large (> 2x platform vector size), its worth
the overhead to vectorize
- if (a.length > 2 * FLOAT_SPECIES.length()) {
+ if (a.length > 2 * FLOAT_SPECIES_LENGTH) {
i += FLOAT_SPECIES.loopBound(a.length);
res += dotProductBody(a, b, i);
}
@@ -120,31 +123,33 @@ final class PanamaVectorUtilSupport implements
VectorUtilSupport {
FloatVector acc2 = FloatVector.zero(FLOAT_SPECIES);
FloatVector acc3 = FloatVector.zero(FLOAT_SPECIES);
FloatVector acc4 = FloatVector.zero(FLOAT_SPECIES);
- final int floatSpeciesLength = FLOAT_SPECIES.length();
- final int unrolledLimit = limit - 3 * floatSpeciesLength;
- for (; i < unrolledLimit; i += 4 * floatSpeciesLength) {
+ final int unrolledLimit = limit - 3 * FLOAT_SPECIES_LENGTH;
+ for (; i < unrolledLimit; i += 4 * FLOAT_SPECIES_LENGTH) {
// one
FloatVector va = FloatVector.fromArray(FLOAT_SPECIES, a, i);
FloatVector vb = FloatVector.fromArray(FLOAT_SPECIES, b, i);
acc1 = fma(va, vb, acc1);
// two
- FloatVector vc = FloatVector.fromArray(FLOAT_SPECIES, a, i +
floatSpeciesLength);
- FloatVector vd = FloatVector.fromArray(FLOAT_SPECIES, b, i +
floatSpeciesLength);
+ final int i2 = i + FLOAT_SPECIES_LENGTH;
+ FloatVector vc = FloatVector.fromArray(FLOAT_SPECIES, a, i2);
+ FloatVector vd = FloatVector.fromArray(FLOAT_SPECIES, b, i2);
acc2 = fma(vc, vd, acc2);
// three
- FloatVector ve = FloatVector.fromArray(FLOAT_SPECIES, a, i + 2 *
floatSpeciesLength);
- FloatVector vf = FloatVector.fromArray(FLOAT_SPECIES, b, i + 2 *
floatSpeciesLength);
+ final int i3 = i2 + FLOAT_SPECIES_LENGTH;
+ FloatVector ve = FloatVector.fromArray(FLOAT_SPECIES, a, i3);
+ FloatVector vf = FloatVector.fromArray(FLOAT_SPECIES, b, i3);
acc3 = fma(ve, vf, acc3);
// four
- FloatVector vg = FloatVector.fromArray(FLOAT_SPECIES, a, i + 3 *
floatSpeciesLength);
- FloatVector vh = FloatVector.fromArray(FLOAT_SPECIES, b, i + 3 *
floatSpeciesLength);
+ final int i4 = i3 + FLOAT_SPECIES_LENGTH;
+ FloatVector vg = FloatVector.fromArray(FLOAT_SPECIES, a, i4);
+ FloatVector vh = FloatVector.fromArray(FLOAT_SPECIES, b, i4);
acc4 = fma(vg, vh, acc4);
}
// vector tail: less scalar computations for unaligned sizes, esp with
big vector sizes
- for (; i < limit; i += floatSpeciesLength) {
+ for (; i < limit; i += FLOAT_SPECIES_LENGTH) {
FloatVector va = FloatVector.fromArray(FLOAT_SPECIES, a, i);
FloatVector vb = FloatVector.fromArray(FLOAT_SPECIES, b, i);
acc1 = fma(va, vb, acc1);
```
I feel like it makes the code a bit easier on the eyes, and benchie is happy:
```
Benchmark (size) Mode Cnt Score
Error Units
VectorUtilBenchmark.floatDotProductVector (main) 1024 thrpt 75 12.347
± 0.148 ops/us
VectorUtilBenchmark.floatDotProductVector (patch) 1024 thrpt 75 12.754
± 0.106 ops/us
```
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