rmuir commented on a change in pull request #69:
URL: https://github.com/apache/lucene/pull/69#discussion_r609724812
##########
File path: lucene/core/src/java/org/apache/lucene/codecs/lucene90/PForUtil.java
##########
@@ -121,4 +167,146 @@ void skip(DataInput in) throws IOException {
in.skipBytes(forUtil.numBytes(bitsPerValue) + (numExceptions << 1));
}
}
+
+ /**
+ * Fill {@code longs} with the final values for the case of all deltas being
1. Note this assumes
+ * there are no exceptions to apply.
+ */
+ private static void prefixSumOfOnes(long[] longs, long base) {
+ System.arraycopy(IDENTITY_PLUS_ONE, 0, longs, 0, ForUtil.BLOCK_SIZE);
+ // This loop gets auto-vectorized
+ for (int i = 0; i < ForUtil.BLOCK_SIZE; ++i) {
+ longs[i] += base;
+ }
+ }
+
+ /**
+ * Fill {@code longs} with the final values for the case of all deltas being
{@code val}. Note
+ * this assumes there are no exceptions to apply.
+ */
+ private static void prefixSumOf(long[] longs, long base, long val) {
+ for (int i = 0; i < ForUtil.BLOCK_SIZE; i++) {
+ longs[i] = (i + 1) * val + base;
Review comment:
i dont know enough about the autovectorization to trick it. But in
general i wonder if we should replace some instances of `ForUtil.BLOCK_SIZE`
with `array.length` etc where possible to make the compiler's job easier wrt
bounds checks and loop processing. arrays are being passed in as parameters,
these are private static methods, so i don't know how smart it is about this
today :) On the other hand, maybe it is a waste of your time and just costs a
single inexpensive check up front...
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