Github user srowen commented on a diff in the pull request:
https://github.com/apache/spark/pull/14762#discussion_r78981296
--- Diff:
common/unsafe/src/main/java/org/apache/spark/unsafe/array/ByteArrayMethods.java
---
@@ -47,13 +47,20 @@ public static int roundNumberOfBytesToNearestWord(int
numBytes) {
public static boolean arrayEquals(
Object leftBase, long leftOffset, Object rightBase, long
rightOffset, final long length) {
int i = 0;
- while (i <= length - 8) {
- if (Platform.getLong(leftBase, leftOffset + i) !=
- Platform.getLong(rightBase, rightOffset + i)) {
- return false;
- }
- i += 8;
- }
+
+ // This attempts to speed up the memcmp type of operation, but there
is no way
+ // to guarantee that the offsets will be on a word boundary in order
to use
+ // Platform.getLong
--- End diff --
I get it. Well at least, why not leave the current behavior for non-SPARC
architectures?
Also, I dunno, is it that rare that the offsets don't match mod 8? should
happen 1/8th of the time if the offsets are randomly distributed and I'm not
even sure that's true. Avoiding a byte by byte comparison is probably a big win
for any non-trivial region, and worth checking a simple condition.
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