rymurr commented on a change in pull request #7101:
URL: https://github.com/apache/arrow/pull/7101#discussion_r422074255
##########
File path:
java/memory/src/main/java/org/apache/arrow/memory/util/hash/SimpleHasher.java
##########
@@ -58,21 +56,21 @@ public int hashCode(long address, long length) {
int hashValue = 0;
int index = 0;
while (index + 8 <= length) {
- long longValue = getLong(address + index);
+ long longValue = MemoryUtil.UNSAFE.getLong(address + index);
int longHash = getLongHashCode(longValue);
hashValue = combineHashCode(hashValue, longHash);
index += 8;
}
if (index + 4 <= length) {
- int intValue = getInt(address + index);
+ int intValue = MemoryUtil.UNSAFE.getInt(address + index);
int intHash = intValue;
hashValue = combineHashCode(hashValue, intHash);
index += 4;
}
while (index < length) {
- byte byteValue = getByte(address + index);
+ byte byteValue = MemoryUtil.UNSAFE.getByte(address + index);
Review comment:
A cursory look at the bytecode shows the `PlatformDependent` call
results in a few static method invocations:
`PlatformDependent.getByte` is defined as
``` java
public static byte getByte(long address) {
return PlatformDependent0.getByte(address);
}
```
and `PlatformDependent0` is
``` java
public static byte getByte(long address) {
return UNSAFE.getByte(address);
}
```
And the `MemoryUtil` one the same with 1 less layer of indirect static
calls. I would anticipate the JIT would optimise the paths to be the same.
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