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Posted to commits@pinot.apache.org by GitBox <gi...@apache.org> on 2021/11/05 21:08:51 UTC
[GitHub] [pinot] Jackie-Jiang commented on a change in pull request #7708: optimise getUnpaddedString with SWAR padding search
Jackie-Jiang commented on a change in pull request #7708:
URL: https://github.com/apache/pinot/pull/7708#discussion_r743973727
##########
File path: pinot-segment-local/src/main/java/org/apache/pinot/segment/local/io/util/FixedByteValueReaderWriter.java
##########
@@ -56,14 +57,28 @@ public String getUnpaddedString(int index, int numBytesPerValue, byte paddingByt
assert buffer.length >= numBytesPerValue;
long startOffset = (long) index * numBytesPerValue;
- for (int i = 0; i < numBytesPerValue; i++) {
- byte currentByte = _dataBuffer.getByte(startOffset + i);
- if (currentByte == paddingByte) {
- return new String(buffer, 0, i, UTF_8);
+ int written = 0;
+ long pattern = (paddingByte & 0xFFL) * 0x101010101010101L;
+ ByteBuffer wrapper = ByteBuffer.wrap(buffer);
+ for (int i = 0; i < ((numBytesPerValue >>> 3) << 3); i += 8) {
Review comment:
(minor) I think JVM will perform the optimization of only calculating `((numBytesPerValue >>> 3) << 3)` once, just leave a comment to confirm
##########
File path: pinot-segment-local/src/main/java/org/apache/pinot/segment/local/io/util/FixedByteValueReaderWriter.java
##########
@@ -56,14 +57,28 @@ public String getUnpaddedString(int index, int numBytesPerValue, byte paddingByt
assert buffer.length >= numBytesPerValue;
long startOffset = (long) index * numBytesPerValue;
- for (int i = 0; i < numBytesPerValue; i++) {
- byte currentByte = _dataBuffer.getByte(startOffset + i);
- if (currentByte == paddingByte) {
- return new String(buffer, 0, i, UTF_8);
+ int written = 0;
+ long pattern = (paddingByte & 0xFFL) * 0x101010101010101L;
+ ByteBuffer wrapper = ByteBuffer.wrap(buffer);
+ for (int i = 0; i < ((numBytesPerValue >>> 3) << 3); i += 8) {
+ long word = _dataBuffer.getLong(startOffset + i);
+ wrapper.putLong(i, word);
+ long zeroed = word ^ pattern;
+ long tmp = (zeroed & 0x7F7F7F7F7F7F7F7FL) + 0x7F7F7F7F7F7F7F7FL;
+ tmp = ~(tmp | zeroed | 0x7F7F7F7F7F7F7F7FL);
+ int end = Long.numberOfLeadingZeros(tmp) >>> 3;
Review comment:
Will it be faster if we first check `if (tmp != 0)`?
```suggestion
if (tmp != 0) {
int end = Long.numberOfLeadingZeros(tmp) >>> 3;
return new String(buffer, 0, written + end, UTF_8);
}
```
We can also directly make this `for` loop on `written`
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