I checked out readVInt() to see if I could optimize it any...
For a random distribution of integers <200 I was able to speed it up a
little bit, but nothing to write home about:
old new percent
Java14-client : 13547 12468 8%
Java14-server: 6047 5266 14%
Java15-client: 11688 11234 4%
Java15-server: 5813 4875 19%
Java16-client: 11125 10719 4%
Java16-server: 6031 4859 24%
Then I tested it with integers <128, and it was slower (up to 25%) for
Java15-server, Java16-server, Java16-client. Since <128 could be an
important case, I stopped there.
On a P4 2.8GHz, I was getting around 180M readVInt() calls per second
for single byte VInts (including loop and method call overhead).
Here is the fastest version I could come up with on a P4. It's faster
with variable length vInts, slower will single bytes.
public int readVInt() throws IOException {
byte b = readByte();
if ((b&0x80)==0) return b;
b &= 0x7f;
byte b2 = readByte();
if ((b&0x80)==0) return (b2<<7) | b;
b2 &= 0x7f;
byte b3 = readByte();
if ((b&0x80)==0) return (b3<<14) | (b2<<7) | b;
b3 &= 0x7f;
byte b4 = readByte();
if ((b&0x80)==0) return (b4<<21) | (b3<<14) | (b2<<7) | b;
b4 &= 0x7f;
byte b5 = readByte();
return (b5<<28) | (b4<<21) | (b3<<14) | (b2<<7) | b;
}
-Yonik
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