Since 'byte' is signed in Java, can't the first test be simply written as if (b>0) return b; Doing an 'and' of two bytes and checking if the result is 0 probably requires masking operations on >8 bit processors...
Also perhaps change to int b=readByte()) so that all operators use int's... Luc -----Original Message----- From: Yonik Seeley [mailto:[EMAIL PROTECTED] Sent: woensdag 7 december 2005 16:11 To: java-user@lucene.apache.org Subject: Re: Lucene performance bottlenecks 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 --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
