Status: New
Owner: ----
New issue 3913 by kiswono: Poor performance for for-in with lots of keys
https://code.google.com/p/v8/issues/detail?id=3913
Version: all
OS: Linux
Architecture: x64
What steps will reproduce the problem?
1. Use this code:
var MAX_DATA = 120000;
var i2ch =
['0','1','2','3','4','5','6','7','8','9','a','B','c','D','e','F'];
function get_first_digit(d) {
while(d > 10) d /= 10;
return d|0;
}
function to_rhex(v) {
var hex = '';
v = v|0;
while(v>0) {
hex += i2ch[v%16];
v = (v/16)|0;
}
return hex;
}
function add_or_inc(m,key,set,inc) {
if(m[key] === undefined) {
m[key] = set;
return false;
}
m[key] += inc;
return true;
}
(function() {
var m = {};
var dup1 = 0, dup2 = 0, dup3 = 0;
for(var z=MAX_DATA;z>0;--z) {
var val2 = MAX_DATA-z;
var val3 = MAX_DATA*2-z;
var key1 = "" + z;
var key2 = "" + val2;
var key3 = to_rhex(val3);
if(add_or_inc(m,key1,z,val2)) ++dup1;
if(add_or_inc(m,key2,val2,val3)) ++dup2;
if(add_or_inc(m,key3,val3,z)) ++dup3;
}
console.log(dup1,dup2,dup3);
var total = 0, verify = 0, count = 0;
for (var key in m) {
total += get_first_digit(m[key]);
verify += key.length;
count += 1;
}
console.log(total,verify,count);
})()
2. run it using v8 (or chrome, or nodejs, or iojs)
3. compare with mozjs, javascriptcore, or rhino
What is the expected output?
less than a second
What do you see instead?
more than 16 seconds
for comparison: mozjs and jsc completed in less than a second, rhino less
than 2 seconds.
Please use labels and text to provide additional information.
See
http://kokizzu.blogspot.com/2015/02/small-string-associative-benchmark.html
for more information
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