Promiseの（bluebridの）配列系ループの時間計測メモ #JavaScript

概要

Promiseの（bluebridの）配列系ループの時間計測メモ

promise_looptest.js

const Promise = require('bluebird');

const array = [];
for(let i = 0; i < 10000000; ++i){
    array.push(i);
}

console.time('map');
let count = 0;
return Promise.map(array, (a) => {
    ++count;
    return a;
})
.then(() => {
    console.timeEnd('map');
    console.log(count);
    count = 0;
    console.time('each');
    return Promise.each(array, (a) => {
        ++count;
        return a;
    });
})
.then(() => {
    console.timeEnd('each');
    console.log(count);
    count = 0;
    console.time('reduce');
    return Promise.reduce(array, (promise, a) => {
        ++count;
        return a;
    }, 0);
})
.then(() => {
    console.timeEnd('reduce');
    console.log(count);
    count = 0;
    console.time('all');
    return Promise.all(array.map((a) => {
        ++count;
        return a;
    }))
})
.then(() => {
    console.timeEnd('all');
    console.log(count);
})

結果

map: 1300.333ms
10000000
each: 1641.458ms
10000000
reduce: 1466.863ms
10000000
all: 5150.526ms
10000000

mapが微妙に早い。
誤差のようなきもするけど、何回かしてみてもmapが
一番早い。

別の角度から

promise_looptest2.js

const Promise = require('bluebird');

const array = [];
for(let i = 0; i < 10000000; ++i){
    array.push(i);
}

console.time('map');
let count = 0;
return Promise.map(array, (a) => {
    return Promise.resolve()
    .then(() => {
        ++count;
        return a;
    });
})
.then(() => {
    console.timeEnd('map');
    console.log(count);
    count = 0;
    console.time('each');
    return Promise.each(array, (a) => {
        return Promise.resolve()
        .then(() => {
            ++count;
            return a;
        });
    });
})
.then(() => {
    console.timeEnd('each');
    console.log(count);
    count = 0;
    console.time('reduce');
    return Promise.reduce(array, (promise, a) => {
        return Promise.resolve()
        .then(() => {
            ++count;
            return a;
        });
    }, 0);
})
.then(() => {
    console.timeEnd('reduce');
    console.log(count);
    count = 0;
    console.time('all');
    return Promise.all(array.map((a) => {
        return Promise.resolve()
        .then(() => {
            ++count;
            return a;
        });
    }))
})
.then(() => {
    console.timeEnd('all');
    console.log(count);
})

とPromiseを返すようにしてみる。

結果

mapでout of memory

<--- Last few GCs --->

   14801 ms: Mark-sweep 1401.0 (1440.9) -> 1401.0 (1440.9) MB, 1042.0 / 0.0 ms (+ 0.7 ms in 2 steps since start of marking, biggest step 0.6 ms) [allocation failure] [scavenge might not succeed].
   16553 ms: Mark-sweep 1401.0 (1440.9) -> 1401.0 (1440.9) MB, 1751.2 / 0.0 ms [allocation failure] [scavenge might not succeed].


<--- JS stacktrace --->
Cannot get stack trace in GC.
FATAL ERROR: MarkCompactCollector: semi-space copy, fallback in old gen Allocation failed - JavaScript heap out of memory

現時点での結果

何がダメでout of memoryかの原因は調査予定。
挙動を見ていた感じだと
全部のPromiseを展開するまでmapはまっているように見えた。
なぜ待つのかを調査してみたい。