8 logical cpu's should give *8 run time benefit? - node.js

Question

the code i am running when using promise.all should run at about \8 the time when i am using regular "blocking" for, but the result is very similar not even half the time.
i have tried to run this 2 NODEJS programs in the same computer.
WHEN USING PROMISE.ALL
let user = { "name": "shay", "interests": ["category1", "category2", "category3", "category4", "category5", "category6", "category7", "category8", "category9", "category10"] }
let result = [];
let Companies = [];
for (i = 0; i < 3000000; i++) {
let company = { "name": "company" + i, "interest": "category" + (Math.floor(Math.random() * 10) + 1) };
Companies.push(company);
}
const successRate = () => {
return (Math.floor(Math.random() * 100) + 1) + "%"
}
const task = function (interest) {
return new Promise((resolve, reject) => {
Companies.forEach(company => {
if (company.interest == interest)
result.push({ "company": company.name, "interest": company.interest, "success": successRate() })
});
resolve('succeed!');
});
};
const run = async function () {
let tasks = user.interests.map(interest => {
return task(interest)
});
await Promise.all(tasks);
}
const start = Date.now();
run();
WHEN USING REGULAR FOR
let user = {"name":"shay","interests":["category1","category2","category3","category4","category5","category6","category7","category8","category9","category10"]}
let result =[];
let Companies = [];
for (i=0;i<3000000;i++)
{
let company = {"name":"company"+i,"interest":"category"+(Math.floor(Math.random() * 10) + 1)};
Companies.push(company);
}
const successRate=()=>{
return (Math.floor(Math.random() * 100) + 1)+"%"
}
const start = Date.now();
user.interests.forEach(interest => {
Companies.forEach(company => {
if (company.interest==interest)
result.push({"company":company.name,"interest":company.interest,"success":successRate()})
});
});
console.log("run time",Date.now()-start);
the promise.all total run time is 1314
the regular for total run time is 1430

Answer 1

Node.js follows a single threaded architecture, it doesn't create a new thread for a new promise - everything runs in the same thread. Asynchronous behaviour is achieved via event loop, underlying OS concurrency and libuv. If you're familiar with Nginx - it actually works pretty much the same way. So don't mix JavaScript's Promise<> with Java's Future<>.