It really depends on how complex the calculations for 3/4 are.

If you need/want to scale beyond one system, you should really consider 
utilizing a Message Queue system for serializing these requests to worker nodes.

In general, complex calculations should definitely be handled outside node’s 
main event loop.   If you must handle these calculations in-band (without a 
separate queue),  your best option would be a native node module that utilizes 
the thread pool within node.  Second would be to have an external process do 
your calculations, this *could* be in node.js or a compiled module in C, C++, 
GoLang etc.   I would recommend that if you aren’t going to create a native 
node module for this, that you at *least* wrap it in a module that uses a 
generic-pool in order to limit the number of processes you launch for the 
calculations.



From: Andy Zelinski 
Sent: Sunday, March 16, 2014 10:47 AM
To: [email protected] 
Subject: [nodejs] Heavy computation best practices

I am hoping for someone to point me in the right direction (examples, info) on 
how best to handle the need for some processor heavy computations that might 
best be executed with C++ math libraries. 

example scenario pseudocode:

1. application user clicks "give me 10 movies to watch" button after entering 
age, iq, time of day,  and how much time he/she has to watch. (some post data 
needed as calculation parameters)
2. application pulls some historical data from database: an array of [person 
id, age, iq, movie watched, time watched, movie length, rating user gave] -- 
say a million data points in an array
3. application then needs to apply a sophisticated math model to all data 
points and includes other hard-coded parameters. 
4. assume after watching one movie, all the hard-coded parameters change as a 
side effect, so the algorithm should rank all movies in likelihood loved from 1 
to n, choose the top ranked movie for user, and then iterate for the next 9, 
re-applying the math model

is this best handled by forking a child_process? use node-ffi? wrap a c++ 
object that can handle the math and pass the parameters?

thanks a million

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