concurrency - How to spawn concurrent computation in Haskell? -

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If I get a function that calculates four very long and returns a list with the result of four calculations, but Where each calculation is not dependent on another, how do you "parallel" in Haskell?

To better explain my question, here is a close example of my thoughts: 

 
  (defan some-function [arg1 arg2] [c1 C2 (c1 c3 c4]] [c1 c2 c3 c4])  
 
 cgi (future (very long-calculated ARGU1)) C3 (future (very-long-calculation logic 2)) 3 (Future (very long-computed hypothesis)) C4 (long-term calculations) Beggary]]; There is no need to wrap the C4 in the future [@ C1 @ C2 @ C3C4])

What will happen in Haskell as follows? 

  someFunction :: (a -> A -> A -> a) - & gt; (A) C1 and Lt; - Rapper (very long computed computation) C2 and Lt; - Rapper (very long-calculated logic 2) C3 and LT; - Rapper (very long-calculated computation) C4 and LT; - (very-long-calculated arg4) rseq c1 rseq c2 rseq c3 returns (c1, c2, c3, c4)

Do I need rpar / rseq c4?

What is the rpar / Rseq way to go for such concurrent calculation?

What if I do not do rseq, then what program will wait, later, when I try to use return values ​​in the returned list?

Is it transparent or do you need to do something like "DRF" that you are in closure when you use '@'?

You are looking for a package. For example, if you want to run three computations and want to take one that completes this first:

Function = do c1 < - async $ veryLongComputation1 c2 & lt; - Async $ veryLongComputation2 c3 & lt; - async $ very long computations 3 (_, a) & lt; - Wait for any $ [c1, c2, c3] one

come back or you can wait for special async thread Share the situation via, and stm . This is a very useful package for this type of thing. The exact version you asked in OP will look something like this: 

  Some functions: IO (a, b, c, d) someFunction = Do c1 & lt; - async $ veryLongComputation1C2 & lt; - async $ veryLongComputation2 c3 & lt; - async $ long long computation 3 v4 & lt; - Very long Compliment 4 - Wait for all the results and wait for a Tupple $ (,,,) & lt; $ & Gt; C1 and LT; * & Gt; C2 and lieutenant; * & Gt; C3 & Lt; * & Gt; (Return v4)

It surely assumes that c1, c2, c3 are all side-effects and you are not interested in the result. Wait and elections get value for you.

I also highly recommend "Haskell in parallel and concurrent programming" by Simon Marlowe.


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