Parallelizing Monte Carlo Tree Search

Question

I have a Monte Carlo Tree Search implementation that I need to optimize. So I thought about parallelizing the rollout phase. How to do that? (Is there a code example). Are there any python modules etc that you would recommend?

I apologize if this isn't the right place to post this.

Answer 1

you didn't give a demo code so It's hard to totally solve your problem

class MCTS:
    ....
    def _run_search(self):
        ...
        for node in nodes:
            node.reward = self._rollout(node) # rollout
        ...

And with multiprocessing, you can:

from multiprocessing import Pool
class MCTS:
    ....
    def _run_search(self):
        ...
        with Pool(os.cpu_count()-2) as p:
            result = p.map(self._rollout, nodes)
        # for node in nodes:
        #    node.reward = self._rollout(node) # rollout
        ...

So if you can give a demo code, the problem will be more clear.

And by the way, you can always replace a for loop by multiprocessing like this:

We see this situation: for loop

# inp
data = [1,2,3,4,5]
def f(x):
    return x**2

# processing (for loop)
result = []
for i in data:
    result.append(f(i))

# out
print(result) # [1,4,9,16,25]

Method 0: multiprocessing (what you want~)

# inp
data = [1,2,3,4,5]
def f(x):
    return x**2

# processing (multiprocessing)
with Pool(os.cpu_count()-2) as p:
    result = p.map(f, data)

# out
print(result) # [1,4,9,16,25]

Method 2: list comprehensions

# inp
data = [1,2,3,4,5]
def f(x):
    return x**2

# processing (list comprehension)
result = [f(i) for i in data]

# out
print(result) # [1,4,9,16,25]

Method 3: map + lambda expression

# inp
data = [1,2,3,4,5]
def f(x):
    return x**2

# processing (lambda + map)
result = map(lambda x: f(x), data)

# out
print(result) # [1,4,9,16,25]

0. for loop
1. multiprocessing
2. list comprehension
3. map + lambda expression

As you see, for loop, multiprocessing, list comprehensive, map+lambda is four way to do one thing batchly