An simple example using parallelization function

[caoxiaoyue]

Dear developers,

I notice nestle can support parallelization sampling now. can you give a simple example to show how to use it? I have made some attempt but failed. Below is my attempt.

from pathos.multiprocessing import ProcessingPool 
pool = ProcessingPool(nodes=4)  #use dill pickle

#below class is from nestle source code
class FakePool(object):
    """A fake Pool for serial function evaluations."""

    def __init__(self,pool):
        self.pool = pool

    def submit(self, fn, *args, **kwargs):
        return FakeFuture(fn, *args, **kwargs)

    def map(self, func, *iterables):
        return self.pool.map(func, *iterables)

    def shutdown(self):
        pass
    
class FakeFuture(object):
    """A fake Future to mimic function calls."""

    def __init__(self, fn, *args, **kwargs):
        self.fn = fn
        self.args = args
        self.kwargs = kwargs

    def result(self):
        return self.fn(*self.args, **self.kwargs)

    def cancel(self):
        return True

fakepool = FakePool(pool)


t1 = time.time()
res = nestle.sample(loglike, prior, 7, method='multi',pool=fakepool, queue_size=4,
                    npoints=25,callback=nestle.print_progress)
t2 = time.time()

Above method can run successfully, but the runing time of code do not decrease. Also, I type top command in linux shell, it seems above method do not spawn subprocess. could you give any suggestion?