async_plotter.py

import time
import multiprocessing as mp
import gc

#From https://gist.github.com/astrofrog/1453933

import numpy as np
import matplotlib.pyplot as plt


class Plotter():

    def __init__(self, processes=mp.cpu_count()):

        self.manager = mp.Manager()
        self.nc = self.manager.Value('i', 0)
        self.pids = []
        self.processes = processes

    def async_plotter(self, nc, fig, filename, processes):
        while nc.value >= processes:
            time.sleep(0.1)
        nc.value += 1
        print("Plotting " + filename)
        fig.savefig(filename)
        #plt.close(fig)
        nc.value -= 1
        plt.close("all")

    def save(self, fig, filename):
        p = mp.Process(target=self.async_plotter,
                       args=(self.nc, fig, filename, self.processes))
        p.start()
        self.pids.append(p)

    def join(self):
        for p in self.pids:
            p.join()
        self.pids = []
        gc.collect()

if __name__=="__main__":
    # Create instance of Asynchronous plotter
    a = Plotter()

    for i in range(10):

        print('Preparing %04i.png' % i)

        # Generate random points
        x = np.random.random(10000)
        y = np.random.random(10000)

        # Generate figure
        fig = plt.figure()
        ax = fig.add_subplot(1, 1, 1)
        ax.set_xscale('log')
        ax.set_yscale('log')
        ax.scatter(x, y)

        # Add figure to queue
        a.save(fig, '%04i.png' % i)

    # Wait for all plots to finish
    a.join()