large memory leak in new contour routine

[efiring]

In master and in 1.5.1, the new C++ contour routine has a massive memory leak; the 'legacy' mode does not. The following script illustrates this; run it as-is and then with the 'legacy' kwarg uncommented for comparison. (The script is long only because it seems report_memory has been removed from cbook. Unless it has simply been moved elsewhere or renamed, we need to bring it back.)

import numpy as np
import matplotlib
matplotlib.use('agg')
import matplotlib.pyplot as plt
# from matplotlib.cbook import report_memory

import os, sys

def report_memory(i=0):  # argument may go away
    'return the memory consumed by process'
    from matplotlib.compat.subprocess import Popen, PIPE
    pid = os.getpid()
    if sys.platform == 'sunos5':
        try:
            a2 = Popen('ps -p %d -o osz' % pid, shell=True,
                       stdout=PIPE).stdout.readlines()
        except OSError:
            raise NotImplementedError(
                "report_memory works on Sun OS only if "
                "the 'ps' program is found")
        mem = int(a2[-1].strip())
    elif sys.platform.startswith('linux'):
        try:
            a2 = Popen('ps -p %d -o rss,sz' % pid, shell=True,
                       stdout=PIPE).stdout.readlines()
        except OSError:
            raise NotImplementedError(
                "report_memory works on Linux only if "
                "the 'ps' program is found")
        mem = int(a2[1].split()[1])
    elif sys.platform.startswith('darwin'):
        try:
            a2 = Popen('ps -p %d -o rss,vsz' % pid, shell=True,
                       stdout=PIPE).stdout.readlines()
        except OSError:
            raise NotImplementedError(
                "report_memory works on Mac OS only if "
                "the 'ps' program is found")
        mem = int(a2[1].split()[0])
    elif sys.platform.startswith('win'):
        try:
            a2 = Popen(["tasklist", "/nh", "/fi", "pid eq %d" % pid],
                       stdout=PIPE).stdout.read()
        except OSError:
            raise NotImplementedError(
                "report_memory works on Windows only if "
                "the 'tasklist' program is found")
        mem = int(a2.strip().split()[-2].replace(',', ''))
    else:
        raise NotImplementedError(
            "We don't have a memory monitor for %s" % sys.platform)
    return mem


np.random.seed(0)
z = np.random.randn(500, 100)

for i in range(200):
    fig, ax = plt.subplots()
    ax.contourf(z)  # , corner_mask='legacy')
    fig.savefig('temp.png')
    plt.close(fig)
    if i % 10 == 0:
        print(i, report_memory(i))

[efiring]

Ah, yes, #5360 replaced cbook.report_memory with unit/memleak.py, but I don't see how to use it for a case such as the present one.

[ianthomas23]

Confirmed, major gaffe, fix on its way.

[tacaswell]

Closed by #6942