MAINT: move gc.collect to function (from review)

2 files changed, 27 insertions, 9 deletions

diff --git a/numpy/core/tests/test_multiarray.py b/numpy/core/tests/test_multiarray.py
index 5bab992fa..b29daa675 100644
--- a/numpy/core/tests/test_multiarray.py
+++ b/numpy/core/tests/test_multiarray.py
@@ -36,7 +36,7 @@ from numpy.testing import (
     assert_, assert_raises, assert_warns, assert_equal, assert_almost_equal,
     assert_array_equal, assert_raises_regex, assert_array_almost_equal,
     assert_allclose, IS_PYPY, HAS_REFCOUNT, assert_array_less, runstring,
-    temppath, suppress_warnings
+    temppath, suppress_warnings, break_cycles,
     )
 from numpy.core.tests._locales import CommaDecimalPointLocale
 
@@ -3784,7 +3784,7 @@ class TestPickling(object):
                         a, pickle.loads(pickle.dumps(a, protocol=proto)),
                         err_msg="%r" % a)
             del a, DATA, carray
-            gc.collect(); gc.collect(); gc.collect()
+            break_cycles()
             # check for reference leaks (gh-12793)
             for ref in refs:
                 assert ref() is None
@@ -7181,7 +7181,7 @@ class TestMemEventHook(object):
         # needs to be larger then limit of small memory cacher in ctors.c
         a = np.zeros(1000)
         del a
-        gc.collect(); gc.collect(); gc.collect()
+        break_cycles()
         _multiarray_tests.test_pydatamem_seteventhook_end()
 
 class TestMapIter(object):
@@ -7753,12 +7753,12 @@ class TestCTypes(object):
 
         # `ctypes_ptr` should hold onto `arr`
         del arr
-        gc.collect(); gc.collect(); gc.collect()
+        break_cycles()
         assert_(arr_ref() is not None, "ctypes pointer did not hold onto a reference")
 
         # but when the `ctypes_ptr` object dies, so should `arr`
         del ctypes_ptr
-        gc.collect(); gc.collect(); gc.collect()
+        break_cycles()
         assert_(arr_ref() is None, "unknowable whether ctypes pointer holds a reference")
 
 
@@ -7940,15 +7940,15 @@ class TestArrayFinalize(object):
         assert_(isinstance(obj_subarray, RaisesInFinalize))
 
         # reference should still be held by obj_arr
-        gc.collect(); gc.collect(); gc.collect()
+        break_cycles()
         assert_(obj_ref() is not None, "object should not already be dead")
 
         del obj_arr
-        gc.collect(); gc.collect(); gc.collect()
+        break_cycles()
         assert_(obj_ref() is not None, "obj_arr should not hold the last reference")
 
         del obj_subarray
-        gc.collect(); gc.collect(); gc.collect()
+        break_cycles()
         assert_(obj_ref() is None, "no references should remain")
 
 
diff --git a/numpy/testing/_private/utils.py b/numpy/testing/_private/utils.py
index 3ace84415..24e26d65c 100644
--- a/numpy/testing/_private/utils.py
+++ b/numpy/testing/_private/utils.py
@@ -6,6 +6,7 @@ from __future__ import division, absolute_import, print_function
 
 import os
 import sys
+import platform
 import re
 import gc
 import operator
@@ -39,6 +40,7 @@ __all__ = [
         'SkipTest', 'KnownFailureException', 'temppath', 'tempdir', 'IS_PYPY',
         'HAS_REFCOUNT', 'suppress_warnings', 'assert_array_compare',
         '_assert_valid_refcount', '_gen_alignment_data', 'assert_no_gc_cycles',
+        'break_cycles',
         ]
 
 
@@ -50,7 +52,7 @@ class KnownFailureException(Exception):
 KnownFailureTest = KnownFailureException  # backwards compat
 verbose = 0
 
-IS_PYPY = '__pypy__' in sys.modules
+IS_PYPY = platform.python_implementation() == 'PyPy'
 HAS_REFCOUNT = getattr(sys, 'getrefcount', None) is not None
 
 
@@ -2324,3 +2326,19 @@ def assert_no_gc_cycles(*args, **kwargs):
     args = args[1:]
     with _assert_no_gc_cycles_context(name=func.__name__):
         func(*args, **kwargs)
+
+def break_cycles():
+    """
+    Break reference cycles by calling gc.collect
+    Objects can call other objects' methods (for instance, another object's
+     __del__) inside their own __del__. On PyPy, the interpreter only runs
+    between calls to gc.collect, so multiple calls are needed to completely
+    release all cycles.
+    """
+
+    gc.collect()
+    if IS_PYPY:
+        # interpreter runs now, to call deleted objects' __del__ methods
+        gc.collect()
+        # one more, just to make sure
+        gc.collect()