TST: Skip tests that use a large amount of memory by default (#31007)

QuLogic · web-flow · commit 54d385671c98 · 2026-02-20T14:55:23.000-05:00
* TST: Reduce memory usage of test_downsample_interpolation_stage

By cutting the grid by one-tenth in each dimension, this cuts memory
usage from 1.0GiB to 65.2MiB. I temporarily added an assert in
`_ImageBase._make_image` to confirm that the interpolation stage did
correctly switch to 'rgba' as well.

* TST: Delete test_invisible_Line_rendering

This test tries to check for slowdowns, which is inherently flaky (as
noted by the comment), and we don't check `set_visible` for other
artists.

* TST: Skip tests that use a large amount of memory by default

According to memray, these tests use fairly large amounts of memory:
- lib/matplotlib/tests/test_simplification.py::test_throw_rendering_complexity_exceeded: 2.2GiB
- lib/matplotlib/tests/test_agg.py::test_chunksize_fails: 2.0GiB
- lib/matplotlib/tests/test_image.py::test_large_image[png-col-16777216-2\\*\\*24 rows-upper]: 1.0GiB
- lib/matplotlib/tests/test_image.py::test_large_image[png-col-16777216-2\\*\\*24 rows-lower]: 1.0GiB
- lib/matplotlib/tests/test_image.py::test_large_image[png-row-8388608-2\\*\\*23 columns-lower]: 537.8MiB
- lib/matplotlib/tests/test_image.py::test_large_image[png-row-8388608-2\\*\\*23 columns-upper]: 537.8MiB

The next closest tests use just 216MiB, then 145.5MiB, etc. and then the
majority under 100MiB.

If you're unlucky, with 4-way xdist you might use upwards of 6GiB RAM if
you get all these on separate processes.

The above tests are all fairly low-level checks for Agg renderer limits
that are not likely to change often, so skip them by default unless on
CI.
diff --git a/doc/devel/testing.rst b/doc/devel/testing.rst
@@ -52,6 +52,9 @@ In the root directory of your development repository run::
 ``--capture=no`` or ``-s``     Do not capture stdout
 =============================  ===========
 
+Some tests may use a large amount of memory (>0.5GiB); to enable those tests, set the
+environment variable ``MPL_TEST_EXPENSIVE``.
+
 To run a single test from the command line, you can provide a file path, optionally
 followed by the function separated by two colons, e.g., (tests do not need to be
 installed, but Matplotlib should be)::
diff --git a/lib/matplotlib/testing/conftest.py b/lib/matplotlib/testing/conftest.py
@@ -1,5 +1,8 @@
-import pytest
+import os
 import sys
+
+import pytest
+
 import matplotlib
 from matplotlib import _api
 
@@ -80,6 +83,13 @@ def mpl_test_settings(request):
                 matplotlib.use(prev_backend)
 
 
+@pytest.fixture
+def high_memory(pytestconfig):
+    from matplotlib.testing import is_ci_environment
+    if not (os.environ.get('MPL_TEST_EXPENSIVE') or is_ci_environment()):
+        pytest.skip('Test uses too much memory')
+
+
 @pytest.fixture
 def pd():
     """
diff --git a/lib/matplotlib/testing/conftest.pyi b/lib/matplotlib/testing/conftest.pyi
@@ -7,6 +7,8 @@ def pytest_unconfigure(config: pytest.Config) -> None: ...
 @pytest.fixture
 def mpl_test_settings(request: pytest.FixtureRequest) -> None: ...
 @pytest.fixture
+def high_memory(pytestconfig: pytest.Config) -> None: ...
+@pytest.fixture
 def pd() -> ModuleType: ...
 @pytest.fixture
 def xr() -> ModuleType: ...
diff --git a/lib/matplotlib/tests/conftest.py b/lib/matplotlib/tests/conftest.py
@@ -1,2 +1,3 @@
 from matplotlib.testing.conftest import (  # noqa
-    mpl_test_settings, pytest_configure, pytest_unconfigure, pd, text_placeholders, xr)
+    pytest_configure, pytest_unconfigure,
+    high_memory, mpl_test_settings, pd, text_placeholders, xr)
diff --git a/lib/matplotlib/tests/test_agg.py b/lib/matplotlib/tests/test_agg.py
@@ -328,7 +328,7 @@ def test_draw_path_collection_error_handling():
         fig.canvas.draw()
 
 
-def test_chunksize_fails():
+def test_chunksize_fails(high_memory):
     # NOTE: This test covers multiple independent test scenarios in a single
     #       function, because each scenario uses ~2GB of memory and we don't
     #       want parallel test executors to accidentally run multiple of these
diff --git a/lib/matplotlib/tests/test_image.py b/lib/matplotlib/tests/test_image.py
@@ -1555,7 +1555,7 @@ def test_downsample_interpolation_stage(fig_test, fig_ref):
     # Fixing random state for reproducibility
     np.random.seed(19680801)
 
-    grid = np.random.rand(4000, 4000)
+    grid = np.random.rand(400, 400)
     ax = fig_ref.subplots()
     ax.imshow(grid, interpolation='auto', cmap='viridis',
               interpolation_stage='rgba')
@@ -1583,7 +1583,7 @@ def test_rc_interpolation_stage():
     'dim, size, msg', [['row', 2**23, r'2\*\*23 columns'],
                        ['col', 2**24, r'2\*\*24 rows']])
 @check_figures_equal()
-def test_large_image(fig_test, fig_ref, dim, size, msg, origin):
+def test_large_image(fig_test, fig_ref, dim, size, msg, origin, high_memory):
     # Check that Matplotlib downsamples images that are too big for AGG
     # See issue #19276. Currently the fix only works for png output but not
     # pdf or svg output.
diff --git a/lib/matplotlib/tests/test_lines.py b/lib/matplotlib/tests/test_lines.py
@@ -4,7 +4,6 @@
 
 import itertools
 import platform
-import timeit
 from types import SimpleNamespace
 
 from cycler import cycler
@@ -31,52 +30,6 @@ def test_segment_hits():
     assert_array_equal(mlines.segment_hits(cx, cy, x, y, radius), [0])
 
 
-# Runtimes on a loaded system are inherently flaky. Not so much that a rerun
-# won't help, hopefully.
-@pytest.mark.flaky(reruns=5)
-def test_invisible_Line_rendering():
-    """
-    GitHub issue #1256 identified a bug in Line.draw method
-
-    Despite visibility attribute set to False, the draw method was not
-    returning early enough and some pre-rendering code was executed
-    though not necessary.
-
-    Consequence was an excessive draw time for invisible Line instances
-    holding a large number of points (Npts> 10**6)
-    """
-    # Creates big x and y data:
-    N = 10**7
-    x = np.linspace(0, 1, N)
-    y = np.random.normal(size=N)
-
-    # Create a plot figure:
-    fig = plt.figure()
-    ax = plt.subplot()
-
-    # Create a "big" Line instance:
-    l = mlines.Line2D(x, y)
-    l.set_visible(False)
-    # but don't add it to the Axis instance `ax`
-
-    # [here Interactive panning and zooming is pretty responsive]
-    # Time the canvas drawing:
-    t_no_line = min(timeit.repeat(fig.canvas.draw, number=1, repeat=3))
-    # (gives about 25 ms)
-
-    # Add the big invisible Line:
-    ax.add_line(l)
-
-    # [Now interactive panning and zooming is very slow]
-    # Time the canvas drawing:
-    t_invisible_line = min(timeit.repeat(fig.canvas.draw, number=1, repeat=3))
-    # gives about 290 ms for N = 10**7 pts
-
-    slowdown_factor = t_invisible_line / t_no_line
-    slowdown_threshold = 2  # trying to avoid false positive failures
-    assert slowdown_factor < slowdown_threshold
-
-
 def test_set_line_coll_dash():
     fig, ax = plt.subplots()
     np.random.seed(0)
diff --git a/lib/matplotlib/tests/test_simplification.py b/lib/matplotlib/tests/test_simplification.py
@@ -455,7 +455,7 @@ def test_start_with_moveto():
     assert segs[0][1] == Path.MOVETO
 
 
-def test_throw_rendering_complexity_exceeded():
+def test_throw_rendering_complexity_exceeded(high_memory):
     plt.rcParams['path.simplify'] = False
     xx = np.arange(2_000_000)
     yy = np.random.rand(2_000_000)
diff --git a/lib/mpl_toolkits/axes_grid1/tests/conftest.py b/lib/mpl_toolkits/axes_grid1/tests/conftest.py
@@ -1,2 +1,3 @@
-from matplotlib.testing.conftest import (mpl_test_settings,  # noqa
-                                         pytest_configure, pytest_unconfigure)
+from matplotlib.testing.conftest import (  # noqa
+    pytest_configure, pytest_unconfigure,
+    high_memory, mpl_test_settings)
diff --git a/lib/mpl_toolkits/axisartist/tests/conftest.py b/lib/mpl_toolkits/axisartist/tests/conftest.py
@@ -1,2 +1,3 @@
-from matplotlib.testing.conftest import (mpl_test_settings,  # noqa
-                                         pytest_configure, pytest_unconfigure)
+from matplotlib.testing.conftest import (  # noqa
+    pytest_configure, pytest_unconfigure,
+    high_memory, mpl_test_settings)
diff --git a/lib/mpl_toolkits/mplot3d/tests/conftest.py b/lib/mpl_toolkits/mplot3d/tests/conftest.py
@@ -1,2 +1,3 @@
-from matplotlib.testing.conftest import (mpl_test_settings,  # noqa
-                                         pytest_configure, pytest_unconfigure)
+from matplotlib.testing.conftest import (  # noqa
+    pytest_configure, pytest_unconfigure,
+    high_memory, mpl_test_settings)
