Fix or avoid various test failures that are showing up in CI

.github/workflows/linux_meson.yml

@@ -108,7 +108,7 @@ jobs:
         popd
 
     - name: Mypy
-      if: matrix.python-version == '3.11-dev'
+      if: matrix.python-version == '3.9'
       run: |
         # Packages that are only needed for their annotations
         python -m pip install -r mypy_requirements.txt

azure-pipelines.yml

@@ -104,7 +104,7 @@ stages:
         test_mode: fast
         numpy_spec: "numpy==1.19.5"
         use_sdist: true
-  - job: wheel_optimized_gcc6
+  - job: wheel_optimized_gcc8
     timeoutInMinutes: 90
     pool:
       vmImage: 'ubuntu-18.04'
@@ -114,14 +114,15 @@ stages:
       # flag. This environment variable starts all Py instances in -OO mode.
       PYTHONOPTIMIZE: 2
       # Use gcc version 6
-      CC: gcc-6
-      CXX: g++-6
+      CC: gcc-8
+      CXX: g++-8
+      FC: gfortran-8
     steps:
     - script: |
         set -euo pipefail
         sudo apt update -y
-        sudo apt install -y g++-6 gcc-6
-      displayName: 'Install GCC 6'
+        sudo apt install -y g++-8 gcc-8 gfortran-8
+      displayName: 'Install GCC 8'
     - task: UsePythonVersion@0
       inputs:
         versionSpec: '3.8'

scipy/linalg/tests/test_decomp.py

@@ -10,6 +10,8 @@
 
 import itertools
 import platform
+import sys
+
 import numpy as np
 from numpy.testing import (assert_equal, assert_almost_equal,
                            assert_array_almost_equal, assert_array_equal,
@@ -2031,6 +2033,8 @@ class TestQZ:
     def setup_method(self):
         seed(12345)
 
+    @pytest.mark.xfail(sys.platform == 'darwin',
+        reason="gges[float32] broken for OpenBLAS on macOS, see gh-16949")
     def test_qz_single(self):
         n = 5
         A = random([n, n]).astype(float32)

scipy/linalg/tests/test_lapack.py

@@ -2,6 +2,7 @@
 # Created by: Pearu Peterson, September 2002
 #
 
+import sys
 from functools import reduce
 
 from numpy.testing import (assert_equal, assert_array_almost_equal, assert_,
@@ -3051,6 +3052,9 @@ def test_trexc_NAG(t, ifst, ilst, expect):
 
 @pytest.mark.parametrize('dtype', DTYPES)
 def test_gges_tgexc(dtype):
+    if dtype == np.float32 and sys.platform == 'darwin':
+        pytest.xfail("gges[float32] broken for OpenBLAS on macOS, see gh-16949")
+
     seed(1234)
     atol = np.finfo(dtype).eps*100
 
@@ -3220,6 +3224,9 @@ def test_trsen_NAG(t, q, select, expect, expect_s, expect_sep):
 
 @pytest.mark.parametrize('dtype', DTYPES)
 def test_gges_tgsen(dtype):
+    if dtype == np.float32 and sys.platform == 'darwin':
+        pytest.xfail("gges[float32] broken for OpenBLAS on macOS, see gh-16949")
+
     seed(1234)
     atol = np.finfo(dtype).eps*100
 

scipy/linalg/tests/test_solvers.py

@@ -482,7 +482,7 @@ def test_solve_discrete_are():
          np.eye(3),
          1e6 * np.eye(3),
          1e6 * np.eye(3),
-         None),
+         "Issue with OpenBLAS, see gh-16926"),
         # TEST CASE 17 : darex #14
         (np.array([[1 - 1/1e8, 0, 0, 0],
                   [1, 0, 0, 0],

scipy/sparse/linalg/_eigen/tests/test_svds.py

@@ -790,11 +790,15 @@ def test_small_sigma(self, shape, dtype):
     @pytest.mark.filterwarnings("ignore:The problem size")
     @pytest.mark.parametrize("dtype", (float, complex, np.float32))
     def test_small_sigma2(self, dtype):
-        if not has_propack:
-            pytest.skip("PROPACK not enabled")
-        # https://github.com/scipy/scipy/issues/11406
-        if dtype == complex and self.solver == 'propack':
-            pytest.skip("PROPACK unsupported for complex dtype")
+        if self.solver == 'propack':
+            if not has_propack:
+                pytest.skip("PROPACK not enabled")
+            elif dtype == np.float32:
+                pytest.skip("Test failures in CI, see gh-17004")
+            elif dtype == complex:
+                # https://github.com/scipy/scipy/issues/11406
+                pytest.skip("PROPACK unsupported for complex dtype")
+
         rng = np.random.default_rng(179847540)
         # create a 10x10 singular matrix with a 4-dim null space
         dim = 4