Merge pull request scipy#23153 from crusaderky/tst-optimize-mem

TST: optimize: cap pytest-run-parallel memory usage

Author: tylerjereddy

scipy/optimize/tests/test_least_squares.py

@@ -400,6 +400,7 @@ def test_convergence_with_only_one_tolerance_enabled(self):
                                 method=self.method)
             assert_allclose(res.x, x_opt)
 
+    @pytest.mark.parallel_threads(4)  # 0.4 GiB per thread RAM usage
     @pytest.mark.fail_slow(5.0)
     def test_workers(self):
         serial = least_squares(fun_trivial, 2.0, method=self.method)