TST: add multithreaded ufunc execution test

numpy/_core/tests/test_multithreading.py

@@ -9,13 +9,31 @@
     pytest.skip(allow_module_level=True, reason="no threading support in wasm")
 
 
-def test_parallel_errstate_creation():
+def run_threaded(func, iters, pass_count=False):
+    with concurrent.futures.ThreadPoolExecutor(max_workers=8) as tpe:
+        if pass_count:
+            futures = [tpe.submit(func, i) for i in range(iters)]
+        else:
+            futures = [tpe.submit(func) for _ in range(iters)]
+        for f in futures:
+            f.result()
+
+
+def test_parallel_randomstate_creation():
     # if the coercion cache is enabled and not thread-safe, creating
     # RandomState instances simultaneously leads to a data race
     def func(seed):
         np.random.RandomState(seed)
 
-    with concurrent.futures.ThreadPoolExecutor(max_workers=8) as tpe:
-        futures = [tpe.submit(func, i) for i in range(500)]
-        for f in futures:
-            f.result()
+    run_threaded(func, 500, pass_count=True)
+
+
+def test_parallel_ufunc_execution():
+    # if the loop data cache or dispatch cache are not thread-safe
+    # computing ufuncs simultaneously in multiple threads leads
+    # to a data race
+    def func():
+        arr = np.random.random((25,))
+        np.unique(arr)
+
+    run_threaded(func, 500)