adding multithreading test

Author: SwayamInSync

quaddtype/numpy_quaddtype/src/scalar.c

@@ -494,7 +494,7 @@ QuadPrecision_as_integer_ratio(QuadPrecisionObject *self, PyObject *Py_UNUSED(ig
     exponent -= FLOAT128_PRECISION;
     ```
     This should work but give non-simplified, huge integers (although they also come down to same representation)
-    We can also do gcd to find simplified values, but it'll add more O(log(N)) {which in theory seem better}
+    We can also do gcd to find simplified values, but it'll add more O(log(N))
     For the sake of simplicity and fixed 128-bit nature, we will loop till 113 only
     */
 

quaddtype/tests/test_multithreading.py

@@ -0,0 +1,36 @@
+import concurrent.futures
+import threading
+
+import pytest
+
+import numpy as np
+from numpy._core import _rational_tests
+from numpy._core.tests.test_stringdtype import random_unicode_string_list
+from numpy.testing import IS_64BIT, IS_WASM
+from numpy.testing._private.utils import run_threaded
+
+if IS_WASM:
+    pytest.skip(allow_module_level=True, reason="no threading support in wasm")
+
+pytestmark = pytest.mark.thread_unsafe(
+    reason="tests in this module are already explicitly multi-threaded"
+)
+
+from numpy_quaddtype import *
+
+
+def test_as_integer_ratio_reconstruction():
+    """Multi-threaded test that as_integer_ratio() can reconstruct the original value."""
+    values = ["3.14", "0.1", "1.414213562373095", "2.718281828459045",
+    "-1.23456789", "1000.001", "0.0001", "1e20", "1.23e15", "1e-30", pi]
+
+    def test(barrier):
+      barrier.wait() # All threads start simultaneously
+      for val in values:
+        quad_val = QuadPrecision(val)
+        num, denom = quad_val.as_integer_ratio()
+        # todo: can remove str converstion after merging PR #213
+        reconstructed = QuadPrecision(str(num)) / QuadPrecision(str(denom))
+        assert reconstructed == quad_val
+    
+    run_threaded(test, pass_barrier=True, max_workers=64, outer_iterations=100)