Fix flaky test for sensitivity analysis

Summary:
This fixes a flaky test for sensitivity analysis. Currently the QMC
integration done for computing Sobol indices is seeded for reproducibility.
That done for computing derivative-based sensitivity measures is not. This diff
changes that so that the derivative-based measures will also have seeded QMC
with the same seed, to match Sobol indices.

A side effect of this is that it fixes the flaky test, since the results are no
longer random based on the QMC points.

Reviewed By: bernardbeckerman

Differential Revision: D54855136

ax/utils/sensitivity/derivative_measures.py

@@ -73,7 +73,7 @@ def __init__(
         if input_qmc:
             # pyre-fixme[4]: Attribute must be annotated.
             self.input_mc_samples = (
-                draw_sobol_samples(bounds=bounds, n=num_mc_samples, q=1)
+                draw_sobol_samples(bounds=bounds, n=num_mc_samples, q=1, seed=1234)
                 .squeeze(1)
                 .to(dtype)
             )

ax/utils/sensitivity/tests/test_sensitivity.py

@@ -271,23 +271,23 @@ def test_SobolGPMean(self) -> None:
         # Test with signed
         model_bridge = get_modelbridge(modular=True)
         # Unsigned
+        sobol_kwargs = {"input_qmc": True, "num_mc_samples": 10}
         ind_dict = ax_parameter_sens(
             model_bridge,  # pyre-ignore
-            input_qmc=True,
-            num_mc_samples=10,
             order="total",
             signed=False,
+            **sobol_kwargs,  # pyre-ignore
         )
         ind_deriv = compute_derivatives_from_model_list(
             model_list=[model_bridge.model.surrogate.model],
             bounds=torch.tensor(model_bridge.model.search_space_digest.bounds).T,
+            **sobol_kwargs,
         )
         ind_dict_signed = ax_parameter_sens(
             model_bridge,  # pyre-ignore
-            input_qmc=True,
-            num_mc_samples=10,
             order="total",
             # signed=True
+            **sobol_kwargs,  # pyre-ignore
         )
         for i, pname in enumerate(["x1", "x2"]):
             self.assertEqual(