feat: Use iminuit v1.5.X API (#1202)

* Require iminuit compatible with v1.5.3 in 'minuit' extra
* Adopt iminuit v1.5.3+ API
   - ncalls -> ncalls_total
   - ngrads -> ngrads_total
* Remove mocking of iminuit.Minuit().from_array_func from tests
   - c.f. scikit-hep/iminuit#464

Author: matthewfeickert

setup.py

@@ -9,7 +9,7 @@
     'torch': ['torch~=1.2'],
     'jax': ['jax~=0.2.4', 'jaxlib~=0.1.56'],
     'xmlio': ['uproot3~=3.14'],  # Future proof against uproot4 API changes
-    'minuit': ['iminuit~=1.4.3'],  # v1.5.0 breaks pyhf for 32b TensorFlow and PyTorch
+    'minuit': ['iminuit~=1.5.3'],
 }
 extras_require['backends'] = sorted(
     set(

src/pyhf/optimize/opt_minuit.py

@@ -113,7 +113,7 @@ def _minimize(
         minimizer.tol = tolerance
         minimizer.migrad(ncall=maxiter)
         # Following lines below come from:
-        # https://github.com/scikit-hep/iminuit/blob/22f6ed7146c1d1f3274309656d8c04461dde5ba3/src/iminuit/_minimize.py#L106-L125
+        # https://github.com/scikit-hep/iminuit/blob/64acac11cfa2fb91ccbd02d1b3c51f8a9e2cc484/src/iminuit/_minimize.py#L102-L121
         message = "Optimization terminated successfully."
         if not minimizer.valid:
             message = "Optimization failed."
@@ -141,7 +141,7 @@ def _minimize(
             fun=minimizer.fval,
             hess_inv=hess_inv,
             message=message,
-            nfev=minimizer.ncalls,
-            njev=minimizer.ngrads,
+            nfev=minimizer.ncalls_total,
+            njev=minimizer.ngrads_total,
             minuit=minimizer,
         )

tests/test_optim.py

@@ -420,20 +420,6 @@ def test_minuit_failed_optimization(
     monkeypatch, mocker, has_reached_call_limit, is_above_max_edm
 ):
     class BadMinuit(iminuit.Minuit):
-        @classmethod
-        def from_array_func(cls, *args, **kwargs):
-            """
-            from_array_func won't need mocker in a newer version of iminuit
-
-            See scikit-hep/iminuit#464 for more details
-            """
-            self = super().from_array_func(*args, **kwargs)
-            mock = mocker.MagicMock(wraps=self)
-            mock.valid = False
-            mock.fmin.has_reached_call_limit = has_reached_call_limit
-            mock.fmin.is_above_max_edm = is_above_max_edm
-            return mock
-
         @property
         def valid(self):
             return False