fix n_iter report

benchmarks/ridge/solvers/scikit_learn.py

@@ -64,10 +64,20 @@ def run(self, _):
         self.n_iter_ = estimator.n_iter_
 
     def get_result(self):
+        n_iter = self.n_iter_
+        if isinstance(n_iter, list):
+            n_iter = set(n_iter)
+            if len(n_iter) > 1:
+                raise ValueError(
+                    "In multitarget mode, the same number of iterations is expected "
+                    "for all targets, to keep reports comparable."
+                )
+            n_iter = n_iter.pop()
+
         return dict(
             weights=self.weights,
             intercept=self.intercept,
-            n_iter=self.n_iter_,
+            n_iter=n_iter,
             version_info=f"scikit-learn {version('scikit-learn')}",
             __name=self.name,
             **self._parameters,