Fix Mamba2 Grouped SSD Support in the torch_forward Path (#37533)

* Fix mamba2 grouped support in bamba torch path

* patch zamba2 and mamba2

* Add a unit test for grouped SSD

* add comment for the new unit test

* add output_size arg value to repeat_interleave calls

* Add comment

tests/models/mamba2/test_modeling_mamba2.py

@@ -238,6 +238,14 @@ class Mamba2ModelTest(ModelTesterMixin, GenerationTesterMixin, PipelineTesterMix
         config_and_inputs = self.model_tester.prepare_config_and_inputs()
         self.model_tester.create_and_check_mamba2_slow_vs_fast_forward(*config_and_inputs)
 
+    # This test adjusts n_groups to half the original setting and effectively
+    # creates a grouped SSD configuration in the mamba2 layers
+    # See https://github.com/huggingface/transformers/pull/37533/
+    def test_mamba2_slow_vs_fast_forward_grouped(self):
+        config_and_inputs = self.model_tester.prepare_config_and_inputs()
+        config_and_inputs[0].n_groups //= 2
+        self.model_tester.create_and_check_mamba2_slow_vs_fast_forward(*config_and_inputs)
+
     def test_initialization(self):
         config, _ = self.model_tester.prepare_config_and_inputs_for_common()