fix gemma4 num attention head bugs (from #7975)

deepspeed/runtime/sequence_parallel/ulysses_sp.py

@@ -491,14 +491,19 @@ def register_with_transformers(
             local_seq_length = seq_length // mpu.get_sequence_parallel_world_size()
             global_seq_length = seq_length
 
+        arch_cfg = hf_model_config.get_text_config()
+
         uattn = UlyssesSPAttentionHF(
             attn=core_attn_function,
             batch_size=micro_batch_size,
-            attn_head_count=hf_model_config.num_attention_heads,
-            attn_head_size=getattr(hf_model_config, "head_dim",
-                                   hf_model_config.hidden_size // hf_model_config.num_attention_heads),
-            kv_head_count=hf_model_config.num_key_value_heads,
-            num_hidden_layers=hf_model_config.num_hidden_layers,
+            attn_head_count=arch_cfg.num_attention_heads,
+            attn_head_size=getattr(
+                arch_cfg,
+                "head_dim",
+                arch_cfg.hidden_size // arch_cfg.num_attention_heads,
+            ),
+            kv_head_count=arch_cfg.num_key_value_heads,
+            num_hidden_layers=arch_cfg.num_hidden_layers,
             process_group=mpu.get_sequence_parallel_group(),
             seq_length_is_variable=seq_length_is_variable,
             local_seq_length=local_seq_length,

tests/unit/multimodal/__init__.py

@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: Apache-2.0
+# DeepSpeed Team

tests/unit/multimodal/test_gemma4_config.py

@@ -0,0 +1,27 @@
+# SPDX-License-Identifier: Apache-2.0
+# DeepSpeed Team
+
+from transformers import Gemma4Config
+
+
+def test_gemma4_text_config_fallback():
+    config = Gemma4Config()
+    assert not hasattr(config, 'num_attention_heads'), \
+        "Gemma4Config top-level should not have num_attention_heads"
+    arch_cfg = config.get_text_config()
+    assert hasattr(arch_cfg, 'num_attention_heads')
+    assert arch_cfg.num_attention_heads > 0
+    assert hasattr(arch_cfg, 'num_key_value_heads')
+    assert arch_cfg.num_key_value_heads > 0
+    assert hasattr(arch_cfg, 'num_hidden_layers')
+    assert arch_cfg.num_hidden_layers > 0
+    assert hasattr(arch_cfg, 'hidden_size')
+    assert arch_cfg.hidden_size > 0
+
+
+def test_gemma4_text_config_matches_text_config():
+    config = Gemma4Config()
+    arch_cfg = config.get_text_config()
+    assert arch_cfg is config.text_config
+    assert arch_cfg.num_attention_heads == config.text_config.num_attention_heads
+    assert arch_cfg.num_key_value_heads == config.text_config.num_key_value_heads