saves some VRAM for 1 GPU training

RWKV-v4/train.py

@@ -217,6 +217,17 @@ if __name__ == '__main__':
         "gradient_clipping": 1.0,
         "gradient_accumulation_steps": 1,
     }
+    if NUM_GPUS == 1:
+        DEEPSPEED_CFG['zero_optimization'] = {
+            "stage":1, # saves some VRAM
+            "contiguous_gradients":False,
+            "overlap_comm":False,
+            "allgather_partitions":False,
+            "reduce_scatter":False,
+            "allgather_bucket_size":200000000,
+            "reduce_bucket_size":200000000,
+            "sub_group_size":1000000000000
+        }
     
     if os.environ['RWKV_FLOAT_MODE'] == 'fp16':
         DEEPSPEED_CFG["fp16"] = {