fix bug of backend (#294)

README.md

@@ -57,14 +57,14 @@ pip install auto-round
 ### Basic Usage (Gaudi2/CPU/GPU)
 
 A user guide detailing the full list of supported arguments is provided by calling ```auto-round -h``` on the terminal.
-Alternatively, you can use ```auto_round``` instead of ```auto-round```.
+Alternatively, you can use ```auto_round``` instead of ```auto-round```. Set the format you want in `format` and multiple formats exporting has been supported. 
 
 ```bash
 CUDA_VISIBLE_DEVICES=0 auto-round \
     --model facebook/opt-125m \
     --bits 4 \
     --group_size 128 \
-    --format auto_round \
+    --format "auto_round,auto_gptq" \
     --disable_eval \
     --output_dir ./tmp_autoround
 ```

auto_round/backend.py

@@ -137,7 +137,7 @@ def feature_num_greater_checker(in_feature, out_feature, num):
                                                requirements=["intel-extension-for-transformers"])
 
 BackendInfos['auto_round:qbits_zp'] = BackendInfo(device=["cpu"], sym=[True, False],
-                                                  packing_format="qbits",
+                                                  packing_format="qbits_zp+-1",
                                                   bits=[2, 4, 8], group_size=None,
                                                   priority=0 if "intel" in get_cpu_manufacturer() else 5,
                                                   feature_checks=[],