Update codegen params and doc (#3228)

* update decoding

* update doc

Author: gongenlei

examples/code_generation/codegen/README.md

@@ -38,7 +38,13 @@
 
 
 ## 效果展示
-- 解算法题。求解无重复字符的最长子串的长度
+
+- Github Copilot代码提示效果展示
+<p align="center">
+<img src="https://user-images.githubusercontent.com/24390500/189046785-6c04a3c3-ce89-4684-9aff-a7dc2e7a7041.gif"/> <br />
+</p>
+
+- 解算法题效果展示。求解无重复字符的最长子串的长度
 ```python
 from paddlenlp import Taskflow
 

examples/code_generation/codegen/codegen_server.py

@@ -32,7 +32,7 @@ class DefaultConfig:
     repetition_penalty = 1.0
     min_length = 0
     max_length = 16
-    decode_strategy = "sampling"
+    decode_strategy = "greedy_search"
     load_state_as_np = True
     use_faster = True
     use_fp16_decoding = True
@@ -104,9 +104,7 @@ async def gen(item: Input):
     logger.info("Finish generating code")
     end_time = time.time()
     logger.info(f"Time cost: {end_time - start_time}")
-    output = tokenizer.decode(output[0],
-                              skip_special_tokens=True,
-                              spaces_between_special_tokens=False)
+    output = tokenizer.decode(output[0], skip_special_tokens=True)
     logger.info(f"Generated code: {output}")
     output_json = Output(
         id=random_completion_id(),