simplify version file. (#1203)

* simplify version file.
* add code fingerprint to avoid rebuild unchange code.

Author: xuhancn

.gitignore

@@ -91,7 +91,7 @@ torch/test/
 torch/version.py
 
 intel_extension_for_pytorch/version.py
-csrc/utils/version.cpp
+csrc/utils/version.h
 
 cscope.*
 

csrc/utils/version.h

@@ -298,6 +298,24 @@ def get_build_version(ipex_git_sha):
     return ipex_version
 
 
+def generate_code_fingerprint(ipex_build_version, ipex_git_sha, torch_git_sha, build_mode):
+    fingerprint = "{}_{}_{}_{}".format(ipex_build_version, ipex_git_sha, torch_git_sha, build_mode)
+    return fingerprint
+
+def check_code_fingerprint_in_file(file_path, fingerprint):
+    b_exist = os.path.isfile(file_path)
+    if b_exist is False:
+        return False
+
+    with open(file_path) as file:
+        # read all content of a file
+        content = file.read()
+        # check if string present in a file
+        if fingerprint in content:
+            return True
+        else:
+            return False
+
 def create_version_files(base_dir, ipex_build_version, ipex_git_sha, torch_git_sha):
     def write_buffer_to_file(file_path, buffer):
         write_buffer_flag = True
@@ -315,7 +333,7 @@ def write_buffer_to_file(file_path, buffer):
 
     print('Building Intel Extension for PyTorch. Version: {}'.format(ipex_build_version))
     py_version_path = os.path.join(base_dir, package_name, 'version.py')
-    cpp_version_path = os.path.join(base_dir, package_name, '..', 'csrc', 'utils', 'version.cpp')
+    cpp_version_path = os.path.join(base_dir, package_name, '..', 'csrc', 'utils', 'version.h')
 
     py_buffer = "# Autogenerated file, do not edit!\n"
     py_buffer += "__version__ = '{}'\n".format(ipex_build_version)
@@ -326,9 +344,15 @@ def write_buffer_to_file(file_path, buffer):
         mode_str = "debug"
     py_buffer += "__mode__ = '{}'\n".format(mode_str)
 
+    current_code_fingerprint = generate_code_fingerprint(ipex_build_version, ipex_git_sha, torch_git_sha, mode_str)
+    b_same_fingerprint = check_code_fingerprint_in_file(cpp_version_path, current_code_fingerprint)
+    if b_same_fingerprint is True:
+        return
+
     c_buffer = '// Autogenerated file, do not edit!\n'
-    # c_buffer += '#include "intel_extension_for_pytorch/csrc/version.h"\n\n'
-    c_buffer += '#include "version.h"\n\n'
+    c_buffer += '// code fingerprint: {}\n\n'.format(current_code_fingerprint)
+    c_buffer += '#pragma once\n'
+    c_buffer += '#include <string>\n\n'
     c_buffer += 'namespace torch_ipex {\n\n'
     c_buffer += 'const std::string __version__()\n'.format(ipex_build_version)
     c_buffer += '{{ return "{}"; }}\n\n'.format(ipex_build_version)