moved Singleton class to a better place

work related to [https://bugzilla.ipr.univ-rennes.fr/show_bug.cgi?id=3958]

iprbench/core.py

@@ -9,15 +9,6 @@ BenchParamType = Union[int, str]
 BenchmarkConfig = Dict[BenchParamId, BenchParamType]
 
 
-class Singleton(type):
-    _instances = {}
-
-    def __call__(cls, *args, **kwargs):
-        if cls not in cls._instances:
-            cls._instances[cls] = super(type(cls), cls).__call__(*args, **kwargs)  # pylint: disable=bad-super-call, no-member
-        return cls._instances[cls]
-
-
 class BenchParam():
     '''a parameter of a benchmark
 

iprbench/main.py

@@ -1,6 +1,7 @@
-from .core import BenchmarkId, IBenchmark, Singleton
+from .core import BenchmarkId, IBenchmark
 from .benchmarks.hibench import HiBench
 from .benchmarks.mamul1 import MaMul1
+from .util import Singleton
 import logging
 import argparse
 from pathlib import Path

iprbench/util.py

@@ -5,6 +5,15 @@ import shutil
 import logging
 
 
+class Singleton(type):
+    _instances = {}
+
+    def __call__(cls, *args, **kwargs):
+        if cls not in cls._instances:
+            cls._instances[cls] = super(type(cls), cls).__call__(*args, **kwargs)  # pylint: disable=bad-super-call, no-member
+        return cls._instances[cls]
+
+
 def _extract_res_dir_using_py_3_7(dir_resource_package: str, dest_path: Path):
     dest_path.mkdir(parents=True, exist_ok=True)
     dir_contents = importlib.resources.contents(dir_resource_package)