[Test] add test_smallest_possible

tests/test_datatypes.py

 # -*- coding: utf-8 -*-
 
-import finn.core.datatype as dt
+from finn.core.datatype import DataType
 
 
 def test_datatypes():
-    assert dt.DataType.BIPOLAR.allowed(-1)
-    assert dt.DataType.BIPOLAR.allowed(0) is False
-    assert dt.DataType.BINARY.allowed(-1) is False
-    assert dt.DataType.BINARY.allowed(1)
-    assert dt.DataType.UINT2.allowed(2)
-    assert dt.DataType.UINT2.allowed(10) is False
-    assert dt.DataType.UINT3.allowed(5)
-    assert dt.DataType.UINT3.allowed(-7) is False
-    assert dt.DataType.UINT4.allowed(15)
-    assert dt.DataType.UINT4.allowed(150) is False
-    assert dt.DataType.UINT8.allowed(150)
-    assert dt.DataType.UINT8.allowed(777) is False
-    assert dt.DataType.UINT16.allowed(14500)
-    assert dt.DataType.UINT16.allowed(-1) is False
-    assert dt.DataType.UINT32.allowed(2 ** 10)
-    assert dt.DataType.UINT32.allowed(-1) is False
-    assert dt.DataType.INT2.allowed(-1)
-    assert dt.DataType.INT2.allowed(-10) is False
-    assert dt.DataType.INT3.allowed(5) is False
-    assert dt.DataType.INT3.allowed(-2)
-    assert dt.DataType.INT4.allowed(15) is False
-    assert dt.DataType.INT4.allowed(-5)
-    assert dt.DataType.INT8.allowed(150) is False
-    assert dt.DataType.INT8.allowed(-127)
-    assert dt.DataType.INT16.allowed(-1.04) is False
-    assert dt.DataType.INT16.allowed(-7777)
-    assert dt.DataType.INT32.allowed(7.77) is False
-    assert dt.DataType.INT32.allowed(-5)
-    assert dt.DataType.INT32.allowed(5)
+    assert DataType.BIPOLAR.allowed(-1)
+    assert DataType.BIPOLAR.allowed(0) is False
+    assert DataType.BINARY.allowed(-1) is False
+    assert DataType.BINARY.allowed(1)
+    assert DataType.UINT2.allowed(2)
+    assert DataType.UINT2.allowed(10) is False
+    assert DataType.UINT3.allowed(5)
+    assert DataType.UINT3.allowed(-7) is False
+    assert DataType.UINT4.allowed(15)
+    assert DataType.UINT4.allowed(150) is False
+    assert DataType.UINT8.allowed(150)
+    assert DataType.UINT8.allowed(777) is False
+    assert DataType.UINT16.allowed(14500)
+    assert DataType.UINT16.allowed(-1) is False
+    assert DataType.UINT32.allowed(2 ** 10)
+    assert DataType.UINT32.allowed(-1) is False
+    assert DataType.INT2.allowed(-1)
+    assert DataType.INT2.allowed(-10) is False
+    assert DataType.INT3.allowed(5) is False
+    assert DataType.INT3.allowed(-2)
+    assert DataType.INT4.allowed(15) is False
+    assert DataType.INT4.allowed(-5)
+    assert DataType.INT8.allowed(150) is False
+    assert DataType.INT8.allowed(-127)
+    assert DataType.INT16.allowed(-1.04) is False
+    assert DataType.INT16.allowed(-7777)
+    assert DataType.INT32.allowed(7.77) is False
+    assert DataType.INT32.allowed(-5)
+    assert DataType.INT32.allowed(5)
+
+
+def test_smallest_possible():
+    assert DataType.get_smallest_possible(1) == DataType.BINARY
+    assert DataType.get_smallest_possible(1.1) == DataType.FLOAT32
+    assert DataType.get_smallest_possible(-1) == DataType.BIPOLAR
+    assert DataType.get_smallest_possible(-3) == DataType.INT3
+    assert DataType.get_smallest_possible(-3.2) == DataType.FLOAT32