Fix uniform real dimension interval mapping to ConfigSpace

src/orion/algo/space/configspace.py

@@ -71,12 +71,19 @@ def dimension(self, dim: Dimension) -> None:
     def real(self, dim: Real) -> FloatHyperparameter:
         """Convert a real dimension into a configspace equivalent"""
         if dim.prior_name in ("reciprocal", "uniform"):
-            a, b = dim._args
+
+            # NB: scipy uniform [loc, scale], configspace [min, max] with max = loc + scale, loc = min
+            if dim.prior_name == "uniform":
+                loc, scale = dim._args
+                lower = loc
+                upper = loc + scale
+            else:
+                lower, upper = dim._args
 
             return UniformFloatHyperparameter(
                 name=dim.name,
-                lower=a,
-                upper=b,
+                lower=lower,
+                upper=upper,
                 default_value=dim.default_value,
                 q=_qantization(dim),
                 log=dim.prior_name == "reciprocal",
@@ -102,13 +109,19 @@ def real(self, dim: Real) -> FloatHyperparameter:
 
     def integer(self, dim: Integer) -> IntegerHyperparameter:
         """Convert a integer dimension into a configspace equivalent"""
+
         if dim.prior_name in ("int_uniform", "int_reciprocal"):
-            a, b = dim._args
+            if dim.prior_name == "int_uniform":
+                loc, scale = dim._args
+                lower = loc
+                upper = loc + scale
+            else:
+                lower, upper = dim._args
 
             return UniformIntegerHyperparameter(
                 name=dim.name,
-                lower=a,
-                upper=b,
+                lower=lower,
+                upper=upper,
                 default_value=dim.default_value,
                 q=_qantization(dim),
                 log=dim.prior_name == "int_reciprocal",
@@ -203,12 +216,18 @@ def _from_uniform(dim: Hyperparameter) -> Integer | Real:
     else:
         kwargs["precision"] = int(-log10(dim.q)) if dim.q else 4
 
-    dist = "uniform"
-    args.append(dim.lower)
-    args.append(dim.upper)
-
     if dim.log:
         dist = "reciprocal"
+        args.append(dim.lower)
+        args.append(dim.upper)
+    else:
+        # NB: scipy uniform [loc, scale], configspace [min, max] with max = loc + scale, loc = min
+        loc = dim.lower
+        scale = dim.upper - dim.lower
+
+        dist = "uniform"
+        args.append(loc)
+        args.append(scale)
 
     return klass(dim.name, dist, *args, **kwargs)
 

tests/unittests/algo/test_configspace.py

@@ -10,15 +10,21 @@
 def test_orion_configspace():
     space = Space()
 
+    # NB: scipy uniform [loc, scale], configspace [min, max] with max = loc + scale, loc = min
+    def uniform(type, name, low, high, **kwargs):
+        return type(name, "uniform", low, high - low, **kwargs)
+
     space.register(Integer("r1i", "reciprocal", 1, 6))
-    space.register(Integer("u1i", "uniform", -3, 6))
-    space.register(Integer("u2i", "uniform", -3, 6))
-    space.register(Integer("u3i", "uniform", -3, 6, default_value=2))
+    space.register(uniform(Integer, "u1i", -3, 6))
+    space.register(uniform(Integer, "u2i", -3, 6))
+    space.register(uniform(Integer, "u4i", -4, 0, default_value=-1))
+    space.register(uniform(Integer, "u3i", -3, 6, default_value=2))
 
     space.register(Real("r1f", "reciprocal", 1, 6))
-    space.register(Real("u1f", "uniform", -3, 6))
-    space.register(Real("u2f", "uniform", -3, 6))
-    space.register(Real("name.u2f", "uniform", -3, 6))
+    space.register(uniform(Real, "u1f", -3, 6))
+    space.register(uniform(Real, "u2f", -3, 6))
+    space.register(uniform(Real, "u4f", -4, 0, default_value=-0.2))
+    space.register(uniform(Real, "name.u2f", -3, 6))
 
     space.register(Categorical("c1", ("asdfa", 2)))
     space.register(Categorical("c2", dict(a=0.2, b=0.8)))