Remove hyperparameter in a configuration space

ConfigSpace/conditions.pyx

@@ -74,6 +74,9 @@ cdef class ConditionComponent(object):
     def evaluate_vector(self, instantiated_vector):
         return bool(self._evaluate_vector(instantiated_vector))
 
+    def get_referenced_hyperparameters(self) -> List[Hyperparameter]:
+        pass
+
     cdef int _evaluate_vector(self, np.ndarray value):
         pass
 
@@ -147,6 +150,9 @@ cdef class AbstractCondition(ConditionComponent):
         hp_name = self.parent.name
         return self._evaluate(instantiated_parent_hyperparameter[hp_name])
 
+    def get_referenced_hyperparameters(self) -> List[Hyperparameter]:
+        return self.get_children() + self.get_parents()
+
     cdef int _evaluate_vector(self, np.ndarray instantiated_vector):
         if self.parent_vector_id is None:
             raise ValueError("Parent vector id should not be None when calling evaluate vector")
@@ -523,6 +529,9 @@ cdef class AbstractConjunction(ConditionComponent):
                 raise ValueError("All Conjunctions and Conditions must have "
                                  "the same child.")
 
+    def get_referenced_hyperparameters(self) -> List[Hyperparameter]:
+        return sum([cond.get_referenced_hyperparameters() for cond in self.components], [])
+
     def __eq__(self, other: Any) -> bool:
         """
         This method implements a comparison between self and another

ConfigSpace/forbidden.pyx

@@ -31,7 +31,7 @@ import numpy as np
 import io
 from ConfigSpace.hyperparameters import Hyperparameter
 from ConfigSpace.hyperparameters.hyperparameter cimport Hyperparameter
-from typing import Dict, Any, Union
+from typing import Dict, Any, Union, List
 
 from ConfigSpace.forbidden cimport AbstractForbiddenComponent
 
@@ -71,6 +71,9 @@ cdef class AbstractForbiddenComponent(object):
         return (self.value == other.value and
                 self.hyperparameter.name == other.hyperparameter.name)
 
+    def get_referenced_hyperparameters(self) -> List[Hyperparameter]:
+        pass
+
     def __hash__(self) -> int:
         """Override the default hash behavior (that returns the id or the object)"""
         return hash(tuple(sorted(self.__dict__.items())))
@@ -103,6 +106,9 @@ cdef class AbstractForbiddenClause(AbstractForbiddenComponent):
         self.hyperparameter = hyperparameter
         self.vector_id = -1
 
+    def get_referenced_hyperparameters(self) -> List[Hyperparameter]:
+        return [self.hyperparameter]
+
     cpdef get_descendant_literal_clauses(self):
         return (self, )
 
@@ -315,6 +321,9 @@ cdef class AbstractForbiddenConjunction(AbstractForbiddenComponent):
         self.n_components = len(self.components)
         self.dlcs = self.get_descendant_literal_clauses()
 
+    def get_referenced_hyperparameters(self) -> List[Hyperparameter]:
+        return sum([forb.get_referenced_hyperparameters() for forb in self.components], [])
+
     def __repr__(self):
         pass
 
@@ -497,6 +506,9 @@ cdef class ForbiddenRelation(AbstractForbiddenComponent):
         self.right = right
         self.vector_ids = (-1, -1)
 
+    def get_referenced_hyperparameters(self) -> List[Hyperparameter]:
+        return [self.left, self.right]
+
     def __eq__(self, other: Any) -> bool:
         if not isinstance(other, self.__class__):
             return False

ConfigSpace/util.py

@@ -708,3 +708,68 @@ def get_cartesian_product(value_sets: list[tuple], hp_names: list[str]) -> list[
         unchecked_grid_pts.popleft()
 
     return checked_grid_pts
+
+
+def remove_hyperparameter(name: str, configuration_space: ConfigurationSpace) -> ConfigurationSpace:
+    """
+    Returns a new configuration space with the hyperparameter removed.
+
+    Parameters
+    ----------
+    name: str
+        Name of the hyperparameter to remove
+
+    configuration_space: :class:`~ConfigSpace.configuration_space.ConfigurationSpace`
+        Configuration space from which to remove the hyperparameter.
+
+    Returns
+    -------
+    :class:`~ConfigSpace.configuration_space.Configuration`
+        A new configuration space without the hyperparameter
+    """
+    if name not in configuration_space._hyperparameters:
+        raise ValueError(f"{name} not in {configuration_space}")
+
+    hp_to_remove = configuration_space.get_hyperparameter(name)
+    hps = [
+        copy(hp)  # type: ignore
+        for hp in configuration_space.get_hyperparameters()
+        if hp.name != name
+    ]
+
+    conditions = [
+        cond
+        for cond in configuration_space.get_conditions()
+        if hp_to_remove not in cond.get_referenced_hyperparameters()
+    ]
+    forbiddens = [
+        forbidden
+        for forbidden in configuration_space.get_forbiddens()
+        if hp_to_remove not in forbidden.get_referenced_hyperparameters()
+    ]
+
+    if isinstance(configuration_space.random, np.random.RandomState):
+        new_seed = configuration_space.random.randint(2**32 - 1)
+    else:
+        new_seed = copy(configuration_space.random)  # type: ignore
+
+    new_space = ConfigurationSpace(
+        seed=new_seed,
+        name=copy(configuration_space.name),  # type: ignore
+        meta=copy(configuration_space.meta),  # type: ignore
+    )
+    new_space.add_hyperparameters(hps)
+
+    new_conditions = ConfigurationSpace.substitute_hyperparameters_in_conditions(
+        conditions=conditions,
+        new_configspace=new_space,
+    )
+    new_forbiddens = ConfigurationSpace.substitute_hyperparameters_in_forbiddens(
+        forbiddens=forbiddens,
+        new_configspace=new_space,
+    )
+
+    new_space.add_conditions(new_conditions)
+    new_space.add_forbidden_clauses(new_forbiddens)
+
+    return new_space