Scarliles/splitter injection

sklearn/tree/_splitter.pxd

@@ -6,19 +6,60 @@
 #          Jacob Schreiber <[email protected]>
 #          Adam Li <[email protected]>
 #          Jong Shin <[email protected]>
+#          Samuel Carliles <[email protected]>
 #
 # License: BSD 3 clause
 
 # See _splitter.pyx for details.
 cimport numpy as cnp
 
 from libcpp.vector cimport vector
+from libc.stdlib cimport malloc
 
 from ..utils._typedefs cimport float32_t, float64_t, intp_t, int32_t
 from ._utils cimport UINT32_t
 from ._criterion cimport BaseCriterion, Criterion
 
 
+# NICE IDEAS THAT DON'T APPEAR POSSIBLE
+# - accessing elements of a memory view of cython extension types in a nogil block/function
+# - storing cython extension types in cpp vectors
+#
+# despite the fact that we can access scalar extension type properties in such a context,
+# as for instance node_split_best does with Criterion and Partition,
+# and we can access the elements of a memory view of primitive types in such a context
+#
+# SO WHERE DOES THAT LEAVE US
+# - we can transform these into cpp vectors of structs
+#   and with some minor casting irritations everything else works ok
+ctypedef void* SplitConditionParameters
+ctypedef bint (*SplitConditionFunction)(
+    Splitter splitter,
+    SplitRecord* current_split,
+    intp_t n_missing,
+    bint missing_go_to_left,
+    float64_t lower_bound,
+    float64_t upper_bound,
+    SplitConditionParameters split_condition_parameters
+) noexcept nogil
+
+cdef struct SplitConditionTuple:
+    SplitConditionFunction f
+    SplitConditionParameters p
+
+cdef class SplitCondition:
+    cdef SplitConditionTuple t
+
+cdef class MinSamplesLeafCondition(SplitCondition):
+    pass
+
+cdef class MinWeightLeafCondition(SplitCondition):
+    pass
+
+cdef class MonotonicConstraintCondition(SplitCondition):
+    pass
+
+
 cdef struct SplitRecord:
     # Data to track sample split
     intp_t feature         # Which feature to split on.
@@ -112,6 +153,12 @@ cdef class Splitter(BaseSplitter):
     cdef const cnp.int8_t[:] monotonic_cst
     cdef bint with_monotonic_cst
 
+    cdef list _presplit_conditions
+    cdef list _postsplit_conditions
+
+    cdef vector[SplitConditionTuple*] presplit_conditions
+    cdef vector[SplitConditionTuple*] postsplit_conditions
+
     cdef int init(
         self,
         object X,