feat: use NumPy's RNG instead of igraph's own

Author: ntamas

src/codegen/internal_lib.py.in

@@ -40,6 +40,8 @@ from .types import (
     igraph_maxflow_stats_t,
     igraph_isocompat_t,
     igraph_plfit_result_t,
+    igraph_rng_t,
+    igraph_rng_type_t,
 )
 
 
@@ -356,6 +358,23 @@ igraph_es_destroy = _lib.igraph_es_destroy
 igraph_es_destroy.restype = None
 igraph_es_destroy.argtypes = [c_void_p]
 
+# Random number generators
+
+igraph_rng_init = _lib.igraph_rng_init
+igraph_rng_init.restype = handle_igraph_error_t
+igraph_rng_init.argtypes = [POINTER(igraph_rng_t), POINTER(igraph_rng_type_t)]
+
+igraph_rng_destroy = _lib.igraph_rng_destroy
+igraph_rng_destroy.restype = None
+igraph_rng_destroy.argtypes = [c_void_p]
+
+igraph_rng_default = _lib.igraph_rng_default
+igraph_rng_default.restype = POINTER(igraph_rng_t)
+
+igraph_rng_set_default = _lib.igraph_rng_set_default
+igraph_rng_set_default.restype = POINTER(igraph_rng_t)
+igraph_rng_set_default.argtypes = [POINTER(igraph_rng_t)]
+
 # Graph type
 
 igraph_destroy = _lib.igraph_destroy

src/igraph_ctypes/__init__.py

@@ -1,5 +1,8 @@
 from .version import __version__
 
 from .graph import Graph
+from ._internal.setup import setup_igraph_library
 
 __all__ = ("Graph", "__version__")
+
+setup_igraph_library()

src/igraph_ctypes/_internal/lib.py

@@ -40,6 +40,8 @@
     igraph_maxflow_stats_t,
     igraph_isocompat_t,
     igraph_plfit_result_t,
+    igraph_rng_t,
+    igraph_rng_type_t,
 )
 
 
@@ -356,6 +358,23 @@ def _load_igraph_c_library():
 igraph_es_destroy.restype = None
 igraph_es_destroy.argtypes = [c_void_p]
 
+# Random number generators
+
+igraph_rng_init = _lib.igraph_rng_init
+igraph_rng_init.restype = handle_igraph_error_t
+igraph_rng_init.argtypes = [POINTER(igraph_rng_t), POINTER(igraph_rng_type_t)]
+
+igraph_rng_destroy = _lib.igraph_rng_destroy
+igraph_rng_destroy.restype = None
+igraph_rng_destroy.argtypes = [c_void_p]
+
+igraph_rng_default = _lib.igraph_rng_default
+igraph_rng_default.restype = POINTER(igraph_rng_t)
+
+igraph_rng_set_default = _lib.igraph_rng_set_default
+igraph_rng_set_default.restype = POINTER(igraph_rng_t)
+igraph_rng_set_default.argtypes = [POINTER(igraph_rng_t)]
+
 # Graph type
 
 igraph_destroy = _lib.igraph_destroy

src/igraph_ctypes/_internal/rng.py

@@ -0,0 +1,78 @@
+from ctypes import pointer
+from functools import partial
+from numpy.random import Generator, PCG64
+from typing import Callable, Optional
+
+from .lib import igraph_rng_set_default
+from .types import igraph_rng_type_t, np_type_of_igraph_uint_t
+from .wrappers import _RNG
+
+__all__ = ("NumPyRNG",)
+
+
+class NumPyRNG:
+    """Implementation of an igraph RNG that wraps a NumPy RNG."""
+
+    _generator: Generator
+    """The wrapped NumPy random number generator."""
+
+    _rng: _RNG
+    _rng_type: igraph_rng_type_t
+
+    def __init__(self, generator: Generator):
+        # TODO(ntamas): currently we assume that Generator.bit_generator is
+        # PCG64
+        assert isinstance(generator.bit_generator, PCG64)
+
+        self._generator = generator
+        self._rng_type = igraph_rng_type_t(
+            name=b"NumPy RNG",
+            bits=64,
+            init=igraph_rng_type_t.TYPES["init"](self._rng_init),
+            destroy=igraph_rng_type_t.TYPES["destroy"](self._rng_destroy),
+            seed=igraph_rng_type_t.TYPES["seed"](self._rng_seed),
+            get=igraph_rng_type_t.TYPES["get"](self._rng_get),
+        )
+        self._rng = _RNG.create(pointer(self._rng_type))
+        self._rng.unwrap().is_seeded = True
+
+    def _rng_init(self, _state):
+        _state[0] = None
+        return 0  # IGRAPH_SUCCESS
+
+    def _rng_destroy(self, rng):
+        pass
+
+    def _rng_seed(self, _state, value):
+        # Ignore, we assume that NumPy RNGs are seeded externally
+        return 0
+
+    def _rng_get(self, _state):
+        """
+        return self._generator.bit_generator.ctypes.next_uint64(
+            self._generator.bit_generator.ctypes.state
+        )
+        """
+        return self._generator.integers(
+            0, 0xFFFFFFFFFFFFFFFF, dtype=np_type_of_igraph_uint_t, endpoint=True
+        )
+
+    def attach(self) -> Callable[[], None]:
+        """Attaches this RNG instance as igraph's default RNG.
+
+        Returns:
+            a callable that can be called with no arguments to restore the
+            RNG that was in effect before this RNG was attached.
+        """
+        global _igraph_default_rng
+
+        old = igraph_rng_set_default(self._rng)
+        _igraph_default_rng = self
+
+        return partial(igraph_rng_set_default, old)
+
+
+_igraph_default_rng: Optional[NumPyRNG] = None
+"""We need to keep a reference to NumPyRNG to keep the underlying low-level
+C objects alive, so we use an internal object in this module for that.
+"""

src/igraph_ctypes/_internal/setup.py

@@ -0,0 +1,13 @@
+from .rng import NumPyRNG
+
+__all__ = ("setup_igraph_library",)
+
+
+def setup_igraph_library() -> None:
+    """Initializes the random number generator of the igraph library.
+
+    This function is called when the ``igraph_ctypes`` module is imported by the user.
+    """
+    from numpy.random import default_rng
+
+    NumPyRNG(default_rng()).attach()

src/igraph_ctypes/_internal/types.py

@@ -10,7 +10,10 @@
     c_int64,
     c_long,
     c_ulong,
+    c_uint8,
+    c_uint64,
     c_void_p,
+    py_object,
     POINTER,
     Structure,
     Union as CUnion,
@@ -38,11 +41,15 @@ def vector_fields(base_type):
     c_int64  # TODO(ntamas): this depends on whether igraph is 32-bit or 64-bit
 )
 igraph_real_t = c_double
+igraph_uint_t = (
+    c_uint64  # TODO(ntamas): this depends on whether igraph is 32-bit or 64-bit
+)
 
 # TODO(ntamas): these depend on whether igraph is 32-bit or 64-bit
 np_type_of_igraph_bool_t = np.bool_
 np_type_of_igraph_integer_t = np.int64
 np_type_of_igraph_real_t = np.float64
+np_type_of_igraph_uint_t = np.uint64
 
 
 class FILE(Structure):
@@ -347,6 +354,60 @@ class igraph_plfit_result_t(Structure):
     ]
 
 
+igraph_rng_state_t = py_object
+
+
+class igraph_rng_type_t(Structure):
+    """ctypes representation of an ``igraph_rng_type_t`` object"""
+
+    TYPES = {
+        "init": CFUNCTYPE(igraph_error_t, POINTER(igraph_rng_state_t)),
+        "destroy": CFUNCTYPE(None, igraph_rng_state_t),
+        "seed": CFUNCTYPE(igraph_error_t, igraph_rng_state_t, igraph_uint_t),
+        "get": CFUNCTYPE(igraph_uint_t, igraph_rng_state_t),
+    }
+
+    _fields_ = [
+        ("name", c_char_p),
+        ("bits", c_uint8),
+        ("init", TYPES["init"]),
+        ("destroy", TYPES["destroy"]),
+        ("seed", TYPES["seed"]),
+        ("get", TYPES["get"]),
+        (
+            "get_int",
+            CFUNCTYPE(
+                igraph_integer_t, igraph_rng_state_t, igraph_integer_t, igraph_integer_t
+            ),
+        ),
+        ("get_real", CFUNCTYPE(igraph_real_t, igraph_rng_state_t)),
+        ("get_norm", CFUNCTYPE(igraph_real_t, igraph_rng_state_t)),
+        ("get_geom", CFUNCTYPE(igraph_real_t, igraph_rng_state_t, igraph_real_t)),
+        (
+            "get_binom",
+            CFUNCTYPE(
+                igraph_real_t, igraph_rng_state_t, igraph_integer_t, igraph_real_t
+            ),
+        ),
+        ("get_exp", CFUNCTYPE(igraph_real_t, igraph_rng_state_t, igraph_real_t)),
+        (
+            "get_gamma",
+            CFUNCTYPE(igraph_real_t, igraph_rng_state_t, igraph_real_t, igraph_real_t),
+        ),
+        ("get_pois", CFUNCTYPE(igraph_real_t, igraph_rng_state_t, igraph_real_t)),
+    ]
+
+
+class igraph_rng_t(Structure):
+    """ctypes representation of an ``igraph_rng_t`` object"""
+
+    _fields_ = [
+        ("type", POINTER(igraph_rng_type_t)),
+        ("state", igraph_rng_state_t),
+        ("is_seeded", igraph_bool_t),
+    ]
+
+
 igraph_isocompat_t = CFUNCTYPE(
     igraph_bool_t,
     POINTER(igraph_t),

src/igraph_ctypes/_internal/wrappers.py

@@ -8,6 +8,8 @@
     igraph_matrix_init,
     igraph_matrix_int_destroy,
     igraph_matrix_int_init,
+    igraph_rng_init,
+    igraph_rng_destroy,
     igraph_vector_destroy,
     igraph_vector_init,
     igraph_vector_bool_destroy,
@@ -25,6 +27,7 @@
     igraph_es_t,
     igraph_matrix_t,
     igraph_matrix_int_t,
+    igraph_rng_t,
     igraph_vector_t,
     igraph_vector_bool_t,
     igraph_vector_int_t,
@@ -38,6 +41,7 @@
     "_Graph",
     "_Matrix",
     "_MatrixInt",
+    "_RNG",
     "_Vector",
     "_VectorBool",
     "_VectorInt",
@@ -236,3 +240,14 @@ class _Graph(create_boxed("_Graph", igraph_t, destructor=igraph_destroy)):
     igraph_es_t,
     destructor=igraph_es_destroy,
 )
+
+
+class _RNG(
+    create_boxed(
+        "_RNG",
+        igraph_rng_t,
+        constructor=igraph_rng_init,
+        destructor=igraph_rng_destroy,
+    )
+):
+    pass