Surface gp_GetRandomNumber and seed its random number generator

examples/full/demo_random_int.py

@@ -0,0 +1,16 @@
+"""Script to demo the random integer generator used by the random graph generators.
+"""
+
+#!/usr/bin/env python
+
+from planarity import (
+    gp_GetRandomNumber,
+)
+
+if __name__ == "__main__":
+
+    print("Some pseudo-random numbers between 1 and 10:")
+    print(gp_GetRandomNumber(1, 10))
+    print(gp_GetRandomNumber(1, 10))
+    print(gp_GetRandomNumber(1, 10))
+    print(gp_GetRandomNumber(1, 10))

planarity/__init__.py

@@ -12,6 +12,7 @@
 from .full.graphLib import (
     gp_GetQuietMode,
     gp_SetQuietMode,
+    gp_GetRandomNumber,
 )
 
 # Surfaced from planarity/c/graphLib/graphLib.h
@@ -107,6 +108,14 @@
 from .full.graph import Graph
 from .full.g6IterationUtils import G6ReadIterator, G6WriteIterator
 
+# Seed the random number generator in the C library so that the
+# random number and random graph generators will produce different
+# outputs on each run of a script.
+from .full.graphLib import (
+    seed_rng,
+)
+seed_rng()
+
 # NOTE: In the future, we could automatically generate the version number by
 # configuring setuptools-scm, but presently this seems simpler.
 __version__ = "1.0.1"

planarity/full/cgraphLib.pxd

@@ -11,6 +11,8 @@ cdef extern from "../c/graphLib/lowLevelUtils/apiutils.h":
     int gp_GetQuietMode()
     void gp_SetQuietMode(int newQuietMode)
 
+    int gp_GetRandomNumber(int NMin, int NMax)
+
 
 cdef extern from "../c/graphLib/graphLib.h":
     const char *gp_GetProjectVersionFull()

planarity/full/graphLib.pyx

@@ -12,6 +12,7 @@ of the caller to make sure these functions are being called legitimately.
 from planarity.full cimport cgraphLib
 from planarity.full.cgraphLib cimport graphP, G6ReadIteratorP, G6WriteIteratorP
 
+from libc.stdlib cimport srand
 
 # Surfaced from planarityc/graphLib/lowLevelUtils/apiutils.h
 QUIETMODE_NONE = cgraphLib.QUIETMODE_NONE
@@ -144,6 +145,31 @@ def gp_SetQuietMode(int newQuietMode) -> None:
     cgraphLib.gp_SetQuietMode(newQuietMode)
 
 
+def gp_GetRandomNumber(int NMin, int NMax) -> int:
+    """Generates a pseudo-random integer number in the range of the parameters.
+
+    Like ``random.randint()`` except this method calls the same C-layer
+    ``gp_GetRandomNumber()`` method that is called by the random graph
+    generator methods such as ``gp_CreateRandomGraph()``.
+
+    Args:
+        NMin: The lower bound
+        NMax: The upper bound
+
+    Returns:
+        A pseudo-random integer in the closed range [NMin, NMax]
+    """
+    return cgraphLib.gp_GetRandomNumber(NMin, NMax)
+
+def seed_rng() -> None:
+    # Called by __init__.py to seed the pseudo-random number generator
+    # used by gp_GetRandomNumber() and the random graph generator methods.
+    # We seed with a random int generated by Python because Python seeds
+    # its random number generator with a true source of entropy when 
+    # available and only falls back to system time otherwise.
+    import random
+    srand(random.randint(0, 4294967295))
+
 def gp_GetProjectVersionFull() -> str:
     """Returns the Edge Addition Planarity Suite's project release version.