add custom hypergraph generator

Author: yifanfeng97

dhg/random/hypergraphs/hypergraph.py

@@ -74,18 +74,21 @@ def hypergraph_Gnm(num_v: int, num_e: int, method:str="low_order_first", prob_k_
     Args:
         ``num_v`` (``int``): The Number of vertices.
         ``num_e`` (``int``): The Number of hyperedges.
-        ``method`` (``str``): The method to generate hyperedges must be one of ``"uniform"``, ``"low_order_first"``, ``"high_order_first"``. Defaults to ``"uniform"``.
+        ``method`` (``str``): The method to generate hyperedges must be one of ``"uniform"``, ``"low_order_first"``, ``"high_order_first"``, ``"custom"``. Defaults to ``"uniform"``.
     Examples:
         >>> import dhg.random as random
         >>> hg = random.hypergraph_Gnm(5, 4)
         >>> hg.e
         ([(0, 1, 3, 4), (0, 2, 3, 4), (0, 2, 3), (0, 2, 4)], [1.0, 1.0, 1.0, 1.0])
+        >>> hg = dhg.random.hypergraph_Gnm(5, 4, 'custom', [0, 0, 0.8, 0.2])
+        >>> hg.e
+        ([(1, 2, 3, 4), (0, 2, 3, 4), (0, 1, 2, 3), (0, 1, 2, 3, 4)], [1.0, 1.0, 1.0, 1.0])
     """
     # similar to nauty in sagemath, https://doc.sagemath.org/html/en/reference/graphs/sage/graphs/hypergraph_generators.html
 
     assert num_v > 1, "num_v must be greater than 1"
     assert num_e > 0, "num_e must be greater than 0"
-    assert method in ("uniform", "low_order_first", "high_order_first"), "method must be one of 'uniform', 'low_order_first', 'high_order_first'"
+    assert method in ("uniform", "low_order_first", "high_order_first", "custom"), "method must be one of 'uniform', 'low_order_first', 'high_order_first', 'custom'"
     deg_e_list = list(range(2, num_v + 1))
     if method == "uniform":
         prob_k_list = [C(num_v, k) / (2 ** num_v - 1) for k in deg_e_list]
@@ -97,6 +100,11 @@ def hypergraph_Gnm(num_v: int, num_e: int, method:str="low_order_first", prob_k_
         prob_k_list = [3 ** (-k) for k in range(len(deg_e_list))].reverse()
         sum_of_prob_k_list = sum(prob_k_list)
         prob_k_list = [prob_k / sum_of_prob_k_list for prob_k in prob_k_list]
+    elif method == "custom":
+        assert prob_k_list is not None, "prob_k_list must be provided when method is custom"
+        assert len(prob_k_list) == num_v - 1, "prob_k_list must have length `num_v - 1'"
+        sum_of_prob_k_list = sum(prob_k_list)
+        prob_k_list = [prob_k / sum_of_prob_k_list for prob_k in prob_k_list]
     else:
         raise ValueError(f"Unknown method: {method}")