From e7b6b845ddc2e914efb1867d36472f44404f33ae Mon Sep 17 00:00:00 2001
From: webbrain-one <295484252+webbrain-one@users.noreply.github.com>
Date: Wed, 12 Aug 2026 13:02:26 +0300
Subject: [PATCH] Validate probability distribution sums to 1

Add a check during initialization to ensure the distribution sums to 1.
This prevents undefined behavior when the sampler is initialized with
an invalid probability distribution.

Closes #7
---
 vose_sampler/vose_sampler.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/vose_sampler/vose_sampler.py b/vose_sampler/vose_sampler.py
index 543814c..2be7d49 100644
--- a/vose_sampler/vose_sampler.py
+++ b/vose_sampler/vose_sampler.py
@@ -22,6 +22,8 @@ class VoseAlias(object):
 
     def __init__(self, dist, rng=None):
         """ (VoseAlias, dict[, RNG]) -> NoneType """
+        if sum(dist.values()) != 1:
+            raise ValueError("Probability distribution must sum to 1.")
         self.dist = dist
         self.rng = rng or random.Random()
         self.alias_initialisation()