From e64e281b6377e715642d35ae664761720358335d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ricardo=20Monta=C3=B1ana=20G=C3=B3mez?=
 <rmontanana@gmail.com>
Date: Wed, 14 May 2025 13:15:33 +0200
Subject: [PATCH] Return AUC 0.5 if nPos==0 || nNeg==0

---
 src/main/RocAuc.cpp | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/main/RocAuc.cpp b/src/main/RocAuc.cpp
index 03a1c31..c41d986 100644
--- a/src/main/RocAuc.cpp
+++ b/src/main/RocAuc.cpp
@@ -4,7 +4,7 @@
 #include <utility>
 #include "RocAuc.h"
 namespace platform {
-    
+
     double RocAuc::compute(const torch::Tensor& y_proba, const torch::Tensor& labels)
     {
         size_t nClasses = y_proba.size(1);
@@ -48,6 +48,7 @@ namespace platform {
         double tp = 0, fp = 0;
         double totalPos = std::count(y_test.begin(), y_test.end(), classIdx);
         double totalNeg = nSamples - totalPos;
+        if (totalPos == 0 || totalNeg == 0) return 0.5; // neutral AUC
 
         for (const auto& [score, label] : scoresAndLabels) {
             if (label == 1) {