From 24298edf21b85ccc17e7a070f982ab6b5946f282 Mon Sep 17 00:00:00 2001
From: James Lamb <jaylamb20@gmail.com>
Date: Fri, 11 Dec 2020 05:51:01 +0000
Subject: [PATCH] clarify warning about small target values with MAPE (#3615)

---
 src/objective/regression_objective.hpp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/objective/regression_objective.hpp b/src/objective/regression_objective.hpp
index d7660a754991..bd25ec4e5029 100644
--- a/src/objective/regression_objective.hpp
+++ b/src/objective/regression_objective.hpp
@@ -587,7 +587,9 @@ class RegressionMAPELOSS : public RegressionL1loss {
     RegressionL2loss::Init(metadata, num_data);
     for (data_size_t i = 0; i < num_data_; ++i) {
       if (std::fabs(label_[i]) < 1) {
-        Log::Warning("Met 'abs(label) < 1', will convert them to '1' in MAPE objective and metric");
+        Log::Warning(
+          "Some label values are < 1 in absolute value. MAPE is unstable with such values, "
+          "so LightGBM rounds them to 1.0 when calculating MAPE.");
         break;
       }
     }