From bd8116eaf02c9fb7673cadd097b0daff27fb6fa4 Mon Sep 17 00:00:00 2001
From: Nicklas Larsson <n_larsson@yahoo.com>
Date: Mon, 25 Mar 2024 17:22:48 +0100
Subject: [PATCH] r.univar: init max value with smallest possible value (#3512)

Manual backport of 68ca15d0696a9583f730f8b13ae9d6812a2fde71
---
 raster/r.univar/r.univar_main.c            |  2 +-
 raster/r.univar/testsuite/test_r_univar.py | 44 ++++++++++++++++++++++
 2 files changed, 45 insertions(+), 1 deletion(-)

diff --git a/raster/r.univar/r.univar_main.c b/raster/r.univar/r.univar_main.c
index 8cb26b5d9ca..b8f73c7e5b4 100644
--- a/raster/r.univar/r.univar_main.c
+++ b/raster/r.univar/r.univar_main.c
@@ -362,7 +362,7 @@ static void process_raster(univar_stat *stats, int *fd, int *fdz,
         double *max = G_malloc(n_alloc * sizeof(double));
 
         for (i = 0; i < n_alloc; i++) {
-            max[i] = DBL_MIN;
+            max[i] = -DBL_MAX;
             min[i] = DBL_MAX;
         }
 
diff --git a/raster/r.univar/testsuite/test_r_univar.py b/raster/r.univar/testsuite/test_r_univar.py
index 8bcbb6da238..871e76c8885 100644
--- a/raster/r.univar/testsuite/test_r_univar.py
+++ b/raster/r.univar/testsuite/test_r_univar.py
@@ -19,6 +19,7 @@ def tearDownClass(cls):
     def tearDown(self):
         self.runModule("g.remove", flags="f", type="raster", name="map_a")
         self.runModule("g.remove", flags="f", type="raster", name="map_b")
+        self.runModule("g.remove", flags="f", type="raster", name="map_negative")
         self.runModule("g.remove", flags="f", type="raster", name="zone_map")
         self.runModule("g.remove", flags="f", type="raster", name="zone_map_with_gap")
 
@@ -39,6 +40,11 @@ def setUp(self):
             expression="zone_map_with_gap = if(row()> 20, 2, 9)",
             overwrite=True,
         )
+        self.runModule(
+            "r.mapcalc",
+            expression="map_negative = -double(10) - row() - col()",
+            overwrite=True,
+        )
 
     def test_1(self):
         # Output of r.univar
@@ -223,6 +229,44 @@ def test_multiple_3(self):
             sep="=",
         )
 
+    def test_negative(self):
+        """
+        check map with only negative values
+        :return:
+        """
+
+        univar_string = """n=8100
+        null_cells=0
+        cells=8100
+        min=-190
+        max=-12
+        range=178
+        mean=-101
+        mean_of_abs=101
+        stddev=36.7400780256838
+        variance=1349.83333333333
+        coeff_var=-36.3763148769146
+        sum=-818100"""
+
+        self.runModule("g.region", res=10)
+        self.assertModuleKeyValue(
+            module="r.univar",
+            map="map_negative",
+            flags="rg",
+            reference=univar_string,
+            precision=6,
+            sep="=",
+        )
+        self.assertModuleKeyValue(
+            module="r.univar",
+            map="map_negative",
+            flags="rg",
+            nprocs=4,
+            reference=univar_string,
+            precision=6,
+            sep="=",
+        )
+
     def test_1_zone(self):
         """
         one map and zone