From 204d1f1456c0a58c1b8f5ebe54a794766b757f62 Mon Sep 17 00:00:00 2001
From: Gael Guennebaud <g.gael@free.fr>
Date: Sat, 8 Dec 2018 00:13:37 +0100
Subject: [PATCH] Fix noise in sparse_basic_3 (numerical cancellation) (grafted
 from cd25b538abff7370100ef5613b8138919f89c7b0 )

---
 test/sparse_basic.cpp | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/test/sparse_basic.cpp b/test/sparse_basic.cpp
index f84b6e3f5..d0ef722b6 100644
--- a/test/sparse_basic.cpp
+++ b/test/sparse_basic.cpp
@@ -630,7 +630,8 @@ void big_sparse_triplet(Index rows, Index cols, double density) {
   {
     Index r = internal::random<Index>(0,rows-1);
     Index c = internal::random<Index>(0,cols-1);
-    Scalar v = internal::random<Scalar>();
+    // use positive values to prevent numerical cancellation errors in sum
+    Scalar v = numext::abs(internal::random<Scalar>());
     triplets.push_back(TripletType(r,c,v));
     sum += v;
   }