clean the ambiguity with insertBack and add a insertBackByOuterInner function
diff --git a/test/sparse_basic.cpp b/test/sparse_basic.cpp
index 9de156d..43d9c62 100644
--- a/test/sparse_basic.cpp
+++ b/test/sparse_basic.cpp
@@ -323,12 +323,12 @@
         else if (x<0.5)
         {
           countFalseNonZero++;
-          m2.insertBack(j,i) = Scalar(0);
+          m2.insertBackByOuterInner(j,i) = Scalar(0);
         }
         else
         {
           countTrueNonZero++;
-          m2.insertBack(j,i) = refM2(i,j) = Scalar(1);
+          m2.insertBackByOuterInner(j,i) = refM2(i,j) = Scalar(1);
         }
       }
     }