[example][1ptracer] Use library-independent portable random distribution

examples/1ptracer/spatialparams_1p.hh

@@ -32,7 +32,13 @@
 // In this example, we use a randomly generated and element-wise distributed
 // permeability field. For this, we use the random number generation facilities
 // provided by the C++ standard library.
+// Dumux additionally implements some simpler but
+// standard-library-implementation-independent random distributions
+// that are accurate enough for our purposes
+// but allow to generate reproducible and portable random fields (when using a constant seed)
+// for testing purposes.
 #include <random>
+#include <dumux/common/random.hh>
 
 // We include the spatial parameters class for single-phase models discretized
 // by finite volume schemes, from which the spatial parameters defined for this
@@ -88,15 +94,19 @@ public:
 
         // Furthermore, the position of the lens, which is defined by the position of the lower left and the upper right corners, are obtained from the input file.
         lensLowerLeft_ = getParam<GlobalPosition>("SpatialParams.LensLowerLeft");
-        lensUpperRight_ =getParam<GlobalPosition>("SpatialParams.LensUpperRight");
+        lensUpperRight_ = getParam<GlobalPosition>("SpatialParams.LensUpperRight");
 
         // We generate random fields for the permeability using lognormal distributions,
         // with `permeability_` as mean value and 10 % of it as standard deviation.
         // A separate distribution is used for the lens using `permeabilityLens_`.
         // A permeability value is created for each element of the grid and is stored in the vector `K_`.
+        // For a "truly" random field (different every time we execute) the seed `0` for the
+        // Mersenne-Twister pseudo-random-number generator should be replaced
+        // by `std::random_device{}()`. For unbiased high-quality distributions (usually not needed)
+        // replace `Dumux::SimpleLogNormalDistribution` by `std::lognormal_distribution`.
         std::mt19937 rand(0);
-        std::lognormal_distribution<Scalar> K(std::log(permeability_), std::log(permeability_)*0.1);
-        std::lognormal_distribution<Scalar> KLens(std::log(permeabilityLens_), std::log(permeabilityLens_)*0.1);
+        Dumux::SimpleLogNormalDistribution<Scalar> K(std::log(permeability_), std::log(permeability_)*0.1);
+        Dumux::SimpleLogNormalDistribution<Scalar> KLens(std::log(permeabilityLens_), std::log(permeabilityLens_)*0.1);
 
         // loop over all elements and compute a permeability value
         for (const auto& element : elements(gridGeometry->gridView()))