rand: prefer our own generators

CMakeLists.txt

@@ -478,6 +478,7 @@ list (
     "${CMAKE_CURRENT_BINARY_DIR}/prefix/${PREFIX}/preprocessor.hpp"
     quaternion.cpp
     quaternion.hpp
+    rand/generic.hpp
     rand/lcg.cpp
     rand/lcg.hpp
     rand/mwc64x.cpp

rand/generic.hpp

@@ -0,0 +1,18 @@
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ *
+ * Copyright 2020, Danny Robson <danny@nerdcruft.net>
+ */
+
+#pragma once
+
+#include "xoshiro.hpp"
+
+
+///////////////////////////////////////////////////////////////////////////////
+namespace cruft::rand {
+    /// A generator with a good tradeoff between speed, size, and quality.
+    using general_generator = xoshiro256plusplus;
+}

random.hpp

@@ -9,6 +9,7 @@
 #pragma once
 
 #include "coord/traits.hpp"
+#include "rand/generic.hpp"
 
 #include <algorithm>
 #include <array>
@@ -54,7 +55,7 @@ namespace cruft::random {
     inline auto&
     generator (void)
     {
-        using generator_t = std::mt19937_64;
+        using generator_t = cruft::rand::general_generator;
         static thread_local auto gen = initialise<generator_t> ();
         return gen;
     }

test/geom/sample/edge.cpp

@@ -1,7 +1,8 @@
-#include "geom/sample/edge.hpp"
-#include "tap.hpp"
-#include "coord/iostream.hpp"
 #include "coord/comparator.hpp"
+#include "coord/iostream.hpp"
+#include "geom/sample/edge.hpp"
+#include "rand/generic.hpp"
+#include "tap.hpp"
 
 #include <map>
 
@@ -14,7 +15,7 @@ int main ()
     std::map<cruft::point2i, int, cruft::coord::ordering<>> counts;
 
     auto sampler = cruft::geom::sample::edge (AREA);
-    std::mt19937_64 gen;
+    cruft::rand::general_generator gen (42);
 
     cruft::TAP::logger tap;
 

test/list/sort.cpp

@@ -8,6 +8,7 @@
 
 #include "list/sort.hpp"
 #include "random.hpp"
+#include "rand/generic.hpp"
 #include "tap.hpp"
 #include "iterator/zip.hpp"
 
@@ -72,7 +73,7 @@ int main ()
         std::shuffle (
             std::begin (data),
             std::end   (data),
-            std::mt19937 {COUNT}
+            cruft::rand::general_generator {COUNT}
         );
 
         test_sort (tap, std::move (data), "sorting large unique and shuffled array");

tools/poisson.cpp

@@ -2,6 +2,7 @@
 #include "functor.hpp"
 #include "geom/aabb.hpp"
 #include "geom/sample/surface.hpp"
+#include "rand/generic.hpp"
 
 #include <cstdlib>
 #include <iostream>
@@ -24,10 +25,12 @@ main (int argc, char **argv)
 
     opts.scan (argc, argv);
 
+    auto gen = cruft::random::initialise<cruft::rand::general_generator> ();
+
     std::cout << "<svg height='" << area.h << "' width='" << area.h << "'>";
     namespace sample = cruft::geom::sample;
     for (auto const &p: sample::poisson (sample::surface {area},
-                                         std::default_random_engine (),
+                                         gen,
                                          cruft::functor::constant (distance),
                                          samples))
     {