Add graph references

2026-06-28 13:49:01 +01:00
parent 0a9807e448
commit a11edf0c53
2578 changed files with 868045 additions and 0 deletions
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+/*
+ * PCG Random Number Generation for C.
+ *
+ * Copyright 2014-2019 Melissa O'Neill <oneill@pcg-random.org>,
+ *                     and the PCG Project contributors.
+ *
+ * SPDX-License-Identifier: (Apache-2.0 OR MIT)
+ *
+ * Licensed under the Apache License, Version 2.0 (provided in
+ * LICENSE-APACHE.txt and at http://www.apache.org/licenses/LICENSE-2.0)
+ * or under the MIT license (provided in LICENSE-MIT.txt and at
+ * http://opensource.org/licenses/MIT), at your option. This file may not
+ * be copied, modified, or distributed except according to those terms.
+ *
+ * Distributed on an "AS IS" BASIS, WITHOUT WARRANTY OF ANY KIND, either
+ * express or implied.  See your chosen license for details.
+ *
+ * For additional information about the PCG random number generation scheme,
+ * visit http://www.pcg-random.org/.
+ */
+
+/*
+ * This code is derived from the canonical C++ PCG implementation, which
+ * has many additional features and is preferable if you can use C++ in
+ * your project.
+ *
+ * Repetative C code is derived using C preprocessor metaprogramming
+ * techniques.
+ */
+
+#include "pcg_variants.h"
+
+/* Multi-step advance functions (jump-ahead, jump-back)
+ *
+ * The method used here is based on Brown, "Random Number Generation
+ * with Arbitrary Stride,", Transactions of the American Nuclear
+ * Society (Nov. 1994).  The algorithm is very similar to fast
+ * exponentiation.
+ *
+ * Even though delta is an unsigned integer, we can pass a
+ * signed integer to go backwards, it just goes "the long way round".
+ */
+
+uint64_t pcg_advance_lcg_64(uint64_t state, uint64_t delta, uint64_t cur_mult,
+                            uint64_t cur_plus)
+{
+    uint64_t acc_mult = 1u;
+    uint64_t acc_plus = 0u;
+    while (delta > 0) {
+        if (delta & 1) {
+            acc_mult *= cur_mult;
+            acc_plus = acc_plus * cur_mult + cur_plus;
+        }
+        cur_plus = (cur_mult + 1) * cur_plus;
+        cur_mult *= cur_mult;
+        delta /= 2;
+    }
+    return acc_mult * state + acc_plus;
+}