Add XorShift, SplitMix64, WyRandom, PCG, and XoroShiro generators

Co-authored-by: 8e8m <248551607+8e8m@users.noreply.github.com>

1 files changed, 94 insertions, 0 deletions

diff --git a/source/pcg_random.c b/source/pcg_random.c
new file mode 100644
index 0000000..4d01b49
--- /dev/null
+++ b/source/pcg_random.c
@@ -0,0 +1,94 @@
+/* MIT License - Copyright (c) 2025 wallstop
+ * Original C# implementation from: https://github.com/wallstop/unity-helpers
+ * Converted to C for librandom project
+ *
+ * @BAKE cc -O2 -Wall -Wextra -std=c99 -o pcg_random pcg_random.c -lm @STOP
+ */
+
+#include "pcg_random.h"
+
+static inline uint64_t normalize_increment(uint64_t increment) {
+    return (increment & 1ULL) == 0 ? increment | 1ULL : increment;
+}
+
+void pcg_init(pcg_random_t *rng, uint64_t seed) {
+    rng->increment = normalize_increment(6554638469ULL);
+    rng->state = seed;
+    /* Warm up the state */
+    pcg_next_uint(rng);
+    rng->increment = normalize_increment((uint64_t)pcg_next_uint(rng) | ((uint64_t)pcg_next_uint(rng) << 32));
+}
+
+void pcg_init_full(pcg_random_t *rng, uint64_t state, uint64_t increment) {
+    rng->state = state;
+    rng->increment = normalize_increment(increment);
+}
+
+uint32_t pcg_next_uint(pcg_random_t *rng) {
+    uint64_t old_state = rng->state;
+    rng->state = old_state * 6364136223846793005ULL + rng->increment;
+    uint32_t xor_shifted = (uint32_t)(((old_state >> 18) ^ old_state) >> 27);
+    int rot = (int)(old_state >> 59);
+    return (xor_shifted >> rot) | (xor_shifted << ((-rot) & 31));
+}
+
+uint64_t pcg_next_ulong(pcg_random_t *rng) {
+    uint64_t high = (uint64_t)pcg_next_uint(rng) << 32;
+    uint64_t low = (uint64_t)pcg_next_uint(rng);
+    return high | low;
+}
+
+float pcg_next_float(pcg_random_t *rng) {
+    uint32_t value = pcg_next_uint(rng);
+    return (value >> 8) * 0x1.0p-24f;
+}
+
+double pcg_next_double(pcg_random_t *rng) {
+    uint64_t value = pcg_next_ulong(rng);
+    return (value >> 11) * 0x1.0p-53;
+}
+
+#ifdef PCG_TEST_MAIN
+#include <stdio.h>
+#include <time.h>
+
+int main(void) {
+    pcg_random_t rng;
+    
+    printf("PCG Random C Implementation Test\n");
+    printf("=================================\n\n");
+    
+    pcg_init(&rng, 42);
+    
+    printf("Testing with seed 42:\n");
+    printf("First 10 uint32_t values:\n");
+    for (int i = 0; i < 10; i++) {
+        printf("  %u\n", pcg_next_uint(&rng));
+    }
+    
+    printf("\nFirst 10 uint64_t values:\n");
+    pcg_init(&rng, 42);
+    for (int i = 0; i < 10; i++) {
+        printf("  %llu\n", (unsigned long long)pcg_next_ulong(&rng));
+    }
+    
+    printf("\nFirst 10 float values:\n");
+    pcg_init(&rng, 42);
+    for (int i = 0; i < 10; i++) {
+        printf("  %.6f\n", pcg_next_float(&rng));
+    }
+    
+    printf("\nPerformance test: generating 10 million uint32_t values...\n");
+    pcg_init(&rng, (uint64_t)time(NULL));
+    clock_t start = clock();
+    uint64_t sum = 0;
+    for (int i = 0; i < 10000000; i++) {
+        sum += pcg_next_uint(&rng);
+    }
+    clock_t end = clock();
+    double elapsed = (double)(end - start) / CLOCKS_PER_SEC;
+    printf("Time: %.3f seconds (sum: %llu to prevent optimization)\n", elapsed, (unsigned long long)sum);
+    
+    return 0;
+}
+#endif