From ca118555214a176728b9aab87849391344306d6d Mon Sep 17 00:00:00 2001
From: Paul Oliver <contact@pauloliver.dev>
Date: Thu, 29 Feb 2024 02:29:13 +0100
Subject: Initial commit.

---
 src/evolver.c | 132 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 132 insertions(+)
 create mode 100644 src/evolver.c

(limited to 'src/evolver.c')

diff --git a/src/evolver.c b/src/evolver.c
new file mode 100644
index 0000000..e3b6ef7
--- /dev/null
+++ b/src/evolver.c
@@ -0,0 +1,132 @@
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include "types.h"
+#include "getter.h"
+#include "instset.h"
+#include "memory.h"
+#include "evolver.h"
+
+static boolean g_is_init;
+static uint32 g_last_changed_address;
+static uint32 g_calls_on_last_cycle;
+static uint32 g_state[4];
+
+void _sal_evo_init(void)
+{
+	/* Start up the evolver module. We simply set the 128 bits into a random
+	state by calling 'rand()'.
+	*/
+	assert(!g_is_init);
+	srand((uint32)time(NULL));
+	g_state[0] = rand();
+	g_state[1] = rand();
+	g_state[2] = rand();
+	g_state[3] = rand();
+	g_is_init = TRUE;
+}
+
+void _sal_evo_quit(void)
+{
+	/* Quit the evolver module. Reset everything back to zero.
+	*/
+	assert(g_is_init);
+	g_is_init = FALSE;
+	g_last_changed_address = 0;
+	g_calls_on_last_cycle = 0;
+	memset(g_state, 0, sizeof(uint32) * 4);
+}
+
+void _sal_evo_load_from(FILE *file)
+{
+	/* Load evolver state from a binary file.
+	*/
+	assert(!g_is_init);
+	assert(file);
+	fread(&g_is_init, sizeof(boolean), 1, file);
+	fread(&g_last_changed_address, sizeof(uint32), 1, file);
+	fread(&g_calls_on_last_cycle, sizeof(uint32), 1, file);
+	fread(&g_state, sizeof(uint32), 4, file);
+}
+
+void _sal_evo_save_into(FILE *file)
+{
+	/* Save evolver state into a binary file.
+	*/
+	assert(g_is_init);
+	assert(file);
+	fwrite(&g_is_init, sizeof(boolean), 1, file);
+	fwrite(&g_last_changed_address, sizeof(uint32), 1, file);
+	fwrite(&g_calls_on_last_cycle, sizeof(uint32), 1, file);
+	fwrite(&g_state, sizeof(uint32), 4, file);
+}
+
+/* Getter methods for the evolver module.
+*/
+UINT32_GETTER(evo, last_changed_address)
+UINT32_GETTER(evo, calls_on_last_cycle)
+
+uint32 sal_evo_get_state(uint8 state_index)
+{
+	/* Get part of the evolver's internal state (32 bits of 128 total bits) as
+	an unsigned int.
+	*/
+	assert(g_is_init);
+	assert(state_index < 4);
+	return g_state[state_index];
+}
+
+static uint32 generate_random_number(void)
+{
+	/* Generate a single 32 bit random number. This module makes use of the
+	XOR-Shift pseudo-rng. We use XOR-Shift because it's extremely lightweight
+	and fast, while providing quite good results. Find more info about it here:
+	>>> https://en.wikipedia.org/wiki/Xorshift
+	*/
+	uint32 tmp1;
+	uint32 tmp2;
+	assert(g_is_init);
+	tmp2 = g_state[3];
+	tmp2 ^= tmp2 << 11;
+	tmp2 ^= tmp2 >> 8;
+	g_state[3] = g_state[2];
+	g_state[2] = g_state[1];
+	g_state[1] = tmp1 = g_state[0];
+	tmp2 ^= tmp1;
+	tmp2 ^= tmp1 >> 19;
+	g_state[0] = tmp2;
+	g_calls_on_last_cycle++;
+	return tmp2;
+}
+
+void _sal_evo_randomize_at(uint32 address)
+{
+	/* Place a random instruction into a given address.
+	*/
+	uint8 inst;
+	assert(g_is_init);
+	assert(sal_mem_is_address_valid(address));
+	inst = generate_random_number() % INST_COUNT;
+	g_last_changed_address = address;
+	sal_mem_set_inst(address, inst);
+}
+
+void _sal_evo_cycle(void)
+{
+	/* During each simulation cycle, a random 32 bit integer is generated. If
+	this integer represents a 'valid' address in memory
+	(i.e. new_rand < memory_size), this address becomes hit by a cosmic ray
+	(randomized). This simple mutation scheme is enough to drive evolution in
+	Salis.
+	*/
+	uint32 address;
+	assert(g_is_init);
+	g_calls_on_last_cycle = 0;
+	address = generate_random_number();
+
+	if (sal_mem_is_address_valid(address)) {
+		_sal_evo_randomize_at(address);
+	}
+}
-- 
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