add basic computations

2 files changed, 94 insertions, 0 deletions

diff --git a/src/mind/topology.js b/src/mind/topology.js
index 755fe4a..1cd52d3 100644
--- a/src/mind/topology.js
+++ b/src/mind/topology.js
@@ -8,6 +8,9 @@ const graph_proto = {
 	connect: function(source, sink, weight) {
 		return network_connect(this, source, sink, weight);
 	},
+	compute: function(inputs, state) {
+		return network_compute(this, inputs, state);
+	},
 };
 
 export function network(input_count, internal_count, output_count, weight_max = 4) {
@@ -58,3 +61,56 @@ function network_connect(n, source, sink, weight) {
 
 	return Object.freeze(nn);
 }
+
+
+function incident_edges(n, adj) {
+	const incident = adj
+		.map((edge, index) => edge < 0 ? index : null)
+		.filter(index => index !== null);
+
+	return incident;
+}
+
+
+function edge_ends(n, edge) {
+	const ends = n.adjacency
+		.map((adj, index) => adj[edge] !== 0 ? index : null)
+		.filter(index => index != null);
+	
+	ends.sort((a, b) => n.adjacency[a][edge] < n.adjacency[b][edge] ? -1 : 1);
+
+	return ends;
+}
+
+
+function get_value(n, index, input) {
+	if (is_input(n, index)) {
+		return input[index];
+	}
+	const adj = n.adjacency[index];
+	const incident = incident_edges(n, adj);	
+	const weight = incident.map(x => n.weight[x]);
+	const sources = incident
+		.map(x => edge_ends(n, x))
+		.map(x => x.length === 2 ? x[1] : x[0]);
+
+	const sum = sources
+		.reduce((acc, x, i) => acc + (weight[i] * get_value(n, x, input)), 0);
+	
+	return Math.tanh(sum);
+}
+
+
+function network_compute(n, input, state) {
+	const outputs = n.adjacency
+		.map((x, i) => is_output(n, i) ? i : null)
+		.filter(i => i !== null);
+
+	const output = Object.freeze(
+		outputs.map(x => get_value(n, x, input))
+	);
+
+	const newstate = Object.freeze([]);
+	
+	return Object.freeze([output, newstate]);
+}
diff --git a/src/mind/topology.test.js b/src/mind/topology.test.js
index 5aab350..e1c5f87 100644
--- a/src/mind/topology.test.js
+++ b/src/mind/topology.test.js
@@ -99,3 +99,41 @@ test('self-connections work correctly', () => {
 		weight: [ 2 ],
 	});
 });
+
+
+test('network computations', () => {
+	const n = network(1, 0, 1).connect(0, 1, 2.0);
+	const input = [ -0.5 ];
+	const state = [];
+	const result = n.compute(input, state);
+	expect(result).toEqual([
+		[ Math.tanh(-0.5 * 2.0) ],
+		[],
+	]);
+
+	expect(input).toEqual([ -0.5 ]);
+	expect(state).toEqual([]);
+
+	expect(() => result[0] = 'hi').toThrow();
+	expect(() => result[0].push('hi')).toThrow();
+	expect(() => result[1] = 'hi').toThrow();
+	expect(() => result[1].push('hi')).toThrow();
+});
+
+
+test('multiple input network', () => {
+	const n = network(4, 0, 1)
+		.connect(0, 4, -1.0)
+		.connect(1, 4, -2.0)
+		.connect(2, 4,  1.0)
+		.connect(3, 4,  2.0)
+	
+	expect(n.compute([1, 2, 3, 5], [])).toEqual([
+		[ Math.tanh(
+			(-1.0 * 1) +
+			(-2.0 * 2) +
+			(1.0  * 3) +
+			(2.0  * 5))],
+		[],
+	]);
+});