examples: improve the pendulum simulation, with several modes and diagrams (#13446)

examples/pendulum-simulation/modules/sim/worker.v

@@ -0,0 +1,67 @@
+module sim
+
+import math
+import benchmark
+
+const (
+	max_iterations     = 1000
+	simulation_delta_t = 0.0005
+)
+
+pub struct SimRequest {
+	params SimParams
+	state  SimState
+pub:
+	id int
+}
+
+pub struct SimResult {
+	state SimState
+pub:
+	id               int
+	magnet1_distance f64
+	magnet2_distance f64
+	magnet3_distance f64
+}
+
+pub fn sim_worker(id int, request_chan chan &SimRequest, result_channels []chan &SimResult) {
+	mut bmark := benchmark.new_benchmark()
+	for {
+		request := <-request_chan or { break }
+		bmark.step()
+		result := compute_result(request)
+		for ch in result_channels {
+			ch <- result
+		}
+		bmark.ok()
+	}
+	bmark.stop()
+	println(bmark.total_message(@FN + ': worker $id'))
+}
+
+pub fn compute_result(request SimRequest) &SimResult {
+	mut state := request.state
+	params := request.params
+
+	for _ in 0 .. sim.max_iterations {
+		state.increment(sim.simulation_delta_t, params)
+		if state.done() {
+			println('done!')
+			break
+		}
+	}
+
+	m1_dist := params.get_magnet_dist(0, state)
+	m2_dist := params.get_magnet_dist(2.0 * math.pi / 3.0, state)
+	m3_dist := params.get_magnet_dist(4.0 * math.pi / 3.0, state)
+
+	id := request.id
+
+	return &SimResult{
+		id: id
+		state: state
+		magnet1_distance: m1_dist
+		magnet2_distance: m2_dist
+		magnet3_distance: m3_dist
+	}
+}