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

examples/pendulum-simulation/parallel.v

@@ -0,0 +1,84 @@
+module main
+
+import benchmark
+import sim
+import sim.args as simargs
+import sim.img
+
+fn main() {
+	args := simargs.parse_args() ? as simargs.ParallelArgs
+
+	img_settings := img.image_settings_from_grid(args.grid)
+
+	width := img_settings.width
+	height := img_settings.height
+	total_pixels := width * height
+
+	request_chan := chan &sim.SimRequest{cap: args.workers}
+	result_chan := chan &sim.SimResult{cap: args.workers}
+
+	mut writer := img.ppm_writer_for_fname(args.filename, img_settings) ?
+	mut image_writer := img.new_image_writer(mut writer, img_settings)
+
+	mut workers := []thread{cap: args.workers}
+	mut bmark := benchmark.start()
+
+	defer {
+		request_chan.close()
+		sim.log('Waiting for workers to finish')
+		workers.wait()
+		result_chan.close()
+		bmark.measure(@FN)
+		sim.log('Closing writer file')
+		writer.close()
+		sim.log('Done!')
+	}
+
+	for id in 0 .. args.workers {
+		workers << go sim.sim_worker(id, request_chan, [result_chan])
+	}
+
+	mut x := 0
+	mut y := 0
+	mut request_index := 0
+
+	for {
+		// setup state conditions
+		position := sim.vector(
+			x: 0.1 * ((f64(x) - 0.5 * f64(width - 1)) / f64(width - 1))
+			y: 0.1 * ((f64(y) - 0.5 * f64(height - 1)) / f64(height - 1))
+			z: 0.0
+		)
+		velocity := sim.vector(x: 0, y: 0, z: 0)
+
+		mut state := sim.new_state(
+			position: position
+			velocity: velocity
+		)
+
+		state.satisfy_rope_constraint(args.params)
+		request := &sim.SimRequest{
+			id: request_index
+			state: state
+			params: args.params
+		}
+		select {
+			result := <-result_chan {
+				image_writer.handle(result) or { break }
+			}
+			else {
+				if request.id == total_pixels {
+					continue
+				}
+				request_chan <- request
+				x++
+				if x == width {
+					x = 0
+					y++
+					sim.log('y: ${y + 1}')
+				}
+				request_index++
+			}
+		}
+	}
+}