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

examples/pendulum-simulation/parallel_with_iw.v

@@ -0,0 +1,50 @@
+module main
+
+import benchmark
+import sim
+import sim.args as simargs
+import sim.img
+
+fn main() {
+	args := simargs.parse_args(extra_workers: 1) ? as simargs.ParallelArgs
+
+	img_settings := img.image_settings_from_grid(args.grid)
+
+	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 workers := []thread{cap: args.workers + 1}
+	mut bmark := benchmark.start()
+
+	defer {
+		image_worker := workers.pop()
+		request_chan.close()
+		sim.log('Waiting for workers to finish')
+		workers.wait()
+		result_chan.close()
+		sim.log('Waiting for image writer to finish')
+		image_worker.wait()
+		sim.log('Workers finished!')
+		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])
+	}
+
+	workers << go img.image_worker(mut writer, result_chan, img_settings)
+
+	handle_request := fn [request_chan] (request &sim.SimRequest) ? {
+		request_chan <- request
+	}
+
+	sim.run(args.params,
+		grid: args.grid
+		on_request: sim.SimRequestHandler(handle_request)
+	)
+}