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	Stylistshop I Requirement An Exercise of the Synchronization of Autonomous Processes 20140727 We use this exercise to analyze a simplified business model. The requirement is as the following. We review threads synchronization in Java at the same time. /* Stylist Shop - The shop has a NumberofWorkers>0 hairdressers. - The shop starts slightly before its business hour. - - So the first customer always get served. - - Business hours are 9-5, namely 836001000 milliseconds. For convenience of simulation, the duration will be scaled down to 83600 milliseconds. Each IndividualServiceTime will take half an hour, 36001000/2 milliseconds. - In program segments, there should not be hard-coded values. The above constants are set as class constants. They are adjustable ONLY before each simulation is run, or say at pre-compilation/assembly time. - At the end of business day, a report will be generated: - - total customer served - - detail of each customer visited, visiting time, worker ID (if not served, this set 0), partially implemented. / / - Each customer has a unique ID. - The customer will be generated by a thread. - - Market research shows each day, there could be [MinVisitors,MaxVisitors]. The generator will simulate customers' random visiting to the shop. We would consider this research to be expected but not guaranteed. - - When a customer comes, if there is worker available, the customer will take the service without preference. Suppose the shop has a board/screen, showing the workers available. The customer simply uses the service first available or leaves if none available. / / Worker: - each worker has a unique ID - For each customer, IndividualServiceTime will take half an hour, 36001000/2 milliseconds. - After a hairdresser served a customer, the worker will report the status as available, and vice versa. /
	Stylistshop II the Customer Model 20140727 The customer model generates events in this producer-consumer data structure. class Customer { private long serverId = 0l; public long getServerId() { return serverId; } public void setServerId(long serverId) { this.serverId = serverId; } private long id = 0; public Customer() { super(); id = count.incrementAndGet(); } public long getId() { return id; } public void setId(long id) { this.id = id; } public static AtomicLong count = new AtomicLong(0l); public static class LeadGenerator implements Runnable { private boolean halted = false; public boolean isHalted() { return halted; } public void setHalted(boolean halted) { this.halted = halted; } public void run() { while (!halted) { try { TimeUnit.MILLISECONDS .sleep(((long) (Math.random() * ((StilystShop.EndTime - StilystShop.StartTime) / StilystShop.MinVisitors - (StilystShop.EndTime - StilystShop.StartTime) / StilystShop.MaxVisitors)) + (StilystShop.EndTime - StilystShop.StartTime) / StilystShop.MaxVisitors) / StilystShop.TimeScaleDownFactor); // System.out.println("Generated."); } catch (InterruptedException e) { // e.printStackTrace(); }// sleep Customer c = new Customer(); lc.add(c); StilystShop.getInstance().serveOne(c); } // System.out.println("Lead generator ended."); } } public static List<Customer> lc = new ArrayList<Customer>(); }
	Stylistshop III the Worker Model 20140727 The worker model processes events and report status in this producer-consumer data structure. class Worker implements Runnable { private long id = 0; public long getId() { return id; } public void setId(long id) { this.id = id; } public static AtomicLong count = new AtomicLong(0l); public Worker() { super(); id = count.incrementAndGet(); } private volatile boolean available = true; public static final long IndividualServiceTime = 3600 * 1000 / 2; public synchronized boolean isAvailable() { return available; } private boolean halted = false; public boolean isHalted() { return halted; } public void setHalted(boolean halted) { this.halted = halted; } // public void setAvailable(boolean available) { // this.available = available; // } public void run() { while (!halted) { synchronized (this) { try { this.wait(); available = false; } catch (InterruptedException e) { // e.printStackTrace(); } } try { TimeUnit.MILLISECONDS.sleep(IndividualServiceTime/StilystShop.TimeScaleDownFactor); } catch (InterruptedException e) { } available = true; } } }
	Stylistshop IV synchronized or noise? 20140727 Put things in one file. package net.heteroclinic.experiment.stylistshop; import java.util.ArrayList; import java.util.List; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.Future; import java.util.concurrent.TimeUnit; import java.util.concurrent.atomic.AtomicLong; /* Stylist Shop - The shop has a NumberofWorkers>0 hairdressers. - The shop starts slightly before its business hour. - - So the first customer always get served. - - Business hours are 9-5, namely 836001000 milliseconds. For convenience of simulation, the duration will be scaled down to 83600 milliseconds. Each IndividualServiceTime will take half an hour, 36001000/2 milliseconds. - In program segments, there should not be hard-coded values. The above constants are set as class constants. They are adjustable ONLY before each simulation is run, or say at pre-compilation/assembly time. - At the end of business day, a report will be generated: - - total customer served - - detail of each customer visited, visiting time, worker ID (if not served, this set 0), partially implemented. / / - Each customer has a unique ID. - The customer will be generated by a thread. - - Market research shows each day, there could be [MinVisitors,MaxVisitors]. The generator will simulate customers' random visiting to the shop. We would consider this research to be expected but not guaranteed. - - When a customer comes, if there is worker available, the customer will take the service without preference. Suppose the shop has a board/screen, showing the workers available. The customer simply uses the service first available or leaves if none available. / class Customer { private long serverId = 0l; public long getServerId() { return serverId; } public void setServerId(long serverId) { this.serverId = serverId; } private long id = 0; public Customer() { super(); id = count.incrementAndGet(); } public long getId() { return id; } public void setId(long id) { this.id = id; } public static AtomicLong count = new AtomicLong(0l); public static class LeadGenerator implements Runnable { private boolean halted = false; public boolean isHalted() { return halted; } public void setHalted(boolean halted) { this.halted = halted; } public void run() { while (!halted) { try { TimeUnit.MILLISECONDS .sleep(((long) (Math.random() ((StilystShop.EndTime - StilystShop.StartTime) / StilystShop.MinVisitors - (StilystShop.EndTime - StilystShop.StartTime) / StilystShop.MaxVisitors)) + (StilystShop.EndTime - StilystShop.StartTime) / StilystShop.MaxVisitors) / StilystShop.TimeScaleDownFactor); // System.out.println("Generated."); } catch (InterruptedException e) { // e.printStackTrace(); }// sleep Customer c = new Customer(); lc.add(c); StilystShop.getInstance().serveOne(c); } // System.out.println("Lead generator ended."); } } public static List<Customer> lc = new ArrayList<Customer>(); } /* Worker: - each worker has a unique ID - For each customer, IndividualServiceTime will take half an hour, 36001000/2 milliseconds. - After a hairdresser served a customer, the worker will report the status as available, and vice versa. / class Worker implements Runnable { private long id = 0; public long getId() { return id; } public void setId(long id) { this.id = id; } public static AtomicLong count = new AtomicLong(0l); public Worker() { super(); id = count.incrementAndGet(); } private volatile boolean available = true; public static final long IndividualServiceTime = 3600 * 1000 / 2; public synchronized boolean isAvailable() { return available; } private boolean halted = false; public boolean isHalted() { return halted; } public void setHalted(boolean halted) { this.halted = halted; } // public void setAvailable(boolean available) { // this.available = available; // } public void run() { while (!halted) { synchronized (this) { try { this.wait(); available = false; } catch (InterruptedException e) { // e.printStackTrace(); } } try { TimeUnit.MILLISECONDS.sleep(IndividualServiceTime/StilystShop.TimeScaleDownFactor); } catch (InterruptedException e) { } available = true; } } } public class StilystShop { public static final int NumberofWorkers = 3; public static final long MinVisitors = 57; public static final long MaxVisitors = 120; // in milliseconds public static final long StartTime = 0l; public static final long EndTime = StartTime + 8 * 3600 * 1000; // In simulation one second becomes one millisecond. public static final long TimeScaleDownFactor = 1000l; private boolean running = false; private StilystShop() { }; protected static StilystShop instance = new StilystShop(); private List<Worker> workers = new ArrayList<Worker>(); public void addAWorker(Worker w) { workers.add(w); } public static Object board = new Object(); public static synchronized StilystShop getInstance() { if (null == instance) { instance = new StilystShop(); } return instance; } // private int serviceCount = 0; public static List<Customer> customerServed = new ArrayList<Customer>(); public int getServiceCount() { return customerServed.size(); } public void serveOne(Customer c) { // start of a transaction synchronized (board) { board.notify(); for (Worker w: workers) { if (w.isAvailable()) { synchronized (w) { c.setServerId(w.getId()); customerServed.add(c); w.notify(); } break; } } } // end of a transaction } public static void main(String[] args) throws InterruptedException { List<Future<?>> fl = new ArrayList<Future<?>>(); ExecutorService exec = Executors.newCachedThreadPool(); StilystShop.ShopRunner sr = new StilystShop.ShopRunner(); Customer.LeadGenerator lg = new Customer.LeadGenerator(); for (int i = 0; i<3 ; i++) { Worker w = new Worker(); StilystShop.getInstance().addAWorker(w); fl.add(exec.submit(w)); } fl.add(exec.submit(sr)); // There should be a barrier before fl.add(exec.submit(lg)); TimeUnit.MILLISECONDS .sleep((StilystShop.EndTime - StilystShop.StartTime) / StilystShop.TimeScaleDownFactor); // System.out.println("Shop closed, printing report."); lg.setHalted(true); sr.setHalted(true); exec.shutdown(); for (Future<?> f : fl) f.cancel(true); } public static class ShopRunner implements Runnable { private boolean halted = false; private int doorBellCount = 0; public boolean isHalted() { return halted; } public void setHalted(boolean halted) { this.halted = halted; } public void run() { while (!halted) { try { // TimeUnit.MILLISECONDS.sleep(10); synchronized (board) { board.wait(); } //System.out.println("One served."); doorBellCount ++; } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } } StilystShop.getInstance().stop(); System.out.println("Shop closed, printing report. " + doorBellCount + " visitors."); System.out.println("Audit:"); for (Customer c:customerServed ) { System.out.println(""+c.getId()+"\t"+ c.getServerId()); } } } public void stop() { for (Worker w: workers) { w.setHalted(true); synchronized (w) { w.notify(); } } } }