1. Programming project #2 1 CS502 Spring 2006 Programming Project #2 CS-502 Operating Systems Spring 2006

2. Programming project #2 2 CS502 Spring 2006 Programming Assignment 1.Write a mailbox package for communicating among threads. 2.Test your package with a simple program addem that uses multiple threads to add numbers. 3.Use your package to implement a multi- threaded version of the game of Life.

3. Programming project #2 3 CS502 Spring 2006 Purpose To practice writing concurrent programs that share resources and information To practice using the Linux pthread and semaphore facilities To practice structuring a system facility in terms of its interface and implementation

4. Programming project #2 4 CS502 Spring 2006 Part 0: Mailboxes msg structure:– struct msg { int iFrom; // who sent message (thread #) int type; // type (part of payload) int value1 ;// 1 st value (part of payload) int value2 ;// 2 nd value (part of payload) } Operations SendMsg(int iTo, struct msg *pMsg) RecvMsg(int iFrom, struct msg *pMsg) InitMailboxes(int number_of_mailboxes) CleanupMailboxes() Each mailbox can hold at most one message

5. Programming project #2 5 CS502 Spring 2006 Operations on Mailboxes SendMsg(int iTo, struct msg *pMsg) Copies contents of pMsg* into mailbox iTo Blocks if mailbox is already full RecvMsg(int iFrom, struct msg *pMsg) Receives contents from mailbox iFrom, copies to pMsg* Blocks if mailbox is empty InitMailboxes(int number_of_mailboxes) Creates an array of mailboxes, each comprising an instance of msg and the necessary semaphores Initializes the semaphores to indicate mailboxes are empty CleanupMailboxes() Deletes the array of mailboxes and the semaphores

6. Programming project #2 6 CS502 Spring 2006 Semaphores #include Operations of interest:– –sem_init() –sem_wait() –sem_post() –sem_destroy() –…

7. Programming project #2 7 CS502 Spring 2006 Implementation of Mailboxes Implement as a module or package –Mailbox.h as interface Defines msg and all operations –Mailbox.c as implementation Hides all details from client Especially semaphores!

8. Programming project #2 8 CS502 Spring 2006 Part 1: addem Purpose: to test and exercise the Mailbox package Command line –% addem n M –Uses n threads to add the numbers from 1 to M Main thread is thread_0 –Includes pthread.h, Mailbox.h –Reads and parses command line –Initializes n+1 mailboxes using InitMailboxes() –Creates n worker threads, dispatches part of task to each thread via SendMsg –Get results via RecvMsg, combines and prints results. –Cleans up after itself!

9. Programming project #2 9 CS502 Spring 2006 Part 2: Game of Life John Conway, Scientific American, April 1970. Rectangular grid, n  m squares Each square has eight nearest neighbors May be occupied or unoccupied Rules for next generation An occupied square with 0 or 1 occupied neighbors dies of loneliness An occupied with 4, 5, 6, 7, or 8 neighbors dies of overcrowding An occupied with 2 or 3 occupied neighbors survives An unoccupied square with exactly 3 occupied neighbors becomes occupied

10. Programming project #2 10 CS502 Spring 2006 Example Generation 0: 0 1 0 0 0 0 1 1 1 0 0 0 Generation 1: 0 0 1 0 0 1 1 0 0 0

11. Programming project #2 11 CS502 Spring 2006 Operation Command line –% life n filename g [print [input]] –Uses n threads to play g generations starting from the position in file filename –Optional arguments print and input are to aid in debugging

12. Programming project #2 12 CS502 Spring 2006 Operation (continued) Main thread is thread_0 –Includes pthread.h, Mailbox.h –Reads and parses command line –Creates even and odd generation arrays Initializes even array from file –Initializes n+1 mailboxes using InitMailboxes() –Creates n worker threads, dispatches range of rows to each thread via SendMsg –Loops to compute generations Sends go message to each thread Get results via RecvMsg Combines results into new generation array Determines whether or not it is time to stop –Cleans up after itself!

13. Programming project #2 13 CS502 Spring 2006 Project Submission Due Monday, March 6 at start of class Must run on CS or CCC computers at WPI! Submit via turnin command = ‘ /cs/bin/turnin ’ on CCC machines classname = ‘ cs502 ’ assignment = ‘ project2 ’ Include Code, makefiles, test files or input, test output Bring printed copy to class.