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Programming Project #2

Programming Project #2. CS-502 Operating Systems Spring 2006. Programming Assignment. Write a mailbox package for communicating among threads. Test your package with a simple program addem that uses multiple threads to add numbers.

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Programming Project #2

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

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

  3. 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 CS502 Spring 2006

  4. Part 0: Mailboxes • msg structure:– struct msg { int iFrom; // who sent message (thread #) int type; // type (part of payload) int value1;// 1st value (part of payload) int value2;// 2nd 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 CS502 Spring 2006

  5. 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 CS502 Spring 2006

  6. Semaphores #include <semaphore.h> • Operations of interest:– • sem_init() • sem_wait() • sem_post() • sem_destroy() • … CS502 Spring 2006

  7. 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! CS502 Spring 2006

  8. Part 1: addem • Purpose: to test and exercise the Mailbox package • Command line • % addem nM • 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! CS502 Spring 2006

  9. 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 CS502 Spring 2006

  10. 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 0 0 CS502 Spring 2006

  11. 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 CS502 Spring 2006

  12. 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! CS502 Spring 2006

  13. 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. CS502 Spring 2006

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