CSCI 4061 Lab11: Threads and Worms

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                            LAB 11 QUESTIONS
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- Name: (FILL THIS in)
- NetID: (THE kauf095 IN kauf0095@umn.edu)

Answer the questions below according to the lab specification. Write
your answers directly in this text file and submit it to complete Lab01.


PROBLEM 1: The Setup
====================

A
~

  Compile and run `worm_pthread.c' using the provided Makefile. Make
  sure to follow the program prompts.  Describe what you observe. Also
  do brief research and find out what the Unix command `watch' does and
  how it is used with this program.


B
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  Consult the structure of the `main()' function. Determine how changes
  to the file `worm_board.txt' are made. What special tricks are used to
  make it relatively easy to change the file AND to change specific
  portions of the file.


C
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  Describe the area of code in `main()' which creates threads and awaits
  them finishing.
  - Describe the function which is used to start a thread running and
    its arguments. Consult the manual for documentation on this function
    if needed.
  - Describe the function which is used to wait until a thread finishes.


PROBLEM 2: The Worms
====================

A
~

  Examine the `worm_func()' function carefully.  You may wish to
  consider the specific data passed to these worms which are in the
  array of `wormparam_t' structs midway through `main()'.

  Describe the basic algorithm that worms follow to do their work.


B
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  Describe how worms avoid both claiming the same piece of
  territory. What system call mechanism is used to ensure that two worms
  cannot claim the same area of the board? Describe the function calls
  that are used to accomplish this and what functions in `main()' are
  used to set up this coordination mechanism.


C
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  Describe the logic that appears to cause worms to be 'fast' and
  'slow': how is this artificial speed actually created in the
  `worm_func()' code.

  While the speed differences of worms is an intended creation of the
  program, speculate as to what use threads can be when dealing with
  entities of different speeds.


Optional Enrichment: Threads in Python
======================================

  Threads are not unique to C and the Pthreads library. Most modern
  programming environments include some version of them. The prototype
  version of the worms program was written in Python and can be found in
  `worms.py' and can be run via
  ,----
  | > ./worms.py
  `----
  - No territory or step numbers are tracked in the Python version; it
    runs until Ctrl-c is pressed
  - This version does not use a memory mapped file instead showing the
    board on the console.
  - The `curses' library is used to manipulate the terminal screen which
    allows for boxes and color to be used but complicates the
    implementation somewhat.
  - Python features several types of mutual exclusion locks including
    one used here that can be re-locked by the same thread without
    negative effects.

  Time permitting, explore the code of `worms.py' and draw some
  parallels as to the C code.