Software Systems
Spring 2008

For today, you should have:

1) started Homework 3

2) Read the Cow book and written a word counter.

3) Read Waldspurger and Weihl.

4) Read the next section of the LBoS.


Outline:

1) Homework 3 questions?

2) Waldspurger and Weihl

3) performance evaluation techniques

4) count.c

5) fork.c

7) One-minute paper.


For next time you should:

1) work on Homework 3

2) Read Chapter 10 of the Cow Book 

3) Do the next semaphore problem (exclusive queue)

4) Read Tanenbaum page 202-210 (no reading questions)

5) prepare for a quiz


Performance evaluation techniques
---------------------------------

1) Analysis: only works for very simple strategies/models

2) Simulation: useful for checking out wide range of
               possibilities.

               depends on workload model or traces

3) Implementation: most reliable, but also depends on
                   workload


Of the three kinds of performance evaluation (analysis, simulation,
implementation) which do Waldspurger and Weihl do?






What is their workload or workload model?






What are their performance metrics?



count.c
-------

You can find all the examples in the Cow Book online, or download
wb/ss/code/cow_book_examples.tar

In general, a good way to program is to start with something
similar to what you want and go from there.

I started with copy.c on page 211

isspace and other character classifiers are in ctype.h

type "man isspace" for more info

The results of count.c agree with wc (at least for WarAndPeace.txt),
so apparently we are using the same definition of "word"

Number of words in WarAndPeace.txt is 566237

If you know about lex, you could generate a word counter like this:

count.lex:

int wordcount = 0;

%option noyywrap

%%

[A-Za-z]+[^A-Za-z]+           ++wordcount;

%%

int main()

{
      yylex();
      printf("%d\n", wordcount);
      return (0);
}



fork.c
------

1) Download fork.c from wb/ss/code

2) Read over the code and make sure you understand it.

3) Compile and run the program.  If you run it without
   a command-line argument, it creates one child process:

   ./fork

   Otherwise you can tell it how many children

   ./fork 5

4) Confirm that the parent and child processes run in
   separate address spaces.

5) In the current program, what does the elapsed time measure?

   How long does it take to create a new process?

6) Copy the time-measurement code into pthread.d and estimate
   how long it takes to create a new thread.