hi everyone,

some announcements -

  o i've graded hw 4, will grade hw5/6 tomorrow, mail 4/5/6 on wednesday

  o i've decided to change hw9.  my reason for this is that while the  material
    is very nice, the questions in the book don't really capture the essence of
    the material.  (the questions are more about implementating small
    applications, not so much about notation.)

    instead of questions 1, 3, 8, and 18 from the chapter, i'd like you to read
    the material and write a summary of what you learned.  (1-3 paragraphs
    per section.)

  o i'll be out of the country for a few weeks, leaving july 17.  my contact
    information will be on my web page, and i'll be checking email.  i'll grade
    the last two submissions remotely, will email grades back.

hw 7/8 is due sunday july 23 at 11:59pm.

chapter 7 is about performance.  in my opinion, most undergraduate classes
stress performance far too much - perhaps because it's more quantiative,
and therefore has more academic respectability.  POP makes the point early
in chapter 7 that the first principle of optimization is DON'T.  if it's
good enough, the only reason to boost performance is to show how clever
you are (and invariably you'll fall flat on your facing doing so -
performance tuning can introduce all sorts of nasty corner-case bugs,
takes much longer than you expected, etc.)

one interesting aspect of the performance optimizations that POP talks
about is that they go beyond the usual big-Oh data structure and
algorithms theory, and also includes a detailed discussion of "tuning" -
this includes things like cacheing, special purpose allocation,
precomputing results, etc.

chapter 8 is about portability.  there are many ways in which a program
can fail to be portable, some of which are obivous (assumptions about word
length), whereas others are a lot more subtle, e.g., the memory footprint
and the organization of a struct/object in memory is a function of the
compiler, and writing out these objects in raw byte order can be
disastrous.  more generally, it's easy to forget that a lot of your code
calls library functions, many of which are not guaranteed to exist.

chapter 8 is fairly short, and if you really want to learn about
portability, the best book i have come across is "write portable code" by
brian hook (no starch press).  i've seen it at borders as well as barnes
and noble, so check it out the next time you're there.

cheers,
adnan