Errata

Last updated October 13, 1997.

Delete question 3 from the distributed dining philosophers assignment on page 175. Deadlock is not possible if all forks are initially dirty and philosopher 1 has two.

On page 130 the implementation of signal and wait for signal-and-continue using semaphores is not correct. It should read

wait(condi):
   COUNTi++
   V(mutex)
   P(SEMi)
   P(mutex)
 ...
signal(condi):
   if COUNTi > 0 then
      COUNTi--
      V(SEMi)
   fi
   V(mutex)
   exit the monitor, i.e., return

A major oversight in the Acknowledgements is not thanking the team at the University of Arizona that developed SR: Greg Andrews, Ron Olsson, Gregg Townsend, and many graduate students. I am grateful to them for designing and implementing a very nice concurrent programming language that I have found extremely useful in my teaching.

There are some minor typographical errors in the text part of the book. These are readily identifiable.

Program 6.14, the driver for the lock example, has some statements out of order in the do true loop in process a_user. The loop should be changed from

do true ->
   napping := int(random(1000*nap_time))
   write("age()=", age(), "user", i, "napping for", napping)
   napping := int(random(1000*nap_time))
   nap(napping)
   write("age()=", age(), "user", i, "doing a down")
   S.down()
   write("age()=", age(), "after down, user", i, "napping for", napping)
   napping := int(random(1000*nap_time))
   nap(napping)
   write("age()=", age(), "user", i, "doing an up")
   S.up()
od

do true ->
   napping := int(random(1000*nap_time))
   write("age()=", age(), "user", i, "napping for", napping)
   nap(napping)
   write("age()=", age(), "user", i, "doing a down")
   S.down()
   napping := int(random(1000*nap_time))
   write("age()=", age(), "after down, user", i, "napping for", napping)
   nap(napping)
   write("age()=", age(), "user", i, "doing an up")
   S.up()
od

Here is the complete fixed program with a new example run.

Some minor changes have been made to the following programs:

5.04: changed see_if_very_hunger to see_if_very_hungry; mentioned nested _proc() causes deadlock in a comment
5.06: changed # style comments to /* */ as per the manual page for m2sr
6.03: took out max := n*n and changed fa loop to do (still by 2)

Here are the complete fixed programs: Program 5.04, Program 5.06, Program 6.03.

The global resource SRanimator, Program 7.15, is an earlier version of the one distributed in version 2.3 (October 1994) of the SR software. Several new animation actions are supported.

  op A_fonttext(id : int; lx, ly : real; cen : int; colorr, fontname, str : string[*])
  op A_stepjump(id : int; tx, ty : real; nsteps, steptime : int)
  op A_stepjumpto(id1, id2 : int; nsteps, steptime : int)
  op A_resize(id : int; rx, ry: real)
  op A_zoom(id : int; rx, ry: real)
  op jumpsteps(id : int; tx, ty : real; nsteps, steptime : int)
  op jumptosteps(id1, id2 : int; nsteps, steptime : int)

And two new parameters, style and arrows, were added to the line drawing procedure.

  op A_line (id : int; lx, ly, sx, sy : real; colorr, width, style, arrows : string[*])

For more details, see the paper sranimator.ps in the doc directory of the SR distribution.

In the Instructor's Manual, ``See Section 7.5.3 for a similar experiment using quicksort.'' should read ``See the Parallel Computing section on page 79....''

SJH

shartley@mcs.drexel.edu