Expectations for CS152 garbage collector
We divided the problem into stages to help you pace yourself;
the stages don't carry equal weight for grading.
The second and third stages carry approximately the same weight, and
together they account for the bulk of your grade.
Stage 4 will account for a small part of your grade.
Your explanation of your solution to this assignment is most important
and will count for approximately half your grade. Although we do not
require that you do so, you may find it
advisable to use TeX, Frame, Word, WordPerfect, or a similar program
to prepare a PostScript README file.
For stages 2 and 3 we expect your written explanation to include:
In addition to checking your code and your explanation, we will test
your dump-stack primitive and your garbage collector on a variety
- A complete list of types that could lead to values of type
SEXP. We will check your code to see that you have
implemented a tracing procedure for each such type.
- A complete list of roots, that is, values of the stated types.
This list should include not only global variables but also local
variables and parameters of specific procedures.
Do mention individual variables by name.
- An explanation of how you provide these roots to the allocator
(which must always be prepared to pass them on to the collector).
For global variables this is obvious, since every procedure always has
access to them. You will have to explain, however, how you provide
access to local variables and parameters.
We will check your code to see that every root on your list is made
available to the allocator.
It is acceptable not to provide all the roots while
collection is turned off, that is, in an ``unsafe'' region.
statement of the invariants and an argument about why the invariants
are maintained. Your argument should be clear and concise, but a
formal, mathematical proof is not necessary.
Your argument should state all the invariants,
name the global data
structures that participate in those invariants, and show how every
procedure that touches one of those data structures maintains the
If you are not familiar with this style of argument, seek help
For stage 4, we will check your implementation to see that you have
provided the measurements called for in the problem statement, but
the bulk of your grade will be based on your explanation.
Your explanation should cover two points:
- What changes to the allocator and collector are needed to
accomodate the variable Gamma?
What new invariants are added?
3 and 4 differ? You should compare the behavior of stages 3 and 4 on
both merge sort and insertion sort and explain the differences for
both small and large n. It may help you to know that in both
running time and memory consumption, insertion sort is
O(n-squared) whereas merge sort is O(n log n).