C线程代业辅导代调试、POSIX Threads代编码

(CSCI 363) Project Two -- POSIX Threads

Instructions

This program sorts strings using "enzymes".  An enzyme is a function that sorts two consecutive

characters.  We define one enzyme per pair of consecutive characters; these enzymes working

together in parallel can sort the entire string.  We use pthreads to instantiate and parallelize the

enzymes.

Unfortunately, this program doesn't seem to be working correctly.  That's where you come in.

Before you edit the code, read through it, and answer these questions:

 1) Briefly explain why this application would be difficult to write using multiple processes

instead of threads.

 2) What is the significance of 'workperformed'?  How is it used?

 3) Explain exactly what is the type of 'fp' in the following declaration: void *(*fp)(void *)

Now, to fix the program:

 1) The function run_enzyme() needs to be created. Please see the notes inside enzyme.c.

 2) The function 'make_enzyme_threads' has a memory bug. Fix this by simply re-ordering the

lines in this function.  It is simple fix but may take a while for you to find it.

 3) The function 'join_on_enzymes' is incomplete. Read the relevant man pages and figure out

how the function is supposed to work. Then insert the correct code snippets into

'whatgoeshere'.

 4) Your programming work can be considered complete when you have completed the above

and all of the tests pass.

Testing

make test

./enzyme -test -f0 all

Running tests...

1.make                ::pass

2.sort                ::pass

3.pleasequit1         ::pass

4.pleasequit0         ::pass

5.swap1               ::pass

6.swap2               ::pass

7.swap3               ::pass

8.run_enzyme          ::pass

9.join                ::pass

10.cancel             ::pass

You may also want to experiment with the cancel function -

./enzyme Cba

./enzyme CBA

Questions

 1) Why do we not detach any of the enzyme threads? Would the program function if we

detached the sleeper thread?

 2) Why does the program use sched_yield? What happens if this is not used? Will the swap

counts always be identical?

 3) Threads are cancelled if the string contains a 'C' e.g. "Cherub". Why do we not include

cancelled threads when adding up the total number of swaps?

 4) What happens when a thread tries to join itself? (You may need to create a test program to

try this) Does it deadlock? Or does it generate an error?

 5) Briefly explain how the sleeper thread is implemented.

 6) Briefly explain why PTHREAD_CANCEL_ASYNCHRONOUS is used in this MP.

 7) Briefly explain the bug in #2 of fix the program section above.

Turn In

Enzyme.c (i.e. finish fix the program section tasks) and YourName.docx (i.e. answer the

questions above). Due date will be announced on Blackboard.