Lab 8 - Quicksort
Most of the code for this lab is provided for you in the
lab8 directory. Create a new subdirectory for this lab
on Helios. Change to that subdirectory and type the following to copy all of
the files over:
cp /usr/users/mdanfor/public_html/cs223-f07/lab8/* .
File Descriptions
file_gen.cpp - This is a variation on the file
generator used for the homework assignment. It generates data in the range of
0 to 999. It also seeds random with the current time instead of a static
value. You can compile file_gen.cpp with make file_gen which will
make an executable called file_gen
vt100ansi.h - This header file allows colors to
be printed to the screen using the macro vtprintf(COLOR) where
COLOR is one of the colors defined in the file.
quicksort.cpp - This defines the quicksort
algorithm using median-of-three pivots. It will call insertion sort when the
number of elements is less than the defined THRESHOLD value. You can run
quicksort in debug mode by defining DEBUG_MODE. In debug mode, information
about choosing the pivot, making the swaps and doing insertion sort are
printed to the screen. Since there is a lot of information, SLEEP_SEC defines
how long the debug mode pauses between stages so that the information can be
read.
lab8main.cpp - This is the main program. You
will need to fill in a little code to open the specified file and read the
data into the local array. (Note: You will need to do a similar task to this
in the current homework assignment too). To compile lab8main.cpp after making
the required changes, type make main. This will create an
executable called main, which can be run with
main input1 or any other filename.
input1, input2 and
input3 - Pre-generated input files containing 40
integers each.
Makefile - A makefile to compile the above code
into executables.
Assignment
Fill in the required portion of lab8main.cpp and compile the program. Test
different file sizes and see how quicksort partitions the lists. Notice how
even when the list is not partitioned in the middle, the split operation still
runs quickly. Turn off debugging mode by removing, commenting out or undef
the DEBUG_MODE line and recompile the program with make main.
Try running the following:
time main input1
This will show you how long it takes to run the quicksort executable for
input1. Try generating larger files and compare the runtime. Helios is
pretty fast, so you may need to increase MAX_CAPACITY to 5000 or 10000 and
sort a file of that size to see a noticeable difference in the time.
Email me a small writeup (1-2 paragraphs is sufficient) of what you've seen
following these instructions and your modified lab8main.cpp.