Description
At the beginning of your lab period, the lab instructor will briefly review the functionality of the UNIX
nice(1) command. You will need to use nice(1) in question 2g of this lab. The time(1) command—
including the meaning of elapsed time and user CPU time—will also be reviewed.
Solve or complete each of the tasks or problems below. For all problems involving the use of LINUX/UNIX
commands, place the command or pipeline you used along with the resulting output (i.e. copy-and-paste from
your terminal window) in a file called lab8.txt. However, do not include extraneous or superfluous commands or output; only include content relevant and essential to the specified task. Then, with a text editor,
add to lab8.txt identifying information to clearly distinguish which commands/output/code/description
correspond to each task/question. When done, hand in lab8.txt and your modified Makefile from question 2e through the moodle page for the lab. This lab is out of a total of 14 marks; the number of marks
allocated to each question is indicated below. Marks may be docked for extraneous, irrelevant, or superfluous
content or for not following directions. Your submission is due at 11:55 p.m. on Thursday, November 3.
Note that specific platforms need to be used for some of the commands.
1. (1 mark) As you already know, information on UNIX commands can be obtained from their manual
pages. However, some commands also contain additional information in “info pages”. Use the info(1)
LINUX/UNIX command to view the info page for make on tuxworld. Among many other pieces of
information, this info page lists possible values for the special variable .FEATURES—information not
found in the manual page for make. Find the list of these values, and then copy-and-paste the description of the list of possible values for variable .FEATURES into lab8.txt.
2. Perform this question on your an ismac machine in Rm S311 or RmS315. Do not use tuxworld for this
question. Include in lab8.txt a log of each step, except as noted.
(a) (1 mark) Download the file queens14.cc from the “Examples” portion of the course web pages
and compile it manually (i.e. without using a makefile), calling the executable file nqueens. You
will need this file in step 2g. You do not need to show a log of the download in lab8.txt.
(b) (1 mark) Use the curl(1) command to download the source code for the factor program from
the following URL:
http://www.acme.com/software/factor/factor_02Jun2016.tar.gz
A bit of documentation for this program is available at this URL:
http://www.acme.com/software/factor/
(c) (1 mark) Use a UNIX command to un-tar (unpack) the file you downloaded in part 2b. Then
change your current directory to the factor subdirectory that was just created. Notice that the
source code for factor is written in C.
1
(d) (1 mark) Use the make(1) command with appropriate options to print the commands thatwould
be executed if you were to invoke make at this point (with no options or arguments). It is always
a good idea to do this before using someone else’s makefile just to make sure it isn’t going to do
anything you are not expecting or would not approve of.
(e) (1 mark) You may have noticed that the output from step 2d showed a cc command involving the
“-s” option. This option is deprecated, and should be removed from the set of LDFLAGS. Copy
the original Makefile to Makefile.org. Then edit the Makefile to remove the use of the “-s”
option. You do not need to submit a log of your editing. Finally, using diff(1) show the changes
you made to the Makefile.
(f) (2 marks) Use make to build the factor program. Do not “make install”. Test the factor
program with a few inputs to get an idea of what the output looks like. Note that there may be
another program called factor in the directories specified by your PATH; if so, you will need to explicitly specify the path to your newly-built factor (i.e. “./factor”) in order to run it. Make sure
to test factor on a range of inputs (the documentation at http://www.acme.com/software/factor/
will be necessary for this). Finally, change your working directory back to the one with nqueens
in it.
(g) For this part of the question, you are required to run the command “./nqueens 6” (this is the
nqueens you compiled in step 2a) under three different conditions. For each of the conditions,
you are to use the time(1) command to measure the amount of time taken by nqueens. The
three conditions are as follows:
i. (1 mark) For the first condition, just run nqueens by itself, without running anything else
concurrently. Use time(1) to run nqueens. Note that it might take a minute or two for the
computation to complete.
ii. (2 marks) For the second condition, start ten instances of the command
“factor/factor 30000000-90000000 > /dev/null &”. Next, use the command “ps -O nice”
to output the “nice number” of your processes, including these factor processes. Then give
the same timed nqueens command as in part 2(g)i. Make sure these three steps are performed in rapid succession. After nqueens completes, kill all of the factor processes. The
killall(1) command is useful for this.
Recall that to quickly re-invoke the last command given to the shell you can use “!!”. Alternatively, you can use the up-arrow key on the right side of the keyboard to retrieve the last
command from the HISTORY buffer.
iii. (2 marks) For the third condition, run ten instances of the same factor command as in 2(g)ii
(before running nqueens), but with the “nice number” of each factor process incremented by
10. Use the nice(1) command for this. After starting the ten instances of factor, execute
the command “ps -O nice” to show that the nice numbers of these processes have indeed
been changed from the situation in part 2(g)ii. Then run the timed nqueens command (again
using time(1)). Kill all of the factor processes after nqueens completes.
(h) (1 mark) Were there any differences in the elapsed times taken in i, ii, and iii? What about the
user CPU times? In lab8.txt comment on why these differences occurred (or did not occur).
You will be using the factor program in next week’s lab, so make sure not to delete it.
2