Description
Purpose: Become more familiar with input/output buffering concepts.
Points: 50 (Description 10 pts, Write-up 40 pts)
Assignment:
Update the assignment #11 code to change the buffer
size from 750,000 to 3. Execute the original program
from assignment #11 A (buffer of 750,000) and the
modified assignment #11 B (buffer of 1). We will use
the Unix time1
command to obtain the execution
times. Additionally, we will use the Unix diff2
command which compares two files and reports any
differences. There should be no differences between
the created thumbnail file and the provided master
thumbnail file.
To simplify this process, a script file is provided to
execute the program two times with each executable
file. The timing results are placed in a file
a11times.txt.
● Summarize your results for assignment #11 A
and B. The write up (in write_up.txt)
should include the following information.
○ Briefly describe your machine (one
sentence). Include the machine type (desktop/laptop/mini), processor speed, disk type (ssd,
hard-drive, etc.) and memory.
○ Compute the average ‘real’ time for the two ‘large’ buffer size executions (original). Ensure
to leave the original two results and add the final averaged result.
○ Compute the average ‘real’ time for the two ‘small’ buffer size executions. Ensure to leave
the original two results and add the final averaged result.
○ State which was faster and by how much. Include the time difference and the percentage
faster or slower. The percentage change3
should be calcualted as follows:
percentChange = (
(small buffer average)−(large buffer average )
(large buffer average) )
∗ 100
○ Explaination of the results. Specifically, explain the impact of the buffer size on the
execution speed of the program. Explaination should not exceed 200 words. (40 pts)
Note, any explainations exceeding 200 words will not be graded and scored as a 0.
1 For more information, refer to: http://en.wikipedia.org/wiki/Time_(Unix)
2 For more information, refer to: http://en.wikipedia.org/wiki/Diff
3 For more information, refer to: http://en.wikipedia.org/wiki/Percent_change
Source: xkcd.com/612
Assignment #11B Timing Script
The following commands will execute the program and provide timing results (for both the ‘large’ and
‘small’ buffers).
ed-vm% time ./makeThumbLG moon.bmp tmp1.bmp
ed-vm% diff tmp1.bmp mstr.bmp
ed-vm%
ed-vm% time ./makeThumbSM moon.bmp tmp2.bmp
ed-vm% diff tmp2.bmp mstr.bmp
ed-vm%
To automate this process, a script file is provided that will execute the assignment #11 two times for
the ‘large’ buffer size and two times for the ‘small’ buffer size and place the results in a file. You can
download the script file, set the permission, and execute as follows:
ed-vm$ chmod +x a11timer
ed-vm$ ./a11timer makeThumbLG makeThumbSM
Where makeThumbLG is the assignment #11 A executable (with the large buffer) and makeThumbSM
is the assignment #11 B executable (with the small buffer).
You will need to perform the averaging using a calculator. Be careful of the minutes and seconds times
when adding the values! It may be easiest to convert all times to seconds.
Unix Time Command
The Unix Time command will provide some details on how long a program or command took to
execute. For example, if you have a program ./someProg then in the shell you can type:
ed-vm$ time ./someProg
The output (shown below) details how long the code took to run:
real 1m10.951s
user 0m2.390s
sys 0m1.705s
● Real time – Elapsed time from beginning to end of program (or wall clock time)
● CPU time – Divided into User time and System time
◦ User time – time used by the program itself and any library subroutines it calls
◦ System time – time used by the system calls invoked by the program (directly or indirectly)
At the terminal prompt, you can type man time to see the manual page for time.
Submission:
• All source files must assemble and execute on Ubuntu and assemble with yasm.
• Submit source files
◦ Submit a copy of the program source file via the on-line submission.
◦ Note, only the functions file (a11procs.asm) will be submitted.
◦ Timer script output (a11btimes.txt).
◦ Assignment #11B write up (write_up.txt).
• Once you submit, the system will score the project and provide feedback.
◦ If you do not get full score, you can (and should) correct and resubmit.
◦ You can re-submit an unlimited number of times before the due date/time.
• Late submissions will be accepted for a period of 24 hours after the due date/time for any given
assignment. Late submissions will be subject to a ~2% reduction in points per an hour late. If
you submit 1 minute – 1 hour late -2%, 1-2 hours late -4%, … , 23-24 hours late -50%. This
means after 24 hours late submissions will receive an automatic 0.
Program Header Block
All source files must include your name, section number, assignment, NSHE number, and program
description. The required format is as follows:
; Name:
; NSHE ID:
; Section:
; Description:
Failure to include your name in this format will result in a loss of up to 10%.
Scoring Rubric
Scoring will include functionality, code quality, and documentation. Below is a summary of the
scoring rubric for this assignment.
Criteria Weight Summary
Assemble – Failure to assemble will result in a score of 0.
Program Header 3% Must include header block in the required
format (see above).
General Comments 7% Must include an appropriate level of program
documentation.
Program Functionality
(and on-time)
90% Program must meet the functional
requirements as outlined in the assignment.
Must be submitted on time for full score.
