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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:
