cs161-list February 2003

cs161-list@lists.fas.harvard.edu

14 participants
42 discussions

by Alexandra (Sasha) Fedorova

The solution set for Assignment 1 has been released. It is posted in the "assignments" section of the course web site. -- Sasha

21 years, 2 months

Re: [cs161-list] how to fire up a user program from the menu

by dholland＠eecs.harvard.edu

> Is menu.c's other program option -s just a placeholder or does it > have run user program functionality? It calls userprog, but I > can't get it to run anything. I was hoping to see userprog in > action, before modifying it for fork and exec. I wanted to see how > the files are identified (path) so that I can add test programs and > run them once I get fork and exec to work. Any help you could > offer would be greatly appreciated. 's' is equivalent to 'p /bin/sh' ...or at least it should be. (Please make sure when you're done with asst2 that this is still true.) -- - David A. Holland / dholland(a)eecs.harvard.edu

21 years, 2 months

Solution set for A0

by Alexandra (Sasha) Fedorova

Solution set for Assignment 0 has been posted on the web site in the "assignments" section. Solution set for Assignment 1 is coming soon. -- Sasha

21 years, 2 months

reminder: no 6-8 OH today

by gwa

hi guys and gals: just a reminder that jonathan is out of town and won't be holding his 6-8 office hours tonight. sasha's mine and david's will take place as usual (barring any more "unusual" weather ;-) good luck with assignment two! -gwa-

21 years, 2 months

Note: SECTION TIME AND LOCATION CHANGE

by Alexandra (Sasha) Fedorova

Dear Students: Today's 7:30 PM section that is normally taught by Sasha Fedorova at 53 Church street has been rescheduled, because the Extension School building that we use for this section is closed today. The time and location for today's section are: When: Today, Tuesday, February 18th, 7PM Where: Maxwell-Dworkin, G-115, (33 Oxford Street). The change affects only this week's section. Starting from next week this section will be held as noted on the syllabus. (Don't let this change in schedule discourage your attendance - we will be covering some very important material that will help you get started with Assignemnt 2.) -- Sasha

21 years, 2 months

groups

by Jonathan Ledlie

Hi 161ers, Just letting you know that your animal groups now exist on FAS and that you should be able to chgrp your CVS repositories as shown in the assignment now. -jonathan

21 years, 3 months

goto, volatile, optimizations

by gwa

hello cs161ers: a few things in this email: 1) volatile somebody took me up on my offer to cook up compiler output showing the effect of declaring a variable volatile. an example of the difference in compile output when "volatile" is used (attached) (compiled with gcc -S -O2) 2) goto use it occured to me recently that it might be wise to try and reverse a bit of the "never ever ever use goto" conditioning that some of you received in cs50. in systems programming goto is frequently used for cleanup on error, as in the following example: ****************************** if (!(var1 = kmalloc())) { goto out1; } if (!(var2 = kmalloc())) { goto out2; } if (!(var3 = kmalloc())) { goto out3; } ... do something ... return successvalue; out3: kfree(var2); out2: kfree(var1); out1: return NULL; ****************************** pretty clean actually... we like this stuff. of course, you need to decide when this is appropriate. for a lot of kernel-level stuff, failure means BIG problems. if a kernel thread can't allocated a lock/sem/cv it probably is going to die and perhaps take the entire system with it so error checking as presented above is nice but probably unnecessary (just call panic). you can think more about preventing low memory situations in asst3. 3) optimization we had a few people approach us during asst1 who either wanted to or were in the midst of doing some pretty crazy optimizations. we don't want to discourage you from optimizing your code, but please keep the following in mind: * when you do your design, design clean interfaces to make later optimizations possible. * optimizations should not be attempted until all code that needs to be submitted has been written and THROROUGHLY tested. we like fast code, but we like correct code more. * think about the tradeoffs of optimization: how often is this piece of code going to be run? is it worth it to trade {speed, space} for {space, speed} and added complexity? are you going to able to understand this code two months later? we'll have more to say about optimizations later, but please feel free to approach the course staff for guidance if you want to attempt something cool... we'd love to hear about it. good luck on asst2. -gwa-

21 years, 3 months

Assignment 2 code-reading

by dholland＠eecs.harvard.edu

It has been observed that the question about userptr_t inadvertently got asked twice. It is both question #7 and #13. You don't need to repeat the answer twice. -- - David A. Holland / dholland(a)eecs.harvard.edu

21 years, 3 months

W6-8 OH

by Jonathan Ledlie

Hi cs161-ers, I will not be able to hold office hours this week on 2/19 from 6-8pm because I will be away at a conference in Berkeley. Sorry! -jonathan

21 years, 3 months

last-ditch try: NEED A PARTNER??

by Courtney Anne O'Keefe

hi there -- apologies for the mass email: I thought I'd give this one more shot... does anybody out there need a cs161 partner (and not already have one)?? if so, me too! - please email me!! :] cheers, courtney

21 years, 3 months

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cs161-list February 2003