Ask MetaFilter questions tagged with profiling

No time like the present

Blazecock Pileon — Tue, 04 Mar 2008 23:24:33 -0800

I'm interested in aspects of benchmarking with the help of UNIX's time, specifically, what user, system and elapsed times correspond to, within the functional context of the system and the tested application. I have a very rough idea what the results of time point to in terms of CPU contention, with respect to the result of elapsed time, if elapsed is greater than the sum of user and system times.

• What does it mean that user makes non-system calls (what are those calls?)

• Likewise, what does it mean specifically that system makes system calls (what are those calls?)

Would I use user and system mean times to establish how to guide function profiling, within an application?

• What benchmarking results should I use as criteria for comparing one test result with another, all else the same?

For example, let's say I run sed -e 's/+/-/' inputdata on the same system, where different builds of sed have been compiled with different optimization flags and compilers.

• In this case, why would I choose the mean user time over mean system time as the criterium for comparing against like measurements of a "baseline" stock build of sed?

• Likewise, what are the caveats with choosing one measurement class over the other? (What are the downsides of using user time? system time? I suspect the answer to this will depend upon the calls made.)

If you have pointers to literature (other than the thousands of man pages on Google) I'd be appreciative of that advice, as well. Thanks in advance.

What are my rights when being pulled over by the police for no reason?

hcastro — Tue, 30 Oct 2007 10:13:57 -0800

What are my rights when being pulled over by the police for no reason? On two separate occasions, over the past 2 months, I've been pulled over by local police for no apparent reason. Both times they've asked for my license and registration, returned them to me after about 5-10 minutes, and let me go without any ticket/warning. This past week my mother was pulled over in the same manner (different car). She mentioned it to our neighbor, and he reported a similar incident.

We live in an area of Philadelphia, PA that isn't too good, but that shouldn't be an excuse. They should at least have a reason to pull me over before doing so. I haven't asked any of the officers to explain themselves, because I fear the Dave Chappelle scenario (cop sprinkles crack on you). Can anyone shed some light on what type of rights I have/what I can do about this? Should I write a letter to the mayor? Police commissioner?

Thanks for your help.

-- Just to clear up some potential racial profiling responses:

-My mother and I are Hispanic, but don't necessarily look it.
-My neighbor is African-American.

Hey man, is that a crowbar in your pocket or are you just glad to see me?

Anonymous — Mon, 27 Aug 2007 11:34:27 -0800

I'm Sikh, I'm going to SF, I'm (irrationally) scared... I'm 28, a UK citizen and, ostensibly Sikh. I wouldn't (in a million years) call myself a proper follower of my faith -- my beard is shaved BUT I do wear a modern style turban (kinda like this guy here). I'm traveling to SF in 2 weeks on work and I'll be there for 5 days or so. It'll be my first trip to the USA and in many, many ways I'm *really* looking forward to it.

However, given the current socio-political climate I find myself feeling intimidated thinking about walking around the USA looking the way I do -- and am afraid for my personal safety. I understand that part of this is complete irrational fear, but part of it is based on anecdotes from friends and family who have been there, as well as my own experiences in the UK.

I also understand that by-and-large SF is probably one of the most liberal, cosmopolitan cities in the USA and most people will probably have a rough idea of who I am and where I'm from. I'm just afraid of the uneducated buffoons. So I was wondering, any hints or tips on (1) how to behave (2) places to avoid and (3) generally make my trip more pleasant?

How do you calculate the burden a bit of PHP is likely to put on the server?

Tuwa — Fri, 24 Aug 2007 22:06:27 -0800

How do you calculate the burden a bit of code is likely to put on the server? Extra points for free and easily understood. I'm webmaster of a ~100 page site with every page containing a sidebar. The sidebar has buttons on it which either link to that page if you're not on it or put a CSS class on the text if you are.

I'm in process of updating and streamlining the site. I'd like to remove the sidebar to (a new file) sidebar.php and use an include on all the other pages so that any time the sidebar changes I can change and reupload only one file rather than 100.

I know this can be done in Javascript, but I'd rather not. I'd like an option that works for *every* visitor, not simply the ones visiting in a Javascript-capable browser with Javascript turned on.

The code I was thinking of was something like
$here = $_SERVER['PHP_SELF'];
if ($here == '/index.php')
print "Home";
else
print "Home";

It works, and I suspect it won't be a problem even though we have just a very basic hosting package and get about 5k page views a week. (The math: 5,000 page hits a week * 10 if/thens = 50k if/thens/week = 7153 if/thens a day = 297 an hour = 5 a minute = most likely not a problem.) But how do you know how much of that kind of access a host permits? At what point does it get their attention and/or ire?

Also, how do you calculate the burden of proposed code? Where does one go for that information? What do you do to make sure you're writing code that can handle a lot of traffic?

Tax Dollars at work?

Unregistered User — Fri, 21 Jul 2006 04:46:05 -0800

search: Can you help me find a citation? There was an article or post, possibly a pdf, that is a template used by our wonderful homeland security et al, to track and monitor would be terrorist's, one of these criteria's were certain flag signals for them. Much like shooting rubber bands at planes, there was a article I ran across recently, and unfortunately didn't link it, having to do with, for example, The Psychology of Cyberspace it profiled the "cyber terrorist", or some such; as I vaguely remember it described --with bullet points-- of a would be "terrorist", one example was, "anyone who spends more than 50 hours a week on the internet", among other ridiculous things, as set down by the FBI or some other alphabet agency. Can anyone help me find that citation? I would like to use it in a research paper I am working on.