# Search Results

• ### Optimizing a Parking Lot Problem. What algorithims should I use to fit the most amount of cars in th

What algorithms (brute force or not) would I use to put in as many cars (assume all cars are the same size) in a parking lot so that there is at least one exit (from the container) and a car cannot be blocked. Or can someone show me an example of this problem solved programmatically. The parking lot varies in shape would be nice but if you want to assume its some invariant shape that is fine. Another Edit: Assume that driving distance in the parking lot is not a factor (although it would be totally awesome if it was weighted factor to number of cars in lot). Another Edit: Assume 2 Dimensional (no cranes or driving over cars). Another Edit: You cannot move cars around once they are parked (its not a valet parking lot). I hope the question is specific enough now.

• ### R scatterplot overplotting color

##### - by rgeekay
So far I have this: qplot(df[[1]], as.numeric(rownames(df)), group=df[[2]], color=df[[2]], ylab="") I want to use different colors for the points in the 2 groups - perhaps a lighter shade for the what's in black now and a darker - say, red for what's in blue. Also, I want to use hexbin kind of thing for group=0 but not for group=1. I'm not able to get the syntax to get this working. In the current plot 0 is in black and 1 is in blue. Added: I worked on it some more, and by using factor and scale_colour_manual, I got the grey color for 0 and red for 1: > palette1 [1] "grey" "red" "blue" "violet" "black" fy=factor(y, labels=c('grey', 'red')) qplot(x, seq(1:length(x)),col=fy, ylab="") + geom_point() + scale_colour_manual(values=palette1) Pending questions are: How to first plot all the grey and then red on top (some of the red is now hidden because the grey is plotted over). How to apply the hexbin logic for group0 i.e. the grey points only and not for the red.

• ### Linux software RAID6: rebuild slow

##### - by Ole Tange
I am trying to find the bottleneck in the rebuilding of a software raid6. ## Pause rebuilding when measuring raw I/O performance # echo 1 > /proc/sys/dev/raid/speed_limit_min # echo 1 > /proc/sys/dev/raid/speed_limit_max ## Drop caches so that does not interfere with measuring # sync ; echo 3 | tee /proc/sys/vm/drop_caches >/dev/null # time parallel -j0 "dd if=/dev/{} bs=256k count=4000 | cat >/dev/null" ::: sdbd sdbc sdbf sdbm sdbl sdbk sdbe sdbj sdbh sdbg 4000+0 records in 4000+0 records out 1048576000 bytes (1.0 GB) copied, 7.30336 s, 144 MB/s [... similar for each disk ...] # time parallel -j0 "dd if=/dev/{} skip=15000000 bs=256k count=4000 | cat >/dev/null" ::: sdbd sdbc sdbf sdbm sdbl sdbk sdbe sdbj sdbh sdbg 4000+0 records in 4000+0 records out 1048576000 bytes (1.0 GB) copied, 12.7991 s, 81.9 MB/s [... similar for each disk ...] So we can read sequentially at 140 MB/s in the outer tracks and 82 MB/s in the inner tracks on all the drives simultaneously. Sequential write performance is similar. This would lead me to expect a rebuild speed of 82 MB/s or more. # echo 800000 > /proc/sys/dev/raid/speed_limit_min # echo 800000 > /proc/sys/dev/raid/speed_limit_max # cat /proc/mdstat md2 : active raid6 sdbd[10](S) sdbc[9] sdbf[0] sdbm[8] sdbl[7] sdbk[6] sdbe[11] sdbj[4] sdbi[3](F) sdbh[2] sdbg[1] 27349121408 blocks super 1.2 level 6, 128k chunk, algorithm 2 [9/8] [UUU_UUUUU] [=========>...........] recovery = 47.3% (1849905884/3907017344) finish=855.9min speed=40054K/sec But we only get 40 MB/s. And often this drops to 30 MB/s. # iostat -dkx 1 sdbc 0.00 8023.00 0.00 329.00 0.00 33408.00 203.09 0.70 2.12 1.06 34.80 sdbd 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 sdbe 13.00 0.00 8334.00 0.00 33388.00 0.00 8.01 0.65 0.08 0.06 47.20 sdbf 0.00 0.00 8348.00 0.00 33388.00 0.00 8.00 0.58 0.07 0.06 48.00 sdbg 16.00 0.00 8331.00 0.00 33388.00 0.00 8.02 0.71 0.09 0.06 48.80 sdbh 961.00 0.00 8314.00 0.00 37100.00 0.00 8.92 0.93 0.11 0.07 54.80 sdbj 70.00 0.00 8276.00 0.00 33384.00 0.00 8.07 0.78 0.10 0.06 48.40 sdbk 124.00 0.00 8221.00 0.00 33380.00 0.00 8.12 0.88 0.11 0.06 47.20 sdbl 83.00 0.00 8262.00 0.00 33380.00 0.00 8.08 0.96 0.12 0.06 47.60 sdbm 0.00 0.00 8344.00 0.00 33376.00 0.00 8.00 0.56 0.07 0.06 47.60 iostat says the disks are not 100% busy (but only 40-50%). This fits with the hypothesis that the max is around 80 MB/s. Since this is software raid the limiting factor could be CPU. top says: PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 38520 root 20 0 0 0 0 R 64 0.0 2947:50 md2_raid6 6117 root 20 0 0 0 0 D 53 0.0 473:25.96 md2_resync So md2_raid6 and md2_resync are clearly busy taking up 64% and 53% of a CPU respectively, but not near 100%. The chunk size (128k) of the RAID was chosen after measuring which chunksize gave the least CPU penalty. If this speed is normal: What is the limiting factor? Can I measure that? If this speed is not normal: How can I find the limiting factor? Can I change that?

• ### Bowser’s Weekend with the Kids [Video]

##### - by Asian Angel
Bowser decides to have his son Larry be a boss on one of the airships when he comes to spend the weekend with him. The question is can Larry be a tough enough boss for Mario to deal with or will things go horribly wrong for him? Bowser’s Weekend With The Kids [Dorkly] How to Banish Duplicate Photos with VisiPic How to Make Your Laptop Choose a Wired Connection Instead of Wireless HTG Explains: What Is Two-Factor Authentication and Should I Be Using It?

• ### Video Games from the Bad Guys’ Perspective [Video]

##### - by Jason Fitzpatrick
We’re so used to seeing video games from our perspective–the hero with the endless power ups and do-overs–but how does the video game world look from the perspective of the bad guys? Rather grim and confusing, as the video above highlights. [via Geekosystem] How to Banish Duplicate Photos with VisiPic How to Make Your Laptop Choose a Wired Connection Instead of Wireless HTG Explains: What Is Two-Factor Authentication and Should I Be Using It?

• ### Super Mario – 3D Chalk Art (Time Lapse) [Video]

##### - by Asian Angel
This awesome time-lapse video lets you watch artist Chris Carlson create a fantastic 3D chalk art rendition of Mario on a sidewalk setting. There is certainly a lot more work and precision to it than some people may believe… Super Mario – 3D Chalk Art (Time Lapse) [via Neatorama] How to Banish Duplicate Photos with VisiPic How to Make Your Laptop Choose a Wired Connection Instead of Wireless HTG Explains: What Is Two-Factor Authentication and Should I Be Using It?

• ### Chuck Jones Shows How to Draw Bugs Bunny [Video]

##### - by Asian Angel
Is drawing one of your passions and/or hobbies? Are you a fan of the classic Bugs Bunny cartoons? Then you will certainly enjoy this delightful video where Chuck Jones shows you how to draw Bugs Bunny! Chuck Jones shows how to draw Bugs Bunny [via Neatorama] How to Make Your Laptop Choose a Wired Connection Instead of Wireless HTG Explains: What Is Two-Factor Authentication and Should I Be Using It? HTG Explains: What Is Windows RT and What Does It Mean To Me?

• ### An XEvent a Day (12 of 31) – Using the Extended Events SSMS Addin

##### - by Jonathan Kehayias
The lack of SSMS support for Extended Events, coupled with the fact that a number of the existing Events in SQL Trace were not implemented in SQL Server 2008, has no doubt been a key factor in its slow adoption rate. Since the release of SQL Server Denali CTP1, I have already seen a number of blog posts that talk about the introduction of Extended Events in SQL Server, because there is now a stub for it inside of SSMS. Don’t get excited yet, the functionality in CTP1 is very limited at this point,...(read more)

• ### MDM 2010 Summit in San Francisco

##### - by Tony Ouk
Since 2006, the MDM Global Summit Series has brought master data expertise to more than 5,000 delegates worldwide. The Series is designed to reinforce the importance of data governance as a key factor to your MDM program's success while providing real-world experience and all-in-one access to solutions providers. Come join us June 2-3, 2010 at the Hyatt Regency in San Francisco.  For more information including registration details, visit the MDM Global Summit Series website.

• ### The Science of Brain Freezes [Video]

##### - by Jason Fitzpatrick
For many readers summer is in full swing and icy treats are abundant; check out this video to see the science behind how a frozen treat can bring on the dreaded “brain freeze”. [via Boing Boing] How to Make Your Laptop Choose a Wired Connection Instead of Wireless HTG Explains: What Is Two-Factor Authentication and Should I Be Using It? HTG Explains: What Is Windows RT and What Does It Mean To Me?

• ### Using Flash in Your Website Design

Many people like a wow factor in their website design and something that gives that is flash. Flash is used to created rich internet applications such as animation, video, audio and the interactivity of images.

• ### 7 Cool Firefox Ad-ons

<b>The Linux Box:</b> "One of the coolest things about Firefox is its extensibility. Everyone has their collection of favorite Firefox add-ons and I thought I would share mine. Some provide improved organization, some have a certain "WOW!" factor, and others just look pretty."

• ### Site Speed - 5 Quick Reasons You Need Speed

Google have introduced a new ranking factor called 'site speed' into their search algorithm. From now on, the length of time it takes for your web pages to load will influence your search engine positioning on Google.com. In other words fast websites will be favored over slow websites in its search results.

• ### The Best Websites for Free Online Courses, Certificates, Degrees, and Educational Resources

##### - by Lori Kaufman
Have you thought about expanding your knowledge by taking some courses? There are several colleges and other sites that offer free online courses, certificate programs, some degree programs, and education resources for teachers and professors. How to Banish Duplicate Photos with VisiPic How to Make Your Laptop Choose a Wired Connection Instead of Wireless HTG Explains: What Is Two-Factor Authentication and Should I Be Using It?

• ### Nostalgia Lane: Steve Jobs Introduces the iPhone in 2007 [Classic Video]

##### - by Asian Angel
With the five year anniversary of the iPhone approaching, here is a look back at when it all started with this classic introductory presentation by Steve Jobs. Steve Jobs introduces iPhone in 2007 [YouTube] How to Banish Duplicate Photos with VisiPic How to Make Your Laptop Choose a Wired Connection Instead of Wireless HTG Explains: What Is Two-Factor Authentication and Should I Be Using It?

• ### Python Forgiveness vs. Permission and Duck Typing

##### - by darkfeline
In Python, I often hear that it is better to "beg forgiveness" (exception catching) instead of "ask permission" (type/condition checking). In regards to enforcing duck typing in Python, is this try: x = foo.bar except AttributeError: pass else: do(x) better or worse than if hasattr(foo, "bar"): do(foo.bar) else: pass in terms of performance, readability, "pythonic", or some other important factor?

• ### Mathematica Programming Language&ndash;An Introduction

##### - by JoshReuben
The Mathematica http://www.wolfram.com/mathematica/ programming model consists of a kernel computation engine (or grid of such engines) and a front-end of notebook instances that communicate with the kernel throughout a session. The programming model of Mathematica is incredibly rich & powerful – besides numeric calculations, it supports symbols (eg Pi, I, E) and control flow logic.   obviously I could use this as a simple calculator: 5 * 10 --> 50 but this language is much more than that!   for example, I could use control flow logic & setup a simple infinite loop: x=1; While [x>0, x=x,x+1] Different brackets have different purposes: square brackets for function arguments:  Cos[x] round brackets for grouping: (1+2)*3 curly brackets for lists: {1,2,3,4} The power of Mathematica (as opposed to say Matlab) is that it gives exact symbolic answers instead of a rounded numeric approximation (unless you request it):   Mathematica lets you define scoped variables (symbols): a=1; b=2; c=a+b --> 5 these variables can contain symbolic values – you can think of these as partially computed functions:   use Clear[x] or Remove[x] to zero or dereference a variable.   To compute a numerical approximation to n significant digits (default n=6), use N[x,n] or the //N prefix: Pi //N -->3.14159 N[Pi,50] --> 3.1415926535897932384626433832795028841971693993751 The kernel uses % to reference the lastcalculation result, %% the 2nd last, %%% the 3rd last etc –> clearer statements: eg instead of: Sqrt[Pi+Sqrt[Sqrt[Pi+Sqrt[Pi]]] do: Sqrt[Pi]; Sqrt[Pi+%]; Sqrt[Pi+%] The help system supports wildcards, so I can search for functions like so: ?Inv* Mathematica supports some very powerful programming constructs and a rich function library that allow you to do things that you would have to write allot of code for in a language like C++.   the Factor function – factorization: Factor[x^3 – 6*x^2 +11x – 6] --> (-3+x) (-2+x) (-1+x)   the Solve function – find the roots of an equation: Solve[x^3 – 2x + 1 == 0] -->   the Expand function – express (1+x)^10 in polynomial form: Expand[(1+x)^10] --> 1+10x+45x^2+120x^3+210x^4+252x^5+210x^6+120x^7+45x^8+10x^9+x^10 the Prime function – what is the 1000th prime? Prime[1000] -->7919 Mathematica also has some powerful graphics capabilities:   the Plot function – plot the graph of y=Sin x in a single period: Plot[Sin[x], {x,0,2*Pi}] you can also plot 3D surfaces of functions using Plot3D function

• ### Efficient SQL Server Indexing by Design

Having a good set of indexes on your SQL Server database is critical to performance. Efficient indexes don't happen by accident; they are designed to be efficient. Greg Larsen discusses whether primary keys should be clustered, when to use filtered indexes and what to consider when using the Fill Factor.

• ### Small Business and Organic SEO - A Win Win Situation

Small business owners have to run on tiny budgets and that becomes constraint for effective publicity. The online marketing performance also suffers due to this crucial factor. The remedy lies in organic SEO, which efficiently works for the website of small business and supports the placement in higher rankings in search results. It is a win win situation for small business owners.

• ### The clock hands of the buffer cache

Over a leisurely beer at our local pub, the Waggon and Horses, Phil Factor was holding forth on the esoteric, but strangely poetic, language of SQL Server internals, riddled as it is with 'sleeping threads', 'stolen pages', and 'memory sweeps'. Suddenly, however, my attention was grabbed by his mention of the 'clock hands of the buffer cache'....Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

With the latest announcement that page loading times would soon be a factor in site ranking, it is now more important than ever to make sure that your website loads quickly, efficiently and doesn't hang on various problems that make not only Google but the visitor waiting for ever. By looking at a few things, you can really help to increase your page load times, keeping the engines and your visitors happy.

• ### The Best How-To Geek Articles for June 2012

##### - by Asian Angel
This past month we covered topics such as why you only have to wipe a disk once to erase it, what RSS is and how you can benefit from using it, how websites are tracking you online, and more. Join us as we look back at the best articles for June. How to Banish Duplicate Photos with VisiPic How to Make Your Laptop Choose a Wired Connection Instead of Wireless HTG Explains: What Is Two-Factor Authentication and Should I Be Using It?

• ### How to Get Found on Search Engines

Getting found on search engines is a critical factor to businesses because the majority of consumers are looking using these sites to find answers. If you do not have a high ranking, you run the risk of never getting found on a medium that is growing in popularity by the minute.