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• Arbitrary-precision random numbers in C: generation for Monte Carlo simulation without atmospheric n

  - by Yktula

  I know that there are other questions similar to this one, however the following question pertains to arbitrary-precision random number generation in C for use in Monte Carlo simulation. How can we generate good quality arbitrary-precision random numbers in C, when atmospheric noise isn't always available, without relying on disk i/o or network access that would create bottlenecks? libgmp is capable of generating random numbers, but, like other implementations of pseudo-random number generators, it requires a seed. As the manual mentions, "the system time is quite easy to guess, so if unpredictability is required then it should definitely not be the only source for the seed value." Is there a portable/ported library for generating random numbers, or seeds for random numbers? The libgmp also mentions that "On some systems there's a special device /dev/random which provides random data better suited for use as a seed." However, /dev/random and /dev/urandom can only be used on *nix systems.

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• Removing the image from an IKImageView

  - by Brian Postow

  I have an IKImageView that is coming up effectively un-initialized. This is happening effectively in an error-state (The user is unregistered) so I haven't had a chance to put an image in it yet. In 10.6, this comes up fine, with a black rectangle. In 10.5, however, it comes up with garbage. some rectangles of noise, some rectangles of copies of the desktop, etc. I've tried setting the ZoomFactor to 0.0, I've tried setting the image to nil, but it appears that the problem is beyond that. any ideas? (My next kludge is going to be to ship tiny blank image with the app, and try to get it to load that... but that's kind of silly)

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• Kink detection in drawn polylines

  - by David Rutten

  Users can sketch in my app using a very simple tool (move mouse while holding LMB). This results in a series of mousemove events and I record the cursor location at each event. The resulting polyline curve tends to be rather dense, with recorded points almost every other pixel. I'd like to smooth this pixelated polyline, but I don't want to smooth intended kinks. So how do I figure out where the kinks are? The image shows the recorded trail (red pixels) and the 'implied' shape as a human would understand it. People tend to slow down near corners, so there is usually even more noise here than on the straight bits.

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• Novel fitness measure for evolutionary image matching simulation

  - by Nick Johnson

  I'm sure many people have already seen demos of using genetic algorithms to generate an image that matches a sample image. You start off with noise, and gradually it comes to resemble the target image more and more closely, until you have a more-or-less exact duplicate. All of the examples I've seen, however, use a fairly straightforward pixel-by-pixel comparison, resulting in a fairly predictable 'fade in' of the final image. What I'm looking for is something more novel: A fitness measure that comes closer to what we see as 'similar' than the naive approach. I don't have a specific result in mind - I'm just looking for something more 'interesting' than the default. Suggestions?

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• GpsSatellite.getSnr() - What is the value range?

  - by rflexor

  I'm building a Sat-View that draws a small bar-chart for available satellites and their signal strength (or better: their signal-to-noise-ratio / SNR). The javadoc doesn't say what value-range to expect for the SNR. The NMEA-Standard says 0-99, but even in best conditions my G1 doesn't reach that value. I also read that different manufacturers use different value-ranges for the SNR, so is that true for android-devices, too? Or is there a unified value range on that plattform and if so, what is it? The lack of information in the docs leads me to suspect I just get the "raw" SNR from the driver, in which case I'd like to know: What do you think is the best approach to visualize that unknown value-range in a bar-chart?

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• Video Synthesis - Making waves, patterns, gradients...

  - by Nathan

  I'm writing a program to generate some wild visuals. So far I can paint each pixel with a random blue value: for (y = 0; y < YMAX; y++) { for (x = 0; x < XMAX; x++) { b = rand() % 255; setPixelColor(x,y,r,g,b); } } I'd like to do more than just make blue noise, but I'm not sure where to start (Google isn't helping me much today), so it would be great if you could share anything you know on the subject or some links to related resources.

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• asp.net web deployment

  - by CliffC

  i have successful created asp.net web deployment project under visual studio 2008 and everything works fine. However there is a new requirement from my user where they want to browse the location to install the web application instead of using the default install location. Is there anyway to achieve this ? or do i need to use some third party deployment tools? i have tried the sample transformation file on http://www.codeproject.com/KB/install/ChangeVDirWebSetupProject.aspx?fid=295594&fr=1&df=90&mpp=25&noise=3&sort=Position&view=Quick#xx0xx but it only seems to work under vs2005 thanks

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• Do you have any tips for comments code to keep them in step with the code?

  - by Rob Wells

  G'day, I've read both of Steve McConnell's excellent Code Complete books "Code Complete" and "Code Complete 2" and was wondering if people have any other suggestions for commenting code. My commenting mantra could be summed up by the basic idea of expressing "what the code below cannot say". While enjoying this interesting blog post by Jeff about commenting I was still left wondering "When coding, when do you feel a comment is required?" Edit: Oops. Seems to be a duplicate of this question http://stackoverflow.com/questions/121945/how-do-you-like-your-comments so sorry for the noise. Thanks to my, seemingly, SO shadow for pointing it out - wouldn't have thought I was that interesting. Now off to read the original post and see if it is relevant. Edit: I meant to emphasise the best appraoch to ensure that your comments will stay in step with the code. Maybe expressing an intent rather than the mechansim for instance.

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• How do I indicate success and failure with colour?

  - by Steve McLeod

  I need to make a Java component that turns the background a certain colour when a process passed, and another colour when the process failed. My first thought was: green for success, red for failure. But then I read that 10% of males can't differentiate between these two colours. What would be a better combination of colours? (For the nitpickers: yes, I know that colour alone doesn't suffice, that text, shape, and noise can also be used. Nevertheless I am asking about the appropriate use of colour.)

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• Video Synthesis - Making waves, pattern, gradients...

  - by Nathan

  I'm writing a program to generate some trippy visuals. My code paints each pixel with a random blue value which loops at 0.04 second intervals. for (y = 0; y < 5.5; y += 0.2) { for (x = 0; x < 7.5; x += 0.2) { b = rand() / ((double) RAND_MAX); setPixelColor(x,y,r,g,b); } } I'd like to do more than just make blue noise... but my maths is a bit rusty, and Google isn't helping me much today, so it would be great if you could share anything you know about making waves, patterns, gradient animations, etc or links to such material.

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• Changing the x-axis of seqlogo figures in matlab

  - by JudoWill

  I'm making a large number of seqlogos programatically. They are hundreds of columns wide and so running a seqlogo normally creates letters that are too thin to see. I've noticed that I only care about a few of these columns (not necessarily consecutive columns) ... most are noise but some are highly conserved. I use something like this snippet: conserve_cell = seqlogo(wide_seqs, 'displaylogo', false); high_bit_cols = any(conserve_cell{2}>1.0,1); [~, handle] = seqlogo(wide_seqs(:,high_bit_cols )); Although when I do this I lose the information about which columns the data came from. Normally I would just change the x-axis of the seqlogo. However, seqlogo's are some sort of crazy java-based object and calls like: set(handle, 'xticklabel', num2str(find(high_bit_cols))) don't work. Any help would be greatly appreciated. Thanks, Will

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• casting unused return values to void

  - by markh44

  int fn(); void whatever() { (void) fn(); } Is there any reason for casting an unused return value to void, or am I right in thinking it's a complete waste of time? Follow up: Well that seems pretty comprehensive. I suppose it's better than commenting an unused return value since self documenting code is better than comments. Personally, I'll turn these warnings off since it's unnecessary noise. I'll eat my words if a bug escapes because of it...

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• Matlab: Analysis of signal

  - by Mateusz

  Hi, I have a problem with this task: For free route perform frequency analysis and give parametrs of each signal component: time of beginning and ending of each component beginning and ending frequency amplitude (in time domain) in the beginning and end of each signal's component level of noise in dB Assume, that, the parametrs of each component like amplitude, frequency is changing lineary in time. Frequency of sampling is 1000Hz For example I have signal like this: Nx=64; fs=1000; t=1/fs*(0:Nx-1); %========================== A1=1; A2=4; f1=500; f2=1000; x1=A1*cos(2*pi*f1*t); x2=A2*sin(2*pi*f2*t); %========================== x=x1+x2;

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• ffmpeg: converting an avi to a reduced, shareable flv/mp4...

  - by meder

  I recently followed a guide and recompiled my ffmpeg so x264 is enabled. I used some generic settings to convert my 700 MB avi file to a mp4 file, the result was a 407MB mp4 file. The original avi file's settings: Codec: DX50 Resolution: 704x304 Frame rate: 23.976023 Stream 1 Codec: mpga Type: Audio Channels: 2 Sample rate: 48000 Hz Bitrate 179 kb/s Command I used: ffmpeg -i input.avi -acodec libfaac -ab 128k -ac 2 -vcodec libx264 -vpre hq -crf 22 -threads 0 output.mp4 The settings of the output file (output.mp4): Codec: avc1 Resolution: 704x304 Display resolution: 704x304 Frame rate: 11.988011 Stream 1 Codec: mp4a Type: Audio Channels: 2 Sample Rate: 48000 Hz Bits per sample: 16 Bitrate: 1536 kb/s The quality of the output mp4 is pretty nice, it seems as if it's pretty much the same as the original source. However, I'm trying to reduce the filesize and I'm not really sure whether I should go with an flv format or keep it mp4. The advantage the flv would have obviously is that it would be playable with a flash player ( I have come across some swf players which take a flash parameter to play an flv file ).. but maybe I could use the video element, as I'm only going to be displaying this video privately so I don't have to worry about supporting legacy browsers such as IE. Can someone recommend some settings to specify in order for the filesize to be around ~100-150MB or so? I don't mind a reduction in quality, nor do I mind resizing it - I was going to do it initially but I wasn't sure what the guidelines were ( if any ) for dealing with resolution.. since this video's is 704x304 would it still be ok if I forced it into one that isn't perfectly fit for the aspect ratio? I have no clue about that part. I realize that I could have probably specified 28 instead of 22 for the CRF, I'm not sure if I should do that as opposed to maybe specifying smaller resolution, which might make it smaller as well?

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• How do I write to a file and print to a terminal cuncurrently in Unix?

  - by bias

  I have a little bash function to log my Macports outputs to a file (since installs often spew little tidbits that are easy to lose in terminal noise), then I just cat the file to the terminal: function porti { command sudo port install $@ >> $1.log 2>&1; cat $1.log } Is there a way to do this concurrently? I don't care about it being in Bash, that's just how I started it. BTW I pass $@ to install but only $1 for the file name so that I can do something like: porti git-gore +bash_completion and only get the file git-core.log however someone else might prefer to include variants in the file name ...

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• Bad temperature sensors on Foxconn motherboard?

  - by Gawain

  I have a system with a Foxconn V400 series motherboard and AMD Athlon 3000+ processor. Ever since I got it a few years ago the fans (particularly the CPU fan) have been really loud. So recently I installed SpeedFan to see why they were running so fast. SpeedFan reported the CPU temperature to be 32C, and one motherboard sensor at about 26C. But the other two motherboard sensors were reporting 78C and 64C respectively. Naturally the fans were both maxed out because of this, with the CPU fan at 5800rpm and the case fan at 2400rpm. I opened the case and everything inside was literally cool to the touch, with the exception of the CPU heatsink which was slightly warm, but nowhere near 78C. It seems like the temperature sensors are either defective or being read incorrectly. Is there some way I can decrease my fan noise without risking damage to my processor? Some way to ignore those two temp sensors? Any help would be greatly appreciated.

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• Interpreting Search Results

  - by Simon

  Hi all, I am tasked with writing a program that, given a search term and the HTML source of a page representing search results of some unknown search engine (it can really be anything, a blog, a shop, Google, eBay, ...), needs to build a data structure of the results containing "what's in the results": a title for earch result, the "details" link, the position within the results etc. It is not known whether the results page contains any of the data at all, and whether there are any search results. The goal is to feed the data structure into another program that extracts meaning. What I am looking for is not BeautifulSoup or a RegExp but rather some clever ideas or algorithms on how to interpret the HTML source. What do I do to find out what part of the page constitutes a single result item? How do I filter the markup noise to extract the important bits? What would you do? Pointers to fields of research covering what I try to to are aly greatly appreciated. Thanks, Simon

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• Using PIG with Hadoop, how do I regex match parts of text with an unknown number of groups?

  - by lmonson

  I'm using Amazon's elastic map reduce. I have log files that look something like this random text foo="1" more random text foo="2" more text noise foo="1" blah blah blah foo="1" blah blah foo="3" blah blah foo="4" ... How can I write a pig expression to pick out all the numbers in the 'foo' expressions? I prefer tuples that look something like this: (1,2) (1) (1,3,4) I've tried the following: TUPLES = foreach LINES generate FLATTEN(EXTRACT(line,'foo="([0-9]+)"')); But this yields only the first match in each line: (1) (1) (1)

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• Do you have any tips for comments to keep them in step with the code? [closed]

  - by Rob Wells

  Possible Duplicate: How do you like your comments? G'day, I've read both of Steve McConnell's excellent Code Complete books "Code Complete" and "Code Complete 2" and was wondering if people have any other suggestions for commenting code. My commenting mantra could be summed up by the basic idea of expressing "what the code below cannot say". While enjoying this interesting blog post by Jeff about commenting I was still left wondering "When coding, when do you feel a comment is required?" Edit: Oops. Seems to be a duplicate of this question http://stackoverflow.com/questions/121945/how-do-you-like-your-comments so sorry for the noise. Thanks to my, seemingly, SO shadow for pointing it out - wouldn't have thought I was that interesting. Now off to read the original post and see if it is relevant. Edit: I meant to emphasise the best appraoch to ensure that your comments will stay in step with the code. Maybe expressing an intent rather than the mechansim for instance.

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• Problem with Full text Searching

  - by devendra

  I am searching in resumes weather the word is exist or not i am using the below query Case1: select top(10) c_resume_text from sntbl_candidates where contains(c_resume_text,'"a/dm"') in the above example only it is not working properly .It showing resumes even though there is no text like that. In Messages i am getting the following message. Informational: The full-text search condition contained noise word(s). if i try with Case 2: select top(10) c_resume_text from sntbl_candidates where contains(c_resume_text,'"a/d') i am getting proper results in case 2 can any one suggest me what to do. Thanks

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• Redundancy algorithm for reading noisy bitstream

  - by Tedd Hansen

  I'm reading a lossy bit stream and I need a way to recover as much usable data as possible. There can be 1's in place of 0's and 0's in palce of 1's, but accuracy is probably over 80%. A bonus would be if the algorithm could compensate for missing/too many bits as well. The source I'm reading from is analogue with noise (microphone via FFT), and the read timing could vary depending on computer speed. I remember reading about algorithms used in CD-ROM's doing this in 3? layers, so I'm guessing using several layers is a good option. I don't remember the details though, so if anyone can share some ideas that would be great! :) Edit: Added sample data Best case data: in: 0000010101000010110100101101100111000000100100101101100111000000100100001100000010000101110101001101100111000101110000001001111011001100110000001001100111011110110101011100111011000100110000001000010111 out: 0010101000010110100101101100111000000100100101101100111000000100100001100000010000101110101001101100111000101110000001001111011001100110000001001100111011110110101011100111011000100110000001000010111011 Bade case (timing is off, samples are missing): out: 00101010000101101001011011001110000001001001011011001110000001001000011000000100001011101010011011001 in: 00111101001011111110010010111111011110000010010000111000011101001101111110000110111011110111111111101 Edit2: I am able to controll the data being sent. Currently attempting to implement simple XOR checking (though it won't be enough).

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• Can enabling a RAID controller's writeback cache harm overall performance?

  - by Nathan O'Sullivan

  I have an 8 drive RAID 10 setup connected to an Adaptec 5805Z, running Centos 5.5 and deadline scheduler. A basic dd read test shows 400mb/sec, and a basic dd write test shows about the same. When I run the two simultaneously, I see the read speed drop to ~5mb/sec while the write speed stays at more or less the same 400mb/sec. The output of iostat -x as you would expect, shows that very few read transactions are being executed while the disk is bombarded with writes. If i turn the controller's writeback cache off, I dont see a 50:50 split but I do see a marked improvement, somewhere around 100mb/s reads and 300mb/s writes. I've also found if I lower the nr_requests setting on the drive's queue (somewhere around 8 seems optimal) I can end up with 150mb/sec reads and 150mb/sec writes; ie. a reduction in total throughput but certainly more suitable for my workload. Is this a real phenomenon? Or is my synthetic test too simplistic? The reason this could happen seems clear enough, when the scheduler switches from reads to writes, it can run heaps of write requests because they all just land in the controllers cache but must be carried out at some point. I would guess the actual disk writes are occuring when the scheduler starts trying to perform reads again, resulting in very few read requests being executed. This seems a reasonable explanation, but it also seems like a massive drawback to using writeback cache on an system with non-trivial write loads. I've been searching for discussions around this all afternoon and found nothing. What am I missing?

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• Which upgrade path for disk IO bound postgres server?

  - by user41679

  Hi all, We currently have a Sun x4270 with 2xquad core Xeon Nehalmen 2.93ghz cores (16 threads), 72 gig of ram and 16 x 10k SAS disks split between the os raid 1, a partition for the Write Ahead Logs which is raid 10 and a partition for the database tables and indexes which is also raid 10, all xfs. I'm currently evaluating which path to go down in terms of upgrades. We'll be sharding the DB at some point soon, but for now I need to focus on hardware upgrades specifically. The machine is not CPU or memory bound at all at the moment, just IOWait is become an issue. The machine is mostly write access as we have a heavy caching layer. We're seeing about 300 write IOPS average on both the database partitions. We don't have any additional storage infrastructure like a Fiber Channel or ISCSI network. Budget isn't too much of a concern, something inline with the size of this server (i.e no $1m IBM machines) Space is ok on the DB side of things, we're running out obviously but there's also some reduction we can do. Additional space would be good though. My current thoughts are either: * ISCSI SAN, possible with 10Gbit network that has solid state acceleration. * FusionIO card / Sun F20 card (will the FusionIO card work in the Sun box? * DAS shelf (something like this http://www.broadberry.co.uk/das-direct-attached-storage-servers/cyberstore-224s-das) which a combination of 15k sas disks and some Intel X25-E drives for DB indexes etc) what would I need to put in the x4270 to add a DAS shelf? I think it's a SAS HBA card, do I have to use Sun's own card or will any PCI Express card work? Anything else??? what would you guys do from your experience? I appreciate it's a lot of questions, but I haven't expanded a DB machine for a number of years and the landscape has changed dramatically since then! Any advice or feedback would be very much appreciated. Let me know if there's anything else I can clarify. Thanks in advance!

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• What Windows editor has CORRECT EOL whitespace handling?

  - by blueshift

  I'm looking for a Windows text editor for programming that handles EOL whitespace CORRECTLY, which for my idea of correct means: Strip all EOL whitespace on save, EXCEPT on lines that I haven't edited. This is to minimise the amount of EOL whitespace evil in my world, but not pollute SCM diff/blame with whitespace-only fixes (I have to deal with old / other people's code). I have played with TextPad, Notepad++, Kodomo Edit and Programmer's Notepad 2, and found all of them lacking. Also: I don't get along with vi, and I am unsure about Emacs on Windows. @Matti Virkkunen: I could mess with diff, but I want to fix the problem, not the symptoms. Fixing diff means all my, others, and server side diff tools need to be fixed, and doesn't fix space/noise/hash change issues in SCM. Example pet hate using that system: "update" tells me a file has changed. Diff shows no changes.

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• matlab fit exp2

  - by HelloWorld

  I'm unsuccessfully looking for documentation of fit function using exp2 (sum of 2 exponents). How to operate the function is clear: [curve, gof] = fit(x, y,'exp2'); But since there are multiple ways to fit a sum of exponents I'm trying to find out what algorithm is used. Particularly what happens when I'm fitting one exponent (the raw data) with a bit of noise, how the exponents are spread. I've simulated several cases, and it seems that it "drops" all the weight on the second set of coefficients, but row data analysis often shows different behavior. Does anyone have suggestions of documentation?

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