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Search found 1451 results on 59 pages for 'theory'.

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• Which tool should I use for finding out my memory allocation in Perl?

  - by Colin Newell

  I've slurped in a big file using File::Slurp but given the size of the file I can see that I must have it in memory twice or perhaps it's getting inflated by being turned into 16 bit unicode. How can I best diagnose that sort of a problem in Perl? The file I pulled in is 800mb in size and my perl process that's analysing that data has roughly 1.6gb allocated at runtime. I realise that I may be wrong about my reason for the problem but I'm not sure the most efficient way to prove/disprove my theory.

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• mysql left join

  - by user1019538

  I have two table one is index and another is the price structure as under table : index : column : trandate ,indexcode Table : price : Column: trandate,symbol,price i want to know the missing price. I issue the query select i.trandate,i.indexcode,p.trandate,p.price from index i left join price p on i.trandate = p.trandate where p.symbol='ABC' and indexcode="New" the above query does not show the null date even though various price in missing in price table. Only reason i understand is that the index table does not have the symbol field that's why...but as per theory if you want to show all the rows of one table and only the match value of another table then use the left or right join query...please anybody can help

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• Less Mathematical Approaches to Machine Learning?

  - by Ed

  Out of curiosity, I've been reading up a bit on the field of Machine Learning, and I'm surprised at the amount of computation and mathematics involved. One book I'm reading through uses advanced concepts such as Ring Theory and PDEs (note: the only thing I know about PDEs is that they use that funny looking character). This strikes me as odd considering that mathematics itself is a hard thing to "learn." Are there any branches of Machine Learning that use different approaches? I would think that a approaches relying more on logic, memory, construction of unfounded assumptions, and over-generalizations would be a better way to go, since that seems more like the way animals think. Animals don't (explicitly) calculate probabilities and statistics; at least as far as I know.

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• Best way to track impressions/clicks in a bespoke advertisement system?

  - by Martin Bean

  I've been asked to create a bespoke advertisement system despite suggesting open source alternatives such as OpenX and DoubleClick for Publishers (the former Google Ad Manager). I've got the basics of the system set up, i.e. uploading creatives, creating positions and a mechanism to place creatives within positions; however, the area I'm stuck with is impression and click tracking. At the moment an impression and click is stored with the creative, but this then means impressions/clicks can't be queried. For example, we can't find how many impressions were in position x between date y and date z. How would I go about storing that kind of data? My theory was store the creative ID, position ID and timestamp in a database table, but given the amount of traffic the site has this would produce a very large database very quickly. If any one could give me a pointer or two, that would be great.

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• Can jQuery perform a compound select against the top level only? (a.k.a. "How to avoid chaining chil

  - by harpo

  Basically, is there a way to write a.children('.outer').children('.inner') without the intermediate selector? I can't write $('.outer > .inner', a) because I don't want to do full-depth search against a — I know that the .outer elements are immediate children of a. It's partly a matter of "elegance", but partly because I'm trying to avoid "throwaway" element sets. Yes, jQuery may in effect do the same thing, but it has a better chance of optimizing (at least in theory), when it knows the full query's intent.

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• Grails: Duplicates & unique constraint validation

  - by rukoche

  OK here is stripped down version of what I have in my app Artist domain: class Artist { String name Date lastMined def artistService static transients = ['artistService'] static hasMany = [events: Event] static constraints = { name(unique: true) lastMined(nullable: true) } def mine() { artistService.mine(this) } } Event domain: class Event { String name String details String country String town String place String url String date static belongsTo = [Artist] static hasMany = [artists: Artist] static constraints = { name(unique: true) url(unique: true) } } ArtistService: class ArtistService { def results = [ [ name:"name", details:"details", country:"country", town:"town", place:"place", url:"url", date:"date" ] ] def mine(Artist artist) { results << results[0] // now we have a duplicate results.each { def event = new Event(it) if (event.validate()) { if (artist.events.find{ it.name == event.name }) { log.info "grrr! valid duplicate name: ${event.name}" } artist.addToEvents(event) } } artist.lastMined = new Date() if (artist.events) { artist.save(flush: true) } } } In theory event.validate() should return false and event will not be added to artist, but it doesn't.. which results in DB exception on artist.save() Although I noticed that if duplicate event is persisted first everything works as intended. Is it bug or feature? :P

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• Managed HttpListener vs C++ Network Lib - Requires admin rights?

  - by Max

  So, I have noticed that starting an HttpListener is considered impolite according to Win 7. I cannot do so without administrative rights without adding myself to some URL reservation list. In theory, this is alright, but I'd like to make my program as little invasive as possible. My main other alternative is something like the c++ Network Library, which utilizes boost. This is probably not as simple as a HttpListener though. Will this circumvent the admin rights requirement for listening to some HTTP url? How does windows handle http listening? Right now I'm just listening to http://+:xxxx/url, I guess it's fully possible to just create a Socket listening at port xxxx and provide my own/third party http implementation?

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• how to find out how much application memory django process is (or will be) taking?

  - by photographer

  There are different "Application memory" options (like 80MB...200MB) in django-friendly hosting called webfaction and I'm confused deciding which one I should buy. Could someone please walk me through the ideas on how to figure out how much memory my project might require (excluding operating system, the main apache server and the database servers memory requirements)? I understand in theory I'll need to perform some kind of load testing, but thought there might be ways to calculate that in advance with some simple/relatively easy understandable approach. I don't know how hard they enforce application memory usage limit, and another question is: what will happen if more users came to the site and more threads started than what I expected? Will the application crash? Or will delays just become uncomfortable? And - no, application is not ready yet (I can't measure anything right now). Development environment if it matters is Winodows 7, 64-bit. Hosting itself is some kind of Linux I think. (Sorry if it's not a stackoverflow question.)

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• OO C++ - Virtual Methods

  - by Phorce

  Just a really quick question here. I'm using virtual functions to read in from a text file. Now, it's virtual because in one aspect I want the values to be normalised, and, in the other respect I don't want them to be normalised. I have tried to do this: bool readwav(string theFile, 'native'); So in theory, if the 'native' is used, this method should be called, however, if 'double' is called then a different version of the method is called. Same for if the value is empty, it should just perform the native option. First question, why doesn't the declaration above work? Also, is this the best route to go down? Or, would it be better to have just one class method that switches between the options. Thanks :)

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• Keeping track of dirty blocks on a block device

  - by mikeY

  I'm looking for a way to keep track of what blocks on a block device are modified after a point in time. How I eventually want to use this for is to keep two 2TB disks in sync, one which only comes online (connected through USB) once a month. Without knowing what blocks have been modified, I have to go through the whole 2TB every time. I'm using a recent GNU/Linux OS and have C and Python experience. I'm hoping to avoid writing kernel level code as I don't have any experience in that area whatsoever. My current theory is that there should be some hooks somewhere where my code can get called when a disk flush is performed. Any ideas?

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• Netbeans or Eclipse for C++?

  - by Robert Gould

  I'm currently working on a pet project and need to do C++ development on Windows, Mac, Linux, and Solaris, and I've narrowed it down to Netbeans and Eclipse, so I was wonderig which is more solid as a C++ editor. I just need solid editing, good autocompletion for templated code ad external libraries, and project file management, the build tools are external, so thats irrelevant here, for my comparison. Thus which is a better choice? Note: I know I should be using emacs or vim, but the issue is, my theory at least, that I'm left handed, so I use my right side (design,creativity) of the brain more than the left side (logic, memory), so I just simply cannot use emacs or vim, my brain simply isn't compatible, I tried them many times too, even used emacs for a few months but it drove me crazy... Thanks

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• What is the easiest straightforward way of telling which version performs better?

  - by Peter Perhác

  I have an application, which I have re-factored so that I believe it is now faster. One can't possibly feel the difference, but in theory, the application should run faster. Normally I would not care, but as this is part of my project for my master's degree, I would like to support my claim that the re-factoring did not only lead to improved design and 'higher quality', but also an increase in performance of the application (a small toy-thing - a train set simulation). I have toyed with the latest VisualVM thing today for about four hours but I couldn't get anything helpful out of it. There isn't (or I haven't found it) a way to simply compare the profiling results taken from the two versions (pre- and post- refactoring). What would be the easiest, the most straightforward way of simply telling the slower from the faster version of the application. The difference of the two must have had an impact on the performance. Thank you.

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• memset on array of structures in C++

  - by garry

  I have another memset question. It appears as if the code I am editing may have some issues (or it's not done the same way in different files) A::LRM las[9]; //A and LRM are both structures with BOOLS and INTS memset(&las, 0, sizeof(las)); typedef Sec SecArray[16]; SecArray rad_array; memset(rad_array, 0, sizeof(SecArray)); The second example appears to be correct because rad_array is the same as the first position in the array. Then the sizeof(SecArray)) would make sense. The first one doesn't seem correct to me. All structs are just BOOLs and INTS nothing dynamic in them. My understanding from my other post about memset was that it followed this format. memset("pointer to object", "what to set it to", "size of object") Can anyone tell me what exactly is going on here if I am incorrect with my theory.

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• Creating triangles using borders

  - by Interstellar_Coder

  I recently needed to create speech bubbles. To create the little tip at the end of the speech bubble, i used a css technique where the element is given a 0 width and 0 height and given borders. Making certain borders transparent would create diagonals. This works great, and i am able to manipulate different borders to create triangles/shapes to my liking. The problem is, i don't fully understand why this works. I understand that it all starts out with a rectangle and as you set one or more of the borders to transparent it creates a diagonal. My question is how does this work ? And why does it create a diagonal in the first place ? EDIT: To clarify, i would like to know the theory behind why this technique works.

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• Can jQuery perform a compound select against the top level only?

  - by harpo

  Basically, is there a way to write a.children('.outer').children('.inner') without the intermediate selector? I can't write $('.outer > .inner', a) because I don't want to do full-depth search against a — I know that the .outer elements are immediate children of a. It's partly a matter of "elegance", but partly because I'm trying to avoid "throwaway" element sets. Yes, jQuery may in effect do the same thing, but it has a better chance of optimizing (at least in theory), when it knows the full query's intent.

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• How do I create custom Controls for my VS2005 toolbox?

  - by end-user

  Ok, this question might more about design theory. I have successfully created controls that show up in my toolbox, so I'm pretty sure I have the process right. Also, my "AutoToolboxPopulate" is set to true, so things are showing up as I create them. My question is this: I'm sub-classing a native Control for specialized use. When I derive my class from an exposed concrete class, such as BulletedList, my custom Control appears in my Toolbox. However, when I drop it back to the parent, such as ListControl, my Control is not listed (actually it's grayed out when I "List All"). What am I missing?

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• Referral System PHP

  - by Liam

  I have a membership based website and im planning on implementing a referral system. My website is credit based, the idea is that if User X refers User Y, then User X gets 100 bonus credits. Has anybody built a referral system before and if so what obstacles should I bear in mind? I've had a snoop round SO tonight but couldn't find any suitable answers. My theory is to give each user a random string which is generated and stored in the DB when they sign up, The user will then be presented with a URL incl. that string which when they pass to somebody (User Z), User Z is then sent to a page, the page then uses the GET method to gather the Random string and update the DB Row they currently occupy, does this sound feasible or could it easily be breached? Thanks

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• How can I embed a flash movie in a zend view programmatically?

  - by curro

  I have tried to embed a flash movie in a zend view using the htmlFlash helper. In theory you only have to pass the movie path to the htmlFlash helper in a phtml view: echo $this-htmlFlash('/path/to/myMovie.swf'); And the framework will generate the html code in the html page: <object data="/path/to/flash.swf" type="application/x-shockwave-flash" classid="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000" codebase="http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab"> </object> However, I have done so and the code doesn't appear on the source code. Has anyone had this problem? Thank you

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• sql data source re binding question

  - by Keith

  In my gridview after an insert operation has been done I am filtering the sqldatasource by ID. I am getting an error that the item drop down box selected value is not in the list. To test my theory I created a new sql data source with only the select statement and after the insert operation I am binding it to my grid view and filtering by Id and I get my result. The question Having a second data source is not the solution so is it possible that there is some way to use sqldatasource1? what I tried is sqldatasource.databind() and gridview.databind() on the inserted and inserting metheds in many test cases but still that doesnt work. I dont have any filters applied on the original data source?

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• RegExp to match everything up to first blank line

  - by SKWebDev

  Hi, I'm writing a bash script that will show me what TV programs to watch today, it will get this information from a text file. The text is in the following format: Monday: Family Guy (2nd May) Tuesday: House The Big Bang Theory (3rd May) Wednesday: The Bill NCIS NCIS LA (27th April) Thursday: South Park Friday: FlashForward Saturday: Sunday: HIGNFY Underbelly I'm planning to use 'date +%A' to work out the day of the week and use the output in a grep regex to return the appropriate lines from my text file. If someone can help me with the regex I should be using I would be eternally great full.

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• What to do when using Contract.Assert(true) and the method must return something?

  - by devoured elysium

  I have a bit of code with the following logic: //pseudo-code foreach (element in elementList) { if (element is whatever) return element; } } In theory, there is always one element that is whatever, so this method should pose no problems. In any case, I've put an assertion on the end of the method just to be sure: //pseudo-code foreach (element in elementList) { if (element is whatever) return element; } } Contract.Assert(true, "Invalid state!"); The problem is that as this method has to return something, and the compiler doesn't understand that the assertion will break the program execution. Before using Contracts, in these kind of situations, I used to throw an Exception, which solved the problem. How would you handle this with Contract.Assert()? Returning null or default(element_type) after the Contract.Assert() call knowing it will never be called and shutting up the compiler? Or is there any other more elegant way of doing this? Thanks

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• Should I denormalize a has_many has_many?

  - by Cameron

  I have this: class User < ActiveRecord::Base has_many :serials has_many :sites, :through => :series end class Serial < ActiveRecord::Base belongs_to :user belongs_to :site has_many :episodes end class Site < ActiveRecord::Base has_many :serials has_many :users, :through => :serials end class Episode < ActiveRecord::Base belongs_to :serial end I would like to do some operations on User.serials.episodes but I know this would mean all sorts of clever tricks. I could in theory just put all the episode data into serial (denormalize) and then group_by Site when needed. If I have a lot of episodes that I need to query on would this be a bad idea? thanks

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• remove a varchar2 string from the middle of table data values

  - by Michelle Daniel

  Data in the file_name field of the generation table should be an assigned number, then _01, _02, or _03, etc. and then .ldf (example 82617_01.pdf). Somewhere, the program is putting a state name and sometimes a date/time stamp, between the assigned number and the 01, 02, etc. (82617_ALABAMA_01.pdf or 19998_MAINE_07-31-2010_11-05-59_AM.pdf or 5485325_OREGON_01.pdf for example). We would like to develop an SQL statement to find the bad file names and fix them. In theory it seems rather simple to find file_names that include a varchar2 data type and remove it, but putting the statement together is beyond me. Any help or suggestions apprecuiated. Something like ........... UPDATE GENERATION SET FILE_NAME (?) WHERE FILE_NAME (?...LIKE '%STRING%');?

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• Regular Expression

  - by equilibrium

  Ohh! this regular expression thing is eating my brain up. I have been reading it from Introduction to Automata Theory, Languages and Computer by Hopcroft, Motwani and Ullman. I have solved a few exercises too but could not solve the following even after trying for almost one hr. The problem is to write a regular expression that defines a language consisting of all strings of 0s and 1s except the substring 011. Is the answer (0+1)* - 011 correct ? If not what should be the correct answer for this?

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• is there a good reason to fear closed-source code *inside* of open-source libraries?

  - by jcollum

  Here's the situation. At work here, I hear there is resistance to using open source code (Nant in particular) because there might be copyrighted code in there. Meaning somewhere in that open source tool or library there might be a chunk of code that was directly lifted from copyrighted code. In theory, this means our company (which is quite large) get sued for big money because they used an open source library. We don't ship any software, so how this theoretical plaintiff would find this out is a mystery. I have also heard that some group of people came through a year or two ago and actually found instances of this in our codebase. That's hearsay of course, so who knows. Is this simple paranoia? Didn't something similar to this happen with Linux a while ago? Wouldn't the burden of checking for copyrighted code lie with the people who made the code, not the people who use it?

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