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• Cuda driver, CPU/GPU performances issue

  - by elect

  I implemented a RNS Montgomery exponentiation in Cuda and on cpu for comparison. Everything nice everything fine. It runs on just one SM. However I am going to tell you some strange regression in both cpu/gpu performances. During the devoloping, about two month ago, I was using Cuda 5 preview on Ubuntu 11.04 64b. In this time, I reach the following performances: cpu 460ms gpu 120ms Then one day when I turn on the pc, the graphical environment didnt start. I dont know which was the problem, however I switched to the console and installed again the Cuda driver. At the following boot performances changed: cpu 310ms gpu 80ms I was like Q.Q...uhm ok, nice to see this, but I was wondering how that could be possible However, I went then in holiday for 10 days and I continued developing and optimizing on my notebook (but not the same part of the code, some additional stuff) When I was back, I just updated the source files, and performances came back to 460/120ms.. I couldnt believe it, I tried to install Cuda 5 RC, updating the video driver too... nothing changed... I checked Debug/Release, Cuda computability, but the problem seems being somewhere else.. Looking around the net I found this, I am pretty sure it must have something to do with the driver, because the performance change affected both cpu and gpu Do you have some tips/ideas/suggestions?

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• Is there any kind of established architecture for browser based MMO games?

  - by black_puppydog

  I am beginning the development of a broser based game in which players take certain actions at any point in time. Big parts of gameplay will be happening in real life and just have to be entered into the system. I believe a good kind of comparison might be a platform for managing fantasy football, although I have virtually no experience playing that, so please correct me if I am mistaken here. The point is that some events happen in the program (i.e. on the server, out of reach for the players) like pulling new results from some datasource, starting of a new round by a game master and such. Other events happen in real life (two players closing a deal on the transfer of some team member or whatnot - again: have never played fantasy football) and have to be entered into the system. The first part is pretty easy since the game masters will be "staff" and thus can be trusted to a certain degree to not mess with the system. But the second part bothers me quite a lot, especially since the actions may involve multiple steps and interactions with different players, like registering a deal with the system that then has to be approved by the other party or denied and passed on to a game master to decide. I would of course like to separate the game logic as far as possible from the presentation and basic form validation but am unsure how to do this in a clean fashion. Of course I could (and will) put some effort into making my own architectural decisions and prototype different ideas. But I am bound to make some stupid mistakes at some point, so I would like to avoid some of that by getting a little "book smart" beforehand. So the question is: Is there any kind of architectural works that I can read up on? Papers, blogs, maybe design documents or even source code? Writing this down this seems more like a business application with business rules, workflows and such... Any good entry points for that?

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• Nullable types and ?? operator C# [en-US]

  - by ruimachado

  Nullable types vs Non-nullable types   While developing our C# projects its frequent the null comparison operation to avoid null exceptions. This simple operation is mainly coded using the "var x = null" code example inside an if clause. However not all types of variables are nullable, which means that setting a variable to null is not allowed in every cases, it depends on what kind of type are you defining. But what if there was an extension to your non-nullable type that would convert your variable types to nullable? This extension really exists. As I said before in C# you have nullable types which represent all the values of an underlying type, and an additional null value and can be declared easily using "T?", where T is the type of the variable and for example the normal int type cannot be null, so its a non-nullable type, however if you define a "int?" your variable can be null, what you do is convert a non-nullable type to a nullable type. Example: int x=null;     Not allowed     int? x=null;   Allowed     While using nullable types you can check if a variable is null the same way you do it with nullable types:     But what about setting a default value when a certain variable is null?   In this cases the c# .net framework let you set a default value when you try to assign a nullable type to a non-nullable type, using the ?? operator. If you don't use this operator you can still catch the InvalidOperationException which is throw in this cases. For example  without the ?? operator :     Using the ?? operator your code becomes cleaner and more easy to read and you get a bonus, you can set a default value for multiple variables using the ?? in a chain set.     That’s it,   Thanks, Rui Machado rpmachado.wordpress.com

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• What are solutions and tradeoffs to maintain search result consistency in a web application

  - by iammichael

  Consider a web application with a custom search function that must display the results in a paged manner (twenty per page with up to hundreds of thousands of total results) and the ability to drill down to individual results that maintain next/previous links to navigate through the results. Re-executing the search on each page request to get the appropriate results for that page of data can be too expensive (up to 15s per search). Also, since the underlying data can change frequently (e.g. addition of new results), re-executing could cause the next/previous functionality to result in inconsistent behavior (e.g. the same results reappearing on a later page after having been viewed on an earlier page). What options exist to ensure the search results can be viewed across multiple pages in a consistent manner, and what tradeoffs does each option have in terms of network, CPU, memory, and storage requirements? EDIT: I thought caching the query search results was an obvious necessity. The question is really asking about where to cache the result set and what tradeoffs might exist to each. For example, storing the ids of the entities in the result set on the client, or storing the IDs of the entities themselves in the users session on the web server, or in a temporary table in the database. I'm not looking specifically for a single solution as different scenarios may result in different approaches (and such a question would be more suited for stackoverflow.com rather than here), but more of a design comparison between the possible approaches.

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• Clustering Strings on the basis of Common Substrings

  - by pk188

  I have around 10000+ strings and have to identify and group all the strings which looks similar(I base the similarity on the number of common words between any two give strings). The more number of common words, more similar the strings would be. For instance: How to make another layer from an existing layer Unable to edit data on the network drive Existing layers in the desktop Assistance with network drive In this case, the strings 1 and 3 are similar with common words Existing, Layer and 2 and 4 are similar with common words Network Drive(eliminating stop word) The steps I'm following are: Iterate through the data set Do a row by row comparison Find the common words between the strings Form a cluster where number of common words is greater than or equal to 2(eliminating stop words) If number of common words<2, put the string in a new cluster. Assign the rows either to the existing clusters or form a new one depending upon the common words Continue until all the strings are processed I am implementing the project in C#, and have got till step 3. However, I'm not sure how to proceed with the clustering. I have researched a lot about string clustering but could not find any solution that fits my problem. Your inputs would be highly appreciated.

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• rails: has_many :through + polymorphism validation?

  - by ramonrails

  I am trying to achieve this. Any hints? A project has many users through join model A user has many projects through join model Admin class inherits User class. It also has some Admin specific stuff. Admin like inheritance for Supervisor and Operator Project has one Admin, One supervisor and many operators. Now I want to 1. submit data for project, admin, supervisor and operator in a single project form 2. validate all and show errors on the project form. Project has_many :users, :through = :projects_users User has_many :projects, :through = :projects_users ProjectsUser = :id integer, :user_id :integer, :project_id :integer, :user_type :string ProjectUser belongs_to :project, belongs_to :user, :polymorphic = true Admin < User Supervisor < User Operator < User Is the approach correct? Any and all suggestions are welcome.

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• What language available on commodity web hosts would suit a C# developer? [closed]

  - by billpg

  Recognising its ubiquity on commodity web hosting services, I tried developing in PHP a few years ago. I really didn't like it, later deciding that life was too short for PHP. (In brief, having to put $ on variable names; mis-spelt variable names become new variables; converting non-numeric strings to integers without complaint; the need for an "and this time I mean it" comparison operator.) In my ideal world, commodity web hosts would all support C#/ASP.NET, my preferred web-development language and framework, but this is not my ideal world. Even Mono has barely made a dent on Linux based hosts. However, last time I moaned about PHP's ubiquity, someone followed up that this was no longer the case, and that many other languages are now commonly usable on web hosts too. What programming language; a. Would suit a developer who prefers C#. b. Is available to run on many web hosts.

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• Distance between hyperplanes

  - by michael dillard

  I'm trying to teach myself some machine learning, and have been using the MNIST database (http://yann.lecun.com/exdb/mnist/) do so. The author of that site wrote a paper in '98 on all different kinds of handwriting recognition techniques, available at http://yann.lecun.com/exdb/publis/pdf/lecun-98.pdf. The 10th method mentioned is a "Tangent Distance Classifier". The idea being that if you place each image in a (NxM)-dimensional vector space, you can compute the distance between two images as the distance between the hyperplanes formed by each where the hyperplane is given by taking the point, and rotating the image, rescaling the image, translating the image, etc. I can't figure out enough to fill in the missing details. I understand that most of these are indeed linear operators, so how does one use that fact to then create the hyperplane? And once we have a hyperplane, how do we take its distance with other hyperplanes?

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• User Defined Class as a Template Parameter

  - by isurulucky

  Hi, I' m implementing a custom STL map. I need to make sure that any data type (basic or user defined) key will work with it. I declared the Map class as a template which has two parameters for the key and the value. My question is if I need to use a string as the key type, how can I overload the < and operators for string type keys only?? In template specialization we have to specialize the whole class with the type we need as I understand it. Is there any way I can do this in a better way?? What if I add a separate Key class and use it as the template type for Key? Thank You!!

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• Why does there seem to be a lot of fear in choosing the "wrong" language to learn?

  - by Shewbox

  Perhaps its just me, but as a current CS student I have already come across many questions on this site and elsewhere about not just "Which language should I use for x?" but also "Does anyone still use language Y?" My first CS class was taught in Scheme, which, if I'm not mistaken, isn't used widely (at least in comparison to languages like Java, PHP, Python, etc). Many of my classmates balked at the idea of having to learn a language they would never have to use again, but I don't quite understand where so much of this fear of learning less popular languages comes from. No, I may not use Scheme in any job I get, but I certainly don't regret having learned to use it (albeit in a very beginner, not very in-depth manner in that one semester). I am taking a search engines class this semester, which is done in Perl and again I am seeing classmates complaining about the language choice. I can understand having a favorite language and disliking others but why do some get worked up over learning it in the first place? Can you really learn the "wrong" language? Isn't learning something like Scheme or Haskell good mental exercise if nothing else, and useful at least to exposure to different ways of solving problems?

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• Nonstatic conversion functions; Casting different types, e.g. DirectX vector to OpenGL vector

  - by Markus

  I am currently working on a game "engine" that needs to move values between a 3D engine, a physics engine and a scripting language. Since I need to apply vectors from the physics engine to 3D objects very often and want to be able to control both the 3D, as well as the physics objects through the scripting system, I need a mechanism to convert a vector of one type (e.g. vector3d<float>) to a vector of the other type (e.g. btVector3). Unfortunately I can make no assumptions on how the classes/structs are laid out, so a simple reinterpret_cast probably won't do. So the question is: Is there some sort of 'static'/non-member casting method to achieve basically this: vector3d<float> operator vector3d<float>(btVector3 vector) { // convert and return } btVector3 operator btVector3(vector3d<float> vector) { // convert and return } Right now this won't compile since casting operators need to be member methods. (error C2801: 'operator foo' must be a non-static member)

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• ASP.Net navigation tabs like windows tab control

  - by devphil

  I would like to have a webpage something like windows tab control. Each webpage does not lose the contents and data while moving between pages, postbacks, etc. Here is the website design and my idea: [Master Page] "Fruits" "Cars" "Animals" "Operators" clicking on "Fruits" will forwards to "Fruits" page, and the same for other links (tabs) The user works on "Fruits" page searching fruits, fill up some fields, etc. The user then moves to "Cars" page and then builds up his own car by filling some fields, etc and then the user goes back to "Fruits" page again - the user sees the same page where she/he left on "Fruits" page. Please suggest some good ways other than using javascript:history.go(-1). Is this possible to implement?

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• Booting off a ZFS root in 14.04

  - by RJVB

  I've been running a Debian derivative (LMDE) on a ZFS root for half a year now. It was created by cloning a regular ext4-based install with all the necessary packages onto a ZFS pool, chrooting into that pool and recreating a grub menu and bootloader. The system uses an ext-3 dedicated /boot partition. I would like to do the same with Ubuntu 14.04, but have encountered several obstacles. There is no Trusty zfs-grub package The default grub package doesn't have ZFS support built in. I found a small bug in the build system responsible for that (report with patch created) and built my own grub packages. The built-in ZFS support is dysfunctional, it does not add the proper arguments to the kernel command line I thus installed the ZoL grub package I also use on my LMDE system, which does give me a correct grub.cfg However, even with that correct grub.cfg, the boot process apparently doesn't retrieve the bootfs parameter from the ZFS pool; instead the variable that's supposed to receive the value remains empty. As a result, initrd tries to load the default pool ("rpool"), which fails of course. I can however import the pool by hand, and complete the process by hand. If memory serves me well, I also had to disable apparmor, to avoid the boot process from blocking after importing the pool. Am I overlooking something? Just for comparison, I installed the Ubuntu 3.13 kernel on my LMDE system, and that works just fine (i.e. the identical kernel and grub binaries allow successful booting without glitches on LMDE but not on Ubuntu).

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• Creating LINQ to SQL for counting a parameter

  - by Matt

  I'm trying to translate a sql query into LINQ to SQL. I keep getting an error "sequence operators not supported for type 'system.string'" If I take out the distinct count part, it works. Is it not because I'm using the GROUP BY? SELECT COUNT(EpaValue) AS [Leak Count], Location, EpaValue AS [Leak Desc.] FROM ChartMes.dbo.RecourceActualEPA_Report WHERE (EpaName = N'LEAK1') AND (Timestamp) '20100429030000' GROUP BY EpaValue, Location ORDER BY Location, [Leak Count] DESC Dim temp = (From p In db2.RecourceActualEPA_Reports _ Where (p.Timestamp = str1stShiftStart) And (p.Timestamp < str2ndShiftCutoff) _ And (p.EpaName = "Leak1") _ Select p.EpaName.Distinct.Count(), p.Location, p.EpaValue)

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• How do I cluster strings based on a relation between two strings?

  - by Tom Wijsman

  If you don't know WEKA, you can try a theoretical answer. I don't need literal code/examples... I have a huge data set of strings in which I want to cluster the strings to find the most related ones, these could as well be seen as duplicate. I already have a set of couples of string for which I know that they are duplicate to each other, so, now I want to do some data mining on those two sets. The result I'm looking for is a system that would return me the possible most relevant couples of strings for which we don't know yet that they are duplicates, I believe that I need clustering for this, which type? Note that I want to base myself on word occurrence comparison, not on interpretation or meaning. Here is an example of two string of which we know they are duplicate (in our vision on them): The weather is really cold and it is raining. It is raining and the weather is really cold. Now, the following strings also exist (most to least relevant, ignoring stop words): Is the weather really that cold today? Rainy days are awful. I see the sunshine outside. The software would return the following two strings as most relevant, which aren't known to be duplicate: The weather is really cold and it is raining. Is the weather really that cold today? Then, I would mark that as duplicate or not duplicate and it would present me with another couple. How do I go to implement this in the most efficient way that I can apply to a large data set?

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• how to structure code that uses std::rel_ops

  - by R Samuel Klatchko

  I was working on some code and wanted to make use of std::rel_ops. From what I can tell, you need to do using std::rel_ops to your source code to make use of them. But I'm not sure where the best place to put that is. Let's say I have a header file with a class that only defines the minimal operator== and operator<: // foo.h class foo { public: bool operator==(const foo &other) const; bool operator<(const foo &other) const; }; I'm not sure where to put using std::rel_ops. If I leave it out of the foo.h, then every user of foo.h needs to know the implementation detail that foo is not defining all the operators itself. But putting using std::rel_ops inside foo.h breaks the rule of thumb about not having a using in a header file. How do other people resolve this issue?

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• Is there a way to serialize automatically enums as int?

  - by FireAphis

  Hello, Is there a way to serialize enums automatically as int? Every time I define a new enum and write std::stringstream stream; stream << myenum1; stream >> myenum2; the compiler complains that the operators << and are not defined. Do you know a way to tell the compiler to treat enums as plain int's? What makes the problem harder is that, actually, the serialization is inside a template. Something like this: template <typename T> void serialize(const T& value) { std::stringstream stream; stream << value; } So I cannot add any casts :( Maybe I can specialize it somehow? Thank you.

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• VB.NET logical expression evaluator

  - by Tim

  I need to test a logical expression held in a string to see if it evaluate to TRUE or FALSE.(the strig is built dynamically) For example the resulting string may contain "'dog'<'cat' OR (14 AND 4<6)". There are no variables in the string, it will logically evaluate. It will only contain simple operators = < < = <= and AND , OR and Open and Close Brackets, string constants and numbers. (converted to correct syntax && || etc.) I currently acheive this by creating a jscipt function and compiling it into a .dll. I then reference the .dll in my VB.NET project. class ExpressionEvaluator { function Evaluate(Expression : String) { return eval(Expression); } } Is there a simpler method using built in .NET functions or Lamdba expressions.

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• using NEWSEQUENTIALID() with UPDATE Trigger

  - by Ram

  I am adding a new GUID/Uniqueidentifier column to my table. ALTER TABLE table_name ADD VersionNumber UNIQUEIDENTIFIER UNIQUE NOT NULL DEFAULT NEWSEQUENTIALID() GO And when ever a record is updated in the table, I would want to update this column "VersionNumber". So I create a new trigger CREATE TRIGGER [DBO].[TR_TABLE_NAMWE] ON [DBO].[TABLE_NAME] AFTER UPDATE AS BEGIN UPDATE TABLE_NAME SET VERSIONNUMBER=NEWSEQUENTIALID() FROM TABLE_NAME D JOIN INSERTED I ON D.ID=I.ID/* some ID which is used to join*/ END GO But just realized that NEWSEQUENTIALID() can only be used with CREATE TABLE or ALTER TABLE. I got this error The newsequentialid() built-in function can only be used in a DEFAULT expression for a column of type 'uniqueidentifier' in a CREATE TABLE or ALTER TABLE statement. It cannot be combined with other operators to form a complex scalar expression. Is there a workaround for this ? Edit1: Changing NEWSEQUENTIALID() to NEWID() in the trigger solves this, but I am indexing this column and using NEWID() would be sub-optimal

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• NFS mount of /var/www to OS X

  - by ploughguy

  I have spent 2 hours trying to create an NFS mount from my Ubuntu 10.04 LTS server to my OS X desktop system. Objective: three way file compare between the code base on the Mac, the development system on the local Linux test system, and the hosted website. The hosted service uses cpanel so I can mount a webdisk - easy as pie - took 10 seconds. The local Ubuntu box, on the other hand - nothing but pain and frustration. Here is what I have tried: In File Browser, navigate to /var/www/site and right-click. Select share this folder. Enter sharename wwwsite and a comment. Click button "Create Share". Message says - you can only share file systems you own. There is a message on how to fix this, but the killer is that this is sharing by SMB. It will change the LFs to CR-LFs which will affect the file comparison. So forget this option. In a terminal window, run shares-admin (I have not been able to convince it to give me the "Shared Folders" option in the System Administration window - Maybe it is somewhere else in the menu, but I cannot find it) define an NFS export. Enter the path /var/www/site, select NFS enter the ip address of the iMac and save. On the mac, try to mount the file system using the usual methods - finder, command line "mount" command - not found. Nothing. Tried restarting the linux box in case there is a daemon that needs restarting - nothing. So I have run out of stuff to do. I have tried searching the documentation - it is pretty basic. The man page documentation is as opaque as ever. Please, oh please, will someone help me to get this @38&@^# thing to work! Thanks for reading this far... PG.

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• Semantic errors

  - by gautam kumar

  Can semantic errors be detected by the compiler or not? If not when do the errors get detected? As far as I know semantic errors are those errors which result from the expressions involving operators with incorrect number/type of operands. For example: n3=n1*n2;//n1 is integer, n2 is a string, n3 is an integer The above statement is semantically incorrect. But while reading C Primer Plus by Stephen Prata I found the following statement The compiler does not detect semantic errors, because they don't violate C rules. The compiler has no way of divining your true intentions. That leaves it to you to find these kinds of errors. One way is to compare what a program does to what you expected it to do. If not the compiler, who detects those errors? Am I missing something?

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• Mixing LINQ to SQL with properties of objects in a generic list

  - by BPotocki

  I am trying to accomplish something like this query: var query = from a in DatabaseTable where listOfObjects.Any(x => x.Id == a.Id) select a; Basically, I want to filter the results where a.Id equals a property of one of the objects in the generic list "listOfObjects". I'm getting the error "Local sequence cannot be used in LINQ to SQL implementation of query operators except the Contains() operator." Any ideas on how to filter this in an easily readable way using "contains" or another method? Thanks in advance.

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• How to create a valid schema in a WSDL that restrict to <|<=|>|>=

  - by wsxedc

  This is what I have in my schema section of my WSDL to specify the field has to be comparison operators <xsd:simpleType> <xsd:restriction base="xsd:string"> <xsd:pattern value="&lt;|&gt;|&lt;=|&gt;=|="/> </xsd:restriction> </xsd:simpleType> SoapUI complains about this part of the WSDL, I tried to set the value to something with non special characters and the WSDL is valid. So I tried to replace that whole long string to be value=">gt;" and it valid but value="<lt;" is not valid, and value=">" is also not valid. My question is, why does the WSDL validation need > to be double escaped? The main question is, how to provide a valid less than side within the pattern value.

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• How to create and Expression tree to do the same as "StartsWith"

  - by Jonathan

  Hi to all. Currently, I have this method to compare two numbers Private Function ETForGreaterThan(ByVal query As IQueryable(Of T), ByVal propertyValue As Object, ByVal propertyInfo As PropertyInfo) As IQueryable(Of T) Dim e As ParameterExpression = Expression.Parameter(GetType(T), "e") Dim m As MemberExpression = Expression.MakeMemberAccess(e, propertyInfo) Dim c As ConstantExpression = Expression.Constant(propertyValue, propertyValue.GetType()) Dim b As BinaryExpression = Expression.GreaterThan(m, c) Dim lambda As Expression(Of Func(Of T, Boolean)) = Expression.Lambda(Of Func(Of T, Boolean))(b, e) Return query.Where(lambda) End Function It works fine and is consumed in this way query = ETForGreaterThan(query, Value, propertyInfo) As you can see, I give it an IQueryable collection and it add a where clause to it, base on a property and a value. Y can construct Lessthan, LessOrEqualThan etc equivalents as Expression has this operators predefined. ¿How can I transform this code to do the same with strings? Expression don't give me a predefined operator like "contains" or "startwith" and I'm really noob with Expression trees. Thanks, and please Post your answer in C#/VB. Choose the one that make you feel more confortable.

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• Recommended display/background brightness ratio and UI color schemes [duplicate]

  - by user1306322

  This question already has an answer here: Colour scheme for editor - guidelines or medical reccomendations 3 answers I'm a professional programmer, which means I spend a lot of time staring at various displays. Recently I've been having some problems with my eyes, so I went to talk to several doctors, which all gave me different recommendations as to how bright the background of the room should be in comparison to the display's brightness. It was very confusing, as some of them even agreed with counter-arguments of others, which made it all even less clear. So I'd like to ask the professional programmers, as people who actually have some experience with that. Some of the doctors said that looking at a monitor is like looking at a book, so the brightness ratios should be approximately the same. Others said that background should be as bright as the display itself, because then there is no brightness difference at the edges, and that's what may cause eye fatigue. From my own experience, I can say that reading a book isn't the same as writing or debugging a program, where you have to pay close attention to each symbol, and in books most words are easily recognizable without focusing too hard on them. Also, books are black on white and I myself use the default (dark text, white bg) color scheme for my IDE, but I've seen some programmers use mid-bright text on very dark background color schemes. So I'd like to ask what are the recommended display/background brightness ratios for programming? I'm not sure this site is the right one for this kind of questions, so if you know a better one, please comment.

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