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• Integer Linear Programming Java: Multiple Open Source and Commercial tools are available. Which one

  - by Sandeep Jindal

  Hi, I need to use Integer Linear Programming API/Tool for my application. Though my application is in Java but I don’t mind calling an EXE (Tool) from Java providing input using file (MPS, etc). My search analysis is as follows: There are multiple Open Source and Commercial tools available to solve ILP Following I found and think are useful for my needs. 1. Gnu LP Kit(GLPK): I think this is the oldest and probably most stable and efficient 2. IP_Solve: Has good reviews about it. 3. JavaILP: Found this, but not much reviews about it 4. Apache Common-Math: Supports LP but not ILP, so ruled out. 5. Coin-OR Can you please suggest which one shall be the best in terms of stability, efficiency, acceptance, etc Regards Sandeep Jindal

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• MTU mismatch between GetIfEntry and netsh

  - by ChrisJ

  I'm working on pseudo-transport layer software that runs over UDP, providing reliable connection-oriented transmission, as an alternative to TCP. In order to maximize network efficiency, we query the MTU of the "best" network adapter upon initialization. MIB_IFROW row = {0}; row.dwIndex = dwBestIfIndex; dwRes = GetIfEntry(&row); Searching online I found that you can use the following netsh commands to query for this same value, from a command prompt (not a C++ API) netsh interface ipv4 show interfaces netsh interface ipv4 show subinterfaces The troubling issue is that while row.dwMtu may be set to 1500, snooping the network traffic on the sending laptop shows that our packets are fragmented into 1300 byte packets. netsh also reports that the MTU is 1300. Clearly the value reported by netsh command is the actual used values. Anyone know what API I can call to get the same values as netsh?

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• Python regular expression implementation details

  - by Tom

  A question that I answered got me wondering: How are regular expressions implemented in Python? What sort of efficiency guarantees are there? Is the implementation "standard", or is it subject to change? I thought that regular expressions would be implemented as DFAs, and therefore were very efficient (requiring at most one scan of the input string). Laurence Gonsalves raised an interesting point that not all Python regular expressions are regular. (His example is r"(a+)b\1", which matches some number of a's, a b, and then the same number of a's as before). This clearly cannot be implemented with a DFA. So, to reiterate: what are the implementation details and guarantees of Python regular expressions? It would also be nice if someone could give some sort of explanation (in light of the implementation) as to why the regular expressions "cat|catdog" and "catdog|cat" lead to different search results in the string "catdog", as mentioned in the question that I referenced before.

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• Programatically detect number of physical processors/cores or if hyper-threading is active on Window

  - by HTASSCPP

  I have a multithreaded c++ application that runs on Windows, Mac and a few Linux flavours. To make a long story short: Inorder for it to run at maximum efficiency I have to be able to instantiate a single thread per physical processor/core. Creating more threads than there are physical processors/cores degrades the performance of my program considerably. I can already correctly detect the number of logical processors/cores correctly on all three of these platforms. To be able to detect the number of physical processors/cores correctly I'll have to detect if hyper-treading is supported AND active. My question therefore is if there is a way to detect whether hyperthreading is supported AND ENABLED? If so, how exactly.

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• Keyboard layout for international programmers?

  - by splattne

  I think everybody who had to program using a standard German (or any other international) keyboard layout on Windows (or Mac) will complain about the conundrum of either having all special characters ( [ ] | { } / etc. ) needed for most programming languages "at the fingertip" and "losing" the language specific characters (umlauts ä ö ü etc.) on the keyboard or viceversa: having simple access to umlauts, but not to brackets etc. If you are programming in C / C++ / C# / Java / Javascript for example, it is very exhausting if you have to press Alt-Gr + 7 for every opening curly bracket. It is an ergonomic nightmare and reduces your typing efficiency. What is the best way to cope with this problem? Is there a satisfying solution? Maybe there are special layouts or keyboards which address this issue?

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• ColdFusion structs Direct Assignment vs object literal notation.

  - by Tom Hubbard

  The newer versions of ColdFusion (I believe CF 8 and 9) allow you to create structs with object literal notation similar to JSON. My question is, are there specific benefits (execution efficiency maybe) to using object literal notation over individual assignments for data that is essentially static? For example: With individual assignments you would do something like this: var user = {}; user.Fname = "MyFirstnam"; user.Lname = "MyLastName"; user.titles = []; ArrayAppend(user.titles,'Mr'); ArrayAppend(user.titles,'Dr.'); Whereas with object literals you would do something like. var user = {Fname = "MyFirstnam", Lname = "MyLastName", titles = ['Mr','Dr']}; Now this limited example is admittedly simple, but if titles was an array of structures (Say an array of addresses), the literal notation becomes awkward to work with.

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• Which is faster in Python: x**.5 or math.sqrt(x)?

  - by Casey

  I've been wondering this for some time. As the title say, which is faster, the actual function or simply raising to the half power? UPDATE This is not a matter of premature optimization. This is simply a question of how the underlying code actually works. What is the theory of how Python code works? I sent Guido van Rossum an email cause I really wanted to know the differences in these methods. My email: There are at least 3 ways to do a square root in Python: math.sqrt, the '**' operator and pow(x,.5). I'm just curious as to the differences in the implementation of each of these. When it comes to efficiency which is better? His response: pow and ** are equivalent; math.sqrt doesn't work for complex numbers, and links to the C sqrt() function. As to which one is faster, I have no idea...

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• effective retrieve for a voting system in PHP and MySQL

  - by Adnan

  Hello, I have a system where registered users can vote up/vote down comment for a picture. Something very similar to SO's voting system. I store the votes in a table with values as such; vote_id | vote_comment_id | vote_user_id | vote_date | vote_type Now I have few a question concerned the speed and efficiency for the following; PROB: Once a user opens the picture page with comments I need, if that user has already voted UP/DOWN a comment to show it like; "you voted up" or "you voted down" next to the comment (in SO it the vote image is highlighted) MY POSSIBLE SOL: Right now when I open a picture page for each comment I loop thru, I loop thru my table of votes as well and check if a user has voted and show the status (I compare the vote_user_id with the user's session). How efficient is this? Anyone have a better approach to tackle this kind of problem?

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• How to persist a very abstract data type between sessions: PHP

  - by Greelmo

  I have an abstract data type that behaves much like stack. It represents a history of "graph objects" made by a particular user. Each "graph object" holds one or more "lines", a date range, keys, and a title. Each "line" holds a sql generator configured for a particular subset of data in my db. I would like for these "histories" to be available to users between their sessions. It will be in the form of a tab that reads something like "most recent graphs". What do you believe to be the best way to persist this type of data between sessions. This application could get rather large, so efficiency is a concern. Thanks in advance.

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• geo-indexing: efficiently calculating proximity based on latitude/longitude

  - by AnC

  My simple web app (WSGI, Python) supports text queries to find items in the database. Now I'd like to extend this to allow for queries like "find all items within 1 mile of {lat,long}". Of course that's a complex job if efficiency is a concern, so I'm thinking of a dedicated external module that does indexing for geo-coordinates - sort of like Lucene would for text. I assume a generic component like this already exists, but haven't been able to find anything so far. Any help would be greatly appreciated.

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• Nielson's usablity scale

  - by Banderdash

  Just wondering if anyone out there knows of a standard survey (preferably based off Jacob Nielson's work on usability) that web admin's can administer to test groups for usability? I could just make up my own but I feel there as got to be some solid research out there on the sort of judgments on tasks I should be asking. For example Q:: Ask user to find profile page Do I ... A.) Present them with standard likert scale after each question B.) Present them the likert after all the questions .. Then what should that likert be, I know Nielson's usability judgments scale is based on Learnability, Efficiency of Use, Memorability, Error Rate, Satisfaction but I can only imagine a likert I would design that would effectively measure satisfaction...how am I suppose to ask a user to rank the Memorability of a site after one use on a 1-5 scale? Surely someone has devised a good way to pose the question?

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• effective retrieve for a voting system in PHP

  - by Adnan

  Hello, I have a system where registered users can vote up/vote down comment for a picture. Something very similar to SO's voting system. I store the votes in a table with values as such; vote_id | vote_comment_id | vote_user_id | vote_date Now I have few a question concerned the speed and efficiency for the following; PROB: Once a user opens the picture page with comments I need, if that user has already voted UP/DOWN a comment to show it like; "you voted up" or "you voted down" next to the comment (in SO it the vote image is highlighted) MY POSSIBLE SOL: Right now when I open a picture page for each comment I loop thru, I loop thru my table of votes as well and check if a user has voted and show the status (I compare the vote_user_id with the user's session). How efficient is this? Anyone have a better approach to tackle this kind of problem?

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• What is better, a STL list or a STL Map for 20 entries, considering order of insertion is as importa

  - by Abhijeet

  I have the following scenario.The implementation is required for a real time application. 1)I need to store at max 20 entries in a container(STL Map, STL List etc). 2)If a new entry comes and 20 entries are already present i have to overwrite the oldest entry with the new entry. Considering point 2, i feel if the container is full (Max 20 entries) 'list' is the best bet as i can always remove the first entry in the list and add the new one at last (push_back). However, search won't be as efficient. For only 20 entries, does it really make a big difference in terms of searching efficiency if i use a list in place of a map? Also considering the cost of insertion in map i feel i should go for a list? Could you please tell what is a better bet for me ?

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• Offtopic : how can I see my deleted question? Why it was deleted, but not closed?

  - by Tom

  I know it is offtopic and I will delete my question as soon as I get any answer, but somebody deleted my question. The question was opened for the whole day, but when I got 3 reopens and edited my question for asking for 2 more reopens to reopen my question, somebody deleted my question. It was about efficiency during the programming. Why somebody deleted my question and didn't let to be it closed? I found there many good answers although it was closed and now I can see absolutely nothing so I suppose it was deleted. Can somebody tell me smth?

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• Dealing with UIImagePickerController to minimize memory useage

  - by Gordon Fontenot

  So, I have read the SO post on UIImagePickerController, UIImage, Memory and More, and I read the post on Memory Leak Problems with UIImagePickerController in iPhone. I have VASTLY increased my memory efficiency between these 2 posts, and I thank the OPs and the people that provided the answers. I just had a question on the answer provided in the Memory Leak question, which was (essentially): only have one instance of the controller throughout the programs runtime What would be the best way to go about this without causing memory leaks? Right now I am initiating it and releasing it on every use from within the view, and I am seeing exactly what the answer describes (Memory warnings and a crash after about 20 uses). Should I initiate the UIImagePickerController when I need it, but use a seperate class unrelated to the view to control it? How should I deal with releasing the controller if I do it this way?

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• Base-camp Style Subdomains and IDs of Models

  - by Newy

  I have an app that has Basecamp-style subdomains, that is, I have Projects, Users, Apples and Oranges. The Users, Apples and Oranges are all keyed to a Project and only exist in the http://project.myapp.com. I added a project_id to Users, Apples and Oranges and everything works, except of course that the ids of those three objects increment globally, and throughout my app I lookup objects by that id. This doesn't seem like best practice. Should I instead do lookups by a secondary key? How does that affect efficiency? If there's a good blog post that covers this, would be wesome.

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• Pre-allocate memory between HostApp and DLL

  - by Leo

  I have a DLL which provided a decoding function, as follows: function MyDecode (Source: PChar; SourceLen: Integer; var Dest: PChar; DestLen: Integer): Boolean; stdcall; The HostApp call "MyDecode", and transfer into the Source, SourceLen and Dest parameters, the DLL returns decoded Dest and DestLen. The problem is: The HostApp impossible to know decoded Dest length, and therefore would not know how to pre-allocated Dest's memory. I know that can split "MyDecode" into two functions: function GetDecodeLen (Source: PChar; SourceLen: Integer): Integer; stdcall; // Return the Dest's length function MyDecodeLen (Source: PChar; SourceLen: Integer; var Dest: PChar): Boolean; stdcall; But, My decoding process is very complicated, so if split into two functions will affect the efficiency. Is there a better solution?

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• binary file formats: need for error correction?

  - by Jason S

  I need to serialize some data in a binary format for efficiency (datalog where 10-100MB files are typical), and I'm working out the formatting details. I'm wondering if realistically I need to worry about file corruption / error correction / etc. What are circumstances where file corruption can happen? Should I be building robustness to corruption into my binary format? Or should I wrap my nonrobust-to-corruption stream of bytes with some kind of error correcting code? (any suggestions? I'm using Java) Or should I just not worry about this?

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• Tips for optimizing C#/.NET programs

  - by Bob

  It seems like optimization is a lost art these days. Wasn't there a time when all programmers squeezed every ounce of efficiency from their code? Often doing so while walking 5 miles in the snow? In the spirit of bringing back a lost art, what are some tips that you know of for simple (or perhaps complex) changes to optimize C#/.NET code? Since it's such a broad thing that depends on what one is trying to accomplish it'd help to provide context with your tip. For instance: When concatenating many strings together use StringBuilder instead. If you're only concatenating a handful of strings it's ok to use the + operator. Use string.Compare to compare 2 strings instead of doing something like string1.ToLower() == string2.ToLower()

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• How to scroll and zoom in/out large images on iPhone?

  - by Horace Ho

  I have a large image, size around 30000 (w) x 6000 (h) pixels. You may consider it's like a big map. I assume I need to crop it up into smaller tiles. Questions: what are the right ViewControllers to use? (link) what is the tile strategy? (I put this in another question, as it's not iPhone specific) Requirements: whole image (though cropped) can be scrolled up/down/left/right by swipes zoom in (up to pixel-to-pixel) out (down to screen-fit-by-height) by the 2-finger operation memory efficiency by lazy loading tiles Bonus requirements: automatic scroll, say from left to right slowly and smoothly Thanks!

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• From interpeted to native code: "dynamic" languages compiler support

  - by Daniel

  First, I am aware that dynamic languages is a term used mainly by a vendor; I am using it just to have a container word to include languages like Perl (a favorite of mine), Python, Tcl, Ruby, PHP and so on. They are interpreted but I am interested here to refer to languages featuring strong capability to support the programmer efficiency and the support for typical constructs of modern interpreted languages My question is: there are dynamic languages can be compiled efficiently in native executable code - typically for Windows platforms? Which ones? Maybe using some third part ad-hoc tools? I am not talking about huge executables carrying with them a full interpreter or some similar tricks nor some smart module able to include its own dependances or some required modules, but a honest, straight, standard, solid executable code. If not, there is some technical reason inhibiting the availability of such a best-of-both-world feature? Thanks! Daniel

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• Retail knowledge inference

  - by blueomega

  So i am doing a research on how can i infer knowledge from reports (not with a specific format), but after pre processing, i should have some kind of formatted data. A fairly basic inference would be: "Retailer has X stock." and "X is sellable." - "Retailer sells X" the knowledge i focus is retail domain oriented, and if possible i should improve its efficiency with each iteration. Is this scifi(some of my friends think it is)? The related stuff i find online are "expert systems" that find anomalies, fuzzy inference systems and some rants about "easy knowledge". Can you help me with some points for me to focus or orient me in some research directions? blueomega

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• Filter zipcodes by proximity in Django with the Spherical Law of Cosines

  - by spiffytech

  I'm trying to handle proximity search for a basic store locater in Django. Rather than haul PostGIS around with my app just so I can use GeoDjango's distance filter, I'd like to use the Spherical Law of Cosines distance formula in a model query. I'd like all of the calculations to be done in the database in one query, for efficiency. An example MySQL query from The Internet implementing the Spherical Law of Cosines like this: SELECT id, ( 3959 * acos( cos( radians(37) ) * cos( radians( lat ) ) * cos( radians( lng ) - radians(-122) ) + sin( radians(37) ) * sin( radians( lat ) ) ) ) AS distance FROM stores HAVING distance < 25 ORDER BY distance LIMIT 0 , 20; The query needs to reference the Zipcode ForeignKey for each store's lat/lng values. How can I make all of this work in a Django model query?

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• Effective methods for reading and writing large files in C

  - by Bertholt Stutley Johnson

  I'm writing an application that deals with very large user-generated input files. The program will copy about 95 percent of the file, effectively duplicating it and switching a few words and values in the copy, and then appending the copy (in chunks) to the original file, such that each block (consisting of between 10 and 50 lines) in the original is followed by the copied and modified block, and then the next original block, and so on. The user-generated input conforms to a certain format, and it is highly unlikely that any line in the original file is longer than 100 characters long. Which would be the better approach? a) To use one file pointer and use variables that hold the current position of how much has been read and where to write to, seeking the file pointer back and forth to read and write; or b) To use multiple file pointers, one for reading and one for writing. I am mostly concerned with the efficiency of the program, as the input files will reach up to 25,000 lines, each about 50 characters long. Thanks!

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• How do we achieve "substring-match" under O(n) time?

  - by Pacerier

  I have an assignment that requires reading a huge file of random inputs, for example: Adana Izmir Adnan Menderes Apt Addis Ababa Aden ADIYAMAN ALDAN Amman Marka Intl Airport Adak Island Adelaide Airport ANURADHAPURA Kodiak Apt DALLAS/ADDISON Ardabil ANDREWS AFB etc.. If I specify a search term, the program is supposed to find the lines whereby a substring occurs. For example, if the search term is "uradha", the program is supposed to show ANURADHAPURA. If the search term is "airport", the program is supposed to show Amman Marka Intl Airport, Adelaide Airport A quote from the assignment specs: "You are to program this application taking efficiency into account as though large amounts of data and processing is involved.." I could easily achieve this functionality using a loop but the performance would be O(n). I was thinking of using a trie but it seems to only work if the substring starts from index 0. I was wondering what solutions are there which gives a performance better than O(n)?

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