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  • Is there a Boost (or other common lib) type for matrices with string keys?

    - by mohawkjohn
    I have a dense matrix where the indices correspond to genes. While gene identifiers are often integers, they are not contiguous integers. They could be strings instead, too. I suppose I could use a boost sparse matrix of some sort with integer keys, and it wouldn't matter if they're contiguous. Or would this still occupy a great deal of space, particularly if some genes have identifiers that are nine digits? Further, I am concerned that sparse storage is not appropriate, since this is an all-by-all matrix (there will be a distance in each and every cell, provided the gene exists). I'm unlikely to need to perform any matrix operations (e.g., matrix multiplication). I will need to pull vectors out of the matrix (slices). It seems like the best type of matrix would be keyed by a Boost unordered_map (a hash map), or perhaps even simply an STL map. Am I looking at this the wrong way? Do I really need to roll my own? I thought I saw such a class somewhere before. Thanks!

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  • How to record different authentication types (username / password vs token based) in audit log

    - by RM
    I have two types of users for my system, normal human users with a username / password, and delegation authorized accounts through OAuth (i.e. using a token identifier). The information that is stored for each is quite different, and are managed by different subsytems. They do however interact with the same tables / data within the system, so I need to maintain the audit trail regardless of whether human user, or token-based user modified the data. My solution at the moment is to have a table called something like AuditableIdentity, and then have the two types inheriting off that table (either in the single table, or as two seperate tables with 1 to 1 PK with AuditableIdentity. All operations would use the common AuditableIdentity PK for CreatedBy, ModifiedBy etc columns. There isn't any FK constraint on the audit columns, so any text can go in there, but I want an easy way to easily determine whether it was a human or system that made the change, and joining to the one AuditableIdentity table seems like a clean way to do that? Is there a best practice for this scenario? Is this an appropriate way of approaching the problem - or would you not bother with the common table and just rely on joins (to the two seperate un-related user / token tables) later to determine which user type matches which audit records?

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  • What do I need to do to make sure my app launches as Admin?

    - by John Gietzen
    I'm writing an app that allows you to script the buttons from a wiimote into actions on your PC. It currently supports all of the features of the main remote control, except for the speaker. Now, I'm running in to trouble when I run it on Vista with UAC turned on. Any time a UAC'd window has focus, my app fails to move the mouse successfully. For instance, when an installer is run, I have to navigate it with the keyboard. Will running the app as administrator solve my problem? (At one point in time, I was able to successfully move the mouse over a UAC-password-entry box) How do I build a manifest that will tell windows to "run as administrator"? How do I embed this manifest into my app, if I'm strongly naming my assembly? How do I sign my application with an Authenticode cert? EDIT: Ok, so after some more extensive research, I have found: http://msdn.microsoft.com/en-us/library/bb756929.aspx <requestedExecutionLevel level="asInvoker|highestAvailable|requireAdministrator" uiAccess="true|false"/> However, the article says: Applications with the uiAccess flag set to true must be Authenticode signed to start properly. In addition, the application must reside in a protected location in the file system. \Program Files\ and \windows\system32\ are currently the two allowable protected locations. I have edited the question to reflect the new developments.

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  • An unusual type signature

    - by Travis Brown
    In Monads for natural language semantics, Chung-Chieh Shan shows how monads can be used to give a nicely uniform restatement of the standard accounts of some different kinds of natural language phenomena (interrogatives, focus, intensionality, and quantification). He defines two composition operations, A_M and A'_M, that are useful for this purpose. The first is simply ap. In the powerset monad ap is non-deterministic function application, which is useful for handling the semantics of interrogatives; in the reader monad it corresponds to the usual analysis of extensional composition; etc. This makes sense. The secondary composition operation, however, has a type signature that just looks bizarre to me: (<?>) :: (Monad m) => m (m a -> b) -> m a -> m b (Shan calls it A'_M, but I'll call it <?> here.) The definition is what you'd expect from the types; it corresponds pretty closely to ap: g <?> x = g >>= \h -> return $ h x I think I can understand how this does what it's supposed to in the context of the paper (handle question-taking verbs for interrogatives, serve as intensional composition, etc.). What it does isn't terribly complicated, but it's a bit odd to see it play such a central role here, since it's not an idiom I've seen in Haskell before. Nothing useful comes up on Hoogle for either m (m a -> b) -> m a -> m b or m (a -> b) -> a -> m b. Does this look familiar to anyone from other contexts? Have you ever written this function?

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  • Outgoing UDP sniffer in python?

    - by twneale
    I want to figure out whether my computer is somehow causing a UDP flood that is originating from my network. So that's my underlying problem, and what follows is simply my non-network-person attempt to hypothesize a solution using python. I'm extrapolating from recipe 13.1 ("Passing Messages with Socket Datagrams") from the python cookbook (also here). Would it possible/sensible/not insane to try somehow writing an outgoing UDP proxy in python, so that outgoing packets could be logged before being sent on their merry way? If so, how would one go about it? Based on my quick research, perhaps I could start a server process listening on suspect UDP ports and log anything that gets sent, then forward it on, such as: import socket s =socket.socket(socket.AF_INET, socket.SOCK_DGRAM) s.bind(("", MYPORT)) while True: packet = dict(zip('data', 'addr'), s.recvfrom(1,024)) log.info("Recieved {data} from {addr}.".format(**packet)) But what about doing this for a large number of ports simultaneously? Impractical? Are there drawbacks or other reasons not to bother with this? Is there a better way to solve this problem (please be gentle).

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  • How can I add a portrait layout on top of a landscape Camera SurfaceView?

    - by user319919
    I need a Camera SurfaceView for my application. The camera should be set to fixed landscape view which is done by setting android:screenOrientation="landscape" for the activity in the AndroidManifest.xml. After doing some experiments and Google researches trying to use setRotation(int) inside the camera preview implementation, I came to the conclusion, that it is obviously the common practice to get a preview with correct behaviour. Now the camera preview itself looks fine for landscape orientation. But I need to have an overlay that holds a bunch of buttons. Due to usability the user interface should be in portrait view (or even better orientation aware). There seemed no other option to me, but to fix the activity screenOrientation, so that the camera preview looks normal (in portrait mode the whole view is streched and rotated to the left) Is there a workaround to get my buttons back to portrait orientation? Or another overall approach to deal with the camera view? Parameters.setRotation(int) obvisouly didnt work. I am quite new to the Android plattform programming. Of course I dont know much about the programming tricks and workarounds yet. I did a lot of research over the last two weeks, but couldnt find the right solution so far.

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  • Generics vs inheritance (whenh no collection classes are involved)

    - by Ram
    This is an extension of this questionand probably might even be a duplicate of some other question(If so, please forgive me). I see from MSDN that generics are usually used with collections The most common use for generic classes is with collections like linked lists, hash tables, stacks, queues, trees and so on where operations such as adding and removing items from the collection are performed in much the same way regardless of the type of data being stored. The examples I have seen also validate the above statement. Can someone give a valid use of generics in a real-life scenario which does not involve any collections ? Pedantically, I was thinking about making an example which does not involve collections public class Animal<T> { public void Speak() { Console.WriteLine("I am an Animal and my type is " + typeof(T).ToString()); } public void Eat() { //Eat food } } public class Dog { public void WhoAmI() { Console.WriteLine(this.GetType().ToString()); } } and "An Animal of type Dog" will be Animal<Dog> magic = new Animal<Dog>(); It is entirely possible to have Dog getting inherited from Animal (Assuming a non-generic version of Animal)Dog:Animal Therefore Dog is an Animal Another example I was thinking was a BankAccount. It can be BankAccount<Checking>,BankAccount<Savings>. This can very well be Checking:BankAccount and Savings:BankAccount. Are there any best practices to determine if we should go with generics or with inheritance ?

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  • Strange EListError occurance (when accessing variable-defined index)

    - by michal
    Hi, I have a TList which stores some objects. Now I have a function which does some operations on that list: function SomeFunct(const AIndex: integer): IInterface begin if (AIndex > -1) and (AIndex < fMgr.Windows.Count ) then begin if (fMgr.Windows[AIndex] <> nil) then begin if not Supports(TForm(fMgr.Windows[AIndex]), IMyFormInterface, result) then result:= nil; end; end else result:= nil; end; now, what is really strange is that accessing fMgr.Windows with any proper index causes EListError... However if i hard-code it (in example, replace AIndex with value 0 or 1) it works fine. I tried debugging it, the function gets called twice, with arguments 0 and 1 (as supposed). while AIndex = 0, evaluating fMgr.Windows[AIndex] results in EListError at $someAddress, while evaluating fMgr.Windws[0] instead - returns proper results ... what is even more strange, even though there is an EListError, the function returns proper data ... and doesn't show anything. Just info on two EListError memory leaks on shutdown (using FastMM) any ideas what could be wrong?! Thanks in advance michal

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  • Need Help with wxPython & pyGame

    - by Xavier
    Hi Guys, I'm actually in need of your help and advice here on my assignment that I am working on. First of all, I was task to do a program that runs langton's ant simulation. For that, I've managed to get the source code (from snippets.dzone.com/posts/show/5143) and edited it accordingly to my requirements. This was done and ran in pygame module extension. In addition, my task requires a GUI to interface for users to run and navigate through the screens effectively with the langton's ant program running. I used wxPython with the help of an IDE called BOA constructor to create the frames, buttons, textboxes, etc. Basically, all the stuff needed in the interfaces. However, I've ran into some problems listed below: Found problem integrating pyGame with wxPython. On this note, I've research the internet for answers and tutorials where I found out from website: wiki.wxpython.org/IntegratingPyGame & aspn.activestate.com/ASPN/Mail/Message/wxpython-users/3178042. I understand from the sites that integrating pyGame with wxPython will be a difficult task where it has caused common problems like the inability to placing other controls into the frames as the pyGame application will cover the entire panel. I really hope that you can clarify my doubts on this and advise me on the path that I should take from here. Therefore, I ask the following questions: Is it feasible to integrate pyGame with wxPython? If it is not feasible to integrate pyGame with wxPython, what other alternatives do I have to create a GUI interface integrating pyGame into it. If so how do I go about? If it is possible to go about integrating pyGame with wxPython, how do I go about doing so? Really need you guys opinion on this.

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  • Help me avoid a resonance cascade.

    - by SLC
    Hi, my name is Dr. Kleiner, and I'm a senior scientist working at the Black Mesa Research Facility. I've just finished compiling my code to analyse a large unknown sample we've come across. Unfortunately, there were 19 build errors and 42 warnings, but I've been told the experiment must go ahead. Time is critical, we've already got one of our newest employees who is suiting up as I type this to complete the experiment. I really need some help. Can you think of anything last minute to stop a potential resonance cascade? Someone has hidden my glasses again... Anyway, I hope I never see a resonance cascade, and definitely don't want to create one. It's my lunch break in 5 minutes, and my casserole is already in the microwave ready. Please, give me some advice. If it helps I wrote all of the code to analyse the sample and activate the sampler machine in BASIC. Edit: Oh god! They're everywhere! Send assista

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  • Pass a data.frame column name to a function

    - by Kevin Middleton
    I'm trying to write a function to accept a data.frame (x) and a column from it. The function performs some calculations on x and later returns another data.frame. I'm stuck on the best-practices method to pass the column name to the function. The two minimal examples fun1 and fun2 below produce the desired result, being able to perform operations on x$column, using max() as an example. However, both rely on the seemingly (at least to me) inelegant (1) call to substitute() and possibly eval() and (2) the need to pass the column name as a character vector. fun1 <- function(x, column){ do.call("max", list(substitute(x[a], list(a = column)))) } fun2 <- function(x, column){ max(eval((substitute(x[a], list(a = column))))) } df <- data.frame(A = 1:20, B = rnorm(10)) fun1(df, "B") fun2(df, "B") I would like to be able to call the function as fun(df, B), for example. Other options I have considered but have not tried: Pass column as an integer of the column number. I think this would avoid substitute(). Ideally, the function could accept either. with(x, get(column)), but, even if it works, I think this would still require substitute Make use of formula() and match.call(), neither of which I have much experience with. Subquestion: Is do.call() preferred over eval()? Thanks, Kevin

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  • Old desktop programmer wants to create S+S project

    - by Craig
    I have an idea for a product that I want to be web-based. But because I live in Brasil, the internet is not always available so there needs to be a desktop component that is available for when the internet is down. Also, I have been a SQL programmer, a desktop application programmer using dBase, VB and Pascal, and I have created simple websites using HTML and website creation tools, such as Frontpage. So from my research, I think I have the following options; PHP, Ruby on Rails, Python or .NET for the programming side. MySQL for the DB. And Apache, or possibly IIS, for the webserver. I will probably start with a local ISP provider for the cloud servce. But then maybe move to something more "robust" and universal in the future, ie. Amazon, or Azure, or something along that line. My question then is this. What would you recommend for something like this? I'm sure that I have not listed all of the possibilities, but the ones I have researched and thought of. Thanks everyone, Craig

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  • PHP CodeIgniter Framework - Thoughts on developing with it?

    - by Sootah
    I've been reviewing different frameworks to use for my next couple of major web applications, and after days of research am almost set on using CodeIgniter. The reason I'm leaning towards CI is that so far it looks to be the best suited for me. It doesn't require constant command-line access (I am currently using shared hosting; the projects do not warrant a dedicate server yet), nothing special has to be installed on the server running it (you just upload the framework to the root of whatever your developing), and they appear to have some excellent documentation, videos, and tutorials on how to get started. Do any of you have experience with CodeIgniter? If so, what is your opinion of it and its features? What had you developed with it, and what types of applications is it best suited to create? I certainly don't want to get into a situation where I'm trying to bend a framework to do something that it isn't well-suited for. Both of my projects will be database-driven apps that will require user registration, the ability to manipulate data that is specific to their account (their posts, listings, user account details, etc), amongst other things. Also, if you have any other PHP framework suggestions, I am open to them. Thanks in advance for your help! -Sootah

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  • Fast Lightweight Image Comparisson Metric Algorithm

    - by gav
    Hi All, I am developing an application for the Android platform which contains 1000+ image filters that have been 'evolved'. When a user selects a photo I want to present the most relevant filters first. This 'relevance' should be dependent on previous use cases. I have already developed tools that register when a filtered image is saved; this combination of filter and image can be seen as the training data for my system. The issue is that the comparison must occur between selecting an image and the next screen coming up. From a UI point of view I need the whole process to take less that 4 seconds; select an image- obtain a metric to use for similarity - check against use cases - return 6 closest matches. I figure with 4 seconds I can use animations and progress dialogs to keep the user happy. Due to platform contraints I am fairly limited in the computational expense of the algorithm. I have implemented a technique adapted from various online tutorials for running C code on the G1 and hence this language is available Specific Constraints; Qualcomm® MSM7201A™, 528 MHz Processor 320 x 480 Pixel bitmap in 32 bit ARGB ~ 2 seconds computational time for the native method to get the metric ~ 2 seconds to compare the metric of the current image with training data This is an academic project so all ideas are welcome, anything you can think of or have heard about would be of interest to me. My ideas; I want to keep the complexity down (O(n*m)?) by using pixel data only rather than a neighbourhood function I was looking at using the Colour historgram/Greyscale histogram/Texture/Entropy of the image, combining them to make the measure. There will be an obvious loss of information but I need the resultant metric to be substantially smaller than the memory footprint of the image (~0.512 MB) As I said, any ideas to direct my research would be fantastic. Kind regards, Gavin

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  • Upload An Excel File in Classic ASP On Windows 2003 x64 Using Office 2010 Drivers

    - by alphadogg
    So, we are migrating an old web app from a 32-bit server to a newer 64-bit server. The app is basically a Classic ASP app. The pool is set to run in 64-bit and cannot be set to 32-bit due to other components. However, this breaks the old usage of Jet drivers and subsequent parsing of Excel files. After some research, I downloaded the 64-bit version of the new 2010 Office System Driver Beta and installed it. Presumably, this allows one to open and read Excel and CSV files. Here's the snippet of code that errors out. Think I followed the lean guidelines on the download page: Set con = Server.CreateObject("ADODB.Connection") con.ConnectionString = "Provider=Microsoft.ACE.OLEDB.14.0;Data Source=" & strPath & ";Extended Properties=""Excel 14.0;""" con.Open Any ideas why? UPDATE: My apologies. I did forget the important part, the error message: ADODB.Connection error '800a0e7a' Provider cannot be found. It may not be properly installed. /vendor/importZipList2.asp, line 56 I have installed, and uninstalled/reinstalled twice.

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  • Why is OCR(MODI.MiLANGUAGES.miLANG_ENGLISH, true, true) causing an OCR running error?

    - by Ian Wells
    Hi folks, I am using MODI to read tiff images and do what I need to do with the text. Some images work fine and then other tiff images always cause the method, OCR(MODI.MiLANGUAGES.miLANG_ENGLISH, true, true) to fail. I have researched this and tried different variations such as 'false','false' in the parameter list. I have also tried SYSDEFAULT instead of English but I still get the error. Can anyone please tell me why it would fail on some tiff images and not on others? I have done some research and found this answer: One possible cause is MODI trying to process a file without any recognisable text. A blank document, or one which has only drawings/scribbles and is effectively blank, will cause this exception. Obviously this is not good enough as there is no way I can have an app that decides to OCR some images and not others. I handle the exception, but the OCR object is not then initalised so I can't do what I need to do from there. This is a bloody nightmare! Why can't the method just do it's bloody job and if the image has some unreadable pages then just ignore them? I am using Windows 7 Ultimate and Office 2007 Ultimate. Visual Studio version is 2008 Thanks, IW

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  • Having an issue with org.hibernate.SessionException: Session is closed! in Hibernate

    - by hal10001
    I've done quite a bit a research on this with no luck, but all the answers have a tendency to point toward the session context settings in the config file. What is odd is that I get a session connection the very first time I hit the page (and therefore, a successful result set), but then when I reload I get the following exception: org.hibernate.SessionException: Session is closed! Here are my config settings that are not DB connection string related: <property name="hibernate.show_sql">false</property> <property name="hibernate.dialect">org.hibernate.dialect.SQLServerDialect</property> <property name="hibernate.current_session_context_class">thread</property> <property name="hibernate.cache.provider_class">org.hibernate.cache.NoCacheProvider</property> <property name="hibernate.cache.use_query_cache">false</property> <property name="hibernate.cache.use_minimal_puts">false</property> Here is an example of a call I make that produces the situation I described above. public T get(int id) { session.beginTransaction(); T type; try { type = getTypeClass().cast(session.get(getTypeClass(), id)); } catch (ClassCastException classCastException) { throw new ClassCastException(classCastException.getMessage()); } session.getTransaction().commit(); return type; } The session variable reference is to a static field that contains the current session. All of the session connection details are textbook reference manual. For example, here is my Hibernate session utility: import org.hibernate.SessionFactory; import org.hibernate.cfg.Configuration; public class HibernateSessionFactoryUtil { private static final SessionFactory sessionFactory = buildSessionFactory(); private static SessionFactory buildSessionFactory() { try { return new Configuration().configure().buildSessionFactory(); } catch (Throwable ex) { System.err.println("Initial SessionFactory creation failed." + ex); throw new ExceptionInInitializerError(ex); } } public static SessionFactory getSessionFactory() { return sessionFactory; } }

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  • Building a custom (dynamic) dataset and grid

    - by marko.ivanovski.nz
    Hi, I'm in the process of building a dynamic table in which you can add/remove rows & columns so it varies in size depending on what the user wants. Its purpose is to store properties for a product, but there can be from 1 to 10 different properties(columns) per product, and multiple instances(rows) of the product as well. Here's a screenshot of what I mean http://i40.tinypic.com/nbqkxc.jpg As you can see I need the structure to be completely up to the client which is where I'm getting stuck. I've started writing a custom DataSet that has "add column" & "add row" buttons, and have built a custom Table with Textboxes in each cell which builds from that dataset. I have no idea how to store the data on submit though, and to make it even more complex I need to store this in the database as a string which I think I can do by converting it to XML. Any help is appreciated, I think I just need a pointer in the right direction and am happy to do research from there. Thanks in advance. Marko

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  • How to draw an unfilled square on top of a stream video using a mouse and track the object enclosed

    - by Haxed
    Hi, I am making an object tracking application. I have used Emgucv 2.1.0.0 to load a video file to a picturebox. I have also taken the video stream from a web camera. Now, I want to draw an unfilled square on the video stream using a mouse and then track the object enclosed by the unfilled square as the video continues to stream. This is what people have suggested so far:- (1) .NET Video overlay drawing(DirectX) - but this is for C++ users, the suggester said that there are .NET wrappers, but I had a hard time finding any. (2) DxLogo sample DxLogo – A sample application showing how to superimpose a logo on a data stream. It uses a capture device for the video source, and outputs the result to a file. Sadly, this does not use a mouse. (3) GDI+ and mouse handling - this area I do not have a clue. And for tracking the object in the square, I would appreciate if someone give me some research paper links to read. Any help as to using the mouse to draw on a video is greatly appreciated. Thank you for taking the time to read this. Many Thanks

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  • How to override the default init.tcl

    - by Sean Murphy
    I'm working on a project where I want to make use of TCL as the command interpreter. I have a working c library object which I can load from within the tcl shell but my problem is finding a way to automatically do this while starting a tclsh. Essentially my ultimate goal is to be able to run a script and have it load my library and run some initial startup tcl code before dropping me back to the tclsh command prompt in interactive mode. e.g. tclsh -f myscript.tcl --then-switch-to-interactive or EXPORT TCLINIT=myscript.tcl tclsh The basic goal is to avoid having to distribute tclsh but rather rely in local user installations of tcl. All I would like to distribute is my library, a startup script and a shell command to launch the tclsh with the library preloaded. I've tried using the environment variables TCLINIT and TCL_LIBRARY but they seem to have no effect. The only workable solutions I've found so far are to add "source myscript.tcl" to either the end of /usr/share/tcltk/tcl8.5.init.tcl or ~/.tclshrc However both of these "solutions" are non perfect as they require modification of the default users workspace. It strikes me that there must be a way to handle this in TCL, but my research so far hasn't yielded anything. Does anyone have any suggestions?

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  • Mysql Server Optimization

    - by Ish Kumar
    Hi Geeks, We are having serious MySQL(InnoDB) performance issues at a moment when we do: (10-20) insertions on TABLE1 (10-20) updates on TABLE2 Note: Both above operations happens within fraction of a second. And this occurs every few (10-15) minutes. And all online users (approx 400-600) doing read operation on join of TABLE1 & TABLE2 every 1 second. Here is our mysql configuration info: http://docs.google.com/View?id=dfrswh7c_117fmgcmb44 Issues: Lot queries wait and expire later (saw it from phpmyadmin / processes). My poor MySQL server crashes sometimes Questions Q1: Any suggestions to optimize at MySQL level? Q2: I thinking to use persistent connections at application level, is it right? Info Added Later: Database Engine: InnoDB TABLE1 : 400,000 rows (inserting 8,000 daily) & TABLE2: 8,000 rows 1 second query: SELECT b.id, b.user_id, b.description, b.debit, b.created, b.price, u.username, u.email, u.mobile FROM TABLE1 b, TABLE2 u WHERE b.credit = 0 AND b.user_id = u.id AND b.auction_id = "12345" ORDER BY b.id DESC LIMIT 10; // there are few more but they are not so critical. Indexing is good, we are using them wisely. In above query all id's are indexed And TABLE1 has frequent insertions and TABLE2 has frequent updates.

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  • Is it possible to write map/reduce jobs for Amazon Elastic MapReduce using .NET?

    - by Chris
    Is it possible to write map/reduce jobs for Amazon Elastic MapReduce (http://aws.amazon.com/elasticmapreduce/) using .NET languages? In particular I would like to use C#. Preliminary research suggests not. The above URL's marketing text suggests you have a "choice of Java, Ruby, Perl, Python, PHP, R, or C++", without mentioning .NET languages. This Amazon thread (http://developer.amazonwebservices.com/connect/thread.jspa?messageID=136051 -- "Support for C# / F# map/reducers") explicitly says that "currently Amazon Elastic MapReduce does not support Mono platform or languages such as C# or F#." The above suggests that it can't be done. I'm wondering if there are any workarounds, though. For example, can I modify the Elastic MapReduce machine image for my account, and install Mono on there? An alternative, suggested by Amazon FAQs "Using Other Software Required by Your Jar" (http://docs.amazonwebservices.com/ElasticMapReduce/latest/DeveloperGuide/index.html?CHAP_AdvancedTopics.html) and "How to Use Additional Files and Libraries With the Mapper or Reducer" (http://docs.amazonwebservices.com/ElasticMapReduce/latest/DeveloperGuide/index.html?addl_files.html), is to make the first step of the Map/Reduce job be to install Mono on the local instance. That sounds kind of inefficient, but maybe it could work? Maybe a saner alternative would be to try to forgo the convenience of Elastic MapReduce, and manually set up my own Hadoop cluster on EC2. Then I assume I could install Mono without difficulty.

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  • Reconstructing trees from a "fingerprint"

    - by awshepard
    I've done my SO and Google research, and haven't found anyone who has tackled this before, or at least, anyone who has written about it. My question is, given a "universal" tree of arbitrary height, with each node able to have an arbitrary number of branches, is there a way to uniquely (and efficiently) "fingerprint" arbitrary sub-trees starting from the "universal" tree's root, such that given the universal tree and a tree's fingerprint, I can reconstruct the original tree? For instance, I have a "universal" tree (forgive my poor illustrations), representing my universe of possibilities: Root / / / | \ \ ... \ O O O O O O O (Level 1) /|\/|\...................\ (Level 2) etc. I also have tree A, a rooted subtree of my universe Root / /|\ \ O O O O O / Etc. Is there a way to "fingerprint" the tree, so that given that fingerprint, and the universal tree, I could reconstruct A? I'm thinking something along the lines of a hash, a compression, or perhaps a functional/declarative construction? Big-O analysis (in time or space) is a plus. As a for-instance, a nested expression like: {{(Root)},{(1),(2),(3)},{(2,3),(1),(4,5)}...} representing the actual nodes present at each level in the tree is probably valid, but can it be done more efficiently?

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  • Understanding F# Asynchronous Programming

    - by Yin Zhu
    I kind of know the syntax of asynchronous programming in F#. E.g. let downloadUrl(url:string) = async { let req = HttpWebRequest.Create(url) // Run operation asynchronously let! resp = req.AsyncGetResponse() let stream = resp.GetResponseStream() // Dispose 'StreamReader' when completed use reader = new StreamReader(stream) // Run asynchronously and then return the result return! reader.AsyncReadToEnd() } In F# expert book (and many other sources), they say like let! var = expr simply means "perform the asynchronous operation expr and bind the result to var when the operation completes. Then continue by executing the rest of the computation body" I also know that a new thread is created when performing async operation. My original understanding was that there are two parallel threads after the async operation, one doing I/O and one continuing to execute the async body at the same time. But in this example, I am confused at let! resp = req.AsyncGetResponse() let stream = resp.GetResponseStream() What happens if resp has not started yet and the thread in the async body wants to GetResponseStream? Is this a possible error? So maybe my original understanding was wrong. The quoted sentences in the F# expert book actually means that "creating a new thread, hang the current thread up, when the new thread finishes, wake up the body thread and continue", but in this case I don't see we could save any time. In the original understanding, the time is saved when there are several independent IO operations in one async block so that they could be done at the same time without intervention with each other. But here, if I don't get the response, I cannot create the stream; only I have stream, I can start reading the stream. Where's the time gained?

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  • jqGrid : "All in One" approach width jqGridEdit Class > how to set a composite primary key ?

    - by Qualliarys
    Hello, How to set a composite primary key for a "All in One" approach (grid defined in JS file, and data using jqGridEdit Class in php file) ? Please, for me a composite primary key of a table T, is a elementary primary key that is defined with some fields belong to this table T ! Here is my test, but i get no data and cannot use the CRUD operations : In my JS file i have this lines code: ... colModel":[ {"name":"index","index":"index","label":"index"}, // <= THAT'S JUST THE INDEX OF MY TABLE {"name":"user","index":"user","label":"user","key":true}, // <= A PART OF MY COMPOSITE PRIMARY KEY {"name":"pwd","index":"pwd","label":"pwd","key":true}, // <= A PART OF MY COMPOSITE PRIMARY KEY {"name":"state","index":"state","label":"state","key":true}, // <= A PART OF MY COMPOSITE PRIMARY KEY ... <= AND SO ON "url":"mygrid_crud.php", "datatype":"json", "jsonReader":{repeatitems:false}, "editurl": "mygrid_crud.php", "prmNames":{"id":"index"} // <= WHAT I NEED TO WRITE HERE ??? ... In my php file (mygrid_crud.php) : ... $grid = new jqGridEdit($conn); $query = "SELECT * FROM mytable WHERE user='$user' and pwd='$pwd' and state='$state'..."; // <= SELECT * it's ok or i need to specify all fields i need ? $grid->SelectCommand = $query; $grid->dataType = "json"; $grid->table = 'mytable'; $grid->setPrimaryKeyId('index'); // <= WHAT I NEED TO WRITE HERE ??? ... $grid->editGrid(); Please, say me what is wrong, and how to do to set a composite primary key in this approach !? Thank you so much for tour responses.

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