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  • Moving Javascript object with all bounded events to other variable

    - by Saif Bechan
    Let's say I have an anchor tag, with some events. <a id="clickme" href="/endpoint">clickme</a> <a id="clickme2" href="/endpoint2">clickme2</a> Let's use jquery for simplicity: $('#clickme').on('click', function(){.....}) I also have a variable: var myActiveVar = $('#clickme'); When I want to remove the element an every trace of it I can do this: myActiveVar.off().remove(); Here comes the problem, I want to reuse the variable. Something like this: var oldAcriveVar = myActiveVar; myActiveVar = $('#clickme2'); // Now I want to do some operations // both of the elements are still on // the page, when I'm done: oldActiveVar.off().remove(); Comeplete code: var myActiveVar = $('#clickme'); // Operate on myActiveVar var oldAcriveVar = myActiveVar; myActiveVar = $('#clickme2'); // Operate on myActiveVar which is // the new element. // Old element stays visible oldActiveVar.off().remove(); // Old element and all traces are gone Edit: Maybe the above code will work, but my problem goes beyond. I just gave a simplified example. I am using Backbone events that are bounded to object. They need to be removed when I am done with the object.

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  • Is it legal to take sealed .NET framework class source and extend it?

    - by Giedrius
    To be short, I'm giving very specific example, but I'm interested in general situation. There is a FtpWebRequest class in .NET framework and it is missing some of new FTP operations, like MFCT. It is ok in a sense that this operation is still in draft mode, but it is not ok in a sense, that FtpWebRequest is sealed and there's no other way (at least I don't see it) to extend it with this new operation. Easiest way to do it would be take FtpWebRequest class source from .NET reference sources and extend it, in such way will be kept all the consistence in naming, implementation, etc. Question is how much legal it is? I won't sell this class as a product, I can publish my changes on web - nothing to hide here. If it is not legal, can I take this class source from mono and include in native .net project? Did you had similar case and how you solved it? Update: as long as extension method is offered, I'm pasting source from .NET framework which should show that extension methods are not the solution. So there's a property Method, where you can pass FTP command: public override string Method { get { return m_MethodInfo.Method; } set { if (String.IsNullOrEmpty(value)) { throw new ArgumentException(SR.GetString(SR.net_ftp_invalid_method_name), "value"); } if (InUse) { throw new InvalidOperationException(SR.GetString(SR.net_reqsubmitted)); } try { m_MethodInfo = FtpMethodInfo.GetMethodInfo(value); } catch (ArgumentException) { throw new ArgumentException(SR.GetString(SR.net_ftp_unsupported_method), "value"); } } } As you can see there FtpMethodInfo.GetMethodInfo(value) call in setter, which basically validates value against internal enum static array. Update 2: Checked mono implementation and it is not exact replica of native code + it does not implement some of the things.

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  • Memory mapping of files and system cache behavior in WinXP

    - by Canopus
    Our application is memory intensive and deals with reading a large number of disk files. The total load can be more than 3 GB. There is a custom memory manager that uses memory mapped files to achieve reading of such a huge data. The files are mapped into the process memory space only when needed and with this the process memory is well under control. But what is observed is, with memory mapping, the system cache keeps on increasing until it occupies the available physical memory. This leads to the slowing down of the entire system. My question is how to prevent system cache from hogging the physical memory? I attempted to remove the file buffering (by using FILE_FLAG_NO_BUFFERING ), but with this, the read operations take considerable amount of time and slows down the application performance. How to achieve the scalability without sacrificing much on performance. What are the common techniques used in such cases? I dont have a good understanding of the WinXP OS caching behavior. Any good links explaining the same would also be helpful.

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  • Is it possible to load an entire SQL Server CE database into RAM?

    - by DanM
    I'm using LinqToSql to query a small SQL Server CE database. I've noticed that any operations involving sub-properties are disappointingly slow. For example, if I have a Customer table that is referenced by an Order table via a foreign key, LinqToSql will automatically create an EntitySet<Order> property. This is a nice convenience, allowing me to do things like Customer.Order.Where(o => o.ProductName = "Stopwatch"), but for some reason, SQL Server CE hangs up pretty bad when I try to do stuff like this. One of my queries, which isn't really that complicated takes 3-4 seconds to complete. I can get the speed up to acceptable, even fast, if I just grab the two tables individually and convert them to List<Customer> and List<Order>, then join then manually with my own query, but this is throwing out a lot of the appeal of LinqToSql. So, I'm wondering if I can somehow get the whole database into RAM and just query that way, then occasionally save it. Is this possible? How? If not, is there anything else I can do to boost the performance? Note: My database in its initial state is about 250K and I don't expect it to grow to more than 1-2Mb. So, loading the data into RAM certainly wouldn't be a problem from a memory point of view.

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  • JavaCard monitoring folder

    - by GxG
    I want to write a two way application: applet for javacard and an application in C#. I've got the C# covered but i want to know if with JavaCard i can monitor a folder on the memory and how would i go about doing that. I have a shared folder let's call it temp in which i want to store buffer information between the simulated smartcard and the C# application. The C# application will only read from that folder and display the information, but also it will write requests towards the smartcard. For example i simulate entering the PIN for the card. The applet will write a file containing available options and the C# application will read that file and display those options; from the C# app i will chose and option and write a request file in the same folder. This is when the smartcard which is monitoring that folder will read the request and issue a response. Can i make the smartcard monitor that folder? I was thinking of using encrypted XML files for the request/response operations. But simple .txt files are good to. I am limited to using JavaCard v2.2.1, and every operation has to be encrypted/decrypted. (with the ciphering i have no problem)

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  • Trouble tunneling my local Wordpress install to the mysql database on appfog

    - by alanmoo
    I've set up a wordpress install on appfog (using rackspace), and cloned the install to my local machine for development. I know the install works (using MAMP) because I created a local mysql database and changed wp-config.php to point to it. However, I want to develop without having to change wp-config.php every time I commit. After doing some research, it seems like the Appfog service Caldecott lets me tunnel into the mysql database on the server, using af tunnel. Unfortunately, I'm having issues with getting it working. Even if I change my MAMP mysql port to something like 8889, and tunnel mysql through port 3306, it looks like it's connected but I still get "Error establishing a database connection" when loading my localhost Wordpress. When I quit the mysql monitor (using ctrl+x, ctrl+c), I get a message stating "Error: 'mysql' execution failed; is it in your $PATH?'. Originally, no, it wasn't, but I've fixed my PATH variable on my local machine so that when I go to Terminal and just type mysql, it loads up. So I guess my question is 2 parts: 1.)Am I going with the right approach for Wordpress development on my local machine and 2.)If so, why is the tunnel not working?

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  • Create table and call it from sql

    - by user1770816
    I have a PL/SQL function which creates a new temporary table. For creating the table I use execute immediate. When I run my function in oracle sql developer everything is ok; the function creates the temp table without errors. But when U use SQL: Select function_name from table_name I get an exceptions: ORA-14552: cannot perform a DDL, commit or rollback inside a query or DML ORA-06512: at "SYSTEM.GET_USERS", line 10 14552. 00000 - "cannot perform a DDL, commit or rollback inside a query or DML " *Cause: DDL operations like creation tables, views etc. and transaction control statements such as commit/rollback cannot be performed inside a query or a DML statement. Update Sorry, write from tablet PC and have problems with format text. My function: CREATE OR REPLACE FUNCTION GET_USERS ( USERID IN VARCHAR2 ) RETURN VARCHAR2 AS request VARCHAR2(520) := 'CREATE GLOBAL TEMPORARY TABLE '; BEGIN request := request || 'temp_table_' || userid || '(user_name varchar2(50), user_id varchar2(20), is_administrator varchar2(5)') || ' ON COMMIT PRESERVE ROWS'; EXECUTE IMMEDIATE (request); RETURN 'true'; END GET_USERS;

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  • Strange results about C++11 memory model (Relaxed ordering)

    - by Dancing_bunny
    I was testing the example in the memory model of the Anthony Williams's book "C++ Concurrency" #include<atomic> #include<thread> #include<cassert> std::atomic_bool x,y; std::atomic_int z; void write_x_then_y() { x.store(true, std::memory_order_relaxed); y.store(true, std::memory_order_relaxed); } void read_y_then_x() { while(!y.load(std::memory_order_relaxed)); if(x.load(std::memory_order_relaxed)) { ++z; } } int main() { x = false; y = false; z = 0; std::thread a(write_x_then_y); std::thread b(read_y_then_x); a.join(); b.join(); assert(z.load()!=0); } According to the explanation, relaxed operations on difference variables (here x and y) can be freely reordered. However, I repeated running the problem for more than several days. I never hit the situation that the assertion (assert(z.load()!=0);) fires. I just use the default optimization and compile the code using g++ -std=c++11 -lpthread dataRaceAtomic.cpp Does anyone actually try it and hit the assertion? Could anyone give me an explanation about my test results? BTW, I also tried the version without using the atomic type, I got the same result. Currently, both programs are running healthily. Thanks.

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  • Interesting Scala typing solution, doesn't work in 2.7.7?

    - by djc
    I'm trying to build some image algebra code that can work with images (basically a linear pixel buffer + dimensions) that have different types for the pixel. To get this to work, I've defined a parametrized Pixel trait with a few methods that should be able to get used with any Pixel subclass. (For now, I'm only interested in operations that work on the same Pixel type.) Here it is: trait Pixel[T <: Pixel[T]] { def mul(v: Double): T def max(v: T): T def div(v: Double): T def div(v: T): T } Now I define a single Pixel type that has storage based on three doubles (basically RGB 0.0-1.0), I've called it TripleDoublePixel: class TripleDoublePixel(v: Array[Double]) extends Pixel[TripleDoublePixel] { var data: Array[Double] = v def this() = this(Array(0.0, 0.0, 0.0)) def toString(): String = { "(" + data(0) + ", " + data(1) + ", " + data(2) + ")" } def increment(v: TripleDoublePixel) { data(0) += v.data(0) data(1) += v.data(1) data(2) += v.data(2) } def mul(v: Double): TripleDoublePixel = { new TripleDoublePixel(data.map(x => x * v)) } def div(v: Double): TripleDoublePixel = { new TripleDoublePixel(data.map(x => x / v)) } def div(v: TripleDoublePixel): TripleDoublePixel = { var tmp = new Array[Double](3) tmp(0) = data(0) / v.data(0) tmp(1) = data(1) / v.data(1) tmp(2) = data(2) / v.data(2) new TripleDoublePixel(tmp) } def max(v: TripleDoublePixel): TripleDoublePixel = { val lv = data(0) * data(0) + data(1) * data(1) + data(2) * data(2) val vv = v.data(0) * v.data(0) + v.data(1) * v.data(1) + v.data(2) * v.data(2) if (lv > vv) (this) else v } } Now I want to write code to use this, that doesn't have to know what type the pixels are. For example: def idiv[T](a: Image[T], b: Image[T]) { for (i <- 0 until a.data.size) { a.data(i) = a.data(i).div(b.data(i)) } } Unfortunately, this doesn't compile: (fragment of lindet-gen.scala):145: error: value div is not a member of T a.data(i) = a.data(i).div(b.data(i)) I was told in #scala that this worked for someone else, but that was on 2.8. I've tried to get 2.8-rc1 going, but it doesn't compile for me. Is there any way to get this to work in 2.7.7?

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  • RIA Service/oData ... "Requests that attempt to access a single element using key values from a resu

    - by user327911
    I've recently started working up a sample project to play with an oData feed coming from a RIA service. I am able to view the feed and the metadata via any web browser, however, if I try to perform certain query operations on the feed I receive "unsupported" exceptions. Sample oData feed: ProductSet http://localhost:50880/Services/Rebirth-Web-Services-ProductService.svc/OData/ProductSet/ 2010-04-28T14:02:10Z http://localhost:50880/Services/Rebirth-Web-Services-ProductService.svc/OData/ProductSet(guid'b0a2b170-c6df-441f-ae2a-74dd19901128') 2010-04-28T14:02:10Z b0a2b170-c6df-441f-ae2a-74dd19901128 Product 0 Type 1 Active Sample web.config entry: Sample service: [EnableClientAccess()] public class ProductService : DomainService { [Query(IsDefault = true)] public IQueryable GetProducts() { IList products = new List(); for (int i = 0; i < 90; i++) { Product product = new Product { Id = Guid.NewGuid(), Name = "Product " + i.ToString(), ProductType = i < 30 ? "Type 1" : ((i > 30 && i < 60) ? "Type 2" : "Type 3"), Status = i % 2 == 0 ? "Active" : "NotActive" }; products.Add(product); } return products.AsQueryable(); } } If I provide the url "http://localhost:50880/Services/Rebirth-Web-Services-ProductService.svc/OData/ProductSet(guid'b0a2b170-c6df-441f-ae2a-74dd19901128')" to my web browser I receive the following xml: Requests that attempt to access a single element using key values from a result set are not supported. I'm new to RIA and oData. Could this be something as simple as my web browsers not supporting this type of querying on the result set or something else? Thanks ahead! Corey

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  • WCF consumed as WebService adds a boolean parameter?

    - by Martín Marconcini
    I've created the default WCF Service in VS2008. It's called "Service1" public class Service1 : IService1 { public string GetData( int value ) { return string.Format("You entered: {0}", value); } public CompositeType GetDataUsingDataContract( CompositeType composite ) { if ( composite.BoolValue ) { composite.StringValue += "Suffix"; } return composite; } } It works fine, the interface is IService1: [ServiceContract] public interface IService1 { [OperationContract] string GetData( int value ); [OperationContract] CompositeType GetDataUsingDataContract( CompositeType composite ); // TODO: Add your service operations here } This is all by default; Visual Studio 2008 created all this. I then created a simple Winforms app to "test" this. I added the Service Reference to my the above mentioned service and it all works. I can instanciate and call myservice1.GetData(100); and I get the result. But I was told that this service will have to be consumed by a Winforms .NET 2.0 app via Web Services, so I proceeded to add the reference to a new Winforms .NET 2.0 application created from scratch (only one winform called form1). This time, when adding the "web reference", it added the typical "localhost" one belonging to webservices; the wizard saw the WCF Service (running on background) and added it. When I tried to consume this, I found out that the GetData(int) method, was now GetData(int, bool). Here's the code private void button1_Click( object sender, EventArgs e ) { localhost.Service1 s1 = new WindowsFormsApplication2.localhost.Service1(); Console.WriteLine(s1.GetData(100, false)); } Notice the false in the GetData call? I don't know what that parameter is or where did that come from, it is called "bool valueSpecified". Does anybody know where this is coming from? Anything else I should do to consume a WCF Service as a WebService from .NET 2.0? (winforms).

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  • MSI File/Registry failures on Windows Server 2008/Windows 7 (x64)

    - by Luca
    I'm trying to deploy an application on Windows Server 2008 (SP2 x64) and Windows 7 (x64), using VS2005 Installer Project. The MSI version (I think) it the 2.0. Everything works fine, except that some registry keys and some files are not copied on the install machine. The MSI system doesn't notify about nothing (and I don't know whether MSI logs its operations). Are there incompatibilities between my MSI installer project and these new OSes? It seems to me that the OS protect itself for being modified in some part. For example, I'm trying to set the registry keys: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\WinLogon\SpecialAccounts\UserList\User but it is not created. In the same installer there are many other keys, which are created like expected (as they always did before on Windows XP and Windows Server 2003). To provide another example, I'm trying to install the file %SystemFolder%\oobe\info\backgrounds\backgroundDefault.jpg (where %SystemFolder% is typically "C:\Windows\System32"), but the file is not copied at all!!! What's going on? I've found the backgroundDefault.jpg file is located in another directory: %SystemRoot%\SysWOW64\oobe\info. But I've not specified nothing about a System (64 bit) folder. How can I copy the file in the right place?

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  • Windows Workflow Foundation 4.0 Designer Rehosting with Custom Activities

    - by Robert
    I have several WF 4.0 workflows that I have created for an application my company is developing. Some of these workflows are simple, and some are very complex (i.e. many steps, several different types of activities, custom activities). For many of these workflows, I have created several custom code activities to support some internal process types. The workflows work great and we have had very few problems when it comes to maintaining them within VS 2010. We now want to move that responsibility off to our business users, so I have created a WPF application to rehost the WF designer (according to the MS samples). My problem is that when I open one of the workflows that contains custom code activities, those activities are represented as red boxes with the error message of "Activity could not be loaded because of errors in XAML." I have done research and have found several posts that mention that this is usually a problem with namespacing and referencing. The rehosted designer is in a namespace similar to this: Company.Application.Workflow.Designer And the custom code activities are contained within a separate custom workflow library, which I have included as a reference in the designer project. The library's namespace is similar to this: Company.Application.Workflow.Data.Activities As I have mentioned, the library is set as a reference in the designer's project, and I see it being copied to the output when I build the project. I have also included the reference in the XAML of the main designed application. What am I missing?

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  • Exemplars of large document-centric applications with COM/XPCOM/.NET interfaces.

    - by Warren P
    I am looking for exemplars (design examples) showing the use of interfaces (aka 'protocols' for you smalltalkers) to design a document management architecture in a large Word Processor, Spreadsheet, vector graphic or publishing package, or office-productivity (non-database) application with support for as many of the following as possible: any open source project, will be ideal, and language of implementation is unimportant since I am looking for design examples, however an object oriented language with support for "interfaces" is a must. I know at least a dozen languages, and I'm willing to study any application's source. use of "interface" could loosely be applied to either XPCOM or COM interfaces, or .NET interfaces, or even the use of pure-virtual (virtual+abstract) base-classes for OOP languages that lack the ability to declare an interface distinct from a class. I am mostly looking for a robust, thorough and flexible implementation for a document, IDocument, various document views (IDocumentView), and whatever operations make sense in that case. I am particular interested in cases where the product in question is a real-world product. For example, if anybody familiar with OpenOffice can tell me if the code contains a good sample design. I am looking for design documentation that outlines the design of the interfaces for such an application. So for example, if the openoffice spreadsheet has such an interface design, then that might be the best case, because it is a widely used real-world design, with millions of users, rather than a textbook example, which is minimal, and contrived. I know that the Mozilla platform uses XPCOM, and its design is heavily "interface" oriented, but I am looking more for a "word processor" or "spreadsheet" type of document design, rather than a web-browser. I am particularly interested in the interfaces used to access to data and meta-data such as markup (attributes like bold, and italics, and font size), and the ability to search and look up named entities within a document.

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  • Tree iterator, can you optimize this any further?

    - by Ron
    As a follow up to my original question about a small piece of this code I decided to ask a follow up to see if you can do better then what we came up with so far. The code below iterates over a binary tree (left/right = child/next ). I do believe there is room for one less conditional in here (the down boolean). The fastest answer wins! The cnt statement can be multiple statements so lets make sure this appears only once The child() and next() member functions are about 30x as slow as the hasChild() and hasNext() operations. Keep it iterative <-- dropped this requirement as the recursive solution presented was faster. This is C++ code visit order of the nodes must stay as they are in the example below. ( hit parents first then the children then the 'next' nodes). BaseNodePtr is a boost::shared_ptr as thus assignments are slow, avoid any temporary BaseNodePtr variables. Currently this code takes 5897ms to visit 62200000 nodes in a test tree, calling this function 200,000 times. void processTree (BaseNodePtr current, unsigned int & cnt ) { bool down = true; while ( true ) { if ( down ) { while (true) { cnt++; // this can/will be multiple statesments if (!current->hasChild()) break; current = current->child(); } } if ( current->hasNext() ) { down = true; current = current->next(); } else { down = false; current = current->parent(); if (!current) return; // done. } } }

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  • What C# container is most resource-efficient for existence for only one operation?

    - by ccornet
    I find myself often with a situation where I need to perform an operation on a set of properties. The operation can be anything from checking if a particular property matches anything in the set to a single iteration of actions. Sometimes the set is dynamically generated when the function is called, some built with a simple LINQ statement, other times it is a hard-coded set that will always remain the same. But one constant always exists: the set only exists for one single operation and has no use before or after it. My problem is, I have so many points in my application where this is necessary, but I appear to be very, very inconsistent in how I store these sets. Some of them are arrays, some are lists, and just now I've found a couple linked lists. Now, none of the operations I'm specifically concerned about have to care about indices, container size, order, or any other functionality that is bestowed by any of the individual container types. I picked resource efficiency because it's a better idea than flipping coins. I figured, since array size is configured and it's a very elementary container, that might be my best choice, but I figure it is a better idea to ask around. Alternatively, if there's a better choice not out of resource-efficiency but strictly as being a better choice for this kind of situation, that would be nice as well.

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  • Automatically Organize Tags in Tax/Folksonomy

    - by Rob Wilkerson
    I'm working on a process that will perform natural language processing (NLP) on one--and potentially several--of our content rich sites. What I'd like to do once the NLP is complete is to automatically organize the output (generally a set of terms that you might think of as tags given the prevalence of that metaphor) into some kind of standard or generally accepted organizational structure. In a perfect world, I'd really like this to be crowd sourced under the folksonomy concept (as opposed to a taxonomy) since the ultimate goal is to target/appeal to real people rather than "domain experts", but I'm open to ideas and best practices. For the obvious purpose of scalability, I'd like to automate the population of this tax/folksonomy so that "some guy" in the team/organization isn't responsible for looking at a bunch of words (with or without context) and arbitrarily fleshing out the contextual components of the tree. I have a few ideas for doing this that require some research to establish viability, but I have exactly zero practical experience with this sort of thing so the ideas really just boil down to stuff I made up that might perform some role in accomplishing the task. Imagining that others have vastly more experience with this sort of thing, I'm hoping that I can stand on your shoulders. Thanks for your thoughts and insights.

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  • How to get the real, actual duration of an MP3 file (VBR or CBR) server-side

    - by Cummander Checkov
    I used to calculate the duration of MP3 files server-side using ffmpeg - which seemed to work fine. Today i discovered that some of the calculations were wrong. Somehow, for some reason, ffmpeg will miscalculate the duration and it seems to happen with variable bit rate mp3 files only. When testing this locally, i noticed that ffmpeg printed two extra lines in green. Command used: ffmpeg -i song_9747c077aef8.mp3 ffmpeg says: [mp3 @ 0x102052600] max_analyze_duration 5000000 reached at 5015510 [mp3 @ 0x102052600] Estimating duration from bitrate, this may be inaccurate After a nice, warm google session, i found some posts on this, but no solution was found. I then tried to increase the maximum duration: ffmpeg -analyzeduration 999999999 -i song_9747c077aef8.mp3 After this, ffmpeg returned only the second line: [mp3 @ 0x102052600] Estimating duration from bitrate, this may be inaccurate But in either case, the calculated duration was just plain wrong. Comparing it to VLC i noticed that here the duration is correct. After more research i stumbled over mp3info - which i installed and used. mp3info -p "%S" song_9747c077aef8.mp3 mp3info then returned the CORRECT duration, but only as an integer, which i cannot use as i need a more accurate number here. The reason for this was explained in a comment below, by user blahdiblah - mp3info is simply pulling ID3 info from the file and not actually performing any calculations. I also tried using mplayer to retrieve the duration, but just as ffmpeg, mplayer is returning the wrong value. Now i ran out of options. If somebody knows how to get around this, any hints, tips, guides or corrections are welcome! Thank You!

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  • Creating simple calculator with bison & flex in C++ (not C)

    - by ak91
    Hey, I would like to create simple C++ calculator using bison and flex. Please note I'm new to the creating parsers. I already found few examples in bison/flex but they were all written in C. My goal is to create C++ code, where classes would contain nodes of values, operations, funcs - to create AST (evaluation would be done just after creating whole AST - starting from the root and going forward). For example: my_var = sqrt(9 ** 2 - 32) + 4 - 20 / 5 my_var * 3 Would be parsed as: = / \ my_var + / \ sqrt - | / \ - 4 / / \ / \ ** 32 20 5 / \ 9 2 and the second AST would look like: * / \ my_var 3 Then following pseudocode reflects AST: ast_root = create_node('=', new_variable("my_var"), exp) where exp is: exp = create_node(OPERATOR, val1, val2) but NOT like this: $$ = $1 OPERATOR $3 because this way I directly get value of operation instead of creation the Node. I believe the Node should contain type (of operation), val1 (Node), val2 (Node). In some cases val2 would be NULL, like above mentioned sqrt which takes in the end one argument. Right? It will be nice if you can propose me C++ skeleton (without evaluation) for above described problem (including *.y file creating AST) to help me understand the way of creating/holding Nodes in AST. Code can be snipped, just to let me get the idea. I'll also be grateful if you point me to an existing (possibly simple) example if you know any. Thank you all for your time and assistance!

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  • Caching vector addition over changing collections

    - by DRMacIver
    I have the following setup: I have a largish number of uuids (currently about 10k but expected to grow unboundedly - they're user IDs) and a function f : id - sparse vector with 32-bit integer values (no need to worry about precision). The function is reasonably expensive (not outrageously so, but probably on the order of a few 100ms for a given id). The dimension of the sparse vectors should be assumed to be infinite, as new dimensions can appear over time, but in practice is unlikely to ever exceed about 20k (and individual results of f are unlikely to have more than a few hundred non-zero values). I want to support the following operations efficiently: add a new ID to the collection invalidate an existing ID retrieve sum f(id) in O(changes since last retrieval) i.e. I want to cache the sum of the vectors in a way that's reasonable to do incrementally. One option would be to support a remove ID operation and treat invalidation as a remove followed by an add. The problem with this is that it requires us to keep track of all the old values of f, which is expensive in space. I potentially need to use many instances of this sort of cached structure, so I would like to avoid that. The likely usage pattern is that new IDs are added at a fairly continuous rate and are frequently invalidated at first. Ids which have been invalidated recently are much more likely to be invalidated again than ones which have remained valid for a long time, but in principle an old Id can still be invalidated. Ideally I don't want to do this in memory (or at least I want a way that lets me save the result to disk efficiently), so an idea which lets me piggyback off an existing DB implementation of some sort would be especially appreciated.

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  • GUI for server-client program

    - by sksingh73
    I am making a server-client application in c++. In this i am also using shared memory & file read-write operations. my program is completely ready & i now wants to make a gui for it. someone suggested me to go for QT4, but when i tried it, i found i have to re-write 80% of the code because QT has got its own classes & variable. i don't want to do it. i want suggestions from you on this regard. my requirements for gui are very simple i.e there will be a main form, which will have two text boxes in which all messages being sent & received by client & server should be shown. there should be another lineedit box, through which i can send the messages to the other end server. I don't know how to make this gui. someone suggested tcl/tk, other suggested me use php/swig. i am not sure how to go about this. my only requirement is that i want to make this simple gui with minimum of changes in my code. THANX

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  • Checked and Unchecked operators don't seem to be working when...

    - by flockofcode
    1) Is UNCHECKED operator in effect only when expression inside UNCHECKED context uses an explicit cast ( such as byte b1=unchecked((byte)2000); ) and when conversion to particular type can happen implicitly? I’m assuming this since the following expression throws a compile time error: byte b1=unchecked(2000); //compile time error 2) a) Do CHECKED and UNCHECKED operators work only when resulting value of an expression or conversion is of an integer type? I’m assuming this since in the first example ( where double type is being converted to integer type ) CHECKED operator works as expected: double m = double.MaxValue; b=checked((byte)m); // reports an exception , while in second example ( where double type is being converted to a float type ) CHECKED operator doesn’t seem to be working. since it doesn't throw an exception: double m = double.MaxValue; float f = checked((float)m); // no exception thrown b) Why don’t the two operators also work with expressions where type of a resulting value is of floating-point type? 2) Next quote is from Microsoft’s site: The unchecked keyword is used to control the overflow-checking context for integral-type arithmetic operations and conversions I’m not sure I understand what exactly have expressions and conversions such as unchecked((byte)(100+200)); in common with integrals? Thank you

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  • How should I lock the table in this VB6 / Access application?

    - by Brian Hooper
    I'm working on a VB6 application using an Access database. The application writes messages to a log table from time to time. Several instances of the application may be running simultaneously and to distinguish them they each have their own run number. The run number is deduced from the log table thus... Set record_set = New ADODB.Recordset query_string = "SELECT MAX(RUN_NUMBER) + 1 AS NEW_RUN_NUMBER FROM ERROR_LOG" record_set.CursorLocation = adUseClient record_set.Open query_string, database_connection, adOpenStatic, , adCmdText record_set.MoveLast If IsNull(record_set.Fields("NEW_RUN_NUMBER")) Then run_number = 0 Else run_number = record_set.Fields("NEW_RUN_NUMBER") End If command_string = "INSERT INTO ERROR_LOG (RUN_NUMBER, SEVERITY, MESSAGE) " & _ " VALUES (" & Str$(run_number) & ", " & _ " " & Str$(SEVERITY_INFORMATION) & ", " & _ " 'Run Started'); " database_connection.Execute command_string Obviously there is a small gap between the calculation of the run number and the appearance of the new row in the database, and to prevent another instance getting access between the two operations I'd like to lock the table; something along the lines of SET TRANSACTION READ WRITE RESERVING ERROR_LOG FOR PROTECTED WRITE; How should I go about doing this? Would locking the recordset do any good (the row in the record set doesn't match any particular row in the database)?

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  • What's a good way to write batch scripts in C#?

    - by Scott Bilas
    I would like to write simple scripts in C#. Stuff I would normally use .bat or 4NT .btm files for. Copying files, parsing text, asking user input, and so on. Fairly simple but doing this stuff right in a batch file is really hard (no exceptions for example). I'm familiar with command line "scripting" wrappers like AxScript so that gets me part of the way there. What I'm missing is the easy file-manipulation framework. I want to be able to do cd(".."), copy(srcFile, destFile) type functionality. Tools I have tried: NANT, which we use in our build process. Not a good scripting tool. Insanely verbose XML syntax and to add a simple function you must write an extension assembly. Can't do it inline. PowerShell. Looks great, but I just haven't been able to switch over to this as my primary shell. Too many differences from 4NT. Whatever I do needs to run from an ordinary command prompt and not require a special shell to run it through. Can PowerShell be used as a script executor? Perl/Python/Ruby. Really hate learning an entirely new language and framework just to do batch file operations. Haven't been able to dedicate the time I need to do this. Plus, we're a 99% .NET shop for our toolchain and I really want to leverage our existing experience and codebase. Are there frameworks out there that are trying to solve this problem of "make a batch file in C#" that you have used? I want the power of C#/.NET with the immediate-mode type functionality of a typical cmd.exe shell language. Am I alone in wanting something like this?

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  • Better way to compare neighboring cells in matrix

    - by HyperCube
    Suppose I have a matrix of size 100x100 and I would like to compare each pixel to its direct neighbor (left, upper, right, lower) and then do some operations on the current matrix or a new one of the same size. A sample code in Python/Numpy could look like the following: (the comparison 0.5 has no meaning, I just want to give a working example for some operation while comparing the neighbors) import numpy as np my_matrix = np.random.rand(100,100) new_matrix = np.array((100,100)) my_range = np.arange(1,99) for i in my_range: for j in my_range: if my_matrix[i,j+1] > 0.5: new_matrix[i,j+1] = 1 if my_matrix[i,j-1] > 0.5: new_matrix[i,j-1] = 1 if my_matrix[i+1,j] > 0.5: new_matrix[i+1,j] = 1 if my_matrix[i-1,j] > 0.5: new_matrix[i-1,j] = 1 if my_matrix[i+1,j+1] > 0.5: new_matrix[i+1,j+1] = 1 if my_matrix[i+1,j-1] > 0.5: new_matrix[i+1,j-1] = 1 if my_matrix[i-1,j+1] > 0.5: new_matrix[i-1,j+1] = 1 This can get really nasty if I want to step into one neighboring cell and start from it to do a similar task... Do you have some suggestions how this can be done in a more efficient manner? Is this even possible?

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