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  • singleton vs factory?

    - by fayer
    i've got 3 Log classes that all implements iLog interface: DatabaseLog FileLog ScreenLog there can only be one instance of them. initially i though of using single pattern for each class but then i thought why not use a factory for instantiation instead, cause then i wont have to create single pattern for each one of them and for all future Log classes. and maybe someone would want them as multiple objects in the future. so my questions is: should i use factory or singleton pattern here?

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  • C# Monte Carlo Incremental Risk Calculation optimisation, random numbers, parallel execution

    - by m3ntat
    My current task is to optimise a Monte Carlo Simulation that calculates Capital Adequacy figures by region for a set of Obligors. It is running about 10 x too slow for where it will need to be in production and number or daily runs required. Additionally the granularity of the result figures will need to be improved down to desk possibly book level at some stage, the code I've been given is basically a prototype which is used by business units in a semi production capacity. The application is currently single threaded so I'll need to make it multi-threaded, may look at System.Threading.ThreadPool or the Microsoft Parallel Extensions library but I'm constrained to .NET 2 on the server at this bank so I may have to consider this guy's port, http://www.codeproject.com/KB/cs/aforge_parallel.aspx. I am trying my best to get them to upgrade to .NET 3.5 SP1 but it's a major exercise in an organisation of this size and might not be possible in my contract time frames. I've profiled the application using the trial of dotTrace (http://www.jetbrains.com/profiler). What other good profilers exist? Free ones? A lot of the execution time is spent generating uniform random numbers and then translating this to a normally distributed random number. They are using a C# Mersenne twister implementation. I am not sure where they got it or if it's the best way to go about this (or best implementation) to generate the uniform random numbers. Then this is translated to a normally distributed version for use in the calculation (I haven't delved into the translation code yet). Also what is the experience using the following? http://quantlib.org http://www.qlnet.org (C# port of quantlib) or http://www.boost.org Any alternatives you know of? I'm a C# developer so would prefer C#, but a wrapper to C++ shouldn't be a problem, should it? Maybe even faster leveraging the C++ implementations. I am thinking some of these libraries will have the fastest method to directly generate normally distributed random numbers, without the translation step. Also they may have some other functions that will be helpful in the subsequent calculations. Also the computer this is on is a quad core Opteron 275, 8 GB memory but Windows Server 2003 Enterprise 32 bit. Should I advise them to upgrade to a 64 bit OS? Any links to articles supporting this decision would really be appreciated. Anyway, any advice and help you may have is really appreciated.

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  • Silverlight OOB Application Path Portability

    - by jws
    Silverlight Out-of-browser applications get installed to a seemingly random location: AppData\LocalLow\Microsoft\Silverlight\OutOfBrowser\2333572144.www.microsoft.com for example. Currently, I am simply storing this path, which works perfectly well on a single machine and a single install, but how can I refer to this application between different installations?

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  • android : listview customization

    - by Puneet kaur
    hi, it is possible to have single listview with 2 or more columns ,which is operatable with paging property (i.e. at a time listview will show only 4 items in single column and on press of right arrow it will show next 4 items ).. can u please tell me he procedure to implement it or any idea. Thanks puneet

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  • fastest way to sort the entries of a "smooth" 2D array

    - by Drew Wagner
    What is the fastest way to sort the values in a smooth 2D array? The input is a small filtered image: about 60 by 80 pixels single channel single or double precision float row major storage, sequential in memory values have mixed sign piecewise "smooth", with regions on the order of 10 pixels wide Output is a flat (about 4800 value) array of the sorted values, along with the indices that sort the original array.

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  • Web Apps for Source Code Discussion

    - by Wilco
    Are there any web apps that allow for source code collaboration? I'm thinking of something that could look at an SVN repo/local folder/etc. and publish the code with support for threaded discussions under each file or class. Ideally I want to find something that I could deploy/host myself, so being based in PHP would be a huge plus.

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  • Convert MYSQL Timestamp to time_t

    - by Kewley
    I'm writing a multi-threaded program that needs to be able to check if a row requires updating and act accordingly. I had problems using the built in date/time functions of MySql and so decided to just store the "lastupdate" timestamp as an integer in the table. However, I'm having problems converting this timestamp to time_t so that I can use the time functions with it. Any help is greatly appreciated.

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  • Singleton: How should it be used

    - by Loki Astari
    Edit: From another question I provided an answer that has links to a lot of questions/answers about singeltons: More info about singletons here: So I have read the thread Singletons: good design or a crutch? And the argument still rages. I see Singletons as a Design Pattern (good and bad). The problem with Singleton is not the Pattern but rather the users (sorry everybody). Everybody and their father thinks they can implement one correctly (and from the many interviews I have done, most people can't). Also because everybody thinks they can implement a correct Singleton they abuse the Pattern and use it in situations that are not appropriate (replacing global variables with Singletons!). So the main questions that need to be answered are: When should you use a Singleton How do you implement a Singleton correctly My hope for this article is that we can collect together in a single place (rather than having to google and search multiple sites) an authoritative source of when (and then how) to use a Singleton correctly. Also appropriate would be a list of Anti-Usages and common bad implementations explaining why they fail to work and for good implementations their weaknesses. So get the ball rolling: I will hold my hand up and say this is what I use but probably has problems. I like "Scott Myers" handling of the subject in his books "Effective C++" Good Situations to use Singletons (not many): Logging frameworks Thread recycling pools /* * C++ Singleton * Limitation: Single Threaded Design * See: http://www.aristeia.com/Papers/DDJ_Jul_Aug_2004_revised.pdf * For problems associated with locking in multi threaded applications * * Limitation: * If you use this Singleton (A) within a destructor of another Singleton (B) * This Singleton (A) must be fully constructed before the constructor of (B) * is called. */ class MySingleton { private: // Private Constructor MySingleton(); // Stop the compiler generating methods of copy the object MySingleton(MySingleton const& copy); // Not Implemented MySingleton& operator=(MySingleton const& copy); // Not Implemented public: static MySingleton& getInstance() { // The only instance // Guaranteed to be lazy initialized // Guaranteed that it will be destroyed correctly static MySingleton instance; return instance; } }; OK. Lets get some criticism and other implementations together. :-)

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  • Generic function that accept a table and column name and returns all the primary key values that mat

    - by nashr rafeeg
    i have functions that look like this that is littered through out the code def get_M_status(S): M_id = merital.select(merital.c.marital_status_description == S).execute().fetchone() if M_id == None: print "Warning: No Marital id found for %s Merital status to Single" % S M_id = merital.select(merital.c.marital_status_description == "Single").execute().fetchone() return M_id[0] i was wondering if their is a way to write a generic function where i can pass the relevant values ie: table name primary key column filter column and filter value cheers

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  • Why isn't the reference counter in boost::shared_ptr volatile?

    - by Johann Gerell
    In the boost::shared_ptr destructor, this is done: if(--*pn == 0) { boost::checked_delete(px); delete pn; } where pn is a pointer to the reference counter, which is typedefed as shared_ptr::count_type -> detail::atomic_count -> long I would have expected the long to be volatile long, given threaded usage and the non-atomic 0-check-and-deletion in the shared_ptr destructor above. Why isn't it volatile?

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  • JSF library for Master - Details screen

    - by user305702
    I have a JSF - Spring - iBatis Technical stack I need to create Master Details relationship screen with two level of Master _Details captured in single screen Which JSF library gives support for such requirements ??? Exact Need : Have to create at least 5-6 screens with Header- Line - LineItemDetails - LineTaxDetails - LineXYZDetails in single screen Please help with examples or urls regards Shridhar

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  • How to share connection pool among multiple Java applications

    - by Wilson
    Hi all. I'm implementing several JavaSE applications on single server. Is it possible to setup a single connection pool (e.g. C3P0) and share among these applications? I just want to have an easy way to manage the total number of DB connections. Is there any drawbacks using such centralized connection pool? Thank you, Wilson

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  • Is One Tool or a Suite of Tools Better for Scrum?

    - by Rob Wells
    G'day, Edit: We've been using Scrum very successfully for several years on several projects of varying sizes. In fact, our team developed the successful iPlayer project for the BBC using a classical Scrum approach. After using various combinations of tools, some high-tech, some low-tech, across these projects we now wish to try adopting a suitable tool suite. Our manager is to some extent attempting to force the adoption of a single suite of tools for Scrum. I've looked at the SO question "Best Scrum tools" and most people seem to recommend either: a suite of low-tech solutions, e.g. whiteboards, post-its, index cards, etc., or a monolithic tool that tries to satisfy as much as possible of the process, e.g. Agilo, Mingle, ScrumWorks, Target Process, etc. Our team is currently evaluating several different Scrum tools. However, we are looking at selecting a single, monolithic tool, e.g. Agilo. All of the "one-stop" solutions have their strengths and weaknesses with the serious enterprise type solutions being the best sort of fit. But all have some short comings. After reading the paper "Peer Code Review: An Agile Process" over at SmartBear I started wondering if we were trying to force adoption of a tool on a "best fit" basis. I think you can take a couple of reference artefacts of the Scrum development process, say user stories, epics and themes, and the code base which must use a well-known SCM, e.g. SVN, Hg, etc. Then if we take that as the common reference points for the tools employed then we would be able to use a group of tools to handle the different aspects of the Scrum process rather than try forcing a fit of a single tool would is a bit like forcing a square peg into the round hole. In this way, providing you've agreed your common reference points, you can use several tools, each performing their role better than a could be done by a single component in a monolithic tool suite. Is this a more sensible approach? Are the two reference points I mentioned above suitable, or is their a better choice of points where the tools would meet? cheers,

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  • Dataset to excel

    - by Ruben Monteiro
    Hi. I'm developing an application that as to export a dataset to excel, this dataset have 3 tables and the relation between them, I would like to export this to a single excel sheet where for each parent table there is a '+' sign that when expanded shows the child values related to it. To export a single table to excel I know how to do it, but to create this type of relation I have no idea how to do it, do I have to create a macro on the excel file?

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  • Multi-part question about multi-threading, locks and multi-core processors (multi ^ 3)

    - by MusiGenesis
    I have a program with two methods. The first method takes two arrays as parameters, and performs an operation in which values from one array are conditionally written into the other, like so: void Blend(int[] dest, int[] src, int offset) { for (int i = 0; i < src.Length; i++) { int rdr = dest[i + offset]; dest[i + offset] = src[i] > rdr? src[i] : rdr; } } The second method creates two separate sets of int arrays and iterates through them such that each array of one set is Blended with each array from the other set, like so: void CrossBlend() { int[][] set1 = new int[150][75000]; // we'll pretend this actually compiles int[][] set2 = new int[25][10000]; // we'll pretend this actually compiles for (int i1 = 0; i1 < set1.Length; i1++) { for (int i2 = 0; i2 < set2.Length; i2++) { Blend(set1[i1], set2[i2], 0); // or any offset, doesn't matter } } } First question: Since this apporoach is an obvious candidate for parallelization, is it intrinsically thread-safe? It seems like no, since I can conceive a scenario (unlikely, I think) where one thread's changes are lost because a different threads ~simultaneous operation. If no, would this: void Blend(int[] dest, int[] src, int offset) { lock (dest) { for (int i = 0; i < src.Length; i++) { int rdr = dest[i + offset]; dest[i + offset] = src[i] > rdr? src[i] : rdr; } } } be an effective fix? Second question: If so, what would be the likely performance cost of using locks like this? I assume that with something like this, if a thread attempts to lock a destination array that is currently locked by another thread, the first thread would block until the lock was released instead of continuing to process something. Also, how much time does it actually take to acquire a lock? Nanosecond scale, or worse than that? Would this be a major issue in something like this? Third question: How would I best approach this problem in a multi-threaded way that would take advantage of multi-core processors (and this is based on the potentially wrong assumption that a multi-threaded solution would not speed up this operation on a single core processor)? I'm guessing that I would want to have one thread running per core, but I don't know if that's true.

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  • WPF: Link from grid to form

    - by Ron H
    What I need is a grid with all employees data, and a link to a single employees form. I'm ok with filling the grid with data. my questions are: how to create the link? how to send the parameter (employeeid) to the single-employee page, and make it open with the correct data. Thanks, Ron

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  • List to CSV in Python

    - by Steve
    Hi, I am creating a CSV from a list of values. CSV File gets created but the csv is formed as a single column. Actually it should be multiple rows with multiple columns, instead it forms as a multiple rows with a single column. I am using the following code from random import choice import csv fileObject = csv.writer(open('Insurance.csv','w'),dialect='excel',delimiter=' ') for i in range(0,175): current_list = list(choice(master_list)) fileObject.writerows(current_list) current_list = [] Thanks

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  • How to query through a DBRef in MongoDB/pymongo?

    - by Soviut
    Is it possible to query through a DBRef using a single find spec? user collection { 'age': 30 } post collection { 'user': DBRef('user', ...) } Is it possible to query for all post who's users are 30 in a single find step? If not, would it be wise to create a javascript function to handle the multi-stage operation or will that cause blocking problems?

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  • Windows: Hotkey assistance

    - by Mister X
    Well, I'm wondering is there's any way to link a single key on my keyboard to a file. I wish to execute the file upon pressing the key. I tried using the built in shortcut hotkey system and it didn't work out for me. It really needs to be one single key.

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  • [solved] PHP-called hyperlink stopped showing when CSS table implemented

    - by Luke
    EDIT: Solved - was not flutter's tag stripping, should work as advertised. I'm using Flutter (which creates custom fields) in Wordpress to display profile information entered as a Post. Before I implemented the CSS tables the link showed up and was clickable. Now I get nothing returned, even when I try to call the link outside the table. If you know anything about this, here's my code in the index.php file and I remain available for any questions. <?php if (in_category('Profile')) { ?> <table id="mytable" cellspacing="0"> -snip- <tr> <th class="row1" valign="top">Website </td> <td>Link: <a href="<?php echo get_post_meta($post->ID, 'FrWebsite', $single=true) ?>"> <?php echo get_post_meta($post->ID, 'FrWebsite', $single=true) ?></a></td> </tr> -snip- </table> Thanks, L Edit: @Josh - there is a foreach looping construct in the table and it is reading and displaying the code correctly, I see what you're getting at now: <tr> <th class="row2" valign="top">Specialities </td> <td class="alt" valign="top"><?php $my_array = get('Expertise'); $output = ""; foreach($my_array as $check) { $output .= "<span>$check</span><br/> "; } echo $output; ?></td> </tr> Edit - @Josh - here's the old code as far as I can remember it, there was no major difference just a <td> tag where there now stands a <th>, there wasn't the class="" and there was no "Link:" and FrWebsite was called Website, but it still didn't work when called Website so I changed to see if that was the error. <tr> <td width="200" valign="top">Website </td> <td><a href="<?php echo get_post_meta($post->ID, 'Website', $single=true) ?>"><?php echo get_post_meta($post->ID, 'Website', $single=true) ?></a></td> </tr>

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