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  • Displaying shifts on a timetable/calendar using C#

    - by Dave Peters
    I am very much a beginner and have experience of SQL and a tiny amount of VBA. What I am looking to do is create a tool to pull shift times from a database and to display them on a timetable/calendar. It will be part of a desktop application that the (very tech illiterate) end users will use to view and amend shift patterns. In essence it will be a grid with days on one axis and people on the other (I would however like to have the blocks proportional to shift length). In my mind it would potentially be a simple Gantt chart. All computing stuff I’ve learnt has been through trial and error and I want to use this project to get a much better understanding of C# as well as to get to the end product. I have been reading around for ways to tackle the problem and my issue is creating the timetable framework to which I will bind the data. I am using Visual Studio 2010 and SQL Server 2008 R2. Do you know of good resources which will either start me on the road to designing my own interface or give a basic framework I can adapt? All the resources I’ve found so far have been in different languages or for web based applications. Thank you for your time.

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  • Non-Relational Database Design

    - by Ian Varley
    I'm interested in hearing about design strategies you have used with non-relational "nosql" databases - that is, the (mostly new) class of data stores that don't use traditional relational design or SQL (such as Hypertable, CouchDB, SimpleDB, Google App Engine datastore, Voldemort, Cassandra, SQL Data Services, etc.). They're also often referred to as "key/value stores", and at base they act like giant distributed persistent hash tables. Specifically, I want to learn about the differences in conceptual data design with these new databases. What's easier, what's harder, what can't be done at all? Have you come up with alternate designs that work much better in the non-relational world? Have you hit your head against anything that seems impossible? Have you bridged the gap with any design patterns, e.g. to translate from one to the other? Do you even do explicit data models at all now (e.g. in UML) or have you chucked them entirely in favor of semi-structured / document-oriented data blobs? Do you miss any of the major extra services that RDBMSes provide, like relational integrity, arbitrarily complex transaction support, triggers, etc? I come from a SQL relational DB background, so normalization is in my blood. That said, I get the advantages of non-relational databases for simplicity and scaling, and my gut tells me that there has to be a richer overlap of design capabilities. What have you done? FYI, there have been StackOverflow discussions on similar topics here: the next generation of databases changing schemas to work with Google App Engine choosing a document-oriented database

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  • Required Working Precision for the BBP Algorithm?

    - by brainfsck
    Hello, I'm looking to compute the nth digit of Pi in a low-memory environment. As I don't have decimals available to me, this integer-only BBP algorithm in Python has been a great starting point. I only need to calculate one digit of Pi at a time. How can I determine the lowest I can set D, the "number of digits of working precision"? D=4 gives me many correct digits, but a few digits will be off by one. For example, computing digit 393 with precision of 4 gives me 0xafda, from which I extract the digit 0xa. However, the correct digit is 0xb. No matter how high I set D, it seems that testing a sufficient number of digits finds an one where the formula returns an incorrect value. I've tried upping the precision when the digit is "close" to another, e.g. 0x3fff or 0x1000, but cannot find any good definition of "close"; for instance, calculating at digit 9798 gives me 0xcde6 , which is not very close to 0xd000, but the correct digit is 0xd. Can anyone help me figure out how much working precision is needed to calculate a given digit using this algorithm? Thank you,

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  • Function approximation with Maclaurin series

    - by marines
    I need to approx (1-x)^0.25 with given accuracy (0.0001 e.g.). I'm using expansion found on Wikipedia for (1+x)^0.25. I need to stop approximating when current expression is less than the accuracy. long double s(long double x, long double d) { long double w = 1; long double n = 1; // nth expression in series long double tmp = 1; // sum while last expression is greater than accuracy while (fabsl(tmp) >= d) { tmp *= (1.25 / n - 1) * (-x); // the next expression w += tmp; // is added to approximation n++; } return w; } Don't mind long double n. :P This works well when I'm not checking value of current expression but when I'm computing 1000 or more expressions. Domain of the function is <-1;1 and s() calculates approximation well for x in <-1;~0.6. The bigger the argument is the bigger is the error of calculation. From 0.6 it exceeds the accuracy. I'm not sure if the problem is clear enough because I don't know English math language well. The thing is what's the matter with while condition and why the function s() doesn't approximate correctly.

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  • OleDbExeption Was unhandled in VB.Net

    - by ritch
    Syntax error (missing operator) in query expression '((ProductID = ?) AND ((? = 1 AND Product Name IS NULL) OR (Product Name = ?)) AND ((? = 1 AND Price IS NULL) OR (Price = ?)) AND ((? = 1 AND Quantity IS NULL) OR (Quantity = ?)))'. I need some help sorting this error out in Visual Basics.Net 2008. I am trying to update records in a MS Access Database 2008. I have it being able to update one table but the other table is just not having it. Private Sub Admin_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load 'Reads Users into the program from the text file (Located at Module.VB) ReadUsers() 'Connect To Access 2007 Database File con.ConnectionString = ("Provider=Microsoft.ACE.OLEDB.12.0;" & "Data Source=E:\Computing\Projects\Login\Login\bds.accdb;") con.Open() 'SQL connect 1 sql = "Select * From Clients" da = New OleDb.OleDbDataAdapter(sql, con) da.Fill(ds, "Clients") MaxRows = ds.Tables("Clients").Rows.Count intCounter = -1 'SQL connect 2 sql2 = "Select * From Products" da2 = New OleDb.OleDbDataAdapter(sql2, con) da2.Fill(ds, "Products") MaxRows2 = ds.Tables("Products").Rows.Count intCounter2 = -1 'Show Clients From Database in a ComboBox ComboBoxClients.DisplayMember = "ClientName" ComboBoxClients.ValueMember = "ClientID" ComboBoxClients.DataSource = ds.Tables("Clients") End Sub The button, the error appears on da2.update(ds, "Products") Private Sub Button4_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button4.Click Dim cb2 As New OleDb.OleDbCommandBuilder(da2) ds.Tables("Products").Rows(intCounter2).Item("Price") = ProductPriceBox.Text da2.Update(ds, "Products") 'Alerts the user that the Database has been updated MsgBox("Database Updated") End Sub However the code works on updating another table Private Sub UpdateButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles UpdateButton.Click 'Allows users to update records in the Database Dim cb As New OleDb.OleDbCommandBuilder(da) 'Changes the database contents with the content in the text fields ds.Tables("Clients").Rows(intCounter).Item("ClientName") = ClientNameBox.Text ds.Tables("Clients").Rows(intCounter).Item("ClientID") = ClientIDBox.Text ds.Tables("Clients").Rows(intCounter).Item("ClientAddress") = ClientAddressBox.Text ds.Tables("Clients").Rows(intCounter).Item("ClientTelephoneNumber") = ClientNumberBox.Text 'Updates the table withing the Database da.Update(ds, "Clients") 'Alerts the user that the Database has been updated MsgBox("Database Updated") End Sub

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  • How to completely wipe a previous ClickOnce installation?

    - by Dabblernl
    I have a curious problem: My app is distributed through ClickOnce. I recently installed three new clients on a new location. They worked. After an update however, all old clients worked fine, but the three new clients did not. As my code is swallowing an exception somewhere I have been unable thusfar to pinpoint where the error lies. When I XCopy the latest version of the app to the desktop of the three new client computers the program works fine. So, I thought uninstalling and reinstalling the program from the download location should fix the problem, but it does not! I can think of two explanations: The new location has some firewall/virusscanner in place that doesn't like the latest version of my app when it is run from a standard ClickOnce directory, but it allows execution from the desktop. Some old settings (the app uses user scoped and app scoped settings) remain in effect after the uninstall. When I find and check the user.config file for the app however, I find no incorrect setttings there. Thusfar, I have been unable to reproduce the error on any other machine. How can I solve this!?

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  • how to better (inambiguaously) use the terms CAPTCHA and various types of interactions?

    - by vgv8
    I am working on survey of state-of-the-art and trends of spam prevention techniques. I observe that non-intrusive, transparent to visitor spam prevention techniques (like context-based filtering or honey traps) are frequently called non-captcha. Is it correct understanding of term CAPTCHA which is "type of challenge-response [ 2 ]test used in computing to ensure that the response is not generated by a compute" [ 1 ] and challenge-response does not seem to imply obligatory human involvement. So, which understanding (definition) of term and classification I'd better to stick with? How would I better call CAPTCHA without direct human interaction in order to avoid ambiguity and confusion of terms understnding? How would I better (succinctly and unambiguously) coin the term for captchas requiring human interaction but without typing into textbox? How would I better (succinctly and unambiguously) coin the terms to mark the difference between human interaction with images (playing, drag&dropping, rearranging, clicking with images) vs. just recognizing them (and then typing into a textbox the answer without interaction with images)? PS. The problem is that recognition of a wiggled word in an image or typing the answer to question is also interaction and when I start to use the terms "interaction", "interactive", "captcha", "protection", "non-captcha", "non-interactive", "static", "dynamic", "visible", "hidden" the terms overlap ambiguously with which another (especailly because the definitions or their actual practice of usage are vague or contradictive). [ 1 ] http://en.wikipedia.org/wiki/CAPTCHA

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  • How to build n-layered web architecture with PHP?

    - by Alex
    I have a description and design of a website and I need to redesign it to allow for new requirements. The website's purpose is the offering of government's contracts and bidding opportunities for different businesses.I'm dealing with the 3-tier architecture PHP website comprising of the user-interface tier(client's web browser),business logic layer(Apache web server with PHP engine in it and a couple of applications running within a web server as well) and a database layer(local mysql database). Now,i need to redesign it to su???rt distributed n-tier architecture and specify how I would go about it.After long hours of research i came to this solution: business logic should be separated into presentation and purely business logic tier to allow for n-layer architecture(user-interface,presentation tier,b.logic and data tier).I have decided to use ??? just for the presentation(since the original existing website is in PHP) and use it within apache web server.In the business logic i want to use J2?? implementation technology instead of implementing it in PHP(i.e using Zend app.server and smarty template) cz J2EE can provide much more essential container services which are essential for business logic,its robustness,maintainability and different critical business operations which will be carried out by the g?v?rnment's website.So,particularly,i want to use J??ss app.server with ?J? business objects in it which would provide all the b.logic in java and would interact with the database and so forth.In order to connect PHP on a web server with java on app.server i'm gonna use PHP/Java bridge API (or maybe Quercus or SOAP is better?).Finally,i have my data tier with mysql which will communicate with b.logic via JD??.Payment system application in ???.server is gonna use S??? to talk with credit card company. From your professional point of view,does it sound like a good way of redesigning the original website to allow for n-tier architecture considering the specifics of the website and the criticality of its operations?(payment system is included in it)or u would personally prefer to use PHP business objects for business logic as well instead of J2EE?If you have any wiser recommendation or some alternative,please let me know what is right or wrong in my current solution. H??? to hear your professional advice very s??n (I'm new to the area of web development) Thanks in advance

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  • Which Database to choose?

    - by Sundar
    I have the following criteria Database should be protected with a username and password. It should not be possible to copy the database file and use it else were like MS Access. There will be no central database server. Each machine will run their own database server locally and user will initiate synchronization. Concept is inspired from distributed version control system like Git. So it should have good replication support. Strong consistency is not needed. Users will synchronize each other database when they need. In case of conflicts it should be possible to find the conflict and present it (from application) to the user for fixing it. Revisions of data if available it will be good. e.g. Entire history of change to a invoice. I explored document oriented database and inclined towards the same. But I dont know what to choose. Database is small it will not reach even 1GB in the next few years (say 3 years). Please feel free to suggest any database which you think might be suitable. Any pointers is highly appreciated. Thanks in advance.

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  • Has Twisted changed its dependencies?

    - by cdecker
    Hi all, I'm currently working on a Python/Twisted project which is to be distributed and tested on Planetlab. For some reason my code was working on friday and now that I wanted to test a minor change it refuses to work at all: Traceback (most recent call last): File "acn_a4/src/node.py", line 6, in <module> from twisted.internet.protocol import DatagramProtocol File "/usr/lib/python2.5/site-packages/Twisted-10.0.0-py2.5-linux-i686.egg/twisted/__init__.py", line 18, in <module> from twisted.python import compat File "/usr/lib/python2.5/site-packages/Twisted-10.0.0-py2.5-linux-i686.egg/twisted/python/compat.py", line 146, in <module> import operator File "/home/cdecker/dev/acn/acn_a4/src/operator.py", line 7, in <module> File "/home/cdecker/acn_a4/src/node.py", line 6, in <module> from twisted.internet.protocol import DatagramProtocol File "/usr/lib/python2.5/site-packages/Twisted-10.0.0-py2.5-linux-i686.egg/twisted/internet/protocol.py", line 20, in <module> from twisted.python import log, failure, components File "/usr/lib/python2.5/site-packages/Twisted-10.0.0-py2.5-linux-i686.egg/twisted/python/log.py", line 19, in <module> from twisted.python import util, context, reflect File "/usr/lib/python2.5/site-packages/Twisted-10.0.0-py2.5-linux-i686.egg/twisted/python/util.py", line 5, in <module> import os, sys, hmac, errno, new, inspect, warnings File "/usr/lib/python2.5/inspect.py", line 32, in <module> from operator import attrgetter ImportError: cannot import name attrgetter And since I'm pretty new to python I have no idea what could have caused this problem. All suggestions are welcome :-)

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  • Managing common components with Fossil CVS

    - by Larry Lustig
    I'm a Fossil (and CVS configuration novice) attempting to create and manage a set of distributed Fossil repositories for a Delphi project. I have the following directory tree: Projects Some Project Delphi Components LookupListView Some Client Some Project For Client Some Other Project For Client Source Code Project Resources Project Database I am setting up Fossil version control in order to version and share Projects\Some Client\Some Other Project For Client\Source Code, which contains Delphi 2010 source for a database project. This project makes use of Projects\Delphi Components\LookupListView which is a Delphi component. I need this code to be included in the versioning system for my project. I will, in theory, need to include it in other Fossil repositories in the future, as well. If I create my Fossil repository at the Source Code or Some Other Project For Client level, I cannot add any code above that level to my repository. What is the proper way to deal with this? The two solutions that occur to me are 1) Creating a separate repository for LookupListView and make sure that everyone who uses a repository for a project that references it "knows" that they must also get the current version of this project as well. This seems to defeat the purpose of being able to obtain a complete, current version of the project with a single checkout. The problem is magnified because there are other common component dependencies in this project. 2) Establishing my Fossil repository in the Projects directory, so I can check in files from various subfolders. This seems to me to involve an awful lot of extra path-typing when doing adds, and also to impose my directory structure (Some Client\Some Other Project For Client\Source) on the other users of the repository -- in this case, the actual client. Any suggestions appreciated.

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  • Optimized Publish/Subcribe JMS Broker Cluster and Conflicting Posts on StackOverFlow for the Answer

    - by Gene
    Hi, I am looking to build a publish/subscribe distributed messaging framework that can manage huge volumes of message traffic with some intelligence at the broker level. I don't know if there's a topology that describes this, but this is the model I'm going after: EXAMPLE MODEL A A) There are two running message brokers (ideally all on localhost if possible, for easier demo-ing) : Broker-A Broker-B B) Each broker will have 2 listeners and 1 publisher. Example Figure [subscriber A1, subscriber A2, publisher A1] <-- BrokerA <-- BrokerB <-- [publisher B1, subscriber B1, subscriber B2] IF a message-X is published to broker A and there no subscribers for it among the listeners on Broker-B (via criteria in Message Selectors or Broker routing rules), then that message-X will never be published to Broker-B. ELSE, broker A will publish the message to broker B, where one of the broker B listeners/subscribers/services is expecting that message based on the subscription criteria. Is Clustering the Correct Approach? At first, I concluded that the "Broker Clustering" concept is what I needed to support this. However, as I have come to understand it, the typical use of clustering entails either: message redundancy across all brokers ... or Competing Consumers pattern ... and neither of these satisfy the requirement in the EXAMPLE MODEL A. What is the Correct Approach? My question is, does anyone know of a JMS implementation that supports the model I described? I scanned through all the stackoverflow post titles for the search: JMS and Cluster. I found these two informative, but seemingly conflicting posts: Says the EXAMPLE MODEL A is/should-be implicitly supported: http://stackoverflow.com/questions/2255816/jms-consumer-with-activemq-network-of-brokers " this means you pick a broker, connect to it, and let the broker network sort it out amongst themselves. In theory." Says the EXAMPLE MODEL A IS NOT suported: http://stackoverflow.com/questions/2017520/how-does-a-jms-topic-subscriber-in-a-clustered-application-server-recieve-message "All the instances of PropertiesSubscriber running on different app servers WILL get that message." Any suggestions would be greatly appreciated. Thanks very much for reading my post, Gene

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  • PCA extended face recognition

    - by cMinor
    The state of the art says that we can use PCA to perform face recognition. like this, this or this I am working with a project that involves training a classifier to detect a person who is wearing glasess or hats or even a mustache. The purpose of doing this is to detect when a person that has robbed a bank, store, or have commeted some sort of crime(s) (we have their image in a database), enters a certain place ( historically we know these guys have robbed, so we should take care to avoid problems). We came first to have a distributed database with all images of criminals, then I thought to have a layer of them clasifying these criminals using accesories like hats, mustache or anything that hides their face etc... Then, to apply that knowledge to detect when a particular or a suspect person enters a comercial place. ( In practice when someone is going to rob not all the times they are using an accesorie...) What do you think about this idea of doing PCA to first detect principal components of the face and then the components of an accesory. I was thinking that maybe a probabilistic approach is better so we can compute the probability the criminal is the person that entered a place and call the respective authorities.

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  • Make WebStart Java desktop application to start on system startup on Windows and Mac

    - by parxier
    I developed small cross-platform (Windows and Mac) SWT desktop application. It is distributed with WebStart. So far so good, everything works. I've got a new requirement to make my app start on system startup (with no user interaction). What is the best way to accomplish that? In JNLP file I've got this: <shortcut online="false"> <desktop/> <menu submenu="CompanyName"/> </shortcut> On Windows WebStart creates a desktop link [app_name].lnk and it points to javaws.exe and then some Java cache file as a parameter with funny name like ..\Sun\Java\Deployment\cache\6.0\4\2c0a6a781-213476. I can possibly programmatically find that link on user's machine by name... erm... and then copy it into user's Startup folder. I can see a problem here though as user can disable WebStart desktop shortcut creation option all together. On Mac WebStart pops up a dialog to prompt user for the location where to create an [app_name].app (user is allowed to change link name there!) file that launches an application. On Mac I don't event know where the Startup folder is located (and it seems to be much more complex there). Is there Java library out there that abstracts start app on system startup concept on different platforms as SWT does for GUI abstraction?

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  • Linux 2.6.31 Scheduler and Multithreaded Jobs

    - by dsimcha
    I run massively parallel scientific computing jobs on a shared Linux computer with 24 cores. Most of the time my jobs are capable of scaling to 24 cores when nothing else is running on this computer. However, it seems like when even one single-threaded job that isn't mine is running, my 24-thread jobs (which I set for high nice values) only manage to get ~1800% CPU (using Linux notation). Meanwhile, about 500% of the CPU cycles (again, using Linux notation) are idle. Can anyone explain this behavior and what I can do about it to get all of the 23 cores that aren't being used by someone else? Notes: In case it's relevant, I have observed this on slightly different kernel versions, though I can't remember which off the top of my head. The CPU architecture is x64. Is it at all possible that the fact that my 24-core jobs are 32-bit and the other jobs I'm competing w/ are 64-bit is relevant? Edit: One thing I just noticed is that going up to 30 threads seems to alleviate the problem to some degree. It gets me up to ~2100% CPU.

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  • How can one setup a version control system on a local network, without a server?

    - by Andrew
    Edit: Ok so I learned that I guess I need an distributed source control, however are there any UI based ones, and do they allow you to merge with other users on the network? This is kind of a two part question, so here it goes. I want to start developing a web application at home (with multiple developers). However, I don't have a dedicated server nor want to pay for on. So first, I don't know which version control system to use for this case, as at work we mostly have TFS setup, so I am not to familiar with whats out there. What are the best free CVS/SVN tools out there? Second, is it possible to somehow setup the CVS/SVN where there is no dedicated server and both clients store up to one week of the source code from the last check-in? Also, it would be helpful if it could integrate with visual studio, again this isn't that important at all. Problem: There are Five users, one is a Server. Server Connected: All Ok Server Disconnected: No one can share. What I am looking for: No Server: Users still have versioning based on version id of last check-in. Users must check all version on network to make sure they aren't outdated based on their last version id. If not check-in, otherwise merge/get latest. If they are update checkin, and set current version id +1.

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  • What encoding does InstallShield expect non-latin-alphabet string table entries to use?

    - by DNS
    I work on an app that gets distributed via a single installer containing multiple localizations. The build process includes a script that updates the .ism string table with translations for each supported language. This works fine for languages like French and German. But when testing the installer in, i.e. Japanese, the text shows up as a series of squares. It's unlikely to be a font problem, since the InstallShield-supplied strings show up fine; only the string table entries are mangled. So the problem seems to be that the strings are in the wrong encoding. The .ism is in XML format, with UTF-8 declared as its encoding, so I assumed the strings needed to be UTF-8 encoded as well. Do they actually need to use the encoding of the target platform? Is there any concern, then, about targets having different encodings, i.e. Chinese systems using one GB-encoding versus another? What is the right thing to do here?

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  • Version control for PHP Developement

    - by Vinod Mohan
    Hello, I have been hearing a lot about the advantages of using a version control system and would like to try one. I was doing freelance web development in PHP for the past 2 years, two months back I hired two more programmer to help me. I will be hiring one more person soon. We maintain 4 websites, all of which are my own, which are continuously being edited by one of us. I learned PHP by myself and have never worked in any other firms. Hence I am new to version control, unit testing and all. Currently, we have development servers on our workstations. When we edit a particular section of a site, we download the code for that particular section (say /news/ or /movies/ or /wallpapers/ ) from the production server to the dev server, makes the changes locally and uploads to the production server (no code review / testing). Because of this, our dev server is always out of date from our prod server. Occasionally, this also create problem when one of us forgets to download the latest copy from prod and overwrites the last change. I know this is very very foolish, but currently our prod server is the only copy that has all the updates and latest changes. Can anyone please suggest which is the best version control system for me? I am more interested in distributed version control, since we don't have a central backup for all our code. I read about Mercurial and Git and found that Mercurial is used in several large open source projects by Mozilla, Sun, Symbian etc. So which one do you think is better for me? Not only version control, if there are any other package that I can use to make my current setup better, please mention that too :) Thanks and Regards, Vinod Mohan

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  • Bundle a Python app as a single file to support add-ons or extensions?

    - by Brandon Craig Rhodes
    There are several utilities — all with different procedures, limitations, and target operating systems — for getting a Python package and all of its dependencies and turning them into a single binary program that is easy to ship to customers: http://wiki.python.org/moin/Freeze http://www.pyinstaller.org/ http://www.py2exe.org/ http://svn.pythonmac.org/py2app/py2app/trunk/doc/index.html My situation goes one step further: third-party developers will be wanting to write plug-ins, extensions, or add-ons for my application. It is, of course, a daunting question how users on platforms like Windows would most easily install plugins or addons in such a way that my app can easily discover that they have been installed. But beyond that basic question is another: how can a third-party developer bundle their extension with whatever libraries the extension itself needs (which might be binary modules, like lxml) in such a way that the plugin's dependencies become available for import at the same time that the plugin becomes available. How can this be approached? Will my application need its own plug-in area on disk and its own plug-in registry to make this tractable? Or are there general mechanisms, that I could avoid writing myself, that would allow an app that is distributed as a single executable to look around and find plugins that are also installed as single files?

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  • Where to find algorithms for standard math functions?

    - by dsimcha
    I'm looking to submit a patch to the D programming language standard library that will allow much of std.math to be evaluated at compile time using the compile-time function evaluation facilities of the language. Compile-time function evaluation has several limitations, the most important ones being: You can't use assembly language. You can't call C code or code for which the source is otherwise unavailable. Several std.math functions violate these and compile-time versions need to be written. Where can I get information on good algorithms for computing things such as logarithms, exponents, powers, and trig functions? I prefer just high level descriptions of algorithms to actual code, for two reasons: To avoid legal ambiguity and the need to make my code look "different enough" from the source to make sure I own the copyright. I want simple, portable algorithms. I don't care about micro-optimization as long as they're at least asymptotically efficient. Edit: D's compile time function evaluation model allows floating point results computed at compile time to differ from those computed at runtime anyhow, so I don't care if my compile-time algorithms don't give exactly the same result as the runtime version as long as they aren't less accurate to a practically significant extent.

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  • Detecting death of spawned process using Window CRT

    - by Michael Tiller
    Executive summary: I need a way to determine whether a Windows process I've spawned via _spawnl and am communicating with using FDs from _pipe has died. Details: I'm using the low-level CRT function in Windows (_eof, _read) to communicate with a process that was spawned via a call to _spawnl (with the P_NOWAIT) flag. I'm using _pipe to create file descriptors to communicate with this spawned process and passing those descriptors (the FD #) to it on the command line. It is worth mentioning that I don't control the spawned process. It's a black box to me. It turns out that the process we are spawning occasionally crashes. I'm trying to make my code robust to this by detecting the crash. Unfortunately, I can't see a way to do this. It seems reasonable to me to expect that a call to _eof or _read on one of those descriptors would return an error status (-1) if the process had died. Unfortunately, that isn't the case. It appears that the descriptors have a life of their own independent of the spawned process. So even though the process on the other end is dead, I get no error status on the file descriptor I'm using to communicate with it. I've got the PID for the nested process (returned from the _spanwnl call) but I don't see anything I can do with that. My code works really well except for one thing. I can't detect whether the spawned process is simply busy computing me an answer or has died. If I can use the information from _pipe and _spawnl to determine if the spawned process is dead, I'll be golden. Suggestions very welcome. Thanks in advance. UPDATE: I found a fairly simple solution and added it as the selected answer.

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  • Testing a wide variety of computers with a small company

    - by Tom the Junglist
    Hello everyone, I work for a small dotcom which will soon be launching a reasonably-complicated Windows program. We have uncovered a number of "WTF?" type scenarios that have turned up as the program has been passed around to the various not-technical-types that we've been unable to replicate. One of the biggest problems we're facing is that of testing: there are a total of three programmers -- only one working on this particular project, me -- no testers, and a handful of assorted other staff (sales, etc). We are also geographically isolated. The "testing lab" consists of a handful of VMWare and VPC images running sort-of fresh installs of Windows XP and Vista, which runs on my personal computer. The non-technical types try to be helpful when problems arise, we have trained them on how to most effectively report problems, and the software itself sports a wide array of diagnostic features, but since they aren't computer nerds like us their reporting is only so useful, and arranging remote control sessions to dig into the guts of their computers is time-consuming. I am looking for resources that allow us to amplify our testing abilities without having to put together an actual lab and hire beta testers. My boss mentioned rental VPS services and asked me to look in to them, however they are still largely very much self-service and I was wondering if there were any better ways. How have you, or any other companies in a similar situation handled this sort of thing? EDIT: According to the lingo, our goal here is to expand our systems testing capacity via an elastic computing platform such as Amazon EC2. At this point I am not sure suggestions of beefing up our unit/integration testing are going to help very much as we are consistently hitting walls at the systems testing phase. Has anyone attempted to do this kind of software testing on a cloud-type service like EC2? Tom

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  • Splitting MS Access Database - Front End Part Location

    - by kristof
    One of the best practices as specified by Microsoft for Access Development is splitting Access application into 2 parts; Front End that hold all the object except tables and the Back End that holds the tables. The msdn page links there to the article Splitting Microsoft Access Databases to Improve Performance and Simplify Maintainability that describes the process in details. It is recommended that in multi user environment the Back End is stored on the server/shared folder while the Front End is distributed to each user. That implies that each time there are any changes made to the front end they need to be deployed to every user machine. My question is: Assuming that the users themselves do not have rights to modify the Front End part of the application what would be the drawbacks/dangers of leaving this on the server as well next to the Back End copy? I can see the performance issues here, but are there any dangers here like possible corruptions etc? Thank you EDIT Just to clarify, the scenario specified in question assumes one Front End stored on the server and shared by users. I understand that the recommendation is to have FE deployed to each user machine, but my question is more about what are the dangers if that is not done. E.g. when you are given an existing solution that uses the approach of both FE and BE on the server. Assuming the the performance is acceptable and the customer is reluctant to change the approach would you still push the change? And why exactly? For example the danger of possible data corruption would definitely be the strong enough argument, but is that the case? It is a part of follow up of my previous question From SQL Server to MS Access 2007

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  • NonStop ODBC: how the connections (ODBC servers) are assigned to CPUs?

    - by Vladimir Dyuzhev
    We have an ODBC pool running on a NonStop server. The pool is connected to SQL/MX. This pool is used by a few external Java applications, each of which has an JDBC pool connected to ODBC pool (e.g. 14 connections per application). With time (after a few application recycles) we see an imbalance between CPUs -- some have 8 ODBC processes running, some only 5. That leads to CPU time imbalance too. Up to this point we assumed that a CPU is assigned to ODBC process in round-robin fashion. That would maintain the number of ODBC processes more or less equally distributed. It's not the case though. Is there any information on how ODBC pool decided which CPU to choose for every new allocated process? Does it look at CPU load? Available memory? Something else? Sadly, even HP's own people (available to us, that is) couldn't answer those questions with certainty. :-(

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  • Can per-user randomized salts be replaced with iterative hashing?

    - by Chas Emerick
    In the process of building what I'd like to hope is a properly-architected authentication mechanism, I've come across a lot of materials that specify that: user passwords must be salted the salt used should be sufficiently random and generated per-user ...therefore, the salt must be stored with the user record in order to support verification of the user password I wholeheartedly agree with the first and second points, but it seems like there's an easy workaround for the latter. Instead of doing the equivalent of (pseudocode here): salt = random(); hashedPassword = hash(salt . password); storeUserRecord(username, hashedPassword, salt); Why not use the hash of the username as the salt? This yields a domain of salts that is well-distributed, (roughly) random, and each individual salt is as complex as your salt function provides for. Even better, you don't have to store the salt in the database -- just regenerate it at authentication-time. More pseudocode: salt = hash(username); hashedPassword = hash(salt . password); storeUserRecord(username, hashedPassword); (Of course, hash in the examples above should be something reasonable, like SHA-512, or some other strong hash.) This seems reasonable to me given what (little) I know of crypto, but the fact that it's a simplification over widely-recommended practice makes me wonder whether there's some obvious reason I've gone astray that I'm not aware of.

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