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• How to manage multiple python versions ?

  - by Gyom

  short version: how can I get rid of the multiple-versions-of-python nightmare ? long version: over the years, I've used several versions of python, and what is worse, several extensions to python (e.g. pygame, pylab, wxPython...). Each time it was on a different setup, with different OSes, sometimes different architectures (like my old PowerPC mac). Nowadays I'm using a mac (OSX 10.6 on x86-64) and it's a dependency nightmare each time I want to revive script older than a few months. Python itself already comes in three different flavours in /usr/bin (2.5, 2.6, 3.1), but I had to install 2.4 from macports for pygame, something else (cannot remember what) forced me to install all three others from macports as well, so at the end of the day I'm the happy owner of seven (!) instances of python on my system. But that's not the problem, the problem is, none of them has the right (i.e. same set of) libraries installed, some of them are 32bits, some 64bits, and now I'm pretty much lost. For example right now I'm trying to run a three-year-old script (not written by me) which used to use matplotlib/numpy to draw a real-time plot within a rectangle of a wxwidgets window. But I'm failing miserably: py26-wxpython from macports won't install, stock python has wxwidgets included but also has some conflict between 32 bits and 64 bits, and it doesn't have numpy... what a mess ! Obviously, I'm doing things the wrong way. How do you usally cope with all that chaos ?e

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• Can I automatically throw descriptive exceptions with parameter values and class feild information?

  - by Robert H.

  I honestly don't throw exceptions often. I catch them even less, ironically. I currently work in shop where we let them bubble up to avicode. For whatever reason, however, avicode isn't configured to capture some of the critical bits I need when these exceptions come bouncing back to my attention. Specifically, I'd like to see the parameter values and the class’s field data at the time of the exception. I’d guess with the large suite of .Net services that I could create a static method to crawl up the stack, gather these bits and store them in a string that I could stick in my exception message. I really don't are how long such a method would take to execute as performance is no longer a concern when I hit one of these scenarios. If it's possible, I'm sure someone has done it. If that's the case, I'm having a hard time finding it. I think any search containing "exception" brings back too many resutls. Anyway, can this be done? If so, some examples or links would be great. Thanks in advance for your time, Robert

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• How to use MSBuild to target multiple versions of .NET Framework?

  - by McKAMEY

  I am improving the builds for an open source project which currently supports .NET Framework v2.0, v3.5, and now v4.0. Up until now, I've restricted myself to v2.0 to ensure compatibility, but with VS2010 I am interested in having real targeted builds. I'm looking for some guidance on how to edit the MSBuild csproj/soln to be able to cleanly produce builds for each target. I'm willing to have complexity in the csproj and in a batch file to control the build. My goal is to be able to have a command line script that could produce the builds without needing Visual Studio installed, but only the necessary .NET Framework(s). Ideally, I'd like to minimize dependencies on additional software (e.g. NAnt). I'm pretty sure this can be done but am having trouble finding a definitive guide on setting it up and best practices. Bonus: my next step after getting this set up will be to better support Mono Framework. Any help on doing this same thing for Mono would be much appreciated.

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• Hibernate database integrity with multiple java applications

  - by Austen

  We have 2 java web apps both are read/write and 3 standalone java read/write applications (one loads questions via email, one processes an xml feed, one sends email to subscribers) all use hibernate and share a common code base. The problem we have recently come across is that questions loaded via email sometimes overwrite questions created in one of the web apps. We originally thought this to be a caching issue. We've tried turning off the second level cache, but this doesn't make a difference. We are not explicitly opening and closing sessions, but rather let hibernate manage them via Util.getSessionFactory().getCurrentSession(), which thinking about it, may actually be the issue. We'd rather not setup a clustered 2nd level cache at this stage as this creates another layer of complexity and we're more than happy with the level of performance we get from the app as a whole. So does implementing a open-session-in-view pattern in the web apps and manually managing the sessions in the standalone apps sound like it would fix this? Or any other suggestions/ideas please? <property name="hibernate.transaction.factory_class">org.hibernate.transaction.JDBCTransactionFactory</property> <property name="hibernate.current_session_context_class">thread</property> <property name="hibernate.cache.use_second_level_cache">false</property>

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• Best ways to copyright protect your work for example Myows

  - by Saif Bechan

  Recently I have read about Myows, they say its: "The universal copyright management and protection app for smart creatives" It is used to protect your application from copyrights and more. Do you think this will be a good idea for large application, or are there better ways to achieve such a thing. url: Myows Update Referencing: http://stackoverflow.com/questions/2618015/has-anyone-tried-myows-to-copyright-protect-your-work/2618628#2618628 Wow there is no better person to have answered this question like the creator himself. Currently I am working on a large web application which is in late testing phase. Because of the complexity of the app there are not many versions of it online so copyright will be a huge issue for me as much of the code is in JavaScript and is easy copyable. I was glad to see that there is some company out there that provide such services, and naturally I wanted to know if there were people using it. I did not know that this type of concept was so 'new'. There were some nice points made in the answer, and I think it will be a good service for people like me. In the next couple of weeks I will be looking further into the subject and start uploading my code and see how it will works out. I will leave this question up because I do want some more suggestions on this topic.

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• How do I Data-Bind dual DateTimePicker to a single DateTime object

  - by S.C. Madsen

  Hi, I have a simple form, with two DateTimePicker-controls: One for date, and one for time. The thing is these two controls are supposed to represent a single point in time. Hence I would like to "Bind" them to a single DateTime property on my form (for simplicity). I did the following: // Start is a DateTime property on the form _StartDate.DataBindings.Add("Value", this, "Start"); _StartTime.DataBindings.Add("Value", this, "Start"); But hooking into "ValueChanged" event, yields mixed results... Sometimes I get exactly what I want, sometimes the updates of the property are "sluggish". I figured this way of splitting into two DateTimePicker's was fairly common. So how to do it? Update: There is possibly multiple questions in there: How do I bind a DateTimePicker (Format: Date) to a DateTime Property on a form? Then, how do I bind yet another DateTimePicker (Format: Time) to the same property? I'm using Visual Studio Express 2008 (.NET 3.5), and I seemingly get ValueChanged events from the DateTimePickers before the value is changed?

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• Dynamically created controls and the ASP.NET page lifecycle

  - by Dirk

  I'm working on an ASP.NET project in which the vast majority of the forms are generated dynamically at run time (form definitions are stored in a DB for customizability). Therefore, I have to dynamically create and add my controls to the Page every time OnLoad fires, regardless of IsPostBack. This has been working just fine and .NET takes care of managing ViewState for these controls. protected override void OnLoad(EventArgs e) { base.OnLoad(e); RenderDynamicControls() } private void RenderDynamicControls(){ //1. call service layer to retrieve form definition //2. create and add controls to page container } I have a new requirement in which if a user clicks on a given button (this button is created at design time) the page should be re-rendered in a slightly different way. So in addition to the code that executes in OnLoad (i.e. RenderDynamicControls()), I have this code: protected void MyButton_Click(object sender, EventArgs e) { RenderDynamicControlsALittleDifferently() } private void RenderDynamicControlsALittleDifferently() (){ //1. clear all controls from the page container added in RenderDynamicControls() //2. call service layer to retrieve form definition //3. create and add controls to page container } My question is, is this really the only way to accomplish what I'm after? It seems beyond hacky to effectively render the form twice simply to respond to a button click. I gather from my research that this is simply how the page-lifecycle works in ASP.NET: Namely, that OnLoad must fire on every Postback before child events are invoked. Still, it's worthwhile to check with the SO community before having to drink the kool-aid. On a related note, once I get this feature completed, I'm planning on throwing an UpdatePanel on the page to perform the page updates via Ajax. Any code/advice that make that transition easier would be much appreciated. Thanks

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• Speedup writing C programs using a subset of the Python syntax

  - by psihodelia

  I am constantly trying to optimize my time. Writing a C code takes a lot of time and requires much more keyboard touches than say writing a Python program. However, in order to speed up the time required to create a C program, one can automatize many things. I'd like to write my programs using smth. like Python but with C semantics. It means, all keywords are C keywords, but syntax is optimized. For example, this C code: #include "dsplib.h" #include "coeffs.h" #define MODULENAME "dsplib" #define NUM_SAMPLES 320 typedef float t_Vec; typedef struct s_Inter { char *pc_Name; struct s_Inter *px_Next; }t_Inter; typedef struct s_DspLibControl { t_Vec f_Y; }t_DspLibControl; void v_DspLibName(void) { printf("Module: %s", MODULENAME); printf("\n"); } int v_DspLibInitInterControl(t_DspLibControl *px_Con) { int y; px_Con->f_Y = 0.0; for(int i=0;i<10;i++) { y += i * i; } return y; } in optimized pythonized version can look like: include dsplib, coeffs define MODULENAME="dsplib", NUM_SAMPLES=320 typedef float t_Vec typedef struct s_Inter: char *pc_Name struct s_Inter *px_Next t_Inter typedef struct s_DspLibControl: t_Vec f_Y t_DspLibControl v_DspLibName(): printf("Module: %s", MODULENAME); printf("\n") int v_DspLibInitInterControl(t_DspLibControl *px_Con): int y px_Con->f_Y = 0.0 for int i=0;i<10;i++: y += i * i return y My question is: Do you know any VIM script, which allows to translate an original pythonized C code into a standard C code? For example, one is writing a C code but uses pythonized syntax, once she decides to translate pythonized blocks into standard C, she selects such blocks and press some key. And she doesn't save such pythonized code of course, VIM translates it into standard C.

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• QuadTrees - how to update when internal items are moving

  - by egarcia

  I've implemented a working QuadTree. It subdivides 2-d space in order to accomodate items, identified by their bounding box (x,y,width,height) on the smallest possible quad (up to a minimum area). My code is based on this implementation (mine is in Lua instead of C#) : http://www.codeproject.com/KB/recipes/QuadTree.aspx I've been able to successfully implement insertions and deletions successfully. I've turn now my attention to the update() function, since my items' position and dimensions change over time. My first implementation works, but it is quite naïve: function QuadTree:update(item) self:remove(item) return self.root:insert(item) end Yup, I basically remove and reinsert every item every time they move. This works, but I'd like to optimize it a bit more; after all, most of the time, moving items still remain on the same quadTree node most of the iterations. Is there any standard way to deal with this kind of update? In case it helps, my code is here: http://github.com/kikito/passion/blob/master/ai/QuadTree.lua I'm not looking for someone to implement it for me; pointers to an existing working implementation (even in other languages) would suffice.

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• How should I handle this Optimistic Concurrency error in this Entity Framework code, I have?

  - by Pure.Krome

  Hi folks, I have the following pseduo code in some Repository Pattern project that uses EF4. public void Delete(int someId) { // 1. Load the entity for that Id. If there is none, then null. // 2. If entity != null, then DeleteObject(..); } Pretty simple but I'm getting a run-time error:- ConcurrencyException: Store, Update, Insert or Delete statement affected an unexpected number of rows (0). Now, this is what is happening :- Two instances of EF4 are running inthe app at the same time. Instance A calls delete. Instance B calls delete a nano second later. Instance A loads the entity. Instance B also loads the entity. Instance A now deletes that entity - cool bananas. Instance B tries to delete the entity, but it's already gone. As such, the no-count or what not is 0, when it expected 1 .. or something like that. Basically, it figured out that the item it is suppose to delete, didn't delete (because it happened a split sec ago). I'm not sure if this is like a race-condition or something. Anyways, is there any tricks I can do here so the 2nd call doesn't crash? I could make it into a stored procedure.. but I'm hoping to avoid that right now. Any ideas? I'm wondering If it's possible to lock that row (and that row only) when the select is called ... forcing Instance B to wait until the row lock has been relased. By that time, the row is deleted, so when Instance B does it's select, the data is not there .. so it will never delete.

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• Prevent Rails link_to_remote multiple submits w Javascript

  - by Chris

  In a Rails project I need to keep a link_to_remote from getting double-clicked. It looks like :before and :after are my only choices - they get prepended/appended to the onclick Ajax call, respectively. But if I try something like: :before => "self.stopObserving()" t,he Ajax is never run. If I try it for :after the Ajax is run but the link never stops observing. The solutions I've seen rely on creating a variable and blocking the whole form, but there are multiple link_to_remote rows on this page and it is valid to click more than one of them at a time - just not the same one twice. One variable per row declared outside of link_to_remote seems very kludgey... Instead of using Prototype I originally tried plain Javascript first for this proof of concept - but it fails too: <a href="#" onclick="self.onclick = function(){alert('foo');};"click</a just puts up an alert when clicked - the lambda here does nothing? This next one is more like the desired goal and should only alert the first time. But instead it alerts every time: <a href="#" onclick="alert('bar'); self.onclick = function(){return false;};"click</a All ideas appreciated!

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• How to Avoid PHP Object Nesting/Creation Limit?

  - by Will Shaver

  I've got a handmade ORM in PHP that seems to be bumping up against an object limit and causing php to crash. Here's a simple script that will cause crashes: <? class Bob { protected $parent; public function Bob($parent) { $this->parent = $parent; } public function __toString() { if($this->parent) return (string) "x " . $this->parent; return "top"; } } $bobs = array(); for($i = 1; $i < 40000; $i++) { $bobs[] = new Bob($bobs[$1 -1]); } ?> Even running this from the command line will cause issues. Some boxes take more than 40,000 objects. I've tried it on Linux/Appache (fail) but my app runs on IIS/FastCGI. On FastCGI this causes the famous "The FastCGI process exited unexpectedly" error. Obviously 20k objects is a bit high, but it crashes with far fewer objects if they have data and nested complexity. Fast CGI isn't the issue - I've tried running it from the command line. I've tried setting the memory to something really high - 6,000MB and to something really low - 24MB. If I set it low enough I'll get the "allocated memory size xxx bytes exhausted" error. I'm thinking that it has to do with the number of functions that are called - some kind of nesting prevention. I didn't think that my ORM's nesting was that complicated but perhaps it is. I've got some pretty clear cases where if I load just ONE more object it dies, but loads in under 3 seconds if it works.

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• Should I expect Comet to be this slow?

  - by Chad Johnson

  I have the following in a Rails controller: def poll records = [] start_time = Time.now.to_i while records.length == 0 do records = Something.uncached{Something.find(:all, :conditions => { :some_condition => false})} if records.length > 0 break end sleep 1 if Time.now.to_i - start_time >= 20 break end end responseData = [] records.each do |record| responseData << { 'something' => record.some_value } # Flag message as received. record.some_condition = true record.save end render :text => responseData.to_json end and then I have Javascript performing an AJAX request. The request sits there for 20 seconds or until the controller method finds a record in the database, waiting. That works. function poll() { $.ajax({ url: '/my_controller/poll', type: 'GET', dataType: 'json', cache: false, data: 'time=' + new Date().getTime(), success: function(response) { // show response here }, complete: function() { poll(); }, error: function() { alert('error'); poll(); } }); } When I have 5 - 10 tabs open in my browser, my web application becomes super slow. Is this to be expected? Or is there some obvious improvement(s) I can make?

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• Does pressing Back always cause Activity to finish()?

  - by stormin986

  I've heard that pressing the back button will essentially cause the current Activity to finish(). Is this always the case? Seems like it would be with the way it pops the Activity off the stack. The one situation I'm not so sure about is when the root Activity in a Task has back pressed. I'm currently experiencing a very weird effect, described as follows: On loading my application, the first Activity is for initialization, and once it finishes, it calls my main Activity (a TabActivity). This first init activity has android:noHistory="true" set in the Manifest so pressing Back from my main Activity won't go back to that. It goes to the Launcher. When I click on my App in the Launcher a second time, the initialization activity loads again, and loads the main Activity when done. Almost immediately after, it loads a second instance of my main Activity. But ONLY after the Application has already been run once, and was exited by pressing BACK from the main Activity. It does it every subsequent time until I force quit the app or load a new version from the IDE. Based on this, I am suspecting some kind of Activity instance is lying around and being reused, since it only happens on the second+ time I run the application (and exit with BACK -- using HOME just returns to the last state of the app, no big deal). Anyone have any thoughts??

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• C# vs C - Big performance difference

  - by John

  I'm finding massive performance differences between similar code in C anc C#. The C code is: #include <stdio.h> #include <time.h> #include <math.h> main() { int i; double root; clock_t start = clock(); for (i = 0 ; i <= 100000000; i++){ root = sqrt(i); } printf("Time elapsed: %f\n", ((double)clock() - start) / CLOCKS_PER_SEC); } And the C# (console app) is: using System; using System.Collections.Generic; using System.Text; namespace ConsoleApplication2 { class Program { static void Main(string[] args) { DateTime startTime = DateTime.Now; double root; for (int i = 0; i <= 100000000; i++) { root = Math.Sqrt(i); } TimeSpan runTime = DateTime.Now - startTime; Console.WriteLine("Time elapsed: " + Convert.ToString(runTime.TotalMilliseconds/1000)); } } } With the above code, the C# completes in 0.328125 seconds (release version) and the C takes 11.14 seconds to run. The c is being compiled to a windows executable using mingw. I've always been under the assumption that C/C++ were faster or at least comparable to C#.net. What exactly is causing the C to run over 30 times slower? EDIT: It does appear that the C# optimizer was removing the root as it wasn't being used. I changed the root assignment to root += and printed out the total at the end. I've also compiled the C using cl.exe with the /O2 flag set for max speed. The results are now: 3.75 seconds for the C 2.61 seconds for the C# The C is still taking longer, but this is acceptable

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• Looking for Bugtracker with specific features

  - by Thorsten Dittmar

  Hi, we're looking into bugtracking systems at our firm. We're quite small (4 developers only). On the other hand we have quite a large number of customers we develop individual software for. Most software is built explicitly for one customer, apart from two or three standard tools we ship. To make support easier for us (and to avoid being interrupted by phone calls all the time) we're looking for a bugtracker that must support a specific set of features. We want the customers to report bugs/feature/change requests themselves and be notified about these reports by email. Then we'd like to track what we've done and how much time it took, notifying the customer about that per email (private notes for just us must be possible). At the end of the month we'd like to bill all closed reports according to the time it took to solve/implement them. The following must be possible: It must have a web based interface where the users must log in with credentials we provide. The users must not be able to create accounts themselves/we must be able to turn off such a feature. We must be able to configure projects and assign customer logins to these projects. The customers must only see projects they are assigned to, not any other projects. Also, customers must not "see" other customers. We would name the projects, so that standard tools are listed as separate projects for each customer. A monthly report must be available that we can use to get information about the requests we worked on per customer. I'd like to introduce some standard product like Mantis (I've played with that a little, but didn't quite figure out whether it provides all the features I listed above). The product should be Open Source and work on a XAMPP Windows Server 2003 environment. Does anybody have any good suggestions?

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• File Locked by Services (after service code reading the text file)

  - by rvpals

  I have a windows services written in C# .NET. The service is running on a internal timer, every time the interval hits, it will go and try to read this log file into a String. My issue is every time the log file is read, the service seem to lock the log file. The lock on that log file will continue until I stop the windows service. At the same time the service is checking the log file, the same log file needs to be continuously updated by another program. If the file lock is on, the other program could not update the log file. Here is the code I use to read the text log file. private string ReadtextFile(string filename) { string res = ""; try { System.IO.FileStream fs = new System.IO.FileStream(filename, System.IO.FileMode.Open, System.IO.FileAccess.Read); System.IO.StreamReader sr = new System.IO.StreamReader(fs); res = sr.ReadToEnd(); sr.Close(); fs.Close(); } catch (System.Exception ex) { HandleEx(ex); } return res; } Thank you.

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• Free Fall Question

  - by Makenshi

  ok im gonna try my best to explain my problem i have this program where u can select 5 balls when u select one you can take it with you while you have the mouse button pressed and its within the ball radius. The problem is that i need a way to make the ball go up when the user stop pressing the mouse button like he sent it to float in the air then make it fall down again i have one way to know the time,velocity and thus the acceleration but i dont know how to implement it... right now i have this void Circulo::caida(float velocidad,float tiempo) { if(this->posY >= 580) { this->posY = 580; this->vcaida = 0.0f; } else if(this->posY < 580) { //this->distancia=9.81f * 0.5f*tiempo*tiempo; this->vcaida += velocidad; this->posY += this->vcaida; } } with this like this it just falls and i cant make the effect i tried to explain... thank you i hope someone can help me .< oh yeah im calculating the time like this just in case it helps difX=(x> evento.motion.xrel)? x-evento.motion.xrel : evento.motion.xrel-x; difY=(y> evento.motion.yrel)? y-evento.motion.yrel : evento.motion.yrel-y; and im sending difY as the time variable

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• Do you like Twisted?

  - by Luca

  I use Python Twisted for web development, and I don't like it? I know async programming is a great idea, I know there are may async web servers now, I know it's the only way to solve some problems you'd have with threads but I don't like. The problem is that, you're forced to program in a twisted way. So, the architecture you have in mind, very often have to be modified to fit the way twisted works. The architecture have to follow the technology, I don't think this is good. When we use callback in javascript, we don't have too many difficulties: things are usually simpler, we use a callback in response to an Ajax call. But in a server web app things are, very often, a bit more complex. Writing chain of callbacks don't seem to me a wonderful way of programming. The code is not simple, and so it is difficult to understand and to maintain. Writing twisted code we very often lost the linear intuitive idea of the algorithm we wanted to implement, especially when things grow in complexity. What's your point of view?

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• onTouchListener togglebutton, ignores first press?

  - by Paul

  I have a togglebutton that should run code when I press it down and more code when I let go. However the first time I press and let go nothing happens. Every other time it is fine, why is this? I can see the method only runs the first time when I let go of the button (it does not trigger any onTouch part of the method though), how can I get around this, and have it work for the first press? public void pushtotalk3(final View view) { ((ToggleButton) view).setChecked(true); ((ToggleButton) view).setChecked(false); view.setOnTouchListener(new OnTouchListener() { @Override public boolean onTouch(View v, MotionEvent event) { //if more than one call, change this code int callId = 0; for (SipCallSession callInfo : callsInfo) { callId = callInfo.getCallId(); Log.e(TAG, "" + callInfo.getCallId()); } final int id = callId; switch (event.getAction()) { case MotionEvent.ACTION_DOWN: { //press ((ToggleButton) view).setBackgroundResource(R.drawable.btn_blue_glossy); ((ToggleButton) view).setChecked(true); OnDtmf(id, 17, 10); OnDtmf(id, 16, 9); return true; } case MotionEvent.ACTION_UP: { //release ((ToggleButton) view).setBackgroundResource(R.drawable.btn_lightblue_glossy); ((ToggleButton) view).setChecked(false); OnDtmf(id, 18, 11); OnDtmf(id, 18, 11); return true; } default: return false; } } }); } EDIT: the xml for the button: <ToggleButton android:id="@+id/PTT_button5" android:layout_width="0dp" android:layout_height="fill_parent" android:text="@string/ptt5" android:onClick="pushtotalk5" android:layout_weight="50" android:textOn="Push To Talk On" android:textOff="Push To Talk Off" android:background="@drawable/btn_lightblue_glossy" android:textColor="@android:color/white" android:textSize="15sp" /> EDIT: hardware problem, can't test solutions atm.

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• Is it normal for C++ static initialization to appear twice in the same backtrace?

  - by Joseph Garvin

  I'm trying to debug a C++ program compiled with GCC that freezes at startup. GCC mutex protects function's static local variables, and it appears that waiting to acquire such a lock is why it freezes. How this happens is rather confusing. First module A's static initialization occurs (there are __static_init functions GCC invokes that are visible in the backtrace), which calls a function Foo(), that has a static local variable. The static local variable is an object who's constructor calls through several layers of functions, then suddenly the backtrace has a few ??'s, and then it's is in the static initialization of a second module B (the __static functions occur all over again), which then calls Foo(), but since Foo() never returned the first time the mutex on the local static variable is still set, and it locks. How can one static init trigger another? My first theory was shared libraries -- that module A would be calling some function in module B that would cause module B to load, thus triggering B's static init, but that doesn't appear to be the case. Module A doesn't use module B at all. So I have a second (and horrifying) guess. Say that: Module A uses some templated function or a function in a templated class, e.g. foo<int>::bar() Module B also uses foo<int>::bar() Module A doesn't depend on module B at all At link time, the linker has two instances of foo<int>::bar(), but this is OK because template functions are marked as weak symbols... At runtime, module A calls foo<int>::bar, and the static init of module B is triggered, even though module B doesn't depend on module A! Why? Because the linker decided to go with module B's instance of foo::bar instead of module A's instance at link time. Is this particular scenario valid? Or should one module's static init never trigger static init in another module?

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• Demangling typeclass functions in GHC profiler output

  - by Paul Kuliniewicz

  When profiling a Haskell program written in GHC, the names of typeclass functions are mangled in the .prof file to distinguish one instance's implementations of them from another. How can I demangle these names to find out which type's instance it is? For example, suppose I have the following program, where types Fast and Slow both implement Show: import Data.List (foldl') sum' = foldl' (+) 0 data Fast = Fast instance Show Fast where show _ = show $ sum' [1 .. 10] data Slow = Slow instance Show Slow where show _ = show $ sum' [1 .. 100000000] main = putStrLn (show Fast ++ show Slow) I compile with -prof -auto-all -caf-all and run with +RTS -p. In the .prof file that gets generated, I see that the top cost centers are: COST CENTRE MODULE %time %alloc show_an9 Main 71.0 83.3 sum' Main 29.0 16.7 And in the tree, I likewise see (omitting irrelevant lines): individual inherited COST CENTRE MODULE no. entries %time %alloc %time %alloc main Main 232 1 0.0 0.0 100.0 100.0 show_an9 Main 235 1 71.0 83.3 100.0 100.0 sum' Main 236 0 29.0 16.7 29.0 16.7 show_anx Main 233 1 0.0 0.0 0.0 0.0 How do I figure out that show_an9 is Slow's implementation of show and not Fast's?

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• Detecting Connection Speed / Bandwidth in .net/WCF

  - by Mystagogue

  I'm writing both client and server code using WCF, where I need to know the "perceived" bandwidth of traffic between the client and server. I could use ping statistics to gather this information separately, but I wonder if there is a way to configure the channel stack in WCF so that the same statistics can be gathered simultaneously while performing my web service invocations. This would be particularly useful in cases where ICMP is disabled (e.g. ping won't work). In short, while making my regular business-related web service calls (REST calls to be precise), is there a way to collect connection speed data implicitly? Certainly I could time the web service round trip, compared to the size of data used in the round-trip, to give me an idea of throughput - but I won't know how much of that perceived bandwidth was network related, or simply due to server-processing latency. I could perhaps solve that by having the server send back a time delta, representing server latency, so that the client can compute the actual network traffic time. If a more sophisticated approach is not available, that might be my answer...

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• Best strategy for synching data in iPhone app

  - by iamj4de

  I am working on a regular iPhone app which pulls data from a server (XML, JSON, etc...), and I'm wondering what is the best way to implement synching data. Criteria are speed (less network data exchange), robustness (data recovery in case update fails), offline access and flexibility (adaptable when the structure of the database changes slightly, like a new column). I know it varies from app to app, but can you guys share some of your strategy/experience? For me, I'm thinking of something like this: 1) Store Last Modified Date in iPhone 2) Upon launching, send a message like getNewData.php?lastModifiedDate=... 3) Server will process and send back only modified data from last time. 4) This data is formatted as so: <+><data id="..."></data></+> // add this to SQLite/CoreData <-><data id="..."></data></-> // remove this <%><data id="..."><attribute>newValue</attribute></data></%> // new modified value I don't want to make <+, <-, <%... for each attribute as well, because it would be too complicated, so probably when receive a <% field, I would just remove the data with the specified id and then add it again (assuming id here is not some automatically auto-incremented field). 5) Once everything is downloaded and updated, I will update the Last Modified Date field. The main problem with this strategy is: If the network goes down when I am updating something = the Last Modified Date is not yet updated = next time I relaunch the app, I will have to go through the same thing again. Not to mention potential inconsistent data. If I use a temporary table for update and make the whole thing atomic, it would work, but then again, if the update is too long (lots of data change), the user has to wait a long time until new data is available. Should I use Last-Modified-Date for each of the data field and update data gradually?

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• Temporary storage for keeping data between program iterations?

  - by mr.b

  I am working on an application that works like this: It fetches data from many sources, resulting in pool of about 500,000-1,500,000 records (depends on time/day) Data is parsed Part of data is processed in a way to compare it to pre-existing data (read from database), calculations are made, and stored in database. Resulting dataset that has to be stored in database is, however, much smaller in size (compared to original data set), and ranges from 5,000-50,000 records. This process almost always updates existing data, perhaps adds few more records. Then, data from step 2 should be kept somehow, somewhere, so that next time data is fetched, there is a data set which can be used to perform calculations, without touching pre-existing data in database. I should point out that this data can be lost, it's not irreplaceable (key information can be read from database if needed), but it would speed up the process next time. Application components can (and will be) run off different computers (in the same network), so storage has to be reachable from multiple hosts. I have considered using memcached, but I'm not quite sure should I do so, because one record is usually no smaller than 200 bytes, and if I have 1,500,000 records, I guess that it would amount to over 300 MB of memcached cache... But that doesn't seem scalable to me - what if data was 5x that amount? If it were to consume 1-2 GB of cache only to keep data in between iterations (which could easily happen)? So, the question is: which temporary storage mechanism would be most suitable for this kind of processing? I haven't considered using mysql temporary tables, as I'm not sure if they can persist between sessions, and be used by other hosts in network... Any other suggestion? Something I should consider?

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