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Search found 2012 results on 81 pages for 'impossible'.

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• realtime diagnostics

  - by Ion Todirel

  I have an application which has a loop, part of a "Scheduler", which runs at all time and is the heart of the application. Pretty much like a game loop, just that my application is a WPF application and it's not a game. Naturally the application does logging at many points, but the Scheduler does some sensitive monitoring, and sometimes it's impossible just from the logs to tell what may have gotten wrong (and by wrong I don't mean exceptions) or the current status. Because Scheduler's inner loop runs at short intervals, you can't do file I/O-based logging (or using the Event Viewer) in there. First, you need to watch it in real-time, and secondly the log file would grow in size very fast. So I was thinking of ways to show this data to the user in the realtime, some things I considered: Display the data in realtime in the UI Use AllocConsole/WriteConsole to display this information in a console Use a different console application which would display this information, communicate between the Scheduler and the console app using pipes or other IPC techniques Use Windows' Performance Monitor and somehow feed it with this information ETW Displaying in the UI would have its issues. First it doesn't integrate with the UI I had in mind for my application, and I don't want to complicate the UI just for this. This diagnostics would only happen rarely. Secondly, there is going to be some non-trivial data protection, as the Scheduler has it's own thread. A separate console window would work probably, but I'm still worried if it's not too much threshold. Allocating my own console, as this is a windows app, would probably be better than a different console application (3), as I don't need to worry about IPC communication, and non-blocking communication. However a user could close the console I allocated, and it would be problematic in that case. With a separate process you don't have to worry about it. Assuming there is an API for Performance Monitor, it wouldn't be integrated too well with my app or apparent to the users. Using ETW also doesn't solve anything, just a random idea, I still need to display this information somehow. What others think, would there be other ways I missed?

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• how do i add images from drable folder instead of url in this code

  - by hayya anam

  i used the following URL https://github.com/jgilfelt/android-mapviewballoons source in my application is show image by using url how do i give images form my own drawable folder?? i found this mapview url which show images inbaloon but is show images by url i wanna show myown iamges how i do? howi give my own images from my folder public class CustomMap extends MapActivity { MapView mapView; List<Overlay> mapOverlays; Drawable drawable; Drawable drawable2; CustomItemizedOverlay<CustomOverlayItem> itemizedOverlay; CustomItemizedOverlay<CustomOverlayItem> itemizedOverlay2; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); mapView = (MapView) findViewById(R.id.mapview); mapView.setBuiltInZoomControls(true); mapOverlays = mapView.getOverlays(); // first overlay drawable = getResources().getDrawable(R.drawable.marker); itemizedOverlay = new CustomItemizedOverlay<CustomOverlayItem>(drawable, mapView); GeoPoint point = new GeoPoint((int)(51.5174723*1E6),(int)(-0.0899537*1E6)); CustomOverlayItem overlayItem = new CustomOverlayItem(point, "Tomorrow Never Dies (1997)", "(M gives Bond his mission in Daimler car)", "http://ia.media-imdb.com/images /M/MV5BMTM1MTk2ODQxNV5BMl5BanBnXkFtZTcwOTY5MDg0NA@@._V1._SX40_CR0,0,40,54_.jpg"); itemizedOverlay.addOverlay(overlayItem); GeoPoint point2 = new GeoPoint((int)(51.515259*1E6),(int)(-0.086623*1E6)); CustomOverlayItem overlayItem2 = new CustomOverlayItem(point2, "GoldenEye (1995)", "(Interiors Russian defence ministry council chambers in St Petersburg)", "http://ia.media-imdb.com/images M/MV5BMzk2OTg 4MTk1NF5BMl5BanBnXkFtZTcwNjExNTgzNA@@._V1._SX40_CR0,0,40,54_.jpg"); itemizedOverlay.addOverlay(overlayItem2); mapOverlays.add(itemizedOverlay); // second overlay drawable2 = getResources().getDrawable(R.drawable.marker2); itemizedOverlay2 = new CustomItemizedOverlay<CustomOverlayItem> (drawable2, mapView); GeoPoint point3 = new GeoPoint((int)(51.513329*1E6),(int)(-0.08896*1E6)); CustomOverlayItem overlayItem3 = new CustomOverlayItem(point3, "Sliding Doors (1998)", "(interiors)", null); itemizedOverlay2.addOverlay(overlayItem3); GeoPoint point4 = new GeoPoint((int)(51.51738*1E6),(int)(-0.08186*1E6)); CustomOverlayItem overlayItem4 = new CustomOverlayItem(point4, "Mission: Impossible (1996)", "(Ethan & Jim cafe meeting)", "http://ia.media-imdb.com/images /M/MV5BMjAyNjk5Njk0MV 5BMl5BanBnXkFtZTcwOTA4MjIyMQ@@._V1._SX40_CR0,0,40,54_.jpg"); itemizedOverlay2.addOverlay(overlayItem4); mapOverlays.add(itemizedOverlay2); final MapController mc = mapView.getController(); mc.animateTo(point2); mc.setZoom(16); } @Override protected boolean isRouteDisplayed() { return false; } }

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• I just can't kill Java thread.

  - by Adrian

  I have a thread that downloads some images from internet using different proxies. Sometimes it hangs, and can't be killed by any means. public HttpURLConnection uc; public InputStream in; Proxy proxy = new Proxy(Proxy.Type.HTTP, new InetSocketAddress("server", 8080)); URL url = new URL("http://images.com/image.jpg"); uc = (HttpURLConnection)url.openConnection(proxy); uc.setConnectTimeout(30000); uc.setAllowUserInteraction(false); uc.setDoOutput(true); uc.addRequestProperty("User-Agent","Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.0)"); uc.connect(); in = uc.getInputStream(); When it hangs, it freezes at the uc.getInputStream() method. I made a timer which tries to kill the thread if it's run time exceeds 3 minutes. I tried .terminate() the thread. No effect. I tried uc.disconnect() from the main thread. The method also hangs and with it, the main thread. I tried in.close(). No effect. I tried uc=null, in=null hoping for an exception that will end the thread. It keeps running. It never passes the uc.getInputStream() method. In my last test the thread lasted over 14 hours after receiving all above commands (or various combinations). I had to kill the Java process to stop the thread. If I just ignore the thread, and set it's instance to null, the thread doesn't die and is not cleaned by garbage collector. I know that because if I let the application running for several days, the Java process takes more and more system memory. In 3 days it took 10% of my 8Gb. RAM system. It is impossible to kill a thread whatever?

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• Data aggregation mongodb vs mysql

  - by Dimitris Stefanidis

  I am currently researching on a backend to use for a project with demanding data aggregation requirements. The main project requirements are the following. Store millions of records for each user. Users might have more than 1 million entries per year so even with 100 users we are talking about 100 million entries per year. Data aggregation on those entries must be performed on the fly. The users need to be able to filter on the entries by a ton of available filters and then present summaries (totals , averages e.t.c) and graphs on the results. Obviously I cannot precalculate any of the aggregation results because the filter combinations (and thus the result sets) are huge. Users are going to have access on their own data only but it would be nice if anonymous stats could be calculated for all the data. The data is going to be most of the time in batch. e.g the user will upload the data every day and it could like 3000 records. In some later version there could be automated programs that upload every few minutes in smaller batches of 100 items for example. I made a simple test of creating a table with 1 million rows and performing a simple sum of 1 column both in mongodb and in mysql and the performance difference was huge. I do not remember the exact numbers but it was something like mysql = 200ms , mongodb = 20 sec. I have also made the test with couchdb and had much worse results. What seems promising speed wise is cassandra which I was very enthusiastic about when I first discovered it. However the documentation is scarce and I haven't found any solid examples on how to perform sums and other aggregate functions on the data. Is that possible ? As it seems from my test (Maybe I have done something wrong) with the current performance its impossible to use mongodb for such a project although the automated sharding functionality seems like a perfect fit for it. Does anybody have experience with data aggregation in mongodb or have any insights that might be of help for the implementation of the project ? Thanks, Dimitris

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• Is my understanding of "select distinct" correct?

  - by paxdiablo

  We recently discovered a performance problem with one of our systems and I think I have the fix but I'm not certain my understanding is correct. In simplest form, we have a table blah into which we accumulate various values based on a key field. The basic form is: recdate date rectime time system varchar(20) count integer accum1 integer accum2 integer There are a lot more accumulators than that but they're all of the same form. The primary key is made up of recdate, rectime and system. As values are collected to the table, the count for a given recdate/rectime/system is incremented and the values for that key are added to the accumulators. That means the averages can be obtained by using accumN / count. Now we also have a view over that table specified as follows: create view blah_v ( recdate, rectime, system, count, accum1, accum2 ) as select distinct recdate, rectime, system, count, value (case when count > 0 then accum1 / count end, 0), value (case when count > 0 then accum2 / count end, 0) from blah; In other words, the view gives us the average value of the accumulators rather than the sums. It also makes sure we don't get a divide-by-zero in those cases where the count is zero (these records do exist and we are not allowed to remove them so don't bother telling me they're rubbish - you're preaching to the choir). We've noticed that the time difference between doing: select distinct recdate from XX varies greatly depending on whether we use the table or the view. I'm talking about the difference being 1 second for the table and 27 seconds for the view (with 100K rows). We actually tracked it back to the select distinct. What seems to be happening is that the DBMS is actually loading all the rows in and sorting them so as to remove duplicates. That's fair enough, it's what we stupidly told it to do. But I'm pretty sure the fact that the view includes every component of the primary key means that it's impossible to have duplicates anyway. We've validated the problem since, if we create another view without the distinct, it performs at the same speed as the underlying table. I just wanted to confirm my understanding that a select distinct can not have duplicates if it includes all the primary key components. If that's so, then we can simply change the view appropriately.

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• Spring AOP pointcut that matches annotation on interface

  - by seanizer

  Hello, this is my first post here, so I apologize in advance for any stupidity on my side. I have a service class implemented in Java 6 / Spring 3 that needs an annotation to restrict access by role. I have defined an annotation called RequiredPermission that has as its value attribute one or more values from an enum called OperationType: public @interface RequiredPermission { /** * One or more {@link OperationType}s that map to the permissions required * to execute this method. * * @return */ OperationType[] value();} public enum OperationType { TYPE1, TYPE2; } package com.mycompany.myservice; public interface MyService{ @RequiredPermission(OperationType.TYPE1) void myMethod( MyParameterObject obj ); } package com.mycompany.myserviceimpl; public class MyServiceImpl implements MyService{ public myMethod( MyParameterObject obj ){ // do stuff here } } I also have the following aspect definition: /** * Security advice around methods that are annotated with * {@link RequiredPermission}. * * @param pjp * @param param * @param requiredPermission * @return * @throws Throwable */ @Around(value = "execution(public *" + " com.mycompany.myserviceimpl.*(..))" + " && args(param)" + // parameter object " && @annotation( requiredPermission )" // permission annotation , argNames = "param,requiredPermission") public Object processRequest(final ProceedingJoinPoint pjp, final MyParameterObject param, final RequiredPermission requiredPermission) throws Throwable { if(userService.userHasRoles(param.getUsername(),requiredPermission.values()){ return pjp.proceed(); }else{ throw new SorryButYouAreNotAllowedToDoThatException( param.getUsername(),requiredPermission.value()); } } The parameter object contains a user name and I want to look up the required role for the user before allowing access to the method. When I put the annotation on the method in MyServiceImpl, everything works just fine, the pointcut is matched and the aspect kicks in. However, I believe the annotation is part of the service contract and should be published with the interface in a separate API package. And obviously, I would not like to put the annotation on both service definition and implementation (DRY). I know there are cases in Spring AOP where aspects are triggered by annotations one interface methods (e.g. Transactional). Is there a special syntax here or is it just plain impossible out of the box. PS: I have not posted my spring config, as it seems to be working just fine. And no, those are neither my original class nor method names. Thanks in advance, Sean PPS: Actually, here is the relevant part of my spring config: <aop:aspectj-autoproxy proxy-target-class="false" /> <bean class="com.mycompany.aspect.MyAspect"> <property name="userService" ref="userService" /> </bean>

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• Debugging site written mainly in JScript with AJAX code injection

  - by blumidoo

  Hello, I have a legacy code to maintain and while trying to understand the logic behind the code, I have run into lots of annoying issues. The application is written mainly in Java Script, with extensive usage of jQuery + different plugins, especially Accordion. It creates a wizard-like flow, where client code for the next step is downloaded in the background by injecting a result of a remote AJAX request. It also uses callbacks a lot and pretty complicated "by convention" programming style (lots of events handlers are created on the fly based on certain object names - e.g. current page name, current step name). Adding to that, the code is very messy and there is no obvious inner structure - the functions are scattered in the code, file names do not reflect the business role of the code, lots of functions and code snippets are most likely not used at all etc. PROBLEM: How to approach this code base, so that the inner flow of the code can be sort-of "reverse engineered" using a suite of smart debugging tools. Ideally, I would like to be able to attach to the running application and step through the code, breaking on each new function call. Also, it would be nice to be able to create a "diagram of calls" in the application (i.e. in order to run a particular page logic, this particular flow of function calls was executed in a particular order). Not to mention to be able to run a coverage analysis, identifying potentially orphaned code fragments. I would like to stress out once more, that it is impossible to understand the inner logic of the application just by looking at the code itself, unless you have LOTS of spare time and beer crates, which I unfortunately do not have :/ (shame...) An IDE of some sort that would aid in extending that code would be also great, but I am currently looking into possibility to use Visual Studio 2010 to do the job, as the site itself is a mix of Classic ASP and ASP.NET (I'd say - 70% Java Script with jQuery, 30% ASP). I have obviously tried FireBug, but I was unable to find a way to define a breakpoint or step into the code, which is "injected" into the client JS using AJAX calls (i.e. the application retrieves the code by invoking an URL and injects it to the client local code). Venkman debugger had similar issues. Any hints would be welcome. Feel free to ask additional questions.

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• Turn class "Interfaceable"

  - by scooterman

  Hi folks, On my company system, we use a class to represent beans. It is just a holder of information using boost::variant and some serialization/deserialization stuff. It works well, but we have a problem: it is not over an interface, and since we use modularization through dlls, building an interface for it is getting very complicated, since it is used in almost every part of our app, and sadly interfaces (abstract classes ) on c++ have to be accessed through pointers, witch makes almost impossible to refactor the entire system. Our structure is: dll A: interface definition through abstract class dll B: interface implementation there is a painless way to achieve that (maybe using templates, I don't know) or I should forget about making this work and simply link everything with dll B? thanks Edit: Here is my example. this is on dll A BeanProtocol is a holder of N dataprotocol itens, wich are acessed by a index. class DataProtocol; class UTILS_EXPORT BeanProtocol { public: virtual DataProtocol& get(const unsigned int ) const { throw std::runtime_error("Not implemented"); } virtual void getFields(std::list<unsigned int>&) const { throw std::runtime_error("Not implemented"); } virtual DataProtocol& operator[](const unsigned int ) { throw std::runtime_error("Not implemented"); } virtual DataProtocol& operator[](const unsigned int ) const { throw std::runtime_error("Not implemented"); } virtual void fromString(const std::string&) { throw std::runtime_error("Not implemented"); } virtual std::string toString() const { throw std::runtime_error("Not implemented"); } virtual void fromBinary(const std::string&) { throw std::runtime_error("Not implemented"); } virtual std::string toBinary() const { throw std::runtime_error("Not implemented"); } virtual BeanProtocol& operator=(const BeanProtocol&) { throw std::runtime_error("Not implemented"); } virtual bool operator==(const BeanProtocol&) const { throw std::runtime_error("Not implemented"); } virtual bool operator!=(const BeanProtocol&) const { throw std::runtime_error("Not implemented"); } virtual bool operator==(const char*) const { throw std::runtime_error("Not implemented"); } virtual bool hasKey(unsigned int field) const { throw std::runtime_error("Not implemented"); } }; the other class (named GenericBean) implements it. This is the only way I've found to make this work, but now I want to turn it in a truly interface and remove the UTILS_EXPORT (which is an _declspec macro), and finally remove the forced linkage of B with A.

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• Cocoa NSOutputStream send to a connection

  - by Chuck

  Hi, I am new to Cocoa, but managed to get a connection (to a FTP) up and running, and I've set up an eventhandler for the NSInputStream iStream to alert every response (which also works). What I manage to get is simply the hello message and a connection timeout 60 sec, closing control connection. After searching stackoverflow and finding a lot of NSOutputStream write problems (e.g. http://stackoverflow.com/questions/703729/how-to-use-nsoutputstreams-write-message) and a lot of confusion in my google hits, I figured I'd try to ask my own question: I've tried reading the developer.apple.com doc on OutputStream, but it seems almost impossible for me to send some data (in this case just a string) to the "connection" via the NSOutputStream oStream. - (IBAction) send_something: sender { const char *send_command_char = [@"USER foo" UTF8String]; send_command_buffer = [NSMutableData dataWithBytes:send_command_char length:strlen(send_command_char) + 1]; uint8_t *readBytes = (uint8_t *)[send_command_buffer mutableBytes]; NSInteger byteIndex = 0; readBytes += byteIndex; int data_len = [send_command_buffer length]; unsigned int len = ((data_len - byteIndex >= 1024) ? 1024 : (data_len-byteIndex)); uint8_t buf[len]; (void)memcpy(buf, readBytes, len); len = [oStream write:(const uint8_t *)buf maxLength:len]; byteIndex += len; } the above seems not to result in any useable events. typing it under NSStreamEventHasSpaceAvailable sometimes give a response if I spam the ftp by keep creating new connection instances and keep sending some command whenever oStream has free space. In other words, nothing "right" and so I'm still unclear how to properly send a command to the connection. Should I open - write - close every time i want to write to oStream (and thus to the ftp) and can I then expect a reply (hasBytesAvailable event on iStream)? For some reason I find it very difficult to find any clear tutorials on this matter. Seems like there are more than a few in the same position as me: unclear how to use oStream write? Any little bit that can help clear this up is greatly appreciated! If needed I can write the rest of the code. Chuck

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• Find location using only distance and range?

  - by pinnacler

  Triangulation works by checking your angle to three KNOWN targets. "I know the that's the Lighthouse of Alexandria, it's located here (X,Y) on a map, and it's to my right at 90 degrees." Repeat 2 more times for different targets and angles. Trilateration works by checking your distance from three KNOWN targets. "I know the that's the Lighthouse of Alexandria, it's located here (X,Y) on a map, and I'm 100 meters away from that." Repeat 2 more times for different targets and ranges. But both of those methods rely on knowing WHAT you're looking at. Say you're in a forest and you can't differentiate between trees, but you know where key trees are. These trees have been hand picked as "landmarks." You have a robot moving through that forest slowly. Do you know of any ways to determine location based solely off of angle and range, exploiting geometry between landmarks? Note, you will see other trees as well, so you won't know which trees are key trees. Ignore the fact that a target may be occluded. Our pre-algorithm takes care of that. 1) If this exists, what's it called? I can't find anything. 2) What do you think the odds are of having two identical location 'hits?' I imagine it's fairly rare. 3) If there are two identical location 'hits,' how can I determine my exact location after I move the robot next. (I assume the chances of having 2 occurrences of EXACT angles in a row, after I reposition the robot, would be statistically impossible, barring a forest growing in rows like corn). Would I just calculate the position again and hope for the best? Or would I somehow incorporate my previous position estimate into my next guess? If this exists, I'd like to read about it, and if not, develop it as a side project. I just don't have time to reinvent the wheel right now, nor have the time to implement this from scratch. So if it doesn't exist, I'll have to figure out another way to localize the robot since that's not the aim of this research, if it does, lets hope it's semi-easy.

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• Find location using only distance and bearing?

  - by pinnacler

  Triangulation works by checking your angle to three KNOWN targets. "I know the that's the Lighthouse of Alexandria, it's located here (X,Y) on a map, and it's to my right at 90 degrees." Repeat 2 more times for different targets and angles. Trilateration works by checking your distance from three KNOWN targets. "I know the that's the Lighthouse of Alexandria, it's located here (X,Y) on a map, and I'm 100 meters away from that." Repeat 2 more times for different targets and ranges. But both of those methods rely on knowing WHAT you're looking at. Say you're in a forest and you can't differentiate between trees, but you know where key trees are. These trees have been hand picked as "landmarks." You have a robot moving through that forest slowly. Do you know of any ways to determine location based solely off of angle and range, exploiting geometry between landmarks? Note, you will see other trees as well, so you won't know which trees are key trees. Ignore the fact that a target may be occluded. Our pre-algorithm takes care of that. 1) If this exists, what's it called? I can't find anything. 2) What do you think the odds are of having two identical location 'hits?' I imagine it's fairly rare. 3) If there are two identical location 'hits,' how can I determine my exact location after I move the robot next. (I assume the chances of having 2 occurrences of EXACT angles in a row, after I reposition the robot, would be statistically impossible, barring a forest growing in rows like corn). Would I just calculate the position again and hope for the best? Or would I somehow incorporate my previous position estimate into my next guess? If this exists, I'd like to read about it, and if not, develop it as a side project. I just don't have time to reinvent the wheel right now, nor have the time to implement this from scratch. So if it doesn't exist, I'll have to figure out another way to localize the robot since that's not the aim of this research, if it does, lets hope it's semi-easy.

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• Zaypay alternatives for payments using call or sms

  - by JohannesH

  We are currently trying to implement a payment provider in zaypay for paying for services using sms or by calling a number. We already have google checkout and paypal working for regular payments but zaypay is rather inflexible, poorly documented and a pain to setup when you have hundreds of products with varying prices. So my question is, do you know of any other european payment providers that take sms and call payments? As a response to Roberts answer/question Hi Robert, I must say that the Zaypay solution is the best and only I've seen thus far regarding phoned payments. However, since its now 2 months ago I finished the implementation of our custom Zaypay UI I can't remember much of the the details of the problems we were having. I'll try to give a brief of them anyways the best I can. First of all I would like to see a redirection type scenario for payalogues. From what I remember you guys are using the JS framework "Prototype" which doesn't play nice with jQuery which we are using so we weren't able to use the popup-type scenario supported by payalogues. Furthermore when implementing our custom interface I remember a lot of missing translations, like words that were codes instead of a word or a phrase. This meant we ended up writing/translating all the messages we needed ourselves. Also, another point of annoyance was the setup of prices and items. I wish we could just send in the order items/prices as a part of the interface like you can in Google Checkout or PayPal (not that they're flawless either), instead of having to define ALL the items you will ever sell through your admin interface beforehand. As far as I can remember it is virtually impossible to use Zaypay for a multi-item order in its current form. Finally there are, as far as I can tell, some security issues that you have to think about when you implement a custom solution... especially a ajax driven one. As I said in my original post you do mention this in the documentation but I believe the documentation wasn't that comprehensive regarding security issues. Again I wish I could give more details but the code & client is long since gone, so I can't look up the comments I wrote. Sorry! Oh yeah, the general API documentation weren't exactly comprehensive and 100% correct either. Again, I don't want to advice people against using Zaypay, I just want to advice that they should try it out first on a realistic prototype and think about their implementation before releasing to production. Maybe its just me who misunderstood a lot of things but I generally had a difficult time using your framework and I was left with a feeling that the API was very new and not thought through from the beginning.

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• How to combine designable components with dependency injection

  - by Wim Coenen

  When creating a designable .NET component, you are required to provide a default constructor. From the IComponent documentation: To be a component, a class must implement the IComponent interface and provide a basic constructor that requires no parameters or a single parameter of type IContainer. This makes it impossible to do dependency injection via constructor arguments. (Extra constructors could be provided, but the designer would ignore them.) Some alternatives we're considering: Service Locator Don't use dependency injection, instead use the service locator pattern to acquire dependencies. This seems to be what IComponent.Site.GetService is for. I guess we could create a reusable ISite implementation (ConfigurableServiceLocator?) which can be configured with the necessary dependencies. But how does this work in a designer context? Dependency Injection via properties Inject dependencies via properties. Provide default instances if they are necessary to show the component in a designer. Document which properties need to be injected. Inject dependencies with an Initialize method This is much like injection via properties but it keeps the list of dependencies that need to be injected in one place. This way the list of required dependencies is documented implicitly, and the compiler will assists you with errors when the list changes. Any idea what the best practice is here? How do you do it? edit: I have removed "(e.g. a WinForms UserControl)" since I intended the question to be about components in general. Components are all about inversion of control (see section 8.3.1 of the UMLv2 specification) so I don't think that "you shouldn't inject any services" is a good answer. edit 2: It took some playing with WPF and the MVVM pattern to finally "get" Mark's answer. I see now that visual controls are indeed a special case. As for using non-visual components on designer surfaces, I think the .NET component model is fundamentally incompatible with dependency injection. It appears to be designed around the service locator pattern instead. Maybe this will start to change with the infrastructure that was added in .NET 4.0 in the System.ComponentModel.Composition namespace.

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• Memory efficient int-int dict in Python

  - by Bolo

  Hi, I need a memory efficient int-int dict in Python that would support the following operations in O(log n) time: d[k] = v # replace if present v = d[k] # None or a negative number if not present I need to hold ~250M pairs, so it really has to be tight. Do you happen to know a suitable implementation (Python 2.7)? EDIT Removed impossible requirement and other nonsense. Thanks, Craig and Kylotan! To rephrase. Here's a trivial int-int dictionary with 1M pairs: >>> import random, sys >>> from guppy import hpy >>> h = hpy() >>> h.setrelheap() >>> d = {} >>> for _ in xrange(1000000): ... d[random.randint(0, sys.maxint)] = random.randint(0, sys.maxint) ... >>> h.heap() Partition of a set of 1999530 objects. Total size = 49161112 bytes. Index Count % Size % Cumulative % Kind (class / dict of class) 0 1 0 25165960 51 25165960 51 dict (no owner) 1 1999521 100 23994252 49 49160212 100 int On average, a pair of integers uses 49 bytes. Here's an array of 2M integers: >>> import array, random, sys >>> from guppy import hpy >>> h = hpy() >>> h.setrelheap() >>> a = array.array('i') >>> for _ in xrange(2000000): ... a.append(random.randint(0, sys.maxint)) ... >>> h.heap() Partition of a set of 14 objects. Total size = 8001108 bytes. Index Count % Size % Cumulative % Kind (class / dict of class) 0 1 7 8000028 100 8000028 100 array.array On average, a pair of integers uses 8 bytes. I accept that 8 bytes/pair in a dictionary is rather hard to achieve in general. Rephrased question: is there a memory-efficient implementation of int-int dictionary that uses considerably less than 49 bytes/pair?

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• Delphi getting property value of a member from ClassType

  - by Kayode Yusuf

  I am implementing a Boilerplate feature - allow users to Change descriptions of some components - like Tlabels - at run time. e.g. TFooClass = Class ( TBaseClass) Label : Tlabel; ... End; Var FooClass : TFooClass; ... At Design time, the value Label's caption property is say - 'First Name', when the application is run, there is a feature that allows the user to change the caption value to say 'Other Name'. Once this is changed, the caption for the label for the class instance of FooClass is updated immediately. The problem now is if the user for whatever reason wants to revert back to the design time value of say 'First Name' , it seems impossible. I can use the RTTIContext methods and all that but I at the end of the day, it seems to require the instance of the class for me to change the value and since this has already being changed - I seem to to have hit a brick wall getting around it. My question is this - is there a way using the old RTTI methods or the new RTTIContext stuff to the property of a class' member without instantiating the class - i.e. getting the property from the ClassType definition. This is code snippet of my attempt at doing that : c : TRttiContext; z : TRttiInstanceType; w : TRttiProperty; Aform : Tform; .... Begin ..... Aform := Tform(FooClass); for vCount := 0 to AForm.ComponentCount-1 do begin vDummyComponent := AForm.Components[vCount]; if IsPublishedProp(vDummyComponent,'Caption') then begin c := TRttiContext.Create; try z := (c.GetType(vDummyComponent.ClassInfo) as TRttiInstanceType); w := z.GetProperty('Caption'); if w <> nil then Values[vOffset, 1] := w.GetValue(vDummyComponent.ClassType).AsString ..... ..... .... .... I am getting all sorts of errors and any help will be greatly appreciated.

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• Runge-Kutta Method with adaptive step

  - by infoholic_anonymous

  I am implementing Runge-Kutta method with adaptive step in matlab. I get different results as compared to matlab's own ode45 and my own implementation of Runge-Kutta method with fixed step. What am I doing wrong in my code? Is it possible? function [ result ] = rk4_modh( f, int, init, h, h_min ) % % f - function handle % int - interval - pair (x_min, x_max) % init - initial conditions - pair (y1(0),y2(0)) % h_min - lower limit for h (step length) % h - initial step length % x - independent variable ( for example time ) % y - dependent variable - vertical vector - in our case ( y1, y2 ) function [ k1, k2, k3, k4, ka, y ] = iteration( f, h, x, y ) % core functionality performed within loop k1 = h * f(x,y); k2 = h * f(x+h/2, y+k1/2); k3 = h * f(x+h/2, y+k2/2); k4 = h * f(x+h, y+k3); ka = (k1 + 2*k2 + 2*k3 + k4)/6; y = y + ka; end % constants % relative error eW = 1e-10; % absolute error eB = 1e-10; s = 0.9; b = 5; % initialization i = 1; x = int(1); y = init; while true hy = y; hx = x; %algorithm [ k1, k2, k3, k4, ka, y ] = iteration( f, h, x, y ); % error estimation for j=1:2 [ hk1, hk2, hk3, hk4, hka, hy ] = iteration( f, h/2, hx, hy ); hx = hx + h/2; end err(:,i) = abs(hy - y); % step adjustment e = abs( hy ) * eW + eB; a = min( e ./ err(:,i) )^(0.2); mul = a * s; if mul >= 1 % step length admitted keepH(i) = h; k(:,:,i) = [ k1, k2, k3, k4, ka ]; previous(i,:) = [ x+h, y' ]; %' i = i + 1; if floor( x + h + eB ) == int(2) break; else h = min( [mul*h, b*h, int(2)-x] ); x = x + keepH(i-1); end else % step length requires further adjustments h = mul * h; if ( h < h_min ) error('Computation with given precision impossible'); end end end result = struct( 'val', previous, 'k', k, 'err', err, 'h', keepH ); end The function in question is: function [ res ] = fun( x, y ) % res(1) = y(2) + y(1) * ( 0.9 - y(1)^2 - y(2)^2 ); res(2) = -y(1) + y(2) * ( 0.9 - y(1)^2 - y(2)^2 ); res = res'; %' end The call is: res = rk4( @fun, [0,20], [0.001; 0.001], 0.008 ); The resulting plot for x1 : The result of ode45( @fun, [0, 20], [0.001, 0.001] ) is:

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• Make a compiled binary run at native speed flawlessly without recompiling from source on a another system?

  - by unknownthreat

  I know that many people, at a first glance of the question, may immediately yell out "Java", but no, I know Java's qualities. Allow me to elaborate my question first. Normally, when we want our program to run at a native speed on a system, whether it be Windows, Mac OS X, or Linux, we need to compile from source codes. If you want to run a program of another system in your system, you need to use a virtual machine or an emulator. While these tools allow you to use the program you need on the non-native OS, they sometimes have problems of performance and glitches. We also have a newer compiler called "JIT Compiler", where the compiler will parse the bytecode program to native machine language before execution. The performance may increase to a very good extent with JIT Compiler, but the performance is still not the same as running it on a native system. Another program on Linux, WINE, is also a good tool for running Windows program on Linux system. I have tried running Team Fortress 2 on it, and tried experiment with some settings. I got ~40 fps on Windows at its mid-high setting on 1280 x 1024. On Linux, I need to turn everything low at 1280 x 1024 to get ~40 fps. There are 2 notable things though: Polygon model settings do not seem to affect framerate whether I set it low or high. When there are post-processing effects or some special effects that require manipulation of drawn pixels of the current frame, the framerate will drop to 10-20 fps. From this point, I can see that normal polygon rendering is just fine, but when it comes to newer rendering methods that requires graphic card to the job, it slows down to a crawl. Anyway, this question is rather theoretical. Is there anything we can do at all? I see that WINE can run STEAM and Team Fortress 2. Although there are flaws, they can run at lower setting. Or perhaps, I should also ask, "is it possible to translate one whole program on a system to another system without recompiling from source and get native speed?" I see that we also have AOT Compiler, is it possible to use it for something like this? Or there are so many constraints (such as DirectX call or differences in software architecture) that make it impossible to have a flawless and not native to the system program that runs at native speed?

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• Sorting a list of colors in one dimension?

  - by Ptah- Opener of the Mouth

  I would like to sort a one-dimensional list of colors so that colors that a typical human would perceive as "like" each other are near each other. Obviously this is a difficult or perhaps impossible problem to get "perfectly", since colors are typically described with three dimensions, but that doesn't mean that there aren't some sorting methods that look obviously more natural than others. For example, sorting by RGB doesn't work very well, as it will sort in the following order, for example: (1) R=254 G=0 B=0 (2) R=254 G=255 B=0 (3) R=255 G=0 B=0 (4) R=255 G=255 B=0 That is, it will alternate those colors red, yellow, red, yellow, with the two "reds" being essentially imperceivably different than each other, and the two yellows also being imperceivably different from each other. But sorting by HLS works much better, generally speaking, and I think HSL even better than that; with either, the reds will be next to each other, and the yellows will be next to each other. But HLS/HSL has some problems, too; things that people would perceive as "black" could be split far apart from each other, as could things that people would perceive as "white". Again, I understand that I pretty much have to accept that there will be some splits like this; I'm just wondering if anyone has found a better way than HLS/HSL. And I'm aware that "better" is somewhat arbitrary; I mean "more natural to a typical human". For example, a vague thought I've had, but have not yet tried, is perhaps "L is the most important thing if it is very high or very low", but otherwise it is the least important. Has anyone tried this? Has it worked well? What specifically did you decide "very low" and "very high" meant? And so on. Or has anyone found anything else that would improve upon HSL? I should also note that I am aware that I can define a space-filling curve through the cube of colors, and order them one-dimensionally as they would be encountered while travelling along that curve. That would eliminate perceived discontinuities. However, it's not really what I want; I want decent overall large-scale groupings more than I want perfect small-scale groupings. Thanks in advance for any help.

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• getline() sets failbit and skips last line

  - by Thanatos

  I'm using std::getline() to enumerate through the lines in a file, and it's mostly working. It's left me curious however - std::getline() is skipping the very last line in my file, but only if it's blank. Using this minimal example: #include <iostream> #include <string> int main() { std::string line; while(std::getline(std::cin, line)) std::cout << "Line: “" << line << "”\n"; return 0; } If I feed it this: Line A Line B Line C I get those lines back at me. But this: Line A Line B Line C [* line is present but blank, ie, the file end is: "...B\nLine C\n" *] (I unfortunately can't have a blank line in SO's little code box thing...) So, first file has three lines ( ["Line A", "Line B", "Line C"] ), second file has four ( ["Line A", "Line B", "Line C", ""] ) This to me seems wrong - I have a four line file, and enumerating it with getline() leaves me with 3. What's really got me scratching my head is that this is exactly what the standard says it should do. (21.3.7.9) Even Python has similar behaviour (but it gives me the newlines too - C++ chops them off.) Is this some weird thing where C++ is expected lines to be terminated, and not separated by '\n', and I'm feeding it differently? Edit Clearly, I need to expand a bit here. I've met up with two philosophies of determining what a "line" in a file is: Lines are terminated by newlines - Dominant in systems such as Linux, and editors like vim. Possible to have a slightly "odd" file by not having a final '\n' (a "noeol" in vim). Impossible to have a blank line at the end of a file. Lines are separated by newlines - Dominant in just about every Windows editor I've ever come across. Every file is valid, and it's possible to have the last line be blank. Of course, YMMV as to what a newline is. I've always treated these as two completely different schools of thought. One earlier point I tried to make was to ask if the C++ standard was explicitly or merely implicitly following the first. (Curiously, where is Mac? terminated or separated?)

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• using CSS to center FLOATED input elements wrapped in a DIV

  - by Tim

  There's no shortage of questions and answers about centering but I've not been able to get it to work given my specific circumstances, which involve floating. I want to center a container DIV that contains three floated input elements (split-button, text, checkbox), so that when my page is resized wider, they go from this: ||.....[ ][v] [ ] [ ] label .....|| to this ||......................[ ][v] [ ] [ ] label.......................|| They float fine, but when the page is made wider, they stay to the left: ||.....[ ][v] [ ] [ ] label .......................................|| If I remove the float so that the input elements are stacked rather than side-by-side: [ ][v] [ ] [ ] label then they DO center correctly when the page is resized. SO it is the float being applied to the elements of the DIV#hbox inside the container that is messing up the centering. Is what I want to do impossible because of the way float is designed to work? Here is my DOCTYPE, and the markup does validate at w3c: <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> Here is my markup: <div id="term1-container"> <div class="hbox"> <div> <button id="operator1" class="operator-split-button">equals</button> <button id="operator1drop">show all operators</button> </div> <div><input type="text" id="term1"></input></div> <div><input type="checkbox" id="meta2"></input><label for="meta2" class="tinylabel">meta</label></div> </div> </div> And here's the (not-working) CSS: #term1-container {text-align: center} .hbox {margin: 0 auto;} .hbox div {float:left; } I have also tried applying display: inline-block to the floated button, text-input, and checkbox; and even though I think it applies only to text, I've also tried applying white-space: nowrap to the #term1-container DIV, based on posts I've seen here on SO. And just to be a little more complete, here's the jQuery that creates the split-button: $(".operator-split-button").button().click( function() { alert( "foo" ); }).next().button( { text: false, icons: { primary: "ui-icon-triangle-1-s" } }).click( function(){positionOperatorsMenu();} ) })

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• Need a fast programming language that can drive two printers

  - by Pete

  I have a rather unusual application that isn't working the way I need, and I hope someone here will have some suggestions or at least a direction to investigate. We have a museum exhibit that has a computer at the entrance driving two small receipt printers. There are two buttons on a console, wired to the left and right buttons of a disemboweled mouse. The two printers and associated buttons are for girls and boys, each button does a random selection from a database of names and prints a small ticket on the appropriate printer with a graphic image, a few words about the exhibit and the randomly chosen name. Conceptually all is well, but it hangs quite often. I got the project at the last minute, because the original designer got bogged down and couldn't deliver, so the exhibit's author asked me the day before opening, whether I could write something that would work. I did it in Word, since I am an experienced VBA programmer. Several other avenues I attempted first all lead to dead ends - one couldn't do graphics, another couldn't handle two printers, yet another couldn't change fonts and so on. The problem is that it simply isn't fast enough - Word can only drive one printer at a time and changing the active printer takes a long time. Not by office standards, where a second or two of delay before a printer starts working on your document is not an issue, but here I need more or less instant response. If kids press a button and nothing happens, they press it over and over until something does happen, resulting in maybe half a dozen commands being sent before the printer starts reacting. Sometimes it jams the program completely, since boys and girls will be pressing the two buttons simultaneously and Word locks up, and even when it doesn't jam, the printers then spit out a stream of tickets, making a mess. The kids start squabbling over which ticket is whose, pulling them out of the printers, snarling the paper tape, jamming the printer and generally making a mess of the whole affair, often necessitating the exhibit caretakers having to restart the computer and clear torn bits of paper out the printers. What I need is some sort of fast programming language that can drive two printers *-simultaneously-*, not the MSOffice claptrap of having to switch the active printer, that can react to both left and right mouse button click events, can print a small graphic image and can print in different font sizes and styles and. I don't need many, but it's not all in one typeface. Can anyone suggest what I might use for this? I don't even know if it's possible at all under Windows, whether the "single active printer" garbage is an Office artifact, or a Windows restriction. My little Commodore-64 twenty-five years ago had two printers attached to it and drove both simultaneously with no difficulties - it doesn't seem to me it should be such an impossible requirement today.

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• centering a div without setting width

  - by Daniel

  Is there a way to do this? When using navigation that can change the number of items often, it would be nice not having to calculate the with and updating the css, but just having a solution that works. if that's impossible (I'm assuming it is) can anyone point me to a javascript that can do this? edit re: provide code some code basically I'm working with, what I think is, the most typical setup <div class="main"> <div class="nav"> <ul> <li>short title</li> <li>Item 3 Long title</li> <li>Item 4 Long title</li> <li>Item 5 Long title</li> <li>Item 6 Extra Long title</li> </ul> </div> </div> edit .main { width:100%; text-align:center; } .nav { margin:0 auto; } .nav ul li { display:inline; text-align:left; } the issue I've found with this/these solutions is that the content is nudged to the right adding some right padding (of 40px) seems to fix this across the browsers I'm checking on (O FF IE). .nav { margin:0 auto; padding-right:40px; } I don't know where this value is coming from though and why 40px fixes this. Does anyone know where this is coming from? it's not a margin or padding but no matter what I do the first about 40px can not be used for placement. Maybe it's the ul or li that's adding this. I've had a look at the display:table-cell way of doing this, but there's that complication with IE and it still has the same issue as the other solution edit (final) okay I've tried some things in regard to the indent. I've reset all padding to 0 *{padding:0;} that fixed it, and I don't need to offset the padding (I think I'll leave my whole process up so if anyone comes across this, it'll save them some time) thanks for the comments and replies

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• Custom onsynctopreference for XUL textbox

  - by Alexey Romanov

  I wanted to enable custom shortcuts in my Firefox extension. The idea is that the user just focuses on a textbox, presses key combination, and it's shown in the textbox and saved to a preference. However, I couldn't get it to work. With this XUL <?xml version="1.0"?> <?xml-stylesheet href="chrome://global/skin/" type="text/css"?> <?xml-stylesheet href="chrome://mozapps/skin/pref/pref.css" type="text/css"?> <!DOCTYPE window SYSTEM "chrome://nextplease/locale/nextplease.dtd"> <prefwindow id="nextpleaseprefs" title="&options.title;" buttons="accept, cancel" xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"> <prefpane id="nextplease.general" label="&options.general.title;" image="chrome://nextplease/skin/Sound Mixer.png"> <preferences> <preference id="nextkey" name="nextplease.nextkey" type="int"/> </preferences> <vbox flex="1"> <hbox align="center"> <label value="&options.general.nextKey;" /> <textbox id="nextkey" flex="1" editable="false" onkeyup="return nextplease.handleKeySelection(this, event);" preference-editable="true" preference="nextkey" onsynctopreference="alert('syncing'); return nextplease.syncKeySelector(this);"/> </hbox> </vbox> </prefpane> <script type="application/x-javascript" src="chrome://nextplease/content/nextpleaseCommon.js" /> <script type="application/x-javascript" src="chrome://nextplease/content/nextpleaseOptions.js" /> </prefwindow> the event in onkeyup works. But when I click the OK button, I don't see a "syncing" alert. Why isn't onsynctopreference working? Is it impossible to have custom onsynctopreference attribute for a textbox?

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• Precise explanation of JavaScript <-> DOM circular reference issue

  - by Joey Adams

  One of the touted advantages of jQuery.data versus raw expando properties (arbitrary attributes you can assign to DOM nodes) is that jQuery.data is "safe from circular references and therefore free from memory leaks". An article from Google titled "Optimizing JavaScript code" goes into more detail: The most common memory leaks for web applications involve circular references between the JavaScript script engine and the browsers' C++ objects' implementing the DOM (e.g. between the JavaScript script engine and Internet Explorer's COM infrastructure, or between the JavaScript engine and Firefox XPCOM infrastructure). It lists two examples of circular reference patterns: DOM element → event handler → closure scope → DOM DOM element → via expando → intermediary object → DOM element However, if a reference cycle between a DOM node and a JavaScript object produces a memory leak, doesn't this mean that any non-trivial event handler (e.g. onclick) will produce such a leak? I don't see how it's even possible for an event handler to avoid a reference cycle, because the way I see it: The DOM element references the event handler. The event handler references the DOM (either directly or indirectly). In any case, it's almost impossible to avoid referencing window in any interesting event handler, short of writing a setInterval loop that reads actions from a global queue. Can someone provide a precise explanation of the JavaScript ↔ DOM circular reference problem? Things I'd like clarified: What browsers are effected? A comment in the jQuery source specifically mentions IE6-7, but the Google article suggests Firefox is also affected. Are expando properties and event handlers somehow different concerning memory leaks? Or are both of these code snippets susceptible to the same kind of memory leak? // Create an expando that references to its own element. var elem = document.getElementById('foo'); elem.myself = elem; // Create an event handler that references its own element. var elem = document.getElementById('foo'); elem.onclick = function() { elem.style.display = 'none'; }; If a page leaks memory due to a circular reference, does the leak persist until the entire browser application is closed, or is the memory freed when the window/tab is closed?

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• Efficient algorithm to distribute work?

  - by Zwei Steinen

  It's a bit complicated to explain but here we go. We have problems like this (code is pseudo-code, and is only for illustrating the problem. Sorry it's in java. If you don't understand, I'd be glad to explain.). class Problem { final Set<Integer> allSectionIds = { 1,2,4,6,7,8,10 }; final Data data = //Some data } And a subproblem is: class SubProblem { final Set<Integer> targetedSectionIds; final Data data; SubProblem(Set<Integer> targetedSectionsIds, Data data){ this.targetedSectionIds = targetedSectionIds; this.data = data; } } Work will look like this, then. class Work implements Runnable { final Set<Section> subSections; final Data data; final Result result; Work(Set<Section> subSections, Data data) { this.sections = SubSections; this.data = data; } @Override public void run(){ for(Section section : subSections){ result.addUp(compute(data, section)); } } } Now we have instances of 'Worker', that have their own state sections I have. class Worker implements ExecutorService { final Map<Integer,Section> sectionsIHave; { sectionsIHave = {1:section1, 5:section5, 8:section8 }; } final ExecutorService executor = //some executor. @Override public void execute(SubProblem problem){ Set<Section> sectionsNeeded = fetchSections(problem.targetedSectionIds); super.execute(new Work(sectionsNeeded, problem.data); } } phew. So, we have a lot of Problems and Workers are constantly asking for more SubProblems. My task is to break up Problems into SubProblem and give it to them. The difficulty is however, that I have to later collect all the results for the SubProblems and merge (reduce) them into a Result for the whole Problem. This is however, costly, so I want to give the workers "chunks" that are as big as possible (has as many targetedSections as possible). It doesn't have to be perfect (mathematically as efficient as possible or something). I mean, I guess that it is impossible to have a perfect solution, because you can't predict how long each computation will take, etc.. But is there a good heuristic solution for this? Or maybe some resources I can read up before I go into designing? Any advice is highly appreciated!

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