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• LINQ to SQL - database relationships won't update after submit

  - by Quantic Programming

  I have a Database with the tables Users and Uploads. The important columns are: Users -> UserID Uploads -> UploadID, UserID The primary key in the relationship is Users -> UserID and the foreign key is Uploads -> UserID. In LINQ to SQL, I do the following operations: Retrieve files var upload = new Upload(); upload.UserID = user.UserID; upload.UploadID = XXX; db.Uploads.InsertOnSubmit(upload) db.SubmitChanges(); If I do that and rerun the application (and the db object is re-built, of course) - if do something like this: foreach(var upload in user.Uploads) I get all the uploads with that user's ID. (like added in the previous example) The problem is, that my application, after adding an upload an submitting changes, doesn't update the user.Uploads collection. i.e - I don't get the newly added uploads. The user object is stored in the Session object. At first, I though that the LINQ to SQL Framework doesn't update the reference of the object, therefore I should simply "reset" the user object from a new SQL request. I mean this: Session["user"] = db.Users.Where(u => u.UserID == user.UserID).SingleOrDefault(); (Where user is the previous user) But it didn't help. Please note: After rerunning the application, user.Uploads does have the new upload! Did anyone experience this type of problem, or is it normal behavior? I am a newbie to this framework. I would gladly take any advice. Thank you!

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• What is the correct way to implement GetProperty<T> on a MessageEncoder?

  - by Programming Hero

  The GetProperty<T> method is something of a mystery for me, especially when it comes to overriding the behaviour for MessageEncoder implementations. Are there any guidelines to the expected behaviour for this method?

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• GPGPU

  WhatGPU obviously stands for Graphics Processing Unit (the silicon powering the display you are using to read this blog post). The extra GP in front of that stands for General Purpose computing.So, altogether GPGPU refers to computing we can perform on GPU for purposes beyond just drawing on the screen. In effect, we can use a GPGPU a bit like we already use a CPU: to perform some calculation (that doesn’t have to have any visual element to it). The attraction is that a GPGPU can be orders of magnitude faster than a CPU.WhyWhen I was at the SuperComputing conference in Portland last November, GPGPUs were all the rage. A quick online search reveals many articles introducing the GPGPU topic. I'll just share 3 here: pcper (ignoring all pages except the first, it is a good consumer perspective), gizmodo (nice take using mostly layman terms) and vizworld (answering the question on "what's the big deal").The GPGPU programming paradigm (from a high level) is simple: in your CPU program you define functions (aka kernels) that take some input, can perform the costly operation and return the output. The kernels are the things that execute on the GPGPU leveraging its power (and hence execute faster than what they could on the CPU) while the host CPU program waits for the results or asynchronously performs other tasks.However, GPGPUs have different characteristics to CPUs which means they are suitable only for certain classes of problem (i.e. data parallel algorithms) and not for others (e.g. algorithms with branching or recursion or other complex flow control). You also pay a high cost for transferring the input data from the CPU to the GPU (and vice versa the results back to the CPU), so the computation itself has to be long enough to justify the overhead transfer costs. If your problem space fits the criteria then you probably want to check out this technology.HowSo where can you get a graphics card to start playing with all this? At the time of writing, the two main vendors ATI (owned by AMD) and NVIDIA are the obvious players in this industry. You can read about GPGPU on this AMD page and also on this NVIDIA page. NVIDIA's website also has a free chapter on the topic from the "GPU Gems" book: A Toolkit for Computation on GPUs.If you followed the links above, then you've already come across some of the choices of programming models that are available today. Essentially, AMD is offering their ATI Stream technology accessible via a language they call Brook+; NVIDIA offers their CUDA platform which is accessible from CUDA C. Choosing either of those locks you into the GPU vendor and hence your code cannot run on systems with cards from the other vendor (e.g. imagine if your CPU code would run on Intel chips but not AMD chips). Having said that, both vendors plan to support a new emerging standard called OpenCL, which theoretically means your kernels can execute on any GPU that supports it. To learn more about all of these there is a website: gpgpu.org. The caveat about that site is that (currently) it completely ignores the Microsoft approach, which I touch on next.On Windows, there is already a cross-GPU-vendor way of programming GPUs and that is the DirectX API. Specifically, on Windows Vista and Windows 7, the DirectX 11 API offers a dedicated subset of the API for GPGPU programming: DirectCompute. You use this API on the CPU side, to set up and execute the kernels that run on the GPU. The kernels are written in a language called HLSL (High Level Shader Language). You can use DirectCompute with HLSL to write a "compute shader", which is the term DirectX uses for what I've been referring to in this post as a "kernel". For a comprehensive collection of links about this (including tutorials, videos and samples) please see my blog post: DirectCompute.Note that there are many efforts to build even higher level languages on top of DirectX that aim to expose GPGPU programming to a wider audience by making it as easy as today's mainstream programming models. I'll mention here just two of those efforts: Accelerator from MSR and Brahma by Ananth. Comments about this post welcome at the original blog.

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• The long road to bug-free software

  - by Tony Davis

  The past decade has seen a burgeoning interest in functional programming languages such as Haskell or, in the Microsoft world, F#. Though still on the periphery of mainstream programming, functional programming concepts are gradually seeping into the imperative C# language (for example, Lambda expressions have their root in functional programming). One of the more interesting concepts from functional programming languages is the use of formal methods, the lofty ideal behind which is bug-free software. The idea is that we write a specification that describes exactly how our function (say) should behave. We then prove that our function conforms to it, and in doing so have proved beyond any doubt that it is free from bugs. All programmers already use one form of specification, specifically their programming language's type system. If a value has a specific type then, in a type-safe language, the compiler guarantees that value cannot be an instance of a different type. Many extensions to existing type systems, such as generics in Java and .NET, extend the range of programs that can be type-checked. Unfortunately, type systems can only prevent some bugs. To take a classic problem of retrieving an index value from an array, since the type system doesn't specify the length of the array, the compiler has no way of knowing that a request for the "value of index 4" from an array of only two elements is "unsafe". We restore safety via exception handling, but the ideal type system will prevent us from doing anything that is unsafe in the first place and this is where we start to borrow ideas from a language such as Haskell, with its concept of "dependent types". If the type of an array includes its length, we can ensure that any index accesses into the array are valid. The problem is that we now need to carry around the length of arrays and the values of indices throughout our code so that it can be type-checked. In general, writing the specification to prove a positive property, even for a problem very amenable to specification, such as a simple sorting algorithm, turns out to be very hard and the specification will be different for every program. Extend this to writing a specification for, say, Microsoft Word and we can see that the specification would end up being no simpler, and therefore no less buggy, than the implementation. Fortunately, it is easier to write a specification that proves that a program doesn't have certain, specific and undesirable properties, such as infinite loops or accesses to the wrong bit of memory. If we can write the specifications to prove that a program is immune to such problems, we could reuse them in many places. The problem is the lack of specification "provers" that can do this without a lot of manual intervention (i.e. hints from the programmer). All this might feel a very long way off, but computing power and our understanding of the theory of "provers" advances quickly, and Microsoft is doing some of it already. Via their Terminator research project they have started to prove that their device drivers will always terminate, and in so doing have suddenly eliminated a vast range of possible bugs. This is a huge step forward from saying, "we've tested it lots and it seems fine". What do you think? What might be good targets for specification and verification? SQL could be one: the cost of a bug in SQL Server is quite high given how many important systems rely on it, so there's a good incentive to eliminate bugs, even at high initial cost. [Many thanks to Mike Williamson for guidance and useful conversations during the writing of this piece] Cheers, Tony.

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• The long road to bug-free software

  - by Tony Davis

  The past decade has seen a burgeoning interest in functional programming languages such as Haskell or, in the Microsoft world, F#. Though still on the periphery of mainstream programming, functional programming concepts are gradually seeping into the imperative C# language (for example, Lambda expressions have their root in functional programming). One of the more interesting concepts from functional programming languages is the use of formal methods, the lofty ideal behind which is bug-free software. The idea is that we write a specification that describes exactly how our function (say) should behave. We then prove that our function conforms to it, and in doing so have proved beyond any doubt that it is free from bugs. All programmers already use one form of specification, specifically their programming language's type system. If a value has a specific type then, in a type-safe language, the compiler guarantees that value cannot be an instance of a different type. Many extensions to existing type systems, such as generics in Java and .NET, extend the range of programs that can be type-checked. Unfortunately, type systems can only prevent some bugs. To take a classic problem of retrieving an index value from an array, since the type system doesn't specify the length of the array, the compiler has no way of knowing that a request for the "value of index 4" from an array of only two elements is "unsafe". We restore safety via exception handling, but the ideal type system will prevent us from doing anything that is unsafe in the first place and this is where we start to borrow ideas from a language such as Haskell, with its concept of "dependent types". If the type of an array includes its length, we can ensure that any index accesses into the array are valid. The problem is that we now need to carry around the length of arrays and the values of indices throughout our code so that it can be type-checked. In general, writing the specification to prove a positive property, even for a problem very amenable to specification, such as a simple sorting algorithm, turns out to be very hard and the specification will be different for every program. Extend this to writing a specification for, say, Microsoft Word and we can see that the specification would end up being no simpler, and therefore no less buggy, than the implementation. Fortunately, it is easier to write a specification that proves that a program doesn't have certain, specific and undesirable properties, such as infinite loops or accesses to the wrong bit of memory. If we can write the specifications to prove that a program is immune to such problems, we could reuse them in many places. The problem is the lack of specification "provers" that can do this without a lot of manual intervention (i.e. hints from the programmer). All this might feel a very long way off, but computing power and our understanding of the theory of "provers" advances quickly, and Microsoft is doing some of it already. Via their Terminator research project they have started to prove that their device drivers will always terminate, and in so doing have suddenly eliminated a vast range of possible bugs. This is a huge step forward from saying, "we've tested it lots and it seems fine". What do you think? What might be good targets for specification and verification? SQL could be one: the cost of a bug in SQL Server is quite high given how many important systems rely on it, so there's a good incentive to eliminate bugs, even at high initial cost. [Many thanks to Mike Williamson for guidance and useful conversations during the writing of this piece] Cheers, Tony.

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• Why do we get a sudden spike in response times?

  - by Christian Hagelid

  We have an API that is implemented using ServiceStack which is hosted in IIS. While performing load testing of the API we discovered that the response times are good but that they deteriorate rapidly as soon as we hit about 3,500 concurrent users per server. We have two servers and when hitting them with 7,000 users the average response times sit below 500ms for all endpoints. The boxes are behind a load balancer so we get 3,500 concurrents per server. However as soon as we increase the number of total concurrent users we see a significant increase in response times. Increasing the concurrent users to 5,000 per server gives us an average response time per endpoint of around 7 seconds. The memory and CPU on the servers are quite low, both while the response times are good and when after they deteriorate. At peak with 10,000 concurrent users the CPU averages just below 50% and the RAM sits around 3-4 GB out of 16. This leaves us thinking that we are hitting some kind of limit somewhere. The below screenshot shows some key counters in perfmon during a load test with a total of 10,000 concurrent users. The highlighted counter is requests/second. To the right of the screenshot you can see the requests per second graph becoming really erratic. This is the main indicator for slow response times. As soon as we see this pattern we notice slow response times in the load test. How do we go about troubleshooting this performance issue? We are trying to identify if this is a coding issue or a configuration issue. Are there any settings in web.config or IIS that could explain this behaviour? The application pool is running .NET v4.0 and the IIS version is 7.5. The only change we have made from the default settings is to update the application pool Queue Length value from 1,000 to 5,000. We have also added the following config settings to the Aspnet.config file: <system.web> <applicationPool maxConcurrentRequestsPerCPU="5000" maxConcurrentThreadsPerCPU="0" requestQueueLimit="5000" /> </system.web> More details: The purpose of the API is to combine data from various external sources and return as JSON. It is currently using an InMemory cache implementation to cache individual external calls at the data layer. The first request to a resource will fetch all data required and any subsequent requests for the same resource will get results from the cache. We have a 'cache runner' that is implemented as a background process that updates the information in the cache at certain set intervals. We have added locking around the code that fetches data from the external resources. We have also implemented the services to fetch the data from the external sources in an asynchronous fashion so that the endpoint should only be as slow as the slowest external call (unless we have data in the cache of course). This is done using the System.Threading.Tasks.Task class. Could we be hitting a limitation in terms of number of threads available to the process?

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• Android threading and database locking

  - by Sena Gbeckor-Kove

  Hi, We are using AsyncTasks to access database tables and cursors. Unfortunately we are seeing occasional exceptions regarding the database being locked. E/SQLiteOpenHelper(15963): Couldn't open iviewnews.db for writing (will try read-only): E/SQLiteOpenHelper(15963): android.database.sqlite.SQLiteException: database is locked E/SQLiteOpenHelper(15963): at android.database.sqlite.SQLiteDatabase.native_setLocale(Native Method) E/SQLiteOpenHelper(15963): at android.database.sqlite.SQLiteDatabase.setLocale(SQLiteDatabase.java:1637) E/SQLiteOpenHelper(15963): at android.database.sqlite.SQLiteDatabase.<init>(SQLiteDatabase.java:1587) E/SQLiteOpenHelper(15963): at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:638) E/SQLiteOpenHelper(15963): at android.database.sqlite.SQLiteDatabase.openOrCreateDatabase(SQLiteDatabase.java:659) E/SQLiteOpenHelper(15963): at android.database.sqlite.SQLiteDatabase.openOrCreateDatabase(SQLiteDatabase.java:652) E/SQLiteOpenHelper(15963): at android.app.ApplicationContext.openOrCreateDatabase(ApplicationContext.java:482) E/SQLiteOpenHelper(15963): at android.content.ContextWrapper.openOrCreateDatabase(ContextWrapper.java:193) E/SQLiteOpenHelper(15963): at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:98) E/SQLiteOpenHelper(15963): at android.database.sqlite.SQLiteOpenHelper.getReadableDatabase(SQLiteOpenHelper.java:158) E/SQLiteOpenHelper(15963): at com.iview.android.widget.IViewNewsTopStoryWidget.initData(IViewNewsTopStoryWidget.java:73) E/SQLiteOpenHelper(15963): at com.iview.android.widget.IViewNewsTopStoryWidget.updateNewsWidgets(IViewNewsTopStoryWidget.java:121) E/SQLiteOpenHelper(15963): at com.iview.android.async.GetNewsTask.doInBackground(GetNewsTask.java:338) E/SQLiteOpenHelper(15963): at com.iview.android.async.GetNewsTask.doInBackground(GetNewsTask.java:1) E/SQLiteOpenHelper(15963): at android.os.AsyncTask$2.call(AsyncTask.java:185) E/SQLiteOpenHelper(15963): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:256) E/SQLiteOpenHelper(15963): at java.util.concurrent.FutureTask.run(FutureTask.java:122) E/SQLiteOpenHelper(15963): at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:648) E/SQLiteOpenHelper(15963): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:673) E/SQLiteOpenHelper(15963): at java.lang.Thread.run(Thread.java:1060) Does anybody have a general example for code which writes to a database from a different thread than the one reading and how can we ensure thread safety. One suggestion I've had is to use a ContentProvider, as this would handle the access of the database from multiple threads. I am going to look at this, but is this the recommended method of handling such a problem? It seems rather heavyweight considering we're talking about in front or behind Thanks in advance.

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• infinite loop shutting down ensime

  - by Jeff Bowman

  When I run M-X ensime-disconnect I get the following forever: string matching regex `\"((?:[^\"\\]|\\.)*)\"' expected but `^@' found and I see this exception when I use C-c C-c Uncaught exception in com.ensime.server.SocketHandler@769aba32 java.net.SocketException: Broken pipe at java.net.SocketOutputStream.socketWrite0(Native Method) at java.net.SocketOutputStream.socketWrite(SocketOutputStream.java:109) at java.net.SocketOutputStream.write(SocketOutputStream.java:153) at sun.nio.cs.StreamEncoder.writeBytes(StreamEncoder.java:220) at sun.nio.cs.StreamEncoder.implFlushBuffer(StreamEncoder.java:290) at sun.nio.cs.StreamEncoder.implFlush(StreamEncoder.java:294) at sun.nio.cs.StreamEncoder.flush(StreamEncoder.java:140) at java.io.OutputStreamWriter.flush(OutputStreamWriter.java:229) at java.io.BufferedWriter.flush(BufferedWriter.java:253) at com.ensime.server.SocketHandler.write(server.scala:118) at com.ensime.server.SocketHandler$$anonfun$act$1$$anonfun$apply$mcV$sp$1.apply(server.scala:132) at com.ensime.server.SocketHandler$$anonfun$act$1$$anonfun$apply$mcV$sp$1.apply(server.scala:127) at scala.actors.Actor$class.receive(Actor.scala:456) at com.ensime.server.SocketHandler.receive(server.scala:67) at com.ensime.server.SocketHandler$$anonfun$act$1.apply$mcV$sp(server.scala:127) at com.ensime.server.SocketHandler$$anonfun$act$1.apply(server.scala:127) at com.ensime.server.SocketHandler$$anonfun$act$1.apply(server.scala:127) at scala.actors.Reactor$class.seq(Reactor.scala:262) at com.ensime.server.SocketHandler.seq(server.scala:67) at scala.actors.Reactor$$anon$3.andThen(Reactor.scala:240) at scala.actors.Combinators$class.loop(Combinators.scala:26) at com.ensime.server.SocketHandler.loop(server.scala:67) at scala.actors.Combinators$$anonfun$loop$1.apply(Combinators.scala:26) at scala.actors.Combinators$$anonfun$loop$1.apply(Combinators.scala:26) at scala.actors.Reactor$$anonfun$seq$1$$anonfun$apply$1.apply(Reactor.scala:259) at scala.actors.ReactorTask.run(ReactorTask.scala:36) at scala.actors.ReactorTask.compute(ReactorTask.scala:74) at scala.concurrent.forkjoin.RecursiveAction.exec(RecursiveAction.java:147) at scala.concurrent.forkjoin.ForkJoinTask.quietlyExec(ForkJoinTask.java:422) at scala.concurrent.forkjoin.ForkJoinWorkerThread.mainLoop(ForkJoinWorkerThread.java:340) at scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:325) Is there something else I'm missing in my config or I should check on? Thanks, Jeff

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• Liferay 5.1.1 solr plugin ClassCastException

  - by Mustafa Zidan

  solr-pulgin throw the following exception [SolrIndexSearcherImpl:79] Error while sending request to Solr java.lang.ClassCastException: com.liferay.portal.kernel.util.HttpUtil cannot be cast to com.liferay.portal.kernel.util.HttpUtil at com.liferay.portal.kernel.util.HttpUtil._getUtil(HttpUtil.java:317) at com.liferay.portal.kernel.util.HttpUtil.getHttp(HttpUtil.java:96) at com.liferay.portal.kernel.util.HttpUtil.addParameter(HttpUtil.java:68) at com.liferay.portal.search.solr.SolrIndexSearcherImpl.search(SolrIndexSearcherImpl.java:71) at com.liferay.portal.search.solr.SolrSearchEngineUtil.search(SolrSearchEngineUtil.java:78) at com.liferay.portal.search.solr.messaging.SolrReaderMessageListener.doCommandSearch(SolrReaderMessageListener.java:92) at com.liferay.portal.search.solr.messaging.SolrReaderMessageListener.doReceive(SolrReaderMessageListener.java:75) at com.liferay.portal.search.solr.messaging.SolrReaderMessageListener.receive(SolrReaderMessageListener.java:46) at com.liferay.portal.kernel.messaging.InvokerMessageListener.receive(InvokerMessageListener.java:69) at com.liferay.portal.kernel.messaging.ParallelDestination$1.run(ParallelDestination.java:59) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) at java.lang.Thread.run(Thread.java:619) 16:08:16,174 ERROR [SolrReaderMessageListener:49] Unable to process message com.liferay.portal.kernel.messaging.Message@2c591d98 com.liferay.portal.kernel.search.SearchException: java.lang.ClassCastException: com.liferay.portal.kernel.util.HttpUtil cannot be cast to com.liferay.portal.kernel.util.HttpUtil at com.liferay.portal.search.solr.SolrIndexSearcherImpl.search(SolrIndexSearcherImpl.java:81) at com.liferay.portal.search.solr.SolrSearchEngineUtil.search(SolrSearchEngineUtil.java:78) at com.liferay.portal.search.solr.messaging.SolrReaderMessageListener.doCommandSearch(SolrReaderMessageListener.java:92) at com.liferay.portal.search.solr.messaging.SolrReaderMessageListener.doReceive(SolrReaderMessageListener.java:75) at com.liferay.portal.search.solr.messaging.SolrReaderMessageListener.receive(SolrReaderMessageListener.java:46) at com.liferay.portal.kernel.messaging.InvokerMessageListener.receive(InvokerMessageListener.java:69) at com.liferay.portal.kernel.messaging.ParallelDestination$1.run(ParallelDestination.java:59) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) can anyone help me on this

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• DateFormat conversion problem in java?

  - by androidbase Praveen

  my input String is : 2010-03-24T17:28:50.000Z output pattern is like: DateFormat formatter1 = new SimpleDateFormat("EEE. MMM. d. yyyy"); i convert this like this: formatter1.format(new Date("2010-03-24T17:28:50.000Z"));//illegalArgumentException here the string "2010-03-24T17:28:50.000Z" ouput should be like this: Thu. Mar. 24. 2010 idea but i get a illegalArgumentException. Dont know why? any idea?? stacktrace message is: 04-08 19:50:28.326: WARN/System.err(306): java.lang.IllegalArgumentException 04-08 19:50:28.345: WARN/System.err(306): at java.util.Date.parse(Date.java:447) 04-08 19:50:28.355: WARN/System.err(306): at java.util.Date.<init>(Date.java:157) 04-08 19:50:28.366: WARN/System.err(306): at com.example.brown.Bru_Tube$SelectDataTask.doInBackground(Bru_Tube.java:222) 04-08 19:50:28.366: WARN/System.err(306): at com.example.brown.Bru_Tube$SelectDataTask.doInBackground(Bru_Tube.java:1) 04-08 19:50:28.405: WARN/System.err(306): at android.os.AsyncTask$2.call(AsyncTask.java:185) 04-08 19:50:28.415: WARN/System.err(306): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305) 04-08 19:50:28.415: WARN/System.err(306): at java.util.concurrent.FutureTask.run(FutureTask.java:137) 04-08 19:50:28.446: WARN/System.err(306): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1068) 04-08 19:50:28.456: WARN/System.err(306): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:561) 04-08 19:50:28.466: WARN/System.err(306): at java.lang.Thread.run(Thread.java:1096)

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• Annoying Twisted Python problem

  - by Kalmi

  I'm trying to answer the following question out of personal interest: What is the fastest way to send 100,000 HTTP requests in Python? And this is what I have came up so far, but I'm experiencing something very stange. When installSignalHandlers is True, it just hangs. I can see that the DelayedCall instances are in reactor._newTimedCalls, but processResponse never gets called. When installSignalHandlers is False, it throws an error and works. from twisted.internet import reactor from twisted.web.client import Agent from threading import Semaphore, Thread import time concurrent = 100 s = Semaphore(concurrent) reactor.suggestThreadPoolSize(concurrent) t=Thread( target=reactor.run, kwargs={'installSignalHandlers':True}) t.daemon=True t.start() agent = Agent(reactor) def processResponse(response,url): print response.code, url s.release() def processError(response,url): print "error", url s.release() def addTask(url): req = agent.request('HEAD', url) req.addCallback(processResponse, url) req.addErrback(processError, url) for url in open('urllist.txt'): addTask(url.strip()) s.acquire() while s._Semaphore__value!=concurrent: time.sleep(0.1) reactor.stop() And here is the error that it throws when installSignalHandlers is True: (Note: This is the expected behaviour! The question is why it doesn't work when installSignalHandlers is False.) Traceback (most recent call last): File "/usr/lib/python2.6/dist-packages/twisted/internet/base.py", line 396, in fireEvent DeferredList(beforeResults).addCallback(self._continueFiring) File "/usr/lib/python2.6/dist-packages/twisted/internet/defer.py", line 224, in addCallback callbackKeywords=kw) File "/usr/lib/python2.6/dist-packages/twisted/internet/defer.py", line 213, in addCallbacks self._runCallbacks() File "/usr/lib/python2.6/dist-packages/twisted/internet/defer.py", line 371, in _runCallbacks self.result = callback(self.result, *args, **kw) --- <exception caught here> --- File "/usr/lib/python2.6/dist-packages/twisted/internet/base.py", line 409, in _continueFiring callable(*args, **kwargs) File "/usr/lib/python2.6/dist-packages/twisted/internet/base.py", line 1165, in _reallyStartRunning self._handleSignals() File "/usr/lib/python2.6/dist-packages/twisted/internet/base.py", line 1105, in _handleSignals signal.signal(signal.SIGINT, self.sigInt) exceptions.ValueError: signal only works in main thread What am I doing wrong and what is the right way? I'm new to twisted.

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• reactor not working when reactor.run is not called in the main thread and installSignalHandlers=Fals

  - by Kalmi

  I'm trying to answer the following question out of personal interest: What is the fastest way to send 100,000 HTTP requests in Python? And this is what I have came up so far, but I'm experiencing something very stange. When installSignalHandlers is True, it just hangs. I can see that the DelayedCall instances are in reactor._newTimedCalls, but processResponse never gets called. When installSignalHandlers is False, it throws an error and works. from twisted.internet import reactor from twisted.web.client import Agent from threading import Semaphore, Thread import time concurrent = 100 s = Semaphore(concurrent) reactor.suggestThreadPoolSize(concurrent) t=Thread( target=reactor.run, kwargs={'installSignalHandlers':True}) t.daemon=True t.start() agent = Agent(reactor) def processResponse(response,url): print response.code, url s.release() def processError(response,url): print "error", url s.release() def addTask(url): req = agent.request('HEAD', url) req.addCallback(processResponse, url) req.addErrback(processError, url) for url in open('urllist.txt'): addTask(url.strip()) s.acquire() while s._Semaphore__value!=concurrent: time.sleep(0.1) reactor.stop() And here is the error that it throws when installSignalHandlers is True: (Note: This is the expected behaviour! The question is why it doesn't work when installSignalHandlers is False.) Traceback (most recent call last): File "/usr/lib/python2.6/dist-packages/twisted/internet/base.py", line 396, in fireEvent DeferredList(beforeResults).addCallback(self._continueFiring) File "/usr/lib/python2.6/dist-packages/twisted/internet/defer.py", line 224, in addCallback callbackKeywords=kw) File "/usr/lib/python2.6/dist-packages/twisted/internet/defer.py", line 213, in addCallbacks self._runCallbacks() File "/usr/lib/python2.6/dist-packages/twisted/internet/defer.py", line 371, in _runCallbacks self.result = callback(self.result, *args, **kw) --- <exception caught here> --- File "/usr/lib/python2.6/dist-packages/twisted/internet/base.py", line 409, in _continueFiring callable(*args, **kwargs) File "/usr/lib/python2.6/dist-packages/twisted/internet/base.py", line 1165, in _reallyStartRunning self._handleSignals() File "/usr/lib/python2.6/dist-packages/twisted/internet/base.py", line 1105, in _handleSignals signal.signal(signal.SIGINT, self.sigInt) exceptions.ValueError: signal only works in main thread What am I doing wrong and what is the right way? I'm new to twisted.

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• GC output clarification

  - by elec

  I'm running a java application with the following settings: -XX:+CMSParallelRemarkEnabled -XX:+UseConcMarkSweepGC -XX:+UseParNewGC -XX:+PrintGCApplicationStoppedTime -XX:+PrintGCApplicationConcurrentTime -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:+PrintGCDateStamps -XX:+PrintHeapAtGC -XX:+PrintTenuringDistribution I'm not sure how to interpret the related gc logs(below). In particular: Heap after GC invocations=31 (full 3): does this mean there were 31 minor GCs, and 3 full GCs ? What triggers the several consecutive lines of Total time for which the application threads were stopped and Application Time ? Is it possible to get the time stamps associated with each of these lines ? GC logs: Total time for which application threads were stopped: 0.0046910 seconds Application time: 0.7946670 seconds Total time for which application threads were stopped: 0.0002900 seconds Application time: 1.0153640 seconds Total time for which application threads were stopped: 0.0002780 seconds Application time: 1.0161890 seconds Total time for which application threads were stopped: 0.0002760 seconds Application time: 1.0145990 seconds Total time for which application threads were stopped: 0.0002950 seconds Application time: 0.9999800 seconds Total time for which application threads were stopped: 0.0002770 seconds Application time: 1.0151640 seconds Total time for which application threads were stopped: 0.0002730 seconds Application time: 0.9996590 seconds Total time for which application threads were stopped: 0.0002880 seconds Application time: 0.9624290 seconds {Heap before GC invocations=30 (full 3): par new generation total 131008K, used 130944K [0x00000000eac00000, 0x00000000f2c00000, 0x00000000f2c00000) eden space 130944K, 100% used [0x00000000eac00000, 0x00000000f2be0000, 0x00000000f2be0000) from space 64K, 0% used [0x00000000f2bf0000, 0x00000000f2bf0000, 0x00000000f2c00000) to space 64K, 0% used [0x00000000f2be0000, 0x00000000f2be0000, 0x00000000f2bf0000) concurrent mark-sweep generation total 131072K, used 48348K [0x00000000f2c00000, 0x00000000fac00000, 0x00000000fac00000) concurrent-mark-sweep perm gen total 30000K, used 19518K [0x00000000fac00000, 0x00000000fc94c000, 0x0000000100000000) 2010-05-11T09:30:13.888+0100: 384.955: [GC 384.955: [ParNew Desired survivor size 32768 bytes, new threshold 0 (max 0) : 130944K-0K(131008K), 0.0052470 secs] 179292K-48549K(262080K), 0.0053030 secs] [Times: user=0.00 sys=0.00, real=0.01 secs] Heap after GC invocations=31 (full 3): par new generation total 131008K, used 0K [0x00000000eac00000, 0x00000000f2c00000, 0x00000000f2c00000) eden space 130944K, 0% used [0x00000000eac00000, 0x00000000eac00000, 0x00000000f2be0000) from space 64K, 0% used [0x00000000f2be0000, 0x00000000f2be0000, 0x00000000f2bf0000) to space 64K, 0% used [0x00000000f2bf0000, 0x00000000f2bf0000, 0x00000000f2c00000) concurrent mark-sweep generation total 131072K, used 48549K [0x00000000f2c00000, 0x00000000fac00000, 0x00000000fac00000) concurrent-mark-sweep perm gen total 30000K, used 19518K [0x00000000fac00000, 0x00000000fc94c000, 0x0000000100000000) } Total time for which application threads were stopped: 0.0056410 seconds Application time: 0.0475220 seconds Total time for which application threads were stopped: 0.0001800 seconds Application time: 1.0174830 seconds Total time for which application threads were stopped: 0.0003820 seconds Application time: 1.0126350 seconds Total time for which application threads were stopped: 0.0002750 seconds Application time: 1.0155910 seconds Total time for which application threads were stopped: 0.0002680 seconds Application time: 1.0155580 seconds Total time for which application threads were stopped: 0.0002880 seconds Application time: 1.0155480 seconds Total time for which application threads were stopped: 0.0002970 seconds Application time: 0.9896810 seconds

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• Which Stroustrup book should I use?

  - by Chris Simmons

  I'm a C# programmer that is looking to branch out. I'm bored of writing business software and want to start getting into graphics programming and games/simulators. So I figured, although writing that stuff isn't impossible in managed code, the "right" way to do that would be to look to C++, of course focussing on the language first, then getting into OpenGL or DirectX (or whatever). Way way back ('98? '99?) I had tried and failed to really grasp Stroustrup's The C++ Programming Language. I know that this book is often not recommended for the beginner. Anyway, I picked it back up (in a much more recent printing) and I'm actually getting it and enjoying it. I also have a copy of his textbook, Programming: Principles and Practice Using C++, which, as I understand it, is really geared toward teaching programming, not necessarily C++. I'm certainly not arrogant enough to claim I don't have anything more to learn about programming, data structures, algoriths, etc., however I'm not a novice there either. So my question is, with the goal of gaining the broader and more real-world-useful understanding of C++ and given my background, on which should I focus? The denser (as I perceive it) TCPPPL or the gentler Programming? EDIT: I thank everyone for the responses. However, I've got a personal choice here to make between these two books. Granted there are other very good books out there, but I'm already a good length into both of the books I mention and I'd like to finish one. So, can anyone respond on which would be the better and why? Time is not an issue; I'm not looking (at this point) at an "accelerated" read.

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• Mono for Android Book has been Released!!!!!

  - by Wallym

  If I understand things correctly, and I make no guarantees that I do, our Mono for Android book has been RELEASED!  I'm not quite sure what this means, but my guess is that that it has been printed and is being shipped to various book sellers.So, if you have pre-ordered a copy, its now up to Amazon to send it to you.  Its fully out of my control, Wrox, Wiley, as well as everyone but Amazon.If you haven't bought a copy already, why?  Seriously, go order 8-10 copies for the ones you love.  They'll make great romantic gifts for the ones you love.  Just think at the look on the other person's face when you give them a copy of our book. Here's a little about the book:The wait is over! For the millions of .NET/C# developers who have been eagerly awaiting the book that will guide them through the white-hot field of Android application programming, this is the book. As the first guide to focus on Mono for Android, this must-have resource dives into writing applications against Mono with C# and compiling executables that run on the Android family of devices.Putting the proven Wrox Professional format into practice, the authors provide you with the knowledge you need to become a successful Android application developer without having to learn another programming language. You'll explore screen controls, UI development, tables and layouts, and MonoDevelop as you become adept at developing Android applications with Mono for Android.Develop Android apps using tools you already know—C# and .NETAimed at providing readers with a thorough, reliable resource that guides them through the field of Android application programming, this must-have book shows how to write applications using Mono with C# that run on the Android family of devices. A team of authors provides you with the knowledge you need to become a successful Android application developer without having to learn another programming language. You'll explore screen controls, UI development, tables and layouts, and MonoDevelop as you become adept at planning, building, and developing Android applications with Mono for Android.Professional Android Programming with Mono for Android and .NET/C#:Shows you how to use your existing C# and .NET skills to build Android appsDetails optimal ways to work with data and bind data to controlsExplains how to program with Android device hardwareDives into working with the file system and application preferencesDiscusses how to share code between Mono for Android, MonoTouch, and Windows® Phone 7Reveals tips for globalizing your apps with internationalization and localization supportCovers development of tablet apps with Android 4Wrox Professional guides are planned and written by working programmers to meet the real-world needs of programmers, developers, and IT professionals. Focused and relevant, they address the issues technology professionals face every day. They provide examples, practical solutions, and expert education in new technologies, all designed to help programmers do a better job.Now, go buy a bunch of copies!!!!!If you are interested in iPhone and Android and would like to get a little more knowledgeable in the area of development, you can purchase the 3 pack of books from Wrox on Mobile Development with Mono.  This will cover MonoTouch, Mono for Android, and cross platform methods for using both tools.  A great package in and of itself.  The name of that package is: Wrox Cross Platform Android and iOS Mobile Development Three-Pack 

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• How to interview a natural scientist for a dev position?

  - by Silas

  I already did some interviews for my company, mostly computer scientists for dev positions but also some testers and project managers. Now I have to fill a vacancy in our research group within the R&D department (side note: “research” means that we try to solve problems in our professional domain/market niche using software in research projects together with universities, other companies, research centres and end user organisations. It’s not computer science research; we’re not going to solve the P=NP problem). Now we invited a guy holding an MSc in chemistry (with a lot of physics in his CV, too), who never had any computer science lesson. I already talked with him about half an hour at a local university’s career days and there’s no doubt the guy is smart. Also his marks are excellent and he graduated with distinction. For his BSc he needed to teach himself programming in Mathematica and told me believably that he liked programming a lot. Also he solved some physical chemistry problem that I probably don’t understand using his own software, implemented in Mathematica, for his MSc thesis. It includes a GUI and a notable size of 8,000 LoC. He seems to be very attracted by what we’re doing in our research group and to be honest it’s quite difficult for an SME like us to get good people. I also am very interested in hiring him since he could assist me in writing project proposals, reports, doing presentations and so on. He would probably fit to our team, too. The only question left is: How can I check if he will get the programming skills he needs to do software implementation in our projects since this will be a significant part of the job? Of course I will ask him what it is, that is fascinating him about programming. I’ll also ask how he proceeded to write his natural science software and how he structured it. I’ll ask about how he managed to obtain the skills and information about software development he needed. But is there something more I could ask? Something more concrete perhaps? Should I ask him to explain his Mathematica solution? To be clear: I’m not looking for knowledge in a particular language or technology stack. We’re a .NET shop in product development but I want to have a free choice for our research projects. So I’m interested in the meta-competence being able to learn whatever is actually needed. I hope this question is answerable and not open-ended since I really like to know if there is a default way to check for the ability to get further programming skills on the job. If something is not clear to you please give me some comments and let me improve my question.

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• Interesting Topics in Comp. Sci. for New Students?

  - by SoulBeaver

  I hope this is the right forum to ask this question. Last friday I was in a discussion with my professors about the students' lack of motivation and interest in the field of Computer Science. All of the students are enrolled, but through questionnaires and other questions that my professor posed it was revealed that over 90% of all enrolled students are just in it for the reward of getting a job sometime in the future (since it's a growing field with high job potential) I asked my professor for the permission to take over the first couple of lectures and try and motivate, interest and inspire students for the field of Computer Science and programming in particular (this is the Intro to Programming course). This request was granted and I now have a week to come up with a lecture topic for my professor's five groups. My main goal isn't to teach, I just want to get students to be as interested in the field as I am. I want to show them what's possible, what awesome magical things have been done in the field, the future we are heading towards using programming and Comp. Sci. Therefore, I would like to pose this question: I have a few topics, materials and sample projects that I would like to talk about: -- Grace Hopper (It is my hope to interest the female programmers in the class. There are never more than two or three per group and they, more than males, are prone to jumping ship and abandoning Comp. Sci.) -- The Singularity Institute -- Alan Turing -- Robotics -- Programming not as a chore or a must, but the idea that we are, at our core, the nexus to which anything anybody does in the digital world is connected to. We are the problem solvers; we assemble all the parts together and we are the ones that, essentially, make the vision a reality. -- Give them an idea for a programming project which, through the help of the professor, could be significant to every student (I want students to not only feel interested in the topic, but they should feel important, that what they do here makes a difference) Do you have interesting topics worthy of discussion, something I can tell the students which they can get interested about? How would you approach the lecture? If you had 90 minutes worth of time to try and get students interested in the project, what would you do?

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• Fatal Exception : AsyncTask #1

  - by Nadirah Ibtisam

  help help..huu Im having a problem here..seems there was no error in codes..but when I run it...and click button to view map consist routing the map..It appers to be close all of sudden..why is that? Please help me friends.. Im developing an app to read my current location and creating route to A position.. here are the codes: public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.map); onNewIntent(getIntent()); Drawable marker = getResources().getDrawable(R.drawable.marker); Drawable marked_places = getResources().getDrawable(R.drawable.feringgi_map); mymap = (MapView)findViewById(R.id.mymap); controller = mymap.getController(); // extract MapView from layout mymap.getController().setZoom(15); mymap.setBuiltInZoomControls(true); mymap.setSatellite(false); // create an overlay that shows our current location myLocationOverlay = new MyLocationOverlay(this, mymap); // add this overlay to the MapView and refresh it mymap.getOverlays().add(myLocationOverlay); mymap.postInvalidate(); myLocationOverlay.runOnFirstFix(new Runnable() { @Override public void run() { controller.setZoom(10); controller.animateTo(myLocationOverlay.getMyLocation()); } }); zoomToMyLocation(); switch(selecteditem) { case 0: switch(selectedsubitem){ case 0://Place A locationManager = (LocationManager) this.getSystemService(Context.LOCATION_SERVICE); locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0, this); Location location = locationManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER); if (location !=null) { loc=location; } GeoPoint destination = getPoint(3.144341, 101.69541800000002); new BackgroundTask(this, loc, destination).execute(); break; } } class BackgroundTask extends AsyncTask<Void, Void, Void> { private Location location; private GeoPoint dest; private Route route; private Activity activity; private ProgressDialog dialog; private RouteOverlay routeOverlay; public BackgroundTask(Activity activity, Location loc, GeoPoint dest) { location=loc; this.dest=dest; this.activity=activity; dialog = new ProgressDialog(activity); } @Override protected void onPreExecute() { dialog.setCancelable(false); dialog.setTitle("Loading..."); dialog.setMessage("Calculating Route..."); dialog.setButton("Cancel", new DialogInterface.OnClickListener() { public void onClick(final DialogInterface dialog, final int id) { cancel(true); MyMap.this.finish(); }}); dialog.show(); } protected Void doInBackground(Void... params) { if(isNetworkAvailable()) { if(haveInternet()) { try{ route = directions(new GeoPoint((int)(location.getLatitude()*1.0E6),(int)(location.getLongitude()*1.0E6)), dest); } catch (NullPointerException e){ } } else { return null; } } else { return null; } return null; } And this is the log cat (updated).. : 12-10 12:21:15.527: E/AndroidRuntime(10146): FATAL EXCEPTION: AsyncTask #1 12-10 12:21:15.527: E/AndroidRuntime(10146): java.lang.RuntimeException: An error occured while executing doInBackground() 12-10 12:21:15.527: E/AndroidRuntime(10146): at android.os.AsyncTask$3.done(AsyncTask.java:278) 12-10 12:21:15.527: E/AndroidRuntime(10146): at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273) 12-10 12:21:15.527: E/AndroidRuntime(10146): at java.util.concurrent.FutureTask.setException(FutureTask.java:124) 12-10 12:21:15.527: E/AndroidRuntime(10146): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307) 12-10 12:21:15.527: E/AndroidRuntime(10146): at java.util.concurrent.FutureTask.run(FutureTask.java:137) 12-10 12:21:15.527: E/AndroidRuntime(10146): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:208) 12-10 12:21:15.527: E/AndroidRuntime(10146): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076) 12-10 12:21:15.527: E/AndroidRuntime(10146): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569) 12-10 12:21:15.527: E/AndroidRuntime(10146): at java.lang.Thread.run(Thread.java:856) 12-10 12:21:15.527: E/AndroidRuntime(10146): Caused by: java.lang.SecurityException: ConnectivityService: Neither user 10228 nor current process has android.permission.ACCESS_NETWORK_STATE. 12-10 12:21:15.527: E/AndroidRuntime(10146): at android.os.Parcel.readException(Parcel.java:1327) 12-10 12:21:15.527: E/AndroidRuntime(10146): at android.os.Parcel.readException(Parcel.java:1281) 12-10 12:21:15.527: E/AndroidRuntime(10146): at android.net.IConnectivityManager$Stub$Proxy.getActiveNetworkInfo(IConnectivityManager.java:728) 12-10 12:21:15.527: E/AndroidRuntime(10146): at android.net.ConnectivityManager.getActiveNetworkInfo(ConnectivityManager.java:378) 12-10 12:21:15.527: E/AndroidRuntime(10146): at com.madcatworld.testtesttest.MyMap$BackgroundTask.isNetworkAvailable(MyMap.java:488) 12-10 12:21:15.527: E/AndroidRuntime(10146): at com.madcatworld.testtesttest.MyMap$BackgroundTask.doInBackground(MyMap.java:411) 12-10 12:21:15.527: E/AndroidRuntime(10146): at com.madcatworld.testtesttest.MyMap$BackgroundTask.doInBackground(MyMap.java:1) 12-10 12:21:15.527: E/AndroidRuntime(10146): at android.os.AsyncTask$2.call(AsyncTask.java:264) 12-10 12:21:15.527: E/AndroidRuntime(10146): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305) 12-10 12:21:15.527: E/AndroidRuntime(10146): ... 5 more This is my manifest file: <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.madcatworld.testtesttest" android:versionCode="1" android:versionName="1.0" > <uses-sdk android:minSdkVersion="8" android:targetSdkVersion="15" /> <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/> <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/> <uses-permission android:name="android.permission.INTERNET"/> <uses-permission android:name="android.permission.CALL_PHONE"/> <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/> <application android:icon="@drawable/ic_launcher" android:label="@string/app_name" android:theme="@style/AppTheme" > <com.google.android.maps.MapView android:id="@+id/mymap" android:clickable="true" android:layout_width="fill_parent" android:layout_height="fill_parent" android:apiKey="XXXX" /> <activity android:theme="@style/StyledIndicators" android:name=".MainTest" android:label="@string/title_activity_main" android:screenOrientation="portrait"> <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> <uses-library android:name="com.google.android.maps"/> <activity android:name="A" android:screenOrientation="portrait"></activity> <activity android:name="B" android:screenOrientation="portrait"></activity> <activity android:name="C" android:screenOrientation="portrait"></activity> </application> </manifest> For your information, I already put ACCESS_NETWORK_STATE in my manifest.. Can u discover what cause the error? No error in code..but it failed to review my route map..:( Thanks Friends

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• Edit Contact code worked in 1.6 but doesn't work on Droid 2.1?

  - by user225405

  Hi All, I had some fairly simple code in my app to invoke Edit Contact activity on a known good contact index that worked in Android 1.6 but is broken for me now in Android 2.1 on the Droid. I built a sample activity/app 'EdCon' to show this: package com.jbh; import android.app.Activity; import android.content.Intent; import android.net.Uri; import android.os.Bundle; public class EdCon extends Activity { /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); // Build an intent to edit a known good contact index Intent i; i = new Intent(Intent.ACTION_EDIT); i.setData(Uri.parse("content://contacts/people/10")); startActivity(i); } } When I run this on my G1 running 1.6 it works as expected i.e. brings up the Edit Contact screen for the known index and then I can hit BACK to return to "Hello World, EdCon". When I run this on the Droid under 2.1 I get the following: 05-07 15:35:57.787: INFO/ActivityManager(1013): Starting activity: Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10000000 cmp=com.jbh/.EdCon } 05-07 15:35:57.826: DEBUG/AndroidRuntime(13780): Shutting down VM 05-07 15:35:57.826: DEBUG/dalvikvm(13780): DestroyJavaVM waiting for non-daemon threads to exit 05-07 15:35:57.928: DEBUG/dalvikvm(13780): DestroyJavaVM shutting VM down 05-07 15:35:57.928: DEBUG/dalvikvm(13780): HeapWorker thread shutting down 05-07 15:35:57.928: DEBUG/dalvikvm(13780): HeapWorker thread has shut down 05-07 15:35:57.928: DEBUG/jdwp(13780): JDWP shutting down net... 05-07 15:35:57.928: DEBUG/jdwp(13780): Got wake-up signal, bailing out of select 05-07 15:35:57.928: INFO/dalvikvm(13780): Debugger has detached; object registry had 1 entries 05-07 15:35:57.928: DEBUG/dalvikvm(13780): VM cleaning up 05-07 15:35:57.935: INFO/ActivityManager(1013): Start proc com.jbh for activity com.jbh/.EdCon: pid=13802 uid=10052 gids={1015} 05-07 15:35:57.967: ERROR/AndroidRuntime(13780): ERROR: thread attach failed 05-07 15:35:58.053: INFO/ActivityThread(13792): Publishing provider com.android.vending.SuggestionsProvider: com.android.vending.SuggestionsProvider 05-07 15:35:58.154: INFO/dalvikvm(13802): Debugger thread not active, ignoring DDM send (t=0x41504e4d l=38) 05-07 15:35:58.209: DEBUG/dalvikvm(13780): LinearAlloc 0x0 used 639500 of 5242880 (12%) 05-07 15:35:58.365: INFO/dalvikvm(13802): Debugger thread not active, ignoring DDM send (t=0x41504e4d l=18) 05-07 15:35:58.639: INFO/ActivityManager(1013): Starting activity: Intent { act=android.intent.action.EDIT dat=content://contacts/people/10 cmp=com.android.contacts/.ui.EditContactActivity } 05-07 15:35:58.975: DEBUG/dalvikvm(13137): GC freed 2902 objects / 166768 bytes in 61ms 05-07 15:35:59.100: DEBUG/vending(13792): com.android.vending.LocalDbSyncService.run(): Syncing local DB with package manager... 05-07 15:35:59.100: DEBUG/vending(13792): com.android.vending.LocalDbSyncService.syncLocalDbWithPackageManager(): No INSTALLING or UNINSTALLING assets. 05-07 15:35:59.115: INFO/ActivityManager(1013): Displayed activity com.android.contacts/.ui.EditContactActivity: 387 ms (total 1296 ms) 05-07 15:35:59.185: DEBUG/Sources(13137): Creating external source for type=com.facebook.auth.login, packageName=com.facebook.katana 05-07 15:35:59.225: DEBUG/vending(13792): com.android.vending.LocalDbSyncService.run(): Syncing done. 05-07 15:35:59.232: WARN/dalvikvm(13137): threadid=27: thread exiting with uncaught exception (group=0x4001b180) 05-07 15:35:59.232: ERROR/AndroidRuntime(13137): Uncaught handler: thread AsyncTask #1 exiting due to uncaught exception 05-07 15:35:59.295: ERROR/AndroidRuntime(13137): java.lang.RuntimeException: An error occured while executing doInBackground() 05-07 15:35:59.295: ERROR/AndroidRuntime(13137): at android.os.AsyncTask$3.done(AsyncTask.java:200) 05-07 15:35:59.295: ERROR/AndroidRuntime(13137): at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273) 05-07 15:35:59.295: ERROR/AndroidRuntime(13137): at java.util.concurrent.FutureTask.setException(FutureTask.java:124) 05-07 15:35:59.295: ERROR/AndroidRuntime(13137): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307) 05-07 15:35:59.295: ERROR/AndroidRuntime(13137): at java.util.concurrent.FutureTask.run(FutureTask.java:137) 05-07 15:35:59.295: ERROR/AndroidRuntime(13137): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1068) 05-07 15:35:59.295: ERROR/AndroidRuntime(13137): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:561) 05-07 15:35:59.295: ERROR/AndroidRuntime(13137): at java.lang.Thread.run(Thread.java:1096) 05-07 15:35:59.295: ERROR/AndroidRuntime(13137): Caused by: android.database.sqlite.SQLiteException: no such column: raw_contact_id: , while compiling: SELECT account_name, account_type, sourceid, version, dirty, data_id, res_package, mimetype, data1, data2, data3, data4, data5, data6, data7, data8, data9, data10, data11, data12, data13, data14, data15, data_sync1, data_sync2, data_sync3, data_sync4, _id, is_primary, is_super_primary, data_version, group_sourceid, sync1, sync2, sync3, sync4, deleted, contact_id, starred, is_restricted FROM contact_entities_view WHERE (1) AND (raw_contact_id=10) 05-07 15:35:59.295: ERROR/AndroidRuntime(13137): at android.database.sqlite.SQLiteProgram.native_compile(Native Method) 05-07 15:35:59.295: ERROR/AndroidRuntime(13137): at android.database.sqlite.SQLiteProgram.compile(SQLiteProgram.java:110) 05-07 15:35:59.295: ERROR/AndroidRuntime(13137): at android.database.sqlite.SQLiteProgram.(SQLiteProgram.java:59) 05-07 15:35:59.295: ERROR/AndroidRuntime(13137): at android.database.sqlite.SQLiteQuery.(SQLiteQuery.java:49) 05-07 15:35:59.295: ERROR/AndroidRuntime(13137): at android.database.sqlite.SQLiteDirectCursorDriver.query(SQLiteDirectCursorDriver.java:49) 05-07 15:35:59.295: ERROR/AndroidRuntime(13137): at android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1221) 05-07 15:35:59.295: ERROR/AndroidRuntime(13137): at android.database.sqlite.SQLiteQueryBuilder.query(SQLiteQueryBuilder.java:316) 05-07 15:35:59.295: ERROR/AndroidRuntime(13137): at com.android.providers.contacts.ContactsProvider2.query(ContactsProvider2.java:3850) 05-07 15:35:59.295: ERROR/AndroidRuntime(13137): at com.android.providers.contacts.ContactsProvider2.query(ContactsProvider2.java:3840) 05-07 15:35:59.295: ERROR/AndroidRuntime(13137): at com.android.providers.contacts.ContactsProvider2$RawContactsEntityIterator.(ContactsProvider2.java:4498) 05-07 15:35:59.295: ERROR/AndroidRuntime(13137): at com.android.providers.contacts.ContactsProvider2.queryEntities(ContactsProvider2.java:4751) 05-07 15:35:59.295: ERROR/AndroidRuntime(13137): at android.content.ContentProvider$Transport.queryEntities(ContentProvider.java:140) 05-07 15:35:59.295: ERROR/AndroidRuntime(13137): at android.content.ContentProviderClient.queryEntities(ContentProviderClient.java:98) 05-07 15:35:59.295: ERROR/AndroidRuntime(13137): at android.content.ContentResolver.queryEntities(ContentResolver.java:296) 05-07 15:35:59.295: ERROR/AndroidRuntime(13137): at com.android.contacts.model.EntitySet.fromQuery(EntitySet.java:72) 05-07 15:35:59.295: ERROR/AndroidRuntime(13137): at com.android.contacts.ui.EditContactActivity$QueryEntitiesTask.doInBackground(EditContactActivity.java:191) 05-07 15:35:59.295: ERROR/AndroidRuntime(13137): at com.android.contacts.ui.EditContactActivity$QueryEntitiesTask.doInBackground(EditContactActivity.java:154) 05-07 15:35:59.295: ERROR/AndroidRuntime(13137): at com.android.contacts.util.WeakAsyncTask.doInBackground(WeakAsyncTask.java:45) 05-07 15:35:59.295: ERROR/AndroidRuntime(13137): at android.os.AsyncTask$2.call(AsyncTask.java:185) 05-07 15:35:59.295: ERROR/AndroidRuntime(13137): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305) 05-07 15:35:59.295: ERROR/AndroidRuntime(13137): ... 4 more 05-07 15:35:59.303: INFO/Process(1013): Sending signal. PID: 13137 SIG: 3 05-07 15:35:59.303: INFO/dalvikvm(13137): threadid=7: reacting to signal 3 05-07 15:35:59.303: ERROR/dalvikvm(13137): Unable to open stack trace file '/data/anr/traces.txt': Permission denied 05-07 15:35:59.506: INFO/DumpStateReceiver(1013): Added state dump to 1 crashes 05-07 15:36:07.053: DEBUG/dalvikvm(12901): GC freed 389 objects / 25056 bytes in 145ms 05-07 15:36:17.287: DEBUG/dalvikvm(11649): GC freed 154 objects / 6816 bytes in 136ms 05-07 15:36:22.365: DEBUG/dalvikvm(13574): GC freed 348 objects / 67848 bytes in 112ms 05-07 15:36:27.451: DEBUG/dalvikvm(11836): GC freed 267 objects / 17432 bytes in 65ms 05-07 15:36:32.553: DEBUG/dalvikvm(12757): GC freed 1888 objects / 92440 bytes in 67ms 05-07 15:36:38.803: INFO/power(1013): * set_screen_state 0 05-07 15:36:38.813: DEBUG/SurfaceFlinger(1013): About to give-up screen, flinger = 0x114c30 05-07 15:36:38.826: DEBUG/Sensors(1013): using accelerometer (name=accelerometer) 05-07 15:36:38.834: DEBUG/PhoneWindow(13137): couldn't save which view has focus because the focused view android.widget.ScrollView@44883558 has no id. 05-07 15:36:38.865: DEBUG/WifiService(1013): ACTION_SCREEN_OFF 05-07 15:36:38.889: DEBUG/WifiService(1013): setting ACTION_DEVICE_IDLE timer for 900000ms 05-07 15:36:44.107: DEBUG/dalvikvm(1013): GC freed 7351 objects / 521440 bytes in 130ms 05-07 15:36:49.373: DEBUG/dalvikvm(13553): GC freed 321 objects / 12056 bytes in 102ms The no such column: raw_contact_id: looks like the issue but I'm not sure how or why that would happen or what it means. Any help appreciated! [email protected]

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• ActiveMQ - "Cannot send, channel has already failed" every 2 seconds?

  - by quanta

  ActiveMQ 5.7.0 In the activemq.log, I'm seeing this exception every 2 seconds: 2013-11-05 13:00:52,374 | DEBUG | Transport Connection to: tcp://127.0.0.1:37501 failed: org.apache.activemq.transport.InactivityIOException: Cannot send, channel has already failed: tcp://127.0.0.1:37501 | org.apache.activemq.broker.TransportConnection.Transport | Async Exception Handler org.apache.activemq.transport.InactivityIOException: Cannot send, channel has already failed: tcp://127.0.0.1:37501 at org.apache.activemq.transport.AbstractInactivityMonitor.doOnewaySend(AbstractInactivityMonitor.java:282) at org.apache.activemq.transport.AbstractInactivityMonitor.oneway(AbstractInactivityMonitor.java:271) at org.apache.activemq.transport.TransportFilter.oneway(TransportFilter.java:85) at org.apache.activemq.transport.WireFormatNegotiator.oneway(WireFormatNegotiator.java:104) at org.apache.activemq.transport.MutexTransport.oneway(MutexTransport.java:68) at org.apache.activemq.broker.TransportConnection.dispatch(TransportConnection.java:1312) at org.apache.activemq.broker.TransportConnection.processDispatch(TransportConnection.java:838) at org.apache.activemq.broker.TransportConnection.iterate(TransportConnection.java:873) at org.apache.activemq.thread.PooledTaskRunner.runTask(PooledTaskRunner.java:129) at org.apache.activemq.thread.PooledTaskRunner$1.run(PooledTaskRunner.java:47) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) at java.lang.Thread.run(Thread.java:662) Due to this keyword InactivityIOException, the first thing comes to my mind is InactivityMonitor, but the strange thing is MaxInactivityDuration=30000: 2013-11-05 13:11:02,672 | DEBUG | Sending: WireFormatInfo { version=9, properties={MaxFrameSize=9223372036854775807, CacheSize=1024, CacheEnabled=true, SizePrefixDisabled=false, MaxInactivityDurationInitalDelay=10000, TcpNoDelayEnabled=true, MaxInactivityDuration=30000, TightEncodingEnabled=true, StackTraceEnabled=true}, magic=[A,c,t,i,v,e,M,Q]} | org.apache.activemq.transport.WireFormatNegotiator | ActiveMQ BrokerService[localhost] Task-2 Moreover, I also didn't see something like this: No message received since last read check for ... or: Channel was inactive for too (30000) long Do a netstat, I see these connections in TIME_WAIT state: tcp 0 0 127.0.0.1:38545 127.0.0.1:61616 TIME_WAIT - tcp 0 0 127.0.0.1:38544 127.0.0.1:61616 TIME_WAIT - tcp 0 0 127.0.0.1:38522 127.0.0.1:61616 TIME_WAIT - Here're the output when running tcpdump: Internet Protocol Version 4, Src: 127.0.0.1 (127.0.0.1), Dst: 127.0.0.1 (127.0.0.1) Version: 4 Header length: 20 bytes Differentiated Services Field: 0x00 (DSCP 0x00: Default; ECN: 0x00: Not-ECT (Not ECN-Capable Transport)) 0000 00.. = Differentiated Services Codepoint: Default (0x00) .... ..00 = Explicit Congestion Notification: Not-ECT (Not ECN-Capable Transport) (0x00) Total Length: 296 Identification: 0x7b6a (31594) Flags: 0x02 (Don't Fragment) 0... .... = Reserved bit: Not set .1.. .... = Don't fragment: Set ..0. .... = More fragments: Not set Fragment offset: 0 Time to live: 64 Protocol: TCP (6) Header checksum: 0xc063 [correct] [Good: True] [Bad: False] Source: 127.0.0.1 (127.0.0.1) Destination: 127.0.0.1 (127.0.0.1) Transmission Control Protocol, Src Port: 61616 (61616), Dst Port: 54669 (54669), Seq: 1, Ack: 2, Len: 244 Source port: 61616 (61616) Destination port: 54669 (54669) [Stream index: 11] Sequence number: 1 (relative sequence number) [Next sequence number: 245 (relative sequence number)] Acknowledgement number: 2 (relative ack number) Header length: 32 bytes Flags: 0x018 (PSH, ACK) 000. .... .... = Reserved: Not set ...0 .... .... = Nonce: Not set .... 0... .... = Congestion Window Reduced (CWR): Not set .... .0.. .... = ECN-Echo: Not set .... ..0. .... = Urgent: Not set .... ...1 .... = Acknowledgement: Set .... .... 1... = Push: Set .... .... .0.. = Reset: Not set .... .... ..0. = Syn: Not set .... .... ...0 = Fin: Not set Window size value: 256 [Calculated window size: 32768] [Window size scaling factor: 128] Checksum: 0xff1c [validation disabled] [Good Checksum: False] [Bad Checksum: False] Options: (12 bytes) No-Operation (NOP) No-Operation (NOP) Timestamps: TSval 2304161892, TSecr 2304161891 Kind: Timestamp (8) Length: 10 Timestamp value: 2304161892 Timestamp echo reply: 2304161891 [SEQ/ACK analysis] [Bytes in flight: 244] Constrained Application Protocol, TID: 240, Length: 244 00.. .... = Version: 0 ..00 .... = Type: Confirmable (0) .... 0000 = Option Count: 0 Code: Unknown (0) Transaction ID: 240 Payload Content-Type: text/plain (default), Length: 240, offset: 4 Line-based text data: text/plain [truncated] \001ActiveMQ\000\000\000\t\001\000\000\000<DE>\000\000\000\t\000\fMaxFrameSize\006\177<FF><FF><FF><FF> <FF><FF><FF>\000\tCacheSize\005\000\000\004\000\000\fCacheEnabled\001\001\000\022SizePrefixDisabled\001\000\000 MaxInactivityDurationInitalDelay\006\ It is very likely a tcp port check. This is what I see when trying telnet from another host: 2013-11-05 16:12:41,071 | DEBUG | Transport Connection to: tcp://10.8.20.9:46775 failed: java.io.EOFException | org.apache.activemq.broker.TransportConnection.Transport | ActiveMQ Transport: tcp:///10.8.20.9:46775@61616 java.io.EOFException at java.io.DataInputStream.readInt(DataInputStream.java:375) at org.apache.activemq.openwire.OpenWireFormat.unmarshal(OpenWireFormat.java:275) at org.apache.activemq.transport.tcp.TcpTransport.readCommand(TcpTransport.java:229) at org.apache.activemq.transport.tcp.TcpTransport.doRun(TcpTransport.java:221) at org.apache.activemq.transport.tcp.TcpTransport.run(TcpTransport.java:204) at java.lang.Thread.run(Thread.java:662) 2013-11-05 16:12:41,071 | DEBUG | Transport Connection to: tcp://10.8.20.9:46775 failed: org.apache.activemq.transport.InactivityIOException: Cannot send, channel has already failed: tcp://10.8.20.9:46775 | org.apache.activemq.broker.TransportConnection.Transport | Async Exception Handler org.apache.activemq.transport.InactivityIOException: Cannot send, channel has already failed: tcp://10.8.20.9:46775 at org.apache.activemq.transport.AbstractInactivityMonitor.doOnewaySend(AbstractInactivityMonitor.java:282) at org.apache.activemq.transport.AbstractInactivityMonitor.oneway(AbstractInactivityMonitor.java:271) at org.apache.activemq.transport.TransportFilter.oneway(TransportFilter.java:85) at org.apache.activemq.transport.WireFormatNegotiator.oneway(WireFormatNegotiator.java:104) at org.apache.activemq.transport.MutexTransport.oneway(MutexTransport.java:68) at org.apache.activemq.broker.TransportConnection.dispatch(TransportConnection.java:1312) at org.apache.activemq.broker.TransportConnection.processDispatch(TransportConnection.java:838) at org.apache.activemq.broker.TransportConnection.iterate(TransportConnection.java:873) at org.apache.activemq.thread.PooledTaskRunner.runTask(PooledTaskRunner.java:129) at org.apache.activemq.thread.PooledTaskRunner$1.run(PooledTaskRunner.java:47) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) at java.lang.Thread.run(Thread.java:662) 2013-11-05 16:12:41,071 | DEBUG | Unregistering MBean org.apache.activemq:BrokerName=localhost,Type=Connection,ConnectorName=ope nwire,ViewType=address,Name=tcp_//10.8.20.9_46775 | org.apache.activemq.broker.jmx.ManagementContext | ActiveMQ Transport: tcp:/ //10.8.20.9:46775@61616 2013-11-05 16:12:41,073 | DEBUG | Stopping connection: tcp://10.8.20.9:46775 | org.apache.activemq.broker.TransportConnection | ActiveMQ BrokerService[localhost] Task-5 2013-11-05 16:12:41,073 | DEBUG | Stopping transport tcp:///10.8.20.9:46775@61616 | org.apache.activemq.transport.tcp.TcpTranspo rt | ActiveMQ BrokerService[localhost] Task-5 2013-11-05 16:12:41,073 | DEBUG | Initialized TaskRunnerFactory[ActiveMQ Task] using ExecutorService: java.util.concurrent.Threa dPoolExecutor@23cc2a28 | org.apache.activemq.thread.TaskRunnerFactory | ActiveMQ BrokerService[localhost] Task-5 2013-11-05 16:12:41,074 | DEBUG | Closed socket Socket[addr=/10.8.20.9,port=46775,localport=61616] | org.apache.activemq.transpo rt.tcp.TcpTransport | ActiveMQ Task-1 2013-11-05 16:12:41,074 | DEBUG | Forcing shutdown of ExecutorService: java.util.concurrent.ThreadPoolExecutor@23cc2a28 | org.apache.activemq.util.ThreadPoolUtils | ActiveMQ BrokerService[localhost] Task-5 2013-11-05 16:12:41,074 | DEBUG | Stopped transport: tcp://10.8.20.9:46775 | org.apache.activemq.broker.TransportConnection | ActiveMQ BrokerService[localhost] Task-5 2013-11-05 16:12:41,074 | DEBUG | Connection Stopped: tcp://10.8.20.9:46775 | org.apache.activemq.broker.TransportConnection | ActiveMQ BrokerService[localhost] Task-5 2013-11-05 16:12:41,902 | DEBUG | Sending: WireFormatInfo { version=9, properties={MaxFrameSize=9223372036854775807, CacheSize=1024, CacheEnabled=true, SizePrefixDisabled=false, MaxInactivityDurationInitalDelay=10000, TcpNoDelayEnabled=true, MaxInactivityDuration=30000, TightEncodingEnabled=true, StackTraceEnabled=true}, magic=[A,c,t,i,v,e,M,Q]} | org.apache.activemq.transport.WireFormatNegotiator | ActiveMQ BrokerService[localhost] Task-5 So the question is: how can I find out the process that is trying to connect to my ActiveMQ (from localhost) every 2 seconds?

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• Why are there many processes listed under the same title in htop?

  - by javanix

  Can anyone explain to me why there are sometimes 10 or 15 processes with the same title and "stats" listed in htop? I'm guessing there are multiple threads running - but that many of them obviously couldn't be running concurrently. Is there any sort of performance hit taken if a process uses say, 15 non-concurrent threads vs. 10 non-concurrent threads?

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• Is this information about me as a programmer concise and good enough?

  - by Nick Rosencrantz

  I not only want you to review my resume but please tell me what you think Google means when they answered me: "We don't look at personal letters and we like your resume and we can recommend you internally but we need measurable experience. What is meant with "measurable" here? Do they mean like O(1) compared to O(n), selling an entire company, grades or what? This is what I sent: Curriculum vitae Nick Rosencrantz Competence: System development, web development Technical competence: Java, Javascript, HTML, XML, CSS, AJAX, PHP, SQL, Python Employments: 2012- Mobile Innovation AB System Developer IT consultant (Java programmer) 2011-2012 Bnano International Ltd System Developer Python programming in Google App Engine 2008-2009 Sweden Island AB System Developer Programming C++ and Java EE components 2003-2007 Studies Stockholm School of Economics During studies worked as network technician at Effnet AB 2000-2002 Jadestone AB System Developer System development in Java/J2EE. In 2001: KTH, Assistant. Teaching application server programming in Java Enterprise + weblogic + Informix. 1999-2000 Studies KTH 1996-1998 Spray.se System development, Researcher 1995-1995 Finance broker Backoffice work with financial instruments 1993-1994 Computer & Audio-Technical Systems AB Programming, sommer job Education/Courses: Stockholm School of Economics, Master of Science diploma, KTH, Computer Science undergraduate studies Languages Swedish, English, also some German and French Born 1973, Swedish citizen I also have a project-based CS which is several pages long but the above is about what I was aiming for in the beginning when I was looking for a job, now I have employment as an IT consultant in central Stockholm and I want to make my resume concise and also know what Google meant with their answer (It was a Swedish Google employee that via linkedin recruited from my Stockholm School of Economics groups since that is a small elite economics school where I took my M.Sc. and KTH is one of the largest universities in northern Europe so I sent her a link with my CV and she said she could promote me internally if I added "measurable experience" and I've been thinking for weeks what that may mean?

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• Ruby or Python?

  - by Bobby Tables

  Hi all, This question is extremely subjective and open-ended. It might even sound like something I should just research for myself and make my own decision. But I'd like to put it out there and get some thoughts from others. Long story short - I burned out with the rat race and am on a self-funded sabbatical this year. Much of it is to take a break from the corporate grind and travel around, but I also want to play around with new technologies and do some self-learning projects, to stay up to speed on programming, and well - I just love tinkering with programming, when there's no pressure! Here's the thing: I am a lifetime C/C++/Java programmer. I'm a bit of a squiggly bracket snob since I've been working with this family of languages for my entire programming career. So I'd like to learn a language which isn't so closely syntactically related to this group. What I'm basically looking for is a language which is relatively general purpose, fun to learn, has some new concepts that are different from C++/Java, and has a good community. A secondary consideration is that it has good web development frameworks. A tertiary consideration is that it's not totally academic (read: there are real world jobs out there using it). I've narrowed it down to Ruby or Python. My impression of Ruby is that it is extremely web oriented - that the only real application of it is as a server side scripting language for doing web stuff (mainly Ruby on Rails). For Python I'm not so sure. TL;DR and to put it as succinctly as possible: which of these would be better for a C++/Java guy to learn to get some new perspectives on programming? And which is more open and general purpose and applicable to a wider set of applications? I'm leaning towards Ruby at the moment, but I worry to an extent that it looks like it's used as nothing but a server side web language.

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• Moving from windows to linux

  - by rincewind

  I need to reconcile these 2 facts: I don't feel comfortable working on Linux; I need to develop software for Linux. Some background: I have a 10+ years of programming experience on Windows (almost exclusively C/C++, but some .NET as well), I was a user of FreeBSD at home for about 3 years or so (then had to go back to Windows), and I've never had much luck with Linux. And now I have to develop software for Linux. I need a plan. On Windows, you can get away with just knowing a programming language, an API you're coding against, your IDE (VisualStudio) and some very basic tools for troubleshooting (Depends, ProcessExplorer, DebugView, WinDbg). Everything else comes naturally. On Linux, it's a very different story. How the hell would I know what DLL (sorry, Shared Object) would load, if I link to it from Firefox plugin? What's the Linux equivalent of inserting __asm int 3/DebugBreak() in the source and running the program, and then letting the OS call a debugger? Why the hell release builds use something, called appLoader, while debug builds work somehow different? Worst of all: how to provision Linux development environment? So, taking into account that hatred is usually associated with not knowing enough, what would you recommend? I'm ok with Emacs and GCC. I need to educate myself as a Linux admin/user, and I need to learn proper troubleshooting tools (strace is cool, btw), equivalents to the ones I mentioned above. Do I need to do Linux From Scratch? Or do I need to just read some books (I've read "UNIX programming enviornment" by Kernighan and "Advanced Programming..." by Stevens, but I need to learn something more practical)? Or do I need to have some Linux distro on my home computer?

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• The road to become a programmer [closed]

  - by user68991

  I'm looking for a 'career' change, I don't actually have a career at the moment since I haven't been able to find a job since I graduated with a degree in Materials Engineering. One of my loves has always been computers and programming, though I have never studied it seriously. When I was 11 I wrote a very basic graphical 'game' using notepad and HTML, where I drew each possible position of the main character on the different 'maze' level in MSPaint, using pictures of arrows as links to a new page with the character in a new position, and various other buttons would pop up 'search box', 'press button' etc. At the time I thought this was an amazing achievement of my programming skills. I've used a little bit of FORTRAN 90 whilst I was at university, which rekindled my interest in programming. When I was a kid I mainly used C and HTML, but only very basically as my 'game' suggests. I want to learn a new programming language, I'm not entirely sure where I want to go with it, but the number one contender at the moment is android apps. I'm looking at learning Java, but I've read that it's a difficult place to begin with; so I've also looked at learning Visual Basic, which I believe is also object oriented(?) but a little easier to understand? (not that I know what an object is anyway). Any information people could give me regarding which language to learn, and if there are any good online tutorial for that language I'd really appreciate it. Some of the tutorials I've used so far are full or jargon I can't understand. Also, I'm not afraid of maths having got an engineering degree. Thanks in advance for any help/advice. James

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