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• Why calling Process.killProcess(Process.myPid()) is a bad idea?

  - by Tal Kanel

  I've read some posts saying using this method is "not good", shouldn't been use, it's not the right way to "close" the application and it's not how android works... I understand and accept the fact that Android OS knows better then me when it's the right time to terminate the process, but I didn't heard yet a good explanation why it's wrong using the killProcess() method?. after all - it's part of the android API... what I do know is that calling this method while other threads doing in potential an important work (operations on files, writing to DB, HTTP requests, running services..) can be terminated in the middle, and it's clearly not good. also I know I can benefit from the fact that "re-open" the application will be faster, cause the system maybe still "holds" in memory state from last time been used, and killProcess() prevents that. beside this reason, in assumption I don't have such operations, and I don't care my application will load from scratch each run, there are other reasons why not using the killProcess() method? I know about finish() method to close an Activity, so don't write me about that please.. finish() is only for Activity. not to all application, and I think I know exactly why and when to use it... and another thing - I'm developing also games with the Unity3D framework, and exporting the project to android. when I decompiled the generated apk, I was very suprised to find out that the java source code created from unity - implementing Unity's - Application.quit() method, with Process.killProcess(Process.myPid()). Application.quit() is suppose to be the right way to close game according to Unity3d guides (is it really?? maybe I'm wrong, and missed something), so how it happens that the Unity's framework developers which doing a very good work as it seems implemented this in native android to killProcess()? anyway - I wish to have a "list of reasons" why not using the killProcess() method, so please write down your answer - if you have something interesting to say about that. TIA

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• DataGridView not showing Columns and Rows during runtime.

  - by Ankush

  I have created a windows form with two groupbox (GB1 and GB2). GB2 is set to BringToFront and Hide. GB2 have Datagridview dgv docked in panel. GB1 has a button which invoke GB2 groupbox and fill 5 datagridview rows to perform 5 operations. But is not visible during runtime. It display all columns and rows after all 5 operations were done. I want to show the user each row. I have tried below code but it did not work. GB1.Visible = false; GB1.Hide(); panel.BringToFront(); GB2.BringToFront(); GB2.Visible = true; panel.Select(); panel.Focus(); GB2.Select(); GB2.Show(); dgv.Refresh(); dgv.Select(); dgv.Focus(); Please help me.

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• Audio stream mangement in Linux

  - by User1

  I have a very complicated audio setup for a project. Here's what we have: 3 applications playing sound 2 applications recording sound 2 sound cards I really don't really have the code to any of these applications. All I want to do is monitor and control the audio streams. Here are a few examples of operations I'd like to do while the applications are running: Mute one of the incoming audio streams. Have one of the incoming audio streams do a "solo" (be the only stream that can "talk"). Get a graph (about 30 seconds worth) of the audio that each stream produced. Send one of the audio streams to soundcard #1, but all three audio streams to soundcard #2. I would likely switch audio streams every 2 minutes or so with one of the operations listed above. A GUI would be preferred. I started looking at the sound systems in Linux and it gets extremely complex and I feel like there have been many new advances in the past few years. I see jack, pulseaudio, artsd, and several other packages. They all have some promise but where should I start? Is there something someone already built that can help?

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• std::binary_function - no match for call?

  - by Venkat Shiva

  Hi, this is my code: #include <iostream> #include <functional> using namespace std; int main() { binary_function<double, double, double> operations[] = { plus<double>(), minus<double>(), multiplies<double>(), divides<double>() }; double a, b; int choice; cout << "Enter two numbers" << endl; cin >> a >> b; cout << "Enter opcode: 0-Add 1-Subtract 2-Multiply 3-Divide" << endl; cin >> choice; cout << operations[choice](a, b) << endl; } and the error I am getting is: Calcy.cpp: In function ‘int main()’: Calcy.cpp:17: error: no match for call to ‘(std::binary_function<double, double, double>) (double&, double&)’ Can anyone explain why I am getting this error and how to get rid of it?

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• WF performance with new 20,000 persisted workflow instances each month

  - by Nikola Stjelja

  Windows Workflow Foundation has a problem that is slow when doing WF instances persistace. I'm planning to do a project whose bussiness layer will be based on WF exposed WCF services. The project will have 20,000 new workflow instances created each month, each instance could take up to 2 months to finish. What I was lead to belive that given WF slownes when doing peristance my given problem would be unattainable given performance reasons. I have the following questions: Is this true? Will my performance be crap with that load(given WF persitance speed limitations) How can I solve the problem? We currently have two possible solutions: 1. Each new buisiness process request(e.g. Give me a new drivers license) will be a new WF instance, and the number of persistance operations will be limited by forwarding all status request operations to saved state values in a separate database. 2. Have only a small amount of Workflow Instances up at any give time, without any persistance ofso ever(only in case of system crashes etc.), by breaking each workflow stap in to a separate worklof and that workflow handling each business process request instance in the system that is at that current step(e.g. I'm submitting my driver license reques form, which is step one... we have 100 cases of that, and my step one workflow will handle every case simultaneusly). I'm very insterested in solution for that problem. If you want to discuss that problem pleas be free to mail me at [email protected]

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• CLR Stored Procedures

  - by Paul Hatcherian

  In an ASP.NET application, I have a small number of fairly complex, frequently used operations to execute against a database. In these operations, one or more of several tables needs updates or inserts based a logical evaluation of both input parameters and values of certain tables. I've maintained a separation of logic and data access, so the operation currently looks like this: Request received from client Business layer invokes data layer to retrieve data from database Business layer processes result and determines which operation to execute Business layer invokes appropriate data operation Response sent to client As you can see, the client is kept waiting while two separate requests are made to the database. In searching for a solution to this, I've found CLR Stored Procedures, but I'm not sure if I have the right idea about what they are useful for. I have written a replacement for the code above which especially places steps 2-4 in a CLR SP. My understanding is that the SP will be executed locally by SQL Server and result in only one call being made to the server. My initial benchmark tests show this is actually orders of magnitude slower than my original code, but I attribute that recompilation of the code I have not worked out yet and/or some flaw in my environment. My question is basically, is this the intended use of CLR SPs or am I missing something? I realize this is a bit of a compromise structurally, so if there's a better way to do it I'd love to hear it.

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• How to implement Excel Solver functionality in C#?

  - by Vic

  Hi, I have an application in C#, I need to do some optimization calculations, like Excel Solver Add-in does, one option is certainly to write my own solver implementation, but I'm kind of short of time, so I'm looking into libraries that already exist that can help me with this. I've been trying the Microsoft Solver Foundation, which seems pretty neat and cool, the problem is that it doesn't seem to work with the kind of calculations that I need to do. At the end of this question I'm adding the information about the calculations I need to perform and optimize. So basically my question is if any of you know of any other library that I can use for this purpose, or any tutorial that can help to do my own solver, or any idea that gives me a lead to solve this issue. Thanks. Additional Info: This is the data I need to calculate: I have 7 variables, lets call them var1, var2,...,var7 The constraints for these variables are: All of them need to be 0 <= varn <= 0.5 (where n is the number of the variable) The sum of all the variables should be equal to 1 The objective is to maximize the target formula, which in Excel looks like this: (MMULT(TRANSPOSE(L26:L32),M14:M20)) / (SQRT(MMULT(MMULT(TRANSPOSE(L26:L32),M4:S10),L26:L32))) The range that you see in this formula, L26:L32, is actually the range with the variables from above, var1, var2,..., varn. M14:M20 and M4:S10 are ranges with data that I get from different sources, there are more likely decimal values. As I said before, I was using Microsoft Solver Foundation, I modeled pretty much everything with it, I created functions that handle the operations of the target formula, but when I tried to solve the model it always fail, I think it is because of the complexity of the operations. In any case, I just wanted to show these data so you can have an idea about the kind of calculations that I need to implement.

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• Stream Reuse in C#

  - by MikeD

  I've been playing around with what I thought was a simple idea. I want to be able to read in a file from somewhere (website, filesystem, ftp), perform some operations on it (compress, encrypt, etc.) and then save it somewhere (somewhere may be a filesystem, ftp, or whatever). It's a basic pipeline design. What I would like to do is to read in the file and put it onto a MemoryStream, then perform the operations on the data in the MemoryStream, and then save that data in the MemoryStream somewhere. I was thinking I could use the same Stream to do this but run into a couple of problems: Everytime I use a StreamWriter or StreamReader I need to close it and that closes the stream so that I cannot use it anymore. That seems like there must be some way to get around that. Some of these files may be big and so I may run out of memory if I try to read the whole thing in at once. I was hoping to be able to spin up each of the steps as separate threads and have the compression step begin as soon as there is data on the stream, and then as soon as the compression has some compressed data available on the stream I could start saving it (for example). Is anything like this easily possible with the C# Streams? ANyone have thoughts as to how to accomplish this best? Thanks, Mike

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• std::vector iterator or index access speed question

  - by Simone Margaritelli

  Just a stupid question . I have a std::vector<SomeClass *> v; in my code and i need to access its elements very often in the program, looping them forward and backward . Which is the fastest access type between those two ? Iterator access std::vector<SomeClass *> v; std::vector<SomeClass *>::iterator i; std::vector<SomeClass *>::reverse_iterator j; // i loops forward, j loops backward for( i = v.begin(), j = v.rbegin(); i != v.end() && j != v.rend(); i++, j++ ){ // some operations on v items } Subscript access (by index) std::vector<SomeClass *> v; unsigned int i, j, size = v.size(); // i loops forward, j loops backward for( i = 0, j = size - 1; i < size && j >= 0; i++, j-- ){ // some operations on v items } And, does const_iterator offer a faster way to access vector elements in case i do not have to modify them? Thank you in advantage.

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• Managing lots of callback recursion in Nodejs

  - by Maciek

  In Nodejs, there are virtually no blocking I/O operations. This means that almost all nodejs IO code involves many callbacks. This applies to reading and writing to/from databases, files, processes, etc. A typical example of this is the following: var useFile = function(filename,callback){ posix.stat(filename).addCallback(function (stats) { posix.open(filename, process.O_RDONLY, 0666).addCallback(function (fd) { posix.read(fd, stats.size, 0).addCallback(function(contents){ callback(contents); }); }); }); }; ... useFile("test.data",function(data){ // use data.. }); I am anticipating writing code that will make many IO operations, so I expect to be writing many callbacks. I'm quite comfortable with using callbacks, but I'm worried about all the recursion. Am I in danger of running into too much recursion and blowing through a stack somewhere? If I make thousands of individual writes to my key-value store with thousands of callbacks, will my program eventually crash? Am I misunderstanding or underestimating the impact? If not, is there a way to get around this while still using Nodejs' callback coding style?

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• Are there some cases where Python threads can safely manipulate shared state?

  - by erikg

  Some discussion in another question has encouraged me to to better understand cases where locking is required in multithreaded Python programs. Per this article on threading in Python, I have several solid, testable examples of pitfalls that can occur when multiple threads access shared state. The example race condition provided on this page involves races between threads reading and manipulating a shared variable stored in a dictionary. I think the case for a race here is very obvious, and fortunately is eminently testable. However, I have been unable to evoke a race condition with atomic operations such as list appends or variable increments. This test exhaustively attempts to demonstrate such a race: from threading import Thread, Lock import operator def contains_all_ints(l, n): l.sort() for i in xrange(0, n): if l[i] != i: return False return True def test(ntests): results = [] threads = [] def lockless_append(i): results.append(i) for i in xrange(0, ntests): threads.append(Thread(target=lockless_append, args=(i,))) threads[i].start() for i in xrange(0, ntests): threads[i].join() if len(results) != ntests or not contains_all_ints(results, ntests): return False else: return True for i in range(0,100): if test(100000): print "OK", i else: print "appending to a list without locks *is* unsafe" exit() I have run the test above without failure (100x 100k multithreaded appends). Can anyone get it to fail? Is there another class of object which can be made to misbehave via atomic, incremental, modification by threads? Do these implicitly 'atomic' semantics apply to other operations in Python? Is this directly related to the GIL?

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• priority queue with limited space: looking for a good algorithm

  - by SigTerm

  This is not a homework. I'm using a small "priority queue" (implemented as array at the moment) for storing last N items with smallest value. This is a bit slow - O(N) item insertion time. Current implementation keeps track of largest item in array and discards any items that wouldn't fit into array, but I still would like to reduce number of operations further. looking for a priority queue algorithm that matches following requirements: queue can be implemented as array, which has fixed size and _cannot_ grow. Dynamic memory allocation during any queue operation is strictly forbidden. Anything that doesn't fit into array is discarded, but queue keeps all smallest elements ever encountered. O(log(N)) insertion time (i.e. adding element into queue should take up to O(log(N))). (optional) O(1) access for *largest* item in queue (queue stores *smallest* items, so the largest item will be discarded first and I'll need them to reduce number of operations) Easy to implement/understand. Ideally - something similar to binary search - once you understand it, you remember it forever. Elements need not to be sorted in any way. I just need to keep N smallest value ever encountered. When I'll need them, I'll access all of them at once. So technically it doesn't have to be a queue, I just need N last smallest values to be stored. I initially thought about using binary heaps (they can be easily implemented via arrays), but apparently they don't behave well when array can't grow anymore. Linked lists and arrays will require extra time for moving things around. stl priority queue grows and uses dynamic allocation (I may be wrong about it, though). So, any other ideas?

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• Clear UITextField when standard number pad is pressed

  - by Manu

  Hi all, I'm sorry if I didn't explain my problem well enough in the title. In my application, I'm using a small subview to create a very basic calculator on the top side of the screen (I just have an UITextField to show the operations and two buttons). Instead of using a custom keyboard for it, I want to use the standard iPhone number pad. My problem is that after doing an operation (e.g. adding two numbers) and showing the result, I cannot figure out how to clear the screen when the user enters a new number. So, for example: User enters "6" - Number 6 is shown in UITextField User selects "+" - UITextField is cleared to make room for the next number User enters "10" - Number 10 is shown in UITextField User selects "+" - 16 is shown as the result of the previous operation, and should stay there until another number is pressed (he wants to continue adding more numbers) User enters "5" At this point, if I was using a custom keyboard, I could clear the UITextField as soon as the button "5" is pressed by the user, but I cannot figure out how to do so when using the standard number pad. So, the result I get at the moment is "165". Is there a way to detect when a key is pressed in the standard number pad so that I can clear the UITextField before the new number appears? I thought there may be a NSNotification for that, but I couldn't find it. I'm aware that I could solve my problem if I created a custom keyboard or if I used two separated UITextFields (one for the operations and another one for the total), but I would like to use the standard number pad if it's possible. Thanks very much!

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• Using Qt signals/slots instead of a worker thread

  - by Rob

  I am using Qt and wish to write a class that will perform some network-type operations, similar to FTP/HTTP. The class needs to connect to lots of machines, one after the other but I need the applications UI to stay (relatively) responsive during this process, so the user can cancel the operation, exit the application, etc. My first thought was to use a separate thread for network stuff but the built-in Qt FTP/HTTP (and other) classes apparently avoid using threads and instead rely on signals and slots. So, I'd like to do something similar and was hoping I could do something like this: class Foo : public QObject { Q_OBJECT public: void start(); signals: void next(); private slots: void nextJob(); }; void Foo::start() { ... connect(this, SIGNAL(next()), this, SLOT(nextJob())); emit next(); } void Foo::nextJob() { // Process next 'chunk' if (workLeftToDo) { emit next(); } } void Bar::StartOperation() { Foo* foo = new Foo; foo->start(); } However, this doesn't work and UI freezes until all operations have completed. I was hoping that emitting signals wouldn't actually call the slots immediately but would somehow be queued up by Qt, allowing the main UI to still operate. So what do I need to do in order to make this work? How does Qt achieve this with the multitude of built-in classes that appear to perform lengthy tasks on a single thread?

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• Dynamically created operators

  - by Gero

  I created a program using dev-cpp and wxwidgets which solves a puzzle. The user must fill the operations blocks and the results blocks, and the program will solve it. Im solving it using bruteforce, i generate all non repeated 9 length number combinations using a recursive algorithm. It does it pretty fast. Up to here all is great! But the problem is when my program operates depending the character on the blocks. Its extremely slow (it never gets the answer), because of the chars comparation against +, -, *, etc. Im doing a CASE. Is there some way or some programming language wich allows dinamic creation of operators? So i can define the operator ROW1COL2 to be a +, and the same way to all other operations. I leave a screenshot of the app, so its easier to understand how the puzzle works. http://www.imageshare.web.id/images/9gg5cev8vyokp8rhlot9.png PD: The algorithm works, i tryed it with a trivial puzzle, and solved it in a second.

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• Merging k sorted linked lists - analysis

  - by Kotti

  Hi! I am thinking about different solutions for one problem. Assume we have K sorted linked lists and we are merging them into one. All these lists together have N elements. The well known solution is to use priority queue and pop / push first elements from every lists and I can understand why it takes O(N log K) time. But let's take a look at another approach. Suppose we have some MERGE_LISTS(LIST1, LIST2) procedure, that merges two sorted lists and it would take O(T1 + T2) time, where T1 and T2 stand for LIST1 and LIST2 sizes. What we do now generally means pairing these lists and merging them pair-by-pair (if the number is odd, last list, for example, could be ignored at first steps). This generally means we have to make the following "tree" of merge operations: N1, N2, N3... stand for LIST1, LIST2, LIST3 sizes O(N1 + N2) + O(N3 + N4) + O(N5 + N6) + ... O(N1 + N2 + N3 + N4) + O(N5 + N6 + N7 + N8) + ... O(N1 + N2 + N3 + N4 + .... + NK) It looks obvious that there will be log(K) of these rows, each of them implementing O(N) operations, so time for MERGE(LIST1, LIST2, ... , LISTK) operation would actually equal O(N log K). My friend told me (two days ago) it would take O(K N) time. So, the question is - did I f%ck up somewhere or is he actually wrong about this? And if I am right, why doesn't this 'divide&conquer' approach can't be used instead of priority queue approach?

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• Flex - Increase timeout on a PHP service function call

  - by Travesty3

  I'm using Flash Builder 4 Beta 2. I have it connecting to a PHP service. The way I set this up was using the wizard, so I didn't actually write the code to connect to it. The service looks like this: package services.flash { import mx.rpc.AsyncToken; import com.adobe.fiber.core.model_internal; import mx.rpc.AbstractOperation; import valueObjects.CustomDatatype8; import valueObjects.NewUsageData; import mx.collections.ItemResponder; import mx.rpc.remoting.RemoteObject; import mx.rpc.remoting.Operation; import com.adobe.fiber.services.wrapper.RemoteObjectServiceWrapper; import com.adobe.fiber.valueobjects.AvailablePropertyIterator; import com.adobe.serializers.utility.TypeUtility; [ExcludeClass] internal class _Super_FLASH extends RemoteObjectServiceWrapper { // Constructor public function _Super_FLASH() { // initialize service control _serviceControl = new RemoteObject(); var operations:Object = new Object(); var operation:Operation; operation = new Operation(null, "sendCommand"); operation.resultType = Object; operations["sendCommand"] = operation; ... } } One of the functions that I'm calling fetches users from a MySQL database. There are about 30,000 users right now. The service seems to timeout when fetching more than around 22,000 rows, I get the "Channel Disconnected before an acknowledgement was received" error. If I call the PHP script from a browser, it fetches them all with no problems at all, however. I have tried increasing the timeout in the PHP script (which didn't work), but obviously this isn't the problem since the browser is able to pull them up with no problems. Is there a way to increase the timeout of the PHP service in Flash Builder? I'm a bit of a noob when it comes to Flash, so please be descriptive. Thanks in advance!

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• Need events to execute on timer events, metronome precision.

  - by user295734

  I setup a timer to call an event in my application. The problme is the event execution is being skewed by other windows operations. Ex. openning and window, loading a webpage. I need the event to excute exactly on time, every time. When i first set up the app, used a sound file, like a metronome to listen to the even firing, in a steady state, its firing right on, but as soon do something in the windows environment, the sound fires slower, then sort of sppeds up a bit to catch up. So i added a logging method to the event to ctahc the timer ticks. From that data, it appears that the timer is not being affected by the windows app, but my application event calls are being affected. I figured this out by checking the datetime.now in the event, and if i set it to 250 milliseconds, which is 4 clicks per second. You get data something like below. (sec):(ms) 1:000 1:250 1:500 1:750 2:000 2:250 2:500 2:750 3:000 3:250 3:500 3:750 (lets say i execute some windows event)(time will skew) 4:122 4:388 4:600 4:876 (stop doing what i was doing in windows) (going to shorten the data for simplicit, my list was 30sec long) 5:124 5:268 5:500 5:750 (you would se the time go back the same milliseconds it was at the begining) 6:000 6:250 6:500 6:750 7:000 7:250 7:500 7:750 So i'm thinking the timer continues to fire on the same millisecond every time, but its the event that is being skewed to fire off time by other windows operations. Its not a huge skew, but for what i need to accomplish, its unacceptable. Is there anyhting i can do in .NET, hoping to use XAML/WPF application, thats will correct the skewing of events? thx.

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• Why does autoboxing in Java allow me to have 3 possible values for a boolean?

  - by John

  Reference: http://java.sun.com/j2se/1.5.0/docs/guide/language/autoboxing.html If your program tries to autounbox null, it will throw a NullPointerException. javac will give you a compile-time error if you try to assign null to a boolean. makes sense. assigning null to a Boolean is a-ok though. also makes sense, i guess. but let's think about the fact that you'll get a NPE when trying to autounbox null. what this means is that you can't safely perform boolean operations on Booleans without null-checking or exception handling. same goes for doing math operations on an Integer. for a long time, i was a fan of autoboxing in java1.5+ because I thought it got java closer to be truly object-oriented. but, after running into this problem last night, i gotta say that i think this sucks. the compiler giving me an error when I'm trying to do stuff with an uninitialized primitive is a good thing. I think I may be misunderstanding the point of autoboxing, but at the same time I will never accept that a boolean should be able to have 3 values. can anyone explain this? what am i not getting?

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• How to design a RESTful collection resource?

  - by Suresh Kumar

  I am trying to design a "collection of items" resource. I need to support the following operations: Create the collection Remove the collection Add a single item to the collection Add multiple items to the collection Remove a single item from the collection Remove multiple items from the collection This is as far as I have gone: Create collection: ==> POST /service Host: www.myserver.com Content-Type: application/xml <collection name="items"> <item href="item1"/> <item href="item2"/> <item href="item3"/> </collection> <== 201 Created Location: http://myserver.com/service/items Content-Type: application/xml ... Remove collection: ==> DELETE /service/items <== 200 OK Removing a single item from the collection: ==> DELETE /service/items/item1 <== 200 OK However, I am finding supporting the other operations a bit tricky i.e. what methods can I use to: Add single or multiple items to the collection. (PUT doesn't seem to be right here as per HTTP 1.1 RFC Remove multiple items from the collection in one transaction. (DELETE doesn't seem to right here either)

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• .NET threading solution for long queries

  - by Eddie

  Senerio We have an application that records incidents. An external database needs to be queried when an incident is approved by a supervisor. The queries to this external database are sometimes taking a while to run. This lag is experienced through the browser. Possible Solution I want to use threading to eliminate the simulated hang to the browser. I have used the Thread class before and heard about ThreadPool. But, I just found BackgroundWorker in this post. MSDN states: The BackgroundWorker class allows you to run an operation on a separate, dedicated thread. Time-consuming operations like downloads and database transactions can cause your user interface (UI) to seem as though it has stopped responding while they are running. When you want a responsive UI and you are faced with long delays associated with such operations, the BackgroundWorker class provides a convenient solution. Is BackgroundWorker the way to go when handling long running queries? What happens when 2 or more BackgroundWorker processes are ran simultaneously? Is it handled like a pool?

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• Spring - Transaction Readonly

  - by AAK

  Hello Gurus! Just wanted your expert opinions on declarative transaction management for Spring. Here is my setup - A. DAO Layer is Plain old JDBC using jdbcTemplete (No hibernate etc) B. Service Layer is POJO with declarative trasnactions as follows - save*, readonly=false, rollback for Throwable Things work fine with above setup. However when I say get*, readonly=true I see errors in my log file saying - Database connection cannot be marked as readonly. This happens for all get* methods in Service Layer. Now my questions - A. Do I have to say get* as readonly? All my get* methods are pure read DB operations. I do not wish to run them in any transaction context. How serious is the above error? B. When I remove the get* confiiguration, I do not see the errors, morever all my simple get* operations are performed without transactions. Is this the way to go? C. Why would anyone want to have transactional methods where readonly = true? Is there any practical significance of this configuration? Thank you! As always your resposes are much appreciated!

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• Performance of Java matrix math libraries?

  - by dfrankow

  We are computing something whose runtime is bound by matrix operations. (Some details below if interested.) This experience prompted the following question: Do folk have experience with the performance of Java libraries for matrix math (e.g., multiply, inverse, etc.)? For example: JAMA: http://math.nist.gov/javanumerics/jama/ COLT: http://acs.lbl.gov/~hoschek/colt/ Apache commons math: http://commons.apache.org/math/ I searched and found nothing. Details of our speed comparison: We are using Intel FORTRAN (ifort (IFORT) 10.1 20070913). We have reimplemented it in Java (1.6) using Apache commons math 1.2 matrix ops, and it agrees to all of its digits of accuracy. (We have reasons for wanting it in Java.) (Java doubles, Fortran real*8). Fortran: 6 minutes, Java 33 minutes, same machine. jvisualm profiling shows much time spent in RealMatrixImpl.{getEntry,isValidCoordinate} (which appear to be gone in unreleased Apache commons math 2.0, but 2.0 is no faster). Fortran is using Atlas BLAS routines (dpotrf, etc.). Obviously this could depend on our code in each language, but we believe most of the time is in equivalent matrix operations. In several other computations that do not involve libraries, Java has not been much slower, and sometimes much faster.

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• Perl - Read XML

  - by chinna_82

  XML <?xml version='1.0'?> <employee> <name>Smith</name> <age>43</age> <sex>M</sex> <department role='manager'>Operations</department> </employee> Perl use XML::Simple; use Data::Dumper; $xml = new XML::Simple; foreach my $data1 ($data = $xml->XMLin("test.xml")) { print Dumper($data1); } Above code managed to all the xml value like this. Output $VAR1 = { 'department' => { 'content' => 'Operations', 'role' => 'manager' }, 'name' => 'John Doe', 'sex' => 'M', 'age' => '43' }; How do I do, if I only want to get the role value. For this example I need to get Role = manager. Any advice or reference link is highly appreciated.

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• Hibernate overriding database modifications with detached object state

  - by EugeneP

  I'm gonna go with this design: create an object and keep it alive during all web-app session. And I need to synchronize its state with database state. What I want to achieve is that : IF between my db operations, that is, modifications that I persist to a db someone intentionally spoils table rows, then on next saving to a database all those changes WOULD BE OVERWRITTEN with the object state, that always contains valid data. What Hibernate methods do you recommend me to use to persist the modifications in a database? saveOrUpdate() is a possible solution, but maybe there's anything better? Again, I repeat how it looks. First I create an object without collections. Persist it (save()). Then user provides us with additional data. In a serviceLayer, again, we modify our object in memory (say, populate it with collections) and then, persist it again. So every serviceLayer operation of the next step must simply guarantee that database contains the exact persistent copy of this object that we have in memory. If data in a database differ, it MUST BE OVERRIDDEN with the object (kept in memory) state. What Session operations do you recommend?

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