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• Java multiline string

  - by skiphoppy

  Coming from Perl, I sure am missing the "here-document" means of creating a multi-line string in source code: $string = <<"EOF" # create a three line string text text text EOF In Java I have to have cumbersome quotes and plus signs on every line as I concatenate my multiline string from scratch. What are some better alternatives? Define my string in a properties file? Edit: Two answers say StringBuilder.append() is preferable to the plus notation. Could anyone elaborate as to why they think so? It doesn't look more preferable to me at all. I'm looking for away around the fact that multiline strings are not a first-class language construct, which means I definitely don't want to replace a first-class language construct (string concatenation with plus) with method calls. Edit: To clarify my question further, I'm not concerned about performance at all. I'm concerned about maintainability and design issues.

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• Sending BLOBs in a JSON service,... how?

  - by Marten Sytema

  Hello I have a webservice (ie. servlet) implemented in Java. It gets some data from a MySQL table, with one column being of type BLOB (an image), and some other columns are just plain text. Normally I would store the file outside the database with a pointer to it in the database, but due to circumstance I now have to use this BLOB column... What is the proper way to send this? How to encode the image in a JSONObject, and how to parse (and RENDER!) it on the otherside ? I want to use JSONP, to avoid having to proxy it through the consumer's webserver. So that the consumer can just put in a tag pointing to the webservice, calling a callback. Any thoughts how to handle images in this situation? Also thoughts on performance etc. are interesting!

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• How to save objects using Multi-Threading in Core Data?

  - by Konstantin

  I'm getting some data from the web service and saving it in the core data. This workflow looks like this: get xml feed go over every item in that feed, create a new ManagedObject for every feed item download some big binary data for every item and save it into ManagedObject call [managedObjectContext save:] Now, the problem is of course the performance - everything runs on the main thread. I'd like to re-factor as much as possible to another thread, but I'm not sure where I should start. Is it OK to put everything (1-4) to the separate thread?

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• Avoiding Nested Queries

  - by Midhat

  How Important is it to avoid nested queries. I have always learnt to avoid them like a plague. But they are the most natural thing to me. When I am designing a query, the first thing I write is a nested query. Then I convert it to joins, which sometimes takes a lot of time to get right. And rarely gives a big performance improvement (sometimes it does) So are they really so bad. Is there a way to use nested queries without temp tables and filesort

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• PyPy -- How can it possibly beat CPython?

  - by Vulcan Eager

  From the Google Open Source Blog: PyPy is a reimplementation of Python in Python, using advanced techniques to try to attain better performance than CPython. Many years of hard work have finally paid off. Our speed results often beat CPython, ranging from being slightly slower, to speedups of up to 2x on real application code, to speedups of up to 10x on small benchmarks. How is this possible? Which Python implementation was used to implement PyPy? CPython? And what are the chances of a PyPyPy or PyPyPyPy beating their score? (On a related note... why would anyone try something like this?)

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• Taking Responsibilites too early - danger or boon?

  - by narresh

  Just I am only six months experienced guy in software industry.Due to recession season,a large volume of employees from our company are asked to leave.This impact affects the new inexperienced guys. The problem is We have to interact with the client directly to gather the requirement We have to design all HLD and LLD ,use cases and DB Diagrams ,that should staisfy the customers who keeping the high software insdutry standards In this do or die situation (Client gives us narrow dead line),we spend most of time with interacting client (only less time is available for development and testing,even sit out for 24 X 7 won't help us to finish our task) If task will not be finished with in the expected time frame ,that will trigger poor performance ration to our profile There are two important questions flashing in our mind : (1) Quit the job and do other business (2) Face the challenge : (if the option is to face the challenge ,What are all the tools should we follow to automate requirement gathering,testing,DB diagram,Code review and the rest.(We are working on ASP.NET 3.5 with SQL Server 2005).

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• Separation of static and dynamic content in Java EE applications

  - by Dan

  We work with IBM products and we typically use IBM Http Servers (read Apache) as a reverse proxy for our application servers. For performance reasons we serve static content (.gif, .jpg, .css, .html etc.) from our http servers, to ease the burden a bit from the application server. So far, we have to distribute files to http server and configure it manually (writing custom scripts at best.) The problem is the effort needed to keep everything in synch, especially when you need to update the app. Does any Java EE product support this “out of the box”? Is there a way to have application server do this automatically, like in cluster configuration for example, where master node is in charge of distributing the application to other nodes and for keeping everything in synch.

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• Why do Java/C# edge out C++ as the recommended language to learn OOP on S.O?

  - by viksit

  I noticed after reading the answers/discussion to this question (What is the best language to learn OOP on?) - that more and more people are recommending C# or Java over C++ to learn OOP on. A simple term search on that answer page results in 10 hits for C++, 21 for C# and 27 for Java. Now, I understand that these 2 languages fix a lot of quirks and issues with C++, and looked up these resources that relate mostly to performance, JVM vs native implementation, systems focus vs applications, manual memory management vs automated et al. My question is - are there any fundamental differences in the OO capabilities of Java/C# vs C++? Or are the former recommended purely due to their generic ease of use/improvements over the latter? Thanks. PS, I'm aware of Java interface inheritance vs C++ multiple inheritance as a difference. I would consider that an implementational one rather than functional.

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• how to work with javascript typed arrays without using for

  - by ramesh babu

  var sendBuffer = new ArrayBuffer(4096); var dv = new DataView(sendBuffer); dv.setInt32(0, 1234); var service = svcName; for (var i = 0; i < service.length; i++) { dv.setUint8(i + 4, service.charCodeAt(i)); } ws.send(sendBuffer); how to workout this wihout using for loop. for loop decreasing performance while works with huge amount of data.

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• vector<vector<largeObject>> vs. vector<vector<largeObject>*> in c++

  - by Leif Andersen

  Obviously it will vary depending on the compiler you use, but I'm curious as to the performance issues when doing vector<vector<largeObject>> vs. vector<vector<largeObject>*>, especially in c++. In specific: let's say that you have the outer vector full, and you want to start inserting elements into first inner vector. How will that be stored in memory if the outer vector is just storing pointers, as apposed to storing the whole inner vector. Will the whole outer vector have to be moved to gain more space, or will the inner vector be moved (assuming that space wasn't pre-allocated), causing problems with the outer vector? Thank you

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• assistance with classifying tests

  - by amateur

  I have a .net c# library that I have created that I am currently creating some unit tests for. I am at present writing unit tests for a cache provider class that I have created. Being new to writing unit tests I have 2 questions These being: My cache provider class is the abstraction layer to my distributed cache - AppFabric. So to test aspects of my cache provider class such as adding to appfabric cache, removing from cache etc involves communicating with appfabric. Therefore the tests to test for such, are they still categorised as unit tests or integration tests? The above methods I am testing due to interacting with appfabric, I would like to time such methods. If they take longer than a specified benchmark, the tests have failed. Again I ask the question, can this performance benchmark test be classifed as a unit test? The way I have my tests set up I want to include all unit tests together, integration tests together etc, therefore I ask these questions that I would appreciate input on.

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• XCP Project Kronos syslog error: "irq ... : nobody cared" on Dom0 host

  - by Vlad Fedin

  One of our production clusters driven by XCP suddenly went uresponsive. After restart and some investigation we found such logs in dom0 machine syslog: Oct 26 20:32:03 hetzner-2-mrx kernel: [1797931.659040] irq 339: nobody cared (try booting with the "irqpoll" option) Oct 26 20:32:03 hetzner-2-mrx kernel: [1797931.659058] Pid: 0, comm: swapper/3 Tainted: G C O 3.2.0-24-generic #37-Ubuntu Oct 26 20:32:03 hetzner-2-mrx kernel: [1797931.659060] Call Trace: Oct 26 20:32:03 hetzner-2-mrx kernel: [1797931.659062] <IRQ> [<ffffffff810db37d>] __report_bad_irq+0x3d/0xe0 Oct 26 20:32:03 hetzner-2-mrx kernel: [1797931.659071] [<ffffffff810db605>] note_interrupt+0x135/0x190 Oct 26 20:32:03 hetzner-2-mrx kernel: [1797931.659074] [<ffffffff810d8e69>] handle_irq_event_percpu+0xa9/0x220 Oct 26 20:32:03 hetzner-2-mrx kernel: [1797931.659078] [<ffffffff8130ff3b>] ? radix_tree_lookup+0xb/0x10 Oct 26 20:32:03 hetzner-2-mrx kernel: [1797931.659081] [<ffffffff810d9031>] handle_irq_event+0x51/0x80 Oct 26 20:32:03 hetzner-2-mrx kernel: [1797931.659084] [<ffffffff810dc187>] handle_edge_irq+0x87/0x140 Oct 26 20:32:03 hetzner-2-mrx kernel: [1797931.659089] [<ffffffff813a8829>] __xen_evtchn_do_upcall+0x199/0x250 Oct 26 20:32:03 hetzner-2-mrx kernel: [1797931.659092] [<ffffffff813aa96f>] xen_evtchn_do_upcall+0x2f/0x50 Oct 26 20:32:03 hetzner-2-mrx kernel: [1797931.659096] [<ffffffff81666d3e>] xen_do_hypervisor_callback+0x1e/0x30 Oct 26 20:32:03 hetzner-2-mrx kernel: [1797931.659097] <EOI> [<ffffffff810013aa>] ? hypercall_page+0x3aa/0x1000 Oct 26 20:32:03 hetzner-2-mrx kernel: [1797931.659104] [<ffffffff810013aa>] ? hypercall_page+0x3aa/0x1000 Oct 26 20:32:03 hetzner-2-mrx kernel: [1797931.659107] [<ffffffff8100a1d0>] ? xen_safe_halt+0x10/0x20 Oct 26 20:32:03 hetzner-2-mrx kernel: [1797931.659110] [<fff IRQ 339 in cat /proc/interrupts: 339: ... xen-pirq-msi-x eth0 where eth0 is hardware NIC. While host machine seems to hang, guest machines continue to work, so our tiny internal monitoring on one of the virtual hosts logged something like that: [2012-10-26 20:31:51] [OK......] 200 OK : 113159149 ns [2012-10-26 20:32:40] [DISASTER] 500 Can't connect to [hostname]:80 (No route to host) : 47763284432 ns ... [2012-10-26 20:34:40] [DISASTER] 500 Can't connect to [hostname]:80 (No route to host) : 46894835070 ns [2012-10-26 20:34:57] [DISASTER] 500 Can't connect to [hostname]:80 (Bad hostname) : 16821741955 ns ... [2012-10-26 20:38:18] [DISASTER] 500 Can't connect to [hostname]:80 (Bad hostname) : 20103298289 ns [2012-10-26 20:38:37] [DISASTER] 500 Can't connect to [hostname]:80 (Bad hostname) : 17895754943 ns Host and guest OS: Ubuntu 12.04 LTS, 05:00.0 Ethernet controller: Intel Corporation 82574L Gigabit Network Connection Subsystem: ASUSTeK Computer Inc. Device 8369 Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx+ Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx+ Latency: 0, Cache Line Size: 64 bytes Interrupt: pin A routed to IRQ 17 Region 0: Memory at fe500000 (32-bit, non-prefetchable) [size=128K] Region 2: I/O ports at e000 [size=32] Region 3: Memory at fe520000 (32-bit, non-prefetchable) [size=16K] Capabilities: <access denied> Kernel driver in use: e1000e Kernel modules: e1000e Any hints how to debug this?

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• MSSQL choosing row (from group) with max value

  - by sriehl

  I have a large database and am putting together a report of the data. I have aggregated and summed the data from many tables to get two tables that look like the following. id | code | value id | code | value 13 | AA | 0.5 13 | AC | 2.0 13 | AB | 1.0 14 | AB | 1.5 14 | AA | 2.0 13 | AA | 0.5 15 | AB | 0.5 15 | AB | 3.0 15 | AD | 1.5 15 | AA | 1.0 I need to get a list of id's, with the code (sumed from both tables) with the largest value. 13 | AC 14 | AA 15 | AB There are 4-6 thousand records and it is not possible to change the original tables. I'm not too worried about performance as I only need to run it a few times a year.

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• What messaging technologies in windows-ce for guaranteed msg delivery?

  - by Aidanapword

  We are building a windows-ce (6.0R3) based device that requires guaranteed and audit-ready message delivery (including store & forward) up to and down from the cloud. I have been looking for choices beyond: MSMQ a proprietary solution (what our prototype device is using) AMQP (I have not found any RabbitMQ clients for CE, by example) ... are there any others? We will be transporting sensitive data (who isn't?!?!) over a public network, and large scale options are required. Anything running on an embedded device will be performance sensitive too.

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• MySQL locking problem

  - by teehoo

  I have a simple setup of a set of writers and a set of readers working with a MySQL ISAM table. The writers are only inserting rows while the readers are only checking for new rows. OK, so I know that I don't need a lock in this situation, since I'm not modifying existing rows. However my Writers are accessing one more table that does need a lock. I piece of information seems irrelevant except for the following limitation stated in the MySQL documentation: A session that requires locks must acquire all the locks that it needs in a single LOCK TABLES statement. While the locks thus obtained are held, the session can access only the locked tables. For example, in the following sequence of statements, an error occurs for the attempt to access t2 because it was not locked in the LOCK TABLES statement: So to access the table I want to insert rows into, I NEED to lock it, which is causing me performance problems. Any suggestions of how to get around this?

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• MySQL triggers cannot update rows in same table the trigger is assigned to. Suggested workaround?

  - by Cory House

  MySQL doesn't currently support updating rows in the same table the trigger is assigned to since the call could become recursive. Does anyone have suggestions on a good workaround/alternative? Right now my plan is to call a stored procedure that performs the logic I really wanted in a trigger, but I'd love to hear how others have gotten around this limitation. Edit: A little more background as requested. I have a table that stores product attribute assignments. When a new parent product record is inserted, I'd like the trigger to perform a corresponding insert in the same table for each child record. This denormalization is necessary for performance. MySQL doesn't support this and throws: Can't update table 'mytable' in stored function/trigger because it is already used by statement which invoked this stored function/trigger. A long discussion on the issue on the MySQL forums basically lead to: Use a stored proc, which is what I went with for now. Thanks in advance!

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• How can I dynamically inject code into event handlers in Delphi?

  - by mjustin

  For debugging / performance tests I would like to dynamically add logging code to all event handlers of components of a given type. For example, for all Dataset components located ona TDatamodule, I would like to add some code for the BeforeOpen and the AfterOpen event to store the start and end time and send a line to a logger with the elapsed time in the AfterOpen event. I would prefer to do this dynamically (no component subclassing), so that I can add this to all existing datamodules and forms with minimal effort only when needed. Iterating all components and filtering by their type is easy, but for the components which already have event handlers assigned, I need a way to store the existing event handlers, and assign a new modified event handler which first does the logging and then will invoke the original code which was already present. Is there a design pattern which can be applied, or even some example code which shows how to implement this in Delphi?

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• What is the best Java numerical method package?

  - by Bob Cross

  I am looking for a Java-based numerical method package that provides functionality including: Solving systems of equations using different numerical analysis algorithms. Matrix methods (e.g., inversion). Spline approximations. Probability distributions and statistical methods. In this case, "best" is defined as a package with a mature and usable API, solid performance and numerical accuracy. Edit: derick van brought up a good point in that cost is a factor. I am heavily biased in favor of free packages but others may have a different emphasis.

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• Semantic stuff (RDF, OWL) on mobile phones - is it possible?

  - by Brian Schimmel

  I'm thinking about using semantic (web) technogies like RDF and OWL in an application on mobile devices. Currently I'm targeting android, but I'd also be interested in the possibilities on the iPhone and on J2ME. I would like to use a lib instead of implementing everything from scratch. I know that there are some libraries and frameworks like Jena, Redland, Protégé but they don't state on which platforms they are known to work. Having a dynamic object model and parsing from and to XML are must-haves for me. I'd also like to use reasoning, but I've been told it was rather computing-intensive, so that's only a nice-to-have. For all platforms mentioned, the question can be interpreted as Is it possible in theory (especially for J2ME I'm not sure) Are there libs that are known to work on those platforms? Is the performance on a mobile platform good enough for real world usage?

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• Measuring daemon CPU utilization over a portion of it's wall clock run time

  - by WhirlWind

  I am dealing with a network-related daemon: it takes data in, processes it, and spits it out. I would like to increase the performance of this daemon by profiling it and reducing it's CPU utilization. I can do this easily on Linux with gprof. However, I would also like to use something like "time" to measure it's total CPU utilization over a period of time. If possible, I would like to time it over a period that is less than its total run time: thus, I would like to start the daemon, wait awhile, generate CPU statistics, stop generating them, then stop the daemon at some later time. The "time" command would work well for me, but it seems to require that I start and stop the daemon as a child of time. Is there a way to measure CPU utilization for only a portion of the daemon's wall clock time?

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• Getting latest Subsonic builds

  - by Alex Yakunin

  I need the latest Subsonic build or build it by my own. Subsonic project web site shows the latest available version is Subsonic v3.0.0.3 released at July 15, 2009. Questions: Are there any later builds - e.g. maintained by community members? If so, how can I get the latest one? In worst case I'm ready to get the latest source code and try to build it by my own. Are there any instructions for this? Please note, that I'm not interested in almost 1 year old builds - I need a build based on the latest code for tests (LINQ, performance), ideally - compiled for .NET 4.0.

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• Good reasons why to not use XIB files?

  - by mystify

  Are there any good reasons why I should not use XIB / NIB files with an highly customized UI and extensive animations and super low memory footprint needs? As a beginner I started with XIB. Then I figured out I couldn't do just about everything in them. It started to get really hard to customize things the way I wanted them to be. So at the end, I threw all my XIBs away and did it all programmatically. So when someone asks me if XIB is good, I generally say: Yeah, if you want to make crappy boring interfaces and don't care too much about performance, go ahead. But what else could be a reason not to use XIB? Am I the only iPhone developer who prefers doing everything programmatically for this reasons?

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• Reading files from an embedded ZIP archive

  - by aix

  I have a ZIP archive that's embedded inside a larger file. I know the archive's starting offset within the larger file and its length. Are there any Java libraries that would enable me to directly read the files contained within the archive? I am thinking along the lines of ZipFile.getInputStream(). Unfortunately, ZipFile doesn't work for this use case since its constructors require a standalone ZIP file. For performance reasons, I cannot copy the ZIP achive into a separate file before opening it. edit: Just to be clear, I do have random access to the file.

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• Asp .Net MVC Viewmodel should be class or struct?

  - by Jonas Everest

  Hey guys, I have just been thinking about the concept of view model object we create in asp.net MVC. Our purpose is to instantiate it and pass it from controller to view and view read it and display the data. Those view model are usually instantiated through constructor. We won't need to initialize the members, we may not need to redefine/override parameterless constructor and we don't need inheritance feature there. So, why don't we use struct type for our view model instead of class. It will enhance the performance.

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• Is is better to store serialized data or raw html in mysql?

  - by Yegor

  I de-normalized my database, since the application was crawling otherwise, and Im storing a list of categories for each item in the DB as a raw html version, and simply echoing it out in my design. Each category is actually a link, which is include a tag. Naturally, this is abit of a pain, especially if I want to change the look of how the category links are displayed, since I gotta update all the old cached entries. What if I were to store this data as a serialized array instead, and simply unserialize it, and then apply formatting to it in php. Would there be a significant performance decrease over simply echoing out the raw html?

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