Search Results

Search found 12083 results on 484 pages for 'general purpose'.

Page 10/484 | < Previous Page | 6 7 8 9 10 11 12 13 14 15 16 17  | Next Page >

• A Method for Reducing Contention and Overhead in Worker Queues for Multithreaded Java Applications

  - by Janice J. Heiss

  A java.net article, rich in practical resources, by IBM India Labs’ Sathiskumar Palaniappan, Kavitha Varadarajan, and Jayashree Viswanathan, explores the challenge of writing code in a way that that effectively makes use of the resources of modern multicore processors and multiprocessor servers.As the article states: “Many server applications, such as Web servers, application servers, database servers, file servers, and mail servers, maintain worker queues and thread pools to handle large numbers of short tasks that arrive from remote sources. In general, a ‘worker queue’ holds all the short tasks that need to be executed, and the threads in the thread pool retrieve the tasks from the worker queue and complete the tasks. Since multiple threads act on the worker queue, adding tasks to and deleting tasks from the worker queue needs to be synchronized, which introduces contention in the worker queue.” The article goes on to explain ways that developers can reduce contention by maintaining one queue per thread. It also demonstrates a work-stealing technique that helps in effectively utilizing the CPU in multicore systems. Read the rest of the article here.

  Read the article

• System Wide Performance Sanity Check Procedures

  - by user702295

  Do you need to boost your overall implementation performance? Do you need a direction to pinpoint possible performance opportunities? Are you looking for a general performance guide? Try MOS note 69565.1.  This paper describes a holistic methodology that defines a systematic approach to resolve complex Application performance problems.  It has been successfully used on many critical accounts.  The 'end-to-end' tuning approach encompasses the client, network and database and has proven far more effective than isolated tuning exercises.  It has been used to define and measure targets to ensure success.  Even though it was checked for relevance on 13-Oct-2008, the procedure is still very valuable. Regards!  

  Read the article

• Performance triage

  - by Dave

  Folks often ask me how to approach a suspected performance issue. My personal strategy is informed by the fact that I work on concurrency issues. (When you have a hammer everything looks like a nail, but I'll try to keep this general). A good starting point is to ask yourself if the observed performance matches your expectations. Expectations might be derived from known system performance limits, prototypes, and other software or environments that are comparable to your particular system-under-test. Some simple comparisons and microbenchmarks can be useful at this stage. It's also useful to write some very simple programs to validate some of the reported or expected system limits. Can that disk controller really tolerate and sustain 500 reads per second? To reduce the number of confounding factors it's better to try to answer that question with a very simple targeted program. And finally, nothing beats having familiarity with the technologies that underlying your particular layer. On the topic of confounding factors, as our technology stacks become deeper and less transparent, we often find our own technology working against us in some unexpected way to choke performance rather than simply running into some fundamental system limit. A good example is the warm-up time needed by just-in-time compilers in Java Virtual Machines. I won't delve too far into that particular hole except to say that it's rare to find good benchmarks and methodology for java code. Another example is power management on x86. Power management is great, but it can take a while for the CPUs to throttle up from low(er) frequencies to full throttle. And while I love "turbo" mode, it makes benchmarking applications with multiple threads a chore as you have to remember to turn it off and then back on otherwise short single-threaded runs may look abnormally fast compared to runs with higher thread counts. In general for performance characterization I disable turbo mode and fix the power governor at "performance" state. Another source of complexity is the scheduler, which I've discussed in prior blog entries. Lets say I have a running application and I want to better understand its behavior and performance. We'll presume it's warmed up, is under load, and is an execution mode representative of what we think the norm would be. It should be in steady-state, if a steady-state mode even exists. On Solaris the very first thing I'll do is take a set of "pstack" samples. Pstack briefly stops the process and walks each of the stacks, reporting symbolic information (if available) for each frame. For Java, pstack has been augmented to understand java frames, and even report inlining. A few pstack samples can provide powerful insight into what's actually going on inside the program. You'll be able to see calling patterns, which threads are blocked on what system calls or synchronization constructs, memory allocation, etc. If your code is CPU-bound then you'll get a good sense where the cycles are being spent. (I should caution that normal C/C++ inlining can diffuse an otherwise "hot" method into other methods. This is a rare instance where pstack sampling might not immediately point to the key problem). At this point you'll need to reconcile what you're seeing with pstack and your mental model of what you think the program should be doing. They're often rather different. And generally if there's a key performance issue, you'll spot it with a moderate number of samples. I'll also use OS-level observability tools to lock for the existence of bottlenecks where threads contend for locks; other situations where threads are blocked; and the distribution of threads over the system. On Solaris some good tools are mpstat and too a lesser degree, vmstat. Try running "mpstat -a 5" in one window while the application program runs concurrently. One key measure is the voluntary context switch rate "vctx" or "csw" which reflects threads descheduling themselves. It's also good to look at the user; system; and idle CPU percentages. This can give a broad but useful understanding if your threads are mostly parked or mostly running. For instance if your program makes heavy use of malloc/free, then it might be the case you're contending on the central malloc lock in the default allocator. In that case you'd see malloc calling lock in the stack traces, observe a high csw/vctx rate as threads block for the malloc lock, and your "usr" time would be less than expected. Solaris dtrace is a wonderful and invaluable performance tool as well, but in a sense you have to frame and articulate a meaningful and specific question to get a useful answer, so I tend not to use it for first-order screening of problems. It's also most effective for OS and software-level performance issues as opposed to HW-level issues. For that reason I recommend mpstat & pstack as my the 1st step in performance triage. If some other OS-level issue is evident then it's good to switch to dtrace to drill more deeply into the problem. Only after I've ruled out OS-level issues do I switch to using hardware performance counters to look for architectural impediments.

  Read the article

• SQLSTATE[HY000]: General error: 5 Out of memory (Needed 4194092 bytes)

  - by Jon Reeks

  Hi I'm receiving the following error on my shared hosting box: SQLSTATE[HY000]: General error: 5 Out of memory (Needed 4194092 bytes) This error is only triggered on a specific page. I guess this indicates that I am reaching the upper limit of the 64MB allocated to me in my current MySQL environment. Does this mean that a single query is going over (returning) 64MB of data? If so, i guess i can just track down and tune that specific query? Or isnt that the correct approach? Thanks Jon

  Read the article

• General ODBC Error in VBA

  - by raam

  Hi am populating the data from MS Access By Using VBA i am using below mentioned code.if i am run the same code in MS 2007 then It run properly but if i am run the same code in MS 2003 it gives the "General ODBC Error" how to solve this problem Any help would be appreciated!! Thanks in advance Sub Button2_Click() Dim varConnection As String Dim varSQL As String Dim cal, cal1, x varConnection = "ODBC; DSN=MS Access Database;DBQ=D:\Box\Generate.mdb;Driver={Driver do Microsoft Access (*.mdb)}" ' varSQL = "SELECT * FROM Empdata" With ActiveSheet.QueryTables.Add(Connection:=varConnection, Destination:=ActiveSheet.Range("C7")) .CommandText = varSQL .Name = "Query-39008" .Refresh BackgroundQuery = False End With End Sub

  Read the article

• Tomcat Exception-Type Ignoring Specific Exception for More General

  - by David Marks

  For one type of exception, IOException, I want to display one page. For all other exceptions I have a default error page. In my web.xml I have things setup like this: java.io.IOException /queryException.jsp java.lang.Exception /error.jsp The problem is the error.jsp is the only page that ever shows, even if an IOException is thrown. The order the tags appear in doesn't matter; if I remove the java.lang.Exception tag though, I can get queryException to show for IOExceptions. What is the solution here? How can I keep a general error page for all exceptions EXCEPT for those with specific pages?

  Read the article

• A general question about inheritence in the .NET framework

  - by Grant

  I have a general question about inheritance in the .NET framework, lets say you have 2 classes, the first is called Parent and the second is called Child. Child inherits from Parent. Parent wants to ensure that each instance of child executes a specific piece of code when it loads irrespective of whether the child has their own onLoad code explicitly specified. From my experience, if i handle onLoad in the parent and not in the child, the parents onLoad code will fire but if its handled in both classes only the child's code will fire. Is this correct? and if so how can i ensure the parents code will always fire for the child...

  Read the article

• General zoom algorithm for drawing program

  - by Steven Sproat

  My GUI toolkit, wxPython provides some methods for implementing a user zoom factor, however the quality isn't too good. I'm looking for ideas on how to create a zooming feature, which I know is complicated. I have a bitmap representing my canvas which is drawn to. This is displayed inside a scrolled window. Problems I forsee: - performance when zoomed in and panning around the canvas - difficulties with "real" coordinates and zoomed in coordinates - image quality not degrading with the zoom Using wxPython's SetUserScale() on its device contexts presents image quality like this - this is with a 1px line, at 30% zoomed in. I'm just wondering the general steps I'll need to take and the challenges I'll encounter. Thanks for any suggestions

  Read the article

• A general declaration for all inherited classes

  - by Soham

  Consider, there is a class called SuperClass from which, ClassA, ClassB, ClassC is derived. From each one of those derived Classes, there are further more two classes are derived each called ChildClassAA and ChildClassAB[AB stands for Bth Child class from the Ath Class.Lets not really pull our hair on this nomenclature]. Now, ideally, I want to declare a general type as a private member of another Class say IndependentClass which can be initialized during run time as either of the objects of type ClassAor ClassB or ClassC and even the derived classes like ClassAA or ClassAB. Is there a possible way to do it?

  Read the article

• Visual Studio 2010 compilation general error c1010070

  - by user1747455

  I wrote a little "hello world" program to test my computer, but when i sompile the program there's an error: ------ Build started: Project: hi, Configuration: Debug Win32 ------ Build started 15/10/2012 22:36:48. InitializeBuildStatus: Touching "Debug\hi.unsuccessfulbuild". Link: hi.vcxproj - D:\MSVS\hi\Debug\hi.exe Manifest: Debug\hi.exe.intermediate.manifest : general error c1010070: Failed to load and parse the manifest. {q~ 0H Build FAILED. Time Elapsed 00:00:02.34 ========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ========== the creepiest thing i think would be that line of "OH"... i wonder if there's any way to solve this...please help. Many thanks. edit: i tried changing the character set into "multi-byte" and turning "embed manifest"(from "manifest tools") off, but it still cant solve the error

  Read the article

• General suggestions for making R code faster? [closed]

  - by gsk3

  Questions come up fairly frequently about how to make R code faster. This is an attempt to provide a general framework for thinking about the problem. Questions of this nature seem to fall into one of a few categories: I have a loop and it's running slowly. I've heard that vectorization can speed things up. How do I vectorize it? I've vectorized and it's still running slowly. What do I do next? I'd like to speed up my code but it's running quickly enough already. What are the principles and specifics which can be used to make R code run faster?

  Read the article

• Windows Azure: General Availability of Web Sites + Mobile Services, New AutoScale + Alerts Support, No Credit Card Needed for MSDN

  - by ScottGu

  This morning we released a major set of updates to Windows Azure.  These updates included: Web Sites: General Availability Release of Windows Azure Web Sites with SLA Mobile Services: General Availability Release of Windows Azure Mobile Services with SLA Auto-Scale: New automatic scaling support for Web Sites, Cloud Services and Virtual Machines Alerts/Notifications: New email alerting support for all Compute Services (Web Sites, Mobile Services, Cloud Services, and Virtual Machines) MSDN: No more credit card requirement for sign-up All of these improvements are now available to use immediately (note: some are still in preview).  Below are more details about them. Web Sites: General Availability Release of Windows Azure Web Sites I’m incredibly excited to announce the General Availability release of Windows Azure Web Sites. The Windows Azure Web Sites service is perfect for hosting a web presence, building customer engagement solutions, and delivering business web apps.  Today’s General Availability release means we are taking off the “preview” tag from the Free and Standard (formerly called reserved) tiers of Windows Azure Web Sites.  This means we are providing: A 99.9% monthly SLA (Service Level Agreement) for the Standard tier Microsoft Support available on a 24x7 basis (with plans that range from developer plans to enterprise Premier support) The Free tier runs in a shared compute environment and supports up to 10 web sites. While the Free tier does not come with an SLA, it works great for rapid development and testing and enables you to quickly spike out ideas at no cost. The Standard tier, which was called “Reserved” during the preview, runs using dedicated per-customer VM instances for great performance, isolation and scalability, and enables you to host up to 500 different Web sites within them.  You can easily scale your Standard instances on-demand using the Windows Azure Management Portal.  You can adjust VM instance sizes from a Small instance size (1 core, 1.75GB of RAM), up to a Medium instance size (2 core, 3.5GB of RAM), or Large instance (4 cores and 7 GB RAM).  You can choose to run between 1 and 10 Standard instances, enabling you to easily scale up your web backend to 40 cores of CPU and 70GB of RAM: Today’s release also includes general availability support for custom domain SSL certificate bindings for web sites running using the Standard tier. Customers will be able to utilize certificates they purchase for their custom domains and use either SNI or IP based SSL encryption. SNI encryption is available for all modern browsers and does not require an IP address.  SSL certificates can be used for individual sites or wild-card mapped across multiple sites (we charge extra for the use of a SSL cert – but the fee is per-cert and not per site which means you pay once for it regardless of how many sites you use it with).  Today’s release also includes the following new features: Auto-Scale support Today’s Windows Azure release adds preview support for Auto-Scaling web sites.  This enables you to setup automatic scale rules based on the activity of your instances – allowing you to automatically scale down (and save money) when they are below a CPU threshold you define, and automatically scale up quickly when traffic increases.  See below for more details. 64-bit and 32-bit mode support You can now choose to run your standard tier instances in either 32-bit or 64-bit mode (previously they only ran in 32-bit mode).  This enables you to address even more memory within individual web applications. Memory dumps Memory dumps can be very useful for diagnosing issues and debugging apps. Using a REST API, you can now get a memory dump of your sites, which you can then use for investigating issues in Visual Studio Debugger, WinDbg, and other tools. Scaling Sites Independently Prior to today’s release, all sites scaled up/down together whenever you scaled any site in a sub-region. So you may have had to keep your proof-of-concept or testing sites in a separate sub-region if you wanted to keep them in the Free tier. This will no longer be necessary.  Windows Azure Web Sites can now mix different tier levels in the same geographic sub-region. This allows you, for example, to selectively move some of your sites in the West US sub-region up to Standard tier when they require the features, scalability, and SLA of the Standard tier. Full pricing details on Windows Azure Web Sites can be found here.  Note that the “Shared Tier” of Windows Azure Web Sites remains in preview mode (and continues to have discounted preview pricing).  Mobile Services: General Availability Release of Windows Azure Mobile Services I’m incredibly excited to announce the General Availability release of Windows Azure Mobile Services.  Mobile Services is perfect for building scalable cloud back-ends for Windows 8.x, Windows Phone, Apple iOS, Android, and HTML/JavaScript applications.  Customers We’ve seen tremendous adoption of Windows Azure Mobile Services since we first previewed it last September, and more than 20,000 customers are now running mobile back-ends in production using it.  These customers range from startups like Yatterbox, to university students using Mobile Services to complete apps like Sly Fox in their spare time, to media giants like Verdens Gang finding new ways to deliver content, and telcos like TalkTalk Business delivering the up-to-the-minute information their customers require.  In today’s Build keynote, we demonstrated how TalkTalk Business is using Windows Azure Mobile Services to deliver service, outage and billing information to its customers, wherever they might be. Partners When we unveiled the source control and Custom API features I blogged about two weeks ago, we enabled a range of new scenarios, one of which is a more flexible way to work with third party services.  The following blogs, samples and tutorials from our partners cover great ways you can extend Mobile Services to help you build rich modern apps: New Relic allows developers to monitor and manage the end-to-end performance of iOS and Android applications connected to Mobile Services. SendGrid eliminates the complexity of sending email from Mobile Services, saving time and money, while providing reliable delivery to the inbox. Twilio provides a telephony infrastructure web service in the cloud that you can use with Mobile Services to integrate phone calls, text messages and IP voice communications into your mobile apps. Xamarin provides a Mobile Services add on to make it easy building cross-platform connected mobile aps. Pusher allows quickly and securely add scalable real-time messaging functionality to Mobile Services-based web and mobile apps. Visual Studio 2013 and Windows 8.1 This week during //build/ keynote, we demonstrated how Visual Studio 2013, Mobile Services and Windows 8.1 make building connected apps easier than ever. Developers building Windows 8 applications in Visual Studio can now connect them to Windows Azure Mobile Services by simply right clicking then choosing Add Connected Service. You can either create a new Mobile Service or choose existing Mobile Service in the Add Connected Service dialog. Once completed, Visual Studio adds a reference to Mobile Services SDK to your project and generates a Mobile Services client initialization snippet automatically. Add Push Notifications Push Notifications and Live Tiles are a key to building engaging experiences. Visual Studio 2013 and Mobile Services make it super easy to add push notifications to your Windows 8.1 app, by clicking Add a Push Notification item: The Add Push Notification wizard will then guide you through the registration with the Windows Store as well as connecting your app to a new or existing mobile service. Upon completion of the wizard, Visual Studio will configure your mobile service with the WNS credentials, as well as add sample logic to your client project and your mobile service that demonstrates how to send push notifications to your app. Server Explorer Integration In Visual Studio 2013 you can also now view your Mobile Services in the the Server Explorer. You can add tables, edit, and save server side scripts without ever leaving Visual Studio, as shown on the image below: Pricing With today’s general availability release we are announcing that we will be offering Mobile Services in three tiers – Free, Standard, and Premium.  Each tier is metered using a simple pricing model based on the # of API calls (bandwidth is included at no extra charge), and the Standard and Premium tiers are backed by 99.9% monthly SLAs.  You can elastically scale up or down the number of instances you have of each tier to increase the # of API requests your service can support – allowing you to efficiently scale as your business grows. The following table summarizes the new pricing model (full pricing details here):   You can find the full details of the new pricing model here. Build Conference Talks The //BUILD/ conference will be packed with sessions covering every aspect of developing connected applications with Mobile Services. The best part is that, even if you can’t be with us in San Francisco, every session is being streamed live. Be sure not to miss these talks: Mobile Services – Soup to Nuts — Josh Twist Building Cross-Platform Apps with Windows Azure Mobile Services — Chris Risner Connected Windows Phone Apps made Easy with Mobile Services — Yavor Georgiev Build Connected Windows 8.1 Apps with Mobile Services — Nick Harris Who’s that user? Identity in Mobile Apps — Dinesh Kulkarni Building REST Services with JavaScript — Nathan Totten Going Live and Beyond with Windows Azure Mobile Services — Kirill Gavrylyuk , Paul Batum Protips for Windows Azure Mobile Services — Chris Risner AutoScale: Dynamically scale up/down your app based on real-world usage One of the key benefits of Windows Azure is that you can dynamically scale your application in response to changing demand. In the past, though, you have had to either manually change the scale of your application, or use additional tooling (such as WASABi or MetricsHub) to automatically scale your application. Today, we’re announcing that AutoScale will be built-into Windows Azure directly.  With today’s release it is now enabled for Cloud Services, Virtual Machines and Web Sites (Mobile Services support will come soon). Auto-scale enables you to configure Windows Azure to automatically scale your application dynamically on your behalf (without any manual intervention) so you can achieve the ideal performance and cost balance. Once configured it will regularly adjust the number of instances running in response to the load in your application. Currently, we support two different load metrics: CPU percentage Storage queue depth (Cloud Services and Virtual Machines only) We’ll enable automatic scaling on even more scale metrics in future updates. When to use Auto-Scale The following are good criteria for services/apps that will benefit from the use of auto-scale: The service/app can scale horizontally (e.g. it can be duplicated to multiple instances) The service/app load changes over time If your app meets these criteria, then you should look to leverage auto-scale. How to Enable Auto-Scale To enable auto-scale, simply navigate to the Scale tab in the Windows Azure Management Portal for the app/service you wish to enable.  Within the scale tab turn the Auto-Scale setting on to either CPU or Queue (for Cloud Services and VMs) to enable Auto-Scale.  Then change the instance count and target CPU settings to configure the Auto-Scale ranges you want to maintain. The image below demonstrates how to enable Auto-Scale on a Windows Azure Web-Site.  I’ve configured the web-site so that it will run using between 1 and 5 VM instances.  The exact # used will depend on the aggregate CPU of the VMs using the 40-70% range I’ve configured below.  If the aggregate CPU goes above 70%, then Windows Azure will automatically add new VMs to the pool (up to the maximum of 5 instances I’ve configured it to use).  If the aggregate CPU drops below 40% then Windows Azure will automatically start shutting down VMs to save me money: Once you’ve turned auto-scale on, you can return to the Scale tab at any point and select Off to manually set the number of instances. Using the Auto-Scale Preview With today’s update you can now, in just a few minutes, have Windows Azure automatically adjust the number of instances you have running  in your apps to keep your service performant at an even better cost. Auto-scale is being released today as a preview feature, and will be free until General Availability. During preview, each subscription is limited to 10 separate auto-scale rules across all of the resources they have (Web sites, Cloud services or Virtual Machines). If you hit the 10 limit, you can disable auto-scale for any resource to enable it for another. Alerts and Notifications Starting today we are now providing the ability to configure threshold based alerts on monitoring metrics. This feature is available for compute services (cloud services, VM, websites and mobiles services). Alerts provide you the ability to get proactively notified of active or impending issues within your application.  You can define alert rules for: Virtual machine monitoring metrics that are collected from the host operating system (CPU percentage, network in/out, disk read bytes/sec and disk write bytes/sec) and on monitoring metrics from monitoring web endpoint urls (response time and uptime) that you have configured. Cloud service monitoring metrics that are collected from the host operating system (same as VM), monitoring metrics from the guest VM (from performance counters within the VM) and on monitoring metrics from monitoring web endpoint urls (response time and uptime) that you have configured. For Web Sites and Mobile Services, alerting rules can be configured on monitoring metrics from monitoring endpoint urls (response time and uptime) that you have configured. Creating Alert Rules You can add an alert rule for a monitoring metric by navigating to the Setting -> Alerts tab in the Windows Azure Management Portal. Click on the Add Rule button to create an alert rule. Give the alert rule a name and optionally add a description. Then pick the service which you want to define the alert rule on: The next step in the alert creation wizard will then filter the monitoring metrics based on the service you selected:   Once created the rule will show up in your alerts list within the settings tab: The rule above is defined as “not activated” since it hasn’t tripped over the CPU threshold we set.  If the CPU on the above machine goes over the limit, though, I’ll get an email notifying me from an Windows Azure Alerts email address ([email protected]). And when I log into the portal and revisit the alerts tab I’ll see it highlighted in red.  Clicking it will then enable me to see what is causing it to fail, as well as view the history of when it has happened in the past. Alert Notifications With today’s initial preview you can now easily create alerting rules based on monitoring metrics and get notified on active or impending issues within your application that require attention. During preview, each subscription is limited to 10 alert rules across all of the services that support alert rules. No More Credit Card Requirement for MSDN Subscribers Earlier this month (during TechEd 2013), Windows Azure announced that MSDN users will get Windows Azure Credits every month that they can use for any Windows Azure services they want. You can read details about this in my previous Dev/Test blog post. Today we are making further updates to enable an easier Windows Azure signup for MSDN users. MSDN users will now not be required to provide payment information (e.g. no credit card) during sign-up, so long as they use the service within the included monetary credit for the billing period. For usage beyond the monetary credit, they can enable overages by providing the payment information and remove the spending limit. This enables a super easy, one page sign-up experience for MSDN users.  Simply sign-up for your Windows Azure trial using the same Microsoft ID that you use to manage your MSDN account, then complete the one page sign-up form below and you will be able to spend your free monthly MSDN credits (up to $150 each month) on any Windows Azure resource for dev/test:   This makes it trivially easy for every MDSN customer to start using Windows Azure today.  If you haven’t signed up yet, I definitely recommend checking it out. Summary Today’s release includes a ton of great features that enable you to build even better cloud solutions.  If you don’t already have a Windows Azure account, you can sign-up for a free trial and start using all of the above features today.  Then visit the Windows Azure Developer Center to learn more about how to build apps with it. Hope this helps, Scott P.S. In addition to blogging, I am also now using Twitter for quick updates and to share links. Follow me at: twitter.com/scottgu

  Read the article

• Tech Article: Tired of Null Pointer Exceptions? Use Java SE 8's Optional!

  - by Tori Wieldt

  A wise man once said you are not a real Java programmer until you've dealt with a null pointer exception. The null reference is the source of many problems because it is often used to denote the absence of a value. Java SE 8 introduces a new class called java.util.Optional that can alleviate some of these problems. In the tech article "Tired of Null Pointer Exceptions? Use Java SE 8's Optional!" Java expert Raoul-Gabriel Urma shows you how to make your code more readable and protect it against null pointer exceptions. Urma explains "The purpose of Optional is not to replace every single null reference in your codebase but rather to help design better APIs in which—just by reading the signature of a method—users can tell whether to expect an optional value. In addition, Optional forces you to actively unwrap an Optional to deal with the absence of a value; as a result, you protect your code against unintended null pointer exceptions." Learn how to go from writing painful nested null checks to writing declarative code that is composable, readable, and better protected from null pointer exceptions. Read "Tired of Null Pointer Exceptions? Use Java SE 8's Optional!"

  Read the article

• What purpose does “using” serve when used the following way

  - by user287745

  What purpose does “using” serve when used the following way:- ONE EXAMPLE IS THIS, (AN ANSWERER- @richj - USED THIS CODE TO SOLVE A PROBLEM THANKS) private Method(SqlConnection connection) { using (SqlTransaction transaction = connection.BeginTransaction()) { try { // Use the connection here .... transaction.Commit(); } catch { transaction.Rollback(); throw; } } } OTHER EXAMPLE I FOUND WHILE READING ON MICROSOFT SUPPORT SITE public static void ShowSqlException(string connectionString) { string queryString = "EXECUTE NonExistantStoredProcedure"; StringBuilder errorMessages = new StringBuilder(); using (SqlConnection connection = new SqlConnection(connectionString)) { SqlCommand command = new SqlCommand(queryString, connection); try { command.Connection.Open(); command.ExecuteNonQuery(); } catch (SqlException ex) { for (int i = 0; i < ex.Errors.Count; i++) { errorMessages.Append("Index #" + i + "\n" + "Message: " + ex.Errors[i].Message + "\n" + "LineNumber: " + ex.Errors[i].LineNumber + "\n" + "Source: " + ex.Errors[i].Source + "\n" + "Procedure: " + ex.Errors[i].Procedure + "\n"); } Console.WriteLine(errorMessages.ToString()); } } } I AM doing at top of page as using system.data.sqlclient etc so why this using thing in middle of code, What if I omit it (I know the code will work) but what functionality will I be losing

  Read the article

• purpose of 3rd party mvc ?

  - by Honey

  ive seen many third party mvcs or frameworks such as codeignitor , cakephp, and so on. what i want to know is what are their purposes? ive created my own framework call it an mvc or framework (in my opinion their all the same). in my framework i have all the classes in one folder called classes and all functions in another. its all organized and when a new project comes in i am able to complete it fast. i have looked at the applications that i mentioned and it seems to have huge articles and tutorials to study. what is the purpose? why not study the main language such as php, javascript/ajax or jquery, and so on then build something that you know the ins and outs of so that any project comes your way you know what to do. ive known some people who use cakephp and for every project they get stuck and need to figure out what to do. another guy i knew worked with joomla and every basic company website that came his way he would reverse engineer joomla to make it work with the site. are people using these applications because they lack knowledge in the languages? or sometimes have no choice but to make a site while lacking language and put something together.

  Read the article

• What's the purpose of "import package"?

  - by codethief

  As I just found out import package does not make the package's modules available through package.module. The same obviously holds true for from package import subpackage as well as from package import * What's the purpose of importing a package at all then if I can't access its submodules but only the objects defined in __init__.py? It makes sense to me that from package import * would bloat the namespace, which, however, doesn't apply in case of the other two ways! I also understand that loading all submodules might take a long time. But I don't know what these unwanted side-effects, "that should only happen when the sub-module is explicitly imported", are which the author of the previous link mentions. To me it looks like doing an import package[.subpackage] (or from package import subpackage) makes absolutely no sense if I don't exactly want to access objects provided in __init__.py. Are those unwanted side effects really that serious that the language actually has to protect the programmer from causing them? Actually, I thought that Python was a little bit more about "If the programmer wants to do it, let him do it." In my case, I really do want to import all submodules with the single statement from package import subpackage, because I need all of them! Telling Python in the init.py file which submodules I'm exactly talking about (all of them!) is quite cumbersome from my point of view. Please enlighten me. :)

  Read the article

• Best practices for JQuery namespaces + general purpose utility functions

  - by Armchair Bronco

  What are some current "rules of thumb" for implementing JQuery namespaces to host general purpose utility functions? I have a number of JavaScript utility methods scattered in various files that I'd like to consolidate into one (or more) namespaces. What's the best way to do this? I'm currently looking at two different syntaxes, listed in order of preference: //****************************** // JQuery Namespace syntax #1 //****************************** if (typeof(MyNamespace) === "undefined") { MyNamespace = {}; } MyNamespace.SayHello = function () { alert("Hello from MyNamespace!"); } MyNamespace.AddEmUp = function (a, b) { return a + b; } //****************************** // JQuery Namespace syntax #2 //****************************** if (typeof (MyNamespace2) === "undefined") { MyNamespace2 = { SayHello: function () { alert("Hello from MyNamespace2!"); }, AddEmUp: function (a, b) { return a + b; } }; } Syntax #1 is more verbose but it seems like it would be easier to maintain down the road. I don't need to add commas between methods, and I can left align all my functions. Are there other, better ways to do this?

  Read the article

• The Purpose of a Service Layer and ASP.NET MVC 2

  - by user332022

  In an effort to understand MVC 2 and attempt to get my company to adopt it as a viable platform for future development, I have been doing a lot of reading lately. Having worked with ASP.NET pretty exclusively for the past few years, I had some catching up to do. Currently, I understand the repository pattern, models, controllers, data annotations, etc. But there is one thing that is keeping me from completely understanding enough to start work on a reference application. The first is the Service Layer Pattern. I have read many blog posts and questions here on Stack Overflow, but I still don't completely understand the purpose of this pattern. I watched the entire video series at MVCCentral on the Golf Tracker Application and also looked at the demo code he posted and it looks to me like the service layer is just another wrapper around the repository pattern that doesn't perform any work at all. I also read this post: http://www.asp.net/Learn/mvc/tutorial-38-cs.aspx and it seemed to somewhat answer my question, however, if you are using data annotations to perform your validation, this seems unnecessary. I have looked for demonstrations, posts, etc. but I can't seem to find anything that simply explains the pattern and gives me compelling evidence to use it. Can someone please provide me with a 2nd grade (ok, maybe 5th grade) reason to use this pattern, what I would lose if I don't, and what I gain if I do?a

  Read the article

• Finally, upgrade from Nokia X3 to Samsung Galaxy S III

  This time, something slightly different but nonetheless not less interesting, hopefully. Living on a remote island like Mauritius, ill-praised 'Cyber Island' in the Indian Ocean, has its advantages in life style and relaxed environment to life in but in terms of technological aspects it can be quite a nightmare. Well, I guess this might be different story to report about... one day. Cyber Island Mauritius Despite it's shiny advertisement as Cyber Island and business in ICT hub to Africa, Mauritius is not on the latest track of available models in computer hardware or, in the context of this article, cellulars or smart-phone, or communication technology in general. Okay, I have to admit that this statement is only partly true. Money can buy, even here in Mauritius. Luckily, there are ways and ways to deal with this outcry of modern, read: technological, civilisation issues. Online shopping you might think? Yes, for sure, until you discover in your checkout procedure that a small island in the Indian Ocean isn't a preferred destination for delivery and the precious time you spent on putting your items into your cart and feeding your personal level of anticipation gets ruined on the last stint. Ordering from abroad saves you money Anyway, I got in touch with my personal courier and luckily there were some extra-kilos left in the luggage. First obstacle sorted, we have a Transporter! Okay, on the next occasion off to Amazon online and using their Prime service for fast delivery. Actually, the order was placed on Saturday evening and everything got delivered on Tuesday morning - nice job in less than 72 hours. Okay, among the items of that shopping rush I ordered a shiny Samsung Galaxy S III 16GB in oceanic blue - did I mention, that you hardly get a blue model in Mauritius? - for my BWE. Interesting side-notes: First, Amazon Germany dropped the prices for roughly 30% on the S3, and we got the 16GB model for less than 500 Euro (or approx. Rs. 19.500,-) compared to the usual Rs. 27.000,- on the local market. It even varies whether the local price is inclusive or exclusive VAT (15%). Second, since a while she was bothering me to get an iPhone and an iPad for her, fair enough I thought, decent hardware, posh design and reliable services. Until we watched the 'magical' introduction of Samsung's new models at the IFA exhibition, she read the bashing comments on Google+ on the iPhone 5 and I gave her a brief summary on the law suit between Apple and Samsung in the USA. So, yes, Samsung USA is right, the next big thing is already here - literally. My BWE loves the look and touch of the Galaxy S3. And for me it was more cost-effective in terms of purchases done at the App Store, ups, Play Store. Transfer of contacts, text messages and media files Okay, now that the hardware is in place, how to transfer all those contacts, text messages, media files, etc. between those two devices? In the past, I used to use the Nokia Communication Suite between various models but now for Android? Well, as usual Google and Bing are reliable friends and among the first hits I came across an article about How to Transfer Contacts from Nokia to Android. Couldn't be easier, right? Well, sort of... my main Windows systems are already running on Windows 8, and this actually caused problems with the mobile/smart-phone device drivers. The article provides the download for an older version 1.10 which upgrades to 2.11 (as time of writing this entry) but both couldn't get the Galaxy S3 and the Nokia connected. Shame on me... the product page clearly doesn't mention Windows 8 (for now) and Windows 8 isn't available for the general audience at all... After I took a spare machine running on Windows Vista everything went smooth. Software installed, upgrade done, device drivers for Android automatically downloaded and installed, and the same painless routine for the Nokia part. I think, I rebooted the system twice during the whole setup procedure but hey, it was more or less a distraction while coding some stuff in ASP.NET MVC and Telerik Kendo UI. The transfer of contacts and text messages was done via Wondershare MobileGo for Android, and all media files by moving the additional microSD card from one device to the other. But even without an external SD card, it would have been very easy to copy the files via Windows Explorer directly. Little catch and excellent service Fine, we are almost done and the only step left is to shift the SIM card... Ouch, gotcha! The X3 uses a standard size SIM card while the S III only accepts microSIM form factor. What an irony, bigger smartphone needs smaller SIM card. Luckily, the next showroom of Emtel is just 5 mins away up the road, and the service staff over there know their job. Finally, after roughly 10 mins of paper work, activation and small chit-chat, the S3 came to life on the mobile network. Owning a smart-phone now and knowing that my BWE would like to interact more on social networks away from home, especially to upload pictures and provide local 'check-ins', I activated a data package for her in advance, too. Even that it is Saturday, everything was already done and ready to be used. Nice bonus: The Emtel clerk directly offered me to set up the configuration for the Emtel data services, yes sure, go ahead, this saves me to search for that in the settings. Okay, spoiler-alert here, setting a static APN to access the Emtel network and the internet wouldn't be a challenge. But hey, she already had the phone in her hands and I could keep my eyes on the children. Well done, Emtel! Resume Thanks to the useful software package by Wondershare is was a hands-free experience to transfer all the data from a Nokia mobile on Symbian S60 to a Samsung Galaxy S III on Android Ice Cream Sandwich (ICS). In the future, this wont be a serious issue at all anymore thanks to synchronisation services and cloud storage. And for now, I'm only waiting for the official upgrades for Jelly Bean.

  Read the article

• What does "general purpose system" mean for Java SE Embedded?

  - by Majid Azimi

  The Oracle website says this about Java SE Embedded license: development is free, but royalties are required upon deployment on anything other than general purpose systems What does "general purpose system" mean here? We have a sensor network around the country. On each box we have installed, there is a micro controller based board that gets data from the environment and send data on serial port to a ARM based embedded board. On this board system there is a Java process which reads and submits data to our central server using JMS. Is this categorized as general purpose system? Sorry I'm asking this here. We are in Iran, there is no Oracle office here to ask.

  Read the article

• .NET Reference "Copy Local" True / Fasle Being Set Based on Contents of General Assembly

  - by D-Sect

  Hello All. First question for me here. We had a very interesting problem with a Win Forms project. It's been resolved. We know what happened, but we want to understand why it happened. This may help other people out in the future who have a similar problem. The WinForms project failed on 2 of our client's PCs. The error was an obscure kernel.dll error. The project ran fine on 3 other PCs. We found that a .DLL (log4net.dll - a very popular open-source logging library) was missing from our release folder. It was previously in our release folder. Why was it missing in this latest release? It was missing because I must have installed a program on my Dev box that used log4net.dll and it was added to the general assembly. When I checked the SLN's references for log4net.dll, they were changed to "copy local=FALSE". They must have changed automagicially because log4net.dll was present in my GAC. Here's where my question starts: Why did my reference for log4net.dll get changed from COPY LOCAL = TRUE to COPY LOCAL = FALSE? I suspect it's because it was added to my GAC by another program. How can we prevent this from happening again? As it stands now, if I install a piece of software that uses a common library and it adds it to my GAC, then my SLNs that REF that DLL will change from Copy Local TRUE to FALSE. Thank you so much. I hope this helps people out who have a piece of software that runs in some places, but not in others, when it used to run fine in ALL places.

  Read the article

• Architecting iPhone Views - seeking help on a specific issue + general advice

  - by Ev

  Hi there, I am a web developer (rails, python) that is new to iPhone development. I've done some desktop development in the past within the MS environment (C#). I'm trying to build a really simple iPhone application and I am confused by the way that views work in general. If someone can provide advice for my particular problem, along with some resources where I can learn how to architect iPhone views in the future, that would be awesome. I feel like a lot of the Apple documentation that I've come across is too specific - I am lacking a fundamental understanding of how views work on the iPhone. My particular problem looks like this: I need one view that displays some downloaded text content. This is the view that shows when the app loads, and it is pretty straightforward. Then I need a settings area (I've already decided I don't want to use the iPhone settings area). The settings area main page will have some text fields on it. It will also have a 2-row grouped table. Each cell in that table will take you to another view which also has a grouped table used for multi-select. I suspect that I can reuse the same view for these two final "detailed setting" views. In summary: home page settings main page detailed setting 1 detailed setting 2 Any help and advice appreciated.

  Read the article

• Deployments and TFS, general questions

  - by Velika

  SOX requires that we have a separate group deploy our ASP.NET web to production. Currently, that group has access to our current code repository in VSS and uses VSS to deploy code that has been checked into VSS. How are deployments typically done for web applications? As a developer, I have used the Deploy function in Visual Studio to deploy code to a network share which corresponds to a IS virtual folder, but I don't think we can expect that the deployment group will be purchasing a copy of Visual Studio just to do deployments. We could check the code into TFS, but what is the minimum software that that group would need to perform the deployment? Would a Team Explorer Client Access suffice? I am aware that Team System has functionality to automate the building of an application. Do people typically deploy to Production by copying aspx and dlls files from the QA environment to production or do you normally deploy from TFS or even VS directly? It seems to me that the preferred approach would be to deploy from the QA environment, since that is the environment that must have been approved for release or that those files should be checked into TFS and the deployed from TFS, assuming you can deploy from TFS. What confuses me is whether bin (binary) files that are local to the project-do they go into TFS? Is so, doesn't this create problems for other developers in that only 1 developers-the one with the binary checked - can actually debug because debugging requires write access to the binaries? Does this mean that the binaries shouldn't be checked into TFS? But eventually, if you deploy from TFS, the binaries HAVE to be added to TFS. Are they added as a separate (compiled) application node? If so,m this sounds real ugly. I would assume not. How does one ensure that the binaries match the source code that we mark with a particular version number? Obviously, I'm clueless. Can someone give me a general idea of how you handle version control and deployments in particular using TFS?

  Read the article

• is there an equivalent of a trigger for general stored procedure execution on sql server

  - by Arj

  Hi All, Hope you can help. Is there a way to detect when a stored proc is being run on SQL Server without altering the SP itself? Here's the requirement. We need to track users running reports from our enterprise data warehouse as the core product we use doesn't allow for this. Both core product reports and a slew of in-house ones we've added all return their data from individual stored procs. We don't have a practical way of altering the parts of the product webpages where reports are called from. We also can't change the stored procs for the core product reports. (It would be trivial to add a logging line to the start/end of each of our inhouse ones). What I'm trying to find therefore, is whether there's a way in SQL Server (2005 / 2008) to execute a logging stored proc whenever any other stored procedure runs, without altering those stored procedures themselves. We have general control over the SQL Server instance itself as it's local, we just don't want to change the product stored procs themselves. Any one have any ideas? Is there a kind of "stored proc executing trigger"? Is there an event model for SQL Server that we can hook custom .Net code into? (Just to discount it from the start, we want to try and make a change to SQL Server rather than get into capturing the report being run from the products webpages etc) Thoughts appreciated Thanks

  Read the article

• Handling data update/freshness issue in web-app in general (or GWT specifically)

  - by edwin.nathaniel

  In general, how do you guys handle user update/data freshness interaction with the user (UI issue) in web-apps? For example: Multi-users web-app (like project management) Login to a "virtual" space People can update project names, etc How to handle a situation such that: user-A and user-B load a project with title "Project StackOverflow" user-B updates the title to "Project StackExchange" user-A updates the title after user-B update operation to "Project Basecamp" The question I'm asking is from the user perspective (UI) and not about transactional operation. What do most people do in this situation? What would you do after user-B updates the title in user-A screen/view? What happened when user-A tries to update the title after user-B finished his/her update operation? do you inform user-A that the title has changed and he/she has to reload the page? do you go ahead and change the title and let user-B has old data? Do you do some sort of application-level "locking" mechanism? (if someone is updating, nobody else can?) Or fix the application workflow? (who has the access to be able to change things, etc). What would be the simplest solution, but at the same time not annoy the user with more dialog/warning messages. I've encountered this particular problem frequently in a GWT app specifically where domain models are being passed around and refreshing the whole app/client-side isn't the optimal solution in my mind (since it means the whole "loading"/initialization phase must be executed again in this specific environment). Maybe the answer is to stay away from GWT? :) Love to hear options, solutions, and advises from you guys. Thanks

  Read the article

< Previous Page | 6 7 8 9 10 11 12 13 14 15 16 17  | Next Page >