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  • What common programming problems are best solved by using prototypes and closures?

    - by vemv
    As much as I understand both concepts, I can't see how can I take advantage of JavaScript's closures and prototypes aside from using them for creating instantiable and/or encapsulated class-like blocks (which seems more of a workaround than an asset to me) Other JS features such as functions-as-values or logical evaluation of non-booleans are much easier to fall in love with... What common programming problems are best solved by using propotypal inheritance and closures?

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  • How to only render part of an image in lwjgl/openGL

    - by Ephyxia
    I'm making a mining/building game in java using slick2D and I want to make it so you can only see a few blocks in any direction while you are underground. The best example I could find of what I want to do is the game miner dig deep. One way I thought of doing it would be to have a large image and just draw transparent areas on it where you need to be able too see but even if that would be an efficient method I wouldn't be sure how to do that.

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  • How can I move a library inside a project's source tree and compiling static binaries?

    - by AbrahamVanHelpsing
    How can I move a library inside a project's source tree and compiling static binaries? I want to use a particular tool that utilizes ANCIENT binaries without upgrading it's API usage. This way I can use the old libraries inside the single binary without wrecking the local host environment. I am on nix with netbeans/eclipse/code::blocks. I don't have a problem reading, just looking for a starting point. Any thoughts?

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  • Raid superblock missing on single parition. Recovery needed!

    - by user171639
    Ok so I have a 2 TB raid 1 setup that has three partitions: sdc1: linux sdc2: swap sdc3: LVM for data However the LVM will no longer mount. So I thought that I would take the first drive, mount it in linux (ive done this b4), and reset the spare drive to copy the data. Normally I can mount a single drive for data recovery using: sudo su apt-get install mdadm lvm2 mdadm --assemble --scan modprobe dm-mod vgscan vgchange -ay c mount -o ro /dev/c/c /mnt Unfortunately, vgscan doesnot recognize the data partition. It appears as though the superblock on the first drive's data partition was erased while syncing with the second. So now I cannot mount that partition and the second drive is stuck in spare mode. Any ideas? Or a way to force mount the data partition just to copy the data? knoppix@Microknoppix:~$ sudo su root@Microknoppix:/home/knoppix# apt-get install mdadm lvm2 Reading package lists... Done Building dependency tree Reading state information... Done lvm2 is already the newest version. mdadm is already the newest version. 0 upgraded, 0 newly installed, 0 to remove and 551 not upgraded. root@Microknoppix:/home/knoppix# mdadm --assemble --scan mdadm: /dev/md/1 has been started with 1 drive (out of 2). mdadm: /dev/md/0 has been started with 1 drive (out of 2). root@Microknoppix:/home/knoppix# modprobe dm-mod root@Microknoppix:/home/knoppix# vgscan Reading all physical volumes. This may take a while... No volume groups found root@Microknoppix:/home/knoppix# cat /proc/mdstat Personalities : [raid1] md0 : active raid1 sdc1[2] 4193268 blocks super 1.2 [2/1] [U_] md1 : active raid1 sdc2[2] 524276 blocks super 1.2 [2/1] [U_] unused devices: <none> root@Microknoppix:/home/knoppix# mdadm -v --assemble --auto=yes /dev/md2 /dev/sdc3 mdadm: looking for devices for /dev/md2 mdadm: no recogniseable superblock on /dev/sdc3 mdadm: /dev/sdc3 has no superblock - assembly aborted root@Microknoppix:/home/knoppix# dumpe2fs /dev/md0 | grep -i superblock dumpe2fs 1.42.4 (12-Jun-2012) Primary superblock at 0, Group descriptors at 1-1 Backup superblock at 32768, Group descriptors at 32769-32769 Backup superblock at 98304, Group descriptors at 98305-98305 Backup superblock at 163840, Group descriptors at 163841-163841 Backup superblock at 229376, Group descriptors at 229377-229377 Backup superblock at 294912, Group descriptors at 294913-294913 Backup superblock at 819200, Group descriptors at 819201-819201 Backup superblock at 884736, Group descriptors at 884737-884737 root@Microknoppix:/home/knoppix# Notes: I can read the super block from the spare drive. I was gonna try and restore the superblock from one of the backups, but i dont know how or if this would work. I also heard creating a new array (mdadm --create) using the same parameters will not delete the data on the drive but i didnt want to risk it. Recommendations?

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  • Why am I getting such slow file transfer performance?

    - by kingdango
    Copying 4GB from a USB flash drive to my Linux partition. The flash drive is NTFS formatted (I believe, it's Windows formatted). The transfer is incredibly slow and blocks the computer frequently causing lag and hanging applications. My transfer rate is 1.2 MB/sec and that is the max it has hit when I let the File Operations window have focus. Why is this so slow under Ubuntu and significantly faster in Win 7?

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  • Why can't Java/C# implement RAII?

    - by mike30
    Question: Why can't Java/C# implement RAII? Clarification: I am aware the garbage collector is not deterministic. So with the current language features it is not possible for an object's Dispose() method to be called automatically on scope exit. But could such a deterministic feature be added? My understanding: I feel an implementation of RAII must satisfy two requirements: 1. The lifetime of a resource must be bound to a scope. 2. Implicit. The freeing of the resource must happen without an explicit statement by the programmer. Analogous to a garbage collector freeing memory without an explicit statement. The "implicitness" only needs to occur at point of use of the class. The class library creator must of course explicitly implement a destructor or Dispose() method. Java/C# satisfy point 1. In C# a resource implementing IDisposable can be bound to a "using" scope: void test() { using(Resource r = new Resource()) { r.foo(); }//resource released on scope exit } This does not satisfy point 2. The programmer must explicitly tie the object to a special "using" scope. Programmers can (and do) forget to explicitly tie the resource to a scope, creating a leak. In fact the "using" blocks are converted to try-finally-dispose() code by the compiler. It has the same explicit nature of the try-finally-dispose() pattern. Without an implicit release, the hook to a scope is syntactic sugar. void test() { //Programmer forgot (or was not aware of the need) to explicitly //bind Resource to a scope. Resource r = new Resource(); r.foo(); }//resource leaked!!! I think it is worth creating a language feature in Java/C# allowing special objects that are hooked to the stack via a smart-pointer. The feature would allow you to flag a class as scope-bound, so that it always is created with a hook to the stack. There could be a options for different for different types of smart pointers. class Resource - ScopeBound { /* class details */ void Dispose() { //free resource } } void test() { //class Resource was flagged as ScopeBound so the tie to the stack is implicit. Resource r = new Resource(); //r is a smart-pointer r.foo(); }//resource released on scope exit. I think implicitness is "worth it". Just as the implicitness of garbage collection is "worth it". Explicit using blocks are refreshing on the eyes, but offer no semantic advantage over try-finally-dispose(). Is it impractical to implement such a feature into the Java/C# languages? Could it be introduced without breaking old code?

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  • PMDB Block Size Choice

    - by Brian Diehl
    Choosing a block size for the P6 PMDB database is not a difficult task. In fact, taking the default of 8k is going to be just fine. Block size is one of those things that is always hotly debated. Everyone has their personal preference and can sight plenty of good reasons for their choice. To add to the confusion, Oracle supports multiple block sizes withing the same instance. So how to decide and what is the justification? Like most OLTP systems, Oracle Primavera P6 has a wide variety of data. A typical table's average row size may be less than 50 bytes or upwards of 500 bytes. There are also several tables with BLOB types but the LOB data tends not to be very large. It is likely that no single block size would be perfect for every table. So how to choose? My preference is for the 8k (8192 bytes) block size. It is a good compromise that is not too small for the wider rows, yet not to big for the thin rows. It is also important to remember that database blocks are the smallest unit of change and caching. I prefer to have more, individual "working units" in my database. For an instance with 4gb of buffer cache, an 8k block will provide 524,288 blocks of cache. The following SQL*Plus script returns the average, median, min, and max rows per block. column "AVG(CNT)" format 999.99 set verify off select avg(cnt), median(cnt), min(cnt), max(cnt), count(*) from ( select dbms_rowid.ROWID_RELATIVE_FNO(rowid) , dbms_rowid.ROWID_BLOCK_NUMBER(rowid) , count(*) cnt from &tab group by dbms_rowid.ROWID_RELATIVE_FNO(rowid) , dbms_rowid.ROWID_BLOCK_NUMBER(rowid) ) Running this for the TASK table, I get this result on a database with an 8k block size. Each activity, on average, has about 19 rows per block. Enter value for tab: task AVG(CNT) MEDIAN(CNT) MIN(CNT) MAX(CNT) COUNT(*) -------- ----------- ---------- ---------- ---------- 18.72 19 3 28 415917 I recommend an 8k block size for the P6 transactional database. All of our internal performance and scalability test are done with this block size. This does not mean that other block sizes will not work. Instead, like many other parameters, this is the safest choice.

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  • External 1TB WD USB 3.0 HDD is not detecting. Working perfectly find in Windows

    - by Yathi
    My 1TB USB 3.0 was working fine earlier in Ubuntu as well as Windows. But lately it is not at all being detected in Ubuntu. It still works fine in Windows. I did update my Ubuntu to 12.10 but I am not sure if that caused the issue. When I connect my HDD and run dmesg | tail: [ 47.804676] usb 4-3: >Device not responding to set address. [ 48.008575] usb 4-3: >Device not responding to set address. [ 48.212421] usb 4-3: >device not accepting address 9, error -71 [ 48.324451] usb 4-3: >Device not responding to set address. [ 48.528340] usb 4-3: >Device not responding to set address. [ 48.732165] usb 4-3: >device not accepting address 10, error -71 [ 48.844138] usb 4-3: >Device not responding to set address. [ 49.048179] usb 4-3: >Device not responding to set address. [ 49.251881] usb 4-3: >device not accepting address 11, error -71 [ 49.251907] hub 4-0:1.0: >unable to enumerate USB device on port 3 The output of sudo fdisk -l is : Disk /dev/sda: 1000.2 GB, 1000204886016 bytes 255 heads, 63 sectors/track, 121601 cylinders, total 1953525168 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 4096 bytes I/O size (minimum/optimal): 4096 bytes / 4096 bytes Disk identifier: 0x00030cde Device Boot Start End Blocks Id System /dev/sda1 2048 1332981759 666489856 83 Linux /dev/sda2 1332981760 1953523711 310270976 5 Extended /dev/sda5 1332983808 1349365759 8190976 82 Linux swap / Solaris /dev/sda6 1349367808 1953523711 302077952 7 HPFS/NTFS/exFAT Disk /dev/sdb: 120.0 GB, 120034123776 bytes 255 heads, 63 sectors/track, 14593 cylinders, total 234441648 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x000a2519 Device Boot Start End Blocks Id System /dev/sdb1 * 2048 103368703 51683328 7 HPFS/NTFS/exFAT /dev/sdb2 103368704 154568703 25600000 83 Linux /dev/sdb3 154568704 234440703 39936000 7 HPFS/NTFS/exFAT /dev/sda and /dev/sdb are my 2 internal HDDs. But the external one which should be /dev/sdc is not even being shown though it is connected and the LED on the HDD is glowing. Someone had suggested adding blacklist uas to /etc/modprobe.d/blacklist.conf. Tried that as well. But still not working. Can someone help me out.

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  • Is it possible (and practical) to search a string for arbitrary-length repeating patterns?

    - by blz
    I've recently developed a huge interest in cryptography, and I'm exploring some of the weaknesses of ECB-mode block ciphers. A common attack scenario involves encrypted cookies, whose fields can be represented as (relatively) short hex strings. Up until now, I've relied on my eyes to pick out repeating blocks, but this is rather tedious. I'm wondering what kind of algorithms (if any) could help me automate my search for repeating patterns within a string. Can anybody point me in the right direction?

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  • CMake : système de compilation sort en version 3.0, nouveaux générateurs, variables, propriétés et meilleure gestion de la compilation croisée

    CMake 3 est maintenant disponible ! Découvrez les nouveautés du système de compilation multiplateforme Nouvelles pages de manuel, dont une pour Qt, nouveaux générateurs et de multiples autres apports CMake est un système de compilation et de construction de projets multiplateforme et Open Source. À l'aide d'un simple fichier CMakeLists.txt décrivant votre projet, CMake sera capable de le générer des fichiers pour votre EDI préférés. En résumé, il configure votre projet Visual Studio, Code::Blocks,...

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  • SQL SERVER – Reducing CXPACKET Wait Stats for High Transactional Database

    - by pinaldave
    While engaging in a performance tuning consultation for a client, a situation occurred where they were facing a lot of CXPACKET Waits Stats. The client asked me if I could help them reduce this huge number of wait stats. I usually receive this kind of request from other client as well, but the important thing to understand is whether this question has any merits or benefits, or not. Before we continue the resolution, let us understand what CXPACKET Wait Stats are. The official definition suggests that CXPACKET Wait Stats occurs when trying to synchronize the query processor exchange iterator. You may consider lowering the degree of parallelism if a conflict concerning this wait type develops into a problem. (from BOL) In simpler words, when a parallel operation is created for SQL Query, there are multiple threads for a single query. Each query deals with a different set of the data (or rows). Due to some reasons, one or more of the threads lag behind, creating the CXPACKET Wait Stat. Threads which came first have to wait for the slower thread to finish. The Wait by a specific completed thread is called CXPACKET Wait Stat. Note that CXPACKET Wait is done by completed thread and not the one which are unfinished. “Note that not all the CXPACKET wait types are bad. You might experience a case when it totally makes sense. There might also be cases when this is also unavoidable. If you remove this particular wait type for any query, then that query may run slower because the parallel operations are disabled for the query.” Now let us see what the best practices to reduce the CXPACKET Wait Stats are. The suggestions, with which you will find that if you search online through the browser, would play a major role as and might be asked about their jobs In addition, might tell you that you should set ‘maximum degree of parallelism’ to 1. I do agree with these suggestions, too; however, I think this is not the final resolutions. As soon as you set your entire query to run on single CPU, you will get a very bad performance from the queries which are actually performing okay when using parallelism. The best suggestion to this is that you set ‘the maximum degree of parallelism’ to a lower number or 1 (be very careful with this – it can create more problems) but tune the queries which can be benefited from multiple CPU’s. You can use query hint OPTION (MAXDOP 0) to run the server to use parallelism. Here is the two-quick script which helps to resolve these issues: Change MAXDOP at Server Level EXEC sys.sp_configure N'max degree of parallelism', N'1' GO RECONFIGURE WITH OVERRIDE GO Run Query with all the CPU (using parallelism) USE AdventureWorks GO SELECT * FROM Sales.SalesOrderDetail ORDER BY ProductID OPTION (MAXDOP 0) GO Below is the blog post which will help you to find all the parallel query in your server. SQL SERVER – Find Queries using Parallelism from Cached Plan Please note running Queries in single CPU may worsen your performance and it is not recommended at all. Infect this can be very bad advise. I strongly suggest that you identify the queries which are offending and tune them instead of following any other suggestions. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: SQL, SQL Authority, SQL Optimization, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, SQL White Papers, SQLAuthority News, T SQL, Technology

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  • Clean Code: A Handbook of Agile Software Craftsmanship – book review

    - by DigiMortal
       Writing code that is easy read and test is not something that is easy to achieve. Unfortunately there are still way too much programming students who write awful spaghetti after graduating. But there is one really good book that helps you raise your code to new level – your code will be also communication tool for you and your fellow programmers. “Clean Code: A Handbook of Agile Software Craftsmanship” by Robert C. Martin is excellent book that helps you start writing the easily readable code. Of course, you are the one who has to learn and practice but using this book you have very good guide that keeps you going to right direction. You can start writing better code while you read this book and you can do it right in your current projects – you don’t have to create new guestbook or some other simple application to start practicing. Take the project you are working on and start making it better! My special thanks to Robert C. Martin I want to say my special thanks to Robert C. Martin for this book. There are many books that teach you different stuff and usually you have markable learning curve to go before you start getting results. There are many books that show you the direction to go and then leave you alone figuring out how to achieve all that stuff you just read about. Clean Code gives you a lot more – the mental tools to use so you can go your way to clean code being sure you will be soon there. I am reading books as much as I have time for it. Clean Code is top-level book for developers who have to write working code. Before anything else take Clean Code and read it. You will never regret your decision. I promise. Fragment of editorial review “Even bad code can function. But if code isn’t clean, it can bring a development organization to its knees. Every year, countless hours and significant resources are lost because of poorly written code. But it doesn’t have to be that way. What kind of work will you be doing? You’ll be reading code—lots of code. And you will be challenged to think about what’s right about that code, and what’s wrong with it. More importantly, you will be challenged to reassess your professional values and your commitment to your craft. Readers will come away from this book understanding How to tell the difference between good and bad code How to write good code and how to transform bad code into good code How to create good names, good functions, good objects, and good classes How to format code for maximum readability How to implement complete error handling without obscuring code logic How to unit test and practice test-driven development This book is a must for any developer, software engineer, project manager, team lead, or systems analyst with an interest in producing better code.” Table of contents Clean code Meaningful names Functions Comments Formatting Objects and data structures Error handling Boundaries Unit tests Classes Systems Emergence Concurrency Successive refinement JUnit internals Refactoring SerialDate Smells and heuristics A Concurrency II org.jfree.date.SerialDate Cross references of heuristics Epilogue Index

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  • Pie Charts Just Don't Work When Comparing Data - Number 10 of Top 10 Reasons to Never Ever Use a Pie

    - by Tony Wolfram
    When comparing data, which is what a pie chart is for, people have a hard time judging the angles and areas of the multiple pie slices in order to calculate how much bigger one slice is than the others. Pie Charts Don't Work A slice of pie is good for serving up a portion of desert. It's not good for making a judgement about how big the slice is, what percentage of 100 it is, or how it compares to other slices. People have trouble comparing angles and areas to each other. Controlled studies show that people will overestimate the percentage that a pie slice area represents. This is because we have trouble calculating the area based on the space between the two angles that define the slice. This picture shows how a pie chart is useless in determing the largest value when you have to compare pie slices.   You can't compare angles and slice areas to each other. Human perception and cognition is poor when viewing angles and areas and trying to make a mental comparison. Pie charts overload the working memory, forcing the person to make complicated calculations, and at the same time make a decision based on those comparisons. What's the point of showing a pie chart when you want to compare data, except to say, "well, the slices are almost the same, but I'm not really sure which one is bigger, or by how much, or what order they are from largest to smallest. But the colors sure are pretty. Plus, I like round things. Oh,was I suppose to make some important business decision? Sorry." Bad Choices and Bad Decisions Interaction Designers, Graphic Artists, Report Builders, Software Developers, and Executives have all made the decision to use pie charts in their reports, software applications, and dashboards. It was a bad decision. It was a poor choice. There are always better options and choices, yet the designer still made the decision to use a pie chart. I'll expore why people make such poor choices in my upcoming blog entires. (Hint: It has more to do with emotions than with analytical thinking.) I've outlined my opinions and arguments about the evils of using pie charts in "Countdown of Top 10 Reasons to Never Ever Use a Pie Chart." Each of my next 10 blog entries will support these arguments with illustrations, examples, and references to studies. But my goal is not to continuously and endlessly rage against the evils of using pie charts. This blog is not about pie charts. This blog is about understanding why designers choose to use a pie chart. Why, when give better alternatives, and acknowledging the shortcomings of pie charts, do designers over and over again still freely choose to place a pie chart in a report? As an extra treat and parting shot, check out the nice pie chart that Wikipedia uses to illustrate the United States population by state.   Remember, somebody chose to use this pie chart, with all its glorious colors, and post it on Wikipedia for all the world to see. My next blog will give you a better alternative for displaying comparable data - the sorted bar chart.

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  • Creating a branch for every Sprint

    - by Martin Hinshelwood
    There are a lot of developers using version control these days, but a feature of version control called branching is very poorly understood and remains unused by most developers in favour of Labels. Most developers think that branching is hard and complicated. Its not! What is hard and complicated is a bad branching strategy. Just like a bad software architecture a bad branch architecture, or one that is not adhered to can prove fatal to a project. We I was at Aggreko we had a fairly successful Feature branching strategy (although the developers hated it) that meant that we could have multiple feature teams working at the same time without impacting each other. Now, this had to be carefully orchestrated as it was a Business Intelligence team and many of the BI artefacts do not lend themselves to merging. Today at SSW I am working on a Scrum team delivering a product that will be used by many hundreds of developers. SSW SQL Deploy takes much of the pain out of upgrading production databases when you are not using the Database projects in Visual Studio. With Scrum each Scrum Team works for a fixed period of time on a single sprint. You can have one or more Scrum Teams involved in delivering a product, but all the work must be merged and tested, ready to be shown to the Product Owner at the the Sprint Review meeting at the end of the current Sprint. So, what does this mean for a branching strategy? We have been using a “Main” (sometimes called “Trunk”) line and doing a branch for each sprint. It’s like Feature Branching, but with only ONE feature in operation at any one time, so no conflicts Figure: DEV folder containing the Development branches.   I know that some folks advocate applying a Label at the start of each Sprint and then rolling back if you need to, but I have always preferred the security of a branch. Like: being able to create a release from Main that has Sprint3 code even while Sprint4 is being worked on. being sure I can always create a stable build on request. Being able to guarantee a version (labels are not auditable) Be able to abandon the sprint without having to delete the code (rare I know, but would be a mess if it happened) Being able to see the flow of change sets through to a safe release It helps you find invalid dependencies when merging to Main as there may be some file that is in everyone’s Sprint branch, but never got checked in. (We had this at the merge of Sprint2) If you are always operating in this way as a standard it makes it easier to then add more scrum teams in the future. Muscle memory of this way of working. Don’t Like: Additional DB space for the branches Baseless merging between sprint branches when changes are directly ported Note: I do not think we will ever attempt this! Maybe a bit tougher to see the history between sprint branches since the changes go up through Main and down to another sprint branch Note: What you would have to do is see which Sprint the changes were made in and then check the history he same file in that Sprint. A little bit of added complexity that you would have to do anyway with multiple teams. Over time, you can end up with a lot of old unused sprint branches. Perhaps destroy with /keephistory can help in this case. Note: We ALWAYS delete the Sprint branch after it has been merged into Main. That is the theory anyway, and as you can see from the images Sprint2 has already been deleted. Why take the chance of having a problem rolling back or wanting to keep some of the code, when you can just abandon a branch and start a new one? It just seems easier and less painful to use a branch to me! What do you think?   Technorati Tags: TFS,TFS2010,Software Development,ALM,Branching

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  • App Stores&ndash;In All Things, Its Quality Over Quantity

    - by D'Arcy Lussier
    Everybody has an opinion about Windows 8. People love it, people hate it, people are meh about it, people are apparently buying it from Microsoft stores in NYC as if it was water before a natural disaster…if there’s one thing that Microsoft product launches do well, its the ability to bring out strong emotional responses. Over at eweek.com, Don Reisinger wrote about 5 good and bad things about Windows 8. Yes, another opinion piece on WIndows 8. I figured since this one had good and bad it might be worthwhile to read. I then came across #10 on his list, and figured “What the hell…might as well post a bit of a rant on Windows 8 myself!” Here’s #10: 10. Bad: Too few apps Unfortunately, Microsoft wasn’t able to get too many developers to start producing applications for its Windows 8 Store. Microsoft hasn’t yet released official numbers, but some have said that the marketplace has less than 8,000 programs. Considering Apple’s App Store has 100 times that, it’s about time Microsoft starts leaning on developers to get more programs into its store. Believe me, Microsoft *has* been leaning on developers to get apps into the store. I’ve been asked at least 5 or 6 times from 5 or 6 different friends at Microsoft about whether I was going to write a Windows 8 app. I think Microsoft felt they had to try and address the number of apps available in their marketplace, since some people (like Don) would draw comparisons to the number of apps in the Apple marketplace. I feel for Microsoft in this, since the number of apps in a marketplace are an empty stat. Quality of Quantity I have an iPad that my family (wife, 10yo daughter, 3yo daughter) use. We all have our own apps installed on it. In addition, my wife has an iPhone 4S that she also installs apps on. As someone who gets asked by his kids often whether they can buy/download an app, the vast majority of the vast catalogue of iOS marketplace apps are crap! Do you realize how many “free” games are out there, only to really be not-free because you have to purchase in-game content to make the game actually playable? And how about searching – with such a vast array of apps and such high numbers of craptastic ones, trying to find something is incredibly difficult and can be frustrating. I would rather see that Microsoft has 8000 high quality apps in their store at launch, instead of 800000 that were mostly junk. Too Few Apps?! And seriously, 8000 is not a small number. How many iOS apps have I actually bought between the iPad and iPhone? I’ll be generous and say 30…heck, let’s round it up to 40. It’s not like I have 10,000 apps installed on my iPad, nor will that ever happen! So if people have, at the *launch* of a new platform ecosystem, EIGHT THOUSAND apps to choose from, I don’t see that as a fail at all! It should be noted that most of the most common apps (Netflix, Skype, etc.) are available for Windows 8 at launch – I guess I’ll have to wait a few weeks for My Pony Ranch and all its clones to start showing up; pity. Let’s Check Back in a Year So look, let’s check back in a year’s time and see what the app store looks like. My hope is that Microsoft doesn’t continue to push quantity over quality. Even knowing the optics that # of apps in the store carries and the pressure to catch Apple and Android marketplaces, I hope Microsoft avoids the scenario where there’s a good percentage of apps in the Windows Store that are utter rubbish and finding the gems will be cumbersome. But if that happens, we can thank guys like Dan who raised the false issue of app count at the launch for it.

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  • The theory of evolution applied to software

    - by Michel Grootjans
    I recently realized the many parallels you can draw between the theory of evolution and evolving software. Evolution is not the proverbial million monkeys typing on a million typewriters, where one of them comes up with the complete works of Shakespeare. We would have noticed by now, since the proverbial monkeys are now blogging on the Internet ;-) One of the main ideas of the theory of evolution is the balance between random mutations and natural selection. Random mutations happen all the time: millions of mutations over millions of years. Most of them are totally useless. Some of them are beneficial to the evolved species. Natural selection favors the beneficially mutated species. Less beneficial mutations die off. The mutated rabbit doesn't have to be faster than the fox. It just has to be faster than the other rabbits.   Theory of evolution Evolving software Random mutations happen all the time. Most of these mutations are so bad, the new species dies off, or cannot reproduce. Developers write new code all the time. New ideas come up during the act of writing software. The really bad ones don't get past the stage of idea. The bad ones don't get committed to source control. Natural selection favors the beneficial mutated species Good ideas and new code gets discussed in group during informal peer review. Less than good code gets refactored. Enhanced code makes it more readable, maintainable... A good set of traits makes the species superior to others. It becomes widespread A good design tends to make it easier to add new features, easier to understand the current implementations, easier to optimize for performance...thus superior. The best designs get carried over from project to project. They appear in blogs, articles and books about principles, patterns and practices.   Of course the act of writing software is deliberate. This can hardly be called random mutations. Though it sometimes might seem that code evolves through a will of its own ;-) Does this mean that evolving software (evolution) is better than a big design up front (creationism)? Not necessarily. It's a false idea to think that a project starts from scratch and everything evolves from there. Everyone carries his experience of what works and what doesn't. Up front design is necessary, but is best kept simple and minimal, just enough to get you started. Let the good experiences and ideas help to drive the process, whether they come from you or from others, from past experience or from the most junior developer on your team. Once again, balance is the keyword. Balance design up front with evolution on a daily basis. How do you know what balance is right? Through your own experience of what worked and what didn't (here's evolution again). Notes: The evolution of software can quickly degenerate without discipline. TDD is a discipline that leaves little to chance on that part. Write your test to describe the new behavior. Write just enough code to make it behave as specified. Refactor to evolve the code to a higher standard. The responsibility of good design rests continuously on each developers' shoulders. Promiscuous pair programming helps quickly spreading the design to the whole team.

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  • When row estimation goes wrong

    - by Dave Ballantyne
    Whilst working at a client site, I hit upon one of those issues that you are not sure if that this is something entirely new or a bug or a gap in your knowledge. The client had a large query that needed optimizing.  The query itself looked pretty good, no udfs, UNION ALL were used rather than UNION, most of the predicates were sargable other than one or two minor ones.  There were a few extra joins that could be eradicated and having fixed up the query I then started to dive into the plan. I could see all manor of spills in the hash joins and the sort operations,  these are caused when SQL Server has not reserved enough memory and has to write to tempdb.  A VERY expensive operation that is generally avoidable.  These, however, are a symptom of a bad row estimation somewhere else, and when that bad estimation is combined with other estimation errors, chaos can ensue. Working my way back down the plan, I found the cause, and the more I thought about it the more i came convinced that the optimizer could be making a much more intelligent choice. First step is to reproduce and I was able to simplify the query down a single join between two tables, Product and ProductStatus,  from a business point of view, quite fundamental, find the status of particular products to show if ‘active’ ,’inactive’ or whatever. The query itself couldn’t be any simpler The estimated plan looked like this: Ignore the “!” warning which is a missing index, but notice that Products has 27,984 rows and the join outputs 14,000. The actual plan shows how bad that estimation of 14,000 is : So every row in Products has a corresponding row in ProductStatus.  This is unsurprising, in fact it is guaranteed,  there is a trusted FK relationship between the two columns.  There is no way that the actual output of the join can be different from the input. The optimizer is already partly aware of the foreign key meta data, and that can be seen in the simplifiction stage. If we drop the Description column from the query: the join to ProductStatus is optimized out. It serves no purpose to the query, there is no data required from the table and the optimizer knows that the FK will guarantee that a matching row will exist so it has been removed. Surely the same should be applied to the row estimations in the initial example, right ?  If you think so, please upvote this connect item. So what are our options in fixing this error ? Simply changing the join to a left join will cause the optimizer to think that we could allow the rows not to exist. or a subselect would also work However, this is a client site, Im not able to change each and every query where this join takes place but there is a more global switch that will fix this error,  TraceFlag 2301. This is described as, perhaps loosely, “Enable advanced decision support optimizations”. We can test this on the original query in isolation by using the “QueryTraceOn” option and lo and behold our estimated plan now has the ‘correct’ estimation. Many thanks goes to Paul White (b|t) for his help and keeping me sane through this

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  • AI to move custom-shaped spaceships (shape affecting movement behaviour)

    - by kaoD
    I'm designing a networked turn based 3D-6DOF space fleet combat strategy game which relies heavily on ship customization. Let me explain the game a bit, since you need to know a bit about it to set the question. What I aim for is the ability to create your own fleet of ships with custom shapes and attached modules (propellers, tractor beams...) which would give advantages and disadvantages to each ship, so you have lots of different fleet distributions. E.g., long ship with two propellers at the side would let the ship spin around that plane easily, bigger ships would move slowly unless you place lots of propellers at the back (therefore spending more "construction" points and energy when moving, and it will only move fast towards that direction.) I plan to balance all the game around this feature. The game would revolve around two phases: orders and combat phase. During the orders phase, you command the different ships. When all players finish the order phase, the combat phase begins and the ship orders get resolved in real-time for some time, then the action pauses and there's a new orders phase. The problem comes when I think about player input. To move a ship, you need to turn on or off different propellers if you want to steer, travel forward, brake, rotate in place... These propellers don't have to work at their whole power, so you can achieve more movement combinations with less propellers. I think this approach is a bit boring. The player doesn't want to fiddle with motors or anything, you just want to MOVE and KILL. The way I intend the player to give orders to these ships is by a destination and a rotation, and then the AI would calculate the correct propeller power to achive that movement and rotation. Propulsion doesn't have to be the same throught the entire turn calculation (after the orders have been given) so it would be cool if the ships reacted as they move, adjusting the power of the propellers for their needs dynamically, but it may be too hard to implement and it's not really needed for the game to work. In both cases, how would that AI decide which propellers to activate for the best (or at least not worst) trajectory to be achieved? I though about some approaches: Learning AI: The ship types would learn about their movement by trial and error, adjusting their behaviour with more uses, and finally becoming "smart". I don't want to get involved THAT far in AI coding, and I think it can be frustrating for the player (even if you can let it learn without playing.) Pre-calculated timestep movement: Upon ship creation, ALL possible movements are calculated for each propeller configuration and power for a given delta-time. Memory intensive, ugly, bad. Pre-calculated trajectories: The same as above but not for each delta-time but the whole trajectory, which would then be fitted as much as possible. Requires a fixed propeller configuration for the whole combat phase and is still memory intensive, ugly and bad. Continuous brute forcing: The AI continously checks ALL possible propeller configurations throughout the entire combat phase, precalculates a few time steps and decides which is the best one based on that. Con: what's good now might not be that good later, and it's too CPU intensive, ugly, and bad too. Single brute forcing: Same as above, but only brute forcing at the beginning of the simulation, so it needs constant propeller configuration throughout the entire combat phase. Coninuous angle check: This is not a full movement method, but maybe a way to discard "stupid" propeller configurations. Given the current propeller's normal vector and the final one, you can approximate the power needed for the propeller based on the angle. You must do this continuously throughout the whole combat phase. I figured this one out recently so I didn't put in too much thought. A priori, it has the "what's good now might not be that good later" drawback too, and it doesn't care about the other propellers which may act together to make a better propelling configuration. I'm really stuck here. Any ideas?

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  • Incentivizing Work with Development Teams

    - by MarkPearl
    Recently I saw someone on twitter asking about incentives and if anyone had past experience with incentivizing work. I promised to respond with some of the experiences I have had in the past so here goes... **Disclaimer** - these are my experiences with incentives, generally in software development - in some other industries this may not be applicable – this is also my thinking at this point in time, with more experience my opinion may change. Incentivize at the level that you want people to group at If you are wanting to promote a team mentality, incentivize teams. If you want to promote an individual mentality, incentivize individuals. There is nothing worse than mixing this up. Some organizations put a lot of effort in establishing teams and team mentalities but reward individuals. This has a counter effect on the resources they have put towards establishing a team mentality. In the software projects that I work with we want promote cross functional teams that collaborate. Personally, if I was on a team and knew that there was an opportunity to work on a critical component of the system, and that by doing so I would get a bigger bonus, then I would be hesitant to include other people in solving that problem. Thus, I would hinder the teams efforts in being cross functional and reduce collaboration levels. Does that mean everyone in the team should get an even share of an incentive? In most situations I would say yes - even though this may feel counter-intuitive. I have heard arguments put forward that if “person x contributed more than person Y then they should be rewarded more” – This may sound controversial but I would rather treat people how would you like them to perform, not where they currently are at. To add to this approach, if someone is free loading, you bet your bottom dollar that the team is going to make this a lot more transparent if they feel that individual is going to be rewarded at the same level that everyone else is. Bad incentives promote destructive work If you are going to incentivize people, pick you incentives very carefully. I had an experience once with a sales person who was told they would get a bonus provided that they met an ordering target with a particular supplier. What did this person do? They sold everything at cost for the next month or so. They reached the goal, but the company didn't gain anything from it. It was a bad incentive. Expect the same with development teams, if you incentivize zero bug levels, you will get zero code committed to the solution. If you incentivize lines of code, you will get many many lines of bad code. Is there such a thing as a good incentives? Monetary wise, I am not sure there is. I would much rather encourage organizations to pay their people what they are worth upfront. I would also advise against paying money to teams as an incentive or even a bonus or reward for reaching a milestone. Rather have a breakaway for the team that promotes team building as a reward if they reach a milestone than pay them more money. I would also advise against making the incentive the reason for them to reach the milestone. If this becomes the norm it promotes people to begin to only do their job if there is an incentive at the end of the line. This is not a behaviour one wants to encourage. If the team or individual is in the right mind-set, they should not work any harder than they are right now with normal pay.

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  • Is hidden content (display: none;) -indexed- by search engines? [closed]

    - by user568458
    Possible Duplicate: How bad is it to use display: none in CSS? We've established on this site before (in this question) that, since there are so many legitimate uses for hiding content with display: none; when creating interactive features, that sites aren't automatically penalised for content that is hidden this way (so long as it doesn't look algorithmically spammy). Google's Webmaster guidelines also make clear that a good practice when using content that is initially legitimately hidden for interactivity purposes is to also include the same content in a <noscript> tag, and Google recommend that if you design and code for users including users with screen readers or javascript disabled, then 9 times out of 10 good relevant search rankings will follow (though their specific advice seems more written for cases where javascript writes new content to the page). JavaScript: Place the same content from the JavaScript in a tag. If you use this method, ensure the contents are exactly the same as what’s contained in the JavaScript, and that this content is shown to visitors who do not have JavaScript enabled in their browser. So, best practice seems pretty clear. What I can't find out is, however, the simple factual matter of whether hidden content is indexed by search engines (but with potential penalties if it looks 'spammy'), or, whether it is ignored, or, whether it is indexed but with a lower weighting (like <noscript> content is, apparently). (for bonus points it would be great to know if this varies or is consistent between display: none;, visibility: hidden;, etc, but that isn't crucial). This is different to the other questions on display:none; and SEO - those are about good and bad practice and the answers are discussions of good and bad practice, I'm interested simply in the factual 'Yes or no' question of whether search engines index, or ignore, content that is in display: none; - something those other questions' answers aren't totally clear on. One other question has an answer, "Yes", supported by a link to an article that doesn't really clear things up: it establishes that search engines can spot that text is hidden, it discusses (again) whether hidden text causes sites to be marked as spam, and ultimately concludes that in mid 2011, Google's policy on hidden text was evolving, and that they hadn't at that time started automatically penalising display:none; or marking it as spam. It's clear that display: none; isn't always spam and isn't always treated as spam (many Google sites use it...): but this doesn't clear up how, or if, it is indexed. What I will do will be to follow the guidelines and make sure that all the content that is initially hidden which regular users can explore using javascript-driven interactivity is also structured in way that noscript/screenreader users can use. So I'm not interested in best practice, opinions etc because best practice seems to be really clear: accessibility best practices boosts SEO. But I'd like to know what exactly will happen: whether any display: none; content I have alongside <noscript> or otherwise accessibility-optimised content will be be ignored, or indexed again, or picked up to compare against the <noscript> content but not indexed... etc.

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  • Error In centos6 while compiling java classes,in tomcat6

    - by AJIT RANA
    I am newbie to Linux and Centos6. I bought server just now and want to deploy my web app in it. I am getting error while I am compiling my servlet classes. It showing me bash: javac: command not found when I try to compile my classes. But when I checked my class in '/usr/lib/jvm/java-1.6.0/bin .'I found my javac there. Then I checked javac with the help of command ./javac i got ERROR.. [root:ip_address.com]# ./javac There is insufficient memory for the Java Runtime Environment to continue. pthread_getattr_np Error occurred during initialization of VM java.lang.OutOfMemoryError: unable to create new native thread I followed the step as shown in "" Java outofmemoryerror when creating <100 threads "" which shows me command to get limits.. '[root:ipaddress.com]# ulimit -a core file size (blocks, -c) unlimited data seg size (kbytes, -d) unlimited scheduling priority (-e) 0 file size (blocks, -f) unlimited pending signals (-i) 278528 max locked memory (kbytes, -l) 32 max memory size (kbytes, -m) unlimited open files (-n) 1024 pipe size (512 bytes, -p) 8 POSIX message queues (bytes, -q) 819200 real-time priority (-r) 0 stack size (kbytes, -s) 10240 cpu time (seconds, -t) unlimited max user processes (-u) 1024 virtual memory (kbytes, -v) unlimited file locks (-x) unlimited' [root:ipaddress.com]# top bash: top: command not found link :- http://stackoverflow.com/q/12913857/1746764

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  • raid md device is not remove from memory, how to overcome this problem

    - by santhosha
    i create raid 10 , i removed two arrays form md11 one by one , after that i going to editing the contents those are mounted ( it will be not responding stage), after i try for remove arrays those are left it is shows device or resource busy ( is not removed from memory). i try to terminate process this is also not work, i absorve from 4 days resync will be 8.0% it can not modifying. cat /proc/mdstat Personalities : [raid1] [raid0] [raid6] [raid5] [raid4] [linear] [raid10] md11 : active raid10 sde1[3] sdj14 286743936 blocks 64K chunks 2 near-copies [4/1] [___U] [1:2:3:0] [=...................] resync = 8.0% (23210368/286743936) finish=289392.6min speed=15K/sec mdadm -D /dev/md11 /dev/md11: Version : 00.90.03 Creation Time : Sun Jan 16 16:20:01 2011 Raid Level : raid10 Array Size : 286743936 (273.46 GiB 293.63 GB) Device Size : 143371968 (136.73 GiB 146.81 GB) Raid Devices : 4 Total Devices : 2 Preferred Minor : 11 Persistence : Superblock is persistent Update Time : Sun Jan 16 16:56:07 2011 State : active, degraded, resyncing Active Devices : 1 Working Devices : 1 Failed Devices : 1 Spare Devices : 0 Layout : near=2, far=1 Chunk Size : 64K Rebuild Status : 8% complete UUID : 5e124ea4:79a01181:dc4110d3:a48576ea Events : 0.23 Number Major Minor RaidDevice State 0 0 0 0 removed 1 0 0 1 removed 4 8 145 2 faulty spare rebuilding /dev/sdj1 3 8 65 3 active sync /dev/sde1 umount /dev/md11 umount: /dev/md11: not mounted mdadm -S /dev/md11 mdadm: fail to stop array /dev/md11: Device or resource busy lsof /dev/md11 COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME mount 2128 root 3r BLK 9,11 4058 /dev/md11 mount 5018 root 3r BLK 9,11 4058 /dev/md11 mdadm 27605 root 3r BLK 9,11 4058 /dev/md11 mount 30562 root 3r BLK 9,11 4058 /dev/md11 badblocks 30591 root 3r BLK 9,11 4058 /dev/md11 kill -9 2128 kill -9 5018 kill -9 27605 kill -9 30562 kill -3 30591 mdadm -S /dev/md11 mdadm: fail to stop array /dev/md11: Device or resource busy lsof /dev/md11 COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME mount 2128 root 3r BLK 9,11 4058 /dev/md11 mount 5018 root 3r BLK 9,11 4058 /dev/md11 mdadm 27605 root 3r BLK 9,11 4058 /dev/md11 mount 30562 root 3r BLK 9,11 4058 /dev/md11 badblocks 30591 root 3r BLK 9,11 4058 /dev/md11 cat /proc/mdstat Personalities : [raid1] [raid0] [raid6] [raid5] [raid4] [linear] [raid10] md11 : active raid10 sde1[3] sdj14 286743936 blocks 64K chunks 2 near-copies [4/1] [___U] [1:2:3:0] [=...................] resync = 8.0% (23210368/286743936) finish=289392.6min speed=15K/sec

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  • Why does my dd backup of MacBook OS X fail to boot upon restore?

    - by James
    I created a backup of a MacBook hard drive (WD2500BEVS-88US) by hooking it up as a secondary drive on my linux system (Ubuntu 10.10). I used the following command: sudo dd if=/dev/sdc of=/home/backup.img bs=2M This appears to have completed with no errors. I noticed that the file is only 68 GB in size even though the drive is 250 GB in capacity. I restored the image to a spare drive (WD2500BEVS) with the following command: sudo dd if=/home/backup.img of=/dev/sdb bs=2M When I boot the spare drive in the Mac, it appears to start up for a few seconds and then shuts down. (It does not appear to load into the OS at all). When I open up the drive that won't boot in GParted, it looks like this: When looking at the information for the middle partition with the little red exclamation mark, it shows this: The original hard drive that boots ok shows up like this: Further info on both drives: sudo fdisk -l Disk /dev/sdb: 250.1 GB, 250059350016 bytes 255 heads, 63 sectors/track, 30401 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00000000 Device Boot Start End Blocks Id System /dev/sdb1 1 30402 244198580 ee GPT WARNING: GPT (GUID Partition Table) detected on '/dev/sdc'! The util fdisk doesn't support GPT. Use GNU Parted. Disk /dev/sdc: 250.1 GB, 250059350016 bytes 255 heads, 63 sectors/track, 30401 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00000000 Device Boot Start End Blocks Id System /dev/sdc1 1 30402 244198580 ee GPT So why is my backup or restore failing? Why is dd not creating a byte for byte duplicate?

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  • CoreStore Encryption Error on Mac Lion

    - by Michael
    I am trying to encrypt an external drive using diskutil CoreStorage on Mac Lion 10.7.4. I thought the only requirements were that the drive have GUID partition scheme and Journaled HFS+ file system. I think my drive is configured accordingly but when I type the following command I get an error message back: Michaels-MacBook-Pro:~ Michael$ diskutil cs convert disk2 -passphrase TestPassword Error converting disk to CoreStorage: The given file system is not supported on Core Storage (-69756) Here are the details reported for the drive in question: Michaels-MacBook-Pro:~ Michael$ diskutil list disk2 /dev/disk2 #: TYPE NAME SIZE IDENTIFIER 0: GUID_partition_scheme *500.1 GB disk2 1: EFI 209.7 MB disk2s1 2: Apple_HFS Test1 499.8 GB disk2s2 Michaels-MacBook-Pro:~ Michael$ diskutil list disk2 /dev/disk2 #: TYPE NAME SIZE IDENTIFIER 0: GUID_partition_scheme *500.1 GB disk2 1: EFI 209.7 MB disk2s1 2: Apple_HFS Test1 499.8 GB disk2s2 Michaels-MacBook-Pro:~ Michael$ diskutil info disk2s2 Device Identifier: disk2s2 Device Node: /dev/disk2s2 Part of Whole: disk2 Device / Media Name: Test1 Volume Name: Test1 Escaped with Unicode: Test1 Mounted: Yes Mount Point: /Volumes/Test1 Escaped with Unicode: /Volumes/Test1 File System Personality: Journaled HFS+ Type (Bundle): hfs Name (User Visible): Mac OS Extended (Journaled) Journal: Journal size 40960 KB at offset 0xe8e000 Owners: Disabled Partition Type: Apple_HFS OS Can Be Installed: Yes Media Type: Generic Protocol: FireWire SMART Status: Not Supported Volume UUID: 1024D0B8-1C45-3057-B040-AE5C3841DABF Total Size: 499.8 GB (499763888128 Bytes) (exactly 976101344 512-Byte-Blocks) Volume Free Space: 499.3 GB (499315826688 Bytes) (exactly 975226224 512-Byte-Blocks) Device Block Size: 512 Bytes Read-Only Media: No Read-Only Volume: No Ejectable: Yes Whole: No Internal: No I'm a little concerned that the "Partition Type: Apple_HFS" entry is causing the problem, but I don't know how to change that. I only seem to be able to control the "File System Personality: Journaled HFS+" in Disk Utility. Can anyone shed some light on this for me?

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  • Slow VM on esxi 4.1

    - by user57432
    We have a FreeBSD 64bit running on a esxi 4.1, the hardware platform is a DELL R710 with 2 x 56xx (intel 6core cpu) and 48 GB ram. The FreeBSD vm is very slow, when we compiles/builds something on it, it takes 5 minuts and it says "build time 18 seconds.". There's no vmtools installed on the vm. The same vm is installaed on another R710 running esxi 4.0 for dell and there's no problems with that one. Does anyone have any idea about what to look for? the VMs on the second server (ESXi 4.1) is a clone of the VMs running on the first VMserver (ESXi 4.0 Dell edition). It's not possible for me to move the VM back to the first server since the file contaning the vm is too big. We installed the new esxi with a datasore with 8mb blocks because 1mb blocks dident allow for the file size we needed. It looks like the www server on the new ESXi 4.1 works fine, but I havent really tested it. There's not installed vmtools on any of the VMs (FreeBSD). The block size on the second VM (ESXi 4.1) datastorage is 8mb and 1mb on the first (ESXi 4.0)

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