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  • Big Data – Beginning Big Data Series Next Month in 21 Parts

    - by Pinal Dave
    Big Data is the next big thing. There was a time when we used to talk in terms of MB and GB of the data. However, the industry is changing and we are now moving to a conversation where we discuss about data in Petabyte, Exabyte and Zettabyte. It seems that the world is now talking about increased Volume of the data. In simple world we all think that Big Data is nothing but plenty of volume. In reality Big Data is much more than just a huge volume of the data. When talking about the data we need to understand about variety and volume along with volume. Though Big data look like a simple concept, it is extremely complex subject when we attempt to start learning the same. My Journey I have recently presented on Big Data in quite a few organizations and I have received quite a few questions during this roadshow event. I have collected all the questions which I have received and decided to post about them on the blog. In the month of October 2013, on every weekday we will be learning something new about Big Data. Every day I will share a concept/question and in the same blog post we will learn the answer of the same. Big Data – Plenty of Questions I received quite a few questions during my road trip. Here are few of the questions. I want to learn Big Data – where should I start? Do I need to know SQL to learn Big Data? What is Hadoop? There are so many organizations talking about Big Data, and every one has a different approach. How to start with big Data? Do I need to know Java to learn about Big Data? What is different between various NoSQL languages. I will attempt to answer most of the questions during the month long series in the next month. Big Data – Big Subject Big Data is a very big subject and I no way claim that I will be covering every single big data concept in this series. However, I promise that I will be indeed sharing lots of basic concepts which are revolving around Big Data. We will discuss from fundamentals about Big Data and continue further learning about it. I will attempt to cover the concept so simple that many of you might have wondered about it but afraid to ask. Your Role! During this series next month, I need your one help. Please keep on posting questions you might have related to big data as blog post comments and on Facebook Page. I will monitor them closely and will try to answer them as well during this series. Now make sure that you do not miss any single blog post in this series as every blog post will be linked to each other. You can subscribe to my feed or like my Facebook page or subscribe via email (by entering email in the blog post). Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Big Data, PostADay, SQL, SQL Query, SQL Server, SQL Tips and Tricks, T SQL

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  • SQL SERVER – Performance Tuning Resolution

    - by pinaldave
    This blog post is written in response to T-SQL Tuesday hosted by MidnightDBAs. Taking resolutions is such an interesting subject. I think just like records, these are broken way more often. I find this is the funniest thing as we all take resolutions every year but not every year, we can manage to keep them. Well, does it mean we should not take resolutions? In fact I support resolutions. Every year, I take a resolution that I will strive reduce my body weight and I usually manage to keep eating healthy till the end of January. When February begins, I begin to loose focus from my goal and as March starts, the “As usual” eating habits begin. Looking at the positive side, what would happen if every year I do not eat healthy in January, I think that might cause terrible consequences to my health in the long run. So keeping resolutions is a good practise and following them to the extent one can is commendable. Let us come back to the world of SQL Server. What is my resolution for year 2011 for SQL Server? There are many, I am going to list three of very important resolutions that I have taken this new year over here. To understand SQL Server Performance Tuning at a deeper Level I think I am already half way through. I have been being very much busy during any given month doing hands-on performance tuning for at least 12 days on an average. That means, I am doing this activity for almost doing 2 weeks a month. I believe that I have a good understanding of the subject. Note that the word that I have used is “good,” and not “best.” There are often cases when I am stumped, and I have no clue of what to do next. Then, I usually go for my “trial and error” method - whichever method works, I make sure to keep a note on my blog. My goal is that I should never ever go for the trial and error method again to achieve the same solution. I should know the solution right away when I see the problem. I do understand that Performance Tuning can be a strange animal at times and one cannot guess the right step every time. However, aiming a high goal never hurts and I am going to learn more and more in this focused area. Going further from Basic BI understanding I do fairly decent with BI concepts. I know the nbasics of SSIS, SSRS, SSAS, PowerPivot and SharePoint (and few other things MDS, StreamInsight, etc). However, I still consider myself as a beginner. I do not have hands-on experience like many other BI Gurus around. I think I want to take my learning further in this direction. I do not want to be a BI expert as the first step but the goal is to move ahead from basic level towards an advanced level. I am going to start presenting in User Group Sessions and other places on this subject. When I have to prepare new subject for presentations, I think I force myself to learn more. I am committed to learn a bit more in this direction. Learning new features SQL Server 2011 Denali This is new thing from “Microsoft” for all the SQL Geeks. I am eagerly waiting for final product later this year and I am planning to learn it well. I think if I follow my above two goals, I think this goal will be automatically covered. I am eager and excited for this new offering from Microsoft. I guess, these are my resolutions; may be next year about the same time, I must revisit this post and see how much successful I am in following my goal. On a lighter note, I am particularly fan of following cartoon strip (Courtesy: Calvin and Hobbes). I think when we cannot resolve our resolutions, we tend to act like Calvin. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: About Me, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • Project Euler 12: (Iron)Python

    - by Ben Griswold
    In my attempt to learn (Iron)Python out in the open, here’s my solution for Project Euler Problem 12.  As always, any feedback is welcome. # Euler 12 # http://projecteuler.net/index.php?section=problems&id=12 # The sequence of triangle numbers is generated by adding # the natural numbers. So the 7th triangle number would be # 1 + 2 + 3 + 4 + 5 + 6 + 7 = 28. The first ten terms # would be: # 1, 3, 6, 10, 15, 21, 28, 36, 45, 55, ... # Let us list the factors of the first seven triangle # numbers: # 1: 1 # 3: 1,3 # 6: 1,2,3,6 # 10: 1,2,5,10 # 15: 1,3,5,15 # 21: 1,3,7,21 # 28: 1,2,4,7,14,28 # We can see that 28 is the first triangle number to have # over five divisors. What is the value of the first # triangle number to have over five hundred divisors? import time start = time.time() from math import sqrt def divisor_count(x): count = 2 # itself and 1 for i in xrange(2, int(sqrt(x)) + 1): if ((x % i) == 0): if (i != sqrt(x)): count += 2 else: count += 1 return count def triangle_generator(): i = 1 while True: yield int(0.5 * i * (i + 1)) i += 1 triangles = triangle_generator() answer = 0 while True: num = triangles.next() if (divisor_count(num) >= 501): answer = num break; print answer print "Elapsed Time:", (time.time() - start) * 1000, "millisecs" a=raw_input('Press return to continue')

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  • How to get Broadcom BCM 43XX Wireless card working

    - by Fer1805
    NOTE - Although this question is for a specific version of Ubuntu and a specific Broadcom model, the answer to it is for most Broadcom models and versions of Ubuntu 11.04, 11.10, 12.04 and 12.10. If you have come here from another question, feel free to read the answer instead. The answer covers many problems with several solutions. I'm having serious problems installing the Broadcom drivers for Ubuntu 11.04. It worked perfectly on my previous version, but now, it is impossible. I'm a user with no advance knowledge in Linux, so I would need clear explanations on make, compile, etc. I was following the instructions on the following blog, with no luck. How can I get Broadcom BCM4311 Wireless working? Can someone help me? Edit: For the command: "lspci | grep Network", I get the following message: 06:00.0 Network controller: Broadcom Corporation BCM4311 802.11b/g WLAN (rev 01) For the command: iwconfig, i get the following: lo no wireless extensions. eth0 no wireless extensions. When i follow the following steps (from the above link), there are a NO error message at all: open the 'Synaptic Package Manager' and search for bcm uninstall the bcm-kernel-source package make sure that the firmware-b43-installer and the b43-fwcutter packages are installed type into terminal: cat /etc/modprobe.d/* | egrep '8180|acx|at76|ath|b43|bcm|CX|eth|ipw|irmware|isl|lbtf|orinoco|ndiswrapper|NPE|p54|prism|rtl|rt2|rt3|rt6|rt7|witch|wl' (you may want to copy this) and see if the term blacklist bcm43xx is there if it is, type cd /etc/modprobe.d/ and then sudo gedit blacklist.conf put a # in front of the line: blacklist bcm43xx then save the file (I was getting error messages in the terminal about not being able to save, but it actually did save properly). reboot 'End of procedure' Before (not ubuntu 11.04), if i wanted to connect wireles, i just went to the icon at the upper side of the screen, click, showed ALL the wireless network available, and done. Now, the only options i see are: Wired Network Auto Eth0 Disconnect VPN Enable networking Connection information Edit connection. hope above info is enough for your help.

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  • How do I handle having too many links on a webpage because of my menu

    - by RandomBen
    I am developing a website that has a drop-down menu at the top of it. The Menu has around 100 links in it that are repeated on every page. Every page also has some number of links below the Menu that may or may not be in the menu itself. My issue is that Google says they generally don't like pages with more than 100 links on them. Is there any way to change the links on the menu so that they no longer "count" towards my max of 100 links? It seems like there should be an easy way to do this but their really doesn't seem to be. the rel=nofollow still counts towards the number of links on the page at least according to Google, so what other options do I have? I looked into where the 100 comes from and I found that it used to be here: http://www.google.com/support/webmasters/bin/answer.py?hl=en&answer=35769#2 but that is no longer the case. I found a more definitive and frankly muddier answer here: http://www.seomoz.org/blog/questions-answers-with-googles-spam-guru from Matt Cutts from 2007. Long story short, in 2007 they still felt 100 links was a good number but they stated you could go far beyond that. In fact, they said that pages with high PageRank could have 2-300. It did sound like having many links could reduce the PageRank of the page with all of the links or possibly all of the items linked to. Also, I know IIS7's SEO 1.0 toolkit suggests that pages should have no more than 250 links.

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  • Getting codebaseHQ SVN ChangeLog data in your application

    - by saifkhan
    I deploy apps via ClickOnce. After each deployment we have to review the changes made and send out an email to the users with the changes. What I decided now to do is to use CodebaseHQ’s API to access a project’s SVN repository and display the commit notes so some users who download new updates can check what was changed or updated in an app. This saves a heck of a lot of time, especially when your apps are in beta and you are making several changes daily based on feedback. You can read up on their API here Here is a sample on how to access the Repositories API from a windows app Public Sub GetLog() If String.IsNullOrEmpty(_url) Then Exit Sub Dim answer As String = String.Empty Dim myReq As HttpWebRequest = WebRequest.Create(_url) With myReq .Headers.Add("Authorization", String.Format("Basic {0}", Convert.ToBase64String(Encoding.ASCII.GetBytes("username:password")))) .ContentType = "application/xml" .Accept = "application/xml" .Method = "POST" End With Try Using response As HttpWebResponse = myReq.GetResponse() Using sr As New System.IO.StreamReader(response.GetResponseStream()) answer = sr.ReadToEnd() Dim doc As XDocument = XDocument.Parse(answer) Dim commits = From commit In doc.Descendants("commit") _ Select Message = commit.Element("message").Value, _ AuthorName = commit.Element("author-name").Value, _ AuthoredDate = DateTime.Parse(commit.Element("authored-at").Value).Date grdLogData.BeginUpdate() grdLogData.DataSource = commits.ToList() grdLogData.EndUpdate() End Using End Using Catch ex As Exception MsgBox(ex.Message) End Try End Sub

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  • Ubuntu 12.10 boots to purple or black screen but intermittently boots fine

    - by Nic
    I have a fresh install of Ubuntu 12.10 64bit dual booting with Win7 64bit. Windows boots fine every time. When I choose Ubuntu from Grub2 menu it will sometimes boot just fine. Most of the times though it gets stuck at a purple screen with nothing happening and no keys or key combinations working. Other times instead of the purple screen I get a black screen with a flashing cursor at the top. Nothing happens. I need to hold down the power button to restart and after a couple times of trying it will eventually boot into Ubuntu. Once that happens everything runs without any problems. I have tried different approaches to fix the problem but to no avail. I tried removing "quiet splash", used no splash, and nomodeset What I got from this was seeing all the text of the boot process but more often than not the process gets stuck right after recognizing all the USB ports and devices. If it gets stuck nothing happens (except when i plug in a usb device: it still recognizes it with a new line of text) In the case when the boot process works, after it lists the usb devices it tells me something like: recovery of read-only filesystem necessary. (its the filesystem that ubuntu runs on) then it does the recovery and i get: recovery complete. after that Ubuntu will boot properly and I get to see the login screen. I have no idea what to do to fix that problem. I have to reboot 3 to 5 times everytime I want to get into Ubuntu and I feel like I'm breaking my new Laptop. (its a lenovo ideapad z580 btw. i5 processor and nvidia gtx640 graphics card) I hope someone can help me. Thanks. Edit: i just got a "failed to enable AA error" message when waking it up from suspend. I don't know if that helps or has anything to do with the boot probs.

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  • What a web developer can learn [closed]

    - by knoxxs
    There are many things to learn in web development. You can easily find what are the most important thing that you need to learn if you want to be a webmaster. Answer to questions about how to become a web developer or a webmaster only contained limited items that someone need to master. (Some eg - a, b ) But the problem is that these resources are not complete. When I started learning web development i follow the same steps. But after learning the basic development I didn't know that I have learnt nothing, there are many more things to learn. I realized this by following blogs , Q&A sites. When I first downloaded the HTNL% Boilerplate, the issue that they have covered, some of them I haven't even heard about. I want you to just suggest what are the possible things, issues that someone can learn and why to learn. I know the answer is follow blogs and do your work you will learn with time, but with these platforms I could get some benefit out of other experiences. This question is not how to become a webmaster, but answer to this may also cover that too.

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  • Is it just me or is this a baffling tech interview question

    - by Matthew Patrick Cashatt
    Background I was just asked in a tech interview to write an algorithm to traverse an "object" (notice the quotes) where A is equal to B and B is equal to C and A is equal to C. That's it. That is all the information I was given. I asked the interviewer what the goal was but apparently there wasn't one, just "traverse" the "object". I don't know about anyone else, but this seems like a silly question to me. I asked again, "am I searching for a value?". Nope. Just "traverse" it. Why would I ever want to endlessly loop through this "object"?? To melt my processor maybe?? The answer according to the interviewer was that I should have written a recursive function. OK, so why not simply ask me to write a recursive function? And who would write a recursive function that never ends? My question: Is this a valid question to the rest of you and, if so, can you provide a hint as to what I might be missing? Perhaps I am thinking too hard about solving real world problems. I have been successfully coding for a long time but this tech interview process makes me feel like I don't know anything. Final Answer: CLOWN TRAVERSAL!!! (See @Matt's answer below) Thanks! Matt

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  • Less Than Four Weeks Away: Oracle OpenWorld Latin America

    - by Oracle OpenWorld Blog Team
    It's only four weeks and counting to Oracle OpenWorld Latin America 2012 in São Paulo. There are dozens of sessions in seven technology tracks that you won't want to miss. And dozens of interesting, innovative, and exciting sponsors and exhibitors you'll want to be sure to talk to in the Exhibition Hall, not to mention the Oracle demos there that you'll want to experience first-hand. There are three ways to experience Oracle OpenWorld Latin America:  The Oracle OpenWorld conference pass gets you access to all keynotes, sessions, demos, labs, networking events, and more The Oracle OpenWorld and JavaOne conference pass gets you access to all of the above, for BOTH Oracle OpenWorld and JavaOne The Discover pass gets you access to the Exhibition Hall, where you'll be able to see and talk with sponsors and exhibitors, and check out all of the Oracle demos The sooner you sign up the more you save. Savings are greatest between now and 16 November. From 17 November you'll still save significantly over the onsite price if you register before 3 December.  And by the way, the Discover pass comes at no charge if you register by 3 December. So don't wait: Register Now!

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  • Things I've noticed with DVCS

    - by Wes McClure
    Things I encourage: Frequent local commits This way you don't have to be bothered by changes others are making to the central repository while working on a handful of related tasks.  It's a good idea to try to work on one task at a time and commit all changes at partitioned stopping points.  A local commit doesn't have to build, just FYI, so a stopping point doesn't mean a build point nor a point that you can push centrally.  There should be several of these in any given day.  2 hours is a good indicator that you might not be leveraging the power of frequent local commits.  Once you have verified a set of changes works, save them away, otherwise run the risk of introducing bugs into it when working on the next task.  The notion of a task By task I mean a related set of changes that can be completed in a few hours or less.  In the same token don’t make your tasks so small that critically related changes aren’t grouped together.  Use your intuition and the rest of these principles and I think you will find what is comfortable for you. Partial commits Sometimes one task explodes or unknowingly encompasses other tasks, at this point, try to get to a stopping point on part of the work you are doing and commit it so you can get that out of the way to focus on the remainder.  This will often entail committing part of the work and continuing on the rest. Outstanding changes as a guide If you don't commit often it might mean you are not leveraging your version control history to help guide your work.  It's a great way to see what has changed and might be causing problems.  The longer you wait, the more that has changed and the harder it is to test/debug what your changes are doing! This is a reason why I am so picky about my VCS tools on the client side and why I talk a lot about the quality of a diff tool and the ability to integrate that with a simple view of everything that has changed.  This is why I love using TortoiseHg and SmartGit: they show changed files, a diff (or two way diff with SmartGit) of the current selected file and a commit message all in one window that I keep maximized on one monitor at all times. Throw away / stash commits There is extreme value in being able to throw away a commit (or stash it) that is getting out of hand.  If you do not commit often you will have to isolate the work you want to commit from the work you want to throw away, which is wasted productivity and highly prone to errors.  I find myself doing this about once a week, especially when doing exploratory re-factoring.  It's much easier if I can just revert all outstanding changes. Sync with the central repository daily The rest of us depend on your changes.  Don't let them sit on your computer longer than they have to.  Waiting increases the chances of merge conflict which just decreases productivity.  It also prohibits us from doing deploys when people say they are done but have not merged centrally.  This should be done daily!  Find a way to partition the work you are doing so that you can sync at least once daily. Things I discourage: Lots of partial commits right at the end of a series of changes If you notice lots of partial commits at the end of a set of changes, it's likely because you weren't frequently committing, nor were you watching for the size of the task expanding beyond a single commit.  Chances are this cost you productivity if you use your outstanding changes as a guide, since you would have an ever growing list of changes. Committing single files Committing single files means you waited too long and no longer understand all the changes involved.  It may mean there were overlapping changes in single files that cannot be isolated.  In either case, go back to the suggestions above to avoid this.  Committing frequently does not mean committing frequently right at the end of a day's work. It should be spaced out over the course of several tasks, not all at the end in a 5 minute window.

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  • iOS chat application design, sending/relaying the message over to the end user

    - by AyBayBay
    I have a design question. Let us say you were tasked with building a chat application, specifically for iOS (iOS Chat Application). For simplicity let us say you can only chat with one person at a time (no group chat functionality). How then can you achieve sending a message directly to an end user from phone A to phone B? Obviously there is a web service layer with some API calls. One of the API calls available will be startChat(). After starting a chat, when you send a message, you make another async call, let us call it sendMessage() and pass in a string with your message. Once it goes to the web service layer, the message gets stored in a database. Here is where I am currently stuck. After the message gets sent to the web service layer, how do we then achieve sending/relaying the message over to the end user? Should the web server send out a message to the end user and notify them, or should each client call a receiveMessage() method periodically, and if the server side has some info for them it can then respond with that info? Finally, how can we handle the case in which the user you are trying to send a message to is offline? How can we make sure the end user gets the packet when he moves back to an area with signal?

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  • Grading an algorithm: Readability vs. Compactness

    - by amiregelz
    Consider the following question in a test \ interview: Implement the strcpy() function in C: void strcpy(char *destination, char *source); The strcpy function copies the C string pointed by source into the array pointed by destination, including the terminating null character. Assume that the size of the array pointed by destination is long enough to contain the same C string as source, and does not overlap in memory with source. Say you were the tester, how would you grade the following answers to this question? 1) void strcpy(char *destination, char *source) { while (*source != '\0') { *destination = *source; source++; destionation++; } *destionation = *source; } 2) void strcpy(char *destination, char *source) { while (*(destination++) = *(source++)) ; } The first implementation is straightforward - it is readable and programmer-friendly. The second implementation is shorter (one line of code) but less programmer-friendly; it's not so easy to understand the way this code is working, and if you're not familiar with the priorities in this code then it's a problem. I'm wondering if the first answer would show more complexity and more advanced thinking, in the tester's eyes, even though both algorithms behave the same, and although code readability is considered to be more important than code compactness. It seems to me that since making an algorithm this compact is more difficult to implement, it will show a higher level of thinking as an answer in a test. However, it is also possible that a tester would consider the first answer not good because it's not readable. I would also like to mention that this is not specific to this example, but general for code readability vs. compactness when implementing an algorithm, specifically in tests \ interviews.

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  • Data Movement and the Decision Matrix

    - by BuckWoody
    Maybe it’s my military background, or maybe I’ve always had this predilection, but I like to use two devices when I need to make a complex decision: A checklist and a decision matrix. I like to use a checklist because it ensures that I remember the big bits of what I need to do, and brings up questions or areas that I didn’t think about when evaluating options for the decision. And the decision matrix – that’s the thing I use to actually lay out those options. It’s simply a spreadsheet-like grid (I use Excel, but paper and pencil works as well) that lays out the requirements or advantages for the decision across the top, and the options I have on the left-hand side. Then in the “cells” I put whether or not that option on the left will meet the requirement in that column. I then simply “weight” each cell to organize the choices by best-fit. The right answer (or answers) will float right to the top. I was asked yesterday about options for moving data in SQL Server to another system. There are just dozens of ways to do this, from bcp to Replication, each with certain advantages and costs. But asking the questions for the top row first helped me show the person that it isn’t a particular technology that is important, it’s laying out those requirements and thinking about which elements are more important than the other. For instance, is it more important to have the data moved all the time, or is it OK if that happens once in a while? Does the data have to move in two directions or just one? All of these will help that answer jump right out. Try it sometime – it’s a great learning exercise, since it will force you to focus on filling out the matrix. The answer is out there, Neo. Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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  • Should a project start with the client or the server?

    - by MadBurn
    Pretty simple question with a complex answer. Should a project start with the client or the server, and why? Where should a single programmer start a client/server project? What are the best practices and what are the reasons behind them? If you can't think of any, what reasons do you use to justify why you would choose to start one before the other? Personally, I'm asking this question because I'm finishing up specs for a project I will be doing for myself on the side for fun. But now that I'm finishing this phase, I'm wondering "ok, now where do I begin?" Since I've never done a project like this by myself, I'm not sure where I should start. In this project, my server will be doing all the heavy lifting and the client will just be sending updates, getting information from the server, and displaying it. But, I don't want that to sway the answer as I'm looking for more of an in depth and less specific answer that would apply to any project I begin in the future.

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  • DualLayout OpenSourceFood demo site installation instructions

    - by svdoever
    We released DualLayout which enables advanced web design with the power of SharePoint. DualLayout and a demo site can be downloaded from the DualLayout product page. This blogpost contains detailed instructions on installing the demo site. The demo site is based on the site http://opensourcefood.com. The demo site requires internet access because it still links to pages and resources of the real site. Execute the following steps to install the demo site: Copy the OpenSourceFoodDemo.zip file to your SharePoint Server 2010 Make sure that the zip file in “unblocked”, otherwise files are assumed from other computer (right-click on zip file, press “Unblock” button if available) Unzip the OpenSourceFoodDemo.zip to a folder of your choice (c:\OpenSourceFoodDemo) Open the SharePoint  Start->Microsoft SharePoint 2010 Products->SharePoint 2010 Management Shell Change directory to the unzip folder (cd c:\OpenSourceFoodDemo) Start install script: .\InstallDemoSite.ps1 Answer the questions, default values in most cases ok. A little guidance: Question: Give credentials for the account that will be used for the application pool Answer: use for example same account as used for the application pool of your SharePoint site (lookup in IIS Manager) Question: Give credentials for the account that will be used for the application pool Answer: Use same account you are currently logged in with The demo site is made available through a backup and restore. The SharePoint Server 2010 installation must be patched to a level equal or higher to the update level on the SharePoint Server used to create the backup. If you get errors with respect to restore check http://technet.microsoft.com/en-us/sharepoint/ff800847.aspx for downloading the latest cumulative update.

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  • Does immutability entirely eliminate the need for locks in multi-processor programming?

    - by GlenPeterson
    Part 1 Clearly Immutability minimizes the need for locks in multi-processor programming, but does it eliminate that need, or are there instances where immutability alone is not enough? It seems to me that you can only defer processing and encapsulate state so long before most programs have to actually DO something. If a program performs actions on multiple processors, something needs to collect and aggregate the results. All this involves multi-process communication before, after, and possibly during some transformations. The start and end state of the machines are different. Can this always be done with no locks just by throwing out each object and creating a new one instead of changing the original (a crude view of immutability)? What cases still require locking? I'm interested in both the theoretical/academic answer and the practical/real-world answer. I know a lot of functional programmers like to talk about "no side effect" but in the "real world" everything has a side effect. Every processor click takes time and electricity and machine resources away from other processes. So I understand that there may be more than one perspective to answer this question from. If immutability is safe, given certain bounds or assumptions, I want to know what the borders of the "safety zone" are exactly. Some examples of possible boundaries: I/O Exceptions/errors Interfaces with programs written in other languages Interfaces with other machines (physical, virtual, or theoretical) Special thanks to @JimmaHoffa for his comment which started this question! Part 2 Multi-processor programming is often used as an optimization technique - to make some code run faster. When is it faster to use locks vs. immutable objects? Given the limits set out in Amdahl's Law, when can you achieve better over-all performance (with or without the garbage collector taken into account) with immutable objects vs. locking mutable ones? Summary I'm combining these two questions into one to try to get at where the bounding box is for Immutability as a solution to threading problems.

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  • About shared (static) Members and its behavior

    - by Allende
    I just realized that I can access shared members from instances of classes (probably this is not correct, but compile and run), and also learn/discover that, I can modify shared members, then create a new instance and access the new value of the shared member. My question is, what happens to the shared members, when it comes back to the "default" value (class declaration), how dangerous is it do this ? is it totally bad ? is it valid in some cases ?. If you want to test my point here is the code (console project vb.net) that I used to test shared members, as you can see/compile/run, the shared member "x" of the class "Hello" has default value string "Default", but at runtime it changes it, and after creating a new object of that class, this object has the new value of the shared member. Module Module1 Public Class hello Public Shared x As String = "Default" Public Sub New() End Sub End Class Sub Main() Console.WriteLine("hello.x=" & hello.x) Dim obj As New hello() Console.WriteLine("obj.x=" & obj.x) obj.x = "Default shared memeber, modified in object" Console.WriteLine("obj.x=" & obj.x) hello.x = "Defaul shared member, modified in class" Console.WriteLine("hello.x=" & hello.x) Dim obj2 As New hello() Console.WriteLine("obj2.x=" & obj2.x) Console.ReadLine() End Sub End Module UPDATE: First at all, thanks to everyone, each answer give feedback, I suppose, by respect I should choose one as "the answer", I don't want to be offensive to anyone, so please don't take it so bad if I didn't choose you answer.

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  • Numerically stable(ish) method of getting Y-intercept of mouse position?

    - by Fraser
    I'm trying to unproject the mouse position to get the position on the X-Z plane of a ray cast from the mouse. The camera is fully controllable by the user. Right now, the algorithm I'm using is... Unproject the mouse into the camera to get the ray: Vector3 p1 = Vector3.Unproject(new Vector3(x, y, 0), 0, 0, width, height, nearPlane, farPlane, viewProj; Vector3 p2 = Vector3.Unproject(new Vector3(x, y, 1), 0, 0, width, height, nearPlane, farPlane, viewProj); Vector3 dir = p2 - p1; dir.Normalize(); Ray ray = Ray(p1, dir); Then get the Y-intercept by using algebra: float t = -ray.Position.Y / ray.Direction.Y; Vector3 p = ray.Position + t * ray.Direction; The problem is that the projected position is "jumpy". As I make small adjustments to the mouse position, the projected point moves in strange ways. For example, if I move the mouse one pixel up, it will sometimes move the projected position down, but when I move it a second pixel, the project position will jump back to the mouse's location. The projected location is always close to where it should be, but it does not smoothly follow a moving mouse. The problem intensifies as I zoom the camera out. I believe the problem is caused by numeric instability. I can make minor improvements to this by doing some computations at double precision, and possibly abusing the fact that floating point calculations are done at 80-bit precision on x86, however before I start micro-optimizing this and getting deep into how the CLR handles floating point, I was wondering if there's an algorithmic change I can do to improve this? EDIT: A little snooping around in .NET Reflector on SlimDX.dll: public static Vector3 Unproject(Vector3 vector, float x, float y, float width, float height, float minZ, float maxZ, Matrix worldViewProjection) { Vector3 coordinate = new Vector3(); Matrix result = new Matrix(); Matrix.Invert(ref worldViewProjection, out result); coordinate.X = (float) ((((vector.X - x) / ((double) width)) * 2.0) - 1.0); coordinate.Y = (float) -((((vector.Y - y) / ((double) height)) * 2.0) - 1.0); coordinate.Z = (vector.Z - minZ) / (maxZ - minZ); TransformCoordinate(ref coordinate, ref result, out coordinate); return coordinate; } // ... public static void TransformCoordinate(ref Vector3 coordinate, ref Matrix transformation, out Vector3 result) { Vector3 vector; Vector4 vector2 = new Vector4 { X = (((coordinate.Y * transformation.M21) + (coordinate.X * transformation.M11)) + (coordinate.Z * transformation.M31)) + transformation.M41, Y = (((coordinate.Y * transformation.M22) + (coordinate.X * transformation.M12)) + (coordinate.Z * transformation.M32)) + transformation.M42, Z = (((coordinate.Y * transformation.M23) + (coordinate.X * transformation.M13)) + (coordinate.Z * transformation.M33)) + transformation.M43 }; float num = (float) (1.0 / ((((transformation.M24 * coordinate.Y) + (transformation.M14 * coordinate.X)) + (coordinate.Z * transformation.M34)) + transformation.M44)); vector2.W = num; vector.X = vector2.X * num; vector.Y = vector2.Y * num; vector.Z = vector2.Z * num; result = vector; } ...which seems to be a pretty standard method of unprojecting a point from a projection matrix, however this serves to introduce another point of possible instability. Still, I'd like to stick with the SlimDX Unproject routine rather than writing my own unless it's really necessary.

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  • When must I turn my business idea into a formal Company? [closed]

    - by Sony Santos
    I'm a programmer, I have an idea, I know how to implement it, it will be a website, and that site will be my business. My question is very basic: where in timeline must I register my business as an official Company (ie, according Government laws)? Here there are some options to debate or to help answer me: Now - or as soon as I have the idea; When looking for investors (e.g., when a prototype or business plan is ready); When implementing the website; At site's launch; I must launch the website as a personal informal business and, when the business gets success and turns into a more solid and self-running one, only then I must formalize it; It doesn't matter; I can create the company when I want. Nobody talks about that. If I just have an idea, must I run into an office to create a Company? I don't think so. When I'll look for investors, the Company must to pre-exist? Or will the Company be formed with the investor? I'm looking for a generic, country-independent answer, but may the answer for your country can be useful to me. I'm Brazilian, and I believe that the country doesn't matter to this question. (Sorry if this is off-topic, but I coudn't find a batter stackexchange site to ask this.)

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  • Documentation and Test Assertions in Databases

    - by Phil Factor
    When I first worked with Sybase/SQL Server, we thought our databases were impressively large but they were, by today’s standards, pathetically small. We had one script to build the whole database. Every script I ever read was richly annotated; it was more like reading a document. Every table had a comment block, and every line would be commented too. At the end of each routine (e.g. procedure) was a quick integration test, or series of test assertions, to check that nothing in the build was broken. We simply ran the build script, stored in the Version Control System, and it pulled everything together in a logical sequence that not only created the database objects but pulled in the static data. This worked fine at the scale we had. The advantage was that one could, by reading the source code, reach a rapid understanding of how the database worked and how one could interface with it. The problem was that it was a system that meant that only one developer at the time could work on the database. It was very easy for a developer to execute accidentally the entire build script rather than the selected section on which he or she was working, thereby cleansing the database of everyone else’s work-in-progress and data. It soon became the fashion to work at the object level, so that programmers could check out individual views, tables, functions, constraints and rules and work on them independently. It was then that I noticed the trend to generate the source for the VCS retrospectively from the development server. Tables were worst affected. You can, of course, add or delete a table’s columns and constraints retrospectively, which means that the existing source no longer represents the current object. If, after your development work, you generate the source from the live table, then you get no block or line comments, and the source script is sprinkled with silly square-brackets and other confetti, thereby rendering it visually indigestible. Routines, too, were affected. In our system, every routine had a directly attached string of unit-tests. A retro-generated routine has no unit-tests or test assertions. Yes, one can still commit our test code to the VCS but it’s a separate module and teams end up running the whole suite of tests for every individual change, rather than just the tests for that routine, which doesn’t scale for database testing. With Extended properties, one can get the best of both worlds, and even use them to put blame, praise or annotations into your VCS. It requires a lot of work, though, particularly the script to generate the table. The problem is that there are no conventional names beyond ‘MS_Description’ for the special use of extended properties. This makes it difficult to do splendid things such ensuring the integrity of the build by running a suite of tests that are actually stored in extended properties within the database and therefore the VCS. We have lost the readability of database source code over the years, and largely jettisoned the use of test assertions as part of the database build. This is not unexpected in view of the increasing complexity of the structure of databases and number of programmers working on them. There must, surely, be a way of getting them back, but I sometimes wonder if I’m one of very few who miss them.

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  • My Only Gripe With Programming

    - by David Espejo
    Is that im having trouble practicing problems. Even if I decide to practice the problems from my C++ book, they dont give any idea of the way the solution(program) should look like, so that I may compare to see if my program is similar in anyway. My book gives me to many generic "Write a program to do "this" " projects without really showing a concrete example of what "this" really is. In other words How Do I Know That I did "that". One problem in my book said to write a program that calculates the sales tax on a given item????? First of all slase tax differs on state(whats the state,) whats the item(a house, a dog,) How can I check this to see if im right. Programming books dont have answer keys! I know that there is no ABSOLUTE answer, thats just silly, programs can be written in many ways, but a sample of what one would look like based of the difficulty of the problem would really help! Is there a solution to this, maby a book that has worked out examples for the problems they give , or online sources that do something similar.(is there such thing as a programming book with an answer key?)

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  • Session Evaluations

    - by BuckWoody
    I do a lot of public speaking. I write, teach, present and communicate at many levels. I love to do those things. And I love to get better at them. And one of the ways you get better at something is to get feedback on how you did. That being said, I have to confess that I really despise the “evaluations” I get at most venues. From college to technical events to other locations, at Microsoft and points in between, I find these things to be just shy of damaging, and most certainly useless. And it’s not always your fault. Ouch. That seems harsh. But let me ask you one question – and be as honest as you can with the answer – think about it first: “What is the point of a session evaluation?” I’m not saying there isn’t one. In fact, I think there’s a really important reason for them. In my mind, it’s really this: To make the speaker / next session better. Now, if you look at that, you can see right away that most session evals don’t accomplish this goal – not even a little. No, the way that they are worded and the way you (and I) fill them out, it’s more like the implied goal is this: Tell us how you liked this speaker / session. The current ones are for you, not for the speaker or the next person. It’s a popularity contest. Don’t get me wrong. I want to you have a good time. I want you to learn. I want (desperately, oh, please oh please) for you to like me. But in fact, that’s probably not why you went to the session / took the class / read that post. No, you want to learn, and to learn for a particular reason. Remember, I’m talking about college classes, sessions and other class environments here, not a general public event. Most – OK, all – session evaluations make you answer the second goal, not the first. Let’s see how: First, they don’t ask you why you’re there. They don’t ask you if you’re even qualified to evaluate the session or speaker. They don’t ask you how to make it better or keep it great. They use odd numeric scales that are meaningless. For instance, can someone really tell me the difference between a 100-level session and a 200-level one? Between a 400-level and a 500? Is it “internals” (whatever that means) or detail, or length or code, or what? I once heard a great description: A 100-level session makes me say, “wow - I’m smart.” A 500-level session makes me say “wow – that presenter is smart.” And just what is the difference between a 6 and a 7 answer on this question: How well did the speaker know the material? 1  2  3  4  5  6  7  8  9  10 Oh. My. Gosh. How does that make the next session better, or the speaker? And what criteria did you use to answer? And is a “10” better than a “1” (not always clear, and various cultures answer this differently). When it’s all said and done, a speaker basically finds out one thing from the current session evals: “They liked me. They really really liked me.” Or, “Wow. I think I may need to schedule some counseling for the depression I’m about to go into.” You may not think that’s what the speaker hears, but trust me, they do. Those are the only two reactions to the current feedback sheets they get. Either they keep doing what they are doing, or they get their feelings hurt. They just can’t use the information provided to do better. Sorry, but there it is. Keep in mind I do want your feedback. I want to get better. I want you to get your money and time’s worth, probably as much as any speaker alive. But I want those evaluations to be accurate, specific and actionable. I want to know if you had a good time, sure, but I also want to know if I did the right things, and if not, if I can do something different or better. And so, for your consideration, here is the evaluation form I would LOVE for you to use. Feel free to copy it and mail it to me any time. I’m going to put some questions here, and then I’ll even include why they are there. Notice that the form asks you a subjective question right away, and then makes you explain why. That’s work on your part. Notice also that it separates the room and the coffee and the lights and the LiveMeeting from the presenter. So many presenters are faced with circumstances beyond their control, and yet are rated high or low personally on those things. This form helps tease those apart. It’s not numeric. Numbers are easier for the scoring committees but are useless for you and me. So I don’t have any numbers. We’re actually going to have to read these things, not put them in a machine. Hey, if you put in the work to write stuff down, the least we could do is take the time to read it. It’s not anonymous. If you’ve got something to say, say it, and own up to it. People are not “more honest” when they are anonymous, they are less honest. So put your name on it. In fact – this is radical – I posit that these evaluations should be publicly available. Forever. Just like replies to a blog post. Hey, if I’m an organizer, I would LOVE to be able to have access to specific, actionable information on the attendees and the speakers. So if you want mine to be public, go for it. I’ll take the good and the bad. Enjoy. ------------------------------------------------------------------------------------------------------------------------------------------- Session Evaluation – Date, Time, Location, Topic Thanks for giving us your time today. We know that’s valuable, and we hope you learned something you can use from the session. If you can answer these questions as completely as you can, it will help the next person who attends a session here. Your Name: What you do for a living: (We Need your background to evaluate your evaluation) How long you have been doing that: (Again, we need your background to evaluate your evaluation) Paste Session Description Here: (This is what I said I would talk about) Did you like the session?                     No        Meh        Yes (General subjective question – overall “feeling”. You’ll tell us why in a minute.)  Tell us about the venue. Temperature, lights, coffee, or the online sound, performance, anything other than the speaker and the material. (Helps the logistics to be better or as good for the next person) 1. What did you expect to learn in this session? (How did you interpret that extract – did you have expectations that I should work towards for the next person?) 2. Did you learn what you expected to learn? Why? Be very specific. (This is the most important question there is. It tells us how to make the session better for someone like you.) 3. If you were giving this presentation, would you have done anything differently? What? (Helps us to gauge you, the listener, and might give us a great idea on how to do something better. Thanks!) 4. What will you do with the information you got? (Every presenter wants you to learn, and learn something useful. This will help us do that as well or better)  

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  • POLL: How do you build your interfaces in xcode for iphone/coco-touch applications?

    - by LolaRun
    Hi all, It's been 2 months i'm using xcode and building iphone apps, and i'm finding it really hard to grasp the good design for the applications. I always face problems like you can't put your tabbarcontroller in another custom viewcontroller sort of a thing? or other problems... That 'sometimes' - of course - would work if you did the creation of the views/viewcontrollers programmatically. so I don't know if i should start writing the creation of my objects or use interface builder. This is why i'm asking this poll question, to see what's the most accepted way among other developers. I'm not going to answer my question, so the votes would not increase my reputation and risk my poll being closed soon. I prefer that the first two readers of this question should answer by 'using IB' and the second one 'programmatically' and the rest would vote up or down for these two answers. And don't vote my question either, i just need to know, and maybe someone else wants to know. so the longer this question lives the better. and gaining nothing from it concerning reputation would help that cause. thank you all for your cooperation. and go ahead and answer Peace

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  • How do I simplify a 2D game grid for level management while keeping its by-pixel features?

    - by Eric Thoma
    (I cross-posted this from StackOverflow as this seems to be a more appropriate forum. I've looked around a little here and I did not find an answer, so I hope this is not a recurring question.) This is a question dealing with 2D world design. I am playing around by creating a 2D bird's eye view shooter game, and I am looking to make the game sleek and advanced. I hope to be able to write physics so projectiles have momentum and knock-down properties. I am immediately running into the problem of world design. I need a way to have level files that store everything there is about a game. This is easiest by just having a grid of objects. But there are thin-walls and other objects that don't seem to fit into a traditional cell of a grid. I want to be able to fit all these together so I can streamline level design; so I don't have to put in the exact pixel-specific start and end of a wall. There doesn't seem to be an obvious translation from level file to game without forcing myself into a pacman-life scenario, meaning a scenario where the game feels boxy and discrete. There is a contrast between the smoothly (relatively) moving characters and finite jumps in a grid. I would appreciate an answer that would describe implementation options or point me to resources that do. I would also appreciate references to sites that teach game design. The language I am using is Java (although I would love to use C or C++, but I can never find convenient resources in those languages). Thank you for any answers. Please leave any questions in the space below; I will be able to answer them later tonight (28th Nov).

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