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• A bit confused about OOP and PHP.

  - by Pirkka

  Hello I have programmed with procedural style a lot before and in these few months I have decided to go OOP. Im a bit confused about OOP and PHP. Lets say I have Categories table and Pages table in my database. I would like to do a page-class and a category-class. Lets say I would have a page that showed information about the category and there would be a list of pages that belong to the category. How would I implement that in OOP way? I have thought that the category class would have a property (array) that would contain all the pages that it has. Well then comes the part that I`m confused about. Should I have a method that would get all the pages with correct categoryID from the database and should I instantiate all the rows as an Page-object? Or should I have a setPages-method in the Category-class and getAllPages-method in the Pages-class and with that method I would set all the pages to the Category-class. Huh Im lost. :D

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• How to declare a 2D array of 2D array pointers and access them?

  - by vikramtheone

  Hi Guys, How can I declare an 2D array of 2D Pointers? And later access the individual array elements of the 2D arrays. Is my approach correct? void alloc_2D(int ***memory, unsigned int rows, unsigned int cols); int main() { int i, j; int **ptr; int **array[10][10]; for(i=0;i<10;i++) { for(j=0;j<10;j++) { alloc_2D(&ptr, 10, 10); array[i][j] = ptr; } } //After I do this, how can I access the 10 individual 2D arrays? return 0; } void alloc_2D(int ***memory, unsigned int rows, unsigned int cols) { int **ptr; *memory = NULL; ptr = malloc(rows * sizeof(int*)); if(ptr == NULL) { printf("\nERROR: Memory allocation failed!"); } else { int i; for(i = 0; i< rows; i++) { ptr[i] = malloc(cols * sizeof(float)); if(ptr[i]==NULL) { printf("\nERROR: Memory allocation failed!"); } } } *memory = ptr; }

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• Noob - Cycle through stored names and skip blanks

  - by ActiveJimBob

  NOOB trying to make my code more efficient. On scroll button push, the function 'SetName' stores a number to integer 'iName' which is index against 5 names stored in memory. If a name is not set in memeory, it skips to the next. The code works, but takes up a lot of room. Any advice appreciated. Code: #include <string.h> int iName = 0; int iNewName = 0; BYTE GetName () { return iName; } void SetName (int iNewName) { while (iName != iNewName) { switch (byNewName) { case 1: if (strlen (memory.m_nameA) == 0) new_name++; else iName = iNewName; break; case 2: if (strlen (memory.m_nameB) == 0) new_name++; else iName = iNewName; break; case 3: if (strlen (memory.m_nameC) == 0) new_name++; else iName = iNewName; break; case 4: if (strlen (memory.m_nameD) == 0) new_name++; else iName = iNewName; break; case 5: if (strlen (memory.m_nameE) == 0) new_name++; else iName = iNewName; break; default: iNewName = 1; break; } // end of case } // end of loop } // end of SetName function void main () { while(1) { if (Button_pushed) SetName(GetName+1); } // end of infinite loop } // end of main

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• How can I limit asp.net control actions based on user role?

  - by Duke

  I have several pages or views in my application which are essentially the same for both authenticated users and anonymous users. I'd like to limit the insert/update/delete actions in formviews and gridviews to authenticated users only, and allow read access for both authed and anon users. I'm using the asp.net configuration system for handling authentication and roles. This system limits access based on path so I've been creating duplicate pages for authed and anon paths. The solution that comes to mind immediately is to check roles in the appropriate event handlers, limiting what possible actions are displayed (insert/update/delete buttons) and also limiting what actions are performed (for users that may know how to perform an action in the absence of a button.) However, this solution doesn't eliminate duplication - I'd be duplicating security code on a series of pages rather than duplicating pages and limiting access based on path; the latter would be significantly less complicated. I could always build some controls that offered role-based configuration, but I don't think I have time for that kind of commitment right now. Is there a relatively easy way to do this (do such controls exist?) or should I just stick to path-based access and duplicate pages? Does it even make sense to use two methods of authorization? There are still some pages which are strictly for either role so I'll be making use of path-based authorization anyway. Finally, would using something other than path-based authorization be contrary to typical asp.net design practices, at least in the context of using the asp.net configuration system?

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• Recommendations for IPC between parent and child processes in .NET?

  - by Jeremy

  My .NET program needs to run an algorithm that makes heavy use of 3rd party libraries (32-bit), most of which are unmanaged code. I want to drive the CPU as hard as I can, so the code runs several threads in parallel to divide up the work. I find that running all these threads simultaneously results in temporary memory spikes, causing the process' virtual memory size to approach the 2 GB limit. This memory is released back pretty quickly, but occasionally if enough threads enter the wrong sections of code at once, the process crosses the "red line" and either the unmanaged code or the .NET code encounters an out of memory error. I can throttle back the number of threads but then my CPU usage is not as high as I would like. I am thinking of creating worker processes rather than worker threads to help avoid the out of memory errors, since doing so would give each thread of execution its own 2 GB of virtual address space (my box has lots of RAM). I am wondering what are the best/easiest methods to communicate the input and output between the processes in .NET? The file system is an obvious choice. I am used to shared memory, named pipes, and such from my UNIX background. Is there a Windows or .NET specific mechanism I should use?

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• PHP While loop seperating unique categories from multiple 'Joined' tables

  - by Hob

  I'm pretty new to Joins so hope this all makes sense. I'm joining 4 tables and want to create a while loop that spits out results nested under different categories. My Tables categories id | category_name pages id | page_name | category *page_content* id | page_id | image_id images id | thumb_path My current SQL join <?php $all_photos = mysql_query(" SELECT * FROM categories JOIN pages ON pages.category = categories.id JOIN image_pages ON image_pages.page_id = pages.id JOIN images ON images.id = image_pages.image_id ");?> The result I want from a while loop I would like to get something like this.... Category 1 page 1 Image 1, image 2, image 3 page 2 Image 2, image 4 Category 2 page 3 image 1 page 4 image 1, image 2, image 3 I hope that makes sense. Each image can fall under multiple pages and each page can fall under multiple categories. at the moment I have 2 solutions, one which lists each category several times according to the the amount of pages inside them: eg. category 1, page 1, image 1 - category 1, page 1, image 2 etc One that uses a while loop inside another while loop inside another while loop, resulting in 3 sql queries. <?php while($all_page = mysql_fetch_array($all_pages)) { ?> <p><?=$all_page['page_name']?></p> <?php $all_images = mysql_query("SELECT * FROM images JOIN image_pages ON image_pages.page_id = " . $all_page['id'] . " AND image_pages.image_id = images.id"); ?> <div class="admin-images-block clearfix"> <?php while($all_image = mysql_fetch_array($all_images)) { ?> <img src="<?=$all_image['thumb_path']?>" alt="<?=$all_image['title']?>"/> <?php } ?> </div> <?php } } ?

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• Reading and writing in parallel

  - by Malfist

  I want to be able to read and write a large file in parallel, or if not in parallel, at least in blocks so that I don't use up so much memory. This is my current code: // Define memory stream which will be used to hold encrypted data. MemoryStream memoryStream = new MemoryStream(); // Define cryptographic stream (always use Write mode for encryption). CryptoStream cryptoStream = new CryptoStream(memoryStream, encryptor, CryptoStreamMode.Write); //start encrypting using (BinaryReader reader = new BinaryReader(File.Open(fileIn, FileMode.Open))) { byte[] buffer = new byte[1024 * 1024]; int read = 0; do { read = reader.Read(buffer, 0, buffer.Length); cryptoStream.Write(buffer, 0, read); } while (read == buffer.Length); } // Finish encrypting. cryptoStream.FlushFinalBlock(); // Convert our encrypted data from a memory stream into a byte array. //byte[] cipherTextBytes = memoryStream.ToArray(); //write our memory stream to a file memoryStream.Position = 0; using (BinaryWriter writer = new BinaryWriter(File.Open(fileOut, FileMode.Create))) { byte[] buffer = new byte[1024 * 1024]; int read = 0; do { read = memoryStream.Read(buffer, 0, buffer.Length); writer.Write(buffer, 0, read); } while (read == buffer.Length); } // Close both streams. memoryStream.Close(); cryptoStream.Close(); As you can see, it reads the entire file into memory, encrypts it, then writes it out. If I happen to be encrypting files that are very large (2GB+) it tends not to work, or at the very least, consumes ~97% of my memory. How could I do it in a more effective manner?

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• unbuffered I/O in Linux

  - by stuck

  I'm writing lots and lots of data that will not be read again for weeks - as my program runs the amount of free memory on the machine (displayed with 'free' or 'top') drops very quickly, the amount of memory my app uses does not increase - neither does the amount of memory used by other processes. This leads me to believe the memory is being consumed by the filesystems cache - since I do not intend to read this data for a long time I'm hoping to bypass the systems buffers, such that my data is written directly to disk. I dont have dreams of improving perf or being a super ninja, my hope is to give a hint to the filesystem that I'm not going to be coming back for this memory any time soon, so dont spend time optimizing for those cases. On Windows I've faced similar problems and fixed the problem using FILE_FLAG_NO_BUFFERING|FILE_FLAG_WRITE_THROUGH - the machines memory was not consumed by my app and the machine was more usable in general. I'm hoping to duplicate the improvements I've seen but on Linux. On Windows there is the restriction of writing in sector sized pieces, I'm happy with this restriction for the amount of gain I've measured. is there a similar way to do this in Linux?

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• SEO Problem for new dictionary site, google hasn't indexed content.

  - by John

  I loaded about 15,000 pages, letters A & B of a dictionary and submitted to google a text site map. I'm using google's search with advertisement as the planned mechanism to go through my site. Google's webmaster accepted the site mapps as good but then did not index. My index page has been indexed by google and at this point have not linked to any pages. So to get google's search to work I need to get all my content indexed. It appears google will not just index from the site map and so I was thinking of adding pages that spider in links from the main index page. But I don't want to create a bunch of pages that programicly link all of the pages without knowing if this has a chance to work. Eventually I plan on having about 150,000 pages each page being a word or phrase being defined. I wrote a program that is pulling this from a dictionary database. I would like to prove the content that I have to anyone interested to show the value of the dictionary in releation to the dictionary software that I'm completing. Suggestions for getting the entire site indexed by google so I can appear in the search results? Thanks

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• PHP & MySQL Pagination Update Help

  - by TaG

  Its been a while since I updated my pagination on my web page and I'm trying to add First and Last Links to my pagination as well as the ... when the search results are to long. For example I'm trying to achieve the following in the example below. Can some one help me fix my code so I can update my site. Thanks Previous First 1 2 3 4 5 6 7 ... 199 200 Last Next I currently have the following displayed using my code. Previous 1 2 3 4 5 6 7 Next Here is the part of my pagination code that displays the links. if ($pages > 1) { echo '<br /><p>'; $current_page = ($start/$display) + 1; if ($current_page != 1) { echo '<a href="index.php?s=' . ($start - $display) . '&p=' . $pages . '">Previous</a> '; } for ($i = 1; $i <= $pages; $i++) { if ($i != $current_page) { echo '<a href="index.php?s=' . (($display * ($i - 1))) . '&p=' . $pages . '">' . $i . '</a> '; } else { echo '<span>' . $i . '</span> '; } } if ($current_page != $pages) { echo '<a href="index.php?s=' . ($start + $display) . '&p=' . $pages . '">Next</a>'; } echo '</p>'; }

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• Printing an Image embedded into an asp.net page. C#

  - by user1683846

  I am looking to print using C#, micorsoft visual studio, asp.net. The goal:- I am trying to print all pages in a fax document. Format:- The fax document is received as a single .tiff file with multiple pages. What needs to be done:- I need to iterate each page in the .tiff image and print them all. // This function will iterate all pages, one at a time. // protected void PrintAll_Click(object sender, EventArgs e) { // counts number of pages in the fax document.// int number = _FaxPages.Count; // for loop to iterate through each page. // for (int i = 0; i < number; i++) { string _FaxId = Page.Request["FaxId"]; _PageIndex = i; imgFax.ImageUrl = "ShowFax.ashx?n=" + _FaxId + "&f=" + _PageIndex + "&mw=750"; PrintAll.Attributes.Add("onclick", "return printing()"); } } and In my Java script I have: function printing() { window.print(); } Now the issues are: <1 The function only prints one page (the very last page of the tiff file)....and it prints the entire window and not just the embedded .tiff image in the entire web browser window. Any Ideas of how to go about just printing the .tiff embedded image instead of the entire web browser window. <2 Although my for loop iterates through the pages. The print function is only called after the loop has iterated through all the pages and stopped on the final page (say page 6/6). And then it only prints that last page (along with the rest of the contents on the browser window). This is not what I want to happen... I dont want to print all the excess material on the browser window such as buttons, links etc... I just want the embedded .tiff image from the browser window.

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• Single-entry implementation gone wrong

  - by user745434

  I'm doing my first single-entry site and based on the result, I can't see the benefit. I've implemented the following: .htaccess redirects all requests to index.php at the root Url is parsed and each /segment/ is stored as an element in an array First segment indicates which folder to include (e.g. "users" » "/pages/users/index.php"). index.php file of each folder parses the remaining elements in the segments array until array is empty. content.php file of each folder is included if there are no more elements in the segments array, indicating that the destination file is reached Sample File structure ( folders in [] ): [root] index.php [pages] [users] index.php content.php [profile] index.php content.php [edit] index.php content.php [other-page] index.php content.php Request: http://mysite.com/users/profile/ .htaccess redirects request to http://mysite.com/index.php URL is parsed and segments array contains: [1] users, [2] profile index.php maps [1] to "pages/users/index.php", so includes that file pages/users/index.php maps [2] to pages/users/profile/index.php, so includes that file Since no other elements in the segments array, the contents.php file in the current folder (pages/users/profile) is included. I'm not really seeing the benefit of doing this over having functions that include components of the site (e.g. include_header(), include_footer(), etc.), so I conclude that I'm doing something terribly wrong. I'm just not sure what it is.

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• What are some ways to accomplish a dynamic array?

  - by Ted

  I'm going to start working on a new game and one of the things I'd like to accomplish is a dynamic array sort of system that would hold map data. The game will be top-down 2d and made with XNA 4.0 and C#. You will begin in a randomized area which will essentially be tile based. As such a 2 dimensional array would be one way to accomplish this by holding numerical values which would correspond to a list of textures and that would be how it would draw this randomly created map. The problem is I would kind of only like to create the area around where you start and they could venture in which ever direction they wanted to. This would mean I'd have to populate the map array with more randomized data in the direction they go. I could make a really large array and use the center of it and the rest would be in anticipation of new content to be made, but that just seems very inefficient. I suppose when they start a new game I could have a one time map creation process that would go through and create a large randomly generated map array, but holding all of in memory at all times seems also inefficient. Perhaps if there was a way that I'd only hold parts of that map data in memory at one time and somehow not hold the rest in memory. In the end I only need to have a chunk of the map somewhat close to them in memory so perhaps some of you might have suggestions on good ways to approach this kind of randomized map and dynamic array problem. It wouldn't need to be a dynamic array type of thing if I made it so that it pulled in map data nearby that is needed and then once off the screen and not needed it could somehow get rid of that memory that way I wouldn't have a huge array taking up a bunch of memory.

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• C#: System.Lazy&lt;T&gt; and the Singleton Design Pattern

  - by James Michael Hare

  So we've all coded a Singleton at one time or another.  It's a really simple pattern and can be a slightly more elegant alternative to global variables.  Make no mistake, Singletons can be abused and are often over-used -- but occasionally you find a Singleton is the most elegant solution. For those of you not familiar with a Singleton, the basic Design Pattern is that a Singleton class is one where there is only ever one instance of the class created.  This means that constructors must be private to avoid users creating their own instances, and a static property (or method in languages without properties) is defined that returns a single static instance. 1: public class Singleton 2: { 3: // the single instance is defined in a static field 4: private static readonly Singleton _instance = new Singleton(); 5:  6: // constructor private so users can't instantiate on their own 7: private Singleton() 8: { 9: } 10:  11: // read-only property that returns the static field 12: public static Singleton Instance 13: { 14: get 15: { 16: return _instance; 17: } 18: } 19: } This is the most basic singleton, notice the key features: Static readonly field that contains the one and only instance. Constructor is private so it can only be called by the class itself. Static property that returns the single instance. Looks like it satisfies, right?  There's just one (potential) problem.  C# gives you no guarantee of when the static field _instance will be created.  This is because the C# standard simply states that classes (which are marked in the IL as BeforeFieldInit) can have their static fields initialized any time before the field is accessed.  This means that they may be initialized on first use, they may be initialized at some other time before, you can't be sure when. So what if you want to guarantee your instance is truly lazy.  That is, that it is only created on first call to Instance?  Well, there's a few ways to do this.  First we'll show the old ways, and then talk about how .Net 4.0's new System.Lazy<T> type can help make the lazy-Singleton cleaner. Obviously, we could take on the lazy construction ourselves, but being that our Singleton may be accessed by many different threads, we'd need to lock it down. 1: public class LazySingleton1 2: { 3: // lock for thread-safety laziness 4: private static readonly object _mutex = new object(); 5:  6: // static field to hold single instance 7: private static LazySingleton1 _instance = null; 8:  9: // property that does some locking and then creates on first call 10: public static LazySingleton1 Instance 11: { 12: get 13: { 14: if (_instance == null) 15: { 16: lock (_mutex) 17: { 18: if (_instance == null) 19: { 20: _instance = new LazySingleton1(); 21: } 22: } 23: } 24:  25: return _instance; 26: } 27: } 28:  29: private LazySingleton1() 30: { 31: } 32: } This is a standard double-check algorithm so that you don't lock if the instance has already been created.  However, because it's possible two threads can go through the first if at the same time the first time back in, you need to check again after the lock is acquired to avoid creating two instances. Pretty straightforward, but ugly as all heck.  Well, you could also take advantage of the C# standard's BeforeFieldInit and define your class with a static constructor.  It need not have a body, just the presence of the static constructor will remove the BeforeFieldInit attribute on the class and guarantee that no fields are initialized until the first static field, property, or method is called.   1: public class LazySingleton2 2: { 3: // because of the static constructor, this won't get created until first use 4: private static readonly LazySingleton2 _instance = new LazySingleton2(); 5:  6: // Returns the singleton instance using lazy-instantiation 7: public static LazySingleton2 Instance 8: { 9: get { return _instance; } 10: } 11:  12: // private to prevent direct instantiation 13: private LazySingleton2() 14: { 15: } 16:  17: // removes BeforeFieldInit on class so static fields not 18: // initialized before they are used 19: static LazySingleton2() 20: { 21: } 22: } Now, while this works perfectly, I hate it.  Why?  Because it's relying on a non-obvious trick of the IL to guarantee laziness.  Just looking at this code, you'd have no idea that it's doing what it's doing.  Worse yet, you may decide that the empty static constructor serves no purpose and delete it (which removes your lazy guarantee).  Worse-worse yet, they may alter the rules around BeforeFieldInit in the future which could change this. So, what do I propose instead?  .Net 4.0 adds the System.Lazy type which guarantees thread-safe lazy-construction.  Using System.Lazy<T>, we get: 1: public class LazySingleton3 2: { 3: // static holder for instance, need to use lambda to construct since constructor private 4: private static readonly Lazy<LazySingleton3> _instance 5: = new Lazy<LazySingleton3>(() => new LazySingleton3()); 6:  7: // private to prevent direct instantiation. 8: private LazySingleton3() 9: { 10: } 11:  12: // accessor for instance 13: public static LazySingleton3 Instance 14: { 15: get 16: { 17: return _instance.Value; 18: } 19: } 20: } Note, you need your lambda to call the private constructor as Lazy's default constructor can only call public constructors of the type passed in (which we can't have by definition of a Singleton).  But, because the lambda is defined inside our type, it has access to the private members so it's perfect. Note how the Lazy<T> makes it obvious what you're doing (lazy construction), instead of relying on an IL generation side-effect.  This way, it's more maintainable.  Lazy<T> has many other uses as well, obviously, but I really love how elegant and readable it makes the lazy Singleton.

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• An increase to 3 Gig of RAM slows down Ubuntu 10.04 LTS

  - by williepabon

  I have Ubuntu 10.04 running from an external hard drive (installed on an enclosure) connected via USB port. Like a month or so ago, I increased RAM on my pc from 2 Gigs to 3 Gigs. This resulted on extremely long boot times and slow application loads. While I was understanding the nature of my problem, I posted various threads on this forum ( Questions # 188417, 188801), where I was advised to gather speed tests, and other info on my machine. I was also suggested that I might have problems with the RAM installed. Initially, I did not consider that possibility because: 1) I did a memory test with a diagnostic program from DELL (My pc is from Dell) 2) My pc works fine with Windows XP (the default OS), no problems with memory 3) My pc works fine when booting with Ubuntu 10.10 memory stick, no speed problems 4) My pc works fine when booting with Ubuntu 11.10 memory stick, no speed problems Anyway, I performed the memory tests suggested. But before doing it, and to check out any possibility of hardware issues on the hard drive, I did the following: (1) purchased a new hard drive enclosure and moved my hard drive to it, (2) purchased a new USB cable and used it to connect my hard drive/enclosure setup to a different USB port on my pc. Then, I performed speed tests with 1 Gig, 2 Gigs and 3 Gigs of RAM with my Ubuntu 10.04 OS. Ubuntu 10.04 worked well when booted with 1 Gig or 2 Gigs of RAM. When I increased to 3 Gigs, it slowed down to a crawl. I can't understand the relationship between an increase of 1 Gig and the effect it has in Ubuntu 10.04. This doesn't happen with Ubuntu 10.10 and 11.10. Unfortunately for me, Ubuntu 10.04 is my principal work operating system. So, I need a solution for this. Hardware and system information: DELL Precision 670 2 internal SATA Hard drives Audigy 2 ZS audio system Factory OS: Windows XP Professional SP3 NVidia 8400 GTS video card More info: williepabon@WP-WrkStation:~$ uname -a Linux WP-WrkStation 2.6.32-38-generic #83-Ubuntu SMP Wed Jan 4 11:13:04 UTC 2012 i686 GNU/Linux williepabon@WP-WrkStation:~$ lsb_release -a No LSB modules are available. Distributor ID: Ubuntu Description: Ubuntu 10.04.4 LTS Release: 10.04 Codename: lucid Speed test with the 3 Gigs of RAM installed: williepabon@WP-WrkStation:~$ sudo hdparm -tT /dev/sdc [sudo] password for williepabon: /dev/sdc: Timing cached reads: 84 MB in 2.00 seconds = 41.96 MB/sec Timing buffered disk reads: 4 MB in 3.81 seconds = 1.05 MB/sec This is a very slow transfer rate from a hard drive. I will really appreciate a solution or a work around for this problem. I know that that there are users that have Ubuntu 10.04 with 3 Gigs or more of RAM and they don't have this problem. Same question asked on Launchpad for reference.

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• The Sitemap Paradox

  - by Jeff Atwood

  We use a sitemap on Stack Overflow, but I have mixed feelings about it. Web crawlers usually discover pages from links within the site and from other sites. Sitemaps supplement this data to allow crawlers that support Sitemaps to pick up all URLs in the Sitemap and learn about those URLs using the associated metadata. Using the Sitemap protocol does not guarantee that web pages are included in search engines, but provides hints for web crawlers to do a better job of crawling your site. Based on our two years' experience with sitemaps, there's something fundamentally paradoxical about the sitemap: Sitemaps are intended for sites that are hard to crawl properly. If Google can't successfully crawl your site to find a link, but is able to find it in the sitemap it gives the sitemap link no weight and will not index it! That's the sitemap paradox -- if your site isn't being properly crawled (for whatever reason), using a sitemap will not help you! Google goes out of their way to make no sitemap guarantees: "We cannot make any predictions or guarantees about when or if your URLs will be crawled or added to our index" citation "We don't guarantee that we'll crawl or index all of your URLs. For example, we won't crawl or index image URLs contained in your Sitemap." citation "submitting a Sitemap doesn't guarantee that all pages of your site will be crawled or included in our search results" citation Given that links found in sitemaps are merely recommendations, whereas links found on your own website proper are considered canonical ... it seems the only logical thing to do is avoid having a sitemap and make damn sure that Google and any other search engine can properly spider your site using the plain old standard web pages everyone else sees. By the time you have done that, and are getting spidered nice and thoroughly so Google can see that your own site links to these pages, and would be willing to crawl the links -- uh, why do we need a sitemap, again? The sitemap can be actively harmful, because it distracts you from ensuring that search engine spiders are able to successfully crawl your whole site. "Oh, it doesn't matter if the crawler can see it, we'll just slap those links in the sitemap!" Reality is quite the opposite in our experience. That seems more than a little ironic considering sitemaps were intended for sites that have a very deep collection of links or complex UI that may be hard to spider. In our experience, the sitemap does not help, because if Google can't find the link on your site proper, it won't index it from the sitemap anyway. We've seen this proven time and time again with Stack Overflow questions. Am I wrong? Do sitemaps make sense, and we're somehow just using them incorrectly?

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• Getting Internet Explorer to Open Different Sets of Tabs Based on the Day of the Week

  - by Akemi Iwaya

  If you have to use Internet Explorer for work and need to open a different set of work-specific tabs every day, is there a quick and easy way to do it instead of opening each one individually? Today’s Question & Answer session comes to us courtesy of SuperUser—a subdivision of Stack Exchange, a community-driven grouping of Q&A web sites. The Question SuperUser reader bobSmith1432 is looking for a quick and easy way to open different daily sets of tabs in Internet Explorer for his work: When I open Internet Explorer on different days of the week, I want different tabs to be opened automatically. I have to run different reports for work each day of the week and it takes a lot of time to open the 5-10 tabs I use to run the reports. It would be a lot faster if, when I open Internet Explorer, the tabs I needed would automatically load and be ready. Is there a way to open 5-10 different tabs in Internet Explorer depending on the day of the week? Example: Monday – 6 Accounting Pages Tuesday – 7 Billing Pages Wednesday – 5 HR Pages Thursday – 10 Schedule Pages Friday – 8 Work Summary/Order Pages Is there an easier way for Bob to get all those tabs to load and be ready to go each day instead of opening them individually every time? The Answer SuperUser contributor Julian Knight has a simple, non-script solution for us: Rather than trying the brute force method, how about a work around? Open up each set of tabs either in different windows, or one set at a time, and save all tabs to bookmark folders. Put the folders on the bookmark toolbar for ease of access. Each day, right-click on the appropriate folder and click on ‘Open in tab group’ to open all the tabs. You could put all the day folders into a top-level folder to save space if you want, but at the expense of an extra click to get to them. If you really must go further, you need to write a program or script to drive Internet Explorer. The easiest way is probably writing a PowerShell script. Special Note: There are various scripts shared on the discussion page as well, so the solution shown above is just one possibility out of many. If you love the idea of using scripts for a function like this, then make sure to browse on over to the discussion page to see the various ones SuperUser members have shared! Have something to add to the explanation? Sound off in the comments. Want to read more answers from other tech-savvy Stack Exchange users? Check out the full discussion thread here.

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• How does I/O work for large graph databases?

  - by tjb1982

  I should preface this by saying that I'm mostly a front end web developer, trained as a musician, but over the past few years I've been getting more and more into computer science. So one idea I have as a fun toy project to learn about data structures and C programming was to design and implement my own very simple database that would manage an adjacency list of posts. I don't want SQL (maybe I'll do my own query language? I'm just having fun). It should support ACID. It should be capable of storing 1TB let's say. So with that, I was trying to think of how a database even stores data, without regard to data structures necessarily. I'm working on linux, and I've read that in that world "everything is a file," including hardware (like /dev/*), so I think that that obviously has to apply to a database, too, and it clearly does--whether it's MySQL or PostgreSQL or Neo4j, the database itself is a collection of files you can see in the filesystem. That said, there would come a point in scale where loading the entire database into primary memory just wouldn't work, so it doesn't make sense to design it with that mindset (I assume). However, reading from secondary memory would be much slower and regardless some portion of the database has to be in primary memory in order for you to be able to do anything with it. I read this post: Why use a database instead of just saving your data to disk? And I found it difficult to understand how other databases, like SQLite or Neo4j, read and write from secondary memory and are still very fast (faster, it would seem, than simply writing files to the filesystem as the above question suggests). It seems the key is indexing. But even indexes need to be stored in secondary memory. They are inherently smaller than the database itself, but indexes in a very large database might be prohibitively large, too. So my question is how is I/O generally done with large databases like the one I described above that would be at least 1TB storing a big adjacency list? If indexing is more or less the answer, how exactly does indexing work--what data structures should be involved?

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• Breadcrumb using and schema.org rich snippets

  - by Adam Jenkin

  I am having problems implementing the breadcrumb rich snippets from schema.org. When I construct my breadcrumb using the documentation and run via Google Rich Snippet testing tool, the breadcrumb is identified but not shown in the preview. <!DOCTYPE html> <html> <head> <title>My Test Page</title> </head> <body itemscope itemtype="http://schema.org/WebPage"> <strong>You are here: </strong> <div itemprop="breadcrumb"> <a title="Home" href="/">Home</a> > <a title="Test Pages" href="/Test-Pages/">Test Pages</a> > </div> </body> </html> If I change to use the snippets from data-vocabulary.org, the rich snippets show correctly in the preview. <!DOCTYPE html> <html> <head> <title>My Test Page</title> </head> <body> <strong>You are here: </strong> <ol itemprop="breadcrumb"> <li itemscope itemtype="http://data-vocabulary.org/Breadcrumb"> <a href="/" itemprop="url"> <span itemprop="title">Home</span> </a> </li> <li itemscope itemtype="http://data-vocabulary.org/Breadcrumb"> <a href="/Test-Pages/" itemprop="url"> <span itemprop="title">Test Pages</span> </a> </li> </ol> </body> </html> I want the breadcrumb to be shown in the search result rather than the url to the page. Given that schema.org is the recommended way to be using rich snippets, I would rather use this, however as the breadcrumb is not showing in the preview of the search result using this method, i'm not convinced this is working correctly. Am I doing something wrong in the markup for schema.org example?

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• Subterranean IL: Volatile

  - by Simon Cooper

  This time, we'll be having a look at the volatile. prefix instruction, and one of the differences between volatile in IL and C#. The volatile. prefix volatile is a tricky one, as there's varying levels of documentation on it. From what I can see, it has two effects: It prevents caching of the load or store value; rather than reading or writing to a cached version of the memory location (say, the processor register or cache), it forces the value to be loaded or stored at the 'actual' memory location, so it is then immediately visible to other threads. It forces a memory barrier at the prefixed instruction. This ensures instructions don't get re-ordered around the volatile instruction. This is slightly more complicated than it first seems, and only seems to matter on certain architectures. For more details, Joe Duffy has a blog post going into the details. For this post, I'll be concentrating on the first aspect of volatile. Caching field accesses To demonstrate this, I created a simple multithreaded IL program. It boils down to the following code: .class public Holder { .field public static class Holder holder .field public bool stop .method public static specialname void .cctor() { newobj instance void Holder::.ctor() stsfld class Holder Holder::holder ret }}.method private static void Main() { .entrypoint // Thread t = new Thread(new ThreadStart(DoWork)) // t.Start() // Thread.Sleep(2000) // Console.WriteLine("Stopping thread...") ldsfld class Holder Holder::holder ldc.i4.1 stfld bool Holder::stop call instance void [mscorlib]System.Threading.Thread::Join() ret}.method private static void DoWork() { ldsfld class Holder Holder::holder // while (!Holder.holder.stop) {} DoWork: dup ldfld bool Holder::stop brfalse DoWork pop ret} If you compile and run this code, you'll find that the call to Thread.Join() never returns - the DoWork spinlock is reading a cached version of Holder.stop, which is never being updated with the new value set by the Main method. Adding volatile to the ldfld fixes this: dupvolatile.ldfld bool Holder::stopbrfalse DoWork The volatile ldfld forces the field access to read direct from heap memory, which is then updated by the main thread, rather than using a cached copy. volatile in C# This highlights one of the differences between IL and C#. In IL, volatile only applies to the prefixed instruction, whereas in C#, volatile is specified on a field to indicate that all accesses to that field should be volatile (interestingly, there's no mention of the 'no caching' aspect of volatile in the C# spec; it only focuses on the memory barrier aspect). Furthermore, this information needs to be stored within the assembly somehow, as such a field might be accessed directly from outside the assembly, but there's no concept of a 'volatile field' in IL! How this information is stored with the field will be the subject of my next post.

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• Map and fill texture using PBO (OpenGL 3.3)

  - by NtscCobalt

  I'm learning OpenGL 3.3 trying to do the following (as it is done in D3D)... Create Texture of Width, Height, Pixel Format Map texture memory Loop write pixels Unmap texture memory Set Texture Render Right now though it renders as if the entire texture is black. I can't find a reliable source for information on how to do this though. Almost every tutorial I've found just uses glTexSubImage2D and passes a pointer to memory. Here is basically what my code does... (In this case it is generating an 1-byte Alpha Only texture but it is rendering it as the red channel for debugging) GLuint pixelBufferID; glGenBuffers(1, &pixelBufferID); glBindBuffer(GL_PIXEL_UNPACK_BUFFER, pixelBufferID); glBufferData(GL_PIXEL_UNPACK_BUFFER, 512 * 512 * 1, nullptr, GL_STREAM_DRAW); glBindBuffer(GL_PIXEL_UNPACK_BUFFER, 0); GLuint textureID; glGenTextures(1, &textureID); glBindTexture(GL_TEXTURE_2D, textureID); glTexImage2D(GL_TEXTURE_2D, 0, GL_R8, 512, 512, 0, GL_RED, GL_UNSIGNED_BYTE, nullptr); glBindTexture(GL_TEXTURE_2D, 0); glBindTexture(GL_TEXTURE_2D, textureID); glBindBuffer(GL_PIXEL_UNPACK_BUFFER, pixelBufferID); void *Memory = glMapBuffer(GL_PIXEL_UNPACK_BUFFER, GL_WRITE_ONLY); // Memory copied here, I know this is valid because it is the same loop as in my working D3D version glUnmapBuffer(GL_PIXEL_UNPACK_BUFFER); glBindBuffer(GL_PIXEL_UNPACK_BUFFER, 0); And then here is the render loop. // This chunk left in for completeness glUseProgram(glProgramId); glBindVertexArray(glVertexArrayId); glBindBuffer(GL_ARRAY_BUFFER, glVertexBufferId); glEnableVertexAttribArray(0); glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 20, 0); glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 20, 12); GLuint transformLocationID = glGetUniformLocation(3, 'transform'); glUniformMatrix4fv(transformLocationID , 1, true, somematrix) // Not sure if this is all I need to do glBindTexture(GL_TEXTURE_2D, pTex->glTextureId); GLuint textureLocationID = glGetUniformLocation(glProgramId, "texture"); glUniform1i(textureLocationID, 0); glDrawArrays(GL_TRIANGLES, Offset*3, Triangles*3); Vertex Shader #version 330 core in vec3 Position; in vec2 TexCoords; out vec2 TexOut; uniform mat4 transform; void main() { TexOut = TexCoords; gl_Position = vec4(Position, 1.0) * transform; } Pixel Shader #version 330 core uniform sampler2D texture; in vec2 TexCoords; out vec4 fragColor; void main() { // Output color fragColor.r = texture2D(texture, TexCoords).r; fragColor.g = 0.0f; fragColor.b = 0.0f; fragColor.a = 1.0; }

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• ecommerce item deleted by user, 301 rediret to HOME PAGE or 404 not found?

  - by Marco Demaio

  I know this question is someway similar to this one where they reccomend using 404, but after reading this other one where they suggest to use 301 when changing site urls (in the specific case was due to redesign/refactoring) I get a bit of confused and I hope someone could clarify for this specific example: Let's say I have an ecommerce site, let's also say the final user inserted some interesting items in the site and the ecommerce webapp created the item pages at the urls: http://...?id=20, http://...?id=30 etc. Now let's say some of these interesting items got many external links toward them from many other sites because some people found those items very interesting and linked to them. After some years the final user deletes those items, so obviously the pages/urls http://...?id=20, http://...?id=30, etc. now do not exist anymore, but still many pages on the web are linking toward them. What should the ecommerce site do now, just show a 404 page for those items? But, I'm confused, wouldn't this loose all the Google PR passed by the external links to the items pages? So isn't it better to use 301 redirect to HOME PAGE that at least passes the PR to the HOME PAGE? Thanks, EDIT: Well, according to answeres the best thing to do so far is to do a 404/410. In order to make this question more complete, I would like to talk about a special case, just to make sure I understood. properly. Let's say the user creates those items again (the ones he previously deleted at point 4), maybe he changes a bit their names and description, but they are basically the same items. The webapp has no way to know these new added items were the old items so it obviously create them as new items with new urls http://...?id=100, http://...?id=101, does it makes sense at this point to redirect 301 the old urls to the new ones? MORE EDIT (It would be VERY IMPORTANT TO UNDERSTAND): Well according to the clever answers received so far it seems for the special case, explained in my last EDIT, I could use 301, since it's something of not deceptive cause basically the new pages is a replacement for the old page in term of contents. This is basically done to keep the PR passed from external link and also for better user experience. But beside the user experince, that is discussible (*1), in order to preserve PR from external broken linlks why not just always use 301, In my understanding Google dislikes duplicated contents, but are we sure that 301 redirect to HOME PAGE is seen as duplicated contents for Google?! Google itself suggests to redircet 301 index.html to document root so if they consider 301 as duplicated contents wouldn't that be considered duplicated contents too?! Why do they suggest it? Let me provoke you: “why not just add a 301 to HOME PAGE for every not found page?” (*1) as a user, when I follo a broken url from some external link to some website's page I would stick more on this website if I get redirected to HOME PAGE rather than seeing a 404 page where I would think the webiste does not even exist anymore and maybe I don't even try to go to HOME PAGE of the website.

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• Website File and Folder Structure

  - by Drummss

  I am having a problem learning how proper website structure should be. And by that I mean how to code the pages and how folder structure should be. Currently I am navigating around my website using GET variables in PHP when you want go to another page, so I am always loading the index.php file. And I would load the page I wanted like so: $page = "error"; if(isset($_GET["page"]) AND file_exists("pages/".$_GET["page"].".php")) { $page = $_GET["page"]; } elseif(!isset($_GET["page"])) { $page = "home"; } And this: <div id="page"> <?php include("pages/".$page.".php"); ?> </div> The reason I am doing this is because it makes making new pages a lot easier as I don't have to link style sheets and javascript in every file like so: <head> <title> Website Name </title> <link href='http://fonts.googleapis.com/css?family=Lato:300,400' rel='stylesheet' type='text/css'> <link rel="stylesheet" href="css/style.css" type="text/css"> <link rel="shortcut icon" href="favicon.png"/> <script src="//ajax.googleapis.com/ajax/libs/jquery/1.11.0/jquery.min.js" type="text/javascript"></script> <script src="//ajax.googleapis.com/ajax/libs/jqueryui/1.10.4/jquery-ui.min.js" type="text/javascript"></script> </head> There is a lot of problems doing it this way as URLs don't look normal ("?page=apanel/app") if I am trying to access a page from inside a folder inside the pages folder to prevent clutter. Obviously this is not the only way to go about it and I can't find the proper way to do it because I'm sure websites don't link style sheets in every file as that would be very bad if you changed a file name or needed to add another file you would have to change it in every file. If anyone could tell me how it is actually done or point me towards a tutorial that would be great. Thanks for your time :)

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• Plagued by multithreaded bugs

  - by koncurrency

  On my new team that I manage, the majority of our code is platform, TCP socket, and http networking code. All C++. Most of it originated from other developers that have left the team. The current developers on the team are very smart, but mostly junior in terms of experience. Our biggest problem: multi-threaded concurrency bugs. Most of our class libraries are written to be asynchronous by use of some thread pool classes. Methods on the class libraries often enqueue long running taks onto the thread pool from one thread and then the callback methods of that class get invoked on a different thread. As a result, we have a lot of edge case bugs involving incorrect threading assumptions. This results in subtle bugs that go beyond just having critical sections and locks to guard against concurrency issues. What makes these problems even harder is that the attempts to fix are often incorrect. Some mistakes I've observed the team attempting (or within the legacy code itself) includes something like the following: Common mistake #1 - Fixing concurrency issue by just put a lock around the shared data, but forgetting about what happens when methods don't get called in an expected order. Here's a very simple example: void Foo::OnHttpRequestComplete(statuscode status) { m_pBar->DoSomethingImportant(status); } void Foo::Shutdown() { m_pBar->Cleanup(); delete m_pBar; m_pBar=nullptr; } So now we have a bug in which Shutdown could get called while OnHttpNetworkRequestComplete is occuring on. A tester finds the bug, captures the crash dump, and assigns the bug to a developer. He in turn fixes the bug like this. void Foo::OnHttpRequestComplete(statuscode status) { AutoLock lock(m_cs); m_pBar->DoSomethingImportant(status); } void Foo::Shutdown() { AutoLock lock(m_cs); m_pBar->Cleanup(); delete m_pBar; m_pBar=nullptr; } The above fix looks good until you realize there's an even more subtle edge case. What happens if Shutdown gets called before OnHttpRequestComplete gets called back? The real world examples my team has are even more complex, and the edge cases are even harder to spot during the code review process. Common Mistake #2 - fixing deadlock issues by blindly exiting the lock, wait for the other thread to finish, then re-enter the lock - but without handling the case that the object just got updated by the other thread! Common Mistake #3 - Even though the objects are reference counted, the shutdown sequence "releases" it's pointer. But forgets to wait for the thread that is still running to release it's instance. As such, components are shutdown cleanly, then spurious or late callbacks are invoked on an object in an state not expecting any more calls. There are other edge cases, but the bottom line is this: Multithreaded programming is just plain hard, even for smart people. As I catch these mistakes, I spend time discussing the errors with each developer on developing a more appropriate fix. But I suspect they are often confused on how to solve each issue because of the enormous amount of legacy code that the "right" fix will involve touching. We're going to be shipping soon, and I'm sure the patches we're applying will hold for the upcoming release. Afterwards, we're going to have some time to improve the code base and refactor where needed. We won't have time to just re-write everything. And the majority of the code isn't all that bad. But I'm looking to refactor code such that threading issues can be avoided altogether. One approach I am considering is this. For each significant platform feature, have a dedicated single thread where all events and network callbacks get marshalled onto. Similar to COM apartment threading in Windows with use of a message loop. Long blocking operations could still get dispatched to a work pool thread, but the completion callback is invoked on on the component's thread. Components could possibly even share the same thread. Then all the class libraries running inside the thread can be written under the assumption of a single threaded world. Before I go down that path, I am also very interested if there are other standard techniques or design patterns for dealing with multithreaded issues. And I have to emphasize - something beyond a book that describes the basics of mutexes and semaphores. What do you think? I am also interested in any other approaches to take towards a refactoring process. Including any of the following: Literature or papers on design patterns around threads. Something beyond an introduction to mutexes and semaphores. We don't need massive parallelism either, just ways to design an object model so as to handle asynchronous events from other threads correctly. Ways to diagram the threading of various components, so that it will be easy to study and evolve solutions for. (That is, a UML equivalent for discussing threads across objects and classes) Educating your development team on the issues with multithreaded code. What would you do?

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• deadlocks in the innodb status

  - by shantanuo

  Mysql sever has suddenly become very slow. There are no queries in the slow query log but the innodb status shows something like the following. Does it mean that it is due to innodb deadlock? if Yes, what is the way out? *************************** 1. row *************************** Status: ===================================== 100315 12:55:29 INNODB MONITOR OUTPUT ===================================== Per second averages calculated from the last 5 seconds ---------- SEMAPHORES ---------- OS WAIT ARRAY INFO: reservation count 187532, signal count 188120 Mutex spin waits 0, rounds 61908654, OS waits 33052 RW-shared spins 89241, OS waits 41948; RW-excl spins 5857, OS waits 1557 ------------------------ LATEST DETECTED DEADLOCK ------------------------ 100315 12:43:02 *** (1) TRANSACTION: TRANSACTION 0 56996536, ACTIVE 0 sec, process no 5000, OS thread id 3031395216 starting index read mysql tables in use 1, locked 1 LOCK WAIT 6 lock struct(s), heap size 1024, undo log entries 6 MySQL thread id 994, query id 7699751 localhost application Searching rows for update UPDATE QUERY *** (1) WAITING FOR THIS LOCK TO BE GRANTED: RECORD LOCKS space id 0 page no 4073 n bits 296 index `PRIMARY` of table `dbII/tbl_ticket_block_master` trx id 0 56996536 lock_mode X locks r ec but not gap waiting Record lock, heap no 141 PHYSICAL RECORD: n_fields 23; compact format; info bits 0 0: len 7; hex 33353837393936; asc 3587996;; 1: len 4; hex 800001f4; asc ;; 2: len 1; hex 47; asc G;; 3: len 2; hex 6f6b; asc ok;; 4: le n 6; hex 0000035957fe; asc YW ;; 5: len 7; hex 000000401737c0; asc @ 7 ;; 6: SQL NULL; 7: SQL NULL; 8: SQL NULL; 9: len 3; hex 8fb46e; asc n;; 10: SQL NULL; 11: len 1; hex 30; asc 0;; 12: len 0; hex ; asc ;; 13: SQL NULL; 14: len 1; hex 33; asc 3;; 15: len 4; hex 4b9ceebe ; asc K ;; 16: len 1; hex 30; asc 0;; 17: len 4; hex 80006ae8; asc j ;; 18: len 0; hex ; asc ;; 19: len 0; hex ; asc ;; 20: len 0; hex ; asc ;; 21: len 0; hex ; asc ;; 22: len 0; hex ; asc ;; *** (2) TRANSACTION: TRANSACTION 0 56996527, ACTIVE 0 sec, process no 5000, OS thread id 2961476496 fetching rows, thread declared inside InnoDB 237 mysql tables in use 3, locked 3 121 lock struct(s), heap size 11584, undo log entries 16 MySQL thread id 995, query id 7699729 localhost application Searching rows for update UPDATE QUERY *** (2) HOLDS THE LOCK(S): RECORD LOCKS space id 0 page no 4073 n bits 296 index `PRIMARY` of table `DBII/tbl_ticket_block_master` trx id 0 56996527 lock_mode X Record lock, heap no 1 PHYSICAL RECORD: n_fields 1; compact format; info bits 0 0: len 8; hex 73757072656d756d; asc supremum;; Record lock, heap no 2 PHYSICAL RECORD: n_fields 23; compact format; info bits 0 0: len 7; hex 33353837343631; asc 3587461;; 1: len 4; hex 800001f4; asc ;; 2: len 1; hex 47; asc G;; 3: len 6; hex 497373756564; asc Is sued;; 4: len 6; hex 000003425295; asc BR ;; 5: len 7; hex 8000000464012c; asc d ,;; 6: SQL NULL; 7: len 4; hex 80000058; asc X;; 8: len 1; hex 43; asc C;; 9: len 3; hex 8fb465; asc e;; 10: len 3; hex 8fb46d; asc m;; 11: len 1; hex 30; asc 0;; 12: len 0; hex ; asc ; ; 13: SQL NULL; 14: len 1; hex 33; asc 3;; 15: len 4; hex 4b9b33a2; asc K 3 ;; 16: len 3; hex 756d67; asc umg;; 17: len 4; hex 80006744; asc gD;; 18: len 0; hex ; asc ;; 19: len 0; hex ; asc ;; 20: len 0; hex ; asc ;; 21: len 0; hex ; asc ;; 22: len 0; hex ; asc ;;

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