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  • Is there a way to prevent Maven Test from rebuilding the database?

    - by Christopher W. Allen-Poole
    I've recently been asked to, effectively, sell my department on unit testing. I can't tell you how excited this makes me, but I do have one concern. We're using JUnit with Spring and Maven, and this means that each time mvn test is called, it rebuilds the database. Obviously, we can't integrate that with our production server -- it would kill valuable data. How do I prevent the rebuilding without telling maven to skip testing? The best I could figure was to assign the script to operate in a test database (line breaks added for readability): mvn test -Ddbunit.schema=<database>test -Djdbc.url=jdbc:mysql://localhost/<database>test? createDatabaseIfNotExist=true&amp; useUnicode=true&amp;characterEncoding=utf-8 I can't help but think there must be a better way. I'm especially interested in learning if there is an easy way to tell Maven to only run tests on particular classes without building anything else? mvn -Dtest=<test-name> test still rebuilds the database. ======= update ======= Bit of egg on my face here. I didn't realize that I was using the same variable in two places, meaning that the POM was using a "skip.test" variable for both rebuilding the database and for running the tests...

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  • Insert MANY key value pairs fast into berkeley db with hash access

    - by Kungi
    Hi, i'm trying to build a hash with berkeley db, which shall contain many tuples (approx 18GB of key value pairs), but in all my tests the performance of the insert operations degrades drastically over time. I've written this script to test the performance: #include<iostream> #include<db_cxx.h> #include<ctime> #define MILLION 1000000 int main () { long long a = 0; long long b = 0; int passes = 0; int i = 0; u_int32_t flags = DB_CREATE; Db* dbp = new Db(NULL,0); dbp->set_cachesize( 0, 1024 * 1024 * 1024, 1 ); int ret = dbp->open( NULL, "test.db", NULL, DB_HASH, flags, 0); time_t time1 = time(NULL); while ( passes < 100 ) { while( i < MILLION ) { Dbt key( &a, sizeof(long long) ); Dbt data( &b, sizeof(long long) ); dbp->put( NULL, &key, &data, 0); a++; b++; i++; } DbEnv* dbep = dbp->get_env(); int tmp; dbep->memp_trickle( 50, &tmp ); i=0; passes++; std::cout << "Inserted one million --> pass: " << passes << " took: " << time(NULL) - time1 << "sec" << std::endl; time1 = time(NULL); } } Perhaps you can tell me why after some time the "put" operation takes increasingly longer and maybe how to fix this. Thanks for your help, Andreas

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  • Writing a JavaScript zip code validation function

    - by mkoryak
    I would like to write a JavaScript function that validates a zip code, by checking if the zip code actually exists. Here is a list of all zip codes: http://www.census.gov/tiger/tms/gazetteer/zips.txt (I only care about the 2nd column) This is really a compression problem. I would like to do this for fun. OK, now that's out of the way, here is a list of optimizations over a straight hashtable that I can think of, feel free to add anything I have not thought of: Break zipcode into 2 parts, first 2 digits and last 3 digits. Make a giant if-else statement first checking the first 2 digits, then checking ranges within the last 3 digits. Or, covert the zips into hex, and see if I can do the same thing using smaller groups. Find out if within the range of all valid zip codes there are more valid zip codes vs invalid zip codes. Write the above code targeting the smaller group. Break up the hash into separate files, and load them via Ajax as user types in the zipcode. So perhaps break into 2 parts, first for first 2 digits, second for last 3. Lastly, I plan to generate the JavaScript files using another program, not by hand. Edit: performance matters here. I do want to use this, if it doesn't suck. Performance of the JavaScript code execution + download time. Edit 2: JavaScript only solutions please. I don't have access to the application server, plus, that would make this into a whole other problem =)

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  • Perl Regex - Condensing groups of find/replace

    - by brydgesk
    I'm using Perl to perform some file cleansing, and am running into some performance issues. One of the major parts of my code involves standardizing name fields. I have several sections that look like this: sub substitute_titles { my ($inStr) = @_; ${$inStr} =~ s/ PHD./ PHD /; ${$inStr} =~ s/ P H D / PHD /; ${$inStr} =~ s/ PROF./ PROF /; ${$inStr} =~ s/ P R O F / PROF /; ${$inStr} =~ s/ DR./ DR /; ${$inStr} =~ s/ D.R./ DR /; ${$inStr} =~ s/ HON./ HON /; ${$inStr} =~ s/ H O N / HON /; ${$inStr} =~ s/ MR./ MR /; ${$inStr} =~ s/ MRS./ MRS /; ${$inStr} =~ s/ M R S / MRS /; ${$inStr} =~ s/ MS./ MS /; ${$inStr} =~ s/ MISS./ MISS /; } I'm passing by reference to try and get at least a little speed, but I fear that running so many (literally hundreds) of specific string replaces on tens of thousands (likely hundreds of thousands eventually) of records is going to hurt the performance. Is there a better way to implement this kind of logic than what I'm doing currently? Thanks Edit: Quick note, not all the replace functions are just removing periods and spaces. There are string deletions, soundex groups, etc.

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  • Better way of looping to detect change.

    - by Dremation
    As of now I'm using a while(true) method to detect changes in memory. The problem with this is it's kill the applications performance. I have a list of 30 pointers that need checked as rapidly as possible for changes, without sacrificing a huge performance loss. Anyone have ideas on this? memScan = new Thread(ScanMem); public static void ScanMem() { int i = addy.Length; while (true) { Thread.Sleep(30000); //I do this to cut down on cpu usage for (int j = 0; j < i; j++) { string[] values = addy[j].Split(new char[] { Convert.ToChar(",") }); //MessageBox.Show(values[2]); try { if (Memory.Scanner.getIntFromMem(hwnd, (IntPtr)Convert.ToInt32(values[0], 16), 32).ToString() != values[1].ToString()) { //Ok, it changed lets do our work //work if (Globals.Working) return; SomeFunction("Results: " + values[2].ToString(), "Memory"); Globals.Working = true; }//end if }//end try catch { } }//end for }//end while }//end void

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  • Is there a good digraph layout library callable from C++?

    - by Steve314
    The digraphs represent finite automata. Up until now my test program has been writing out dot files for testing. This is pretty good both for regression testing (keep the verified output files in subversion, ask it if there has been a change) and for visualisation. However, there are some problems... Basically, I want something callable from C++ and which plans a layout for my states and transitions but leaves the drawing to me - something that will allow me to draw things however I want and draw on GUI (wxWidgets) windows. I also want a license which will allow commercial use - I don't need that at present, and I may very well release as open source, but I don't want to limit my options ATM. The problems with GraphViz are (1) the warnings about building from source on Windows, (2) all the unnecessary dependencies for rendering and parsing, and (3) the (presumed) lack of a documented API specifically and purely for layout. Basically, I want to be able to specify my states (with bounding rectangle sizes) and transitions, and read out positions for the states and waypoints for each transition, then draw based on those co-ordinates myself. I haven't really figured out how annotations on transitions should be handled, but there should be some kind of provision for specifying bounding-box-sizes for those, associating them with transitions, and reading out positions. Does anyone know of a library that can handle those requirements? I'm not necessarily against implementing something for myself, but in this case I'd rather avoid it if possible.

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  • Referencing object's identity before submitting changes in LINQ

    - by Axarydax
    Hi, is there a way of knowing ID of identity column of record inserted via InsertOnSubmit beforehand, e.g. before calling datasource's SubmitChanges? Imagine I'm populating some kind of hierarchy in the database, but I wouldn't want to submit changes on each recursive call of each child node (e.g. if I had Directories table and Files table and am recreating my filesystem structure in the database). I'd like to do it that way, so I create a Directory object, set its name and attributes, then InsertOnSubmit it into DataContext.Directories collection, then reference Directory.ID in its child Files. Currently I need to call InsertOnSubmit to insert the 'directory' into the database and the database mapping fills its ID column. But this creates a lot of transactions and accesses to database and I imagine that if I did this inserting in a batch, the performance would be better. What I'd like to do is to somehow use Directory.ID before commiting changes, create all my File and Directory objects in advance and then do a big submit that puts all stuff into database. I'm also open to solving this problem via a stored procedure, I assume the performance would be even better if all operations would be done directly in the database.

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  • Naive Bayes matlab, row classification

    - by Jungle Boogie
    How do you classify a row of seperate cells in matlab? Atm I can classify single coloums like so: training = [1;0;-1;-2;4;0;1]; % this is the sample data. target_class = ['posi';'zero';'negi';'negi';'posi';'zero';'posi']; % target_class are the different target classes for the training data; here 'positive' and 'negetive' are the two classes for the given training data % Training and Testing the classifier (between positive and negative) test = 10*randn(25, 1); % this is for testing. I am generating random numbers. class = classify(test,training, target_class, 'diaglinear') % This command classifies the test data depening on the given training data using a Naive Bayes classifier Unlike the above im looking at wanting to classify: A B C Row A | 1 | 1 | 1 = a house Row B | 1 | 2 | 1 = a garden Can anyone help? Here is a code example from matlabs site: nb = NaiveBayes.fit(training, class) nb = NaiveBayes.fit(..., 'param1',val1, 'param2',val2, ...) I dont understand what param1 is or what val1 etc should be?

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  • Rails' page caching vs. HTTP reverse proxy caches

    - by John Topley
    I've been catching up with the Scaling Rails screencasts. In episode 11 which covers advanced HTTP caching (using reverse proxy caches such as Varnish and Squid etc.), they recommend only considering using a reverse proxy cache once you've already exhausted the possibilities of page, action and fragment caching within your Rails application (as well as memcached etc. but that's not relevant to this question). What I can't quite understand is how using an HTTP reverse proxy cache can provide a performance boost for an application that already uses page caching. To simplify matters, let's assume that I'm talking about a single host here. This is my understanding of how both techniques work (maybe I'm wrong): With page caching the Rails process is hit initially and then generates a static HTML file that is served directly by the Web server for subsequent requests, for as long as the cache for that request is valid. If the cache has expired then Rails is hit again and the static file is regenerated with the updated content ready for the next request With an HTTP reverse proxy cache the Rails process is hit when the proxy needs to determine whether the content is stale or not. This is done using various HTTP headers such as ETag, Last-Modified etc. If the content is fresh then Rails responds to the proxy with an HTTP 304 Not Modified and the proxy serves its cached content to the browser, or even better, responds with its own HTTP 304. If the content is stale then Rails serves the updated content to the proxy which caches it and then serves it to the browser If my understanding is correct, then doesn't page caching result in less hits to the Rails process? There isn't all that back and forth to determine if the content is stale, meaning better performance than reverse proxy caching. Why might you use both techniques in conjunction?

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  • Should I persist images on EBS or S3?

    - by javanes
    I am migrating my Java,Tomcat, Mysql server to AWS EC2. I have already attached EBS volume for storing MySql data. In my web application people may upload images. So I should persist them. There are 2 alternatives in my mind: Save uploaded images to EBS volume. Use the S3 service. The followings are my notes, please be skeptic about them, as my expertise is not on servers, but software development. EBS plus: S3 storage is more expensive. (0.15 $/Gb 0.1$/Gb) S3 plus: Serving statics from EBS may influence my web server's performance negatively. Is this true? Does Serving images affect server performance notably? For S3 my server will not be responsible for serving statics. S3 plus: Serving statics from EBS may result I/O cost, probably it will be minor. EBS plus: People say EBS is faster. S3 plus: People say S3 is more safe for persistence. EBS plus: No need to learn API, it is straight forward to save the images to EBS volume. Namely I can not decide, will be happy if you guide. Thanks

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  • How do I ensure my C# software can access the internet in a Citrix + ISA environment?

    - by TomFromThePool
    Hi everyone, A client recently informed us that deployment of our software in their environment has failed due to a proxy error when the software attempts to access the internet. The client has a combination of Citrix and Microsoft's ISA server. The software allows the use of a proxy and the ability to manually enter authentication information, or automatically retrieve the current system proxy settings. The error returned is the standard 407 authentication error, but the client assures us that they have entered the authentication information required. They have also shown us the snippet of the ISA error logs which identify the client as Anonymous and the authentication protocol as Basic. I have a few questions I suppose: How should I go about dealing with the ISA server in my code? I have no real experience with this environment and am assuming that the ISA server is treated like any other proxy. If I am mistaken, what should I be doing? Does ISA allow the administrator to disallow specific authentication protocols - and if this is the case and 'Basic' auth is disallowed, would it still return a 407 error? Could the Citrix environment have caused this issue? Is there any particular way to ensure that my software will work in such an environment? Code-samples would be much appreciated. I have neither a Citrix test server or an ISA server at my disposal to carry out testing on this so I am currently trying to identify possible causes before I make the case for investment in a more robust testing environment. Thanks for any help!

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  • Does complex JOINs causes high coupling and maintenance problems ?

    - by ashkan.kh.nazary
    Our project has ~40 tables with complex relations.A colleague believes in using long join queries which enforces me to learn about tables outside of my module but I think I should not concern about tables not directly related to my module and use data access functions (written by those responsible for other modules) when I need data from them. Let me clarify: I am responsible for the ContactVendor module which enables the customers to contact the vendor and start a conversation about some specific product. Products module has it's own complex tables and relations with functions that encapsulate details (for example i18n, activation, product availability etc ...). Now I need to show the product title of some product related to some conversation between the vendor and customers. I may either write a long query that retrieves the product info along with conversation stuff in one shot (which enforces me to learn about Product tables) OR I may pass the relevant product_id to the get_product_info(int) function. First approach is obviously demanding and introduces many bad practices and things I normally consider fault in programming. The problem with the second approach seems to be the countless mini queries these access functions cause and performance loss is a concern when a loop tries to fetch product titles for 100 products using functions that each perform a separate query. So I'm stuck between "don't code to the implementation, code to interface" and performance. What is the right way of doing things ? UPDATE: I'm specially concerned about possible future modifications to those tables outside of my module. What if the Products module decided to change the way they are doing things? or for some reason modify the schema? It means some other modules would break or malfunction until the change is integrated to them. The usual ripple effect problem.

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  • Where in maven project's path should I put configuration files that are not considered resources

    - by Paralife
    I have a simple java maven project. One of my classes when executing needs to load an xml configuration file from the classpath. I dont want to package such xml file when producing the jar but I want to include a default xml file in a zip assemply under a conf subfolder and I also want this default xml to be available in the unit tests to test against it. As I see it there are 2 possible places of this default xml: src/main/resources/conf/default.xml src/main/conf/default.xml Both solutions demand special pom actions: In solution 1, I get the auto copy to target folder during build which means it is available in testing but I also get it in the produced jar which i dont want. In solution 2, I get the jar as I want it(free of the xml) but I manually have to copy the xml to the target folder to be available for testing. (I dont want to add src's subfolders in test classpath. I think it is bad practice). The question is what is the best solution of the two? If the correct is 2, what is the best way to copy it to target folder? Is there any other solution better and more common than those two? (I also read http://stackoverflow.com/questions/465001/where-should-i-put-application-configuration-files-for-a-maven-project but I would like to know the most "correct solution" from the "convention over configuration" point of view and this link provides some configuration type solutions but not any convention oriented. Maybe there isnt one but I ask anyway. Also the solutions provided include AntRun plugin and appAssembler plugin and I wonder if I could do it with out them.)

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  • Compiling gstreamer plugin in windows

    - by utnapistim
    Hello all, My question: What is the correct way to compile a gstreamer plugin in windows, so that it will be accepted by gstreamer (actually Songbird on top of gstreamer). My setup: I have downloaded the songbird sources following the steps described here and I have a trunk/dependencies/windows-i686-msvc8 directory within my svn sources with all the gstreamer binaries. I have created a gstreamer empty plugin skeleton following the steps detailed in the GStreamer Plugin Writer's Guide, and compiled it against the gstreamer binaries in the Songbird dependencies folder. The compilation was done with VS2010 RC1 (Visual Studio 2008 yelded the same results), using an empty DLL project with the .h and .c files generated using the GStreamer Plugin Writer's Guide. The DLL was lined with libcpmt.lib, libcmt.lib, ws2_32.lib, gobject-2.0.lib, gthread-2.0.lib, gstreamer-0.10-0.lib, glib-2.0.lib, kernel32.lib, nspr4.lib and ignoring all default libraries. I have compiled the files as both .c and .cpp with the same results. Testing: I have installed the Songbird binaries corresponding to the correct svn version, then installed Songbird Developer Tools addon and used it to create an addon for testing my gstreamer plugin. Songbird will not load the pluggin. I have also tried to load it with gst-launch.exe from the trunk/dependencies/windows-i686-msvc8/[...] directory and that generated runtime error R6034: An application has made an attempt to load the C runtime library incorrectly. Most resources I found for this problem recommended restarting or reinstalling windows :(.

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  • Microsoft products such as Visual Studio 2010 does not require to enter serial number

    - by MainMa
    Hi, I am member of WebsiteSpark and was member of DreamSpark. Both programs enable to download software and provide serial keys to use. Some software like Windows Server has an ISO file to download and a serial number displayed on the website which I must enter during installation. Some other software does not have any serial key. For example, when I downloaded Visual Studio 2010, there was just a link to an ISO file. During installation, there was no such a field as serial number (whereas Visual Studio 2008 had this field at the beginning of installation process). There is the same thing with SQL Server 2008 and Microsoft Expression Studio 3. Even when I've downloaded the public trial RTM version of Windows Seven Enterprise, there were no serial number to enter. I don't think that such expensive products as SQL Server 2008 Enterprise are delivered without serials and online validation, so I suppose that the serial is embedded into the product itself, either in installation binaries or in a separate config file, so is already in the ISO I download so I do not have to enter it. So my question is, how it is done technically? Is each 2 GBs ISO generated on-demand on the server to embed a serial each time this ISO is requested? I suppose that if it is done, it has a huge impact on servers performance (no caching, no streaming...), so what may be the techniques used behind? I want to implement the same feature in a product I intend to ship (to simplify installation by avoiding to ask to enter serial number), but I really don't see how to do it with low impact on server performance.

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  • Why slim reader/writer exclusive lock outperformance the shared one?

    - by Jichao
    I have tested the performance of slim reader/writer lock under windows 7 using the codefrom Windows Via C/C++. The result surprised me that the exclusive lock out performance the shared one. Here are the code and the result. unsigned int __stdcall slim_reader_writer_exclusive(void *arg) { //SRWLOCK srwLock; //InitializeSRWLock(&srwLock); for (int i = 0; i < 1000000; ++i) { AcquireSRWLockExclusive(&srwLock); g_value = 0; ReleaseSRWLockExclusive(&srwLock); } _endthreadex(0); return 0; } unsigned int __stdcall slim_reader_writer_shared(void *arg) { int b; for (int i = 0; i < 1000000; ++i) { AcquireSRWLockShared(&srwLock); //b = g_value; g_value = 0; ReleaseSRWLockShared(&srwLock); } _endthreadex(0); return 0; } g_value is a global int volatile variable. Could you kindly explain why this could happen?

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  • Groovy / Scala / Java under the hood

    - by Jack
    I used Java for like 6-7 years, then some months ago I discovered Groovy and started to save a lot of typing.. then I wondered how certain things worked under the hood (because groovy performance is really poor) and understood that to give you dynamic typing every Groovy object is a MetaClass object that handles all the things that the JVM couldn't handle by itself. Of course this introduces a layer in the middle between what you write and what you execute that slows down everything. Then somedays ago I started getting some infos about Scala. How these two languages compare in their byte code translations? How much things they add to the normal structure that it would be obtained by plain Java code? I mean, Scala is static typed so wrapper of Java classes should be lighter, since many things are checked during compile time but I'm not sure about the real differences of what's going inside. (I'm not talking about the functional aspect of Scala compared to the other ones, that's a different thing) Can someone enlighten me? From WizardOfOdds it seems like that the only way to get less typing and same performance would be to write an intermediate translator that translates something in Java code (letting javac compile it) without alterating how things are executed, just adding synctatic sugar withour caring about other fallbacks of the language itself.

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  • Is this a good job description? What title would you give this position?

    - by Zack Peterson
    Department: Information Technology Reports To: Chief Information Officer Purpose: Company's ________________ is specifically engaged in the development of World Wide Web applications and distributed network applications. This person is concerned with all facets of the software development process and specializes in software product management. He or she contributes to projects in an application architect role and also performs individual programming tasks. Essential Duties & Responsibilities: This person is involved in all aspects of the software development process such as: Participation in software product definitions, including requirements analysis and specification Development and refinement of simulations or prototypes to confirm requirements Feasibility and cost-benefit analysis, including the choice of architecture and framework Application and database design Implementation (e.g. installation, configuration, customization, integration, data migration) Authoring of documentation needed by users and partners Testing, including defining/supporting acceptance testing and gathering feedback from pre-release testers Participation in software release and post-release activities, including support for product launch evangelism (e.g. developing demonstrations and/or samples) and subsequent product build/release cycles Maintenance Qualifications: Bachelor's degree in computer science or software engineering Several years of professional programming experience Proficiency in the general technology of the World Wide Web: Hypertext Transfer Protocol (HTTP) Hypertext Markup Language (HTML) JavaScript Cascading Style Sheets (CSS) Proficiency in the following principles, practices, and techniques: Accessibility Interoperability Usability Security (especially prevention of SQL injection and cross-site scripting (XSS) attacks) Object-oriented programming (e.g. encapsulation, inheritance, modularity, polymorphism, etc.) Relational database design (e.g. normalization, orthogonality) Search engine optimization (SEO) Asynchronous JavaScript and XML (AJAX) Proficiency in the following specific technologies utilized by Company: C# or Visual Basic .NET ADO.NET (including ADO.NET Entity Framework) ASP.NET (including ASP.NET MVC Framework) Windows Presentation Foundation (WPF) Language Integrated Query (LINQ) Extensible Application Markup Language (XAML) jQuery Transact-SQL (T-SQL) Microsoft Visual Studio Microsoft Internet Information Services (IIS) Microsoft SQL Server Adobe Photoshop

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  • Ruby on Rails 2.3.5: Populating my prod and devel database with data (migration or fixture?)

    - by randombits
    I need to populate my production database app with data in particular tables. This is before anyone ever even touches the application. This data would also be required in development mode as it's required for testing against. Fixtures are normally the way to go for testing data, but what's the "best practice" for Ruby on Rails to ship this data to the live database also upon db creation? ultimately this is a two part question I suppose. 1) What's the best way to load test data into my database for development, this will be roughly 1,000 items. Is it through a migration or through fixtures? The reason this is a different answer than the question below is that in development, there's certain fields in the tables that I'd like to make random. In production, these fields would all start with the same value of 0. 2) What's the best way to bootstrap a production db with live data I need in it, is this also through a migration or fixture? I think the answer is to seed as described here: http://lptf.blogspot.com/2009/09/seed-data-in-rails-234.html but I need a way to seed for development and seed for production. Also, why bother using Fixtures if seeding is available? When does one seed and when does one use fixtures?

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  • how to handel failure mails using PHP?

    - by Navruk
    example:- If i sent a mail through gmail to this id "[email protected]" i got error like "Delivery to the following recipient failed permanently:" My question is:- If i sent using PHP mail function, how can i catch failure email id? code:- // To send HTML mail, the Content-type header must be set $headers = 'MIME-Version: 1.0' . "\r\n"; $headers .= 'Content-type: text/html; charset=iso-8859-1' . "\r\n"; // Additional headers $headers .= 'To: Mary <[email protected]>, Kelly <[email protected]>' . "\r\n"; $headers .= 'From: Birthday Reminder <[email protected]>' . "\r\n"; $headers .= 'Cc: [email protected]' . "\r\n"; $headers .= 'Bcc: [email protected]' . "\r\n"; $to = "[email protected]"; $subject = "Testing"; $message = "Testing body"; mail($to, $subject, $message, $headers);

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  • how to Compute the average probe length for success and failure - Linear probe (Hash Tables)

    - by fang_dejavu
    hi everyone, I'm doing an assignment for my Data Structures class. we were asked to to study linear probing with load factors of .1, .2 , .3, ...., and .9. The formula for testing is: The average probe length using linear probing is roughly Success-- ( 1 + 1/(1-L)**2)/2 or Failure-- (1+1(1-L))/2. we are required to find the theoretical using the formula above which I did(just plug the load factor in the formula), then we have to calculate the empirical (which I not quite sure how to do). here is the rest of the requirements **For each load factor, 10,000 randomly generated positive ints between 1 and 50000 (inclusive) will be inserted into a table of the "right" size, where "right" is strictly based upon the load factor you are testing. Repeats are allowed. Be sure that your formula for randomly generated ints is correct. There is a class called Random in java.util. USE it! After a table of the right (based upon L) size is loaded with 10,000 ints, do 100 searches of newly generated random ints from the range of 1 to 50000. Compute the average probe length for each of the two formulas and indicate the denominators used in each calculationSo, for example, each test for a .5 load would have a table of size approximately 20,000 (adjusted to be prime) and similarly each test for a .9 load would have a table of approximate size 10,000/.9 (again adjusted to be prime). The program should run displaying the various load factors tested, the average probe for each search (the two denominators used to compute the averages will add to 100), and the theoretical answers using the formula above. .** how do I calculate the empirical success?

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  • how can I save/keep-in-sync an in-memory graph of objects with the database?

    - by Greg
    Question - What is a good best practice approach for how can I save/keep-in-sync an jn-memory graph of objects with the database? Background: That is say I have the classes Node and Relationship, and the application is building up a graph of related objects using these classes. There might be 1000 nodes with various relationships between them. The application needs to query the structure hence an in-memory approach is good for performance no doubt (e.g. traverse the graph from Node X to find the root parents) The graph does need to be persisted however into a database with tables NODES and RELATIONSHIPS. Therefore what is a good best practice approach for how can I save/keep-in-sync an jn-memory graph of objects with the database? Ideal requirements would include: build up changes in-memory and then 'save' afterwards (mandatory) when saving, apply updates to database in correct order to avoid hitting any database constraints (mandatory) keep persistence mechanism separate from model, for ease in changing persistence layer if needed, e.g. don't just wrap an ADO.net DataRow in the Node and Relationship classes (desirable) mechanism for doing optimistic locking (desirable) Or is the overhead of all this for a smallish application just not worth it and I should just hit the database each time for everything? (assuming the response times were acceptable) [would still like to avoid if not too much extra overhead to remain somewhat scalable re performance]

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  • Recycle Freed Objects

    - by uray
    suppose I need to allocate and delete object on heap frequently (of arbitrary size), is there any performance benefit if instead of deleting those objects, I will return it back to some "pool" to be reused later? would it give benefit by reduce heap allocation/deallocation?, or it will be slower compared to memory allocator performance, since the "pool" need to manage a dynamic collection of pointers. my use case: suppose I create a queue container based on linked list, and each node of that list are allocated on the heap, so every call to push() and pop() will allocate and deallocate that node: ` template <typename T> struct QueueNode { QueueNode<T>* next; T object; } template <typename T> class Queue { void push(T object) { QueueNode<T>* newNode = QueueNodePool<T>::get(); //get recycled node if(!newNode) { newNode = new QueueNode<T>(object); } // push newNode routine here.. } T pop() { //pop routine here... QueueNodePool<T>::store(unusedNode); //recycle node return unusedNode->object; } } `

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  • Do complex JOINs cause high coupling and maintenance problems ?

    - by ashkan.kh.nazary
    Our project has ~40 tables with complex relations.A colleague believes in using long join queries which enforces me to learn about tables outside of my module but I think I should not concern about tables not directly related to my module and use data access functions (written by those responsible for other modules) when I need data from them. Let me clarify: I am responsible for the ContactVendor module which enables the customers to contact the vendor and start a conversation about some specific product. Products module has it's own complex tables and relations with functions that encapsulate details (for example i18n, activation, product availability etc ...). Now I need to show the product title of some product related to some conversation between the vendor and customers. I may either write a long query that retrieves the product info along with conversation stuff in one shot (which enforces me to learn about Product tables) OR I may pass the relevant product_id to the get_product_info(int) function. First approach is obviously demanding and introduces many bad practices and things I normally consider fault in programming. The problem with the second approach seems to be the countless mini queries these access functions cause and performance loss is a concern when a loop tries to fetch product titles for 100 products using functions that each perform a separate query. So I'm stuck between "don't code to the implementation, code to interface" and performance. What is the right way of doing things ? UPDATE: I'm specially concerned about possible future modifications to those tables outside of my module. What if the Products module decided to change the way they are doing things? or for some reason modify the schema? It means some other modules would break or malfunction until the change is integrated to them. The usual ripple effect problem.

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  • Changing the indexing on existing table in SQL Server 2000

    - by Raj
    Guys, Here is the scenario: SQL Server 2000 (8.0.2055) Table currently has 478 million rows of data. The Primary Key column is an INT with IDENTITY. There is an Unique Constraint imposed on two other columns with a Non-Clustered Index. This is a vendor application and we are only responsible for maintaining the DB. Now the vendor has recommended doing the following "to improve performance" Drop the PK and Clustered Index Drop the non-clustered index on the two columns with the UNIQUE CONSTRAINT Recreate the PK, with a NON-CLUSTERED index Create a CLUSTERED index on the two columns with the UNIQUE CONSTRAINT I am not convinced that this is the right thing to do. I have a number of concerns. By dropping the PK and indexes, you will be creating a heap with 478 million rows of data. Then creating a CLUSTERED INDEX on two columns would be a really mammoth task. Would creating another table with the same structure and new indexing scheme and then copying the data over, dropping the old table and renaming the new one be a better approach? I am also not sure how the stored procs will react. Will they continue using the cached execution plan, considering that they are not being explicitly recompiled. I am simply not able to understand what kind of "performance improvement" this change will provide. I think that this will actually have the reverse effect. All thoughts welcome. Thanks in advance, Raj

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