efficient storage - Page 261

Differentiate A Section/Portion of 3D object From Other Parts

- by Ramshad

I am trying to write a WPF windows application that dynamically creates a 3 D object for an existing 3D Image. The senerio is as follows. Mark the points randomly on the existing 3D Image. Create a 3D object based on the points already marked. Check the below Sample Screenshots. Screenshot 1 and Screenshot 2 I am successfully able to load the 3D file to the WPF form. And was able to perform the rotation using TrackballDecorator 3D Tools library. I have just read this related post. however i didn't get it exactly :) So,can you suggest some efficient methods to achieve it.

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Logging NHibernate SQL queries

- by GuestMVCAsync

Is there a way to access the full SQL query, including the values, inside my code? I am able to log SQL queries using log4net: <logger name="NHibernate.SQL" additivity="false"> <level value="ALL"/> <appender-ref ref="NHibernateSQLFileLog"/> </logger> However, I would like to find a way to log SQL queries from the code also. This way I will log the specific SQL query that causes an exception in my try/catch statement. Right now I have to data-mine the SQLFileLog to find the query that caused the exception when an exception occurs and it is not efficient.

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Secondary keys in a B-tree

- by Phenom

Let's say that there is a file that contains an unsorted list of student information, which includes a student ID number as well as other information. I want to make a program that retrieves student information based on student ID number. In order to make it efficient, I store the student IDs in a B-tree. So when I enter a student ID number, it searches the B-tree to see if its there or not. It also does one more thing. If it finds the student ID number, then it also returns where in the file that student's information is. This is the secondary key. The program uses this information to locate the rest of the student's information and prints it to screen. Can this be done? Is this how a b-tree works?

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MPFR Rounding 0.9999 to 1?

- by Silmaersti

I'm attempting to store the value 0.9999 into an mpfr_t variable But 0.9999 is rounded to 1 (or some other value != 0.9999) during storage, no matter the round value (GMP_RNDD, GMP_RNDU, GMP_RNDN, GMP_RNDZ) So what's the best method to store 0.9999 in an mpfr_t variable? Is it possible? Here is my test program, it prints "buffer is: 1", instead of the wanted "buffer is: 0.9999": int main() { size_t precision = 4; mpfr_t mpfrValue; mpfr_init2(mpfrValue, precision); mpfr_set_str(mpfrValue, "0.9999", 10, GMP_RNDN); char *buffer = (char*)malloc((sizeof(char) * precision) + 3); mp_exp_t exponent; mpfr_get_str(buffer, &exponent, 10, precision, mpfrValue, GMP_RNDN); printf("buffer is: %s\n", buffer); free(buffer); mpfr_clear(mpfrValue); return 0; } Thanks for any help !

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C++ Thread Safe Integer

- by Paul Ridgway

Hello everyone, I have currently created a C++ class for a thread safe integer which simply stores an integer privately and has public get a set functions which use a boost::mutex to ensure that only one change at a time can be applied to the integer. Is this the most efficient way to do it, I have been informed that mutexes are quite resource intensive? The class is used a lot, very rapidly so it could well be a bottleneck... Googleing C++ Thread Safe Integer returns unclear views and oppinions on the thread safety of integer operations on different architectures. Some say that a 32bit int on a 32bit arch is safe, but 64 on 32 isn't due to 'alignment' Others say it is compiler/OS specific (which I don't doubt). I am using Ubuntu 9.10 on 32 bit machines, some have dual cores and so threads may be executed simultaneously on different cores in some cases and I am using GCC 4.4's g++ compiler. Thanks in advance...

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Opinions regarding C++ programming practice

- by Sagar

I have a program that I am writing, not too big. Apart from the main function, it has about 15 other functions that called for various tasks at various times. The code works just fine all in one file, and as it is right now. However, I was wondering if anyone had any advice on whether it is smarter/more efficient/better programming to put those functions in a separate file different from where main is, or whether it even matters at all. If yes, why? If no, why not? I am not new at C++, but definitely not an expert either, so if you think this question is stupid, feel free to tell me so. Thanks for your time!

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Servlet 3 spec and ThreadLocal

- by mindas

As far as I know, Servlet 3 spec introduces asynchronous processing feature. Among other things, this will mean that the same thread can and will be reused for processing another, concurrent, HTTP request(s). This isn't revolutionary, at least for people who worked with NIO before. Anyway, this leads to another important thing: no ThreadLocal variables as a temporary storage for the request data. Because if the same thread suddenly becomes the carrier thread to a different HTTP request, request-local data will be exposed to another request. All of that is my pure speculation based on reading articles, I haven't got time to play with any Servlet 3 implementations (Tomcat 7, GlassFish 3.0.X, etc.). So, the questions: Am I correct to assume that ThreadLocal will cease to be a convenient hack to keep the request data? Has anybody played with any of Servlet 3 implementations and tried using ThreadLocals to prove the above? Apart from storing data inside HTTP Session, are there any other similar easy-to-reach hacks you could possibly advise?

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java statistics collection for performance evaluation

- by user384706

What is the most efficient way to collect and report performance statistic analysis from an application? If I have an application that uses a series of network apis, and I want to report statistics at runtime, e.g. Method doA() was called 3 times and consumed on avg 500ms Method doB() was called 5 times and consumed on avg 1200ms etc Then, I thought of using a well defined data structure (of collection) that each thread updates per remote call, and this can be used for the report. But I think that it will make the performance worse, for the time spend for statistics collection. Am I correct? How would I procceed if I used a background thread for this, and the other threads that did the remote calls were unaware of this collection gathering? Thanks

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Exploring search options for PHP

- by Joshua

I have innoDB table using numerous foreign keys, but we just want to look up some basic info out of it. I've done some research but still lost. 1) How can I tell if my host has Sphinx installed already? I don't see it as an option for table storage method (i.e. innodb, myisam). 2) Zend_Search_Lucene, responsive enough for AJAX functionality of millions of records? 3) Mirror my innoDB with a myisam? Make every innodb transaction end with a write to the myisam, then use 1:1 lookups? How would I do this automagically? This should make MyISAM ACID-compliant and free(er) from corruption no? 4) PostgreSQL fulltext queries don't even look like SQL to me wtf, I don't have time to learn a new SQL syntax I need noob options 5) ???????????????????? This is high volume site on a decently-equipped VPS Thanks very much for any ideas.

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Finding mySQL duplicates, then merging data

- by Michael Pasqualone

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Fast, Vectorizable method of taking floating point number modulus of special primes?

- by caffiend

Is there a fast method for taking the modulus of a floating point number? With integers, there are tricks for Mersenne primes, so that its possible to calculate y = x MOD 2^31 without needing division. Can any similar tricks be applied for floating point numbers? Preferably, in a way that can be converted into vector/SIMD operations, or moved into GPGPU code. The primes I'm interested in would be 2^7 and 2^31, although if there are more efficient ones for floating point numbers, those would be welcome.

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Write data into .txt file created by CFileDialog, in C++

- by younevertell

I wanna Write data into .txt file created by CFileDialog, in C++. The problem I am facing is that below codes doesn't work, although there is no build error. The .txt file created by CFileDialog can not be found for some reason. What's wrong the code? what's the efficient way to Write data into .txt file created by CFileDialog, in C++? Thanks CFileDialog dlg(FALSE, NULL, NULL, OFN_OVERWRITEPROMPT, _T("My Data File (*.txt)|*.txt||")); if(dlg.DoModal() != IDOK) return; CString filename = dlg.GetPathName(); ofstream outfile (filename); int mydata = 10; outfile << "my data:" << mydata << endl; outfile.close();

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Determining whether a file is a duplicate

- by Todd R

Is there a reliable way to determine whether or not two files are the same? For example, two files with the same size and type may or may not be the same binarilly (yeah, I know it's not really a word). I assume that comparing one or two checksums of the files will help, but I wonder: How reliable are checksums at determining whether two files are different; what are the chances of two different files having the same checksum? Would reliability increase by applying additional checksum comparisons? Which checksum algorithm(s) would be the most efficient and/or reliable? Any ideas, suggestions or thoughts are appreciated! P.S. The code for this is being written in Java running on a nix system, but generic or platform agnostic input is most helpful.

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how to play an encrypted file in Android.

- by user306517

I need to be able to play an encrypted file in Android. The file is AAC. The only way I can see to do this is either: decrypt the file to internal private storage and point the player at that file to play, or decrypt & decode the file to pcm and feed it to an AudioTrack. 1 isn't great because it takes a long time to do that. 2 isn't great either because I don't know how I can take advantage of the HW decoder to do this. Any ideas? tia.

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a completely decoupled OO system ?

- by shrini1000

To make an OO system as decoupled as possible, I'm thinking of the following approach: 1) we run an RMI/directory like service where objects can register and discover each other. They talk to this service through an interface 2) we run a messaging service to which objects can publish messages, and register subscription callbacks. Again, this happens through interfaces 3) when object A wants to invoke a method on object B, it discovers the target object's unique identity through #1 above, and publishes a message on the message service for object B 4) message services invokes B's callback to give it the message 5) B processes the request and sends the response for A on message service 6) A's callback is called and it gets the response. I feel this system is as decoupled as practically possible, but it has the following problems: 1) communication is typically asynchronous 2) hence it's non real time 3) the system as a whole is less efficient. Are there any other practical problems where this design obviously won't be applicable ? What are your thoughts on this design in general ?

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Core Data and iTunes File Sharing - Move/hide the .sqlite file on app update?

- by Eric

I have an iPad app that uses Core Data for data storage. I would like to enable file sharing in iTunes and I don't really want the users to be able to delete or modify the .sqlite file. Can I move the file to a different, hidden directory? Alternatively, could the file be made read-only? I wouldn't mind users having access to the file as long as it couldn't be changed. I suspect there is a trivial solution that is escaping me at the moment.

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Vim: Replacing a line with another one yanked before

- by duddle

At least once per day i have the following situation: A: This line should also replace line X ... X: This is line should be replaced I believe that I don't perform that task efficiently. What I do: Go to line A: AG Yank line A: yy Go to line X: XG Paste line A: P Move to old line: j Delete old line: dd This has the additional disadvantage that line X is now in the default register, which is annoying if I find another line that should be replaced with A. Yanking to and pasting from an additional register ("ayy, "aP) makes this simple task even less efficient. My Questions: Did I miss a built-in Vim command to replace a line yanked before? If not, how can I bind my own command that leaves (or restores) the yanked line in the default register?

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Result of Long Positive Integers & Search and element in array..

- by AGeek

Hi, I have two Questions for which I cannot find answers by googling, but I find these questions very important for preparation.. Kindly explain only the logic, I will be able to code. In Search of Efficient Logic..... in terms of Memory and Time. WAP to add two long positive integers. What Data structure / data type we can use to store the numbers and result. What is the best way to search an element from an array in shortest time. Size of the array could be large enough, and any elements could be stored in the array(i.e. no range). Thanks.

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Automatically update audit information on Entity

- by Nix

I have an entity model that has audit information on every table (50+ tables) CreateDate CreateUser UpdateDate UpdateUser Currently we are programatically updating audit information. Ex: if(changed){ entity.UpdatedOn = DateTime.Now; entity.UpdatedBy = Environment.UserName; context.SaveChanges(); } But I am looking for a more automated solution. During save changes, if an entity is created/updated I would like to automatically update these fields before sending them to the database for storage. Any suggestion on how i could do this? Let me know if any more information is needed.

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What's the best way to implement one-dimensional collision detection?

- by cyclotis04

I'm writing a piece of simulation software, and need an efficient way to test for collisions along a line. The simulation is of a train crossing several switches on a track. When a wheel comes within N inches of the switch, the switch turns on, then turns off when the wheel leaves. Since all wheels are the same size, and all switches are the same size, I can represent them as a single coordinate X along the track. Switch distances and wheel distances don't change in relation to each other, once set. This is a fairly trivial problem when done through brute force by placing the X coordinates in lists, and traversing them, but I need a way to do so efficiently, because it needs to be extremely accurate, even when the train is moving at high speeds. There's a ton of tutorials on 2D collision detection, but I'm not sure the best way to go about this unique 1D scenario.

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Java escape HTML - string replace slow?

- by cpf

Hi StackOverflow, I have a Java application that makes heavy use of a large file, to read, process and give through to SolrEmbeddedServer (http://lucene.apache.org/solr/). One of the functions does basic HTML escaping: private String htmlEscape(String input) { return input.replace("&", "&").replace(">", ">").replace("<", "<") .replace("'", "'").replaceAll("\"", """); } While profiling the application, the program spends roughly 58% of the time in this function, a total of 47% in replace, and 11% in replaceAll. Now, is the Java replace that slow, or am I on the right path and should I consider the program efficient enough to have its bottleneck in Java and not in my code? (Or am I replacing wrong?) Thanks in advance!

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Workstation hardware at does your company buy developers?

- by Bosh

I'm curious to know what workstation hardware companies are devoting to you, as a developer -- and how much they're spending. I'd consider this thread a big success if I could shed some light on these questions: Do engineers at big companies use substantially different hardware than engineers at start-ups companies? Does a fresh developer recruit at Google get substantially different hardware from someone in the same position at Microsoft or Yahoo!? Do programmers in more senior positions have more powerful hardware on their desks? Does anyone think faster hardware makes more efficient engineers?

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RegEx to Reject Unescaped Character

- by JDV72

I want to restrict usage of unescaped ampersands in a particular input field. I'm having trouble getting a RegEx to kill usage of "&" unless followed by "amp;"...or perhaps just restrict usage of "& " (note the space). I tried to adapt the answer in this thread, but to no avail. Thanks. (FWIW, here's a RegEx I made to ensure that a filename field didn't contain restrited chars. and ended in .mp3. It works fine, but does it look efficient?)

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Error with global variable in php not extending to included php file

- by phileaton

I have an html file that calls has a php section in the header like so: $page = basename($_SERVER['PHP_SELF']); Now further down in the html file I have a included footer like so: <?php include("footer.php"); ?> In this script I am referencing the $page variable, but it doesn't find it. I tried echoing the variable and nothing happened. When I place the basename() code in the footer.php file though, it handled it fine. I'd like to be efficient with the coding, so how can I get the footer.php file to get that $page variable? Is there a better way to do this than including the $page variable twice?

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How can I speed up line by line reading of an ASCII file? (C++)

- by Jon

Here's a bit of code that is a considerable bottleneck after doing some measuring: //----------------------------------------------------------------------------- // Construct dictionary hash set from dictionary file //----------------------------------------------------------------------------- void constructDictionary(unordered_set<string> &dict) { ifstream wordListFile; wordListFile.open("dictionary.txt"); string word; while( wordListFile >> word ) { if( !word.empty() ) { dict.insert(word); } } wordListFile.close(); } I'm reading in ~200,000 words and this takes about 240 ms on my machine. Is the use of ifstream here efficient? Can I do better? I'm reading about mmap() implementations but I'm not understanding them 100%. The input file is simply text strings with *nix line terminations.

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Search found 9017 results on 361 pages for 'efficient storage'.

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- by Ramshad

- by GuestMVCAsync

- by Phenom

- by Silmaersti

- by Paul Ridgway

- by Sagar

- by mindas

- by user384706

- by Joshua

- by Michael Pasqualone

- by caffiend

- by younevertell

- by Todd R

- by user306517

- by shrini1000

- by Eric

- by duddle

- by AGeek

- by Nix

- by cyclotis04

- by cpf

- by Bosh

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