Search Results

Search found 14924 results on 597 pages for 'selector performance'.

Page 368/597 | < Previous Page | 364 365 366 367 368 369 370 371 372 373 374 375  | Next Page >

• Recommended textbook for machine-level programming?

  - by Norman Ramsey

  I'm looking at textbooks for an undergraduate course in machine-level programming. If the perfect book existed, this is what it would look like: Uses examples written in C or assembly language, or both. Covers machine-level operations such as two's-complement integer arithmetic, bitwise operations, and floating-point arithmetic. Explains how caches work and how they affect performance. Explains machine instructions or assembly instructions. Bonus if the example assembly language includes x86; triple bonus if it includes x86-64 (aka AMD64). Explains how C values and data structures are represented using hardware registers and memory. Explains how C control structures are translated into assembly language using conditional and unconditional branch instructions. Explains something about procedure calling conventions and how procedure calls are implemented at the machine level. Books I might be interested in would probably have the words "machine organization" or "computer architecture" in the title. Here are some books I'm considering but am not quite happy with: Computer Systems: A Programmer's Perspective by Randy Bryant and Dave O'Hallaron. This is quite a nice book, but it's a book for a broad, shallow course in systems programming, and it contains a great deal of material my students don't need. Also, it is just out in a second edition, which will make it expensive. Computer Organization and Design: The Hardware/Software Interface by Dave Patterson and John Hennessy. This is also a very nice book, but it contains way more information about how the hardware works than my students need. Also, the exercises look boring. Finally, it has a show-stopping bug: it is based very heavily on MIPS hardware and the use of a MIPS simulator. My students need to learn how to use DDD, and I can't see getting this to work on a simulator. Not to mention that I can't see them cross-compiling their code for the simulator, and so on and so forth. Another flaw is that the book mentions the x86 architecture only to sneer at it. I am entirely sympathetic to this point of view, but news flash! You guys lost! Write Great Code Vol I: Understanding the Machine by Randall Hyde. I haven't evaluated this book as thoroughly as the other two. It has a lot of what I need, but the translation from high-level language to assembler is deferred to Volume Two, which has mixed reviews. My students will be annoyed if I make them buy a two-volume series, even if the price of those two volumes is smaller than the price of other books. I would really welcome other suggestions of books that would help students in a class where they are to learn how C-language data structures and code are translated to machine-level data structures and code and where they learn how to think about performance, with an emphasis on the cache.

  Read the article

• NSData release is not reclaiming memory

  - by ctpenrose

  iPhoneOS 3.2 I use NSKeyedUnarchiver's unarchiveObjectWithFile: to load a custom object that contains a single large NSData and another much smaller object. The dealloc method in my custom object gets called, the NSData object is released, its retainCount == 1 just before. Physical memory does not decrement by any amount, let alone a fraction of the NSData size, and with repetition memory warnings are reliably generated: I have test until I actually received level 2 warnings. =( NSString *archivePath = [[[NSBundle mainBundle] pathForResource:@"lingering"] ofType:@"data"] retain]; lingeringDataContainer = [[NSKeyedUnarchiver unarchiveObjectWithFile:archivePath] retain]; [archivePath release]; [lingeringDataContainer release]; and now the dealloc.... - (void) dealloc { [releasingObject release]; [lingeringData release]; [super dealloc]; } Before release: (gdb) p (int) [(NSData *) lingeringData retainCount] $1 = 1 After: (gdb) p (int) [(NSData *) lingeringData retainCount] Target does not respond to this message selector.

  Read the article

• Comparison of algorithmic approaches to the N queens problem

  - by iceman

  I wanted to evaluate performance comparisons for various approaches to solving the N queens problem. Mainly AI metaheuristics based algorithms like simulated annealing, tabu search and genetic algorithm etc compared to exact methods(like backtracking). Is there any code available for study? A lot of real-world optimization problems like it consider cooperative schemes between exact methods and metaheuristics.

  Read the article

• java.util.zip - ZipInputStream v.s. ZipFile

  - by lucho

  Hello, community! I have some general questions regarding the java.util.zip library. What we basically do is an import and an export of many small components. Previously these components were imported and exported using a single big file, e.g.: <component-type-a id="1"/> <component-type-a id="2"/> <component-type-a id="N"/> <component-type-b id="1"/> <component-type-b id="2"/> <component-type-b id="N"/> Please note that the order of the components during import is relevant. Now every component should occupy its own file which should be externally versioned, QA-ed, bla, bla. We decided that the output of our export should be a zip file (with all these files in) and the input of our import should be a similar zip file. We do not want to explode the zip in our system. We do not want opening separate streams for each of the small files. My current questions: Q1. May the ZipInputStream guarantee that the zip entries (the little files) will be read in the same order in which they were inserted by our export that uses ZipOutputStream? I assume reading is something like: ZipInputStream zis = new ZipInputStream(new BufferedInputStream(fis)); ZipEntry entry; while((entry = zis.getNextEntry()) != null) { //read from zis until available } I know that the central zip directory is put at the end of the zip file but nevertheless the file entries inside have sequential order. I also know that relying on the order is an ugly idea but I just want to have all the facts in mind. Q2. If I use ZipFile (which I prefer) what is the performance impact of calling getInputStream() hundreds of times? Will it be much slower than the ZipInputStream solution? The zip is opened only once and ZipFile is backed by RandomAccessFile - is this correct? I assume reading is something like: ZipFile zipfile = new ZipFile(argv[0]); Enumeration e = zipfile.entries();//TODO: assure the order of the entries while(e.hasMoreElements()) { entry = (ZipEntry) e.nextElement(); is = zipfile.getInputStream(entry)); } Q3. Are the input streams retrieved from the same ZipFile thread safe (e.g. may I read different entries in different threads simultaneously)? Any performance penalties? Thanks for your answers!

  Read the article

• Do display objects outside of stage bounds still get rendered by Flash?

  - by Pup

  If an object exists outside of Flash's stage boundaries, is on the Display List, and is visible, is it causing a performance hit from Flash rendering it? In other words, does Flash render what isn't seen? This leads me to believe so: http://stackoverflow.com/questions/170203/how-do-you-make-flash-not-render-an-object-on-the-stage

  Read the article

• what is the proper way to do logging in csv file?

  - by user2003548

  i want to log some information of every single request send to a busy http server in a formatted form,use log module would create some thing i don't want to: [I 131104 15:31:29 Sys:34] i think of csv format but i don't know how to customize it,and python got csv module,but read the manual import csv with open('some.csv', 'w', newline='') as f: writer = csv.writer(f) writer.writerows(someiterable) since it would open and close a file each time, i am afraid in this way would slow down the whole server performance, what could i do?

  Read the article

• How to select nth element of particular type in enlive?

  - by Mad Wombat

  I am trying to scrape some data from a page with a table based layout. So, to get some of the data I need to get something like 3rd table inside 2nd table inside 5th table inside 1st table inside body. I am trying to use enlive, but cannot figure out how to use nth-of-type and other selector steps. To make matters worse, the page in question has a single top level table inside the body, but (select data [:body : :table]) returns 6 results for some reason. What the hell am I doing wrong?

  Read the article

• Exception handling best practices

  - by Costa

  Hi Is there any performance problem or something else about letting the exception to propagate, or it is better to write it like this try { } catch { throw; }

  Read the article

• Can we change dynamically the interval of "schedule" ?

  - by micropsari

  Hello, I'm making a game on iPhone using cocos2d, and I have a question. In my init method I'm doing this : [self schedule:@selector(newMonster:) interval:1]; It create a new monster every second. But I'd like that the interval change over time. For example : -The 10 first seconds of the game: a new monster appears every 1 second. -Then for 10 seconds: a new monster appears every 0.8 second. -And after every 0.5 second... How can I do that? Thanks !

  Read the article

• Memory leak appears only when multiprocessing

  - by Sandro

  I am trying to use python's multiprocessing library to hopefully gain some performance. Specifically I am using its map function. Now, for some reason when I swap it out with its single threaded counterpart I don't get any memory leaks over time. But using the multiprocessing version of map causes my memory to go through the roof. For the record I am doing something which can easily hog up loads of memory, but what would the difference be between the two to cause such a stark difference?

  Read the article

• What is the best algorithm for an overridden System.Object.GetHashCode?

  - by bitbonk

  In .NET System.Object.GetHashCode method is use in a lot of places throughout the .NET base class libraries. Especially when finding items in a collection fast or to determine equality. Is there a standard algorithm/ best practise on how to implement the GetHashCode override for my custom classes so I don't degrate performance?

  Read the article

• Postgres: Convert varchar to text

  - by williamjones

  I screwed up and created a column as a varchar(255) where that is no longer sufficient. I've read that varchar has no performance benefits over text on Postgres, and so would like to convert the varchar to a text column in a safe way that preserves the data. What's the best way for me to do this?

  Read the article

• What is the need of collection framework in java?

  - by JavaUser

  Hi, What is the need of Collection framework in Java since all the data operations(sorting/adding/deleting) are possible with Arrays and moreover array is suitable for memory consumption and performance is also better compared with Collections. Can anyone point me a real time data oriented example which shows the difference in both(array/Collections) of these implementations. Thx

  Read the article

• When and where do you put type annotations in Clojure code?

  - by Michiel Borkent

  When and where do you put type annotations in Clojure code? Obviously when performance counts. But are there rules by which you can live of when (only when doing Java Interop?) and where to add them (function definition arguments)?

  Read the article

• Please help with iPhone Memory & Images, memory usage crashing app

  - by Andrew Gray

  I have an issue with memory usage relating to images and I've searched the docs and watched the videos from cs193p and the iphone dev site on memory mgmt and performance. I've searched online and posted on forums, but I still can't figure it out. The app uses core data and simply lets the user associate text with a picture and stores the list of items in a table view that lets you add and delete items. Clicking on a row shows the image and related text. that's it. Everything runs fine on the simulator and on the device as well. I ran the analyzer and it looked good, so i then starting looking at performance. I ran leaks and everything looked good. My issue is when running Object Allocations as every time i select a row and the view with the image is shown, the live bytes jumps up a few MB and never goes down and my app eventually crashes due to memory usage. Sorting the live bytes column, i see 2 2.72MB mallocs (5.45Mb total), 14 CFDatas (3.58MB total), 1 2.74MB malloc and everything else is real small. the problem is all the related info in instruments is really technical and all the problem solving examples i've seen are just missing a release and nothing complicated. Instruments shows Core Data as the responsible library for all but one (libsqlite3.dylib the other) with [NSSQLCore _prepareResultsFromResultSet:usingFetchPlan:withMatchingRows:] as the caller for all but one (fetchResultSetReallocCurrentRow the other) and im just not sure how to track down what the problem is. i've looked at the stack traces and opened the last instance of my code and found 2 culprits (below). I havent been able to get any responses at all on this, so if anyone has any tips or pointers, I'd really appreciate it!!!! //this is from view controller that shows the title and image - (void)viewWillAppear:(BOOL)animated { [super viewWillAppear:animated]; self.title = item.title; self.itemTitleTextField.text = item.title; if ([item.notes length] == 0) { self.itemNotesTextView.hidden = YES; } else { self.itemNotesTextView.text = item.notes; } //this is the line instruments points to UIImage *image = item.photo.image; itemPhoto.image = image; } - (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath { if (editingStyle == UITableViewCellEditingStyleDelete) { // Delete the managed object for the given index path NSManagedObjectContext *context = [fetchedResultsController managedObjectContext]; [context deleteObject:[fetchedResultsController objectAtIndexPath:indexPath]]; // Save the context. NSError *error = nil; if (![context save:&error]) //this is the line instruments points to { NSLog(@"Unresolved error %@, %@", error, [error userInfo]); exit(-1); } } }

  Read the article

• C# XPath id() not working?

  - by Iggyhopper

  I'm using C# and I'm stumped. Does it just not support id()? I have a large XML file, about 4-5 of them at ~400kb, so I need some speed and performance wherever I can get it. I use XmlDocument.SelectSingleNode("id('blahblahblah')") and it doesn't get the node by id. Am I going crazy or is it that C# XPath just doesn't support id()?

  Read the article

• springboard takes too much CPU

  - by tbarbe

  Is there a way to increase the application priority for the CPU on iPhone? I notice that SpringBoard takes up too much CPU at times causing some fluctuation in performance on the device.

  Read the article

• Exploding by Array of Delimiters

  - by JoeC

  Is there any way to explode() using an array of delimiters? PHP Manual: array explode ( string $delimiter , string $string [, int $limit ] ) Instead of using string $delimiter is there any way to use array $delimiter without affecting performance too much?

  Read the article

• Concise way to getattr() and use it if not None in Python

  - by MTsoul

  I am finding myself doing the following a bit too often: attr = getattr(obj, 'attr', None) if attr is not None: attr() # Do something, either attr(), or func(attr), or whatever else: # Do something else Is there a more pythonic way of writing that? Is this better? (At least not in performance, IMO.) try: obj.attr() # or whatever except AttributeError: # Do something else

  Read the article

• Fastest way to read every 30th byte of large binary file?

  - by timmerk

  What is the fastest way to read every 30th byte of a large binary file (2-3 GB)? I've read there are performance problems with fseek because of I/O buffers, but I don't want to read 2-3 GB of data into memory before grabbing every 30th byte either.

  Read the article

• Using memcached as a session storage with CodeIgniter

  - by Alex N.

  I am researching possibilities of using memcached as a session storage for a system built on CodeIgniter. Has anybody done this before(that's probably a stupid question :) and if so what's your experience folks? Have you used any existing libraries/extensions? As far as performance improvement what have you seen? Any caveats?

  Read the article

• Reasons for Parallel Extensions working slowly

  - by darja

  I am trying to make my calculating application faster by using Parallel Extensions. I am new in it, so I have just replaced the main foreach loop with Parallel.ForEach. But calculating became more slow. What can be common reasons for decreasing performance of parallel extensions? Thanks

  Read the article

• Detecting/Repairing NSConnection failure

  - by anthony

  I would like to use NSConnection/NSDistributedObject for interprocess communication. I would like the client to be able to handle the case where the server is only occasionally reachable. How can I determine if sending a message to the NSConnection will fail or has failed? Currently if my server (the process that has vended the remote object) dies, the client will crash if it sends a selector to the remote object. Ideally I'd like to have a wrapper for the remote object that can lazily instantiate (or reinstantiate) the connection, and return a default value in the case where the connection could not be instantiated, or the connection has failed. I don't really know the correct way to do this using objective c. Here's some pseudocode representing this logic: if myConnection is null: instantiate myConnection if MyConnection is null: return defaultValue try return [myConnection someMethod] catch myConnection = null return defaultValue

  Read the article

• Is 'epoll' the essential reason that Tornadoweb(or Nginx) is so fast?

  - by Mickey Shine

  Tornadoweb and Nginx are popular web servers for the moment and many benchmarkings show that they have a better performance than Apache under certain circumstances. So my question is: Is 'epoll' the most essential reason that make them so fast? And what can I learn from that if I want to write a good socket server?

  Read the article

• Best approach to write huge xml data to file?

  - by Kayes

  Hi. I'm currently exporting a database table with huge data (100000+ records) into an xml file using XmlTextWriter class and I'm writing directly to a file on the physical drive. _XmlTextWriterObject = new XmlTextWriter(_xmlFilePath, null); While my code runs ok, my question is that is it the best approach? Or should I write the whole xml in memory stream first and then write the xml document in physical file from memory stream? And what are the effects on memory/ performance in both cases?

  Read the article

< Previous Page | 364 365 366 367 368 369 370 371 372 373 374 375  | Next Page >