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  • Threadsafe way of exposing keySet()

    - by Jake
    This must be a fairly common occurrence where I have a map and wish to thread-safely expose its key set: public MyClass { Map<String,String> map = // ... public final Set<String> keys() { // returns key set } } Now, if my "map" is not thread-safe, this is not safe: public final Set<String> keys() { return map.keySet(); } And neither is: public final Set<String> keys() { return Collections.unmodifiableSet(map.keySet()); } So I need to create a copy, such as: public final Set<String> keys() { return new HashSet(map.keySet()); } However, this doesn't seem safe either because that constructor traverses the elements of the parameter and add()s them. So while this copying is going on, a ConcurrentModificationException can happen. So then: public final Set<String> keys() { synchronized(map) { return new HashSet(map.keySet()); } } seems like the solution. Does this look right?

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  • Guid Primary /Foreign Key dilemma SQL Server

    - by Xience
    Hi guys, I am faced with the dilemma of changing my primary keys from int identities to Guid. I'll put my problem straight up. It's a typical Retail management app, with POS and back office functionality. Has about 100 tables. The database synchronizes with other databases and receives/ sends new data. Most tables don't have frequent inserts, updates or select statements executing on them. However, some do have frequent inserts and selects on them, eg. products and orders tables. Some tables have upto 4 foreign keys in them. If i changed my primary keys from 'int' to 'Guid', would there be a performance issue when inserting or querying data from tables that have many foreign keys. I know people have said that indexes will be fragmented and 16 bytes is an issue. Space wouldn't be an issue in my case and apparently index fragmentation can also be taken care of using 'NEWSEQUENTIALID()' function. Can someone tell me, from there experience, if Guid will be problematic in tables with many foreign keys. I'll be much appreciative of your thoughts on it...

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  • Memory efficient collection class

    - by Joe
    I'm building an array of dictionaries (called keys) in my iphone application to hold the section names and row counts for a tableview. the code looks like this: [self.results removeAllObjects]; [self.keys removeAllObjects]; NSUInteger i,j = 0; NSString *key = [NSString string]; NSString *prevKey = [NSString string]; if ([self.allResults count] > 0) { prevKey = [NSString stringWithString:[[[self.allResults objectAtIndex:0] valueForKey:@"name"] substringToIndex:1]]; for (NSDictionary *theDict in self.allResults) { key = [NSString stringWithString:[[theDict valueForKey:@"name"] substringToIndex:1]]; if (![key isEqualToString:prevKey]) { NSDictionary *newDictionary = [NSDictionary dictionaryWithObjectsAndKeys: [NSNumber numberWithInt:i],@"count", prevKey,@"section", [NSNumber numberWithInt:j], @"total",nil]; [self.keys addObject:newDictionary]; prevKey = [NSString stringWithString:key]; i = 1; } else { i++; } j++; } NSDictionary *newDictionary = [NSDictionary dictionaryWithObjectsAndKeys: [NSNumber numberWithInt:i],@"count", prevKey,@"section", [NSNumber numberWithInt:j], @"total",nil]; [self.keys addObject:newDictionary]; } [self.tableview reloadData]; The code works fine first time through but I sometimes have to rebuild the entire table so I redo this code which orks fine on the simulator, but on my device the program bombs when I execute the reloadData line : malloc: *** mmap(size=3772944384) failed (error code=12) *** error: can't allocate region *** set a breakpoint in malloc_error_break to debug malloc: *** mmap(size=3772944384) failed (error code=12) *** error: can't allocate region *** set a breakpoint in malloc_error_break to debug Program received signal: “EXC_BAD_ACCESS”. If I remove the reloadData line the code works on the device. I'm wondering if this is something to do with the way I've built the keys array (ie using autoreleased strings and dictionaries).

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  • Split a map using Groovy

    - by Tihom
    I want to split up a map into an array of maps. For example, if there is a map with 25 key/value pairs. I want an array of maps with no more than 10 elements in each map. How would I do this in groovy? I have a solution which I am not excited about, is there better groovy version: static def splitMap(m, count){ if (!m) return def keys = m.keySet().toList() def result = [] def num = Math.ceil(m?.size() / count) (1..num).each { def min = (it - 1) * count def max = it * count > keys.size() ? keys.size() - 1 : it * count - 1 result[it - 1] = [:] keys[min..max].each {k -> result[it - 1][k] = m[k] } } result } m is the map. Count is the max number of elements within the map.

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  • cellForRowAtIndexPath called too late

    - by Mihai Fonoage
    Hi, I am trying to re-load a table every time some data I get from the web is available. This is what I have: SearchDataViewController: - (void)parseDatatXML { parsingDelegate = [[XMLParsingDelegate alloc] init]; parsingDelegate.searchDataController = self; // CONTAINS THE TABLE THAT NEEDS RE-LOADING; ImplementedSearchViewController *searchController = [[ImplementedSearchViewController alloc] initWithNibName:@"ImplementedSearchView" bundle:nil]; ProjectAppDelegate *delegate = [[UIApplication sharedApplication] delegate]; UINavigationController *nav = (UINavigationController *)[delegate.splitViewController.viewControllers objectAtIndex: 0]; NSArray *viewControllers = [[NSArray alloc] initWithObjects:nav, searchController, nil]; self.splitViewController.viewControllers = viewControllers; [viewControllers release]; // PASS A REFERENCE TO THE PARSING DELEGATE SO THAT IT CAN CALL reloadData on the table parsingDelegate.searchViewController = searchController; [searchController release]; // Build the url request used to fetch data ... NSURLRequest *dataURLRequest = [NSURLRequest requestWithURL:[NSURL URLWithString:dataURL]]; parsingDelegate.feedConnection = [[[NSURLConnection alloc] initWithRequest:dataURLRequest delegate:parsingDelegate] autorelease]; } ImplementedSearchViewController: - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { NSLog(@"count = %d", [keys count]); // keys IS A NSMutableArray return [self.keys count]; } - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { ... cell.textLabel.text = [keys objectAtIndex:row]; ... } XMLParsingDelgate: -(void) updateSearchTable:(NSArray *)array { ... [self.currentParseBatch addObject:(NSString *)[array objectAtIndex:1]]; // RELOAD TABLE [self.searchViewController.table reloadData]; } - (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qualifiedName attributes:(NSDictionary *)attributeDict { if ([elementName isEqualToString:@"..."]) { self.currentParseBatch = [NSMutableArray array]; searchViewController.keys = self.currentParseBatch; ... } ... } - (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName { if ([elementName isEqualToString:@"..."]) { ... [self performSelectorOnMainThread:@selector(updateSearchTable:) withObject:array waitUntilDone:NO]; } ... } My problem is that when I debug, the calls go between reloadData and numberOfRowsInSection until the keys array is filled with the last data, time at which the cellForRowAtIndexPath gets called. I wanted the table to be updated for each element I send, one by one, instead of just in the end. Any ideas why this behavior? Thank you!

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  • How to prevent the beep sound caused by alt key pressed in a WinForms TextBox?

    - by Michael Johnson
    I'm creating a routine that allows the user to replicate keyboard shortcuts into a textbox for 'custom keyboard shortcuts' customization, but every time the alt key is pressed with another letter, it produces another sound. I'm capturing the keys in the textbox_keydown event to parse the modifiers + other keys into a readable Shift + A or Ctrl + Shift + B manner into that very same textbox. Should I be doing this in a different event like textbox_previewkey instead of textbox_keydown? How can I prevent the alt modifier key + a letter or number causing the Beep sound? the textbox is just a normal .net 3.5 textbox with the only edited properties of it being the ReadOnly property to false. Is there a better way I could re-do this? I'm currently just checking that if any modifiers keys are pressed and then + a-z or 0-9, then to go ahead and input the appropriately pressed keys into that same textbox like Shift + A or Ctrl + Shift + Y.

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  • How can I specify a relative path in a Python logging config file?

    - by ClaudioA
    I've the following file to config logging: [loggers] keys=root [handlers] keys = root [formatters] keys = generic # Loggers [logger_root] level = DEBUG handlers = root # Handlers [handler_root] class = handlers.RotatingFileHandler args = ("test.log", "maxBytes=1*1024*1024", "backupCount=10") level = NOTSET formatter = generic # Formatters [formatter_generic] format = %(asctime)s,%(msecs)03d %(levelname)-5.5s [%(name)s] %(message)s datefmt = %Y-%m-%d %H:%M:%S In Development this works great, but when I deploy the application test.log is trying to be written in a path in which I don't have the necessary permission. So my question is, How can I do to specify a relative path in this configuration file.

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  • What's wrong with this statement in perl?

    - by benjamin button
    print "$_", join(',',sort keys %$h),"\n"; It's giving me an error below: Use of uninitialized value in string at missing_months.pl line 36. 1,10,11,12 this print statement is present in a for loop as below: foreach my $num ( sort keys %hash ) { my $h = $hash{$num}; print "$_", join(',',sort keys %$h),"\n"; }

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  • How do I implement Hibernate Pagination using a cursor (so the results stay consistent, despite new

    - by hunterae
    Hey all, Is there any way to maintain a database cursor using Hibernate between web requests? Basically, I'm trying to implement pagination, but the data that is being paged is consistently changing (i.e. new records are added into the database). We are trying to set it up such that when you do your initial search (returning a maximum of 5000 results), and you page through the results, those same records always appear on the same page (i.e. we're not continuously running the query each time next and previous page buttons are clicked). The way we're currently implementing this is by merely selecting 5000 (at most) primary keys from the table we're paging, storing those keys in memory, and then just using 20 primary keys at a time to fetch their details from the database. However, we want to get away from having to store these keys in memory and would much prefer a database cursor that we just keep going back to and moving backwards and forwards over the cursor to generate pages. I tried doing this with Hibernate's ScrollableResults but found that I could not call methods like next() and previous() would cause an exception if you within a different web request / Hibernate session (no surprise there). Is there any way to reattach a ScrollableResults object to a Session, much the same way you would reattach a detached database object to make it persistent? Are there any other approaches to implement this data paging with consistent paging results without caching the primary keys?

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  • [Java] Safe way of exposing keySet().

    - by Jake
    This must be a fairly common occurrence where I have a map and wish to thread-safely expose its key set: public MyClass { Map<String,String> map = // ... public final Set<String> keys() { // returns key set } } Now, if my "map" is not thread-safe, this is not safe: public final Set<String> keys() { return map.keySet(); } And neither is: public final Set<String> keys() { return Collections.unmodifiableSet(map.keySet()); } So I need to create a copy, such as: public final Set<String> keys() { return new HashSet(map.keySet()); } However, this doesn't seem safe either because that constructor traverses the elements of the parameter and add()s them. So while this copying is going on, a ConcurrentModificationException can happen. So then: public final Set<String> keys() { synchronized(map) { return new HashSet(map.keySet()); } } seems like the solution. Does this look right?

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  • problem with converting simple code from Winform to silverlight app.

    - by Sara
    Hi. I have this code for window form application and I have been attempting to convert it to a Silverlight application but it does not work!. There is a Textbox and I attached KeyDown event handler to it. when the user press the arrow key ( left or right) while the focus on the textbox, it will write . or -. When it is window form i used e.KeyCode and Keys.Right and its works great but when it is silverlight I used e.Key and key.Right and the program doesn't work good because the arrows do the 2 functions moving and write ./-. How I can work this out in Silverlight? (My English not good) The code ( window form): private void textBox1_KeyDown(object sender, KeyEventArgs e) { if (sender is TextBox) { TextBox textBox = (TextBox)sender; if (e.KeyCode == Keys.Left || e.KeyCode == Keys.Right) { e.Handled = true; char insert; if (e.KeyCode == Keys.Left) { insert = '.'; } else { insert = '-'; } int i = textBox.SelectionStart; textBox.Text = textBox.Text.Insert(i, insert.ToString()); textBox.Select(i + 1, 0); } } } (and Silverlight): private void textBox1_KeyDown(object sender, KeyEventArgs e) { if (sender is TextBox) { TextBox textBox = (TextBox)sender; if (e.Key == Key.Left || e.Key == Key.Right) { e.Handled = true; char insert; if (e.Key == Key.Left) { insert = '.'; } else { insert = '-'; } int i = textBox.SelectionStart; textBox.Text = textBox.Text.Insert(i, insert.ToString()); textBox.Select(i + 1, 0); } } } I don't understand, is there huge different effect between using Keycode/Keys and Key/Key or because something else?

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  • Rationale in selecting Hash Key type

    - by Amrish
    Guys, I have a data structure which has 25 distinct keys (integer) and a value. I have a list of these objects (say 50000) and I intend to use a hash table to store/retrieve them. I am planning to take one of these approaches. Create a integer hash from these 25 integer keys and store it on a hash table. (Yeah! I have some means to handle collisions) Make a string concatenation on the individual keys and use it as a hash key for the hash table. For example, if the key values are 1,2,4,6,7 then the hash key would be "12467". Assuming that I have a total of 50000 records each with 25 distinct keys and a value, then will my second approach be a overkill when it comes to the cost of string comparisons it needs to do to retrieve and insert a record? Some more information! Each bucket in the hash table is a balanced binary tree. I am using the boost library's hash_combine method to create the hash from the 25 keys.

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  • Understanding Security Certificates (and thier pricing)

    - by John Robertson
    I work at a very small company so certificate costs need to be absolutely minimal. However for some applications we do Need to have our customers get that warm fuzzy not-using-a-self-signed certificate feeling. Since creating a "certificate authority" with makecert really just means creating a public/private key pair, it seems pretty clear that creating a public/private key pair FROM such a "certificate authority" really just means generating a second public/private key pair and signing both with the private key that belongs to the "certificate authority". Since the keys are signed anyone can verify they came from the certificate authority I created, or if verisign gave me the pair they sign it with one of their own private keys, and anyone can use verisigns corresponding public key to confirm verisign as the source of the keys. Given this I don't understand when I go to verisign or godaddy why they have rates only for yearly plans, when all I really want from them is a single public/private key pair signed with one of their private keys (so that anyone else can use their public keys to confirm that, yes, they gave me that public/private key pair and they confirmed I was who I said I was so you can trust my public/private key pair as belonging to a legitimate third party). Clearly I am misunderstanding something, what is it? Does verisign retire their public/private key pairs periodically so that my verisign signed key pair "expires" and I need new ones?

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  • One-line expression to map dictionary to another

    - by No Such IP
    I have dictionary like d = {'user_id':1, 'user':'user1', 'group_id':3, 'group_name':'ordinary users'} and "mapping" dictionary like: m = {'user_id':'uid', 'group_id':'gid', 'group_name':'group'} All i want to "replace" keys in first dictionary with keys from second (e.g. replace 'user_id' with 'uid', etc.) I know that keys are immutable and i know how to do it with 'if/else' statement. But maybe there is way to do it in one line expression?

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  • Disable Foreign Key Exposure in Entity Framework?

    - by davemackey
    When I originally created a Dynamic Data project I told it to expose the foreign keys, but now I can't make mappings between two entities b/c of the foreign keys. When I click on mapping details while focused on my association I receive the message: Mappings are not allow for an association over exposed foreign keys. So I'd like to disable the exposure of the foreign keys but am unsure how to do this without creating a new Entity Model from scratch. I'm not far along - so that wouldn't be hard, but I imagine there must be a programmatic switch for this?

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  • Best keyboards for emacs?

    - by catphive
    For emacs users out there, what are your recommended keyboards? Bonus points for keyboards that: Have no capslock key. Instead, a control key in that position. Alt keys that are closer to the center, and easier to use with meta key combos. I find alt keys too far to the left to be a bit awkward to hit with my thumb in some key combos. Help ergonomically with emacs in other ways. I'm not a huge fan of model M style high and clacky keys. I instead prefer laptop style flat keys; however, I'm not disqualifying either category.

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  • How do I create a class in Javascript?

    - by William
    This is what I got so far, and it's not working at all :( <!DOCTYPE html> <html lang="en"> <head> <title>Class Test</title> <meta charset="utf-8" /> <style> body { text-align: center; background-color: #ffffff;} #box { position: absolute; left: 610px; top: 80px; height: 50px; width: 50px; background-color: #ff0000; color: #000000;} </style> <script type="text/javascript"> document.onkeydown=function(event){keyDown(event)}; document.onkeyup=function(event){keyUp(event)}; var box = 0; function Player () { var speed = 5; var x = 50; var y = 50; } function update() { box.style.left = this.x + "px"; box.style.top = this.y + "px"; box.innerHTML = "<h6 style=\"margin: 0px 0px 0px 0px; padding: 0px 0px 0px 0px;\">X: "+ this.x + "<br /> Y: " + this.y + "</h6>"; } var player = new Player(); var keys = new Array(256); var i = 0; for (i = 0;i <= 256; i++){ keys[i] = false; } function keyDown(event){ keys[event.keyCode] = true; } function keyUp(event){ keys[event.keyCode] = false; } function update(){ if(keys[37]) player.x -= player.speed; if(keys[39]) player.x += player.speed; player.update(); } setInterval(update, 1000/60); </script> </head> <body> <div id="box" ></div> <script type="text/javascript"> box = document.getElementById('box'); box.innerHTML = "<h6 style=\"margin: 0px 0px 0px 0px; padding: 0px 0px 0px 0px;\">X: "+ player.x + "<br /> Y: " + player.y + "</h6>"; </script> </body> </html>

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  • smarter "reverse" of a dictionary in python (acc for some of values being the same)?

    - by mrkafk
    def revert_dict(d): rd = {} for key in d: val = d[key] if val in rd: rd[val].append(key) else: rd[val] = [key] return rd >>> revert_dict({'srvc3': '1', 'srvc2': '1', 'srvc1': '2'}) {'1': ['srvc3', 'srvc2'], '2': ['srvc1']} This obviously isn't simple exchange of keys with values: this would overwrite some values (as new keys) which is NOT what I'm after. If 2 or more values are the same for different keys, keys are supposed to be grouped in a list. The above function works, but I wonder if there is a smarter / faster way?

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  • How to use a function for every C# WinForm instead of pasting .

    - by nXqd
    protected override bool ProcessCmdKey(ref Message msg, Keys keyData) { { if (keyData == Keys.Escape) this.Close(); return base.ProcessCmdKey(ref msg, keyData); } } I discovered this snippet to close windows form by esc. I really want to implement this to every windows form. I try to create a new abstract class which inherit from Form and another windows form will inherit from this one . But it doesn't work this way . abstract class AbsForm: Form { protected override bool ProcessCmdKey(ref Message msg, Keys keyData) { { if (keyData == Keys.Escape) this.Close(); return base.ProcessCmdKey(ref msg, keyData); } } } public partial class HoaDonBanSach : AbsForm { public HoaDonBanSach() { InitializeComponent(); } Thanks for reading this :)

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  • Memcached getDelayed alternative implementation

    - by iBobo
    I would like to use getDelayed on the PHP Memcached extension but I think it's not implemented in the right way. Right now you ask for some keys and then retrieve all of them with fetch() and fetchAll(). But imagine a scenario where I need to retrieve 15 keys used in different parts of the page which I don't know in advance, but I can ask the various objects to give me the list. What I want is give the Memcached instance this list (each component would give its part) then later when I need them retrieve from the instance, but not all of them at once: each component would take the one it needs. Basically if I were to implement this I would prohibit using getDelayed alone and implement a bookGet($keys) method where you would add the keys to book (which actually calls getDelayed), and redefine get to handle these three cases: key is booked and retrieved - return the value; key is booked but not retrieved - go and force the fetch of the booked keys and return the correct value; key not booked - do a normal lookup. I want to know if this makes sense, your thoughts on the subject and if someone already implemented this or maybe PECL Memcached already works this way and actually the documentation doesn't explain it correctly.

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  • c# ProcessCmdKey overload, match generic combination

    - by leo
    Hi all, On some control, I want ProcessCmdKey to return true if the keys pressed by the user were ALT and any letter of the alphabet. I'm able to return true if the user presses Alt with the following code, but how can I add the condition of a letter also pressed ? protected override bool ProcessCmdKey(ref Message msg, Keys keyData) { if ((keyData & Keys.Alt) != 0) { return true; } } Thanks.

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  • Best way to store this data?

    - by Malfist
    I have just been assigned to renovate an old website, and I get to move it from some old archaic system to drupal. The only problem is that it's a real-estate system and a lot of data is stored. Currently all the information is stored in a single table, an id represents the house and then everything else is key/value pairs. There are a possible 243 keys per estate, there are 23840 estates in the system. As you can imagine the system is slow and difficult to query. I don't think a table with 243 rows would be a very good idea, and probably worse than the current situation. I've done some investigating and here's what I've found out: Missing data does not indicate a 0 value, data is merged from two, unique sources/formats. Some guessing is involved. I have no control over the source of the data. There are 4 keys that are common to all estates, all values look like something that is commonly searched for and could be indexed There are 10 keys that are in the [90-100)% range 8 of these are information like who's selling it, and it's address. The other two seem to belong with the below range There are 80 keys that are in the [80-90)% range This range seems to mostly just list room types and how many the house has (e.g. bedrooms_possible, bathrooms, family_room_3rd, etc) This range also includes some minor information like school districts, one or two more pieces of data on the address. The 179 keys that are in the [0-80)% range include all sorts of miscellaneous information about the estate My best idea was a hybrid approach, create a table that stores important, common information and keep a smaller key/value table. How would you store this information?

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  • Memcached: booking a fetch

    - by iBobo
    I would like to use getDelayed on the PHP Memcached extension but I think it's not implemented in the right way. Right now you ask for some keys and then retrieve all of them with fetch() and fetchAll(). But imagine a scenario where I need to retrieve 15 keys used in different parts of the page which I don't know in advance, but I can ask the various objects to give me the list. What I want is give the Memcached instance this list (each component would give its part) then later when I need them retrieve from the instance, but not all of them at once: each component would take the one it needs. Basically if I were to implement this I would prohibit using getDelayed alone and implement a bookGet($keys) method where you would add the keys to book (which actually calls getDelayed), and redefine get to handle these three cases: key is booked and retrieved - return the value; key is booked but not retrieved - go and force the fetch of the booked keys and return the correct value; key not booked - do a normal lookup. I want to know if this makes sense, your thoughts on the subject and if someone already implemented this or maybe PECL Memcached already works this way and actually the documentation doesn't explain it correctly.

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  • Multiple key presses doing different events in C#

    - by Nevik Eeirnb
    Hi, private void Form1_KeyDown(object sender, KeyEventArgs e) { if (e.KeyCode == Keys.W) player1.moveUp(); if (e.KeyCode == Keys.NumPad8) player2.moveUp(); } In the above code the moveUp methods basically just increment a value. I want it so both keys can be pressed (or held down)at the same time and both events will trigger. Thanks, Nevik

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  • Why do dicts of defaultdict(int)'s use so much memory? (and other simple python performance question

    - by dukhat
    import numpy as num from collections import defaultdict topKeys = range(16384) keys = range(8192) table = dict((k,defaultdict(int)) for k in topKeys) dat = num.zeros((16384,8192), dtype="int32") print "looping begins" #how much memory should this use? I think it shouldn't use more that a few #times the memory required to hold (16384*8192) int32's (512 mb), but #it uses 11 GB! for k in topKeys: for j in keys: dat[k,j] = table[k][j] print "done" What is going on here? Furthermore, this similar script takes eons to run compared to the first one, and also uses an absurd quantity of memory. topKeys = range(16384) keys = range(8192) table = [(j,0) for k in topKeys for j in keys] I guess python ints might be 64 bit ints, which would account for some of this, but do these relatively natural and simple constructions really produce such a massive overhead? I guess these scripts show that they do, so my question is: what exactly is causing the high memory usage in the first script and the long runtime and high memory usage of the second script and is there any way to avoid these costs?

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