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  • How can I differentiate a manual scroll (via mousewheel/scrollbar) from a Javascript/jQuery scroll?

    - by David Murdoch
    UPDATE: Here is a jsbin example demonstrating the problem. Basically, I have the following javascript which scrolls the window to an anchor on the page: // get anchors with href's that start with "#" $("a[href^=#]").live("click", function(){ var target = $($(this).attr("href")); // if the target exists: scroll to it... if(target[0]){ // If the page isn't long enough to scroll to the target's position // we want to scroll as much as we can. This part prevents a sudden // stop when window.scrollTop reaches its maximum. var y = Math.min(target.offset().top, $(document).height() - $(window).height()); // also, don't try to scroll to a negative value... y=Math.max(y,0); // OK, you can scroll now... $("html,body").stop().animate({ "scrollTop": y }, 1000); } return false; }); It works perfectly......until I manually try to scroll the window. When the scrollbar or mousewheel is scrolled I need to stop the current scroll animation...but I'm not sure how to do this. This is probably my starting point... $(window).scroll(e){ if(IsManuallyScrolled(e)){ $("html,body").stop(); } } ...but I'm not sure how to code the IsManuallyScrolled function. I've checked out e (the event object) in Google Chrome's console and AFAIK there is not way to differentiate between a manual scroll and jQuery's animate() scroll. How can I differentiate between a manual scroll and one called via jQuery's $.fn.animate function?

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  • W3C error doc error? Output tag browser support.

    - by ThomasReggi
    Was looking at the reference page here : http://www.w3.org/TR/html5/offline.html I copied and pasted the code on my server here in separate files. All of the pages are linked correctly but the clock won't show. Just to double check, it wasn't my "server config" I put it on jsfiddle.net here: http://jsfiddle.net/reggi/Dy8PU/. Fails: MAC / FIREFOX 3.6.13 Wins: MAC / FIREFOX 4.0.b8 Is this dummy example code? <!-- clock.html --> <!DOCTYPE HTML> <html> <head> <title>Clock</title> <script src="clock.js"></script> <link rel="stylesheet" href="clock.css"> </head> <body> <p>The time is: <output id="clock"></output></p> </body> </html> /* clock.css */ output { font: 2em sans-serif; } /* clock.js */ setTimeout(function () { document.getElementById('clock').value = new Date(); }, 1000); UPDATE: The W3C code above works on only the NEWEST Beta releases of certain browsers Below are some viable current javascript workarounds

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  • C++: select argmax over vector of classes w.r.t. arbitrary expression

    - by karpathy
    Hello, I have trouble describing my problem so I'll give an example: I have a class description that has a couple of variables in it, for example: class A{ float a, b, c, d; } Now, I maintain a vector<A> that contains many of these classes. What I need to do very very often is to find the object inside this vector that satisfies that one of it's parameters is maximal w.r.t to the others. i.e code looks something like: int maxi=-1; float maxa=-1000; for(int i=0;i<vec.size();i++){ res= vec[i].a; if(res > maxa) { maxa= res; maxi=i; } } return vec[maxi]; However, sometimes I need to find class with maximal a, sometimes with maximal b, sometimes the class with maximal 0.8*a + 0.2*b, sometimes I want a maximal a*VAR + b, where VAR is some variable that is assigned in front, etc. In other words, I need to evaluate an expression for every class, and take the max. I find myself copy-pasting this everywhere, and only changing the single line that defines res. What makes it even more complicated is that even the name of the vector changes. Sometimes it's vec, sometimes it can be something else. I have many vectors that contain A's. This could be changed if this makes the problem too hard. Is there some nice way to avoid this insanity in C++? What's the neatest way to handle this? Thank you!

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  • SQL Server compare table entries for update

    - by Dave
    I have a trade table with several million rows. Each row represents the version of a trade. If I'm given a possibly new trade I compare it to the latest version in the trade table. If it has changed I add a new version, otherwise I do nothing. In order to compare the 2 trades I read the version from the trade table into my application. This doesn't work well when I'm given 10s of thousands of possibly new trades. Even batching reads to read in a 1000 trades at once and compare them the whole process can take several minutes. All the time is spent in the DB. I'm trying to find a way to compare the possibly new trades to the ones in the trade table without so much I/O. What I've come up with so far is adding a hash column to each row in the trade table. The hash is of all the trade fields. Then when I'm given possibly new trades I compute their hash, put the values into a temporary table, then find ones that are different. This feels very hacky. Is there a better way of doing it? Thanks

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  • Efficient algorithm for Next button on a MySQL result set

    - by David Grayson
    I have a website that lets people view rows in a table (each row is a picture). There are more than 100,000 rows. You can view different subsets of the rows, and you can view them with different sort orders. While you are viewing one of the rows, you can click the "Next" or "Previous" buttons to go the next/previous row in the list. How would you implement the "Next" and "Previous" features of the website? More specifically, if you have an arbitrary query that returns a list of up to 100,000+ rows, and you know some information about the current row someone is viewing, how do you determine the NEXT row efficiently? Here is the pseudo-code of the solution I came up with when the website was young, and it worked well when there were only 1000 rows, but now that there are 100,000 rows I think it is eating up too much memory. int nextRowId(string query, int currentRowId) { array allRowIds = mysql_query(query); // Takes up a lot of memory! int currentIndex = (index of currentRowId in allRowIds); // Takes time! return allRowIds[currentIndex+1]; } While you are thinking about this problem, remember that the website can store more information about the current row than just its ID (for example, the position of the current row in the result set), and this information can be used as a hint to help determine the ID of the next row. Edit: Sorry for not mentioning this earlier, but this isn't just a static website: rows can often be added to the list, and rows can be re-ordered in the list. (Much rarer, rows can be removed from the list.) I think that I should worry about that kind of thing, but maybe you can convince me otherwise.

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  • In Corona SDK the background image always cover other images

    - by user1446126
    I'm currently making a tower defense game with Corona SDK. However, while I'm making the gaming scene, The background scene always cover the monster spawn, I've tried background:toBack() ,however it's doesn't work.Here is my code: module(..., package.seeall) function new() local localGroup = display.newGroup(); local level=require(data.levelSelected); local currentDes = 1; monsters_list = display.newGroup() --The background local bg = display.newImage ("image/levels/1/bg.png"); bg.x = _W/2;bg.y = _H/2; bg:toBack(); --generate the monsters function spawn_monster(kind) local monster=require("monsters."..kind); newMonster=monster.new() --read the spawn(starting point) in level, and spawn the monster there newMonster.x=level.route[1][1];newMonster.y=level.route[1][2]; monsters_list:insert(newMonster); localGroup:insert(monsters_list); return monsters_list; end function move(monster,x,y) -- Using pythagoras to calauate the moving distace, Hence calauate the time consumed according to speed transition.to(monster,{time=math.sqrt(math.abs(monster.x-x)^2+math.abs(monster.y-y)^2)/(monster.speed/30),x=x, y=y, onComplete=newDes}) end function newDes() currentDes=currentDes+1; end --moake monster move according to the route function move_monster() for i=1,monsters_list.numChildren do move(monsters_list[i],200,200); print (currentDes); end end function agent() spawn_monster("basic"); end --Excute function above. timer2 = timer.performWithDelay(1000,agent,10); timer.performWithDelay(100,move_monster,-1); timer.performWithDelay(10,update,-1); move_monster(); return localGroup; end and the monster just stuck at the spawn point and stay there. but, When i comment these 3 lines of code: --local bg = display.newImage ("image/levels/1/bg.png"); --bg.x = _W/2;bg.y = _H/2; --bg:toBack(); The problem disappear Any ideas??Thanks for helping

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  • Producer consumer with qualifications

    - by tgguy
    I am new to clojure and am trying to understand how to properly use its concurrency features, so any critique/suggestions is appreciated. So I am trying to write a small test program in clojure that works as follows: there 5 producers and 2 consumers a producer waits for a random time and then pushes a number onto a shared queue. a consumer should pull a number off the queue as soon as the queue is nonempty and then sleep for a short time to simulate doing work the consumers should block when the queue is empty producers should block when the queue has more than 4 items in it to prevent it from growing huge Here is my plan for each step above: the producers and consumers will be agents that don't really care for their state (just nil values or something); i just use the agents to send-off a "consumer" or "producer" function to do at some time. Then the shared queue will be (def queue (ref [])). Perhaps this should be an atom though? in the "producer" agent function, simply (Thread/sleep (rand-int 1000)) and then (dosync (alter queue conj (rand-int 100))) to push onto the queue. I am thinking to make the consumer agents watch the queue for changes with add-watcher. Not sure about this though..it will wake up the consumers on any change, even if the change came from a consumer pulling something off (possibly making it empty) . Perhaps checking for this in the watcher function is sufficient. Another problem I see is that if all consumers are busy, then what happens when a producer adds something new to the queue? Does the watched event get queued up on some consumer agent or does it disappear? see above I really don't know how to do this. I heard that clojure's seque may be useful, but I couldn't find enough doc on how to use it and my initial testing didn't seem to work (sorry don't have the code on me anymore)

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  • Any solution to IE8 bug rendering error when hiding elements?

    - by Magnar
    Bug: when hiding an element with JavaScript in IE8, the margin of still-visible other elements on the side is ignored. This bug has been introduced with IE8, since it works as expected in IE6+7 (and other browsers). <html> <head> <style> #a, #b, #c, #d {background: #ccf; padding: 4px; margin-bottom: 8px;} </style> </head> <body> <div id="a">a</div> <div id="b">b</div> <div id="c">c</div> <div id="d">d</div> <script> setTimeout(function () { document.getElementById("b").style.display = "none"; }, 1000); </script> </body> </html> When running this code, notice how a and c have a margin of 8 between them in normal browsers, but a margin of 0 in IE8. Remove the padding, and IE8 behaves like normal. Remove the timeout and IE8 behaves like normal. A border behaves the same way. I've been working with IE-bugs the last 10 years, but this has me stumped. The solution for now is to wrap the divs, and apply the margin to the outer element and other styles to the inner. But that's reminicent of horrible IE6-workarounds. Any better solutions?

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  • Lights off effect and jquery placement on wordpress

    - by Alexander Santiago
    I'm trying to implement a lights on/off on single posts of my wordpress theme. I know that I have to put this code on my css, which I did already: #the_lights{ background-color:#000; height:1px; width:1px; position:absolute; top:0; left:0; display:none; } #standout{ padding:5px; background-color:white; position:relative; z-index:1000; } Now this is the code that I'm having trouble with: function getHeight() { if ($.browser.msie) { var $temp = $("").css("position", "absolute") .css("left", "-10000px") .append($("body").html()); $("body").append($temp); var h = $temp.height(); $temp.remove(); return h; } return $("body").height(); } $(document).ready(function () { $("#the_lights").fadeTo(1, 0); $("#turnoff").click(function () { $("#the_lights").css("width", "100%"); $("#the_lights").css("height", getHeight() + "px"); $("#the_lights").css({‘display’: ‘block’ }); $("#the_lights").fadeTo("slow", 1); }); $("#soft").click(function () { $("#the_lights").css("width", "100%"); $("#the_lights").css("height", getHeight() + "px"); $("#the_lights").css("display", "block"); $("#the_lights").fadeTo("slow", 0.8); }); $("#turnon").click(function () { $("#the_lights").css("width", "1px"); $("#the_lights").css("height", "1px"); $("#the_lights").css("display", "block"); $("#the_lights").fadeTo("slow", 0); }); }); I think it's a jquery. Where do I place it and how do I call it's function? Been stuck on this thing for 6 hours now and any help would be greatly appreciated...

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  • How can I remove a JPanel from a JFrame?

    - by Roman
    Recently I asked here how to add a new JPanel to JFrame. The answer helped me to get a working code. But not I have a related question: "How can I remove an old JPanel". I need that because of the following problem. A new JPanel appears appears when I want (either time limit is exceeded or user press the "Submit" button). But in several seconds some element of the old JPanel appears together with the component of the new JPanel. I do not understand why it happens. I thought that it is because I have to other threads which update the window. But the first thread just add the old panel once (so, it should be finished). And in the second thread I have a loop which is broken (so, it also should be finished). Here is my code: private Thread controller = new Thread() { public void run() { // First we set the initial pane (for the selection of partner). SwingUtilities.invokeLater(new Runnable() { public void run() { frame.getContentPane().add(generatePartnerSelectionPanel()); frame.invalidate(); frame.validate(); } }); // Update the pane for the selection of the parnter. for (int i=40; i>0; i=i-1) { final int sec = i; SwingUtilities.invokeLater(new Runnable() { public void run() { timeLeftLabel.setText(sec + " seconds left."); } }); try {Thread.sleep(1000);} catch (InterruptedException e) {} if (partnerSubmitted) {break;} } // For the given user the selection phase is finished (either the time is over or form was submitted). SwingUtilities.invokeLater(new Runnable() { public void run() { frame.getContentPane().add(generateWaitForGamePanel()); frame.invalidate(); frame.validate(); } }); } };

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  • .NET MissingMethodException occuring on one of thousands of end-user machines -- any insight?

    - by Yoooder
    This issue has me baffled, it's affecting a single user (to my knowledge) and hasn't been reproduced by us... The user is receiving a MissingMethodException, our trace file indicates it's occuring after we create a new instance of a component, when we're calling an Initialize/Setup method in preparation to have it do work (InitializeWorkerByArgument in the example) The Method specified by the error is an interface method, which a base class implements and classes derived from the base class can override as-needed The user has the latest release of our application All the provided code is shipped within a single assembly Here's a very distilled version of the component: class Widget : UserControl { public void DoSomething(string argument) { InitializeWorkerByArgument(argument); this.Worker.DoWork(); } private void InitializeWorkerByArgument(string argument) { switch (argument) { case "SomeArgument": this.Worker = new SomeWidgetWorker(); break; } // The issue I'm tracking down would have occured during "new SomeWidgetWorker()" // and would have resulted in a missing method exception stating that // method "DoWork" could not be found. this.Worker.DoWorkComplete += new EventHandler(Worker_DoWorkComplete); } private IWidgetWorker Worker { get; set; } void Worker_DoWorkComplete(object sender, EventArgs e) { MessageBox.Show("All done"); } } interface IWidgetWorker { void DoWork(); event EventHandler DoWorkComplete; } abstract class BaseWorker : IWidgetWorker { virtual public void DoWork() { System.Threading.Thread.Sleep(1000); RaiseDoWorkComplete(this, null); } internal void RaiseDoWorkComplete(object sender, EventArgs e) { if (DoWorkComplete != null) { DoWorkComplete(this, null); } } public event EventHandler DoWorkComplete; } class SomeWidgetWorker : BaseWorker { public override void DoWork() { System.Threading.Thread.Sleep(2000); RaiseDoWorkComplete(this, null); } }

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  • Most "thorough" distribution of points around a circle

    - by hippietrail
    This question is intended to both abstract and focus one approach to my problem expressed at "Find the most colourful image in a collection of images". Imagine we have a set of circles, each has a number of points around its circumference. We want to find a metric that gives a higher rating to a circle with points distributed evenly around the circle. Circles with some points scattered through the full 360° are better but circles with far greater numbers of points in one area compared to a smaller number in another area are less good. The number of points is not limited. Two or more points may coincide. Coincidental points are still relevant. A circle with one point at 0° and one point at 180° is better than a circle with 100 points at 0° and 1000 points at 180°. A circle with one point every degree around the circle is very good. A circle with a point every half degree around the circle is better. In my other (colour based question) it was suggested that standard deviation would be useful but with caveat. Is this a good suggestion and does it cope with the closeness of 359° to 1°?

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  • Mootools Javascript can't push to array

    - by nona
    I have an array set with the heights of each hidden div, but when I use it, the div instantly jumps down, rather than slowly sliding as when there is a literal number. EDIT: testing seems to reveal that it's a problem with the push method, as content_height.push(item.getElement('.moreInfo').offsetHeight);alert(content_height[i]);gives undefined, but alert(item.getElement('.moreInfo').offsetHeight); gives the correct values Javascript: window.addEvent('domready', function(){ var content_height = [];i=0; $$( '.bio_accordion' ).each(function(item){ i++; content_height.push( item.getElement('.moreInfo').offsetHeight); var thisSlider = new Fx.Slide( item.getElement( '.moreInfo' ), { mode: 'horizontal' } ); thisSlider.hide(); item.getElement('.moreInfo').set('tween').tween('height', '0px'); var morph = new Fx.Morph(item.getElement( '.divToggle' )); var selected = 0; item.getElement( '.divToggle' ).addEvents({ 'mouseenter': function(){ if(!selected) this.morph('.div_highlight'); }, 'mouseleave': function(){ if(!selected) { this.morph('.divToggle'); } }, 'click': function(){ if (!selected){ if (this.getElement('.symbol').innerHTML == '+') this.getElement('.symbol').innerHTML = '-'; else this.getElement('.symbol').innerHTML = '+'; item.getElement('.moreInfo').set('tween', { duration: 1500, transition: Fx.Transitions.Bounce.easeOut }).tween('height', content_height[i]); //replacing this with '650' keeps it smooth selected = 1; thisSlider.slideIn(); } else{ if (this.getElement('.symbol').innerHTML == '+') this.getElement('.symbol').innerHTML = '-'; else this.getElement('.symbol').innerHTML = '+'; thisSlider.slideOut(); item.getElement('.moreInfo').set('tween', { duration: 1000, transition: Fx.Transitions.Bounce.easeOut }).tween('height', '0px'); selected = 0; } } }); } ); }); Why could this be? Thanks so much!

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  • Problem using the prependTo() in jQuery

    - by raulriera
    Hi all, I am having a problem trying to use the prependTo() function in jQuery... for some reason I can't get this to work $(" <div id="note178" class="note"> <div class="delete"><a href="/chart-notes/delete/178" onclick="$.ajax({ dataType: 'script', url: '/chart-notes/delete/178'}); return false;"><img src='/images/icons/delete.png'></a></div> <div class="timestamp">1 minute ago </div> <div class="content">ñasdas dasdasdasd conclusión</div> </div> ").prependTo(".notes").fadeIn("slow"); Although when doing it like this, it works fine $.ajax({ url:'/chart-notes/show/<cfoutput>#chartnote.id#</cfoutput>', success: function(data) { $(data).prependTo(".notes").fadeIn("slow"); // Scroll to the top of the annotations $('html, body').animate({scrollTop: $(".notes").offset().top}, 1000); // Clear the form $('#chartnote-notes').val(""); } }); The "data" response from that success function is the same <div id="note178" class="note"> <div class="delete"><a href="/chart-notes/delete/178" onclick="$.ajax({ dataType: 'script', url: '/chart-notes/delete/178'}); return false;"><img src='/images/icons/delete.png'></a></div> <div class="timestamp">1 minute ago </div> <div class="content">ñasdas dasdasdasd conclusión</div> </div> As before

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  • Python: Created nested dictionary from list of paths

    - by sberry2A
    I have a list of tuples the looks similar to this (simplified here, there are over 14,000 of these tuples with more complicated paths than Obj.part) [ (Obj1.part1, {<SPEC>}), (Obj1.partN, {<SPEC>}), (ObjK.partN, {<SPEC>}) ] Where Obj goes from 1 - 1000, part from 0 - 2000. These "keys" all have a dictionary of specs associated with them which act as a lookup reference for inspecting another binary file. The specs dict contains information such as the bit offset, bit size, and C type of the data pointed to by the path ObjK.partN. For example: Obj4.part500 might have this spec, {'size':32, 'offset':128, 'type':'int'} which would let me know that to access Obj4.part500 in the binary file I must unpack 32 bits from offset 128. So, now I want to take my list of strings and create a nested dictionary which in the simplified case will look like this data = { 'Obj1' : {'part1':{spec}, 'partN':{spec} }, 'ObjK' : {'part1':{spec}, 'partN':{spec} } } To do this I am currently doing two things, 1. I am using a dotdict class to be able to use dot notation for dictionary get / set. That class looks like this: class dotdict(dict): def __getattr__(self, attr): return self.get(attr, None) __setattr__ = dict.__setitem__ __delattr__ = dict.__delitem__ The method for creating the nested "dotdict"s looks like this: def addPath(self, spec, parts, base): if len(parts) > 1: item = base.setdefault(parts[0], dotdict()) self.addPath(spec, parts[1:], item) else: item = base.setdefault(parts[0], spec) return base Then I just do something like: for path, spec in paths: self.lookup = dotdict() self.addPath(spec, path.split("."), self.lookup) So, in the end self.lookup.Obj4.part500 points to the spec. Is there a better (more pythonic) way to do this?

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  • need help with Java solution /newbie

    - by Racket
    Hi, I'm new to programming in general so i'm trying to be as specific as possible in this question. There's this book that i'm doing some exercises on. I managed to do more than half of what they say, but it's just one input that I have been struggling to find out. I'll write the question and thereafter my code, "Write an application that creates and prints a random phone number of the form XXX-XXX-XXXX. Include the dashes in the output. Do not let the first three digits contain an 8 or 9 (but don't be more restrictive than that), and make sure that the second set of three digits is not greater than 742. Hint: Think through the easiest way to construct the phone number. Each diigit does not have to be determined separately." OK, the highlighted sentence is what i'm looking at. Here's my code: import java.util.Random; public class PP33 { public static void main (String[] args) { Random rand = new Random(); int num1, num2, num3; num1 = rand.nextInt(900) + 100; num2 = rand.nextInt(643) + 100; num3 = rand.nextInt(9000) + 1000; System.out.println(num1+"-"+num2+"-"+num3); } } How am I suppose to do this? I'm on chapter 3 so we have not yet discussed if statements etcetera, but Aliases, String class, Packages, Import declaration, Random Class, Math Class, Formatting output (decimal- & numberFormat), Printf, Enumeration & Wrapper classes + autoboxing. So consider answer the question based only on these assumptions, please. The code doesn't have any errors. Thank you!

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  • jquery plugin caroufredsel hide next/prev buttons until mouseover carousel

    - by John Magnolia
    I am trying to make the buttons hide by default and they only become visible when the mouse is over. Although I am having problems where the carousel core code seems to be adding display block even if I set display none in the CSS. var $slides = $("#slides"); $slides.find('ul.banners').eq(0).carouFredSel({ height: 360, items: { visible: 1 }, scroll: { easing: "easeInOutSine", duration: 1200 }, auto: { delay: 1000 }, prev: { button: $slides.find('.prev'), items: 1 }, next:{ button: $slides.find('.next'), items: 1 }, pagination: { container: $slides.find(".pagination"), keys: true, anchorBuilder: function(nr) { return '<li><a href="#"><span>'+nr+'</span></a></li>'; } } }); $slideButtons = $slides.find(".next,.prev"); $slides.find('ul.banners').hover(function(){ $slideButtons.fadeIn(); },function(){ $slideButtons.fadeOut(); }); HTML <div id="slides"> <ul class="banners"> <li><img /></li> <li><img /></li> </ul> <ul class="pagination"></ul> <div class="next">Next</div> <div class="prev">Previous</div> </div>

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  • forms problem in django 1.1

    - by alexarsh
    I have the following form: class ModuleItemForm2(forms.ModelForm): class Meta: model = Module_item fields = ('title', 'media', 'thumb', 'desc', 'default', 'player_option') The model is: class Module_item(models.Model): title = models.CharField(max_length=100) layout = models.CharField(max_length=5, choices=LAYOUTS_CHOICE) media = models.CharField(help_text='Media url', max_length=500, blank=True, null=True) conserv = models.ForeignKey(Conserv, help_text= 'Redirect to Conserv', blank=True, null=True) conserve_section = models.CharField(max_length=100, help_text= 'Section within the redirected Conserv', blank=True, null=True) parent = models.ForeignKey('self', help_text='Upper menu.', blank=True, null=True) module = models.ForeignKey(Module, blank=True, null=True) thumb = models.FileField(upload_to='sms/module_items/thumbs', blank=True, null=True) desc = models.CharField(max_length=500, blank=True, null=True) auto_play = models.IntegerField(help_text='Auto start play (miliseconds)', blank=True, null=True) order = models.IntegerField(help_text='Display order', blank=True, null=True) depth = models.IntegerField(help_text='The layout depth', blank=True, null=True) flow_replace = models.IntegerField(blank=True, null=True) default = models.IntegerField(help_text='The selected sub item (Note: Starting from 0)', blank=True, null=True) player_options = models.CharField(max_length=1000, null=True, blank=True) In my view I build form: module_item_form2 = ModuleItemForm2() print module_item_form2 And I get the following error on the print line: 'NoneType' object has no attribute 'label' It works fine with django 1.0.2. I see the error only in django 1.1. Do you have an idea what am I doing wrong? Regards, Arshavski Alexander.

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  • Thread-safety of read-only memory access

    - by Edmund
    I've implemented the Barnes-Hut gravity algorithm in C as follows: Build a tree of clustered stars. For each star, traverse the tree and apply the gravitational forces from each applicable node. Update the star velocities and positions. Stage 2 is the most expensive stage, and so is implemented in parallel by dividing the set of stars. E.g. with 1000 stars and 2 threads, I have one thread processing the first 500 stars and the second thread processing the second 500. In practice this works: it speeds the computation by about 30% with two threads on a two-core machine, compared to the non-threaded version. Additionally, it yields the same numerical results as the original non-threaded version. My concern is that the two threads are accessing the same resource (namely, the tree) simultaneously. I have not added any synchronisation to the thread workers, so it's likely they will attempt to read from the same location at some point. Although access to the tree is strictly read-only I am not 100% sure it's safe. It has worked when I've tested it but I know this is no guarantee of correctness! Questions Do I need to make a private copy of the tree for each thread? Even if it is safe, are there performance problems of accessing the same memory from multiple threads?

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  • Fastest inline-assembly spinlock

    - by sigvardsen
    I'm writing a multithreaded application in c++, where performance is critical. I need to use a lot of locking while copying small structures between threads, for this I have chosen to use spinlocks. I have done some research and speed testing on this and I found that most implementations are roughly equally fast: Microsofts CRITICAL_SECTION, with SpinCount set to 1000, scores about 140 time units Implementing this algorithm with Microsofts InterlockedCompareExchange scores about 95 time units Ive also tried to use some inline assembly with __asm {} using something like this code and it scores about 70 time units, but I am not sure that a proper memory barrier has been created. Edit: The times given here are the time it takes for 2 threads to lock and unlock the spinlock 1,000,000 times. I know this isn't a lot of difference but as a spinlock is a heavily used object, one would think that programmers would have agreed on the fastest possible way to make a spinlock. Googling it leads to many different approaches however. I would think this aforementioned method would be the fastest if implemented using inline assembly and using the instruction CMPXCHG8B instead of comparing 32bit registers. Furthermore memory barriers must be taken into account, this could be done by LOCK CMPXHG8B (I think?), which guarantees "exclusive rights" to the shared memory between cores. At last [some suggests] that for busy waits should be accompanied by NOP:REP that would enable Hyper-threading processors to switch to another thread, but I am not sure whether this is true or not? From my performance-test of different spinlocks, it is seen that there is not much difference, but for purely academic purpose I would like to know which one is fastest. However as I have extremely limited experience in the assembly-language and with memory barriers, I would be happy if someone could write the assembly code for the last example I provided with LOCK CMPXCHG8B and proper memory barriers in the following template: __asm { spin_lock: ;locking code. spin_unlock: ;unlocking code. }

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  • Java Concurrency in practice sample question

    - by andy boot
    I am reading "Java Concurrency in practice" and looking at the example code on page 51. This states that if a thread has references to a shared object then other threads may be able to access that object before the constructor has finished executing. I have tried to put this into practice and so I wrote this code thinking that if I ran it enough times a RuntimeException("World is f*cked") would occur. But it isn't doing. Is this a case of the Java spec not guaranting something but my particular implementation of java guaranteeing it for me? (java version: 1.5.0 on Ubuntu) Or have I misread something in the book? Code: (I expect an exception but it is never thrown) public class Threads { private Widgit w; public static void main(String[] s) throws Exception { while(true){ Threads t = new Threads(); t.runThreads(); } } private void runThreads() throws Exception{ new Checker().start(); w = new Widgit((int)(Math.random() * 100) + 1); } private class Checker extends Thread{ private static final int LOOP_TIMES = 1000; public void run() { int count = 0; for(int i = 0; i < LOOP_TIMES; i++){ try { w.checkMe(); count++; } catch(NullPointerException npe){ //ignore } } System.out.println("checked: "+count+" times out of "+LOOP_TIMES); } } private static class Widgit{ private int n; private int n2; Widgit(int n) throws InterruptedException{ this.n = n; Thread.sleep(2); this.n2 = n; } void checkMe(){ if (n != n2) { throw new RuntimeException("World is f*cked"); } } } }

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  • Summarising grouped records in a dataframe in R

    - by monch1962
    Hello all, I have a data frame in R that looks like this: > TimeOffset, Source, Length > 0 1 1500 > 0.1 1 1000 > 0.2 1 50 > 0.4 2 25 > 0.6 2 3 > 1.1 1 1500 > 1.4 1 18 > 1.6 2 2500 > 1.9 2 18 > 2.1 1 37 > ... and I want to convert it to > TimeOffset, Source, Length > 0.2 1 2550 > 0.6 2 28 > 1.4 1 1518 > 1.9 2 2518 > ... Trying to put this into English, I want to group consecutive records with the same 'Source' together, then printing out a single record per group showing the highest time offset in that group, the source, and the sum of the lengths in that group. The TimeOffset values will always increase. I suspect this is possible in R, but I really don't know where to start. In a pinch I could export the data frame out and do it in e.g. Python, but I'd prefer to stay within R if possible. Thanks in advance for any assistance you can provide

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  • Checking if a console application is still running using the Process class

    - by Ced
    I'm making an application that will monitor the state of another process and restart it when it stops responding, exits, or throws an error. However, I'm having trouble to make it reliably check if the process (Being a C++ Console window) has stopped responding. My code looks like this: public void monitorserver() { while (true) { server.StartInfo = new ProcessStartInfo(textbox_srcdsexe.Text, startstring); server.Start(); log("server started"); log("Monitor started."); while (server.Responding) { if (server.HasExited) { log("server exitted, Restarting."); break; } log("server is running: " + server.Responding.ToString()); Thread.Sleep(1000); } log("Server stopped responding, terminating.."); try { server.Kill(); } catch (Exception) { } } } The application I'm monitoring is Valve's Source Dedicated Server, running Garry's Mod, and I'm over stressing the physics engine to simulate it stopping responding. However, this never triggers the process class recognizing it as 'stopped responding'. I know there are ways to directly query the source server using their own protocol, but i'd like to keep it simple and universal (So that i can maybe use it for different applications in the future). Any help appreciated

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  • PHP/XPath: Iterating through ancestor nodes in XML using SimpleXML

    - by StackOverflowNewbie
    I need to loop through the Ancestors nodes in order to get corresponding BrowseNodeId and Name values. How do I do this using XPath? I'm trying something like the the following, but it's not working: //BrowseNode[1]//Ancestors[1]/BrowseNode/BrowseNodeId/text() //BrowseNode[1]//Ancestors[1]/BrowseNode/Name/text() I think the //Ancestors part of the XPath is actually searching the entire XML tree. What I need to do is visit each node to get the needed values. How do I do this? In the example below, I want: Europe - History - Subjects - Books. Example XML: <BrowseNode> <BrowseNodeId>4952</BrowseNodeId> <Name>France</Name> <Ancestors> <BrowseNode> <BrowseNodeId>4935</BrowseNodeId> <Name>Europe</Name> <Ancestors> <BrowseNode> <BrowseNodeId>9</BrowseNodeId> <Name>History</Name> <Ancestors> <BrowseNode> <BrowseNodeId>1000</BrowseNodeId> <Name>Subjects</Name> <IsCategoryRoot>1</IsCategoryRoot> <Ancestors> <BrowseNode> <BrowseNodeId>283155</BrowseNodeId> <Name>Books</Name> </BrowseNode> </Ancestors> </BrowseNode> </Ancestors> </BrowseNode> </Ancestors> </BrowseNode> </Ancestors> </BrowseNode>

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  • Rails wont install at create Makefile stage

    - by mattc
    I am getting this error after running sudo gem install rails /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/ruby extconf.rb creating Makefile make xcrun cc -I. - I/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/universal-darwin12.0 -I/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/universal-darwin12.0 -I. -DJSON_GENERATOR -D_XOPEN_SOURCE -D_DARWIN_C_SOURCE -fno-common -arch i386 -arch x86_64 -g -O3 -pipe -fno-common -DENABLE_DTRACE -fno-common -pipe -fno-common -c generator.c xcrun: Error: failed to exec real xcrun. (No such file or directory) cc -arch i386 -arch x86_64 -pipe -bundle -undefined dynamic_lookup -o generator.bundle generator.o -L. -L/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib -L. -arch i386 -arch x86_64 -lruby -lpthread -ldl -lobjc i686-apple-darwin11-llvm-gcc-4.2: generator.o: No such file or directory i686-apple-darwin11-llvm-gcc-4.2: generator.o: No such file or directory lipo: can't figure out the architecture type of: /var/tmp//ccHCNNwM.out make: *** [generator.bundle] Error 1 I have Homebrew installed, Xcode 4.4 with command line tools installed, Osx 10.6.2 I run gem env and get this but not sure what I'm looking for: RubyGems Environment: - RUBYGEMS VERSION: 1.8.24 - RUBY VERSION: 1.8.7 (2012-02-08 patchlevel 358) [universal-darwin12.0] - INSTALLATION DIRECTORY: /Library/Ruby/Gems/1.8 - RUBY EXECUTABLE: /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/ruby - EXECUTABLE DIRECTORY: /usr/bin - RUBYGEMS PLATFORMS: - ruby - universal-darwin-12 - GEM PATHS: - /Library/Ruby/Gems/1.8 - /Users/matthewcleghorn/.gem/ruby/1.8 - /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/gems/1.8 - GEM CONFIGURATION: - :update_sources => true - :verbose => true - :benchmark => false - :backtrace => false - :bulk_threshold => 1000 - REMOTE SOURCES: - http://rubygems.org/ Any help greatly appreciated. Thanks.

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