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  • Doctrine2 - relationship

    - by Filip Golonka
    I'm developing an application, which is looking for optimal route and timetable in public transport. I have some experience about Doctrine1, but it's my first time with Doctrine2. There is soem new fields to describe relations (mappedBy and inversedBy) and also some new ways of mapping. I have following code: $query = $this->em->createQuery("SELECT partial cls.{stop}, partial t.{arriveTime, departureTime} FROM \Entities\Timetable t JOIN t.ride r JOIN t.carrierLineStop cls WHERE t.departureTime>=:time AND r.idCarrierLine=:carrierLine AND (cls.idStop=:firstStop OR cls.idStop=:lastStop)"); $query->setParameters(array( 'time' => $time, 'carrierLine' => $path->getLine(), 'firstStop' => $path->getFirstStop(), 'lastStop' => $path->getLastStop() )); When I try to execute that script I've got an error: [Semantical Error] line 0, col 24 near '}, partial t.{arriveTime,': Error: There is no mapped field named 'stop' on class Entities\CarrierLineStop. Mapping files: Entities\CarrierLineStop: type: entity table: carrier_line_stop fields: idCarrierLineStop: id: true type: integer unsigned: false nullable: false column: id_carrier_line_stop generator: strategy: IDENTITY nextStop: type: integer unsigned: false nullable: true column: next_stop manyToOne: idCarrierLine: targetEntity: Entities\CarrierLine cascade: { } mappedBy: null inversedBy: null joinColumns: id_carrier_line: referencedColumnName: id_carrier_line orphanRemoval: false stop: column: id_stop targetEntity: Entities\Stop cascade: { } mappedBy: null inversedBy: carrierLineStop joinColumns: id_stop: referencedColumnName: id_stop orphanRemoval: false lifecycleCallbacks: { } - Entities\Stop: type: entity table: stop fields: idStop: id: true type: integer unsigned: false nullable: false column: id_stop generator: strategy: IDENTITY name: type: string length: 45 fixed: false nullable: true miejscowosc: type: string length: 45 fixed: false nullable: true latitude: type: decimal nullable: true longitude: type: decimal nullable: true oneToMany: carrierLineStop: targetEntity: Entities\CarrierLineStop cascade: { } mappedBy: stop inversedBy: null joinColumns: id_stop: referencedColumnName: id_stop orphanRemoval: false lifecycleCallbacks: { } I have no idea about where the problem is...

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  • Ruby Challenge - efficiently change the last character of every word in a sentence to a capital

    - by emson
    Hi All I recently was challenged to write some Ruby code to change the last character of every word in a sentence into a capital. Such that the string: "script to convert the last letter of every word to a capital" becomes "scripT tO converT thE lasT letteR oF everY worD tO A capitaL" This was my optimal solution however I'm sure you wizards have much better solutions and I would be really interested to hear them. "script to convert the last letter of every word to a capital".split.map{|w|w<<w.slice!(-1).chr.upcase}.join' ' For those interested as to what is going on here is an explanation. split will split the sentence up into an array, the default delimiter is a space and with Ruby you don't need to use brackets here. map the array from split is passed to map which opens a block and process each word (w) in the array. the block slice!(s) off the last character of the word and converts it to a chr (a character not ASCII code) and then capitalises upcase it. This character is now appended << to the word which is missing the sliced last letter. Finally the array of words is now join together with a ' ' to reform the sentence. Enjoy

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  • Wasteful Ajax Page Loading

    - by Matt Dawdy
    I've started a new job, and the portion of the project I'm working has a very odd structure. Every pages is a .Net aspx page, and it loads just fine, but nothing is really done at load time. Everything is really loaded from a jquery document.onready handler. What is even more...interesting...is that the onready handler calls some ajax calls that drop entire .aspx pages into divs on the page, but first it strips out several parts of the the returned page. This is the "magic" script the previous programmer ran on all the returned html from his ajax calls: function CleanupResponseText(responseText, uniqueName) { responseText = responseText.replace("theForm.submit();", "SubmitSubForm(theForm, $(theForm).parent());"); responseText = responseText.replace(new RegExp("theForm", "g"), uniqueName); responseText = responseText.replace(new RegExp("doPostBack", "g"), "doPostBack" + uniqueName); return responseText; } He then intercepts any kind of form postback and runs his own form submission function: function SubmitSubForm(form, container) { //ShowLoading(container); $(form).ajaxSubmit( { url: $(form).attr("action"), success: function(responseText) { $(container).html(CleanupResponseText(responseText, form.id)); $("form", container).css("margin-top", "0").css("padding-top", "0"); //HideLoading(container); } } ); } Am I way offbase in thinking that this is less than optimal? I mean, how does a browser take out the html and head and other tags that don't have anything to do with what you are really trying to drop into that div? Also, he's returning things like asp:gridview controls, and the associate viewstate, which can be quite large if his dataset is big. Has anyone seen this before?

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  • How to query the SPView object

    - by Hugo Migneron
    I have a SPView object that contains a lot of SPListItem objects (there are many fields in the view). I am only interested in one of these fields. Let's call it specialField Given that view and specialField, I want to know if a value is contained in specialField. Here is a way of doing what I want to do : String specialField = "Special Field"; String specialValue = "value"; SPList list = SPContext.Current.Site.RootWeb.Lists["My List"]; SPView view = list.Views["My View"]; //This is the view I want to query SPQuery query = new SPQuery(); query.Query = view.Query; SPListItemCollection items = list.GetItems(query); foreach(SPListItem item in items) { var value = item[specialField]; if(value != null) && (value.ToString() == specialValue) { //My value is found. This is what I was looking for. //break out of the loop or return } } //My value is not found. However, iterating through each ListItem hardly seems optimal, especially as there might be hundreds of items. This query will be executed often, so I am looking for an efficient way to do this. EDIT I will not always be working with the same view, so my solution cannot be hardcoded (it has to be generic enough that the list, view and specialField can be changed.

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  • Combining XmlWriter objects?

    - by Kevin
    The way my application is structured, each component generates output as XML and returns an XmlWriter object. Before rendering the final output to the page, I combine all XML and perform an XSL transformation on that object. Below, is a simplified code sample of the application structure. Does it make sense to combine XmlWriter objects like this? Is there a better way to structure my application? The optimal solution would be one where I didn't have to pass a single XmlWriter instance as a parameter to each component. function page1Xml() { $content = new XmlWriter(); $content->openMemory(); $content->startElement('content'); $content->text('Sample content'); $content->endElement(); return $content; } function generateSiteMap() { $sitemap = new XmlWriter(); $sitemap->openMemory(); $sitemap->startElement('sitemap'); $sitemap->startElement('page'); $sitemap->writeAttribute('href', 'page1.php'); $sitemap->text('Page 1'); $sitemap->endElement(); $sitemap->endElement(); return $sitemap; } function output($content) { $doc = new XmlWriter(); $doc->openMemory(); $doc->writePi('xml-stylesheet', 'type="text/xsl" href="template.xsl"'); $doc->startElement('document'); $doc->writeRaw( generateSiteMap()->outputMemory() ); $doc->writeRaw( $content->outputMemory() ); $doc->endElement(); $doc->endDocument(); $output = xslTransform($doc); return $output; } $content = page1Xml(); echo output($content); Update: I may abandon XmlWriter altogether and use DomDocument instead. It is more flexible and it also seemed to perform better (at least on the crude tests I created).

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  • What is this: main:for(...){...} doing?

    - by David Murdoch
    I pulled up the NWmatcher source code for some light morning reading and noticed this odd bit of code I'd never seen in javascript before: main:for(/*irrelevant loop stuff*/){/*...*/} This snippet can be found in the compileGroup method on line 441 (nwmatcher-1.1.1) return new Function('c,s,d,h', 'var k,e,r,n,C,N,T,X=0,x=0;main:for(k=0,r=[];e=N=c[k];k++){' + SKIP_COMMENTS + source + '}return r;' ); Now I figured out what main: is doing on my own. If you have a loop within a loop and want to skip to the next iteration of the outer loop (without completing the inner OR the outer loop) you can execute continue main. Example: // This is obviously not the optimal way to find primes... function getPrimes(max) { var primes = [2], //seed sqrt = Math.sqrt, i = 3, j, s; outer: for (; i <= max; s = sqrt(i += 2)) { j = 3; while (j <= s) { if (i % j === 0) { // if we get here j += 2 and primes.push(i) are // not executed for the current iteration of i continue outer; } j += 2; } primes.push(i); } return primes; } What is this called? Are there any browsers that don't support it? Are there other uses for it other than continue?

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  • In what order should the Python concepts be explained to absolute beginners?

    - by Tomaž Pisanski
    I am teaching Python to undergraduate math majors. I am interested in the optimal order in which students should be introduced to various Python concepts. In my view, at each stage the students should be able to solve a non-trivial programming problem using only the tools available at that time. Each new tool should enable a simpler solution to a familiar problem. A selection of numerous concepts available in Python is essential in order to keep students focused. They should also motivated and should appreciate each newly mastered tool without too much memorization. Here are some specific questions: For instance, my predecessor introduced lists before strings. I think the opposite is a better solution. Should function definitions be introduced at the very beginning or after mastering basic structured programming ideas, such as decisions (if) and loops (while)? Should sets be introduced before dictionaries? Is it better to introduce reading and writing files early in the course or should one use input and print for most of the course? Any suggestions with explanations are most welcome.

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  • Removing dotted border without setting NoFocus in Windows PyQt

    - by Cryptite
    There are a few questions on SO about this, all of which seem to say that the only way to remove the dotted border is to set the focusPolicy on widget/item in question to NoFocus. While this works as a temporary fix, this prevents further interaction with said widget/item in the realm of other necessary focusEvents. Said border in question: Here's an example of why this doesn't work. I have a Non-Modal widget popup, think a lightbox for an image. I want to detect a mousePressEvent outside of the widget and close the widget as a result. To do this, I should catch the focusOutEvent. However, if a vast majority of widgets in my program are set as NoFocus (to remove the border issue), then I cannot catch the focusOutEvent because, you guessed it, they have no focus policy. Here's another example: I have a QTreeWidget that is subclassed so I can catch keyPressEvents for various reasons. The QTreeWidget is also set as NoFocus to prevent the border. Because of this, however, the widget never has focus and therefore no keyPressEvents can be caught. A workaround for this (kludgy, imo) is to use the widget's grabKeyboard class, which is dangerous if I forget to releaseKeyboard later. This is not optimal. So then the question is, is there a way to remove this weird (mostly just ugly) dotted border without turning off focus for everything in my app? Thanks in advance!

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  • Fast (de)serialization on iPhone

    - by Jacob Kuypers
    I'm developing a game/engine for iPhone OS. It's the first time I'm using Objective-C. I made my own binary format for geometry data and for textures I'm focusing on PVRTC. That should be the optimal approach as far as speed and space are concerned. I really want to keep loading time to a minimum and - if possible - be able to save very fast as well. So now I'm trying to make my "Entity" stuff persistent without sacrificing performance. First I wanted to use NSKeyedArchiver. From what I've heard, it's not very fast. Also, what I want to serialize is mostly structs made of floats with some ints and strings, so there isn't really a need for all that "object graph" overhead. NSArchiver would have been more appropriate, but they kicked that off the iphone for some reason. So now I'm thinking about making my own serialization scheme again. Am I wrong in thinking that NSKeyedArchiver is slow (I only read that, haven't tested it myself)? If so, what's the best way to encode/decode structs (with no pointers, mostly floats) without sacrificing speed?

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  • Async task ASP.net HttpContext.Current.Items is empty - How do handle this?

    - by GuruC
    We are running a very large web application in asp.net MVC .NET 4.0. Recently we had an audit done and the performance team says that there were a lot of null reference exceptions. So I started investigating it from the dumps and event viewer. My understanding was as follows: We are using Asyn Tasks in our controllers. We rely on HttpContext.Current.Items hashtable to store a lot of Application level values. Task<Articles>.Factory.StartNew(() => { System.Web.HttpContext.Current = ControllerContext.HttpContext.ApplicationInstance.Context; var service = new ArticlesService(page); return service.GetArticles(); }).ContinueWith(t => SetResult(t, "articles")); So we are copying the context object onto the new thread that is spawned from Task factory. This context.Items is used again in the thread wherever necessary. Say for ex: public class SomeClass { internal static int StreamID { get { if (HttpContext.Current != null) { return (int)HttpContext.Current.Items["StreamID"]; } else { return DEFAULT_STREAM_ID; } } } This runs fine as long as number of parallel requests are optimal. My questions are as follows: 1. When the load is more and there are too many parallel requests, I notice that HttpContext.Current.Items is empty. I am not able to figure out a reason for this and this causes all the null reference exceptions. 2. How do we make sure it is not null ? Any workaround if present ? NOTE: I read through in StackOverflow and people have questions like HttpContext.Current is null - but in my case it is not null and its empty. I was reading one more article where the author says that sometimes request object is terminated and it may cause problems since dispose is already called on objects. I am doing a copy of Context object - its just a shallow copy and not a deep copy.

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  • How to optimize shopping carts for minimal prices?

    - by tangens
    I have a list of items I want to buy. The items are offered by different shops and different prices. The shops have individual delivery costs. I'm looking for an optimal shopping strategy (and a java library supporting it) to purchase all of the items with a minimal total price. Example: Item1 is offered at Shop1 for $100, at Shop2 for $111. Item2 is offered at Shop1 for $90, at Shop2 for $85. Delivery cost of Shop1: $10 if total order < $150; $0 otherwise Delivery cost of Shop2: $5 if total order < $50; $0 otherwise If I buy Item1 and Item2 at Shop1 the total cost is $100 + $90 +$0 = $190. If I buy Item1 and Item2 at Shop2 the total cost is $111 + $85 +$0 = $196. If I buy Item1 at Shop1 and Item2 at Shop2 the total cost is $100 + $10 + $85 + $0 = 195. I get the minimal price if I order Item1 at Shop1 and Item2 at Shop2: $195 Question I need some hints which algorithms may help me to solve optimization problems of this kind for number of items about 100 and number of shops about 20. I already looked at apache-math and its optimization package, but I have no idea what algorithm to look for.

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  • How to generate a monotone MART ROC in R?

    - by user1521587
    I am using R and applying MART (Alg. for multiple additive regression trees) on a training set to build prediction models. When I look at the ROC curve, it is not monotone. I would be grateful if someone can help me with how I should fix this. I am guessing the issue is that initially, MART generates n trees and if these trees are not the same for all the models I am building, the results will not be comparable. Here are the steps I take: 1) Fix the false-negative cost, c_fn. Let cost = c(0, 1, c_fn, 0). 2) use the following line to build the mart model: mart(x, y, lx, martmode='class', niter=2000, cost.mtx=cost) where x is the matrix of training set variables, y is the observation matrix, lx is the matrix which specifies which of the variables in x is numerical, which one categorical. 3) I predict the test set observations using the mart model found in step 2 using this line: y_pred = martpred(x_test, probs=T) 4) I compute the false-positive and false-negative errors as follows: t = 1/(1+c_fn) %threshold based on Bayes optimal rule where c_fp=1 and c_fn. p_0 = length(which(y_test==1))/dim(y_test)[1] p_01 = sum(1*(y_pred[,2]t & y_test==0))/dim(y_test)[1] p_11 = sum(1*(y_pred[,2]t & y_test==1))/dim(y_test)[1] p_fp = p_01/(1-p_0) p_tp = p_11/p_0 5) repeat step 1-4 for a new false-negative cost.

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  • finding N contiguous zero bits in an integer to the left of the MSB from another

    - by James Morris
    First we find the MSB of the first integer, and then try to find a region of N contiguous zero bits within the second number which is to the left of the MSB from the first integer. Here is the C code for my solution: typedef unsigned int t; unsigned const t_bits = sizeof(t) * CHAR_BIT; _Bool test_fit_within_left_of_msb( unsigned width, t val1, t val2, unsigned* offset_result) { unsigned offbit = 0; unsigned msb = 0; t mask; t b; while(val1 >>= 1) ++msb; while(offbit + width < t_bits - msb) { mask = (((t)1 << width) - 1) << (t_bits - width - offbit); b = val2 & mask; if (!b) { *offset_result = offbit; return true; } if (offbit++) /* this conditional bothers me! */ b <<= offbit - 1; while(b <<= 1) offbit++; } return false; } Aside from faster ways of finding the MSB of the first integer, the commented test for a zero offbit seems a bit extraneous, but necessary to skip the highest bit of type t if it is set. I have also implemented similar algorithms but working to the right of the MSB of the first number, so they don't require this seemingly extra condition. How can I get rid of this extra condition, or even, are there far more optimal solutions?

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  • Need help extrapolating Java code

    - by Berlioz
    If anyone familiar with Rebecca Wirfs-Brock, she has a piece of Java code found in her book titled, Object Design: Roles, Responsibilities, and Collaborations. Here is the quote Applying Double Dispatch to a Specific Problem To implement the game Rock, Paper, Scissors we need to write code that determines whether one object “beats” another. The game has nine possible outcomes based on the three kinds of objects. The number of interactions is the cross product of the kinds of objects. Case or switch statements are often governed by the type of data that is being operated on. The object-oriented language equivalent is to base its actions on the class of some other object. In Java, it looks like this Here is the piece of Java code on page 16 ' import java.util.*; import java.lang.*; public class Rock { public static void main(String args[]) { } public static boolean beats(GameObject object) { if (object.getClass.getName().equals("Rock")) { result = false; } else if (object.getClass.getName().equals("Paper")) { result = false; } else if(object.getClass.getName().equals("Scissors")) { result = true; } return result; } }' ===This is not a very good solution. First, the receiver needs to know too much about the argument. Second, there is one of these nested conditional statements in each of the three classes. If new kinds of objects could be added to the game, each of the three classes would have to be modified. Can anyone share with me how to get this "less than optimal" piece of code to work in order to see it 'working'. She proceeds to demonstrate a better way, but I will spare you. Thanks

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  • Fast find object by string property

    - by Andrew Kalashnikov
    Hello, colleagues. I've got task to fast find object by its string property. Object: class DicDomain { public virtual string Id{ get; set; } public virtual string Name { get; set; } } For storing my object I use List[T] dictionary where T is DicDomain for now . I've got 5-10 such lists, which contain about 500-20000 at each one. Task is find objects by its Name. I use next code now: List<T> entities = dictionary.FindAll(s => s.Name.Equals(word, StringComparison.OrdinalIgnoreCase)); I've got some questions: Is my search speed optimal. I think now. Data structure. It List good for this task. What about hashtable,sorted... Method Find. May be i should use string intern?? I haven't much exp at these tasks. Can u give me good advice for increase perfomance. Thanks

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  • Terminate function on System.in .. possible?

    - by Ronald
    I am currently working on a project where I have to make an agent to interact with a server. Each 50ms, the server will receive the last thing I outputted to System.out and send me a new set of lines as a 'state' through the System.in printstream to analyze and send my next message to System.out. Also, if the server receives multiple outputs from me, it only regards the most recent one. .. As for my question: My program originally constructed a tree and then analyzed each leaf node to see which would be optimal, and then waited around for the next input, but I can recursively do a deeper tree search that would make my output 'better' (and again and again to keep returning a better result). Using this and the fact that if the server receives multiple outputs, it only takes the most recent one, I could do each level, print my result and start the next level. But here comes my problem... I can't be stuck in some complex algorithm while I am supposed to receiving the next input as I will then miss it. So I was wondering if there is a way to cancel anything else I am doing when I receive something via System.in and then go back to the beginning of the function and start the search again with the new set of input (and rinse and repeat..) I hope this all makes sense, Thank ye all

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  • NHibernate / multiple sessions and nested objects

    - by bernhardrusch
    We are using NHibernate in a rich client application. It is a pretty open application (the user searches for a dataset or creates a new one, changes the data and saves the data set. We leave the session open, because sometimes we have to lazy load some properties of the object (nested object structure). This means one big problem if we leave the session open, the db (MySQL) closes the connection and we are not able to find this out and it throws an exception (socket communication error) when accessing the database (we are thinking about testing the db connection before accessing the object - but this is not really optimal neither, the other option would be to set back the timeout of the db connection , but this just doesn't seem to well). So - is it possible to reconnect the session to a new database connection ? Another problem is it possible to get an object from one session and then re-attach it to another session ? (I often hear that session.lock should work for this - but this doesn't work so well in our application - so I ended up getting a "fresh" object from the session and copy the data over manually - which is a little bit cumbersome) Any ideas for this ?

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  • Scala always returning true....WHY?

    - by jhamm
    I am trying to learn Scala and am a newbie. I know that this is not optimal functional code and welcome any advice that anyone can give me, but I want to understand why I keep getting true for this function. def balance(chars: List[Char]): Boolean = { val newList = chars.filter(x => x.equals('(') || x.equals(')')); return countParams(newList, 0) } def countParams(xs: List[Char], y: Int): Boolean = { println(y + " right Here") if (y < 0) { println(y + " Here") return false } else { println(y + " Greater than 0") if (xs.size > 0) { println(xs.size + " this is the size") xs match { case xs if (xs.head.equals('(')) => countParams(xs.tail, y + 1) case xs if (xs.head.equals(')')) => countParams(xs.tail, y - 1) case xs => 0 } } } return true; } balance("()())))".toList) I know that I am hitting the false branch of my if statement, but it still returns true at the end of my function. Please help me understand. Thanks.

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  • How can I find the common ancestor of two nodes in a binary tree?

    - by Siddhant
    The Binary Tree here is not a Binary Search Tree. Its just a Binary Tree. The structure could be taken as - struct node { int data; struct node *left; struct node *right; }; The maximum solution I could work out with a friend was something of this sort - Consider this binary tree (from http://lcm.csa.iisc.ernet.in/dsa/node87.html) : The inorder traversal yields - 8, 4, 9, 2, 5, 1, 6, 3, 7 And the postorder traversal yields - 8, 9, 4, 5, 2, 6, 7, 3, 1 So for instance, if we want to find the common ancestor of nodes 8 and 5, then we make a list of all the nodes which are between 8 and 5 in the inorder tree traversal, which in this case happens to be [4, 9, 2]. Then we check which node in this list appears last in the postorder traversal, which is 2. Hence the common ancestor for 8 and 5 is 2. The complexity for this algorithm, I believe is O(n) (O(n) for inorder/postorder traversals, the rest of the steps again being O(n) since they are nothing more than simple iterations in arrays). But there is a strong chance that this is wrong. :-) But this is a very crude approach, and I'm not sure if it breaks down for some case. Is there any other (possibly more optimal) solution to this problem?

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  • Time taken for memcpy decreases after certain point

    - by tss
    I ve a code which increases the size of the memory(identified by a pointer) exponentially. Instead of realloc, I use malloc followed by memcpy.. Something like this.. int size=5,newsize; int *c = malloc(size*sizeof(int)); int *temp; while(1) { newsize=2*size; //begin time temp=malloc(newsize*sizeof(int)); memcpy(temp,c,size*sizeof(int)); //end time //print time in mili seconds c=temp; size=newsize; } Thus the number of bytes getting copied is increasing exponentially. The time required for this task also increases almost linearly with the increase in size. However after certain point, the time taken abruptly reduces to a very small value and then remains constant. I recorded time for similar code, copyin data(Of my own type) 5 -> 10 - 2 ms 10 -> 20 - 2 ms . . 2560 -> 5120 - 5 ms . . 20480 -> 40960 - 30 ms 40960 -> 91920 - 58 ms 367680 -> 735360 - 2 ms 735360 -> 1470720 - 2 ms 1470720 -> 2941440 - 2 ms What is the reason for this drop in time ? Does a more optimal memcpy method get called when the size is large ?

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  • Triangulation & Direct linear transform

    - by srand
    Following Hartley/Zisserman's Multiview Geometery, Algorithm 12: The optimal triangulation method (p318), I got the corresponding image points xhat1 and xhat2 (step 10). In step 11, one needs to compute the 3D point Xhat. One such method is Direct Linear Transform (DLT), mentioned in 12.2 (p312) and 4.1 (p88). The homogenous method (DLT), p312-313, states that it finds a solution as the unit singular vector corresponding to the smallest singular value of A, thus, A = [xhat1(1) * P1(3,:)' - P1(1,:)' ; xhat1(2) * P1(3,:)' - P1(2,:)' ; xhat2(1) * P2(3,:)' - P2(1,:)' ; xhat2(2) * P2(3,:)' - P2(2,:)' ]; [Ua Ea Va] = svd(A); Xhat = Va(:,end); plot3(Xhat(1),Xhat(2),Xhat(3), 'r.'); However, A is a 16x1 matrix, resulting in a Va that is 1x1. What am I doing wrong (and a fix) in getting the 3D point? For what its worth sample data: xhat1 = 1.0e+009 * 4.9973 -0.2024 0.0027 xhat2 = 1.0e+011 * 2.0729 2.6624 0.0098 P1 = 699.6674 0 392.1170 0 0 701.6136 304.0275 0 0 0 1.0000 0 P2 = 1.0e+003 * -0.7845 0.0508 -0.1592 1.8619 -0.1379 0.7338 0.1649 0.6825 -0.0006 0.0001 0.0008 0.0010 A = <- my computation 1.0e+011 * -0.0000 0 0.0500 0 0 -0.0000 -0.0020 0 -1.3369 0.2563 1.5634 2.0729 -1.7170 0.3292 2.0079 2.6624

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  • Time complexity of a powerset generating function

    - by Lirik
    I'm trying to figure out the time complexity of a function that I wrote (it generates a power set for a given string): public static HashSet<string> GeneratePowerSet(string input) { HashSet<string> powerSet = new HashSet<string>(); if (string.IsNullOrEmpty(input)) return powerSet; int powSetSize = (int)Math.Pow(2.0, (double)input.Length); // Start at 1 to skip the empty string case for (int i = 1; i < powSetSize; i++) { string str = Convert.ToString(i, 2); string pset = str; for (int k = str.Length; k < input.Length; k++) { pset = "0" + pset; } string set = string.Empty; for (int j = 0; j < pset.Length; j++) { if (pset[j] == '1') { set = string.Concat(set, input[j].ToString()); } } powerSet.Add(set); } return powerSet; } So my attempt is this: let the size of the input string be n in the outer for loop, must iterate 2^n times (because the set size is 2^n). in the inner for loop, we must iterate 2*n times (at worst). 1. So Big-O would be O((2^n)*n) (since we drop the constant 2)... is that correct? And n*(2^n) is worse than n^2. if n = 4 then (4*(2^4)) = 64 (4^2) = 16 if n = 100 then (10*(2^10)) = 10240 (10^2) = 100 2. Is there a faster way to generate a power set, or is this about optimal?

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  • [iPhone] Play video not in full screen mode

    - by Kyo
    Hello, First, excuse my english :) I've read on apple developer website that video playback provides by the framework supports only full screen mode. I will need to develop an application where video can be played in reduce screen mode. I've see that Orange TV make something which looks like what i need to do. http://img218.imageshack.us/img218/1228/tvplayerorange.jpg The application is available on app store but you need to have a subscription to test this application. Whatever, to resume it, we can see video (tv stream video) in a reduce mode and if we click on the screen it switch to a full screen mode. So my question, what i want to do is possible (Orange TV made it) but i wonder the difficulty to make it. It seems that I have to make a video player. If it take a bunch of time, I tkink I will use Media Player Framework of iPhone even isn't the optimal solution for me. Feel free to ask me more details ;) Thank you for your answers.

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  • How to get timestamp of tick precision in .NET / C#?

    - by Hermann
    Up until now I used DateTime.Now for getting timestamps, but I noticed that if you print DateTime.Now in a loop you will see that it increments in descrete jumps of approx. 15 ms. But for certain scenarios in my application I need to get the most accurate timestamp possible, preferably with tick (=100 ns) precision. Any ideas? Update: Apparently, StopWatch / QueryPerformanceCounter is the way to go, but it can only be used to measure time, so I was thinking about calling DateTime.Now when the application starts up and then just have StopWatch run and then just add the elapsed time from StopWatch to the initial value returned from DateTime.Now. At least that should give me accurate relative timestamps, right? What do you think about that (hack)? NOTE: StopWatch.ElapsedTicks is different from StopWatch.Elapsed.Ticks! I used the former assuming 1 tick = 100 ns, but in this case 1 tick = 1 / StopWatch.Frequency. So to get ticks equivalent to DateTime use StopWatch.Elapsed.Ticks. I just learned this the hard way. NOTE 2: Using the StopWatch approach, I noticed it gets out of sync with the real time. After about 10 hours, it was ahead by 5 seconds. So I guess one would have to resync it every X or so where X could be 1 hour, 30 min, 15 min, etc. I am not sure what the optimal timespan for resyncing would be since every resync will change the offset which can be up to 20 ms.

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  • Interview Q: sorting an almost sorted array (elements misplaced by no more than k)

    - by polygenelubricants
    I was asked this interview question recently: You're given an array that is almost sorted, in that each of the N elements may be misplaced by no more than k positions from the correct sorted order. Find a space-and-time efficient algorithm to sort the array. I have an O(N log k) solution as follows. Let's denote arr[0..n) to mean the elements of the array from index 0 (inclusive) to N (exclusive). Sort arr[0..2k) Now we know that arr[0..k) are in their final sorted positions... ...but arr[k..2k) may still be misplaced by k! Sort arr[k..3k) Now we know that arr[k..2k) are in their final sorted positions... ...but arr[2k..3k) may still be misplaced by k Sort arr[2k..4k) .... Until you sort arr[ik..N), then you're done! This final step may be cheaper than the other steps when you have less than 2k elements left In each step, you sort at most 2k elements in O(k log k), putting at least k elements in their final sorted positions at the end of each step. There are O(N/k) steps, so the overall complexity is O(N log k). My questions are: Is O(N log k) optimal? Can this be improved upon? Can you do this without (partially) re-sorting the same elements?

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