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• Problem with for-loop in python

  - by Protean

  This code is supposed to be able to sort the items in self.array based upon the order of the characters in self.order. The method sort runs properly until the third iteration, unil for some reason the for loop seems to repeat indefinitely. What is going on here? class sorting_class: def __init__(self): self.array = ['ca', 'bd', 'ac', 'ab'] #An array of strings self.arrayt = [] self.globali = 0 self.globalii = 0 self.order = ['a', 'b', 'c', 'd'] #Order of characters self.orderi = 0 self.carry = [] self.leave = [] self.sortedlist = [] def sort(self): for arrayi in self.arrayt: #This should only loop for the number items in self.arrayt. However, the third time this is run it seems to loop indefinitely. print ('run', arrayi) #Shows the problem if self.order[self.orderi] == arrayi[self.globali]: self.carry.append(arrayi) else: if self.globali != 0: self.leave.append(arrayi) def srt(self): self.arrayt = self.array my.sort() #First this runs the first time. while len(self.sortedlist) != len(self.array): if len(self.carry) == 1: self.sortedlist.append(self.carry) self.arrayt = self.leave self.leave = [] self.carry = [] self.globali = 1 self.orderi = 0 my.sort() elif len(self.carry) == 0: if len(self.leave) != 0: #Because nothing matches 'aa' during the second iteration, this code runs the third time" self.arrayt = self.leave self.globali = 1 self.orderi += 1 my.sort() else: self.arrayt = self.array self.globalii += 1 self.orderi = self.globalii self.globali = 0 my.sort() self.orderi = 0 else: #This is what runs the second time. self.arrayt = self.carry self.carry = [] self.globali += 1 my.sort() my = sorting_class() my.srt()

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• Can't write to dynamic iframe using jQuery

  - by Fremont Troll

  My goal is to dynamically create an iframe and write ad JavaScript into it using jQuery (e.g. Google AdSense script). My code works on Chrome, but fails intermittently in Firefox i.e. sometimes the ad script runs and renders the ad, and other times it doesn't. When it doesn't work, the script code itself shows up in the iframe. My guess is these intermittent failures occur because the iframe is not ready by the time I write to it. I have tried various iterations of *iframe_html* (my name for the function which is supposed to wait for the iframe to be ready), but no luck. Any help appreciated! PS: I have read various threads (e.g. http://stackoverflow.com/questions/205087/jquery-ready-in-a-dynamically-inserted-iframe). Just letting everyone know that I've done my research on this, but I'm stuck :) Iteration 1: function iframe_html(html){ $('<iframe name ="myiframe" id="myiframe"/>').appendTo('#maindiv'); $('#myiframe').load( function(){ $('#myiframe').ready( function(){ var d = $("#myiframe")[0].contentWindow.document; d.open(); d.close(); d.write(html); }); } ); }; Iteration 2: function iframe_html(html){ $('<iframe id="myiframe"/>').appendTo('#maindiv').ready( function(){ $("#myiframe").contents().get(0).write(html); } ); };

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• strange memory error when deleting object from Core Data

  - by llloydxmas

  I have an application that downloads an xml file, parses the file, and creates core data objects while doing so. In the parse code I have a function called 'emptydatacontext' that removes all items from Core Data before creating replacements from the xml file. This method looks like this: -(void) emptyDataContext { NSMutableArray* mutableFetchResults = [CoreDataHelper getObjectsFromContext:@"Condition" :@"road" :NO :managedObjectContext]; NSFetchRequest * allCon = [[NSFetchRequest alloc] init]; [allCon setEntity:[NSEntityDescription entityForName:@"Condition" inManagedObjectContext:managedObjectContext]]; NSError * error = nil; NSArray * conditions = [managedObjectContext executeFetchRequest:allCon error:&error]; [allCon release]; for (NSManagedObject * condition in conditions) { [managedObjectContext deleteObject:condition]; } } The first time this runs it deletes all objects and functions as it should - creating new objects from the xml file. I created a 'update' button that starts the exact same process of retrieving the file the preceeding as it did the first time. All is well until its time to delete the core data objects again. This 'deleteObject' call creates a "EXC_BAD_ACCESS" error each time. This only happens on the second time through. See this image for the debugger window as it appears when walking through the deletion FOR loop on the second iteration. Conditions is the fetched array of 7 objects with the objects below. Condition should be an individual condition. link text As you can see 'condition' does not match any of the objects in the 'conditions' array. I'm sure this is why I'm getting the memory access errors. Just not sure why this fetch (or the FOR) is returning a wrong reference. All the code that successfully performes this function on the first iteration is used in the second but with very different results. Thanks in advance for the help!

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• How to prevent ADO.NET from altering double values when it reads from Excel files

  - by Khnle

  I have the following rows in my Excel input file: Column1 Column2 0-5 3.040 6 2.957 7 2.876 and the following code which uses ADO.NET to read it: string fileName = "input.xls"; var connectionString = string.Format("Provider=Microsoft.Jet.OLEDB.4.0; data source={0}; Extended Properties=Excel 8.0;", fileName); var dbConnection = new OleDbConnection(connectionString); dbConnection.Open(); try { var dbCommand = new OleDbCommand("SELECT * FROM [Sheet1$]", dbConnection); var dbReader = dbCommand.ExecuteReader (); while (dbReader.Read()) { string col1 = dbReader.GetValue(0).ToString(); string col2 = dbReader.GetValue(1).ToString(); } } finally { dbConnection.Close(); } The results are very disturbing. Here's why: The values of each column in the first time through the loop: col1 is empty (blank) col2 is 3.04016411633586 Second time: col1 is 6 col2 is 2.95722928448829 Third time: col1 is 7 col2 is 2.8763272933077 The first problem happens with col1 in the first iteration. I expect 0-5. The second problem happens at every iteration with col2 where ADO.NET obviously alters the values as it reads them. How to stop this mal-behavior?

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• Uniquing with Existing Core Data Entities

  - by warrenm

  I'm using Core Data to store a lot (1000s) of items. A pair of properties on each item are used to determine uniqueness, so when a new item comes in, I compare it against the existing items before inserting it. Since the incoming data is in the form of an RSS feed, there are often many duplicates, and the cost of the uniquing step is O(N^2), which has become significant. Right now, I create a set of existing items before iterating over the list of (possible) new items. My theory is that on the first iteration, all the items will be faulted in, and assuming we aren't pressed for memory, most of those items will remain resident over the course of the iteration. I see my options thusly: Use string comparison for uniquing, iterating over all "new" items and comparing to all existing items (Current approach) Use a predicate to filter the set of existing items against the properties of the "new" items. Use a predicate with Core Data to determine uniqueness of each "new" item (without retrieving the set of existing items). Is option 3 likely to be faster than my current approach? Do you know of a better way?

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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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• "java.lang.OutOfMemoryError: Java heap space" in image and array storage

  - by totalconscience

  I am currently working on an image processing demonstration in java (Applet). I am running into the problem where my arrays are too large and I am getting the "java.lang.OutOfMemoryError: Java heap space" error. The algorithm I run creates an NxD float array where: N is the number of pixel in the image and D is the coordinates of each pixel plus the colorspace components of each pixel (usually 1 for grayscale or 3 for RGB). For each iteration of the algorithm it creates one of these NxD float arrays and stores it for later use in a vector, so that the user of the applet may look at the individual steps. My client wants the program to be able to load a 500x500 RGB image and run as the upper bound. There are about 12 to 20 iterations per run so that means I need to be able to store a 12x500x500x5 float in some fashion. Is there a way to process all of this data and, if possible, how? Example of the issue: I am loading a 512 by 512 Grayscale image and even before the first iteration completes I run out of heap space. The line it points me to is: Y.add(new float[N][D]) where Y is a Vector and N and D are described as above. This is the second instance of the code using that line.

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• Creating new image in a loop using OpenCV

  - by user565415

  I am programing some image conversion code with OpenCV and I don't know how can I create image memory buffer to load image on every iteration. I have number of iteration (maxImNumber) and I have an input image. In every loop program must create image that is resized and modified input image. Here is some basic code (concept). for (int imageIndex = 0; imageIndex < maxImNumber; imageIndex++){ cvCopy(inputImage, images[imageIndex], 0); cvReleaseImage(&inputImage); images[imageIndex+1] = cvCreateImage(cvSize((image[imageIndex]->width)/2, image[imageIndex]->height), IPL_DEPTH_8U, 1); for (i=1; i < image[imageIndex]->height; i++) { index = 0; // for(j=0; j < image[imageIndex]->width ; j=j+2){ // doing some basic matematical operation on image content and store it to new image images[imageIndex+1][i][index] = (image[imageIndex][i][j] + image[imageIndex][i][j+2])/2; index++ } } inputImage = cvCreateImage(cvSize((image[imageIndex+1]->width), image[imageIndex]->height), IPL_DEPTH_8U, 1); cvCopy(images[imageIndex+1], inputImage, 0); } Can somebody, please, explain how can I create this image buffer (images[]) and allocate memory for it. Also how can I access any image in this buffer? Thank you very much in advance!

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• How to "pin" C++/CLI pointers

  - by Kumar

  I am wrapping up a class which reading a custom binary data file and makes the data available to a .net/c# class However a couple of lines down the code, i start getting the memory access violation error which i believe is due to the GC moving memory around, the class is managed Here's the code if ( ! reader.OpenFile(...) ) return ; foreach(string fieldName in fields) { int colIndex = reader.GetColIndex( fieldName ); int colType = reader.GetColType( colIndex ); // error is raised here on 2nd iteration } for ( int r = 0 ; r < reader.NumFields(); r++ ) { foreach(string fieldName in fields) { int colIndex = reader.GetColIndex( fieldName ); int colType = reader.GetColType( colIndex ); // error is raised here on 2nd iteration switch ( colType ) { case 0 : // INT processField( r, fieldName, reader.GetInt(r,colIndex) ); break ; .... } } } .... i've looked at interior_ptr, pin_ptr but they give an error c3160 cannot be in a managed class Any workaround ? BTW, this is my 1st C++ program in a very long time !

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• How can I write simulations in Erlang?

  - by rick

  Hi guys, I want to do some numerical stuff in Erlang like this: You've got an array with the following values: [2,3,4] In each iteration, you calculate 0.1 * [n-1] + 0.7 *[n] + 0.2 * [n+1] This becomes the new [n]. If n == 0 then [n-1] = 0. If [n] == length of array then [n] = 0. So I try an example: [2,3,4] calculations: 0.1 * 0 + 0.7 * 2 + 0.2 * 3 = 2 0.1 * 2 + 0.7 * 3 + 0.2 * 4 = 3.1 0.1 * 3 + 0.7 * 4 + 0.2 * 0 = 3.1 So [2,3,4] becomes to [2, 3.1, 3.1] after one iteration. I know how to write this in a non-functional language like C. But I have difficulties to imagine, how this could be done in Erlang. I found some tutorials on how you read a file to a list. So this is not the problem. How can I spawn different Erlang processes that each process has one element of the list? How can I do calculations by communicating with 'the neighbors', so that the neighbors know where their neigbors are generically, without specifying each? How can I collect the data into a list? Eventually, is it possible to solve that problem in Erlang at all? Thanks for your help.

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• OpenCV compare two images and get different pixels

  - by Richard Knop

  For some reason the code bellow is not working. I have two 640*480 images which are very similar but not the same (at least few hundred/thousand pixels should be different). This is how I am comparing them and counting different pixels: unsigned char* row; unsigned char* row2; int count = 0; // this happens in a loop // fIplImageHeader is current image // lastFIplImageHeader is image from previous iteration if ( NULL != lastFIplImageHeader->imageData ) { for( int y = 0; y < fIplImageHeader->height; y++ ) { row = &CV_IMAGE_ELEM( fIplImageHeader, unsigned char, y, 0 ); row2 = &CV_IMAGE_ELEM( lastFIplImageHeader, unsigned char, y, 0 ); for( int x = 0; x < fIplImageHeader->width*fIplImageHeader->nChannels; x += fIplImageHeader->nChannels ) { if (row[x] == row2[x]) // the pixel in the first channel (usually G) { count++; } if (row[x+1] == row2[x+1]) // ... second channel (usually B) { count++; } if (row[x+2] == row2[x+2]) // ... third channel (usually R) { count++; } } } } Now at the end I get number 3626 which would seem alright. But, I tried opening one of the images in MS Paint and drawing thick red lines all over it which should increase the number of different pixels substantially. I got the same number again: 3626. Obviously I am doing something wrong here. I am comparing these images in a loop. This line is before the loop: IplImage* lastFIplImageHeader = cvCreateImageHeader(cvSize(640, 480), 8, 3); Then inside the loop I load images like this: IplImage* fIplImageHeader = cvLoadImage( filePath.c_str() ); // here I compare the pixels (the first code snippet) lastFIplImageHeader->imageData = fIplImageHeader->imageData; So lastFIplImageHeader is storing the image from the previous iteration and fIplImageHeader is storing the current image.

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• ServiceLoader double iterator issues

  - by buge

  Is this a known issue? I had trouble finding any search results. When iterating over a ServiceLoader while an iteration already is in progress, the first iteration will be aborted. For example, assuming there are at least two implementations of Foo, the following code will fail with an AssertionError: ServiceLoader<Foo> loader = ServiceLoader.load(Foo.class); Iterator<Foo> iter1 = loader.iterator(); iter1.next(); Iterator<Foo> iter2 = loader.iterator(); while (iter2.hasNext()) { iter2.next(); } assert iter1.hasNext(); This only seems to occur, if the second iterator really terminates. The code will succeed in this variation for example: ServiceLoader<Foo> loader = ServiceLoader.load(Foo.class); Iterator<Foo> iter1 = loader.iterator(); iter1.next(); Iterator<Foo> iter2 = loader.iterator(); iter2.next(); assert iter1.hasNext(); Is this a bug or a feature? :p Is there a ticket for this already anywhere?

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• CSV Parser works in windows, not linux.

  - by ladookie

  I'm parsing a CSV file that looks like this: E1,E2,E7,E8,,, E2,E1,E3,,,, E3,E2,E8,,, E4,E5,E8,E11,,, I store the first entry in each line in a string, and the rest go in a vector of strings: while (getline(file_input, line)) { stringstream tokenizer; tokenizer << line; getline(tokenizer, roomID, ','); vector<string> aVector; while (getline(tokenizer, adjRoomID, ',')) { if (!adjRoomID.empty()) { aVector.push_back(adjRoomID); } } Room aRoom(roomID, aVector); rooms.addToTail(aRoom); } In windows this works fine, however in Linux the first entry of each vector mysteriously loses the first character. For Example in the first iteration through the while loop: roomID would be E1 and aVector would be 2 E7 E8 then the second iteration: roomID would be E2 and aVector would be 1 E3 Notice the missing E's in the first entry of aVector. when I put in some debugging code it appears that it is initially being stored correctly in the vector, but then something overwrites it. Kudos to whoever figures this one out. Seems bizarre to me. rooms is declared as such: DLList<Room> rooms where DLList stands for Doubly-Linked list.

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• dotNet Templated, Repeating, Databound ServerControl: Counting the templates OnDataBind?

  - by Campbeln

  I have a server control that wraps an underlying class which manages a number of indexes to track where it is in a dataset (ie: RenderedRecordCount, ErroredRecordCount, NewRecordCount, etc.). I've got the server control rendering great, but OnDataBinding I'm having an issue as to seems to happen after CreateChildControls and before Render (both of which properly manage the iteration of the underlying indexes). While I'm somewhat familiar with the ASP.NET page lifecycle, this one seems to be beyond me at the moment. So... how do I hook into the iterative process OnDataBinding uses so I can manage the underlying indexes? Will I have to iterate over the ITemplates myself, managing the indexes as I go or is there an easier solution? Also... I implemented the iteration of the underlying indexes during CreateChildControls originally in the belief that was the proper place to hook in for events like OnDataBinding (thining it was done as the controls were being .Add'd). Now it seems that this may actually be unnecessary. So I guess the secondary question is: What happens during CreateChildControls? Are the unadulterated (read: with <%-tags in place) controls added to the .Controls collection without any other processing?

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• Applying iterative algorithm to a set of rows from database

  - by Corvin

  Hello, this question may seem too basic to some, but please bear with be, it's been a while since I dealt with decent database programming. I have an algorithm that I need to program in PHP/MySQL to work on a website. It performs some computations iteratively on an array of objects (it ranks the objects based on their properties). In each iteration the algorithm runs through all collection a couple of times, accessing various data from different places of the whole collection. The algorithm needs several hundred iterations to complete. The array comes from a database. The straightforward solution that I see is to take the results of a database query and create an object for each row of the query, put the objects to an array and pass the array to my algorithm. However, I'm concerned with efficacy of such solution when I have to work with an array of several thousand of items because what I do is essentially mirror the results of a query to memory. On the other hand, making database query a couple of times on each iteration of the algorithm also seems wrong. So, my question is - what is the correct architectural solution for a problem like this? Is it OK to mirror the query results to memory? If not, which is the best way to work with query results in such an algorithm? Thanks!

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• Mysterious combination

  - by pstone

  I decided to learn concurrency and wanted to find out in how many ways instructions from two different processes could overlap. The code for both processes is just a 10 iteration loop with 3 instructions performed in each iteration. I figured out the problem consisted of leaving X instructions fixed at a point and then fit the other X instructions from the other process between the spaces taking into account that they must be ordered (instruction 4 of process B must always come before instruction 20). I wrote a program to count this number, looking at the results I found out that the solution is n Combination k, where k is the number of instructions executed throughout the whole loop of one process, so for 10 iterations it would be 30, and n is k*2 (2 processes). In other words, n number of objects with n/2 fixed and having to fit n/2 among the spaces without the latter n/2 losing their order. Ok problem solved. No, not really. I have no idea why this is, I understand that the definition of a combination is, in how many ways can you take k elements from a group of n such that all the groups are different but the order in which you take the elements doesn't matter. In this case we have n elements and we are actually taking them all, because all the instructions are executed ( n C n). If one explains it by saying that there are 2k blue (A) and red (B) objects in a bag and you take k objects from the bag, you are still only taking k instructions when 2k instructions are actually executed. Can you please shed some light into this? Thanks in advance.

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• Why are my thread being terminated ?

  - by Sephy

  Hi, I'm trying to repeat calls to methods through 3 differents threads. But after I start my threads, during the next iteration of my loop, they are all terminated so nothing is executed... The code is as follows : public static void main(String[] args) { main = new Main(); pollingThread.start(); } static Thread pollingThread = new Thread() { @Override public void run() { while (isRunning) { main.poll(); // test the state of the threads try { Thread.sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); } } }; }; public void poll() { if (clientThread == null) { clientThread = new Thread(new Runnable() { @Override public void run() { //create some objects } }); clientThread.start(); } else if (clientThread.isAlive()) { // do some treatment } if (gestionnaireThread == null) { gestionnaireThread = new Thread(new Runnable() { @Override public void run() { //create some objects }; }); gestionnaireThread.start(); } else if (gestionnaireThread.isAlive()) { // do some treatment } if (marchandThread == null) { marchandThread = new Thread(new Runnable() { @Override public void run() { // create some objects }; }); marchandThread.start(); } else if (marchandThread.isAlive()) { // do some treatment } } And for some reason, when I test the state of my different threads, they appear as runnable and then a the 2nd iteration, they are all terminated... What am I doing wrong? I actually have no error, but the threads are terminated and so my loop keeps looping and telling me the threads are terminated.... Thanks for any help.

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• yet another logic.

  - by Sunil

  I'm working on a research problem out of curiosity and I don't know how to program the logic that I've in mind. Let me explain it to you : I've 4 vectors say for example, v1 = 1 1 1 1 v2 = 2 2 2 2 v3 = 3 3 3 3 v4 = 4 4 4 4 Now what I want to do is to add them combination-wise. i.e v12 = v1+v2 v13 = v1+v3 v14 = v1+v4 v23 = v2+v3 v24 = v2+v4 v34 = v3+v4 Till this step it is just fine. The problem/trick is now, at the end of each iteration I give the obtained vectors into a black box function and it returns only few of the vectors say v12, v13 and v34. Now, I want to add each of these vectors one vector from v1,v2,v3,v4 which it hasn't added before. For example v3 and v4 hasn't been added to v12 so I want to create v123 and v124. similarly for all the vectors like, v12 should become : v123 = v12+v3 v124 = v12+v4 v13 should become : v132 // this should not occur because I already have v123 v134 = v13+v4; v14,v23 and v24 cannot be considered because it was deleted in the black box function so all we have in our hands to work with is v12,v13 and v34. v34 should become : v341 // cannot occur because we have 134 v342 = v34+v2 It is important that I do not do all at one step at the start like for example I can do (4 choose 3) 4C3 and finish it off but I want to do it step by step at each iteration. I've asked a modified version of this question before (without including the black box function) and got answers here. Can anybody tell me how to do it when the black box function is included ? A modification of the previous answer would also be great. Thanks in advance.

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• Sorting Algorithms

  - by MarkPearl

  General Every time I go back to university I find myself wading through sorting algorithms and their implementation in C++. Up to now I haven’t really appreciated their true value. However as I discovered this last week with Dictionaries in C# – having a knowledge of some basic programming principles can greatly improve the performance of a system and make one think twice about how to tackle a problem. I’m going to cover briefly in this post the following: Selection Sort Insertion Sort Shellsort Quicksort Mergesort Heapsort (not complete) Selection Sort Array based selection sort is a simple approach to sorting an unsorted array. Simply put, it repeats two basic steps to achieve a sorted collection. It starts with a collection of data and repeatedly parses it, each time sorting out one element and reducing the size of the next iteration of parsed data by one. So the first iteration would go something like this… Go through the entire array of data and find the lowest value Place the value at the front of the array The second iteration would go something like this… Go through the array from position two (position one has already been sorted with the smallest value) and find the next lowest value in the array. Place the value at the second position in the array This process would be completed until the entire array had been sorted. A positive about selection sort is that it does not make many item movements. In fact, in a worst case scenario every items is only moved once. Selection sort is however a comparison intensive sort. If you had 10 items in a collection, just to parse the collection you would have 10+9+8+7+6+5+4+3+2=54 comparisons to sort regardless of how sorted the collection was to start with. If you think about it, if you applied selection sort to a collection already sorted, you would still perform relatively the same number of iterations as if it was not sorted at all. Many of the following algorithms try and reduce the number of comparisons if the list is already sorted – leaving one with a best case and worst case scenario for comparisons. Likewise different approaches have different levels of item movement. Depending on what is more expensive, one may give priority to one approach compared to another based on what is more expensive, a comparison or a item move. Insertion Sort Insertion sort tries to reduce the number of key comparisons it performs compared to selection sort by not “doing anything” if things are sorted. Assume you had an collection of numbers in the following order… 10 18 25 30 23 17 45 35 There are 8 elements in the list. If we were to start at the front of the list – 10 18 25 & 30 are already sorted. Element 5 (23) however is smaller than element 4 (30) and so needs to be repositioned. We do this by copying the value at element 5 to a temporary holder, and then begin shifting the elements before it up one. So… Element 5 would be copied to a temporary holder 10 18 25 30 23 17 45 35 – T 23 Element 4 would shift to Element 5 10 18 25 30 30 17 45 35 – T 23 Element 3 would shift to Element 4 10 18 25 25 30 17 45 35 – T 23 Element 2 (18) is smaller than the temporary holder so we put the temporary holder value into Element 3. 10 18 23 25 30 17 45 35 – T 23   We now have a sorted list up to element 6. And so we would repeat the same process by moving element 6 to a temporary value and then shifting everything up by one from element 2 to element 5. As you can see, one major setback for this technique is the shifting values up one – this is because up to now we have been considering the collection to be an array. If however the collection was a linked list, we would not need to shift values up, but merely remove the link from the unsorted value and “reinsert” it in a sorted position. Which would reduce the number of transactions performed on the collection. So.. Insertion sort seems to perform better than selection sort – however an implementation is slightly more complicated. This is typical with most sorting algorithms – generally, greater performance leads to greater complexity. Also, insertion sort performs better if a collection of data is already sorted. If for instance you were handed a sorted collection of size n, then only n number of comparisons would need to be performed to verify that it is sorted. It’s important to note that insertion sort (array based) performs a number item moves – every time an item is “out of place” several items before it get shifted up. Shellsort – Diminishing Increment Sort So up to now we have covered Selection Sort & Insertion Sort. Selection Sort makes many comparisons and insertion sort (with an array) has the potential of making many item movements. Shellsort is an approach that takes the normal insertion sort and tries to reduce the number of item movements. In Shellsort, elements in a collection are viewed as sub-collections of a particular size. Each sub-collection is sorted so that the elements that are far apart move closer to their final position. Suppose we had a collection of 15 elements… 10 20 15 45 36 48 7 60 18 50 2 19 43 30 55 First we may view the collection as 7 sub-collections and sort each sublist, lets say at intervals of 7 10 60 55 – 20 18 – 15 50 – 45 2 – 36 19 – 48 43 – 7 30 10 55 60 – 18 20 – 15 50 – 2 45 – 19 36 – 43 48 – 7 30 (Sorted) We then sort each sublist at a smaller inter – lets say 4 10 55 60 18 – 20 15 50 2 – 45 19 36 43 – 48 7 30 10 18 55 60 – 2 15 20 50 – 19 36 43 45 – 7 30 48 (Sorted) We then sort elements at a distance of 1 (i.e. we apply a normal insertion sort) 10 18 55 60 2 15 20 50 19 36 43 45 7 30 48 2 7 10 15 18 19 20 30 36 43 45 48 50 55 (Sorted) The important thing with shellsort is deciding on the increment sequence of each sub-collection. From what I can tell, there isn’t any definitive method and depending on the order of your elements, different increment sequences may perform better than others. There are however certain increment sequences that you may want to avoid. An even based increment sequence (e.g. 2 4 8 16 32 …) should typically be avoided because it does not allow for even elements to be compared with odd elements until the final sort phase – which in a way would negate many of the benefits of using sub-collections. The performance on the number of comparisons and item movements of Shellsort is hard to determine, however it is considered to be considerably better than the normal insertion sort. Quicksort Quicksort uses a divide and conquer approach to sort a collection of items. The collection is divided into two sub-collections – and the two sub-collections are sorted and combined into one list in such a way that the combined list is sorted. The algorithm is in general pseudo code below… Divide the collection into two sub-collections Quicksort the lower sub-collection Quicksort the upper sub-collection Combine the lower & upper sub-collection together As hinted at above, quicksort uses recursion in its implementation. The real trick with quicksort is to get the lower and upper sub-collections to be of equal size. The size of a sub-collection is determined by what value the pivot is. Once a pivot is determined, one would partition to sub-collections and then repeat the process on each sub collection until you reach the base case. With quicksort, the work is done when dividing the sub-collections into lower & upper collections. The actual combining of the lower & upper sub-collections at the end is relatively simple since every element in the lower sub-collection is smaller than the smallest element in the upper sub-collection. Mergesort With quicksort, the average-case complexity was O(nlog2n) however the worst case complexity was still O(N*N). Mergesort improves on quicksort by always having a complexity of O(nlog2n) regardless of the best or worst case. So how does it do this? Mergesort makes use of the divide and conquer approach to partition a collection into two sub-collections. It then sorts each sub-collection and combines the sorted sub-collections into one sorted collection. The general algorithm for mergesort is as follows… Divide the collection into two sub-collections Mergesort the first sub-collection Mergesort the second sub-collection Merge the first sub-collection and the second sub-collection As you can see.. it still pretty much looks like quicksort – so lets see where it differs… Firstly, mergesort differs from quicksort in how it partitions the sub-collections. Instead of having a pivot – merge sort partitions each sub-collection based on size so that the first and second sub-collection of relatively the same size. This dividing keeps getting repeated until the sub-collections are the size of a single element. If a sub-collection is one element in size – it is now sorted! So the trick is how do we put all these sub-collections together so that they maintain their sorted order. Sorted sub-collections are merged into a sorted collection by comparing the elements of the sub-collection and then adjusting the sorted collection. Lets have a look at a few examples… Assume 2 sub-collections with 1 element each 10 & 20 Compare the first element of the first sub-collection with the first element of the second sub-collection. Take the smallest of the two and place it as the first element in the sorted collection. In this scenario 10 is smaller than 20 so 10 is taken from sub-collection 1 leaving that sub-collection empty, which means by default the next smallest element is in sub-collection 2 (20). So the sorted collection would be 10 20 Lets assume 2 sub-collections with 2 elements each 10 20 & 15 19 So… again we would Compare 10 with 15 – 10 is the winner so we add it to our sorted collection (10) leaving us with 20 & 15 19 Compare 20 with 15 – 15 is the winner so we add it to our sorted collection (10 15) leaving us with 20 & 19 Compare 20 with 19 – 19 is the winner so we add it to our sorted collection (10 15 19) leaving us with 20 & _ 20 is by default the winner so our sorted collection is 10 15 19 20. Make sense? Heapsort (still needs to be completed) So by now I am tired of sorting algorithms and trying to remember why they were so important. I think every year I go through this stuff I wonder to myself why are we made to learn about selection sort and insertion sort if they are so bad – why didn’t we just skip to Mergesort & Quicksort. I guess the only explanation I have for this is that sometimes you learn things so that you can implement them in future – and other times you learn things so that you know it isn’t the best way of implementing things and that you don’t need to implement it in future. Anyhow… luckily this is going to be the last one of my sorts for today. The first step in heapsort is to convert a collection of data into a heap. After the data is converted into a heap, sorting begins… So what is the definition of a heap? If we have to convert a collection of data into a heap, how do we know when it is a heap and when it is not? The definition of a heap is as follows: A heap is a list in which each element contains a key, such that the key in the element at position k in the list is at least as large as the key in the element at position 2k +1 (if it exists) and 2k + 2 (if it exists). Does that make sense? At first glance I’m thinking what the heck??? But then after re-reading my notes I see that we are doing something different – up to now we have really looked at data as an array or sequential collection of data that we need to sort – a heap represents data in a slightly different way – although the data is stored in a sequential collection, for a sequential collection of data to be in a valid heap – it is “semi sorted”. Let me try and explain a bit further with an example… Example 1 of Potential Heap Data Assume we had a collection of numbers as follows 1[1] 2[2] 3[3] 4[4] 5[5] 6[6] For this to be a valid heap element with value of 1 at position [1] needs to be greater or equal to the element at position [3] (2k +1) and position [4] (2k +2). So in the above example, the collection of numbers is not in a valid heap. Example 2 of Potential Heap Data Lets look at another collection of numbers as follows 6[1] 5[2] 4[3] 3[4] 2[5] 1[6] Is this a valid heap? Well… element with the value 6 at position 1 must be greater or equal to the element at position [3] and position [4]. Is 6 > 4 and 6 > 3? Yes it is. Lets look at element 5 as position 2. It must be greater than the values at [4] & [5]. Is 5 > 3 and 5 > 2? Yes it is. If you continued to examine this second collection of data you would find that it is in a valid heap based on the definition of a heap.

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• Handling HumanTask attachments in Oracle BPM 11g PS4FP+ (II)

  - by ccasares

  Retrieving uploaded attachments -UCM- As stated in my previous blog entry, Oracle BPM 11g 11.1.1.5.1 (aka PS4FP) introduced a new cool feature whereby you can use Oracle WebCenter Content (previously known as Oracle UCM) as the repository for the human task attached documents. For more information about how to use or enable this feature, have a look here. The attachment scope (either TASK or PROCESS) also applies to UCM-attachments. But even with this other feature, one question might arise when using UCM attachments. How can I get them from within the process? The first answer would be to use the same getTaskAttachmentContents() XPath function already explained in my previous blog entry. In fact, that's the way it should be. But in Oracle BPM 11g 11.1.1.5.1 (PS4FP) and 11.1.1.6.0 (PS5) there's a bug that prevents you to do that. If you invoke such function against a UCM-attachment, you'll get a null content response (bug#13907552). Even if the attachment was correctly uploaded. While this bug gets fixed, next I will show a workaround that lets me to retrieve the UCM-attached documents from within a BPM process. Besides, the sample will show how to interact with WCC API from within a BPM process.Aside note: I suggest you to read my previous blog entry about Human Task attachments where I briefly describe some concepts that are used next, such as the execData/attachment[] structure. Sample Process I will be using the following sample process: A dummy UserTask using "HumanTask2" Human Task, followed by an Embedded Subprocess that will retrieve the attachments payload. In this case, and here's the key point of the sample, we will retrieve such payload using WebCenter Content WebService API (IDC): and once retrieved, we will write each of them back to a file in the server using a File Adapter service: In detail:  We will use the same attachmentCollection XSD structure and same BusinessObject definition as in the previous blog entry. However we create a separate variable, named attachmentUCM, based on such BusinessObject. We will still need to keep a copy of the HumanTask output's execData structure. Therefore we need to create a new variable of type TaskExecutionData (different one than the other used for non-UCM attachments): As in the non-UCM attachments flow, in the output tab of the UserTask mapping, we'll keep a copy of the execData structure: Now we get into the embedded subprocess that will retrieve the attachments' payload. First, and using an XSLT transformation, we feed the attachmentUCM variable with the following information: The name of each attachment (from execData/attachment/name element) The WebCenter Content ID of the uploaded attachment. This info is stored in execData/attachment/URI element with the format ecm://<id>. As we just want the numeric <id>, we need to get rid of the protocol prefix ("ecm://"). We do so with some XPath functions as detailed below: with these two functions being invoked, respectively: We, again, set the target payload element with an empty string, to get the <payload></payload> tag created. The complete XSLT transformation is shown below. Remember that we're using the XSLT for-each node to create as many target structures as necessary.  Once we have fed the attachmentsUCM structure and so it now contains the name of each of the attachments along with each WCC unique id (dID), it is time to iterate through it and get the payload. Therefore we will use a new embedded subprocess of type MultiInstance, that will iterate over the attachmentsUCM/attachment[] element: In each iteration we will use a Service activity that invokes WCC API through a WebService. Follow these steps to create and configure the Partner Link needed: Login to WCC console with an administrator user (i.e. weblogic). Go to Administration menu and click on "Soap Wsdls" link. We will use the GetFile service to retrieve a file based on its dID. Thus we'll need such service WSDL definition that can be downloaded by clicking the GetFile link. Save the WSDL file in your JDev project folder. In the BPM project's composite view, drag & drop a WebService adapter to create a new External Reference, based on the just added GetFile.wsdl. Name it UCM_GetFile. WCC services are secured through basic HTTP authentication. Therefore we need to enable the just created reference for that: Right-click the reference and click on Configure WS Policies. Under the Security section, click "+" to add the "oracle/wss_username_token_client_policy" policy The last step is to set the credentials for the security policy. For the sample we will use the admin user for WCC (weblogic/welcome1). Open the composite.xml file and select the Source view. Search for the UCM_GetFile entry and add the following highlighted elements into it:   <reference name="UCM_GetFile" ui:wsdlLocation="GetFile.wsdl">     <interface.wsdl interface="http://www.stellent.com/GetFile/#wsdl.interface(GetFileSoap)"/>     <binding.ws port="http://www.stellent.com/GetFile/#wsdl.endpoint(GetFile/GetFileSoap)"                 location="GetFile.wsdl" soapVersion="1.1">       <wsp:PolicyReference URI="oracle/wss_username_token_client_policy"                            orawsp:category="security" orawsp:status="enabled"/>       <property name="weblogic.wsee.wsat.transaction.flowOption"                 type="xs:string" many="false">WSDLDriven</property>       <property name="oracle.webservices.auth.username"                 type="xs:string">weblogic</property>       <property name="oracle.webservices.auth.password"                 type="xs:string">welcome1</property>     </binding.ws>   </reference> Now the new external reference is ready: Once the reference has just been created, we should be able now to use it from our BPM process. However we find here a problem. The WCC GetFile service operation that we will use, GetFileByID, accepts as input a structure similar to this one, where all element tags are optional: <get:GetFileByID xmlns:get="http://www.stellent.com/GetFile/">    <get:dID>?</get:dID>   <get:rendition>?</get:rendition>   <get:extraProps>      <get:property>         <get:name>?</get:name>         <get:value>?</get:value>      </get:property>   </get:extraProps></get:GetFileByID> and we need to fill up just the <get:dID> tag element. Due to some kind of restriction or bug on WCC, the rest of the tag elements must NOT be sent, not even empty (i.e.: <get:rendition></get:rendition> or <get:rendition/>). A sample request that performs the query just by the dID, must be in the following format: <get:GetFileByID xmlns:get="http://www.stellent.com/GetFile/">   <get:dID>12345</get:dID></get:GetFileByID> The issue here is that the simple mapping in BPM does create empty tags being a sample result as follows: <get:GetFileByID xmlns:get="http://www.stellent.com/GetFile/"> <get:dID>12345</get:dID> <get:rendition/> <get:extraProps/> </get:GetFileByID> Although the above structure is perfectly valid, it is not accepted by WCC. Therefore, we need to bypass the problem. The workaround we use (many others are available) is to add a Mediator component between the BPM process and the Service that simply copies the input structure from BPM but getting rid of the empty tags. Follow these steps to configure the Mediator: Drag & drop a new Mediator component into the composite. Uncheck the creation of the SOAP bindings and use the Interface Definition from WSDL template and select the existing GetFile.wsdl Double click in the mediator to edit it. Add a static routing rule to the GetFileByID operation, of type Service and select References/UCM_GetFile/GetFileByID target service: Create the request and reply XSLT mappers: Make sure you map only the dID element in the request: And do an Auto-mapper for the whole response: Finally, we can now add and configure the Service activity in the BPM process. Drag & drop it to the embedded subprocess and select the NormalizedGetFile service and getFileByID operation: Map both the input: ...and the output: Once this embedded subprocess ends, we will have all attachments (name + payload) in the attachmentsUCM variable, which is the main goal of this sample. But in order to test everything runs fine, we finish the sample writing each attachment to a file. To that end we include a final embedded subprocess to concurrently iterate through each attachmentsUCM/attachment[] element: On each iteration we will use a Service activity that invokes a File Adapter write service. In here we have two important parameters to set. First, the payload itself. The file adapter awaits binary data in base64 format (string). We have to map it using XPath (Simple mapping doesn't recognize a String as a base64-binary valid target): Second, we must set the target filename using the Service Properties dialog box: Again, note how we're making use of the loopCounter index variable to get the right element within the embedded subprocess iteration. Final blog entry about attachments will handle how to inject documents to Human Tasks from the BPM process and how to share attachments between different User Tasks. Will come soon. Again, once I finish will all posts on this matter, I will upload the whole sample project to java.net.

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• VMware Workstation Easy Install is unable to install Windows 8 with a product key specified

  - by Hippo

  I recently attempted to install Windows 8 Enterprise Edition in VMware Workstation. It specified that Easy Install would be used, and requested for the product key, for which I entered the generated MSDN key. This didn't work - the installation goes into a loop with each iteration of the loop ending with the following screen: The guest reboots and the process repeats after clicking "OK". Has anyone been able to successfully install their MSDN image with Easy Install in Workstation?

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• Subclipse - How to mark a major revision?

  - by James P.

  Hi, How does one go about marking a major revision using the Subclipse plugin? I'd like to mark a project at the end of an iteration such that it's possible to revert if necessary without going through endless changes. TIA.

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• Windows PE autorun scripts

  - by tearman

  I've set up a Windows Preinstallation Environment on a USB Thumb Drive (version from the latest iteration of the Windows Automated Install Kit/WAIK), and I'm working on getting a deployment environment set up. However, we'd like to make it so our Level 1 technicians can use the deployment system, and because of this, I've written several batch files to minimize the amount of command line work the technicians have to do. Is there a way I can get these scripts to autorun after the PE environment has finished initializing?

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• Amazon S3 Iterating Through Multi-Page Results. (withMarker)

  - by Jitu

  Trying to iterate through AmazonS3 that has around 5000+ keys stored in the bucket, used sample code based on provided link on Amazon Developer Guide http://docs.amazonwebservices.com/AmazonS3/latest/dev/ListingObjectKeysUsingNetSDK.html Issue is iteration fails when NexMarker is passed which has length of more than 128 string characters, which seems unusal as withMarker accepts string as parameter and there is no documentation on limit to withMarker. request.Marker = response.NextMarker; Has anyone faced similar issue. Thanks in advance.

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• mod_rewrite all but two files causing loop

  - by mpounsett

  I'm trying to set up a web site to allow the creation of a semaphore file to close the site. The logic I want to follow is: when the semaphore file exists and the request is not for /style.css or /favicon.icon show the content of /closed.html I have 1 and 3 working, but my exceptions for 2 result in a processing loop when style.css or favicon.ico are requested. This is my most recent attempt: RewriteEngine on RewriteCond %{REQUEST_URI} !^/style.css RewriteCond %{REQUEST_URI} !^/favicon.ico RewriteCond /usr/local/etc/site/closed -f RewriteRule ^.*$ /closed.html [L] This is in a VirtualHost block, not in a Directory. There is no .htaccess file in play. I have also recently tried this, based on an answer I found elsewhere, but with the same (looping) result: RewriteCond %{REQUEST_URI} ^/style.css [OR] RewriteCond %{REQUEST_URI} ^/favicon.ico RewriteRule ^.*$ - [L] RewriteCond /usr/local/etc/site/closed -f RewriteRule ^.*$ /closed.html [L] I expect a request for /style.css or /favicon.ico to fail to match one of the first two rewrite conditions, which should prevent the URI from being rewritten, which should stop the mod_rewrite iteration. However, mod_rewrite seems to think the URI has been rewritten in those cases, and iterates over the rules again (and again, and again). The above works properly in all cases except for style.css or favicon.ico. In those cases I exceed the loop limits. What am I missing here to cause the rewrite iteration to stop when someone requests style.css or favicon.ico? EDIT: Here's a loglevel 9 example of what happens using the first ruleset when a request arrives for /style.css. This is just the first two iterations.. it continues to loop identically until the limit is reached. 2001:4900:1044:0:145f:826e:6436:dc1 - - [29/May/2014:15:29:26 +0000] [host.example/sid#80c1c48b0][rid#80c1db0a0/initial] (2) init rewrite engine with requested uri /style.css 2001:4900:1044:0:145f:826e:6436:dc1 - - [29/May/2014:15:29:26 +0000] [host.example/sid#80c1c48b0][rid#80c1db0a0/initial] (3) applying pattern '^.*$' to uri '/style.css' 2001:4900:1044:0:145f:826e:6436:dc1 - - [29/May/2014:15:29:26 +0000] [host.example/sid#80c1c48b0][rid#80c1db0a0/initial] (4) RewriteCond: input='/style.css' pattern='!^/style.css' => not-matched 2001:4900:1044:0:145f:826e:6436:dc1 - - [29/May/2014:15:29:26 +0000] [host.example/sid#80c1c48b0][rid#80c1db0a0/initial] (1) pass through /style.css 2001:4900:1044:0:145f:826e:6436:dc1 - - [29/May/2014:15:29:26 +0000] [host.example/sid#80c1c48b0][rid#80c1dd0a0/initial] (2) init rewrite engine with requested uri /style.css 2001:4900:1044:0:145f:826e:6436:dc1 - - [29/May/2014:15:29:26 +0000] [host.example/sid#80c1c48b0][rid#80c1dd0a0/initial] (3) applying pattern '^.*$' to uri '/style.css' 2001:4900:1044:0:145f:826e:6436:dc1 - - [29/May/2014:15:29:26 +0000] [host.example/sid#80c1c48b0][rid#80c1dd0a0/initial] (4) RewriteCond: input='/style.css' pattern='!^/style.css' => not-matched 2001:4900:1044:0:145f:826e:6436:dc1 - - [29/May/2014:15:29:26 +0000] [host.example/sid#80c1c48b0][rid#80c1dd0a0/initial] (1) pass through /style.css

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