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• Neo4j increasing latency as SKIP increases on Cypher query + REST API

  - by voldomazta

  My setup: Java(TM) SE Runtime Environment (build 1.7.0_45-b18) Java HotSpot(TM) 64-Bit Server VM (build 24.45-b08, mixed mode) Neo4j 2.0.0-M06 Enterprise First I made sure I warmed up the cache by executing the following: START n=node(*) RETURN COUNT(n); START r=relationship(*) RETURN count(r); The size of the table is 63,677 nodes and 7,169,995 relationships Now I have the following query: START u1=node:node_auto_index('uid:39') MATCH (u1:user)-[w:WANTS]->(c:card)<-[h:HAS]-(u2:user) WHERE u2.uid <> 39 WITH u2.uid AS uid, (CASE WHEN w.qty < h.qty THEN w.qty ELSE h.qty END) AS have RETURN uid, SUM(have) AS total ORDER BY total DESC SKIP 0 LIMIT 25 This UID has about 40k+ results that I want to be able to put a pagination to. The initial skip was around 773ms. I tried page 2 (skip 25) and the latency was around the same even up to page 500 it only rose up to 900ms so I didn't really bother. Now I tried some fast forward paging and jumped by thousands so I did 1000, then 2000, then 3000. I was hoping the ORDER BY arrangement will already have been cached by Neo4j and using SKIP will just move to that index in the result and wont have to iterate through each one again. But for each thousand skip I made the latency increased by alot. It's not just cache warming because for one I already warmed up the cache and two, I tried the same skip a couple of times for each skip and it yielded the same results: SKIP 0: 773ms SKIP 1000: 1369ms SKIP 2000: 2491ms SKIP 3000: 3899ms SKIP 4000: 5686ms SKIP 5000: 7424ms Now who the hell would want to view 5000 pages of results? 40k even?! :) Good point! I will probably put a cap on the maximum results a user can view but I was just curious about this phenomenon. Will somebody please explain why Neo4j seems to be re-iterating through stuff which appears to be already known to it? Here is my profiling for the 0 skip: ==> ColumnFilter(symKeys=["uid", " INTERNAL_AGGREGATE65c4d6a2-1930-4f32-8fd9-5e4399ce6f14"], returnItemNames=["uid", "total"], _rows=25, _db_hits=0) ==> Slice(skip="Literal(0)", _rows=25, _db_hits=0) ==> Top(orderBy=["SortItem(Cached( INTERNAL_AGGREGATE65c4d6a2-1930-4f32-8fd9-5e4399ce6f14 of type Any),false)"], limit="Add(Literal(0),Literal(25))", _rows=25, _db_hits=0) ==> EagerAggregation(keys=["uid"], aggregates=["( INTERNAL_AGGREGATE65c4d6a2-1930-4f32-8fd9-5e4399ce6f14,Sum(have))"], _rows=41659, _db_hits=0) ==> ColumnFilter(symKeys=["have", "u1", "uid", "c", "h", "w", "u2"], returnItemNames=["uid", "have"], _rows=146826, _db_hits=0) ==> Extract(symKeys=["u1", "c", "h", "w", "u2"], exprKeys=["uid", "have"], _rows=146826, _db_hits=587304) ==> Filter(pred="((NOT(Product(u2,uid(0),true) == Literal(39)) AND hasLabel(u1:user(0))) AND hasLabel(u2:user(0)))", _rows=146826, _db_hits=146826) ==> TraversalMatcher(trail="(u1)-[w:WANTS WHERE (hasLabel(NodeIdentifier():card(1)) AND hasLabel(NodeIdentifier():card(1))) AND true]->(c)<-[h:HAS WHERE (NOT(Product(NodeIdentifier(),uid(0),true) == Literal(39)) AND hasLabel(NodeIdentifier():user(0))) AND true]-(u2)", _rows=146826, _db_hits=293696) And for the 5000 skip: ==> ColumnFilter(symKeys=["uid", " INTERNAL_AGGREGATE99329ea5-03cd-4d53-a6bc-3ad554b47872"], returnItemNames=["uid", "total"], _rows=25, _db_hits=0) ==> Slice(skip="Literal(5000)", _rows=25, _db_hits=0) ==> Top(orderBy=["SortItem(Cached( INTERNAL_AGGREGATE99329ea5-03cd-4d53-a6bc-3ad554b47872 of type Any),false)"], limit="Add(Literal(5000),Literal(25))", _rows=5025, _db_hits=0) ==> EagerAggregation(keys=["uid"], aggregates=["( INTERNAL_AGGREGATE99329ea5-03cd-4d53-a6bc-3ad554b47872,Sum(have))"], _rows=41659, _db_hits=0) ==> ColumnFilter(symKeys=["have", "u1", "uid", "c", "h", "w", "u2"], returnItemNames=["uid", "have"], _rows=146826, _db_hits=0) ==> Extract(symKeys=["u1", "c", "h", "w", "u2"], exprKeys=["uid", "have"], _rows=146826, _db_hits=587304) ==> Filter(pred="((NOT(Product(u2,uid(0),true) == Literal(39)) AND hasLabel(u1:user(0))) AND hasLabel(u2:user(0)))", _rows=146826, _db_hits=146826) ==> TraversalMatcher(trail="(u1)-[w:WANTS WHERE (hasLabel(NodeIdentifier():card(1)) AND hasLabel(NodeIdentifier():card(1))) AND true]->(c)<-[h:HAS WHERE (NOT(Product(NodeIdentifier(),uid(0),true) == Literal(39)) AND hasLabel(NodeIdentifier():user(0))) AND true]-(u2)", _rows=146826, _db_hits=293696) The only difference is the LIMIT clause on the Top function. I hope we can make this work as intended, I really don't want to delve into doing an embedded Neo4j + my own Jetty REST API for the web app.

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• C# - Parse HTML source as XML

  - by fonix232

  I would like to read in a dynamic URL what contains a HTML file, and read it like an XML file, based on nodes (HTML tags). Is this somehow possible? I mean, there is this HTML code: <table class="bidders" cellpadding="0" cellspacing="0"> <tr class="bidRow4"> <td>kucik (automata)</td> <td class="right">9 374 Ft</td> <td class="bidders_date">2010-06-10 18:19:52</td> </tr> <tr class="bidRow4"> <td>macszaf (automata)</td> <td class="right">9 373 Ft</td> <td class="bidders_date">2010-06-10 18:19:52</td> </tr> <tr class="bidRow2"> <td>kucik (automata)</td> <td class="right">9 372 Ft</td> <td class="bidders_date">2010-06-10 18:19:42</td> </tr> <tr class="bidRow2"> <td>macszaf (automata)</td> <td class="right">9 371 Ft</td> <td class="bidders_date">2010-06-10 18:19:42</td> </tr> <tr class="bidRow0"> <td>kucik (automata)</td> <td class="right">9 370 Ft</td> <td class="bidders_date">2010-06-10 18:19:32</td> </tr> <tr class="bidRow0"> <td>macszaf (automata)</td> <td class="right">9 369 Ft</td> <td class="bidders_date">2010-06-10 18:19:32</td> </tr> <tr class="bidRow8"> <td>kucik (automata)</td> <td class="right">9 368 Ft</td> <td class="bidders_date">2010-06-10 18:19:22</td> </tr> <tr class="bidRow8"> <td>macszaf (automata)</td> <td class="right">9 367 Ft</td> <td class="bidders_date">2010-06-10 18:19:22</td> </tr> <tr class="bidRow6"> <td>kucik (automata)</td> <td class="right">9 366 Ft</td> <td class="bidders_date">2010-06-10 18:19:12</td> </tr> <tr class="bidRow6"> <td>macszaf (automata)</td> <td class="right">9 365 Ft</td> <td class="bidders_date">2010-06-10 18:19:12</td> </tr> </table> I want to parse this into a ListView (or a Grid) to create rows with the data contained. All tr are different row, and all td in a given td is a column in the given row. And also I want it to be as fast as possible, as it would update itself in 5 seconds. Is there any library for this?

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• Choosing a type for search results in C#

  - by Chris M

  I have a result set that will never exceed 500; the results that come back from the web-service are assigned to a search results object. The data from the webservice is about 2mb; the bit I want to use is about a third of each record, so this allows me to cache and quickly manipulate it. I want to be able to sort and filter the results with the least amount of overhead and as fast as possible so I used the VCSKICKS timing class to measure their performance Average Total (10,000) Type Create Sort Create Sort HashSet 0.1579 0.0003 1579 3 IList 0.0633 0.0002 633 2 IQueryable 0.0072 0.0432 72 432 Measured in Seconds using http://www.vcskicks.com/algorithm-performance.php I created the hashset through a for loop over the web-service response (adding to the hashset). The List & IQueryable were created using LINQ. Question I can understand why HashSet takes longer to create (the foreach loop vs linq); but why would IQueryable take longer to sort than the other two; and finally is there a better way to assign the HashSet. Thanks Actual Program public class Program { private static AuthenticationHeader _authHeader; private static OPSoapClient _opSession; private static AccommodationSearchResponse _searchResults; private static HashSet<SearchResults> _myHash; private static IList<SearchResults> _myList; private static IQueryable<SearchResults> _myIQuery; static void Main(string[] args) { #region Setup WebService _authHeader = new AuthenticationHeader { UserName = "xx", Password = "xx" }; _opSession = new OPSoapClient(); #region Setup Search Results _searchResults = _opgSession.SearchCR(_authHeader, "ENG", "GBP", "GBR"); #endregion Setup Search Results #endregion Setup WebService // HASHSET SpeedTester hashTest = new SpeedTester(TestHashSet); hashTest.RunTest(); Console.WriteLine("- Hash Test \nAverage Running Time: {0}; Total Time: {1}", hashTest.AverageRunningTime, hashTest.TotalRunningTime); SpeedTester hashSortTest = new SpeedTester(TestSortingHashSet); hashSortTest.RunTest(); Console.WriteLine("- Hash Sort Test \nAverage Running Time: {0}; Total Time: {1}", hashSortTest.AverageRunningTime, hashSortTest.TotalRunningTime); // ILIST SpeedTester listTest = new SpeedTester(TestList); listTest.RunTest(); Console.WriteLine("- List Test \nAverage Running Time: {0}; Total Time: {1}", listTest.AverageRunningTime, listTest.TotalRunningTime); SpeedTester listSortTest = new SpeedTester(TestSortingList); listSortTest.RunTest(); Console.WriteLine("- List Sort Test \nAverage Running Time: {0}; Total Time: {1}", listSortTest.AverageRunningTime, listSortTest.TotalRunningTime); // IQUERIABLE SpeedTester iqueryTest = new SpeedTester(TestIQueriable); iqueryTest.RunTest(); Console.WriteLine("- iquery Test \nAverage Running Time: {0}; Total Time: {1}", iqueryTest.AverageRunningTime, iqueryTest.TotalRunningTime); SpeedTester iquerySortTest = new SpeedTester(TestSortableIQueriable); iquerySortTest.RunTest(); Console.WriteLine("- iquery Sort Test \nAverage Running Time: {0}; Total Time: {1}", iquerySortTest.AverageRunningTime, iquerySortTest.TotalRunningTime); } static void TestHashSet() { var test = _searchResults.Items; _myHash = new HashSet<SearchResults>(); foreach(var x in test) { _myHash.Add(new SearchResults { Ref = x.Ref, Price = x.StandardPrice }); } } static void TestSortingHashSet() { var sorted = _myHash.OrderBy(s => s.Price); } static void TestList() { var test = _searchResults.Items; _myList = (from x in test select new SearchResults { Ref = x.Ref, Price = x.StandardPrice }).ToList(); } static void TestSortingList() { var sorted = _myList.OrderBy(s => s.Price); } static void TestIQueriable() { var test = _searchResults.Items; _myIQuery = (from x in test select new SearchResults { Ref = x.Ref, Price = x.StandardPrice }).AsQueryable(); } static void TestSortableIQueriable() { var sorted = _myIQuery.OrderBy(s => s.Price); } }

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• Why does this Quicksort work?

  - by IVlad

  I find this Quicksort partitioning approach confusing and wrong, yet it seems to work. I am referring to this pseudocode. Note: they also have a C implementation at the end of the article, but it's very different from their pseudocode, so I don't care about that. I have also written it in C like this, trying to stay true to the pseudocode as much as possible, even if that means doing some weird C stuff: #include <stdio.h> int partition(int a[], int p, int r) { int x = a[p]; int i = p - 1; int j = r + 1; while (1) { do j = j - 1; while (!(a[j] <= x)); do i = i + 1; while (!(a[i] >= x)); if (i < j) { int t = a[i]; a[i] = a[j]; a[j] = t; } else { for (i = 1; i <= a[0]; ++i) printf("%d ", a[i]); printf("- %d\n", j); return j; } } } int main() { int a[100] = //{8, 6,10,13,15,8,3,2,12}; {7, 7, 6, 2, 3, 8, 4, 1}; partition(a, 1, a[0]); return 0; } If you run this, you'll get the following output: 1 6 2 3 4 8 7 - 5 However, this is wrong, isn't it? Clearly a[5] does not have all the values before it lower than it, since a[2] = 6 > a[5] = 4. Not to mention that 7 is supposed to be the pivot (the initial a[p]) and yet its position is both incorrect and lost. The following partition algorithm is taken from wikipedia: int partition2(int a[], int p, int r) { int x = a[r]; int store = p; for (int i = p; i < r; ++i) { if (a[i] <= x) { int t = a[i]; a[i] = a[store]; a[store] = t; ++store; } } int t = a[r]; a[r] = a[store]; a[store] = t; for (int i = 1; i <= a[0]; ++i) printf("%d ", a[i]); printf("- %d\n", store); return store; } And produces this output: 1 6 2 3 8 4 7 - 1 Which is a correct result in my opinion: the pivot (a[r] = a[7]) has reached its final position. However, if I use the initial partitioning function in the following algorithm: void Quicksort(int a[], int p, int r) { if (p < r) { int q = partition(a, p, r); // initial partitioning function Quicksort(a, p, q); Quicksort(a, q + 1, r); // I'm pretty sure q + r was a typo, it doesn't work with q + r. } } ... it seems to be a correct sorting algorithm. I tested it out on a lot of random inputs, including all 0-1 arrays of length 20. I have also tried using this partition function for a selection algorithm, in which it failed to produce correct results. It seems to work and it's even very fast as part of the quicksort algorithm however. So my questions are: Can anyone post an example on which the algorithm DOESN'T work? If not, why does it work, since the partitioning part seems to be wrong? Is this another partitioning approach that I don't know about?

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• What is the fastest way to Initialize a multi-dimensional array to non-default values in .NET?

  - by AMissico

  How do I initialize a multi-dimensional array of a primitive type as fast as possible? I am stuck with using multi-dimensional arrays. My problem is performance. The following routine initializes a 100x100 array in approx. 500 ticks. Removing the int.MaxValue initialization results in approx. 180 ticks just for the looping. Approximately 100 ticks to create the array without looping and without initializing to int.MaxValue. Routines similiar to this are called a few hundred-thousand to several million times during a "run". The array size will not change during a run and arrays are created one-at-a-time, used, then discarded, and a new array created. A "run" which may last from one minute (using 10x10 arrays) to forty-five minutes (100x100). The application creates arrays of int, bool, and struct. There can be multiple "runs" executing at same time, but are not because performance degrades terribly. I am using 100x100 as a base-line. I am open to suggestions on how to optimize this non-default initialization of an array. One idea I had is to use a smaller primitive type when available. For instance, using byte instead of int, saves 100 ticks. I would be happy with this, but I am hoping that I don't have to change the primitive data type. public int[,] CreateArray(Size size) { int[,] array = new int[size.Width, size.Height]; for (int x = 0; x < size.Width; x++) { for (int y = 0; y < size.Height; y++) { array[x, y] = int.MaxValue; } } return array; } Down to 450 ticks with the following: public int[,] CreateArray1(Size size) { int iX = size.Width; int iY = size.Height; int[,] array = new int[iX, iY]; for (int x = 0; x < iX; x++) { for (int y = 0; y < iY; y++) { array[x, y] = int.MaxValue; } } return array; } Down to approximately 165 ticks after a one-time initialization of 2800 ticks. (See my answer below.) If I can get stackalloc to work with multi-dimensional arrays, I should be able to get the same performance without having to intialize the private static array. private static bool _arrayInitialized5; private static int[,] _array5; public static int[,] CreateArray5(Size size) { if (!_arrayInitialized5) { int iX = size.Width; int iY = size.Height; _array5 = new int[iX, iY]; for (int x = 0; x < iX; x++) { for (int y = 0; y < iY; y++) { _array5[x, y] = int.MaxValue; } } _arrayInitialized5 = true; } return (int[,])_array5.Clone(); } Down to approximately 165 ticks without using the "clone technique" above. (See my answer below.) I am sure I can get the ticks lower, if I can just figure out the return of CreateArray9. public unsafe static int[,] CreateArray8(Size size) { int iX = size.Width; int iY = size.Height; int[,] array = new int[iX, iY]; fixed (int* pfixed = array) { int count = array.Length; for (int* p = pfixed; count-- > 0; p++) *p = int.MaxValue; } return array; }

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• jQuery hold form submit until "continue" button pressed

  - by Seán McCabe

  I am trying to submit a form, which I have had working, but have now modified it to include a modal jQuery UI box, so that it won't submit until the user presses "continue". I've had various problems with this, including getting the form to hold until that button is pressed, but I think I have found a solution to that, but implementing it, I am getting a SyntaxError which I can't find the source of. With the help of kevin B managed to find the answer was the form was submitting, but the returned JSON response wasn't quite formatted right. The response was that the form wasn't being submitted, so that problem is still occurring. So updated the code with the provided feedback, now need to find out why the form isnt submitting. I know its something to do with the 2nd function isnt recognising the submit button has been pressed, so need to know how to submit that form data without the form needing to be submitted again. Below is the new code: function submitData() { $("#submitProvData").submit(function(event) { event.preventDefault(); var gTotal, sTotal, dfd; var dfd = new $.Deferred(); $('html,body').animate({ scrollTop: 0 }, 'fast'); $("#submitProvData input").css("border", "1px solid #aaaaaa"); $("#submitProvData input[readonly='readonly']").css("border", "none"); sTotal = $('#summaryTotal').val(); gTotal = $('#gptotal').val(); if(gTotal !== 'sTotal'){ $("#newsupinvbox").append('<div id="newsupinvdiagbox" title="Warning - Totals do not match" class="hidden"><p>Press "Continue", to submit the invoice flagged for attention.</p> <br /><p class="italic">or</p><br /> <p>Press "Correct" to correct the discrepancy.</p></div>') //CREATE DIV //SET $("#newsupinvdiagbox").dialog({ resizable: false, autoOpen:false, modal: true, draggable: false, width:380, height:240, closeOnEscape: false, position: ['center',20], buttons: { 'Continue': function() { $(this).dialog('close'); reData(); }, // end continue button 'Correct': function() { $(this).dialog('close'); return false; } //end cancel button }//end buttons });//end dialog $('#newsupinvdiagbox').dialog('open'); } return false; }); } function reData() { console.log('submitted'); $("#submitProvData").submit(function(resubmit){ console.log('form submit'); var formData; formData = new FormData($(this)[0]); $.ajax({ type: "POST", url: "functions/invoicing_upload_provider.php", data: formData, async: false, success: function(result) { $.each($.parseJSON(result), function(item, value){ if(item == 'Success'){ $('#newsupinv_window_message_success_mes').html('The provider invoice was uploaded successfully.'); $('#newsupinv_window_message_success').fadeIn(300, function (){ reset(); }).delay(2500).fadeOut(700); } else if(item == 'Error'){ $('#newsupinv_window_message_error_mes').html(value); $('#newsupinv_window_message_error').fadeIn(300).delay(3000).fadeOut(700); } else if(item == 'Warning'){ $('#newsupinv_window_message_warning_mes').html(value); $('#newsupinv_window_message_warning').fadeIn(300, function (){ reset(); }).delay(2500).fadeOut(700); } }); }, error: function() { $('#newsupinv_window_message_error_mes').html("An error occured, the form was not submitted"); $('#newsupinv_window_message_error').fadeIn(300); $('#newsupinv_window_message_error').delay(3000).fadeOut(700); }, cache: false, contentType: false, processData: false }); }); }

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• Yet another C# Deadlock Debugging Question

  - by Roo

  Hi All, I have a multi-threaded application build in C# using VS2010 Professional. It's quite a large application and we've experienced the classing GUI cross-threading and deadlock issues before, but in the past month we've noticed the appears to lock up when left idle for around 20-30 minutes. The application is irresponsive and although it will repaint itself when other windows are dragged in front of the application and over it, the GUI still appears to be locked... interstingly (unlike if the GUI thread is being used for a considerable amount of time) the Close, Maximise and minimise buttons are also irresponsive and when clicked the little (Not Responding...) text is not displayed in the title of the application i.e. Windows still seems to think it's running fine. If I break/pause the application using the debugger, and view the threads that are running. There are 3 threads of our managed code that are running, and a few other worker threads whom the source code cannot be displayed for. The 3 threads that run are: The main/GUI thread A thread that loops indefinitely A thread that loops indefinitely If I step into threads 2 and 3, they appear to be looping correctly. They do not share locks (even with the main GUI thread) and they are not using the GUI thread at all. When stepping into the main/GUI thread however, it's broken on Application.Run... This problem screams deadlock to me, but what I don't understand is if it's deadlock, why can't I see the line of code the main/GUI thread is hanging on? Any help will be greatly appreciated! Let me know if you need more information... Cheers, Roo -----------------------------------------------------SOLUTION-------------------------------------------------- Okay, so the problem is now solved. Thanks to everyone for their suggestions! Much appreciated! I've marked the answer that solved my initial problem of determining where on the main/UI thread the application hangs (I handn't turned off the "Enable Just My Code" option). The overall issue I was experiencing was indeed Deadlock, however. After obtaining the call-stack and popping the top half of it into Google I came across this which explains exactly what I was experiencing... http://timl.net/ This references a lovely guide to debugging the issue... http://www.aaronlerch.com/blog/2008/12/15/debugging-ui/ This identified a control I was constructing off the GUI thread. I did know this, however, and was marshalling calls correctly, but what I didn't realise was that behind the scenes this Control was subscribing to an event or set of events that are triggered when e.g. a Windows session is unlocked or the screensaver exits. These calls are always made on the main/UI thread and were blocking when it saw the call was made on the incorrect thread. Kim explains in more detail here... http://krgreenlee.blogspot.com/2007/09/onuserpreferencechanged-hang.html In the end I found an alternative solution which did not require this Control off the main/UI thread. That appears to have solved the problem and the application no longer hangs. I hope this helps anyone who's confronted by a similar problem. Thanks again to everyone on here who helped! (and indirectly, the delightful bloggers I've referenced above!) Roo -----------------------------------------------------SOLUTION II-------------------------------------------------- Aren't threading issues delightful...you think you've solved it, and a month down the line it pops back up again. I still believe the solution above resolved an issue that would cause simillar behaviour, but we encountered the problem again. As we spent a while debugging this, I thought I'd update this question with our (hopefully) final solution: The problem appears to have been a bug in the Infragistics components in the WinForms 2010.1 release (no hot fixes). We had been running from around the time the freeze issue appeared (but had also added a bunch of other stuff too). After upgrading to WinForms 2010.3, we've yet to reproduce the issue (deja vu). See my question here for a bit more information: 'http://stackoverflow.com/questions/4077822/net-4-0-and-the-dreaded-onuserpreferencechanged-hang'. Hans has given a nice summary of the general issue. I hope this adds a little to the suggestions/information surrounding the nutorious OnUserPreferenceChanged Hang (or whatever you'd like to call it). Cheers, Roo

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• Code runs 6 times slower with 2 threads than with 1

  - by Edward Bird

  So I have written some code to experiment with threads and do some testing. The code should create some numbers and then find the mean of those numbers. I think it is just easier to show you what I have so far. I was expecting with two threads that the code would run about 2 times as fast. Measuring it with a stopwatch I think it runs about 6 times slower! void findmean(std::vector<double>*, std::size_t, std::size_t, double*); int main(int argn, char** argv) { // Program entry point std::cout << "Generating data..." << std::endl; // Create a vector containing many variables std::vector<double> data; for(uint32_t i = 1; i <= 1024 * 1024 * 128; i ++) data.push_back(i); // Calculate mean using 1 core double mean = 0; std::cout << "Calculating mean, 1 Thread..." << std::endl; findmean(&data, 0, data.size(), &mean); mean /= (double)data.size(); // Print result std::cout << " Mean=" << mean << std::endl; // Repeat, using two threads std::vector<std::thread> thread; std::vector<double> result; result.push_back(0.0); result.push_back(0.0); std::cout << "Calculating mean, 2 Threads..." << std::endl; // Run threads uint32_t halfsize = data.size() / 2; uint32_t A = 0; uint32_t B, C, D; // Split the data into two blocks if(data.size() % 2 == 0) { B = C = D = halfsize; } else if(data.size() % 2 == 1) { B = C = halfsize; D = hsz + 1; } // Run with two threads thread.push_back(std::thread(findmean, &data, A, B, &(result[0]))); thread.push_back(std::thread(findmean, &data, C, D , &(result[1]))); // Join threads thread[0].join(); thread[1].join(); // Calculate result mean = result[0] + result[1]; mean /= (double)data.size(); // Print result std::cout << " Mean=" << mean << std::endl; // Return return EXIT_SUCCESS; } void findmean(std::vector<double>* datavec, std::size_t start, std::size_t length, double* result) { for(uint32_t i = 0; i < length; i ++) { *result += (*datavec).at(start + i); } } I don't think this code is exactly wonderful, if you could suggest ways of improving it then I would be grateful for that also.

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• Custom Online Backup Solution Advice

  - by Martín Marconcini

  I have to implement a way so our customers can backup their SQL 2000/5/8 databasase online. The application they use is a C#/.NET35 Winforms application that connects to a SQL Server (can be 2000/2005/2008, sometimes express editions). The SQL Server is on the same LAN. Our application has a very specific UI and we must code each form following those guidelines. There’s lots of GDI+ to give it the look and feel we want. For that reason, using a 3rd party application is not a very good idea. We need to charge the customer on a monthly/annual basis for the service. Preferably, the customer doesn’t need to care about bandwidth and storage space. It must be transparent. Given the above reqs., my first thoughts are: Solution 1: Code some sort of FTP basic functionality with behind the scenes SQL Backup mechanism, then hire a Hosting service and compress-transfer the .BAK to the Hosting. Maintain a series of Folders (for each customer). They won’t see what’s happening. They will just see a list of their files and a big “Backup now” button that will perform the SQL backup, compress it and upload it (and update the file list) ;) Pros: Not very complicated to implement, simple to use, fairly simple to configure (could have a dedicated ftp user/pass) Cons: Finding a “ftp” only hosting plan is not probably going to be easy, they usually come with a bunch of stuff. FTP is not always the best protocol. more? Solution 2: Similar to 1, but instead of FTP, find a cloud computing service like Amazon S3, Mosso or similar. Pros: Cloud Storage is fast, reliable, etc. It’s kind of easy to implement (specially if there are APIs like AWS or Mosso). Cons: I have been unable to come up with a service optimized for resellers where I can give multiple sub-accounts (one for each customer). Billing is going to be a nightmare cuz these services bill per/GB and with One account it’s impossible to differentiate each customer. Solution 3: Similar to 2, but letting the user create their own account on Amazon S3 (for example). Pros: You forget about billing and such. Cons: A mess for the customer who has to open the Amazon (or whatever) account, will be charged for that and not from you. You can’t really charge the customer (since you’re just not doing anything). Solution 4: Use one of the many backup online solutions that use the tech in cloud storage. Pros: many of these include SQL Server backup, and a lot of features that we’d have to implement. Plus web access and stuff like that will come included. Cons: Still have the billing problem described in number 2. Little of these companies (if any) offers “reseller” accounts. You have to eventually use their software (some offer certain branding). Any better approach? Summary: You have a software (.NET Winapp). You want your users to be able to backup their SQL Server databases online (and be able to retrieve the backups if needed). You ideally would like to charge the customer for this service (i.e. XX € a year).

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• Algorithm to select groups of similar items in 2d array

  - by mafutrct

  There is a 2d array of items (in my case they are called Intersections). A certain item is given as a start. The task is to find all items directly or indirectly connected to this item that satisfy a certain function. So the basic algorithm is like this: Add the start to the result list. Repeat until no modification: Add each item in the array that satisfies the function and touches any item in the result list to the result list. My current implementation looks like this: private IList<Intersection> SelectGroup ( Intersection start, Func<Intersection, Intersection, bool> select) { List<Intersection> result = new List<Intersection> (); Queue<Intersection> source = new Queue<Intersection> (); source.Enqueue (start); while (source.Any ()) { var s = source.Dequeue (); result.Add (s); foreach (var neighbour in Neighbours (s)) { if (select (start, neighbour) && !result.Contains (neighbour) && !source.Contains (neighbour)) { source.Enqueue (neighbour); } } } Debug.Assert (result.Distinct ().Count () == result.Count ()); Debug.Assert (result.All (x => select (x, result.First ()))); return result; } private List<Intersection> Neighbours (IIntersection intersection) { int x = intersection.X; int y = intersection.Y; List<Intersection> list = new List<Intersection> (); if (x > 1) { list.Add (GetIntersection (x - 1, y)); } if (y > 1) { list.Add (GetIntersection (x, y - 1)); } if (x < Size) { list.Add (GetIntersection (x + 1, y)); } if (y < Size) { list.Add (GetIntersection (x, y + 1)); } return list; } (The select function takes a start item and returns true iff the second item satisfies.) This does its job and turned out to be reasonable fast for the usual array sizes (about 20*20). However, I'm interested in further improvements. Any ideas? Example (X satisfies in relation to other Xs, . does never satisfy): .... XX.. .XX. X... In this case, there are 2 groups: a central group of 4 items and a group of a single item in the lower left. Selecting the group (for instance by starting item [2, 2]) returns the former, while the latter can be selected using the starting item and sole return value [0, 3]. Example 2: .A.. ..BB A.AA This time there are 4 groups. The 3 A groups are not connected, so they are returned as separate groups. The bigger A and B groups are connected, but A does not related to B so they are returned as separate groups.

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• weighted RNG speed problem in C++

  - by supert

  I have a (fast) bit of C++ code that samples cards from a 52 card deck: void sample_allcards(int table[5], int holes[], int players) { int temp[5 + 2 * players]; bool try_again; int c, n, i; for (i = 0; i < 5 + 2 * players; i++) { try_again = true; while (try_again == true) { try_again = false; c = fast_rand52(); // reject collisions for (n = 0; n < i + 1; n++) { try_again = (temp[n] == c) || try_again; } temp[i] = c; } } copy_cards(table, temp, 5); copy_cards(holes, temp + 5, 2 * players); } I am implementing code to sample the hole cards according to a known distribution (stored as a 2d table). My code for this looks like: void sample_allcards_weighted(double weights[][HOLE_CARDS], int table[5], int holes[], int players) { // weights are distribution over hole cards int temp[5 + 2 * players]; int n, i; // table cards for (i = 0; i < 5; i++) { bool try_again = true; while (try_again == true) { try_again = false; int c = fast_rand52(); // reject collisions for (n = 0; n < i + 1; n++) { try_again = (temp[n] == c) || try_again; } temp[i] = c; } } for (int player = 0; player < players; player++) { // hole cards according to distribution i = 5 + 2 * player; bool try_again = true; while (try_again == true) { try_again = false; // weighted-sample c1 and c2 at once double w[1326]; memcpy(w, weights[player], sizeof(w)); // h is a number < 1325 int h = weighted_randi(w, HOLE_CARDS); // i2h uses h and sets temp[i] to the 2 cards implied by h i2h(&temp[i], h); // reject collisions for (n = 0; n < i; n++) { try_again = (temp[n] == temp[i]) || (temp[n] == temp[i+1]) || try_again; } } } copy_cards(table, temp, 5); copy_cards(holes, temp + 5, 2 * players); } My problem? The weighted sampling algorithm is a factor of 10 slower. Speed is very important for my application. Is there a way to improve the speed of my algorithm to something more reasonable? Am I doing something wrong in my implementation? Thanks.

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• Make interchangeable class types via pointer casting only, without having to allocate any new objects?

  - by HostileFork

  UPDATE: I do appreciate "don't want that, want this instead" suggestions. They are useful, especially when provided in context of the motivating scenario. Still...regardless of goodness/badness, I've become curious to find a hard-and-fast "yes that can be done legally in C++11" vs "no it is not possible to do something like that". I want to "alias" an object pointer as another type, for the sole purpose of adding some helper methods. The alias cannot add data members to the underlying class (in fact, the more I can prevent that from happening the better!) All aliases are equally applicable to any object of this type...it's just helpful if the type system can hint which alias is likely the most appropriate. There should be no information about any specific alias that is ever encoded in the underlying object. Hence, I feel like you should be able to "cheat" the type system and just let it be an annotation...checked at compile time, but ultimately irrelevant to the runtime casting. Something along these lines: Node<AccessorFoo>* fooPtr = Node<AccessorFoo>::createViaFactory(); Node<AccessorBar>* barPtr = reinterpret_cast< Node<AccessorBar>* >(fooPtr); Under the hood, the factory method is actually making a NodeBase class, and then using a similar reinterpret_cast to return it as a Node<AccessorFoo>*. The easy way to avoid this is to make these lightweight classes that wrap nodes and are passed around by value. Thus you don't need casting, just Accessor classes that take the node handle to wrap in their constructor: AccessorFoo foo (NodeBase::createViaFactory()); AccessorBar bar (foo.getNode()); But if I don't have to pay for all that, I don't want to. That would involve--for instance--making a special accessor type for each sort of wrapped pointer (AccessorFooShared, AccessorFooUnique, AccessorFooWeak, etc.) Having these typed pointers being aliased for one single pointer-based object identity is preferable, and provides a nice orthogonality. So back to that original question: Node<AccessorFoo>* fooPtr = Node<AccessorFoo>::createViaFactory(); Node<AccessorBar>* barPtr = reinterpret_cast< Node<AccessorBar>* >(fooPtr); Seems like there would be some way to do this that might be ugly but not "break the rules". According to ISO14882:2011(e) 5.2.10-7: An object pointer can be explicitly converted to an object pointer of a different type.70 When a prvalue v of type "pointer to T1" is converted to the type "pointer to cv T2", the result is static_cast(static_cast(v)) if both T1 and T2 are standard-layout types (3.9) and the alignment requirements of T2 are no stricter than those of T1, or if either type is void. Converting a prvalue of type "pointer to T1" to the type "pointer to T2" (where T1 and T2 are object types and where the alignment requirements of T2 are no stricter than those of T1) and back to its original type yields the original pointer value. The result of any other such pointer conversion is unspecified. Drilling into the definition of a "standard-layout class", we find: has no non-static data members of type non-standard-layout-class (or array of such types) or reference, and has no virtual functions (10.3) and no virtual base classes (10.1), and has the same access control (clause 11) for all non-static data members, and has no non-standard-layout base classes, and either has no non-static data member in the most-derived class and at most one base class with non-static data members, or has no base classes with non-static data members, and has no base classes of the same type as the first non-static data member. Sounds like working with something like this would tie my hands a bit with no virtual methods in the accessors or the node. Yet C++11 apparently has std::is_standard_layout to keep things checked. Can this be done safely? Appears to work in gcc-4.7, but I'd like to be sure I'm not invoking undefined behavior.

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• NullReferenceException makes me want to shoot myself

  - by rockinthesixstring

  Ok, so once upon a time, my code worked. Since then I did some refactoring (basic stuff so I thought) but now I'm getting a null reference exception, and I can't bloody well figure out why. Here's where it starts. note, this is the logout method, but all of my ActivityLogs sections are throwing this error Function LogOut(ByVal go As String) As ActionResult ActivityLogService.AddActivity(AuthenticationHelper.RetrieveAuthUser.ID, _ IActivityLogService.LogType.UserLogout, _ HttpContext.Request.UserHostAddress) ActivityLogService.SubmitChanges() ''# more stuff happens after this End Function The service is pretty straight forward (notice the ERROR THROWN HERE) Public Sub AddActivity(ByVal userid As Integer, ByVal activity As Integer, ByVal ip As String) Implements IActivityLogService.AddActivity Dim _activity As ActivityLog = New ActivityLog With {.Activity = activity, .UserID = userid, .UserIP = ip.IPAddressToNumber, .ActivityDate = DateTime.UtcNow} ActivityLogRepository.Create(_activity) ''#ERROR THROWN HERE End Sub And the Interface that the Service uses looks like this Public Interface IActivityLogService Sub AddActivity(ByVal userid As Integer, ByVal activity As Integer, ByVal ip As String) Function GetUsersLastActivity(ByVal UserID As Integer) As ActivityLog Sub SubmitChanges() ''' <summary> ''' The type of activity done by the user ''' </summary> ''' <remarks>Each int refers to an activity. ''' There can be no duplicates or modifications ''' after this application goes live</remarks> Enum LogType As Integer ''' <summary> ''' A new session started ''' </summary> SessionStarted = 1 ''' <summary> ''' A new user is Added/Created ''' </summary> UserAdded = 2 ''' <summary> ''' User has updated their profile ''' </summary> UserUpdated = 3 ''' <summary> ''' User has logged into they system ''' </summary> UserLogin = 4 ''' <summary> ''' User has logged out of the system ''' </summary> UserLogout = 5 ''' <summary> ''' A new event has been added ''' </summary> EventAdded = 6 ''' <summary> ''' An event has been updated ''' </summary> EventUpdated = 7 ''' <summary> ''' An event has been deleted ''' </summary> EventDeleted = 8 ''' <summary> ''' An event has received a Up/Down vote ''' </summary> EventVoted = 9 ''' <summary> ''' An event has been closed ''' </summary> EventCloseVoted = 10 ''' <summary> ''' A comment has been added to an event ''' </summary> CommentAdded = 11 ''' <summary> ''' A comment has been updated ''' </summary> CommentUpdated = 12 ''' <summary> ''' A comment has been deleted ''' </summary> CommentDeleted = 13 ''' <summary> ''' An event or comment has been reported as spam ''' </summary> SpamReported = 14 End Enum End Interface And the repository is equally straight forward Public Sub Create(ByVal activity As ActivityLog) Implements IActivityLogRepository.Create dc.ActivityLogs.InsertOnSubmit(activity) End Sub The stack trace is as follows [NullReferenceException: Object reference not set to an instance of an object.] MyApp.Core.Domain.ActivityLogService.AddActivity(Int32 userid, Int32 activity, String ip) in E:\Projects\MyApp\MyApp.Core\Domain\Services\ActivityLogService.vb:49 MyApp.Core.Controllers.UsersController.Authenticate(String go) in E:\Projects\MyApp\MyApp.Core\Controllers\UsersController.vb:258 lambda_method(Closure , ControllerBase , Object[] ) +163 System.Web.Mvc.ActionMethodDispatcher.Execute(ControllerBase controller, Object[] parameters) +51 System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary2 parameters) +409 System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary2 parameters) +52 System.Web.Mvc.<c_DisplayClass15.b_12() +127 System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter(IActionFilter filter, ActionExecutingContext preContext, Func1 continuation) +436 System.Web.Mvc.<>c__DisplayClass17.<InvokeActionMethodWithFilters>b__14() +61 System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodWithFilters(ControllerContext controllerContext, IList1 filters, ActionDescriptor actionDescriptor, IDictionary2 parameters) +305 System.Web.Mvc.ControllerActionInvoker.InvokeAction(ControllerContext controllerContext, String actionName) +830 System.Web.Mvc.Controller.ExecuteCore() +136 System.Web.Mvc.ControllerBase.Execute(RequestContext requestContext) +232 System.Web.Mvc.ControllerBase.System.Web.Mvc.IController.Execute(RequestContext requestContext) +39 System.Web.Mvc.<>c__DisplayClassb.<BeginProcessRequest>b__5() +68 System.Web.Mvc.Async.<>c__DisplayClass1.<MakeVoidDelegate>b__0() +44 System.Web.Mvc.Async.<>c__DisplayClass81.b__7(IAsyncResult ) +42 System.Web.Mvc.Async.WrappedAsyncResult`1.End() +141 System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +54 System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +40 System.Web.Mvc.<c_DisplayClasse.b_d() +61 System.Web.Mvc.SecurityUtil.b_0(Action f) +31 System.Web.Mvc.SecurityUtil.ProcessInApplicationTrust(Action action) +56 System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult) +110 System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.EndProcessRequest(IAsyncResult result) +38 System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +690 System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +194 here's an image of the error when attached to the debugger. And here's an image of the DB schema in question Can anyone shed some light on what I might be missing here?

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• Rails - session information being cleared?

  - by Jty.tan

  Hi! I'm having a weird issue that I can't track down... For context, I have resources of Users, Registries, and Giftlines. Each User has many Registries. Each Registry has many Giftlines. It's a belongs to association for them in a reverse manner. What is basically happening, is that when I am creating a giftline, the giftline itself is created properly, and linked to its associated Registry properly, but then in the process of being redirected back to the Registry show page, the session[:user_id] variable is cleared and I'm logged out. As far as I can tell, where it goes wrong is here in the registries_controller: def show @registry = Registry.find(params[:id]) @user = User.find(@registry.user_id) if (params[:user_id] && (@user.login != params[:user_id]) ) flash[:notice] = "User #{params[:user_id]} does not have such a registry." redirect_to user_registries_path(session[:user_id]) end end Now, to be clear, I can do a show of the registry normally, and nothing weird happens. It's only when I've added a giftline does the session[:user_id] variable get cleared. I used the debugger and this is what seems to be happening. (rdb:19) list [20, 29] in /Users/kriston/Dropbox/ruby_apps/bee_registered/app/controllers/registries_controller.rb 20 render :action => 'new' 21 end 22 end 23 24 def show => 25 @registry = Registry.find(params[:id]) 26 @user = User.find(@registry.user_id) 27 if (params[:user_id] && (@user.login != params[:user_id]) ) 28 flash[:notice] = "User #{params[:user_id]} does not have such a registry." 29 redirect_to user_registries_path(session[:user_id]) (rdb:19) session[:user_id] "tester" (rdb:19) So from there we can see that the code has gotten back to the show command after the item had been added, and that the session[:user_id] variable is still set. (rdb:19) list [22, 31] in /Users/kriston/Dropbox/ruby_apps/bee_registered/app/controllers/registries_controller.rb 22 end 23 24 def show 25 @registry = Registry.find(params[:id]) 26 @user = User.find(@registry.user_id) => 27 if (params[:user_id] && (@user.login != params[:user_id]) ) 28 flash[:notice] = "User #{params[:user_id]} does not have such a registry." 29 redirect_to user_registries_path(session[:user_id]) 30 end 31 end (rdb:19) session[:user_id] "tester" (rdb:19) Stepping on, we get to this point. And the session[:user_id] is still set. At this point, the URL is of the format localhost:3000/registries/:id, so params[:user_id] fails, and the if condition doesn't occur. (Unless I am completely wrong .<) So then the next bit occurs, which is (rdb:19) list [1327, 1336] in /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/base.rb 1327 end 1328 1329 def perform_action 1330 if action_methods.include?(action_name) 1331 send(action_name) => 1332 default_render unless performed? 1333 elsif respond_to? :method_missing 1334 method_missing action_name 1335 default_render unless performed? 1336 else (rdb:19) session[:user_id] "tester" And then when I hit next... (rdb:19) next 2: session[:user_id] = /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/filters.rb:618 return index if nesting != 0 || aborted (rdb:19) list [613, 622] in /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/filters.rb 613 private 614 def call_filters(chain, index, nesting) 615 index = run_before_filters(chain, index, nesting) 616 aborted = @before_filter_chain_aborted 617 perform_action_without_filters unless performed? || aborted => 618 return index if nesting != 0 || aborted 619 run_after_filters(chain, index) 620 end 621 622 def run_before_filters(chain, index, nesting) (rdb:19) session {:user_id=>nil, :session_id=>"49992cdf2ddc708b441807f998af7ddc", :return_to=>"/registries", "flash"=>{}, :_csrf_token=>"xMDI0oDaOgbzhQhDG7EqOlGlxwIhHlB6c71fWgOIKcs="} The session[:user_id] is cleared, and when the page renders, I'm logged out. .< Sooo.... Any idea why this is occurring? It just occurred to me that I'm not sure if I'm meant to be pasting large chunks of debug output in here... Somebody point out to me if I'm not meant to be doing this. . And yes, this only occurs when I have added a giftitem, and it is sending me back to the registry page. When I'm viewing it, the same code occurs, but the session[:user_id] variable isn't cleared. It's driving me mildly insane. Thanks!

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• Reading data from database and binding them to custom ListView

  - by N.K.

  I try to read data from a database i have made and to show some of the data in a row at a custom ListView. I can not understand what is my mistake. This is my code: public class EsodaMainActivity extends Activity { public static final String ROW_ID = "row_id"; //Intent extra key private ListView esodaListView; // the ListActivitys ListView private SimpleCursorAdapter esodaAdapter; // adapter for ListView DatabaseConnector databaseConnector = new DatabaseConnector(EsodaMainActivity.this); // called when the activity is first created @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_esoda_main); esodaListView = (ListView)findViewById(R.id.esodaList); esodaListView.setOnItemClickListener(viewEsodaListener); databaseConnector.open(); //Cursor cursor= databaseConnector.query("esoda", new String[] // {"name", "amount"}, null,null,null); Cursor cursor=databaseConnector.getAllEsoda(); startManagingCursor(cursor); // map each esoda to a TextView in the ListView layout // The desired columns to be bound String[] from = new String[] {"name","amount"}; // built an String array named "from" //The XML defined views which the data will be bound to int[] to = new int[] { R.id.esodaTextView, R.id.amountTextView}; // built an int array named "to" // EsodaMainActivity.this = The context in which the ListView is running // R.layout.esoda_list_item = Id of the layout that is used to display each item in ListView // null = // from = String array containing the column names to display // to = Int array containing the column names to display esodaAdapter = new SimpleCursorAdapter (this, R.layout.esoda_list_item, cursor, from, to); esodaListView.setAdapter(esodaAdapter); // set esodaView's adapter } // end of onCreate method @Override protected void onResume() { super.onResume(); // call super's onResume method // create new GetEsodaTask and execute it // GetEsodaTask is an AsyncTask object new GetEsodaTask().execute((Object[]) null); } // end of onResume method // onStop method is executed when the Activity is no longer visible to the user @Override protected void onStop() { Cursor cursor= esodaAdapter.getCursor(); // gets current cursor from esodaAdapter if (cursor != null) cursor.deactivate(); // deactivate cursor esodaAdapter.changeCursor(null); // adapter now has no cursor (removes the cursor from the CursorAdapter) super.onStop(); } // end of onStop method // this class performs db query outside the GUI private class GetEsodaTask extends AsyncTask<Object, Object, Cursor> { // we create a new DatabaseConnector obj // EsodaMainActivity.this = Context DatabaseConnector databaseConnector = new DatabaseConnector(EsodaMainActivity.this); // perform the db access @Override protected Cursor doInBackground(Object... params) { databaseConnector.open(); // get a cursor containing call esoda return databaseConnector.getAllEsoda(); // the cursor returned by getAllContacts() is passed to method onPostExecute() } // end of doInBackground method // here we use the cursor returned from the doInBackground() method @Override protected void onPostExecute(Cursor result) { esodaAdapter.changeCursor(result); // set the adapter's Cursor databaseConnector.close(); } // end of onPostExecute() method } // end of GetEsodaTask class // creates the Activity's menu from a menu resource XML file @Override public boolean onCreateOptionsMenu(Menu menu) { super.onCreateOptionsMenu(menu); MenuInflater inflater = getMenuInflater(); inflater.inflate(R.menu.esoda_menu, menu); // inflates(eµf?s?) esodamainactivity_menu.xml to the Options menu return true; } // end of onCreateOptionsMenu() method //handles choice from options menu - is executed when the user touches a MenuItem @Override public boolean onOptionsItemSelected(MenuItem item) { // creates a new Intent to launch the AddEditEsoda Activity // EsodaMainActivity.this = Context from which the Activity will be launched // AddEditEsoda.class = target Activity Intent addNewEsoda = new Intent(EsodaMainActivity.this, AddEditEsoda.class); startActivity(addNewEsoda); return super.onOptionsItemSelected(item); } // end of method onPtionsItemSelected() // event listener that responds to the user touching a esoda's name in the ListView OnItemClickListener viewEsodaListener = new OnItemClickListener() { @Override public void onItemClick(AdapterView<?> arg0, View arg1, int arg2, long arg3) { // create an intent to launch the ViewEsoda Activity Intent viewEsoda = new Intent(EsodaMainActivity.this, ViewEsoda.class); // pass the selected esoda's row ID as an extra with the Intent viewEsoda.putExtra(ROW_ID, arg3); startActivity(viewEsoda); // start viewEsoda.class Activity } // end of onItemClick() method }; // end of viewEsodaListener } // end of EsodaMainActivity class The statement: Cursor cursor=databaseConnector.getAllEsoda(); queries all data (columns) From the data I want to show at my custom ListView 2 of them: "name" and "amount". But I still get a debugger error. Please help.

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• is Boost Library's weighted median broken?

  - by user624188

  I confess that I am no expert in C++. I am looking for a fast way to compute weighted median, which Boost seemed to have. But it seems I am not able to make it work. #include <iostream> #include <boost/accumulators/accumulators.hpp> #include <boost/accumulators/statistics/stats.hpp> #include <boost/accumulators/statistics/median.hpp> #include <boost/accumulators/statistics/weighted_median.hpp> using namespace boost::accumulators; int main() { // Define an accumulator set accumulator_set<double, stats<tag::median > > acc1; accumulator_set<double, stats<tag::median >, float> acc2; // push in some data ... acc1(0.1); acc1(0.2); acc1(0.3); acc1(0.4); acc1(0.5); acc1(0.6); acc2(0.1, weight=0.); acc2(0.2, weight=0.); acc2(0.3, weight=0.); acc2(0.4, weight=1.); acc2(0.5, weight=1.); acc2(0.6, weight=1.); // Display the results ... std::cout << " Median: " << median(acc1) << std::endl; std::cout << "Weighted Median: " << median(acc2) << std::endl; return 0; } produces the following output, which is clearly wrong. Median: 0.3 Weighted Median: 0.3 Am I doing something wrong? Any help will be greatly appreciated. * however, the weighted sum works correctly * @glowcoder: The weighted sum works perfectly fine like this. #include <iostream> #include <boost/accumulators/accumulators.hpp> #include <boost/accumulators/statistics/stats.hpp> #include <boost/accumulators/statistics/sum.hpp> #include <boost/accumulators/statistics/weighted_sum.hpp> using namespace boost::accumulators; int main() { // Define an accumulator set accumulator_set<double, stats<tag::sum > > acc1; accumulator_set<double, stats<tag::sum >, float> acc2; // accumulator_set<double, stats<tag::median >, float> acc2; // push in some data ... acc1(0.1); acc1(0.2); acc1(0.3); acc1(0.4); acc1(0.5); acc1(0.6); acc2(0.1, weight=0.); acc2(0.2, weight=0.); acc2(0.3, weight=0.); acc2(0.4, weight=1.); acc2(0.5, weight=1.); acc2(0.6, weight=1.); // Display the results ... std::cout << " Median: " << sum(acc1) << std::endl; std::cout << "Weighted Median: " << sum(acc2) << std::endl; return 0; } and the result is Sum: 2.1 Weighted Sum: 1.5

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• Do you know of a C macro to compute Unix time and date?

  - by Alexis Wilke

  I'm wondering if someone knows/has a C macro to compute a static Unix time from a hard coded date and time as in: time_t t = UNIX_TIMESTAMP(2012, 5, 10, 9, 26, 13); I'm looking into that because I want to have a numeric static timestamp. This will be done hundred of times throughout the software, each time with a different date, and I want to make sure it is fast because it will run hundreds of times every second. Converting dates that many times would definitively slow down things (i.e. calling mktime() is slower than having a static number compiled in place, right?) [made an update to try to render this paragraph clearer, Nov 23, 2012] Update I want to clarify the question with more information about the process being used. As my server receives requests, for each request, it starts a new process. That process is constantly updated with new plugins and quite often such updates require a database update. Those must be run only once. To know whether an update is necessary, I want to use a Unix date (which is better than using a counter because a counter is much more likely to break once in a while.) The plugins will thus receive an update signal and have their on_update() function called. There I want to do something like this: void some_plugin::on_update(time_t last_update) { if(last_update < UNIX_TIMESTAMP(2010, 3, 22, 20, 9, 26)) { ...run update... } if(last_update < UNIX_TIMESTAMP(2012, 5, 10, 9, 26, 13)) { ...run update... } // as many test as required... } As you can see, if I have to compute the unix timestamp each time, this could represent thousands of calls per process and if you receive 100 hits a second x 1000 calls, you wasted 100,000 calls when you could have had the compiler compute those numbers once at compile time. Putting the value in a static variable is of no interest because this code will run once per process run. Note that the last_update variable changes depending on the website being hit (it comes from the database.) Code Okay, I got the code now: // helper (Days in February) #define _SNAP_UNIX_TIMESTAMP_FDAY(year) \ (((year) % 400) == 0 ? 29LL : \ (((year) % 100) == 0 ? 28LL : \ (((year) % 4) == 0 ? 29LL : \ 28LL))) // helper (Days in the year) #define _SNAP_UNIX_TIMESTAMP_YDAY(year, month, day) \ ( \ /* January */ static_cast<qint64>(day) \ /* February */ + ((month) >= 2 ? 31LL : 0LL) \ /* March */ + ((month) >= 3 ? _SNAP_UNIX_TIMESTAMP_FDAY(year) : 0LL) \ /* April */ + ((month) >= 4 ? 31LL : 0LL) \ /* May */ + ((month) >= 5 ? 30LL : 0LL) \ /* June */ + ((month) >= 6 ? 31LL : 0LL) \ /* July */ + ((month) >= 7 ? 30LL : 0LL) \ /* August */ + ((month) >= 8 ? 31LL : 0LL) \ /* September */+ ((month) >= 9 ? 31LL : 0LL) \ /* October */ + ((month) >= 10 ? 30LL : 0LL) \ /* November */ + ((month) >= 11 ? 31LL : 0LL) \ /* December */ + ((month) >= 12 ? 30LL : 0LL) \ ) #define SNAP_UNIX_TIMESTAMP(year, month, day, hour, minute, second) \ ( /* time */ static_cast<qint64>(second) \ + static_cast<qint64>(minute) * 60LL \ + static_cast<qint64>(hour) * 3600LL \ + /* year day (month + day) */ (_SNAP_UNIX_TIMESTAMP_YDAY(year, month, day) - 1) * 86400LL \ + /* year */ (static_cast<qint64>(year) - 1970LL) * 31536000LL \ + ((static_cast<qint64>(year) - 1969LL) / 4LL) * 86400LL \ - ((static_cast<qint64>(year) - 1901LL) / 100LL) * 86400LL \ + ((static_cast<qint64>(year) - 1601LL) / 400LL) * 86400LL ) WARNING: Do not use these macros to dynamically compute a date. It is SLOWER than mktime(). This being said, if you have a hard coded date, then the compiler will compute the time_t value at compile time. Slower to compile, but faster to execute over and over again.

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• Javascript: selfmade methods not working correctly

  - by hdr

  Hi everyone, I tried to figure this out for some days now, I tried to use my own object to sort of replace the global object to reduce problems with other scripts (userscripts, chrome extensions... that kind of stuff). However I can't get things to work for some reason. I tried some debugging with JSLint, the developer tools included in Google Chrome, Firebug and the integrated schript debugger in IE8 but there is no error that explains why it doesn't work at all in any browser I tried. I tried IE 8, Google Chrome 10.0.612.3 dev, Firefox 3.6.13, Safari 5.0.3 and Opera 11. So... here is the code: HTML: <!DOCTYPE HTML> <html manifest="c.manifest"> <head> <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1"> <meta charset="utf-8"> <!--[if IE]> <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/chrome-frame/1/CFInstall.min.js"></script> <script src="https://ie7-js.googlecode.com/svn/version/2.1(beta4)/IE9.js">IE7_PNG_SUFFIX=".png";</script> <![endif]--> <!--[if lt IE 9]> <script src="js/lib/excanvas.js"></script> <script src="https://html5shiv.googlecode.com/svn/trunk/html5.js"></script> <![endif]--> <script src="js/data.js"></script> </head> <body> <div id="controls"> <button onclick="MYOBJECTis.next()">Next</button> </div> <div id="textfield"></div> <canvas id="game"></canvas> </body> </html> Javascript: var that = window, it = document, k = Math.floor; var MYOBJECTis = { aresizer: function(){ // This method looks like it doesn't work. // It should automatically resize all the div elements and the body. // JSLint: no error (execpt for "'window' is not defined." which is normal since // JSLint does nor recognize references to the global object like "window" or "self" // even if you assume a browser) // Firebug: no error // Chrome dev tools: no error // IE8: that.documentElement.clientWidth is null or not an object "use strict"; var a = that.innerWidth || that.documentElement.clientWidth, d = that.innerHeight || that.documentElement.clientHeight; (function() { for(var b = 0, c = it.getElementsByTagName("div");b < c.length;b++) { c.style.width = k(c.offsetWidth) / 100 * k(a); c.style.height = k(c.offsetHight) / 100 * k(d); } }()); (function() { var b = it.getElementsByTagName("body"); b.width = a; b.height = d; }()); }, next: function(){ // This method looks like it doesn't work. // It should change the text inside a div element // JSLint: no error (execpt for "'window' is not defined.") // Firebug: no error // Chrome dev tools: no error // IE8: no error (execpt for being painfully slow) "use strict"; var b = it.getElementById("textfield"), a = [], c; switch(c !== typeof Number){ case true: a[1] = ["HI"]; c = 0; break; case false: return Error; default: b.innerHtml = a[c]; c+=1; } } }; // auto events (function(){ "use strict"; that.onresize = MYOBJECTis.aresizer(); }()); If anyone can help me out with this I would very much appreciate it. EDIT: To answer the question what's not working I can just say that no method I showed here is working at all and I don't know the cause of the problem. I also tried to clean up some of the code that has most likely nothing to do with it. Additional information is in the comments inside the code.

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• jquery mouse events masked by img in IE8 - all other platforms/browsers work fine

  - by Bruce

  Using the jQuery mouse events for mouseenter, mouseleave or hover all work swimmingly on all Mac or Windows browsers except for IE8/Windows. I am using mouseenter and mouseleave to test for hot rectangles (absolutely positioned and dimensioned divs that have no content) over an image used as hotspots to make visible the navigation buttons when different regions of the main enclosing rectangle (image) are touched by the cursor. Windows/IE jQuery never sends notifications (mouseenter our mouseleave) as the cursor enters or exits one of the target divs. If I turn off the visibility of the image everything works as expected (like it does in every other browser), so the image is effectively blocking all messages (the intention was for the image to be a background and all the divs float above it, where they can be clicked on). I understand that there's a z-index gotcha (so explicitly specifying z-index for each absolute positioned div does not work), but unclear as to how to nest or order multiple divs to allow a single set of jQuery rules to support all browsers. The image tag seems to trump all other divs and always appear in front of them... BTW: I could not use i m g as a tag in this text so it is spelled image in the following, so the input editor does not think that I am trying to pull a fast one on stackoverflow... How used? "mainview" is the background image, "zoneleft" and "zoneright" are the active areas where when the cursor enters the nav buttons "leftarrow" and rightarrow" are supposed to appear. Javascript $("div#zoneleft").bind("mouseenter",function () // enters left zone see left arrow { arrowVisibility("left"); document.getElementById("leftarrow").style.display="block"; }).bind("mouseleave",function () { document.getElementById("leftarrow").style.visibility="hidden"; document.getElementById("rightarrow").style.visibility="hidden"; }); HTML <div id="zoneleft" style="position:absolute; top:44px; left:0px; width:355px; height:372px; z-index:40;"> <div id="leftarrow" style="position:absolute; top:158px; left:0px; z-index:50;"><img src="images/newleft.png" width="59" height="56"/></div></div> <div id="zoneright" style="position:absolute; top:44px; left:355px; width:355px; height:372px; z-index:40;"> <div id="rightarrow" style="position:absolute; top:158px; left:296px; z-index:50;"> (tag named changed so that I could include it here) <image src="images/newright.png" width="59" height="56" /></div></div> </div><!-- navbuttons --> <image id="mainview" style="z-index:-1;" src="images/projectPhotos/photo1.jpg" width:710px; height:372px; /> (tag named changed so that I could include it here) </div><!--photo-->

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• Faulty to use memcache together with a php web-browser-game in this way?

  - by Crowye

  Background We are currently working on a strategy web-browser game based on php, html and javascript. The plan is to have 10,000+ users playing within the same world. Currently we are using memcached to: store json static data, language files store changeable serialized php class objects (such as armies, inventorys, unit-containers, buildings, etc) In the back we have a mysql server running and holding all the game data aswell. When a object is loaded through our ObjectLoader it loads in this order: checks a static hashmap in the script for the object checks memcache if it has already been loaded into it otherwise loads from database, and saves it into memcache and the static temp hashmap We have built the whole game using a class-object-oriented approach where functionality is always made between objects. Beause of this we think we have managed to get a nice structure, and with the help of memcached we have received good request times from client-server when interacting with the game. I'm aware that memcache is not synchronized, and also is not commonly used for holding a full game in memory. In the beginning after a server's startup the load times when loading objects into memcache for the first time will be high, but after the server's been online for a while and most loads are from memcache, the loads will be well reduced. Currently we are saving changed objects into memcache and database at the same time. Earlier we had an idea to save objects into db only after a certain time or at intervals, but due to risk inconsistency if the memcache/server went down, we skipped it for now. Client requests to server often return object's status simple json-format without changing the object, which in turn is represented in the browser visually with images and javascript. But from time to time depending on when an object was last updated, it updates them with new information (e.g. a build-queue holding planned buildings time-progress is increased, and/or planned-queue-items-array has changed). Questions: Do you see how this could work or are we walking in blindness here? Do you expect us to have a lot of inconsistency issues if someone loads and updates the a memcache objects while someone else does the same? Is it even doable to do it in the way he have done it? Seems to be working fine atm, but so far we have only been 4 people online at the same time.. Is some other cache program more fit for this class-object approach than memcached? Is there any other tips you have for this situation? UPDATE Since it is simply a "normal webpage" (no applet, flash, etc), we are implementing the game so that the server is the only one holding a "real game-state".. the state of the different javascript-objects on the client is more like a approximative version of the server's game state. From time to time and before you do certain things important things, the client's visual state is updated to the server's state (e.g. the client things he can afford a barracks, asks the server to build a barracks, server updates current resources according to income-data on server and then tries to build a barracks or casts an error-message, and then sends the current server-state on resources, buildings back to the client).. It is not a fast-paced game lika real strategy game. More like a quite slow 3-4 months playtime game, where buildings can take +1 minute up to several days to complete.

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• Help with understanding why UAC dialog pops up on Win7 for our application

  - by Tim

  We have a C++ unmanaged application that appears to cause a UAC prompt. It seems to happen on Win7 and NOT on Vista Unfortunately the UAC dlg is system modal so I can't attach a debugger to check in the code where it is, and running under msdev (we're using 2008) runs in elevated mode. We put a message box at the start of our program/winmain but it doesn't even get that far, so apparently this is in the startup code. What can cause a UAC notification so early and what other things can I do to track down the cause? EDIT Apparently the manifest is an important issue here, but it seems not to be helping me - or perhaps I am not configuring the manifest file correctly. Can someone provide a sample manifest? Also, does the linker/UAC magic figure out that the program "might" write to the registry and set its UAC requirements based on that? There are code paths that might trigger UAC, but we are not even at that point when the UAC dlg comes up. An additional oddity is that this does not seem to happen on Vista with UAC turned on. Here is a manifest (that I think is/was generated automatically): <?xml version='1.0' encoding='UTF-8' standalone='yes'?> <assembly xmlns='urn:schemas-microsoft-com:asm.v1' manifestVersion='1.0'> <trustInfo xmlns="urn:schemas-microsoft-com:asm.v3"> <security> <requestedPrivileges> <requestedExecutionLevel level='asInvoker' uiAccess='false' /> </requestedPrivileges> </security> </trustInfo> <dependency> <dependentAssembly> <assemblyIdentity type='win32' name='Microsoft.Windows.Common-Controls' version='6.0.0.0' processorArchitecture='*' publicKeyToken='6595b64144ccf1df' language='*' /> </dependentAssembly> </dependency> <dependency> <dependentAssembly> <assemblyIdentity type='win32' name='Microsoft.Windows.Common-Controls' version='6.0.0.0' processorArchitecture='x86' publicKeyToken='6595b64144ccf1df' language='*' /> </dependentAssembly> </dependency> </assembly> And then this one was added to the manifest list to see if it would help <?xml version="1.0" encoding="UTF-8" standalone="yes"?> <assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestVersion="1.0"> <assemblyIdentity version="1.0.0.0" processorArchitecture="x86" name="[removed for anonymity]" type="win32" /> <description> [removed for anonymity] </description> <dependency> <dependentAssembly> <assemblyIdentity type="win32" name="Microsoft.Windows.Common-Controls" version="6.0.0.0" processorArchitecture="x86" publicKeyToken="6595b64144ccf1df" language="*" /> </dependentAssembly> </dependency> <trustInfo xmlns="urn:schemas-microsoft-com:asm.v2"> <security> <requestedPrivileges> <requestedExecutionLevel level="asInvoker" uiAccess="false"/> </requestedPrivileges> </security> </trustInfo> </assembly> The following is from the actual EXE using the ManifestViewer tool - <assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestVersion="1.0"> <assemblyIdentity version="1.0.0.0" processorArchitecture="x86" name="[removed]" type="win32" /> <description>[removed]</description> - <dependency> - <dependentAssembly> <assemblyIdentity type="win32" name="Microsoft.Windows.Common-Controls" version="6.0.0.0" processorArchitecture="x86" publicKeyToken="6595b64144ccf1df" language="*" /> </dependentAssembly> </dependency> - <dependency> - <dependentAssembly> <assemblyIdentity type="win32" name="Microsoft.Windows.Common-Controls" version="6.0.0.0" processorArchitecture="*" publicKeyToken="6595b64144ccf1df" language="*" /> </dependentAssembly> </dependency> - <trustInfo xmlns="urn:schemas-microsoft-com:asm.v2"> - <security> - <requestedPrivileges> <requestedExecutionLevel level="asInvoker" uiAccess="false" /> </requestedPrivileges> </security> </trustInfo> </assembly> It appears that it might be due to the xp compatibility setting on our app. I'll have to test that. (we set that in the installer I found out because some sound drivers don't work correctly on win7)

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• How to optimize this javascript code?

  - by Andrija

  I have a jsp which uses a lot of javascript and it's just not fast enough. I would like to optimize it so first, here's a part of the code: In the jsp I have the initialization: window.onload = function () { formCollection.pageSize.value = "<%= pagingSize%>"; elemCollection = iDom3.Table.all["spis"].XML.DOM; <% if (resultList != null) { %> elementsNumber = <%= resultList.size() %>; <%} else { %> elementsNumber = 0; <% } %> contextPath = "<%= request.getContextPath() %>"; } In my js file I have two types of js functions: // gets the first element and sets it's value to all the other; //the selectSingleNode function is used because I use XSLT transformation //to generate the table _setTehJed = function(){ var resultId = formCollection.elements["idTehJedinice_spis_1"].value; var resultText = formCollection.elements["tehnicka_spis_1"].value; if (resultId != ""){ var counter = 1; while (counter<elementsNumber){ counter++; if(formCollection.elements["idTehJedinice_spis_"+counter] != null){ formCollection.elements["idTehJedinice_spis_"+counter].value=resultId; formCollection.elements["tehnicka_spis_"+counter].value=resultText; } var node=elemCollection.selectSingleNode("/suite/table/rows/row[@id = 'spis_"+counter+"']/data[@col = 'tehnicka']/title"); node.text=resultText; var node2=elemCollection.selectSingleNode("/suite/table/rows/row[@id = 'spis_"+counter+"']/data[@col = 'idTehJedinice']/title"); node2.text=resultId; } } } // sets the elements checkbox to checked or unchecked _SelectCheckRokCuvanja = { all : [], Item : function (oItem, sId) { this.all["spis_"+sId] = oItem.value; if (oItem.checked) { elemCollection.selectSingleNode("/suite/table/rows/row[@id = 'spis_"+sId+"']/data[@col = 'rokCheck']").setAttribute("default", "true"); }else{ elemCollection.selectSingleNode("/suite/table/rows/row[@id = 'spis_"+sId+"']/data[@col = 'rokCheck']").setAttribute("default", "false"); } } } I've used these tips: http://blogs.msdn.com/b/ie/archive/2006/08/28/728654.aspx http://code.google.com/speed/articles/optimizing-javascript.html but I still think something could be done like defining the functions like this: In the jsp: window.onload = function () { iDom3.DigitalnaArhivaPrihvat.formCollection=document.forms["controller"]; iDom3.DigitalnaArhivaPrihvat.formCollection.pageSize.value = "<%= pagingSize%>"; iDom3.DigitalnaArhivaPrihvat.elemCollection = iDom3.Table.all["spis"].XML.DOM; <% if (resultList != null) { %> iDom3.DigitalnaArhivaPrihvat.elementsNumber = <%= resultList.size() %> <%} else { %> iDom3.DigitalnaArhivaPrihvat.elementsNumber = 0; <% } %> } in the js: iDom3.DigitalnaArhivaPrihvat = { formCollection:null, elemCollection:null, elementsNumber:null, _setTehJed : function(){ var resultId = this.formCollection.elements.idTehJedinice_spis_1.value; var resultText = this.formCollection.elements.tehnicka_spis_1.value; if (resultId != ""){ var counter = 1; while (counter<this.elementsNumber){ counter++; if(this.formCollection.elements["idTehJedinice_spis_"+counter] !== null){ this.formCollection.elements["idTehJedinice_spis_"+counter].value=resultId; this.formCollection.elements["tehnicka_spis_"+counter].value=resultText; } var node=this.elemCollection.selectSingleNode("/suite/table/rows/row[@id = 'spis_"+counter+"']/data[@col = 'tehnicka']/title"); node.text=resultText; var node2=this.elemCollection.selectSingleNode("/suite/table/rows/row[@id = 'spis_"+counter+"']/data[@col = 'idTehJedinice']/title"); node2.text=resultId; } } }, _SelectCheckRokCuvanja = { all : [], Item : function (oItem, sId) { this.all["spis_"+sId] = oItem.value; if (oItem.checked) { this.elemCollection.selectSingleNode("/suite/table/rows/row[@id = 'spis_"+sId+"']/data[@col = 'rokCheck']").setAttribute("default", "true"); }else{ this.elemCollection.selectSingleNode("/suite/table/rows/row[@id = 'spis_"+sId+"']/data[@col = 'rokCheck']").setAttribute("default", "false"); } } } but the problem is scoping (if I do it like this, the second function does not execute properly). Any suggestions?

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• May be my example site may answer my question about ajax call... Help me

  - by booota

  Okay I have this ajax call $('.updatecom .registercomplaint').click(function(){ updatecomplaints(); }); This calls the function updatecomplaints() function updatecomplaints() { var tno = $(".updatecom #tno").val(); var status = $(".updatecom #status").val(); if(status=='DONE') { $(".updatecom #con").val(''); } var tname = $(".updatecom #tname").val(); var rg11 = $(".updatecom #crg11").val(); var rg06 = $(".updatecom #crg06").val(); var tvpins = $(".updatecom #tvpins").val(); var jointer = $(".updatecom #jointer").val(); var cquantity = $(".updatecom #conqty").val(); var nooftv = $(".updatecom #tvno").val(); var misc = $(".updatecom #misc").val(); var tcomments = $(".updatecom #tcomments").val(); var con = $(".updatecom #con").val(); //alert(tno+status+tname+rg11+rg06+tvpins+jointer+cquantity+nooftv+misc+tcomments+con); $.ajax( { type: "POST", url: "up_functions.php", data: "ticket="+ tno +"& opt=upcom" +"& status="+ status +"& tname="+ tname +"& rg11="+ rg11 +"& rg06="+ rg06 +"& tvpins="+ tvpins +"& jointer="+ jointer +"& cquantity="+ cquantity +"& nooftv="+ nooftv +"& misc="+ misc +"& tcomments="+ tcomments +"& con="+ con, success: function(response) { alert(response); } }); } here is my up_functions.php $tno = htmlspecialchars(trim($_REQUEST['ticket'])); $status = htmlspecialchars(trim($_REQUEST['status'])); $tname = htmlspecialchars(trim($_REQUEST['tname'])); $rg11 = htmlspecialchars(trim($_REQUEST['rg11'])); $rg06 = htmlspecialchars(trim($_REQUEST['rg06'])); $tvpins = htmlspecialchars(trim($_REQUEST['tvpins'])); $jointer = htmlspecialchars(trim($_REQUEST['jointer'])); $cquantity = htmlspecialchars(trim($_REQUEST['cquantity'])); $nooftv = htmlspecialchars(trim($_REQUEST['nooftv'])); $misc = htmlspecialchars(trim($_REQUEST['misc'])); $tcomments = htmlspecialchars(trim($_REQUEST['tcomments'])); $con = htmlspecialchars(trim($_REQUEST['con'])); $result=$ptr-upcomticketinfo($tno,$status,$tname,$rg11,$rg06,$tvpins,$jointer,$cquantity,$nooftv,$misc,$tcomments,$con); echo $result; and here is my upconticketinfo() php function function upcomticketinfo($tno,$status,$tname,$rg11,$rg06,$tvpins,$jointer,$cquantity,$nooftv,$misc,$tcomments,$con) { if($con!='' || $con!=NULL) { $this-query = "update booking discription set STATUS='$status',CLOSED ON='$con' where TICKET NO='$tno'"; $this-q_result = mysql_query($this-query,$this-conn) or die(mysql_error()); if($this-q_result) { $query = "update tech detail set TECH NAME='$tname',CABLE RG11='$rg11',CABLE RG06='$rg06',TV PINS USED='$tvpins',JOINTER USED='$jointer',CONNECTOR QTY='$cquantity',NO OF TV='$nooftv',MISC='$misc',TECH COMMENTS='$tcomments' where BOOKING='$tno'"; $q_result = mysql_query($query,$this-conn) or die(mysql_error()); if($q_result) { $response = "updated"; } else { $response = "error"; } } else { $response = "error"; } } else { $this-query = "update booking discription set STATUS='$status' where TICKET NO='$tno'"; $this-q_result = mysql_query($this-query,$this-conn) or die(mysql_error()); if($this-q_result) { $query = "update tech detail set TECH NAME='$tname',CABLE RG11='$rg11',CABLE RG06='$rg06',TV PINS USED='$tvpins',JOINTER USED='$jointer',CONNECTOR QTY='$cquantity',NO OF TV='$nooftv',MISC='$misc',TECH COMMENTS='$tcomments' where BOOKING='$tno'"; $q_result = mysql_query($query,$this-conn) or die(mysql_error()); if($q_result) { $response = "updated"; } else { $response = "error"; } } else { $response = "error"; } } return $response; } Question is that, this code is working just fine in IE8 i.e i am using... but it is not working in FF 3.6.3... I have checked each n everything... One thing is that the code works fine on FF too only when i debug the page with firebug debugger. Otherwise the alert in ajax success shows itself with nothing in it... Help me... Goto link text Enter 6628 in the Ticket No. box under Update Complaint Status section... A new form will open. In that form press update... Try it in FF and IE... IE8 shows the results as needed but FF does not...

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• Why is SQLite3 using covering indices instead of the indices I created?

  - by Geoff

  I have an extremely large database (contacts has ~3 billion entries, people has ~280 million entries, and the other tables have a negligible number of entries). Most other queries I've run are really fast. However, I've encountered a more complicated query that's really slow. I'm wondering if there's any way to speed this up. First of all, here is my schema: CREATE TABLE activities (id INTEGER PRIMARY KEY, name TEXT NOT NULL); CREATE TABLE contacts ( id INTEGER PRIMARY KEY, person1_id INTEGER NOT NULL, person2_id INTEGER NOT NULL, duration REAL NOT NULL, -- hours activity_id INTEGER NOT NULL -- FOREIGN_KEY(person1_id) REFERENCES people(id), -- FOREIGN_KEY(person2_id) REFERENCES people(id) ); CREATE TABLE people ( id INTEGER PRIMARY KEY, state_id INTEGER NOT NULL, county_id INTEGER NOT NULL, age INTEGER NOT NULL, gender TEXT NOT NULL, -- M or F income INTEGER NOT NULL -- FOREIGN_KEY(state_id) REFERENCES states(id) ); CREATE TABLE states ( id INTEGER PRIMARY KEY, name TEXT NOT NULL, abbreviation TEXT NOT NULL ); CREATE INDEX activities_name_index on activities(name); CREATE INDEX contacts_activity_id_index on contacts(activity_id); CREATE INDEX contacts_duration_index on contacts(duration); CREATE INDEX contacts_person1_id_index on contacts(person1_id); CREATE INDEX contacts_person2_id_index on contacts(person2_id); CREATE INDEX people_age_index on people(age); CREATE INDEX people_county_id_index on people(county_id); CREATE INDEX people_gender_index on people(gender); CREATE INDEX people_income_index on people(income); CREATE INDEX people_state_id_index on people(state_id); CREATE INDEX states_abbreviation_index on states(abbreviation); CREATE INDEX states_name_index on states(name); Note that I've created an index on every column in the database. I don't care about the size of the database; speed is all I care about. Here's an example of a query that, as expected, runs almost instantly: SELECT count(*) FROM people, states WHERE people.state_id=states.id and states.abbreviation='IA'; Here's the troublesome query: SELECT * FROM contacts WHERE rowid IN (SELECT contacts.rowid FROM contacts, people, states WHERE contacts.person1_id=people.id AND people.state_id=states.id AND states.name='Kansas' INTERSECT SELECT contacts.rowid FROM contacts, people, states WHERE contacts.person2_id=people.id AND people.state_id=states.id AND states.name='Missouri'); Now, what I think would happen is that each subquery would use each relevant index I've created to speed this up. However, when I show the query plan, I see this: sqlite> EXPLAIN QUERY PLAN SELECT * FROM contacts WHERE rowid IN (SELECT contacts.rowid FROM contacts, people, states WHERE contacts.person1_id=people.id AND people.state_id=states.id AND states.name='Kansas' INTERSECT SELECT contacts.rowid FROM contacts, people, states WHERE contacts.person2_id=people.id AND people.state_id=states.id AND states.name='Missouri'); 0|0|0|SEARCH TABLE contacts USING INTEGER PRIMARY KEY (rowid=?) (~25 rows) 0|0|0|EXECUTE LIST SUBQUERY 1 2|0|2|SEARCH TABLE states USING COVERING INDEX states_name_index (name=?) (~1 rows) 2|1|1|SEARCH TABLE people USING COVERING INDEX people_state_id_index (state_id=?) (~5569556 rows) 2|2|0|SEARCH TABLE contacts USING COVERING INDEX contacts_person1_id_index (person1_id=?) (~12 rows) 3|0|2|SEARCH TABLE states USING COVERING INDEX states_name_index (name=?) (~1 rows) 3|1|1|SEARCH TABLE people USING COVERING INDEX people_state_id_index (state_id=?) (~5569556 rows) 3|2|0|SEARCH TABLE contacts USING COVERING INDEX contacts_person2_id_index (person2_id=?) (~12 rows) 1|0|0|COMPOUND SUBQUERIES 2 AND 3 USING TEMP B-TREE (INTERSECT) In fact, if I show the query plan for the first query I posted, I get this: sqlite> EXPLAIN QUERY PLAN SELECT count(*) FROM people, states WHERE people.state_id=states.id and states.abbreviation='IA'; 0|0|1|SEARCH TABLE states USING COVERING INDEX states_abbreviation_index (abbreviation=?) (~1 rows) 0|1|0|SEARCH TABLE people USING COVERING INDEX people_state_id_index (state_id=?) (~5569556 rows) Why is SQLite using covering indices instead of the indices I created? Shouldn't the search in the people table be able to happen in log(n) time given state_id which in turn is found in log(n) time?

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• UIButton performance in UITableViewCell vs UIView

  - by marcel salathe

  I'd like to add a UIButton to a custom UITableViewCell (programmatically). This is easy to do, but I'm finding that the "performance" of the button in the cell is slow - that is, when I touch the button, there is quite a bit of delay until the button visually goes into the highlighted state. The same type of button on a regular UIView is very responsive in comparison. In order to isolate the problem, I've created two views - one is a simple UIView, the other is a UITableView with only one UITableViewCell. I've added buttons to both views (the UIView and the UITableViewCell), and the performance difference is quite striking. I've searched the web and read the Apple docs but haven't really found the cause of the problem. My guess is that it somehow has to do with the responder chain, but I can't quite put my finger on it. I must be doing something wrong, and I'd appreciate any help. Thanks. Demo code: ViewController.h #import <UIKit/UIKit.h> @interface ViewController : UIViewController <UITableViewDelegate, UITableViewDataSource> @property UITableView* myTableView; @property UIView* myView; ViewController.m #import "ViewController.h" #import "CustomCell.h" @implementation ViewController @synthesize myTableView, myView; - (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil { self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil]; if (self) { [self initMyView]; [self initMyTableView]; } return self; } - (void) initMyView { UIView* newView = [[UIView alloc] initWithFrame:CGRectMake(0,0,[[UIScreen mainScreen] bounds].size.width,100)]; self.myView = newView; // button on regularView UIButton* myButton = [UIButton buttonWithType:UIButtonTypeRoundedRect]; [myButton addTarget:self action:@selector(pressedMyButton) forControlEvents:UIControlEventTouchUpInside]; [myButton setTitle:@"I'm fast" forState:UIControlStateNormal]; [myButton setFrame:CGRectMake(20.0, 10.0, 160.0, 30.0)]; [[self myView] addSubview:myButton]; } - (void) initMyTableView { UITableView *newTableView = [[UITableView alloc] initWithFrame:CGRectMake(0,100,[[UIScreen mainScreen] bounds].size.width,[[UIScreen mainScreen] bounds].size.height-100) style:UITableViewStyleGrouped]; self.myTableView = newTableView; self.myTableView.delegate = self; self.myTableView.dataSource = self; } -(void) pressedMyButton { NSLog(@"pressedMyButton"); } - (void)viewDidLoad { [super viewDidLoad]; [[self view] addSubview:self.myView]; [[self view] addSubview:self.myTableView]; } - (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView { return 1; } - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { return 1; } - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { CustomCell *customCell = [tableView dequeueReusableCellWithIdentifier:@"CustomCell"]; if (customCell == nil) { customCell = [[CustomCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:@"CustomCell"]; } return customCell; } @end CustomCell.h #import <UIKit/UIKit.h> @interface CustomCell : UITableViewCell @property (retain, nonatomic) UIButton* cellButton; @end CustomCell.m #import "CustomCell.h" @implementation CustomCell @synthesize cellButton; - (id)initWithStyle:(UITableViewCellStyle)style reuseIdentifier:(NSString *)reuseIdentifier { self = [super initWithStyle:style reuseIdentifier:reuseIdentifier]; if (self) { // button within cell cellButton = [UIButton buttonWithType:UIButtonTypeRoundedRect]; [cellButton addTarget:self action:@selector(pressedCellButton) forControlEvents:UIControlEventTouchUpInside]; [cellButton setTitle:@"I'm sluggish" forState:UIControlStateNormal]; [cellButton setFrame:CGRectMake(20.0, 10.0, 160.0, 30.0)]; [self addSubview:cellButton]; } return self; } - (void) pressedCellButton { NSLog(@"pressedCellButton"); } @end

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