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• GSL-GNU in Visual studio

  - by Arman

  I have visual studio 2008, I want to integrate GSL library in my project, kindly give me some guidelines so that I can make it possible. I have added the GSL library but the following error come. Error 1 error LNK2028: unresolved token (0A000010) "extern "C" void __cdecl gsl_matrix_set(struct gsl_matrix *,unsigned int,unsigned int,double)" (?gsl_matrix_set@@$$J0YAXPAUgsl_matrix@@IIN@Z) referenced in function "int __cdecl main(void)" (?main@@$$HYAHXZ) Error 2 error LNK2028: unresolved token (0A000011) "extern "C" struct gsl_matrix * __cdecl gsl_matrix_alloc(unsigned int,unsigned int)" (?gsl_matrix_alloc@@$$J0YAPAUgsl_matrix@@II@Z) referenced in function "int __cdecl main(void)" (?main@@$$HYAHXZ) Error 3 error LNK2028: unresolved token (0A000014) "extern "C" double __cdecl gsl_matrix_get(struct gsl_matrix const *,unsigned int,unsigned int)" (?gsl_matrix_get@@$$J0YANPBUgsl_matrix@@II@Z) referenced in function "int __cdecl main(void)" (?main@@$$HYAHXZ) Error 4 error LNK2019: unresolved external symbol "extern "C" double __cdecl gsl_matrix_get(struct gsl_matrix const *,unsigned int,unsigned int)" (?gsl_matrix_get@@$$J0YANPBUgsl_matrix@@II@Z) referenced in function "int __cdecl main(void)" (?main@@$$HYAHXZ) Error 5 error LNK2019: unresolved external symbol "extern "C" void __cdecl gsl_matrix_set(struct gsl_matrix *,unsigned int,unsigned int,double)" (?gsl_matrix_set@@$$J0YAXPAUgsl_matrix@@IIN@Z) referenced in function "int __cdecl main(void)" (?main@@$$HYAHXZ)

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• Wpf progressbar not updating during method calculation

  - by djerry

  Hey guys, In my app, i have an import option, to read info from a .csv or .txt file and write it to a database. To test, i"m just using 200-300 lines of data. At the beginning of the method, i calculate number of objects/lines to be read. Every time an object is written to the database, i want to update my progressbar. This is how i do it : private void Update(string path) { double lines = 0; using (StreamReader reader = new StreamReader(path)) while ((reader.ReadLine()) != null) lines++; if (lines != 0) { double progress = 0; string lijn; double value = 0; List<User> users = new List<User>(); using (StreamReader reader = new StreamReader(path)) while ((line = reader.ReadLine()) != null) { progress++; value = (progress / lines) * 100.0; updateProgressBar(value); try { User user = ProcessLine(lijn); } catch (ArgumentOutOfRangeException) { continue; } catch (Exception) { continue; } } return; } else { //non relevant code } } To update my progressbar, i'm checking if i can change the ui of the progressbar like this : delegate void updateProgressbarCallback(double value); private void updateProgressBar(double value) { if (pgbImportExport.Dispatcher.CheckAccess() == false) { updateProgressbarCallback uCallBack = new updateProgressbarCallback(updateProgressBar); pgbImportExport.Dispatcher.Invoke(uCallBack, value); } else { Console.WriteLine(value); pgbImportExport.Value = value; } } When i!m looking at the output, the values are calculated correctly, but the progressbar is only showing changes after the method has been called completely, so when the job is done. That's too late to show feedback to the user. Can anyone help me solve this. EDIT : I'm also trying to show some text in labels to tell te user what is being done, and those aren't udpated till after the method is complete. Thanks in advance.

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• Resilient backpropagation neural network - question about gradient

  - by Raf

  Hello Guys, First I want to say that I'm really new to neural networks and I don't understand it very good ;) I've made my first C# implementation of the backpropagation neural network. I've tested it using XOR and it looks it work. Now I would like change my implementation to use resilient backpropagation (Rprop - http://en.wikipedia.org/wiki/Rprop). The definition says: "Rprop takes into account only the sign of the partial derivative over all patterns (not the magnitude), and acts independently on each "weight". Could somebody tell me what partial derivative over all patterns is? And how should I compute this partial derivative for a neuron in hidden layer. Thanks a lot UPDATE: My implementation base on this Java code: www_.dia.fi.upm.es/~jamartin/downloads/bpnn.java My backPropagate method looks like this: public double backPropagate(double[] targets) { double error, change; // calculate error terms for output double[] output_deltas = new double[outputsNumber]; for (int k = 0; k < outputsNumber; k++) { error = targets[k] - activationsOutputs[k]; output_deltas[k] = Dsigmoid(activationsOutputs[k]) * error; } // calculate error terms for hidden double[] hidden_deltas = new double[hiddenNumber]; for (int j = 0; j < hiddenNumber; j++) { error = 0.0; for (int k = 0; k < outputsNumber; k++) { error = error + output_deltas[k] * weightsOutputs[j, k]; } hidden_deltas[j] = Dsigmoid(activationsHidden[j]) * error; } //update output weights for (int j = 0; j < hiddenNumber; j++) { for (int k = 0; k < outputsNumber; k++) { change = output_deltas[k] * activationsHidden[j]; weightsOutputs[j, k] = weightsOutputs[j, k] + learningRate * change + momentumFactor * lastChangeWeightsForMomentumOutpus[j, k]; lastChangeWeightsForMomentumOutpus[j, k] = change; } } // update input weights for (int i = 0; i < inputsNumber; i++) { for (int j = 0; j < hiddenNumber; j++) { change = hidden_deltas[j] * activationsInputs[i]; weightsInputs[i, j] = weightsInputs[i, j] + learningRate * change + momentumFactor * lastChangeWeightsForMomentumInputs[i, j]; lastChangeWeightsForMomentumInputs[i, j] = change; } } // calculate error error = 0.0; for (int k = 0; k < outputsNumber; k++) { error = error + 0.5 * (targets[k] - activationsOutputs[k]) * (targets[k] - activationsOutputs[k]); } return error; } So can I use change = hidden_deltas[j] * activationsInputs[i] variable as a gradient (partial derivative) for checking the sing?

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• Python: Create a duplicate of an array

  - by Dan

  I have an double array alist[1][1]=-1 alist2=[] for x in xrange(10): alist2.append(alist[x]) alist2[1][1]=15 print alist[1][1] and I get 15. Clearly I'm passing a pointer rather than an actual variable... Is there an easy way to make a seperate double array (no shared pointers) without having to do a double for loop? Thanks, Dan

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• Regex to split on successions of newline characters

  - by Beau Martínez

  I'm trying to split a string on newline characters (catering for Windows, OS X, and Unix text file newline characters). If there are any succession of these, I want to split on that too and not include any in the result. So, for when splitting the following: "Foo\r\n\r\nDouble Windows\r\rDouble OS X\n\nDouble Unix\r\nWindows\rOS X\nUnix" The result would be: ['Foo', 'Double Windows', 'Double OS X', 'Double Unix', 'Windows', 'OS X', 'Unix'] What regex should I use?

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• Are this 2 code parts same?

  - by Samvel Siradeghyan

  private double memberVal; public double MemberVal { get { return memberVal; } set { memberVal= value; } } and private double MemberVal { get; set; }

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• What is CDbl doing?

  - by Dan Tao

  I had until recently been under the impression that the CDbl(x) operation in VB.NET was essentially a cast (i.e., the VB equivalent of (double)x in C#); but a recent discovery has revealed that this is not the case. If I have this string: Dim s As String = "12345.12345-" And I do this: Dim d As Double = CDbl(s) d will be set to the value -12345.12345! Now, don't get me wrong, this is kind of convenient in my particular scenario; but I have to admit I'm confused as to why this works. In particular, I'm confused because: Double.Parse does not work with the above input. Double.TryParse does not work. Convert.ToDouble does not work. How is CDbl so clever?

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• Can a GeneralPath be modified?

  - by Dov

  java2d is fairly expressive, but requires constructing lots of objects. In contrast, the older API would let you call methods to draw various shapes, but lacks all the new features like transparency, stroke, etc. Java has fairly high costs associated with object creation. For speed, I would like to create a GeneralPath whose structure does not change, but go in and change the x,y points inside. path = new GeneralPath(GeneralPath.WIND_EVEN_ODD, 10); path.moveTo(x,y); path.lineTo(x2, y2); double len = Math.sqrt((x2-x)*(x2-x) + (y2-y)*(y2-y)); double dx = (x-x2) * headLen / len; double dy = (y-y2) * headLen / len; double dx2 = -dy * (headWidth/headLen); double dy2 = dx * (headWidth/headLen); path.lineTo(x2 + dx + dx2, y2 + dy + dy2); path.moveTo(x2 + dx - dx2, y2 + dy - dy2); path.lineTo(x2,y2); This one isn't even that long. Imagine a much longer sequence of commands, and only the ones on the end are changing. I just want to be able to overwrite commands, to have an iterator effectively. Does that exist?

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• Inline & not-inline

  - by anon

  Suppose I have: struct Vec3 { double x; double y; double z; } ; inline double dot(const Vec3& lhs, const Vec3& rhs) { return lhs.x * rhs.x + lhs.y * rhs.y + lhs.z * rhs.z ; } Is it possible to have "dot" also exist in a non-inlined version, so that it can be in the *.so , so that when I dl open it I can call it? I.e. I want files that include the above header to use the inlined version, but I also want the function to exist in a *.so, so I can dl open it and call it dynamically.

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• Sorting an array of Doubles with NaN in it

  - by Agent Worm

  This is more of a 'Can you explain this' type of question than it is anything else. I came across a problem at work where we were using NaN values in a table, but when the table was sorted, it came out in a very strange, strange manner. I figured NaN was mucking up something so I wrote up a test application to see if this is true. This is what I did. static void Main(string[] args) { double[] someArray = { 4.0, 2.0, double.NaN, 1.0, 5.0, 3.0, double.NaN, 10.0, 9.0, 8.0 }; foreach (double db in someArray) { Console.WriteLine(db); } Array.Sort(someArray); Console.WriteLine("\n\n"); foreach (double db in someArray) { Console.WriteLine(db); } Console.ReadLine(); } Which gave the result: Before: 4,2,NaN,1,5,3,NaN,10,9,8 After: 1,4,NaN,2,3,5,8,9,10,NaN So yes, the NaN some how made the sorted array to be sorted in a strange way. To quote Fry; "Why is those things?"

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• How to zoom in google map (J2ME)

  - by Nivek

  Hi all, I am trying to develop a J2ME application that could retrieve the google map by passing in the GPS coordinates. From http://wiki.forum.nokia.com/index.php/Google_Maps_API_in_Java_ME, it provides the Utility method for map scrolling. Basically it states that i need to include MicroFloat library in my project. Here's what i did (Not sure if i am doing it right) Create a project, build the code. Add the jar file into my current project lib. but i am still getting error from codes. Example double LToY(double y) { return Math.round( offset - radius * Double.longBitsToDouble(MicroDouble.log( Double.doubleToLongBits( (1 + Math.sin(Math.toRadians(y))) / (1 - Math.sin(Math.toRadians(y))) ) )) / 2); } Am i missing any import statment??? Btw i am using netbeans 6.5. Thanks for any guidance... Kevin

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• Abstract Methods in "Product" - Factory Method C#

  - by Regina Foo

  I have a simple class library (COM+ service) written in C# to consume 5 web services: Add, Minus, Divide, Multiply and Compare. I've created the abstract product and abstract factory classes. The abstract product named WS's code: public abstract class WS { public abstract double Calculate(double a, double b); public abstract string Compare(double a, double b); } As you see, when one of the subclasses inherits WS, both methods must be overridden which might not be useful in some subclasses. E.g. Compare doesn't need Calculate() method. To instantiate a new CompareWS object, the client class will call the CreateWS() method which returns a WS object type. public class CompareWSFactory : WSFactory { public override WS CreateWS() { return new CompareWS(); } } But if Compare() is not defined as abstract in WS, the Compare() method cannot be invoked. This is only an example with two methods, but what if there are more methods? Is it stupid to define all the methods as abstract in the WS class? My question is: I want to define abstract methods that are common to all subclasses of WS whereas when the factory creates a WS object type, all the methods of the subclasses can be invoked (overridden methods of WS and also the methods in subclasses). How should I do this?

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• Why is numpy's einsum faster than numpy's built in functions?

  - by Ophion

  Lets start with three arrays of dtype=np.double. Timings are performed on a intel CPU using numpy 1.7.1 compiled with icc and linked to intel's mkl. A AMD cpu with numpy 1.6.1 compiled with gcc without mkl was also used to verify the timings. Please note the timings scale nearly linearly with system size and are not due to the small overhead incurred in the numpy functions if statements these difference will show up in microseconds not milliseconds: arr_1D=np.arange(500,dtype=np.double) large_arr_1D=np.arange(100000,dtype=np.double) arr_2D=np.arange(500**2,dtype=np.double).reshape(500,500) arr_3D=np.arange(500**3,dtype=np.double).reshape(500,500,500) First lets look at the np.sum function: np.all(np.sum(arr_3D)==np.einsum('ijk->',arr_3D)) True %timeit np.sum(arr_3D) 10 loops, best of 3: 142 ms per loop %timeit np.einsum('ijk->', arr_3D) 10 loops, best of 3: 70.2 ms per loop Powers: np.allclose(arr_3D*arr_3D*arr_3D,np.einsum('ijk,ijk,ijk->ijk',arr_3D,arr_3D,arr_3D)) True %timeit arr_3D*arr_3D*arr_3D 1 loops, best of 3: 1.32 s per loop %timeit np.einsum('ijk,ijk,ijk->ijk', arr_3D, arr_3D, arr_3D) 1 loops, best of 3: 694 ms per loop Outer product: np.all(np.outer(arr_1D,arr_1D)==np.einsum('i,k->ik',arr_1D,arr_1D)) True %timeit np.outer(arr_1D, arr_1D) 1000 loops, best of 3: 411 us per loop %timeit np.einsum('i,k->ik', arr_1D, arr_1D) 1000 loops, best of 3: 245 us per loop All of the above are twice as fast with np.einsum. These should be apples to apples comparisons as everything is specifically of dtype=np.double. I would expect the speed up in an operation like this: np.allclose(np.sum(arr_2D*arr_3D),np.einsum('ij,oij->',arr_2D,arr_3D)) True %timeit np.sum(arr_2D*arr_3D) 1 loops, best of 3: 813 ms per loop %timeit np.einsum('ij,oij->', arr_2D, arr_3D) 10 loops, best of 3: 85.1 ms per loop Einsum seems to be at least twice as fast for np.inner, np.outer, np.kron, and np.sum regardless of axes selection. The primary exception being np.dot as it calls DGEMM from a BLAS library. So why is np.einsum faster that other numpy functions that are equivalent? The DGEMM case for completeness: np.allclose(np.dot(arr_2D,arr_2D),np.einsum('ij,jk',arr_2D,arr_2D)) True %timeit np.einsum('ij,jk',arr_2D,arr_2D) 10 loops, best of 3: 56.1 ms per loop %timeit np.dot(arr_2D,arr_2D) 100 loops, best of 3: 5.17 ms per loop The leading theory is from @sebergs comment that np.einsum can make use of SSE2, but numpy's ufuncs will not until numpy 1.8 (see the change log). I believe this is the correct answer, but have not been able to confirm it. Some limited proof can be found by changing the dtype of input array and observing speed difference and the fact that not everyone observes the same trends in timings.

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• How can I make a WPF combo box have the width of its widest element in XAML ?

  - by csuporj

  I know how to do it in code, but can this be done in XAML ? Window1.xaml: <Window x:Class="WpfApplication1.Window1" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="Window1" Height="300" Width="300"> <Grid> <ComboBox Name="ComboBox1" HorizontalAlignment="Left" VerticalAlignment="Top"> <ComboBoxItem>ComboBoxItem1</ComboBoxItem> <ComboBoxItem>ComboBoxItem2</ComboBoxItem> </ComboBox> </Grid> </Window> Window1.xaml.cs: using System.Windows; using System.Windows.Controls; namespace WpfApplication1 { public partial class Window1 : Window { public Window1() { InitializeComponent(); double width = 0; foreach (ComboBoxItem item in ComboBox1.Items) { item.Measure(new Size( double.PositiveInfinity, double.PositiveInfinity)); if (item.DesiredSize.Width > width) width = item.DesiredSize.Width; } ComboBox1.Measure(new Size( double.PositiveInfinity, double.PositiveInfinity)); ComboBox1.Width = ComboBox1.DesiredSize.Width + width; } } }

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• WPF Toolkit: Nullable object must have a value

  - by Via Lactea

  Hi All, I am trying to create some line charts from a dataset and getting an error (WPF+WPF Toolkit + C#): Nullable object must have a value Here is a code that I use to add some data points to the chart: ObservableCollection points = new ObservableCollection(); foreach (DataRow dr in dc.Tables[0].Rows) { points.Add(new VelChartPoint() { Label = dr[0].ToString(), Value = double.Parse(dr[1].ToString()) }); } Here is a class VelChartPoint public class VelChartPoint : VelObject, INotifyPropertyChanged { public DateTime Date { get; set; } public string Label { get; set; } private double _Value; public double Value { get { return _Value; } set { _Value = value; var handler = PropertyChanged; if (null != handler) { handler.Invoke(this, new PropertyChangedEventArgs("Value")); } } } public string FieldName { get; set; } public event PropertyChangedEventHandler PropertyChanged; public VelChartPoint() { } } So the problem occures in this part of the code points.Add(new VelChartPoint { Name = dc.Tables[0].Rows[0][0].ToString(), Value = double.Parse(dc.Tables[0].Rows[0][1].ToString()) } ); I've made some tests, here are some results i've found out. This part of code does'nt work for me: string[] labels = new string[] { "label1", "label2", "label3" }; foreach (string label in labels) { points.Add(new VelChartPoint { Name = label, Value = 500.0 } ); } But this one works fine: points.Add(new VelChartPoint { Name = "LabelText", Value = double.Parse(dc.Tables[0].Rows[0][1].ToString()) } ); Please, help me to solve this error.

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• TextField - behave like PowerPoint

  - by user310113

  I have a Dynamic TextField created with ActionScript (multiline, wordwrap & autosize=true). While running the SWF, if you click into the TextField you get an arrow "move" cursor, then you can double-click to put it into Edit mode to select text. I want it to work like PowerPoint - if you click into the box you'll always get a flashing cursor with the ability to select/insert text, and you can click on the borders to drag, or the corners to resize. I tried adding the focusIn event textField.stage.focus = this.textField but this didn't seem to do anything. When you click into the textField, I basically want it to act as though you followed with a double-click (Edit mode) without actually having to do the double-click. Bonus: and instead of a 2nd double-click returning you to the Move mode (or whatever it's called) I want to select all text. TL;DR: Is there some property of a Dynamic TextField that I can get/set to see if I'm in Edit or Move mode?

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• Mapping Hashmap of Coordinates in Hibernate with Annotation

  - by paddydub

  I've just started using hibernate and I'm trying to map walking distance between two coordinates into a hashmap, There can be many connections from one "FromCoordinate" to another "ToCoordinate". I'm not sure if i've implemented this correctly, What annotations do i need to map this MashMap? Thanks HashMap coordWalkingConnections = new HashMap(); @Entity @Table(name = "COORDCONNECTIONS") public class CoordinateConnection implements Serializable{ private static final long serialVersionUID = -1624745319005591573L; /** auto increasing id number */ @GeneratedValue(strategy = GenerationType.IDENTITY) @Column(name = "ID") @id private int id; @Embedded public FromCoordinate fromCoord; @Embedded public ToCoordinate toCoord; HashMap<FromCoordinate, ArrayList<ToCoordinate >> coordWalkingConnections = new HashMap<FromCoordinate, ArrayList<ToCoordinate >>(); } public class FromCoordinate implements ICoordinate { @Column(name = "FROM_LAT") private double latitude; @Column(name = "FROM_LNG") private double longitude; } public class ToCoordinate implements ICoordinate { @Column(name = "TO_LAT") private double latitude; @Column(name = "TO_LNG") private double longitude; @Column(name = "DISTANCE") private double distance; } DATABASE STRUCTURE id FROM_LAT FROM_LNG TO_LAT TO_LNG Dist 1 43.352669 -6.264341 43.350012 -6.260653 0.38 2 43.352669 -6.264341 43.352669 -6.264341 0.00 3 46.352669 -6.264341 43.353373 -6.262013 0.17 4 47.352465 -6.265865 43.351290 -6.261200 0.25 5 45.452578 -6.265768 43.352788 -6.264396 0.01 6 45.452578 -6.265768 45.782788 -6.234523 0.01 ..... ... . Example HashMap for HashMap<Coordinate, ArrayList<Coordinate>> <KEY{43.352669 -6.264341}, Arraylist VALUES{(43.350012,-6.260653,0.383657), (43.352669, -6.264341, 0.000095), (43.353373, -6.262013, 0.173201)}> <KEY{47.352465 -6.265865}, Arraylist VALUES{(43.351290,-6.261200,0.258781)}> <KEY{45.452578 -6.265768}, Arraylist VALUES{(43.352788,-6.264396,0.013726),(45.782788,-6.234523,0.017726)}>

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• Hibernate Mapping Annotation Question?

  - by paddydub

  I've just started using hibernate and I'm trying to map walking distance between two coordinates into a hashmap, There can be many connections from one "FromCoordinate" to another "ToCoordinate". I'm not sure if i've implemented this correctly, What annotations do i need to map this MashMap? Thanks @Entity @Table(name = "COORDCONNECTIONS") public class CoordinateConnection implements Serializable{ private static final long serialVersionUID = -1624745319005591573L; /** auto increasing id number */ @GeneratedValue(strategy = GenerationType.IDENTITY) @Column(name = "ID") @id private int id; @Embedded public FromCoordinate fromCoord; @Embedded public ToCoordinate toCoord; HashMap<Coordinate, ArrayList<Coordinate>> coordWalkingConnections = new HashMap<Coordinate, ArrayList<Coordinate>>(); } public class FromCoordinate implements ICoordinate { @Column(name = "FROM_LAT") private double latitude; @Column(name = "FROM_LNG") private double longitude; } public class ToCoordinate implements ICoordinate { @Column(name = "TO_LAT") private double latitude; @Column(name = "TO_LNG") private double longitude; @Column(name = "DISTANCE") private double distance; } DATABASE STRUCTURE id FROM_LAT FROM_LNG TO_LAT TO_LNG Dist 1 43.352669 -6.264341 43.350012 -6.260653 0.38 2 43.352669 -6.264341 43.352669 -6.264341 0.00 3 46.352669 -6.264341 43.353373 -6.262013 0.17 4 47.352465 -6.265865 43.351290 -6.261200 0.25 5 45.452578 -6.265768 43.352788 -6.264396 0.01 6 45.452578 -6.265768 45.782788 -6.234523 0.01 ..... ... . Example HashMap for HashMap<Coordinate, ArrayList<Coordinate>> <KEY{43.352669 -6.264341}, Arraylist VALUES{(43.350012,-6.260653,0.383657), (43.352669, -6.264341, 0.000095), (43.353373, -6.262013, 0.173201)}> <KEY{47.352465 -6.265865}, Arraylist VALUES{(43.351290,-6.261200,0.258781)}> <KEY{45.452578 -6.265768}, Arraylist VALUES{(43.352788,-6.264396,0.013726),(45.782788,-6.234523,0.017726)}>

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• Date exception when trying to use date method

  - by Simon Andi

  Hi, I have defined a object model where one of the array elements is a string public static String[] columnNames6 = {"Total Shares", "Total Calls", "Call Strike", "Call Premium", "Call Expiry" }; public static Object[][] data6 = { { new Double(0), new Double(0), new Double(0), new Double(0),"dd/mm/yyyy"}, }; I then use the following code to get the date so that I can use the data method but having no joy - Can someone please tell me why it is throwing an exception after I do this String ExpiryDate = (String)GV.data6[0][4]; System.out.println("DATE STRING IS: " + ExpiryDate); Date EndOptionDate = new Date(ExpiryDate); // SOMETHING WRONG HERE even though it compiles okay //Get Todays's Date Date TodaysDate = new Date(); //Calculate Days Option Expiry long DaysDifference = EndOptionDate.getTime() - TodaysDate.getTime(); Would really appreciate some help as really stuck not sure how I should code the line in bold - new to java, so please excuses my lack of knowledge looked at tutorials can't seem to move forward. Thanks Simon

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• Haskell math performance

  - by Travis Brown

  I'm in the middle of porting David Blei's original C implementation of Latent Dirichlet Allocation to Haskell, and I'm trying to decide whether to leave some of the low-level stuff in C. The following function is one example—it's an approximation of the second derivative of lgamma: double trigamma(double x) { double p; int i; x=x+6; p=1/(x*x); p=(((((0.075757575757576*p-0.033333333333333)*p+0.0238095238095238) *p-0.033333333333333)*p+0.166666666666667)*p+1)/x+0.5*p; for (i=0; i<6 ;i++) { x=x-1; p=1/(x*x)+p; } return(p); } I've translated this into more or less idiomatic Haskell as follows: trigamma :: Double -> Double trigamma x = snd $ last $ take 7 $ iterate next (x' - 1, p') where x' = x + 6 p = 1 / x' ^ 2 p' = p / 2 + c / x' c = foldr1 (\a b -> (a + b * p)) [1, 1/6, -1/30, 1/42, -1/30, 5/66] next (x, p) = (x - 1, 1 / x ^ 2 + p) The problem is that when I run both through Criterion, my Haskell version is six or seven times slower (I'm compiling with -O2 on GHC 6.12.1). Some similar functions are even worse. I know practically nothing about Haskell performance, and I'm not terribly interested in digging through Core or anything like that, since I can always just call the handful of math-intensive C functions through FFI. But I'm curious about whether there's low-hanging fruit that I'm missing—some kind of extension or library or annotation that I could use to speed up this numeric stuff without making it too ugly.

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• Calling UIGetScreenImage() on manually-spawned thread prints "_NSAutoreleaseNoPool():" message to lo

  - by jtrim

  This is the body of the selector that is specified in NSThread +detachNewThreadSelector:(SEL)aSelector toTarget:(id)aTarget withObject:(id)anArgument NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; while (doIt) { if (doItForSure) { NSLog(@"checking"); doItForSure = NO; (void)gettimeofday(&start, NULL); /* do some stuff */ // the next line prints "_NSAutoreleaseNoPool():" message to the log CGImageRef screenImage = UIGetScreenImage(); /* do some other stuff */ (void)gettimeofday(&end, NULL); elapsed = ((double)(end.tv_sec) + (double)(end.tv_usec) / 1000000) - ((double)(start.tv_sec) + (double)(start.tv_usec) / 1000000); NSLog(@"Time elapsed: %e", elapsed); [pool drain]; } } [pool release]; Even with the autorelease pool present, I get this printed to the log when I call UIGetScreenImage(): 2010-05-03 11:39:04.588 ProjectName[763:5903] *** _NSAutoreleaseNoPool(): Object 0x15a2e0 of class NSCFNumber autoreleased with no pool in place - just leaking Has anyone else seen this with UIGetScreenImage() on a separate thread?

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• Getting timing consistency in Linux

  - by Jim Hunziker

  I can't seem to get a simple program (with lots of memory access) to achieve consistent timing in Linux. I'm using a 2.6 kernel, and the program is being run on a dual-core processor with realtime priority. I'm trying to disable cache effects by declaring the memory arrays as volatile. Below are the results and the program. What are some possible sources of the outliers? Results: Number of trials: 100 Range: 0.021732s to 0.085596s Average Time: 0.058094s Standard Deviation: 0.006944s Extreme Outliers (2 SDs away from mean): 7 Average Time, excluding extreme outliers: 0.059273s Program: #include <stdio.h> #include <stdlib.h> #include <math.h> #include <sched.h> #include <sys/time.h> #define NUM_POINTS 5000000 #define REPS 100 unsigned long long getTimestamp() { unsigned long long usecCount; struct timeval timeVal; gettimeofday(&timeVal, 0); usecCount = timeVal.tv_sec * (unsigned long long) 1000000; usecCount += timeVal.tv_usec; return (usecCount); } double convertTimestampToSecs(unsigned long long timestamp) { return (timestamp / (double) 1000000); } int main(int argc, char* argv[]) { unsigned long long start, stop; double times[REPS]; double sum = 0; double scale, avg, newavg, median; double stddev = 0; double maxval = -1.0, minval = 1000000.0; int i, j, freq, count; int outliers = 0; struct sched_param sparam; sched_getparam(getpid(), &sparam); sparam.sched_priority = sched_get_priority_max(SCHED_FIFO); sched_setscheduler(getpid(), SCHED_FIFO, &sparam); volatile float* data; volatile float* results; data = calloc(NUM_POINTS, sizeof(float)); results = calloc(NUM_POINTS, sizeof(float)); for (i = 0; i < REPS; ++i) { start = getTimestamp(); for (j = 0; j < NUM_POINTS; ++j) { results[j] = data[j]; } stop = getTimestamp(); times[i] = convertTimestampToSecs(stop-start); } free(data); free(results); for (i = 0; i < REPS; i++) { sum += times[i]; if (times[i] > maxval) maxval = times[i]; if (times[i] < minval) minval = times[i]; } avg = sum/REPS; for (i = 0; i < REPS; i++) stddev += (times[i] - avg)*(times[i] - avg); stddev /= REPS; stddev = sqrt(stddev); for (i = 0; i < REPS; i++) { if (times[i] > avg + 2*stddev || times[i] < avg - 2*stddev) { sum -= times[i]; outliers++; } } newavg = sum/(REPS-outliers); printf("Number of trials: %d\n", REPS); printf("Range: %fs to %fs\n", minval, maxval); printf("Average Time: %fs\n", avg); printf("Standard Deviation: %fs\n", stddev); printf("Extreme Outliers (2 SDs away from mean): %d\n", outliers); printf("Average Time, excluding extreme outliers: %fs\n", newavg); return 0; }

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• pinpointing "conditional jump or move depends on uninitialized value(s)" valgrind message

  - by kamziro

  So I've been getting some mysterious uninitialized values message from valgrind and it's been quite the mystery as of where the bad value originated from. Seems that valgrind shows the place where the unitialised value ends up being used, but not the origin of the uninitialised value. ==11366== Conditional jump or move depends on uninitialised value(s) ==11366== at 0x43CAE4F: __printf_fp (in /lib/tls/i686/cmov/libc-2.7.so) ==11366== by 0x43C6563: vfprintf (in /lib/tls/i686/cmov/libc-2.7.so) ==11366== by 0x43EAC03: vsnprintf (in /lib/tls/i686/cmov/libc-2.7.so) ==11366== by 0x42D475B: (within /usr/lib/libstdc++.so.6.0.9) ==11366== by 0x42E2C9B: std::ostreambuf_iterator<char, std::char_traits<char> > std::num_put<char, std::ostreambuf_iterator<char, std::char_traits<char> > >::_M_insert_float<double>(std::ostreambuf_iterator<char, std::char_traits<char> >, std::ios_base&, char, char, double) const (in /usr/lib/libstdc++.so.6.0.9) ==11366== by 0x42E31B4: std::num_put<char, std::ostreambuf_iterator<char, std::char_traits<char> > >::do_put(std::ostreambuf_iterator<char, std::char_traits<char> >, std::ios_base&, char, double) const (in /usr/lib/libstdc++.so.6.0.9) ==11366== by 0x42EE56F: std::ostream& std::ostream::_M_insert<double>(double) (in /usr/lib/libstdc++.so.6.0.9) ==11366== by 0x81109ED: Snake::SnakeBody::syncBodyPos() (ostream:221) ==11366== by 0x810B9F1: Snake::Snake::update() (snake.cpp:257) ==11366== by 0x81113C1: SnakeApp::updateState() (snakeapp.cpp:224) ==11366== by 0x8120351: RoenGL::updateState() (roengl.cpp:1180) ==11366== by 0x81E87D9: Roensachs::update() (rs.cpp:321) As can be seen, it gets quite cryptic.. especially because when it's saying by Class::MethodX, it sometimes points straight to ostream etc. Perhaps this is due to optimization? ==11366== by 0x81109ED: Snake::SnakeBody::syncBodyPos() (ostream:221) Just like that. Is there something I'm missing? What is the best way to catch bad values without having to resort to super-long printf detective work?

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• What are the hibernate annotations used to persist a value typed Map with an enumerated type as a ke

  - by Jason Novak

  I am having trouble getting the right hibernate annotations to use on a value typed Map with an enumerated class as a key. Here is a simplified (and extremely contrived) example. public class Thing { public String id; public Letter startLetter; public Map<Letter,Double> letterCounts = new HashMap<Letter, Double>(); } public enum Letter { A, B, C, D } Here are my current annotations on Thing @Entity public class Thing { @Id public String id; @Enumerated(EnumType.STRING) public Letter startLetter; @CollectionOfElements @JoinTable(name = "Thing_letterFrequencies", joinColumns = @JoinColumn(name = "thingId")) @MapKey(columns = @Column(name = "letter", nullable = false)) @Column(name = "count") public Map<Letter,Double> letterCounts = new HashMap<Letter, Double>(); } Hibernate generates the following DDL to create the tables for my MySql database create table Thing (id varchar(255) not null, startLetter varchar(255), primary key (id)) type=InnoDB; create table Thing_letterFrequencies (thingId varchar(255) not null, count double precision, letter tinyblob not null, primary key (thingId, letter)) type=InnoDB; Notice that hibernate tries to define letter (my map key) as a tinyblob, however it defines startLetter as a varchar(255) even though both are of the enumerated type Letter. When I try to create the tables I see the following error BLOB/TEXT column 'letter' used in key specification without a key length I googled this error and it appears that MySql has issues when you try to make a tinyblob column part of a primary key, which is what hibernate needs to do with the Thing_letterFrequencies table. So I would rather have letter mapped to a varchar(255) the way startLetter is. Unfortunately, I've been fussing with the MapKey annotation for a while now and haven't been able to make this work. I've also tried @MapKeyManyToMany(targetEntity=Product.class) without success. Can anyone tell me what are the correct annotations for my letterCounts map so that hibernate will treat the letterCounts map key the same way it does startLetter?

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• Post method in Servlet is not being called again after being executed once

  - by SaurabhCsIITKgp

  I am implementing a database based web application using servlets. Now, when I input a parameter using a form in the jsp page, it redirects it to a servlet which subsequently adds the value to the database (the servlet creates a new table if the table doesn't already exist). The creation of the table and the addition of value works fine if the table doesn't already exists. Once it is created however and the parameter is inputted again in the form, the submit button no longer redirects it to the servlet. Nor is the value added to the database. Kindly advise me as to where I am going wrong. Following are the snippets of my code: From the JSP page (/showmanager is the urlpattern of the servlet): <form action="showmanager" method="post"> <h3>Enter name of the show: </h3> <input type="text" name="showname" value=""> <input type="hidden" name="task" value="addshow" /> <input type="button" value="Add Show"> </form> From the servlet (POST method): p rotected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { if(request.getParameter("task").equals("addshow")){ this.addShow(request.getParameter("showname")); response.sendRedirect("showmanager.jsp"); } } Method to add in database: protected boolean addShow(String showname){ try{ statement =con.prepareStatement("INSERT INTO showdb10(name) VALUES ('"+showname+"')"); if(statement.executeUpdate()>0){ return true; } } catch(Exception e) { try{ statement =con.prepareStatement("create table showdb10 (id int NOT NULL AUTO_INCREMENT, name varchar(255) NOT NULL, date varchar(20),time varchar(20), b_total int, o_total int, b_avbl int, o_avbl int, b_price double(10,2), o_price double(10,2), seat_no varchar(20), transaction_id varchar(255), total_sales double(10,2), paymnt_artists double(10,2), paymnt_othr double(10,2), flag varchar(20), PRIMARY KEY(id))"); statement.executeUpdate(); statement =con.prepareStatement("INSERT INTO showdb10(name) VALUES ('"+showname+"')"); if(statement.executeUpdate()>0){ return true; } }catch(Exception e2){} } return false; }

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