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  • Can you have multiple clipping regions in an HTML Canvas?

    - by emh
    I have code that loads a bunch of images into hidden img elements and then a Javascript loop which places each image onto the canvas. However, I want to clip each image so that it is a circle when placed on the canvas. My loop looks like this: $$('#avatars img').each(function(avatar) { var canvas = $('canvas'); var context = canvas.getContext('2d'); var x = Math.floor(Math.random() * canvas.width); var y = Math.floor(Math.random() * canvas.height); context.beginPath(); context.arc(x+24, y+24, 20, 0, Math.PI * 2, 1); context.clip(); context.strokeStyle = "black"; context.drawImage(document.getElementById(avatar.id), x, y); context.stroke(); }); Problem is, only the first image is drawn (or is visible). If I remove the clipping logic: $$('#avatars img').each(function(avatar) { var canvas = $('canvas'); var context = canvas.getContext('2d'); var x = Math.floor(Math.random() * canvas.width); var y = Math.floor(Math.random() * canvas.height); context.drawImage(document.getElementById(avatar.id), x, y); }); Then all my images are drawn. Is there a way to get each image individually clipped? I tried resetting the clipping area to be the entire canvas between images but that didn't work.

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  • constructor function's object literal returns toString() method but no other method

    - by JohnMerlino
    I'm very confused with javascript methods defined in objects and the "this" keyword. In the below example, the toString() method is invoked when Mammal object instantiated: function Mammal(name){ this.name=name; this.toString = function(){ return '[Mammal "'+this.name+'"]'; } } var someAnimal = new Mammal('Mr. Biggles'); alert('someAnimal is '+someAnimal); Despite the fact that the toString() method is not invoked on the object someAnimal like this: alert('someAnimal is '+someAnimal.toString()); It still returns 'someAnimal is [Mammal "Mr. Biggles"]' . That doesn't make sense to me because the toString() function is not being called anywhere. Then to add even more confusion, if I change the toString() method to a method I make up such as random(): function Mammal(name){ this.name=name; this.random = function(){ return Math.floor(Math.random() * 15); } } var someAnimal = new Mammal('Mr. Biggles'); alert(someAnimal); It completely ignores the random method (despite the fact that it is defined the same way was the toString() method was) and returns: [object object] Another issue I'm having trouble understanding with inheritance is the value of "this". For example, in the below example function person(w,h){ width.width = w; width.height = h; } function man(w,h,s) { person.call(this, w, h); this.sex = s; } "this" keyword is being send to the person object clearly. However, does "this" refer to the subclass (man) or the super class (person) when the person object receives it? Thanks for clearing up any of the confusion I have with inheritance and object literals in javascript.

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  • Converted some PHP functions to c# but getting different results

    - by Tom Beech
    With a bit of help from people on here, i've converted the following PHP functions to C# - But I get very different results between the two and can't work out where i've gone wrong: PHP: function randomKey($amount) { $keyset = "abcdefghijklmABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"; $randkey = ""; for ($i=0; $i<$amount; $i++) $randkey .= substr($keyset, rand(0, strlen($keyset)-1), 1); return $randkey; } public static function hashPassword($password) { $salt = self::randomKey(self::SALTLEN); $site = new Sites(); $s = $site->get(); return self::hashSHA1($s->siteseed.$password.$salt.$s->siteseed).$salt; } c# public static string randomKey(int amount) { string keyset = "abcdefghijklmABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"; string randkey = string.Empty; Random random = new Random(); for (int i = 0; i < amount; i++) { randkey += keyset.Substring(0, random.Next(2, keyset.Length - 2)); } return randkey; } static string hashPassword(string password) { string salt = randomKey(4); string siteSeed = "6facef08253c4e3a709e17d9ff4ba197"; return CalculateSHA1(siteSeed + password + salt + siteSeed) + siteSeed; } static string CalculateSHA1(string ipString) { SHA1 sha1 = new SHA1CryptoServiceProvider(); byte[] ipBytes = Encoding.Default.GetBytes(ipString.ToCharArray()); byte[] opBytes = sha1.ComputeHash(ipBytes); StringBuilder stringBuilder = new StringBuilder(40); for (int i = 0; i < opBytes.Length; i++) { stringBuilder.Append(opBytes[i].ToString("x2")); } return stringBuilder.ToString(); } EDIT The string 'password' in the PHP function comes out as "d899d91adf31e0b37e7b99c5d2316ed3f6a999443OZl" in the c# it comes out as: "905d25819d950cf73f629fc346c485c819a3094a6facef08253c4e3a709e17d9ff4ba197"

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  • Refresher on Java classes in separate files

    - by JohnFaig
    I need a refresher on moving classes from one file into two files. My sample code is in one file called "external_class_file_main". The program runs fine and the code is shown below: Public class external_class_file_main { public static int get_a_random_number (int min, int max) { int n; n = (int)(Math.random() * (max - min +1)) + min; return (n); } public static void main(String[] args) { int r; System.out.println("Program starting..."); r = get_a_random_number (1, 5); System.out.println("random number = " + r); System.out.println("Program ending..."); } } I move the get_a_random_number class to a separate file called "external_class_file". When I do this, I get the following error: Exception in thread "main" java.lang.Error: Unresolved compilation problem: The method get_a_random_number(int, int) is undefined for the type external_class_file_main at external_class_file_main.main(external_class_file_main.java:20) The "external_class_file_main" now contains: public class external_class_file_main { public static void main(String[] args) { int r; System.out.println("Program starting..."); r = get_a_random_number (1, 5); System.out.println("random number = " + r); System.out.println("Program ending..."); } } The "external_class_file" now contains: public class external_class_file { public static int get_a_random_number (int min, int max) { int n; n = (int)(Math.random() * (max - min +1)) + min; return (n); } }

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  • Dice Emulation - ImageView

    - by Michelle Harris
    I am trying to emulate dice using ImageView. When I click the button, nothing seems to happen. I have hard coded this example to replace the image with imageView4 for debugging purposes (I was making sure the random wasn't fail). Can anyone point out what I am doing wrong? I am new to Java, Eclipse and Android so I'm sure I've probably made more than one mistake. Java: import java.util.Random; import android.app.Activity; import android.os.Bundle; import android.view.View; import android.widget.ArrayAdapter; import android.widget.ImageView; import android.widget.Spinner; import android.widget.Toast; public class Yahtzee4Activity extends Activity { /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); Spinner s = (Spinner) findViewById(R.id.spinner); ArrayAdapter adapter = ArrayAdapter.createFromResource( this, R.array.score_types, android.R.layout.simple_spinner_dropdown_item); adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item); s.setAdapter(adapter); } public void onMyButtonClick(View view) { ImageView imageView1 = new ImageView(this); Random rand = new Random(); int rndInt = 4; //rand.nextInt(6) + 1; // n = the number of images, that start at index 1 String imgName = "die" + rndInt; int id = getResources().getIdentifier(imgName, "drawable", getPackageName()); imageView1.setImageResource(id); } } XML for the button: <Button android:id="@+id/button_roll" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/roll" android:onClick="onMyButtonClick" />

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  • java label setText and setBounds clashing?

    - by java
    I would like to have a JLabel changint color to a random one, while jumping to a random position, and while changing its text. but the setText and setBounds seem to clash and i don't know why. if you comment out the setText then the setBounds will work, but they won't work together. import java.awt.*; import java.util.*; import javax.swing.*; public class test2 extends JFrame { private static JLabel label = new JLabel("0"); private static Random gen = new Random(); public test2() { JPanel panel = new JPanel(); panel.add(label); this.add(panel); } public static void move() { for (int i = 0; i < 10; i++) { int n = gen.nextInt(254)+1; int nn = gen.nextInt(254)+1; int nnn = gen.nextInt(254)+1; label.setText(""+i); //the setBounds command will not work with the setText command. why? label.setBounds(n*2, nn*2, 20, 20); label.setForeground(new Color(n, nn, nnn)); try { Thread.sleep(200); } catch (Exception e) {} } } public static void main(String[] args) { test2 frame = new test2(); frame.setVisible(true); frame.setSize(600, 600); frame.setResizable(true); frame.setLocationRelativeTo(null); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); move(); } }

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  • class selector refuses after append to body

    - by supersize
    I'm appending loads of divs in a wrapper: var cubes = [], allCubes = '', for(var i = 0; i < 380; i++) { var randomleft = Math.floor(Math.random()*Math.floor(Math.random()*1000)), randomtop = Math.floor(Math.random()*Math.floor(Math.random()*1000)); allCubes += '<div id="cube'+i+'" class="cube" style="position: absolute; border: 2px #000 solid; left: '+randomleft+'px; top: '+randomtop+'px; width: 9px; height: 9px; z-index: -1"></div>'; } $('#wrapper').append(allCubes); // performance for(var i = 0; i < 380; i++) { cubes.push($('#cube'+i)); } and then I would like to make them all draggable with jQueryUI and log their current position. var allc = $('.cube'); allc.draggable().on('mouseup', function(i) { allc.each(function() { var nleft = $(this).offset().left; var ntop = $(this).offset().top; console.log('cubes['+i+'].animate({ left:'+nleft+',top:'+ntop+'})'); }); }); Unfortunenately it does not work. They are neither draggable nor there comes up a log. Thanks

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  • Counting the number of occurrences of characters in an array

    - by Anthony Pittelli
    This is what I have but it is not working, this is confusing for me. If you scroll down I commented on someones post the exact problem I am having and what I am trying to do. I was thinking maybe the problem is my code to generate the random characters: public void add (char fromChar, char toChar){ Random r = new Random(); //creates a random object int randInt; for (int i=0; i<charArray.length; i++){ randInt = r.nextInt((toChar-fromChar) +1); charArray[i] = (char) randInt; //casts these integers as characters } }//end add public int[] countLetters() { int[] count = new int[26]; char current; for (int b = 0; b <= 26; b++) { for (int i = 97; i <= 123; i++) { char a = (char) i; for (int ch = 0; ch < charArray.length; ch++) { current = charArray[ch]; if (current == a) { count[b]++; } } } } return count; }

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  • problem after uploading file to web host

    - by Alexander
    I have a .xml file in my App_Data folder, I can access it fine in my localhost, however after uploading it to my webhost I got the following: ASP.NET is not authorized to access the requested resource. Consider granting access rights to the resource to the ASP.NET request identity. ASP.NET has a base process identity (typically {MACHINE}\ASPNET on IIS 5 or Network Service on IIS 6) that is used if the application is not impersonating. If the application is impersonating via , the identity will be the anonymous user (typically IUSR_MACHINENAME) or the authenticated request user. To grant ASP.NET access to a file, right-click the file in Explorer, choose "Properties" and select the Security tab. Click "Add" to add the appropriate user or group. Highlight the ASP.NET account, and check the boxes for the desired access. So who should I grant access to read? There's 3 user in my web host and all seems to have read access set to them.. one is NETWORK_SERVICE, IUSR_MACHINENAME and my user. So what is wrong?

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  • Storing multiple discarded datas in a single variable using a string accumulator

    - by dan
    For an assignment for my intro to python course, we are to write a program that generates 100 sets of x,y coordinates. X must be a float between -100.0 and 100.0 inclusive, but not 0. Y is Y = ((1/x) * 3070) but if the absolute value of Y is greater than 100, both numbers must be discarded (BUT STORED) and another set generated. The results must be displayed in a table, and then after the table, the discarded results must be shown. The teacher said we should use a "string accumulator" to store the discarded data. This is what I have so far, and I'm stuck at storing the discarded data. # import random.py import random # import math.py import math # define main def main(): x = random.uniform(-100.0, 100.0) while x == 0: x = random.uniform(-100.0, 100.0) y = ((1/x) * 3070) while math.fabs(y) > 100: xDiscarded = yDiscarded = y = ((1/x) * 3070) As you can see, I run into the problem of when abs(y) 100, I'm not too sure how to store the discarded data and let it accumulate every time abs(y) 100. I'm cool with the data being stored as "351.2, 231.1, 152.2" I just don't know how to turn the variable into a string and store it. We haven't learned arrays yet so I can't do that. Any help would be much appreciated. Thanks!

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  • Question about permute-by-sorting

    - by davit-datuashvili
    In the book "Introduction to Algorithms", second edition, there is the following problem: Suppose we have some array: int a[] = {1,2,3,4} and some random priorities array: P = {36,3,97,19} and the goal is to permute the array a randomly using this priorities array. This is the pseudo code: PERMUTE-BY-SORTING (A) 1 n ? length[A] 2 for i ? 1 to n 3 do P[i] = RANDOM (1, n 3) 4 sort A, using P as sort keys 5 return A The result should be the permuted array: B={2, 4, 1, 3}; I have written this code: import java.util.*; public class Permute { public static void main (String[] args) { Random r = new Random(); int a[] = new int[] {1,2,3,4}; int n = a.length; int b[] = new int[a.length]; int p[] = new int[a.length]; for (int i=0; i<p.length; i++) { p[i] = r.nextInt(n*n*n) + 1; } // for (int i=0;i<p.length;i++){ // System.out.println(p[i]); //} } } How do I continue?

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  • loop prematurely quitting

    - by Nick Gibson
    This loop works fine but prematurely quits at times. I set a piece of code in it so that I can view the random number. It only closes prematurely when the random number is equal to the highest numbered question the user inputs (Example...a user wants 10 questions, if the random number is 10 the program quits.) I have no idea why since i have it set to if(random number <= the number of questions) for ( int loop = 1; loop < loopCount; loop++ ) { aa = r.nextInt ( 10 + 1 ); abc = ( int ) aa; String[] userAnswer = new String[x]; JOptionPane.showMessageDialog ( null, abc ); if ( abc <= x ) { for ( overValue = 1; overValue < forLoop; overValue++ ); { userAnswer[j] = JOptionPane.showInputDialog ( null, "Question " + quesNum + "\n" + questions[abc] + "\n\nA: " + a[abc] + "\nB: " + b[abc] + "\nC: " + c[abc] + "\nD: " + d[abc] ); if ( userAnswer[j].equals ( answers[j] ) ) { JOptionPane.showMessageDialog ( null, "Correct. \nThe Correct Answer is " + answers[abc] ); } else { JOptionPane.showMessageDialog ( null, "Wrong. \n The Correct Answer is " + answers[abc] ); }//else }//for }//if }//for

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  • SQL inner join from field defined table?

    - by Wolftousen
    I have a, currently, a total of 6 tables that are part of this question. The primary table, tableA, contains columns that all the entries in the other 5 tables have in common. The other 5 tables have columns which define the entry in tableA in more detail. For example: TableA ID|Name|Volumn|Weight|Description 0 |T1 |0.4 |0.1 |Random text 1 |R1 |5.3 |25 |Random text TableB ID|Color|Shape 0 |Blue |Sphere TableC ID|Direction|Velocity 1 |North |3.4 (column names are just examples don't take them for what they mean...) The ID field in Table A is unique to all other tables (i.e. TableB will have 0, but TableC will not, nor any other Tables). What I would like to do is select all the fields from TableA and the corresponding (according to ID field) detail Table (TableB-F). What I have currently done and not tested is added a field to TableA so it looks like this: TableA ID|Name|Volumn|Weight|Description|Table 0 |T1 |0.4 |0.1 |Random text|TableB 1 |R1 |5.3 |25 |Random text|TableC I have a few questions about this: 1.Is it proper to do such a thing to TableA, as foreign keys wont work in this situation since they all need to link to different tables? 2.If this is proper, would the SQL query look like this (ID would be input by the user)? SELECT * FROM TableA AS a INNER JOIN a.Table AS t ON a.ID = ID; 3.Is there a better way to do this? Thanks for the help.

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  • A Guided Tour of Complexity

    - by JoshReuben
    I just re-read Complexity – A Guided Tour by Melanie Mitchell , protégé of Douglas Hofstadter ( author of “Gödel, Escher, Bach”) http://www.amazon.com/Complexity-Guided-Tour-Melanie-Mitchell/dp/0199798109/ref=sr_1_1?ie=UTF8&qid=1339744329&sr=8-1 here are some notes and links:   Evolved from Cybernetics, General Systems Theory, Synergetics some interesting transdisciplinary fields to investigate: Chaos Theory - http://en.wikipedia.org/wiki/Chaos_theory – small differences in initial conditions (such as those due to rounding errors in numerical computation) yield widely diverging outcomes for chaotic systems, rendering long-term prediction impossible. System Dynamics / Cybernetics - http://en.wikipedia.org/wiki/System_Dynamics – study of how feedback changes system behavior Network Theory - http://en.wikipedia.org/wiki/Network_theory – leverage Graph Theory to analyze symmetric  / asymmetric relations between discrete objects Algebraic Topology - http://en.wikipedia.org/wiki/Algebraic_topology – leverage abstract algebra to analyze topological spaces There are limits to deterministic systems & to computation. Chaos Theory definitely applies to training an ANN (artificial neural network) – different weights will emerge depending upon the random selection of the training set. In recursive Non-Linear systems http://en.wikipedia.org/wiki/Nonlinear_system – output is not directly inferable from input. E.g. a Logistic map: Xt+1 = R Xt(1-Xt) Different types of bifurcations, attractor states and oscillations may occur – e.g. a Lorenz Attractor http://en.wikipedia.org/wiki/Lorenz_system Feigenbaum Constants http://en.wikipedia.org/wiki/Feigenbaum_constants express ratios in a bifurcation diagram for a non-linear map – the convergent limit of R (the rate of period-doubling bifurcations) is 4.6692016 Maxwell’s Demon - http://en.wikipedia.org/wiki/Maxwell%27s_demon - the Second Law of Thermodynamics has only a statistical certainty – the universe (and thus information) tends towards entropy. While any computation can theoretically be done without expending energy, with finite memory, the act of erasing memory is permanent and increases entropy. Life & thought is a counter-example to the universe’s tendency towards entropy. Leo Szilard and later Claude Shannon came up with the Information Theory of Entropy - http://en.wikipedia.org/wiki/Entropy_(information_theory) whereby Shannon entropy quantifies the expected value of a message’s information in bits in order to determine channel capacity and leverage Coding Theory (compression analysis). Ludwig Boltzmann came up with Statistical Mechanics - http://en.wikipedia.org/wiki/Statistical_mechanics – whereby our Newtonian perception of continuous reality is a probabilistic and statistical aggregate of many discrete quantum microstates. This is relevant for Quantum Information Theory http://en.wikipedia.org/wiki/Quantum_information and the Physics of Information - http://en.wikipedia.org/wiki/Physical_information. Hilbert’s Problems http://en.wikipedia.org/wiki/Hilbert's_problems pondered whether mathematics is complete, consistent, and decidable (the Decision Problem – http://en.wikipedia.org/wiki/Entscheidungsproblem – is there always an algorithm that can determine whether a statement is true).  Godel’s Incompleteness Theorems http://en.wikipedia.org/wiki/G%C3%B6del's_incompleteness_theorems  proved that mathematics cannot be both complete and consistent (e.g. “This statement is not provable”). Turing through the use of Turing Machines (http://en.wikipedia.org/wiki/Turing_machine symbol processors that can prove mathematical statements) and Universal Turing Machines (http://en.wikipedia.org/wiki/Universal_Turing_machine Turing Machines that can emulate other any Turing Machine via accepting programs as well as data as input symbols) that computation is limited by demonstrating the Halting Problem http://en.wikipedia.org/wiki/Halting_problem (is is not possible to know when a program will complete – you cannot build an infinite loop detector). You may be used to thinking of 1 / 2 / 3 dimensional systems, but Fractal http://en.wikipedia.org/wiki/Fractal systems are defined by self-similarity & have non-integer Hausdorff Dimensions !!!  http://en.wikipedia.org/wiki/List_of_fractals_by_Hausdorff_dimension – the fractal dimension quantifies the number of copies of a self similar object at each level of detail – eg Koch Snowflake - http://en.wikipedia.org/wiki/Koch_snowflake Definitions of complexity: size, Shannon entropy, Algorithmic Information Content (http://en.wikipedia.org/wiki/Algorithmic_information_theory - size of shortest program that can generate a description of an object) Logical depth (amount of info processed), thermodynamic depth (resources required). Complexity is statistical and fractal. John Von Neumann’s other machine was the Self-Reproducing Automaton http://en.wikipedia.org/wiki/Self-replicating_machine  . Cellular Automata http://en.wikipedia.org/wiki/Cellular_automaton are alternative form of Universal Turing machine to traditional Von Neumann machines where grid cells are locally synchronized with their neighbors according to a rule. Conway’s Game of Life http://en.wikipedia.org/wiki/Conway's_Game_of_Life demonstrates various emergent constructs such as “Glider Guns” and “Spaceships”. Cellular Automatons are not practical because logical ops require a large number of cells – wasteful & inefficient. There are no compilers or general program languages available for Cellular Automatons (as far as I am aware). Random Boolean Networks http://en.wikipedia.org/wiki/Boolean_network are extensions of cellular automata where nodes are connected at random (not to spatial neighbors) and each node has its own rule –> they demonstrate the emergence of complex  & self organized behavior. Stephen Wolfram’s (creator of Mathematica, so give him the benefit of the doubt) New Kind of Science http://en.wikipedia.org/wiki/A_New_Kind_of_Science proposes the universe may be a discrete Finite State Automata http://en.wikipedia.org/wiki/Finite-state_machine whereby reality emerges from simple rules. I am 2/3 through this book. It is feasible that the universe is quantum discrete at the plank scale and that it computes itself – Digital Physics: http://en.wikipedia.org/wiki/Digital_physics – a simulated reality? Anyway, all behavior is supposedly derived from simple algorithmic rules & falls into 4 patterns: uniform , nested / cyclical, random (Rule 30 http://en.wikipedia.org/wiki/Rule_30) & mixed (Rule 110 - http://en.wikipedia.org/wiki/Rule_110 localized structures – it is this that is interesting). interaction between colliding propagating signal inputs is then information processing. Wolfram proposes the Principle of Computational Equivalence - http://mathworld.wolfram.com/PrincipleofComputationalEquivalence.html - all processes that are not obviously simple can be viewed as computations of equivalent sophistication. Meaning in information may emerge from analogy & conceptual slippages – see the CopyCat program: http://cognitrn.psych.indiana.edu/rgoldsto/courses/concepts/copycat.pdf Scale Free Networks http://en.wikipedia.org/wiki/Scale-free_network have a distribution governed by a Power Law (http://en.wikipedia.org/wiki/Power_law - much more common than Normal Distribution). They are characterized by hubs (resilience to random deletion of nodes), heterogeneity of degree values, self similarity, & small world structure. They grow via preferential attachment http://en.wikipedia.org/wiki/Preferential_attachment – tipping points triggered by positive feedback loops. 2 theories of cascading system failures in complex systems are Self-Organized Criticality http://en.wikipedia.org/wiki/Self-organized_criticality and Highly Optimized Tolerance http://en.wikipedia.org/wiki/Highly_optimized_tolerance. Computational Mechanics http://en.wikipedia.org/wiki/Computational_mechanics – use of computational methods to study phenomena governed by the principles of mechanics. This book is a great intuition pump, but does not cover the more mathematical subject of Computational Complexity Theory – http://en.wikipedia.org/wiki/Computational_complexity_theory I am currently reading this book on this subject: http://www.amazon.com/Computational-Complexity-Christos-H-Papadimitriou/dp/0201530821/ref=pd_sim_b_1   stay tuned for that review!

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  • Code Contracts: Hiding ContractException

    - by DigiMortal
    It’s time to move on and improve my randomizer I wrote for an example of static checking of code contracts. In this posting I will modify contracts and give some explanations about pre-conditions and post-conditions. Also I will show you how to avoid ContractExceptions and how to replace them with your own exceptions. As a first thing let’s take a look at my randomizer. public class Randomizer {     public static int GetRandomFromRange(int min, int max)     {         var rnd = new Random();         return rnd.Next(min, max);     }       public static int GetRandomFromRangeContracted(int min, int max)     {         Contract.Requires(min < max, "Min must be less than max");           var rnd = new Random();         return rnd.Next(min, max);     } } We have some problems here. We need contract for method output and we also need some better exception handling mechanism. As ContractException as type is hidden from us we have to switch from ContractException to some other Exception type that we can catch. Adding post-condition Pre-conditions are contracts for method’s input interface. Read it as follows: pre-conditions make sure that all conditions for method’s successful run are met. Post-conditions are contracts for output interface of method. So, post-conditions are for output arguments and return value. My code misses the post-condition that checks return value. Return value in this case must be greater or equal to minimum value and less or equal to maximum value. To make sure that method can run only the correct value I added call to Contract.Ensures() method. public static int GetRandomFromRangeContracted(int min, int max) {     Contract.Requires(min < max, "Min must be less than max");       Contract.Ensures(         Contract.Result<int>() >= min &&         Contract.Result<int>() <= max,         "Return value is out of range"     );       var rnd = new Random();     return rnd.Next(min, max); } I think that the line I added does not need any further comments. Avoiding ContractException for input interface ContractException lives in hidden namespace and we cannot see it at design time. But it is common exception type for all contract exceptions that we do not switch over to some other type. The case of Contract.Requires() method is simple: we can tell it what kind of exception we need if something goes wrong with contract it ensures. public static int GetRandomFromRangeContracted(int min, int max) {     Contract.Requires<ArgumentOutOfRangeException>(         min < max,         "Min must be less than max"     );       Contract.Ensures(         Contract.Result<int>() >= min &&         Contract.Result<int>() <= max,         "Return value is out of range"     );       var rnd = new Random();     return rnd.Next(min, max); } Now, if we violate the input interface contract giving min value that is not less than max value we get ArgumentOutOfRangeException. Avoiding ContractException for output interface Output interface is more complex to control. We cannot give exception type there and hope that this type of exception will be thrown if something goes wrong. Instead we have to use delegate that gathers information about problem and throws the exception we expect to be thrown. From documentation you can find the following example about the delegate I mentioned. Contract.ContractFailed += (sender, e) => {     e.SetHandled();     e.SetUnwind(); // cause code to abort after event     Assert.Fail(e.FailureKind.ToString() + ":" + e.DebugMessage); }; We can use this delegate to throw the Exception. Let’s move the code to separate method too. Here is our method that uses now ContractException hiding. public static int GetRandomFromRangeContracted(int min, int max) {     Contract.Requires(min < max, "Min must be less than max");       Contract.Ensures(         Contract.Result<int>() >= min &&         Contract.Result<int>() <= max,         "Return value is out of range"     );     Contract.ContractFailed += Contract_ContractFailed;       var rnd = new Random();     return rnd.Next(min, max)+1000; } And here is the delegate that creates exception. public static void Contract_ContractFailed(object sender,     ContractFailedEventArgs e) {     e.SetHandled();     e.SetUnwind();       throw new Exception(e.FailureKind.ToString() + ":" + e.Message); } Basically we can do in this delegate whatever we like to do with output interface errors. We can even introduce our own contract exception type. As you can see later then ContractFailed event is very useful at unit testing.

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  • Cost Comparison Hard Disk Drive to Solid State Drive on Price per Gigabyte - dispelling a myth!

    - by tonyrogerson
    It is often said that Hard Disk Drive storage is significantly cheaper per GiByte than Solid State Devices – this is wholly inaccurate within the database space. People need to look at the cost of the complete solution and not just a single component part in isolation to what is really required to meet the business requirement. Buying a single Hitachi Ultrastar 600GB 3.5” SAS 15Krpm hard disk drive will cost approximately £239.60 (http://scan.co.uk, 22nd March 2012) compared to an OCZ 600GB Z-Drive R4 CM84 PCIe costing £2,316.54 (http://scan.co.uk, 22nd March 2012); I’ve not included FusionIO ioDrive because there is no public pricing available for it – something I never understand and personally when companies do this I immediately think what are they hiding, luckily in FusionIO’s case the product is proven though is expensive compared to OCZ enterprise offerings. On the face of it the single 15Krpm hard disk has a price per GB of £0.39, the SSD £3.86; this is what you will see in the press and this is what sales people will use in comparing the two technologies – do not be fooled by this bullshit people! What is the requirement? The requirement is the database will have a static size of 400GB kept static through archiving so growth and trim will balance the database size, the client requires resilience, there will be several hundred call centre staff querying the database where queries will read a small amount of data but there will be no hot spot in the data so the randomness will come across the entire 400GB of the database, estimates predict that the IOps required will be approximately 4,000IOps at peak times, because it’s a call centre system the IO latency is important and must remain below 5ms per IO. The balance between read and write is 70% read, 30% write. The requirement is now defined and we have three of the most important pieces of the puzzle – space required, estimated IOps and maximum latency per IO. Something to consider with regard SQL Server; write activity requires synchronous IO to the storage media specifically the transaction log; that means the write thread will wait until the IO is completed and hardened off until the thread can continue execution, the requirement has stated that 30% of the system activity will be write so we can expect a high amount of synchronous activity. The hardware solution needs to be defined; two possible solutions: hard disk or solid state based; the real question now is how many hard disks are required to achieve the IO throughput, the latency and resilience, ditto for the solid state. Hard Drive solution On a test on an HP DL380, P410i controller using IOMeter against a single 15Krpm 146GB SAS drive, the throughput given on a transfer size of 8KiB against a 40GiB file on a freshly formatted disk where the partition is the only partition on the disk thus the 40GiB file is on the outer edge of the drive so more sectors can be read before head movement is required: For 100% sequential IO at a queue depth of 16 with 8 worker threads 43,537 IOps at an average latency of 2.93ms (340 MiB/s), for 100% random IO at the same queue depth and worker threads 3,733 IOps at an average latency of 34.06ms (34 MiB/s). The same test was done on the same disk but the test file was 130GiB: For 100% sequential IO at a queue depth of 16 with 8 worker threads 43,537 IOps at an average latency of 2.93ms (340 MiB/s), for 100% random IO at the same queue depth and worker threads 528 IOps at an average latency of 217.49ms (4 MiB/s). From the result it is clear random performance gets worse as the disk fills up – I’m currently writing an article on short stroking which will cover this in detail. Given the work load is random in nature looking at the random performance of the single drive when only 40 GiB of the 146 GB is used gives near the IOps required but the latency is way out. Luckily I have tested 6 x 15Krpm 146GB SAS 15Krpm drives in a RAID 0 using the same test methodology, for the same test above on a 130 GiB for each drive added the performance boost is near linear, for each drive added throughput goes up by 5 MiB/sec, IOps by 700 IOps and latency reducing nearly 50% per drive added (172 ms, 94 ms, 65 ms, 47 ms, 37 ms, 30 ms). This is because the same 130GiB is spread out more as you add drives 130 / 1, 130 / 2, 130 / 3 etc. so implicit short stroking is occurring because there is less file on each drive so less head movement required. The best latency is still 30 ms but we have the IOps required now, but that’s on a 130GiB file and not the 400GiB we need. Some reality check here: a) the drive randomness is more likely to be 50/50 and not a full 100% but the above has highlighted the effect randomness has on the drive and the more a drive fills with data the worse the effect. For argument sake let us assume that for the given workload we need 8 disks to do the job, for resilience reasons we will need 16 because we need to RAID 1+0 them in order to get the throughput and the resilience, RAID 5 would degrade performance. Cost for hard drives: 16 x £239.60 = £3,833.60 For the hard drives we will need disk controllers and a separate external disk array because the likelihood is that the server itself won’t take the drives, a quick spec off DELL for a PowerVault MD1220 which gives the dual pathing with 16 disks 146GB 15Krpm 2.5” disks is priced at £7,438.00, note its probably more once we had two controller cards to sit in the server in, racking etc. Minimum cost taking the DELL quote as an example is therefore: {Cost of Hardware} / {Storage Required} £7,438.60 / 400 = £18.595 per GB £18.59 per GiB is a far cry from the £0.39 we had been told by the salesman and the myth. Yes, the storage array is composed of 16 x 146 disks in RAID 10 (therefore 8 usable) giving an effective usable storage availability of 1168GB but the actual storage requirement is only 400 and the extra disks have had to be purchased to get the  IOps up. Solid State Drive solution A single card significantly exceeds the IOps and latency required, for resilience two will be required. ( £2,316.54 * 2 ) / 400 = £11.58 per GB With the SSD solution only two PCIe sockets are required, no external disk units, no additional controllers, no redundant controllers etc. Conclusion I hope by showing you an example that the myth that hard disk drives are cheaper per GiB than Solid State has now been dispelled - £11.58 per GB for SSD compared to £18.59 for Hard Disk. I’ve not even touched on the running costs, compare the costs of running 18 hard disks, that’s a lot of heat and power compared to two PCIe cards!Just a quick note: I've left a fair amount of information out due to this being a blog! If in doubt, email me :)I'll also deal with the myth that SSD's wear out at a later date as well - that's just way over done still, yes, 5 years ago, but now - no.

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  • Remote Desktop Connection Only Works One Way

    - by advocate
    I can't get my desktop to connect to my laptop through remote desktop connection. Unfortunately I can only get my laptop to connect to my desktop (quite useless). Desktop: Windows 7 Ultimate 64 Bit SP1 Windows firewall is off for all 3 profiles (domain / private / public) Remote desktop connection is installed and set to allow all connections Under running services is: Running Remote Desktop Configuration Running Remote Desktop Services Running Remote Desktop Services UserMode Port Redirector Running Remote Procedure Call (RPC) Stopped Remote Access Auto Connection Manager Stopped Remote Access Connection Manager Stopped Remote Procedure Call (RPC) Locator Stopped Remote Registry Stopped Routing and Remote Access Stopped Windows Remote Management (WS-Management) Laptop: Windows 7 Home Premium 64 Bit SP1 Windows firewall is off for all3 profiles (domain / private / public) Remote desktop connection is installed and set to 'Allow Remote Assistance connections to this computer' Under running services is: Running Remote Procedure Call (RPC) Stopped Remote Access Auto Connection Manager Stopped Remote Access Connection Manager Stopped Remote Desktop Configuration Stopped Remote Desktop Services Stopped Remote Procedure Call (RPC) Locator Stopped Remote Registry Stopped Routing and Remote Access Stopped Windows Remote Management (WS-Management) It should be noted that the Laptop that I'm trying to connect to is an Alienware and might be running some wonky Dell settings. Also, the settings are slightly different for remote desktop connection as it's a Home edition of Windows and not Ultimate like my desktop. Finally, both computers are on the same Homegroup so that RDC can be accessed by one click through the network section of Windows. They're also on the same workgroup, MSHOME, just to see if that helps.

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  • ubuntu 9.10 cups server cupsd.conf

    - by aaron
    i have a cups server running on ubuntu 9.10 on my home network. right now i can access it at 192.168.1.101:631, but when i try to access it at myservername.local:631 i get a 400 Bad Request. here's the relevant section from my current cupsd.conf: ServerName 192.168.1.101 # Only listen for connections from the local machine. Listen localhost:631 Listen /var/run/cups/cups.sock # any of the below 'Listen' directives all yield the same result Listen 192.168.1.101:631 #Listen *:631 #Listen myservername.local:631 # Show shared printers on the local network. Browsing On BrowseOrder allow,deny BrowseAllow all BrowseLocalProtocols CUPS dnssd BrowseAddress 192.168.1.255 # Default authentication type, when authentication is required... DefaultAuthType Basic # Restrict access to the server... <Location /> Order deny,allow Deny from All Allow from 127.0.0.1 Allow from 192.168.1.* </Location> # Restrict access to the admin pages... <Location /admin> Order deny,allow Deny from All #Allow from 127.0.0.1 #Allow from 192.168.1.* </Location> # Restrict access to configuration files... <Location /admin/conf> AuthType Default Require user @SYSTEM Order deny,allow Deny from All #Allow from 127.0.0.1 #Allow from 192.168.1.* </Location> i get the following in /var/log/cups/error_log: E [03/Jan/2010:18:33:41 -0600] Request from "192.168.1.100" using invalid Host: field "myservername.local:631" what do i need to do to be able to access the cups server at both 192.168.1.101:631 and myservername.local:631?

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  • Permissions won't cascade more than 1 level

    - by Jovin_
    Running Windows Small Business Server 2011 I have a file structure with a lot of sub folders (sometimes 5-6 levels deep). I have created access groups to grant access to my users, and also deny groups to deny access to others. X Access & X Deny. These allow or deny access to a mapped network drive X: On the server I put in the groups with Full Control Allow for X Access and Full Control Deny for X Deny, I also tick the box "Apple these permissions to objects and/or containers within this container only" and have ensured that "Apply to:" is "This folder, subfolders and files". But for some reason the permissions will only apply to the next level of folders & files. ex. structure: X: Folder 1 Folder 1a Folder 2 Folder 2a If I apply the permissions to X: it'll only go to Folder 1 & 2, not 1a and 2a, I then need to manually apply the permissions to these too. Is this working as intended or am I doing something wrong?

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  • Can't reset Windows 7 Registry permissions.

    - by n10i
    hi all, i am trying to reset win 7 registry permissions using secedit /configure /cfg %windir%\inf\defltbase.inf /db defltbase.sdb /verbose /areas REGKEYS But i am receiving the following error: An extended error has occurred. The task has completed with an error. See log %windir%\security\logs\scesrv.log for detail info. The content Of the log file: ------------------------------------------- Friday, April 16, 2010 1:50:43 PM ----Configuration engine was initialized successfully.---- ----Reading Configuration Template info... ----Configure 64-bit Registry Keys... Configure users.default. Warning 5: Access is denied. Error taking ownership of users.default\software\SetID. Warning 5: Access is denied. Error opening users.default\software\SetID. Warning 5: Access is denied. Error setting security on users.default\software\SetID. Configure machine\software. Warning 5: Access is denied. Error setting security on machine\software. Warning 1336: The access control list (ACL) structure is invalid. Error setting security on machine\software\Macrovision. Configuration of Registry Keys was completed with one or more errors. ----Configure 32-bit Registry Keys... Configure machine\software. Warning 1336: The access control list (ACL) structure is invalid. Error setting security on machine\software\Audible. Configuration of Registry Keys was completed with one or more errors. ----Un-initialize configuration engine... plz! help me guys!

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  • nginx not serving admin static files?

    - by toto_tico
    First, I want to clarify that this error is just for the admin static files. This means my problem is specific just to the static files that corresponds to the Django admin. The rest of the static files are working perfect. Basically my problem is that for some reason I cannot access those admin static files with the ngix server. It works perfect with the micro server of Django and the collect static is doing its job. This means it is putting the files on the expected place in the static folder. The urls are correct but I cannot even access the admin static files directly, but the others I can. So, for example, I am able to access this url (copying it in the browser): myserver.com:8080/static/css/base/base.css but i am not able to access this other url (copying it in the browser): myserver.com:8080/static/admin/css/admin.css I also tried to copy the admin/ directory structure into other_admin_directory_name/. Then I can access myserver.com:8080/static/other_admin_directory_name/css/admin.css Then, it works. So, I checked permissions and everything is fine. I tried to change ADMIN_MEDIA_PREFIX = '/static/admin/' to ADMIN_MEDIA_PREFIX = '/static/other_admin_directory_name/', it doesn't work. This a mistery in itself that I am exploring but still no luck. Finally, and it seems to be an important clue: I tried to copy the admin/ directory structure into admin_and_then_any_suffix/. Then I cannot access myserver.com:8080/static/admin_and_then_any_suffix//css/admin.css So, if the name of the directory starts with admin (for example administration or admin2) it doesn't work. * added thanks to sarnold observation ** the problem seems to be in the nginx configuration file /etc/nginx/sites-available/mysite location /static/admin { alias /home/vl3/.virtualenvs/vl3/lib/python2.7/site-packages/django/contrib/admin/media/; }

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  • Virtual Lan on the Cloud -- Help Confirm my understanding?

    - by marfarma
    [Note: Tried to post this over at ServerFault, but I don't have enough 'points' for more than one link. Powers that be, move this question over there.] Please give this a quick read and let me know if I'm missing something before I start trying to make this work. I'm not a systems admin professional, and I'd hate to end up banging my head into the wall if I can avoid it. Goals: Create a 'road-warrior' capable star shaped virtual LAN for consultants who spend the majority of their time on client sites, and who's firm has no physical network or servers. Enable CIFS access to a cloud-server based installation of Alfresco Allow Eventual implementation of some form of single-sign-on ( OpenLDAP server ) access to Alfresco and other server applications implemented in the future Given: All Servers will live in the public internet cloud (Rackspace Cloud Servers) OpenVPN Server will be a Linux disto, probably Ubuntu 9.x, installed on same server as Alfresco (at least to start) Staff will access server applications and resources from client sites, hotels, trains, planes, coffee shops or their homes over various ISP, using their company laptops or personal home desktops. Based on my Research thus far, to accomplish this, I'll need: OpenVPN with Bridging Enabled to create a star shaped "virtual" LAN http://openvpn.net/index.php/open-source/documentation/miscellaneous/76-ethernet-bridging.html A Road Warrior Network Configuration, as described in this Shorewall article (lower down the page) http://www.shorewall.net/OPENVPN.html Configure bridge addressesing (probably DHCP) http://openvpn.net/index.php/open-source/faq.html#bridge-addressing Configure CIFS / Samba to accept VPN IP address http://serverfault.com/questions/137933/howto-access-samba-share-over-vpn-tunnel Set up Client software, with keys configured for access (potentially through a OpenVPN-Sa client portal) http://www.openvpn.net/index.php/access-server/download-openvpn-as/221-installation-overview.html

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  • Caused by: java.net.SocketException: Software caused connection abort: socket write error

    - by jrishere
    I running JSP on Oracle 11g, Weblogic 10.3.4. I have 2 managed server and a oracle admin server installed. I am encountering an error where intermittently the log file of the 2 managed server and admin server will show java.net.SocketException: Software caused connection abort: socket write error. The application can run for 2 days without showing this error or it can show up a few times in a day. The server load are similar everday. When this error is been encountered, the server will just stop accepting connections and will not be able to access the application. Even if I try to access the application through localhost, I will not be able to access the JSP pages and a 503 http status is shown but then I am able to access the static HTML page. I will not be able to access the Oracle 11g Weblogic admin console page. When I take a look at admin server log, it shows that the managed servers are disconnected from the admin server and vice versa. Magically the application is able to recover by its own and the application is able to access again or I need to restart the server as restarting the service of the application does not work. The FTP connections that the application is connected to are closed as well. I am able to ping to telnet to the server port. The event log doesn't seem to be leaving any information. We did run wireshark to see the packet traffic and it seems that the application port is sending a RST, ACK packet to the load balancer. Any kind help will greatly be appreciated. Should you need more info, feel free to ask me. Thanks in advance.

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  • Git clone/push/pull - where's that username comes from?

    - by Kuroki Kaze
    I've set up gitosis and able to pull/push through ssh. Gitosis is installed on Debian Lenny server, I'm using git from windows machine (msysgit). The strange thing, if I enable loglevel = DEBUG in gitosis.conf, I see something like this when doing any actions with gitosis server: D:\Kaze\source\test-project>git pull origin master DEBUG:gitosis.serve.main:Got command "git-upload-pack 'test_project.git'" DEBUG:gitosis.access.haveAccess:Access check for '[email protected]' as 'writable' on 'test_project.git'... DEBUG:gitosis.access.haveAccess:Stripping .git suffix from 'test_project.git', new value 'test_project' DEBUG:gitosis.group.getMembership:found '[email protected]' in 'test' DEBUG:gitosis.access.haveAccess:Access ok for '[email protected]' as 'writable' on 'test_project' DEBUG:gitosis.access.haveAccess:Using prefix 'repositories' for 'test_project' DEBUG:gitosis.serve.main:Serving git-upload-pack 'repositories/test_project.git' From 192.168.175.128:test_project * branch master -> FETCH_HEAD Already up-to-date. Question is: why am I *[email protected]? This email is in global user.email config variable, too. Yesterday, when the gitosis was installed, it seen me as kaze@KAZE, this is the name under which I was added to gitosis-admin group (and it worked). But today git (or gitosis) started to see me as [email protected]. This is true for all repositories I push or clone. I had to add this address to gitosis.conf directly on server to be able to edit configs again (it worked). There is 2 public keys in keydir: [email protected] and [email protected], their content is identical and they have kaze@KAZE at end. Origin URL looks like git@lennyserver:test_project. Now, the question is - why Git (or gitosis) suddenly decided to call me by email instead of name@machinename? I've changed a couple things trying to set up Gitosis (updated git on server to 1.6.0 for example), but maybe I broke something in my local git installation?

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  • Bypass proxy authentication [closed]

    - by Diego Queiroz
    My scenario: My network has a proxy that requires interative authentication. When I access any URL, an username and password is requested to enable navigation. I do have a valid username/password (this means I have permissions to access external content). I do not have access to the proxy server (any change to the proxy server is not an option). What I need: I need to bypass the interative authentication process and make it an automated authentication process. What I do NOT need/want: I do not need/want to hack the network. I do not need/want to access unauthorized content. In other words, I just need to find a way to "save" my password in the computer (security is not a problem) to allow application that does not support this kind of interative authentication to access the internet (like non-browser software that also uses HTTP port). My guess: My guess is to develop a new proxy server that will run in the local machine (eg, a proxy for the network proxy). This proxy server will access my network proxy, authenticate and forward the content. Of course this is a last resort. I prefer to not need to develop a proxy server. Does someone know other solution? (any operating system)

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