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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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  • 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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  • 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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  • 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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  • 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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  • JQuery UI Autocomplete TextBox in ASP.NET C# with ArrayList

    - by Avishek Kumar
    hello, I am a asp.net coder looking forward to the "easiest tutorial on the planet" to understand how to make a JQuery Autocomplete in ASP.NET c# with ArrayList which not just me but every .net idiot can understand for once and forever as im tired of looking up so many tutorials which teach me nothing. Im referring to this http://jqueryui.com/demos/autocomplete/ library for autocomplete thing. Here is what exactly i want: 1ASP.NET text-box which has autocomplete added to it. 2It will fetch records from "search.aspx?q=searchtext" and get back maximum of 5 matching results in C# ArrayList Format 3Show those 5 matching autocomplete records below text-box as it does in the jquery UI demo page 4Keep doing the autocomplete work for every new Textvalue/changed value in Text-box Here is "what i don't want to see" in my help example: 1JSON, 2XML 3.ASMX, LINQ, Theories of Book and all weired stuff So let me see who actually knows the best code for helping me. I would be thankful to the best ASP.NET coder who helps me out.

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  • PHP correct indentation?

    - by brainle55
    I'm a beginner PHP coder, recently I've been told I indent my code not correctly. They say this is wrong: if($something) { do_something(); } else { something_more(); and_more(); } While this is right? if($something) { do_something(); } else { something_more(); and_more(); } Really? I am willing to become opensource coder in nearest future so that's why I'm asking how to write code in a good way.

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  • Why does my UITableView change from UITableViewStyleGrouped to UITableViewStylePlain

    - by casper
    My application has a view controller that extends UITableViewController. The initialization method looks like this: - (id)initWithCoder:(NSCoder*)coder { if (self = [super initWithCoder:coder]) { self.tableView = [[UITableView alloc] initWithFrame:self.tableView.frame style:UITableViewStyleGrouped]; } return self; } When the view is initially loaded, it's displayed as UITableViewStyleGrouped. However, if my app ever receives a low memory warning, the above view changes to UITableViewStylePlain. There is no associated xib file with the View/Controller. The viewDidUnload and didReceiveMemoryWarning methods are straightforward: - (void)didReceiveMemoryWarning { // Releases the view if it doesn't have a superview. [super didReceiveMemoryWarning]; // Release any cached data, images, etc that aren't in use. } - (void)viewDidUnload { // Release any retained subviews of the main view. // e.g. self.myOutlet = nil; } My question is, why does the table style change when I receive a memory warning?

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  • Updates to NSDictionary attribute in CoreData not saving

    - by sfkaos
    I have created an Entity in CoreData that includes a Transformable attribute type implemented as an NSDictionary. The NSDictionary attribute only contains values of a custom class. The properties of the custom class are all of type NSString. The custom class complies with NSCoding implementing: -(void)encodeWithCoder:(NSCoder*)coder; -(id)initWithCoder:(NSCoder *)coder When saving the Entity for the first time all attributes including the Transformable (NSDictionary) type are properly saved in the DB. When the same Entity is fetched from the DB and updated (including the Transformable attribute) it seems to be updated properly. However, when the app is closed and then reopened fetching the Entity does not show the updated Transformable attribute-type though the rest of the attributes of type NSDate and NSString are up-to-date. The Transformable attribute is the original saved value not the updated value. Is this a problem with KVO or am I missing something else when trying to save an NSDictionary filled with a custom class to CoreData?

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  • Following PHP coding of Wisdom

    - by justjoe
    i read some wisdom like this : Programmers are encouraged to be careful when using by-reference variables since they can negatively affect the readability and maintainability of the code. i make my own solution, such as give suffix such as _ref in every by-reference variables. so, if i have a variable named as $files_in_root, then i will add suffix and changes it name into $files_in_root_ref. As far my knowledge goes, this is a good solution. So, here come the question Is there any best-practice on choosing suffix for by-reference variable in PHP coder world ? Or do you have any ? In general, how do we sustain readability and maintainability on PHP project with more then 3000 line of code ? I hope PHP coder world has unwritten aggrement for first question, cause it will help spot a pattern on any source code.

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  • Question about rights for svn

    - by diadiora
    I have a web application written in asp.net mvc. I have in MyApp.Web assembly the list of views and and the content files(images, scripts, css, and so on). In MyApp.WebBase I have the rest of fonctionality(Controllers, domain(entities, repositories, services)). Now the question is the following: I want to give to third party html coder access only to MyApp.Web source code in order he to be able to compile the application locally and see the results. By other hand the developer team shoul have access to full source code. The problem is that in order the html coder to be able to compile the application locally he need in his project the references to the MyApp.WebBase.dll Can anyone help me? Thanks.

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  • openGL ES retina support

    - by Bryan
    I'm trying to get the avTouch sample code app to run on the retina display. Has anyone done this? In the CALevelMeter class, I've tried the following: - (id)initWithCoder:(NSCoder *)coder { if (self = [super initWithCoder:coder]) { CGFloat f = self.contentScaleFactor; if ([self respondsToSelector:@selector(contentScaleFactor)]) { self.contentScaleFactor = [[UIScreen mainScreen] scale]; } f = self.contentScaleFactor; _showsPeaks = YES; _channelNumbers = [[NSArray alloc] initWithObjects:[NSNumber numberWithInt:0], nil]; _vertical = NO; _useGL = YES; _meterTable = new MeterTable(kMinDBvalue); [self layoutSubLevelMeters]; [self registerForBackgroundNotifications]; } return self; } and it sets the contentScaleFactor to "2". Great, that was expected. But then in the layoutSubviews, CALevelMeter frame is still 1/2 of what it should be. Any ideas?

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  • Grouped UITableView's cell separator missing when setting backgroundView with an image

    - by Howard Spear
    I have a grouped UITableView with a custom UITableViewCell class and I am adding a custom background image to each cell. However, when I do this, the cell's separator is not visible. If simply switch the table style to Plain instead of Grouped, the separator is showing up. I need the grouped table - how do I make the separator show up? Here's my code: @interface MyCustomTableViewCell : UITableViewCell @end @implementation MyCustomTableViewCell // because I'm loading the cell from a xib file - (id)initWithCoder:(NSCoder *)coder { self = [super initWithCoder:coder]; if (self) { // Create a background image view. self.backgroundView = [[UIImageView alloc] init]; } return self; } // MyViewController - (UITableViewCell *)tableView:(UITableView *)aTableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { // // standard cell dequeue + create cell code here // // // Configure the cell background now // UIImage *backgroundImage = [UIImage imageNamed:@"odd_row.png"]; if (indexPath.row % 2 == 0) { backgroundImage = [UIImage imageNamed:@"even_row.png"]; } UIImageView *backgroundView = (UIImageView *)cell.backgroundView; backgroundView.image = backgroundImage; }

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  • why Observable snapshot observer vector

    - by han14466
    In Observable's notifyObservers method, why does the coder use arrLocal = obs.toArray();? Why does not coder iterate vector directly? Thanks public void notifyObservers(Object arg) { Object[] arrLocal; synchronized (this) { /* We don't want the Observer doing callbacks into * arbitrary code while holding its own Monitor. * The code where we extract each Observable from * the Vector and store the state of the Observer * needs synchronization, but notifying observers * does not (should not). The worst result of any * potential race-condition here is that: * 1) a newly-added Observer will miss a * notification in progress * 2) a recently unregistered Observer will be * wrongly notified when it doesn't care */ if (!changed) return; arrLocal = obs.toArray(); clearChanged(); } for (int i = arrLocal.length-1; i>=0; i--) ((Observer)arrLocal[i]).update(this, arg); }

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  • nagios NRPE: Unable to read output

    - by user555854
    I currently set up a script to restart my http servers + php5 fpm but can't get it to work. I have googled and have found that mostly permissions are the problems of my error but can't figure it out. I start my script using /usr/lib/nagios/plugins/check_nrpe -H bart -c restart_http This is the output in my syslog on the node I want to restart Jun 27 06:29:35 bart nrpe[8926]: Connection from 192.168.133.17 port 25028 Jun 27 06:29:35 bart nrpe[8926]: Host address is in allowed_hosts Jun 27 06:29:35 bart nrpe[8926]: Handling the connection... Jun 27 06:29:35 bart nrpe[8926]: Host is asking for command 'restart_http' to be run... Jun 27 06:29:35 bart nrpe[8926]: Running command: /usr/bin/sudo /usr/lib/nagios/plugins/http-restart Jun 27 06:29:35 bart nrpe[8926]: Command completed with return code 1 and output: Jun 27 06:29:35 bart nrpe[8926]: Return Code: 1, Output: NRPE: Unable to read output Jun 27 06:29:35 bart nrpe[8926]: Connection from 192.168.133.17 closed. If I run the command myself it runs fine (but asks for a password) (nagios user) This are the script permission and the script contents. -rwxrwxrwx 1 nagios nagios 142 Jun 26 21:41 /usr/lib/nagios/plugins/http-restart #!/bin/bash echo "ok" /etc/init.d/nginx stop /etc/init.d/nginx start /etc/init.d/php5-fpm stop /etc/init.d/php5-fpm start echo "done" I also added this line to visudo nagios ALL=(ALL) NOPASSWD: /usr/lib/nagios/plugins/ My local nagios nrpe.cfg ############################################################################# # Sample NRPE Config File # Written by: Ethan Galstad ([email protected]) # # # NOTES: # This is a sample configuration file for the NRPE daemon. It needs to be # located on the remote host that is running the NRPE daemon, not the host # from which the check_nrpe client is being executed. ############################################################################# # LOG FACILITY # The syslog facility that should be used for logging purposes. log_facility=daemon # PID FILE # The name of the file in which the NRPE daemon should write it's process ID # number. The file is only written if the NRPE daemon is started by the root # user and is running in standalone mode. pid_file=/var/run/nagios/nrpe.pid # PORT NUMBER # Port number we should wait for connections on. # NOTE: This must be a non-priviledged port (i.e. > 1024). # NOTE: This option is ignored if NRPE is running under either inetd or xinetd server_port=5666 # SERVER ADDRESS # Address that nrpe should bind to in case there are more than one interface # and you do not want nrpe to bind on all interfaces. # NOTE: This option is ignored if NRPE is running under either inetd or xinetd #server_address=127.0.0.1 # NRPE USER # This determines the effective user that the NRPE daemon should run as. # You can either supply a username or a UID. # # NOTE: This option is ignored if NRPE is running under either inetd or xinetd nrpe_user=nagios # NRPE GROUP # This determines the effective group that the NRPE daemon should run as. # You can either supply a group name or a GID. # # NOTE: This option is ignored if NRPE is running under either inetd or xinetd nrpe_group=nagios # ALLOWED HOST ADDRESSES # This is an optional comma-delimited list of IP address or hostnames # that are allowed to talk to the NRPE daemon. # # Note: The daemon only does rudimentary checking of the client's IP # address. I would highly recommend adding entries in your /etc/hosts.allow # file to allow only the specified host to connect to the port # you are running this daemon on. # # NOTE: This option is ignored if NRPE is running under either inetd or xinetd allowed_hosts=127.0.0.1,192.168.133.17 # COMMAND ARGUMENT PROCESSING # This option determines whether or not the NRPE daemon will allow clients # to specify arguments to commands that are executed. This option only works # if the daemon was configured with the --enable-command-args configure script # option. # # *** ENABLING THIS OPTION IS A SECURITY RISK! *** # Read the SECURITY file for information on some of the security implications # of enabling this variable. # # Values: 0=do not allow arguments, 1=allow command arguments dont_blame_nrpe=0 # COMMAND PREFIX # This option allows you to prefix all commands with a user-defined string. # A space is automatically added between the specified prefix string and the # command line from the command definition. # # *** THIS EXAMPLE MAY POSE A POTENTIAL SECURITY RISK, SO USE WITH CAUTION! *** # Usage scenario: # Execute restricted commmands using sudo. For this to work, you need to add # the nagios user to your /etc/sudoers. An example entry for alllowing # execution of the plugins from might be: # # nagios ALL=(ALL) NOPASSWD: /usr/lib/nagios/plugins/ # # This lets the nagios user run all commands in that directory (and only them) # without asking for a password. If you do this, make sure you don't give # random users write access to that directory or its contents! command_prefix=/usr/bin/sudo # DEBUGGING OPTION # This option determines whether or not debugging messages are logged to the # syslog facility. # Values: 0=debugging off, 1=debugging on debug=1 # COMMAND TIMEOUT # This specifies the maximum number of seconds that the NRPE daemon will # allow plugins to finish executing before killing them off. command_timeout=60 # CONNECTION TIMEOUT # This specifies the maximum number of seconds that the NRPE daemon will # wait for a connection to be established before exiting. This is sometimes # seen where a network problem stops the SSL being established even though # all network sessions are connected. This causes the nrpe daemons to # accumulate, eating system resources. Do not set this too low. connection_timeout=300 # WEEK RANDOM SEED OPTION # This directive allows you to use SSL even if your system does not have # a /dev/random or /dev/urandom (on purpose or because the necessary patches # were not applied). The random number generator will be seeded from a file # which is either a file pointed to by the environment valiable $RANDFILE # or $HOME/.rnd. If neither exists, the pseudo random number generator will # be initialized and a warning will be issued. # Values: 0=only seed from /dev/[u]random, 1=also seed from weak randomness #allow_weak_random_seed=1 # INCLUDE CONFIG FILE # This directive allows you to include definitions from an external config file. #include=<somefile.cfg> # INCLUDE CONFIG DIRECTORY # This directive allows you to include definitions from config files (with a # .cfg extension) in one or more directories (with recursion). #include_dir=<somedirectory> #include_dir=<someotherdirectory> # COMMAND DEFINITIONS # Command definitions that this daemon will run. Definitions # are in the following format: # # command[<command_name>]=<command_line> # # When the daemon receives a request to return the results of <command_name> # it will execute the command specified by the <command_line> argument. # # Unlike Nagios, the command line cannot contain macros - it must be # typed exactly as it should be executed. # # Note: Any plugins that are used in the command lines must reside # on the machine that this daemon is running on! The examples below # assume that you have plugins installed in a /usr/local/nagios/libexec # directory. Also note that you will have to modify the definitions below # to match the argument format the plugins expect. Remember, these are # examples only! # The following examples use hardcoded command arguments... command[check_users]=/usr/lib/nagios/plugins/check_users -w 5 -c 10 command[check_load]=/usr/lib/nagios/plugins/check_load -w 15,10,5 -c 30,25,20 command[check_hda1]=/usr/lib/nagios/plugins/check_disk -w 20% -c 10% -p /dev/hda1 command[check_zombie_procs]=/usr/lib/nagios/plugins/check_procs -w 5 -c 10 -s Z command[check_total_procs]=/usr/lib/nagios/plugins/check_procs -w 150 -c 200 # The following examples allow user-supplied arguments and can # only be used if the NRPE daemon was compiled with support for # command arguments *AND* the dont_blame_nrpe directive in this # config file is set to '1'. This poses a potential security risk, so # make sure you read the SECURITY file before doing this. #command[check_users]=/usr/lib/nagios/plugins/check_users -w $ARG1$ -c $ARG2$ #command[check_load]=/usr/lib/nagios/plugins/check_load -w $ARG1$ -c $ARG2$ #command[check_disk]=/usr/lib/nagios/plugins/check_disk -w $ARG1$ -c $ARG2$ -p $ARG3$ #command[check_procs]=/usr/lib/nagios/plugins/check_procs -w $ARG1$ -c $ARG2$ -s $ARG3$ command[restart_http]=/usr/lib/nagios/plugins/http-restart # # local configuration: # if you'd prefer, you can instead place directives here include=/etc/nagios/nrpe_local.cfg # # you can place your config snipplets into nrpe.d/ include_dir=/etc/nagios/nrpe.d/ My Sudoers files # /etc/sudoers # # This file MUST be edited with the 'visudo' command as root. # # See the man page for details on how to write a sudoers file. # Defaults env_reset # Host alias specification # User alias specification # Cmnd alias specification # User privilege specification root ALL=(ALL) ALL nagios ALL=(ALL) NOPASSWD: /usr/lib/nagios/plugins/ # Allow members of group sudo to execute any command # (Note that later entries override this, so you might need to move # it further down) %sudo ALL=(ALL) ALL # #includedir /etc/sudoers.d Hopefully someone can help!

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  • Amarok 2.1.1 Does not go to the next song

    - by nigative
    Hi, I just updated Amarok from KDE3 version and it looks a bit weird and different. But my problem is after I updated my music collection and started to play it (it is all loaded into my playlist), amarok doesn't start next song after the current song is finished. I have repeat(repeat playlist) and random(random tracks) options enabled. Thanks.

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