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• stdio's remove() not always deleting on time.

  - by Kyte

  For a particular piece of homework, I'm implementing a basic data storage system using sequential files under standard C, which cannot load more than 1 record at a time. So, the basic part is creating a new file where the results of whatever we do with the original records are stored. The previous file's renamed, and a new one under the working name is created. The code's compiled with MinGW 5.1.6 on Windows 7. Problem is, this particular version of the code (I've got nearly-identical versions of this floating around my functions) doesn't always remove the old file, so the rename fails and hence the stored data gets wiped by the fopen(). FILE *archivo, *antiguo; remove("IndiceNecesidades.old"); // This randomly fails to work in time. rename("IndiceNecesidades.dat", "IndiceNecesidades.old"); // So rename() fails. antiguo = fopen("IndiceNecesidades.old", "rb"); // But apparently it still gets deleted, since this turns out null (and I never find the .old in my working folder after the program's done). archivo = fopen("IndiceNecesidades.dat", "wb"); // And here the data gets wiped. Basically, anytime the .old previously exists, there's a chance it's not removed in time for the rename() to take effect successfully. No possible name conflicts both internally and externally. The weird thing's that it's only with this particular file. Identical snippets except with the name changed to Necesidades.dat (which happen in 3 different functions) work perfectly fine. // I'm yet to see this snippet fail. FILE *antiguo, *archivo; remove("Necesidades.old"); rename("Necesidades.dat", "Necesidades.old"); antiguo = fopen("Necesidades.old", "rb"); archivo = fopen("Necesidades.dat", "wb"); Any ideas on why would this happen, and/or how can I ensure the remove() command has taken effect by the time rename() is executed? (I thought of just using a while loop to force call remove() again so long as fopen() returns a non-null pointer, but that sounds like begging for a crash due to overflowing the OS with delete requests or something.)

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• [NEWVERSION]algorithm || method to write prog[UNSOLVED] [closed]

  - by fatai

  I am one of the computer science student. Everyone solve problem with a different or same method, ( but actually I dont know whether they use method or I dont know whether there are such common method to approach problem.) if there are common method, What is it ? If there are different method, which method are you using ? All teacher give us problem which in simple form sometimes, but they donot introduce any approach or method(s) so that we cannot make a decision to choose the method then apply that one to problem , afterward find solution then write code.No help from teacher , push us to find method to solve homework. Ex: my friend is using no method , he says "I start to construct algorithm while I try to write prog." I have found one method when I failed the course, More accurately, my method: When I counter problem in language , I will get more paper and then ; first, input/ output step ; my prog will take this / these there argument(s) and return namely X , ex : in c, input length is not known and at same type , so I must use pointer desired output is in form of package , so use structure second, execution part ; in that step , I am writing all step which are goes to final output ex : in python ; 1.) [ + , [- , 4 , [ * , 1 , 2 ]], 5] 2.) [ + , [- , 4 , 2 ],5 ] 3.) [ + , 2 , 5] 4.) 7 ==> return 7 third, I will write test code ex : in c++ input : append 3 4 5 6 vector_x remove 0 1 desired output vector_x holds : 5 6 now, my other question is ; What is/are other method(s) which have/has been; used to construct class :::: for c++ , python, java used to communicate classes / computers used for solving embedded system problem ::::: for c by other user? Some programmer uses generalized method without considering prog-language(java , perl .. ), what is this method ? Why I wonder , because I learn if you dont costruct algorithm on paper, you may achieve your goal. Like no money no lunch , I can say no algorithm no prog therefore , feel free when you write your own method , a way which is introduced by someone else but you are using and you find it is so efficient

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• Creating a spam list with a web crawler in python

  - by user313623

  Hey guys, I'm not trying to do anything malicious here, I just need to do some homework. I'm a fairly new programmer, I'm using python 3.0, and I having difficulty using recursion for problem-solving. I've been stuck on this question for quite a while. Here's the assignment: Write a recursive method spam(url, n) that takes a url of a web page as input and a non-negative integer n, collects all the email address contained in the web page and adds them to a global dictionary variable spam_dict, and then recursively calls itself on every http hyperlink contained in the web page. You will use a dictionary so only one copy of every email address is save; your dictionary will store (key,value) pairs (email, email). The recursive call should use the parameter n-1 instead of n. If n = 0, you should collect the email addresses but no recursive calls should be made. The parameter n is used to limit the recursion to at most depth n. You will need to use the solutions of the two above problems; you method spam() will call the methods links2() and emails() and possibly other functions as well. Notes: 1. running spam() directly will produce no output on the screen; to find your spam_dict, you will need to read the value of spam_dict, and you will also need to reset it to the empty dictionary before every run of spam. 2. Recall how global variables are used. Usage: spam_dict = {} spam('http://reed.cs.depaul.edu/lperkovic/csc242/test1.html',0) spam_dict.keys() dict_keys([]) spam_dict = {} spam('http://reed.cs.depaul.edu/lperkovic/csc242/test1.html',1) spam_dict.keys() dict_keys(['[email protected]', '[email protected]']) So far, I've written a function that traverses web pages and puts all the links in a nice little list, and what I wanted to do was call that functions. And why would I use recursion on a dictionary? And how? I don't understand how n ties into all of this. def links2(url): content = str(urlopen(url).read()) myparser = MyHTMLParser() myparser.feed(content) lst = myparser.get() mergelst = [] for link in lst: mergelst.append(urljoin(lst[0],link)) print(mergelst) Any input (except why spam is bad) would be greatly appreciated. Also, I realize that the above function could probably look better, if you have a way to do it, I'm all ears. However, all I need is the point is for the program to produce the proper output.

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• Complex SQL query with group by and two rows in one

  - by Ricket

  Okay, I need help. I'm usually pretty good at SQL queries but this one baffles me. By the way, this is not a homework assignment, it's a real situation in an Access database and I've written the requirements below myself. Here is my table layout. It's in Access 2007 if that matters; I'm writing the query using SQL. Id (primary key) PersonID (foreign key) EventDate NumberOfCredits SuperCredits (boolean) There are events that people go to. They can earn normal credits, or super credits, or both at one event. The SuperCredits column is true if the row represents a number of super credits earned at the event, or false if it represents normal credits. So for example, if there is an event which person 174 attends, and they earn 3 normal credits and 1 super credit at the event, the following two rows would be added to the table: ID PersonID EventDate NumberOfCredits SuperCredits 1 174 1/1/2010 3 false 2 174 1/1/2010 1 true It is also possible that the person could have done two separate things at the event, so there might be more than two columns for one event, and it might look like this: ID PersonID EventDate NumberOfCredits SuperCredits 1 174 1/1/2010 1 false 2 174 1/1/2010 2 false 3 174 1/1/2010 1 true Now we want to print out a report. Here will be the columns of the report: PersonID LastEventDate NumberOfNormalCredits NumberOfSuperCredits The report will have one row per person. The row will show the latest event that the person attended, and the normal and super credits that the person earned at that event. What I am asking of you is to write, or help me write, the SQL query to SELECT the data and GROUP BY and SUM() and whatnot. Or, let me know if this is for some reason not possible, and how to organize my data to make it possible. This is extremely confusing and I understand if you do not take the time to puzzle through it. I've tried to simplify it as much as possible, but definitely ask any questions if you give it a shot and need clarification. I'll be trying to figure it out but I'm having a real hard time with it, this is grouping beyond my experience...

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• button of MDImenu can't disenable in VS2008

  - by colorlee

  Hi everyone. i had just started to learn VB and VS2008 and im doing some system due to my homework. i made a WELCOME form with a timer, 5s to pass to the next form which called Select. After passed to next form, itll me.visible = false. Theres 3 buttons on the Select form which call Customer, Staff and Exit. As i had just start, the button Customer will pass to a MDI menu call Customer Menu with a menu strip button called Quotation. Same, Select will me.visible = false when done. Then a problem occured, i made a Quotation inside the Customer Menu, such as the mdiparent of Quotation is Customer. I expected that the Quotation button will disenable to press after i pressed that button. But i fail to do that. And the code below: This is the code of MDI menu Customer Menu: Public Class frmCustomer Private Sub ExitToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ExitToolStripMenuItem.Click End End Sub Private Sub AboutUsToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles AboutUsToolStripMenuItem.Click Dim frm As New AboutMamatai AboutMamatai.ShowDialog() End Sub Private Sub frmCustomer_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load frmQuotation.MdiParent = Me frmQuotation.Show() frmQuotation.Dock = DockStyle.Fill Me.Location = New Point(220, 180) End Sub Private Sub QuotationToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles QuotationToolStripMenuItem.Click frmQuotation.MdiParent = Me frmQuotation.Show() frmQuotation.Dock = DockStyle.Fill End Sub End Class This is the code of the form inside the Customer menu: Public Class frmQuotation Private Sub btnExit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnExit.Click frmCustomer.QuotationToolStripMenuItem.Enabled = True Me.Close() End Sub Private Sub frmQuotation_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load frmCustomer.QuotationToolStripMenuItem.Enabled = False End Sub End Class When im tryin to solve this problem, i found that the problem may cause of the me.visible = false of the Select form and Welcome form. Becoz when i set the Customer Menu be the first form to run. The problem is not exist. Is there anyone can help me ? P.S. I guess if the other two forms code is needed so i post them also This is the code of WELCOME form : Public Class frmWELCOME Private Sub frmWELCOME_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load Me.Location = New Point(270, 210) Timer1.Enabled = True End Sub Private Sub Timer1_Tick(ByVal sender As Object, ByVal e As System.EventArgs) Handles Timer1.Tick Timer1.Enabled = False Dim frm As New frmSelect frm.Show() Me.Visible = False End Sub Private Sub btnSkip_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnSkip.Click Timer1.Enabled = False Dim frm As New frmSelect frm.Show() Me.Visible = False End Sub End Class This is the code of Select Form: Public Class frmSelect Private Sub btnCustomer_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnCustomer.Click Dim frm As New frmCustomer frm.Show() Me.Visible = False End Sub Private Sub btnStaff_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnStaff.Click Dim frm As New frmStaff frm.Show() Me.Visible = False End Sub Private Sub btnExit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnExit.Click End End Sub Private Sub frmSelect_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load Me.Location = New Point(390, 250) End Sub End Class

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• Should I add try/catch around when casting on an attribute of JSP implicit object?

  - by Michael Mao

  Hi all: Basically what I mean is like this: List<String[]> routes = (List<String[]>)application.getAttribute("routes"); For the above code, it tries to get an attribute named "routes" from the JSP implicit object - application. But as everyone knows, after this line of code, routes may very well contains a null - which means this application hasn't got an attribute named "routes". Is this "casting on null" good programming practice in Java or not? Basically I try to avoid exceptions such as java.io.InvalidCastException I reckon things like this are more as "heritage" of Java 1.4 when generic types were not introduced to this language. So I guess everything stored in application attributes as Objects (Similar to traditional ArrayList). And when you do "downcast", there might be invalid casts. What would you do in this case? Update: Just found that although in the implicit object application I did store a List of String arrays, when I do this : List<double[]> routes = (List<double[]>)application.getAttribute("routes"); It doesn't produce any error... And I felt not comfortable already... And even with this code: out.print(routes.get(0)); It does print out something strange : [Ljava.lang.String;@18b352f Am I printing a "pointer to String"? I can finally get an exception like this: out.print(routes.get(0)[1]); with error : java.lang.ClassCastException: [Ljava.lang.String; Because it was me to add the application attribute, I know which type should it be cast to. I feel this is not "good enough", what if I forget the exact type? I know there are still some cases where this sort of thing would happen, such as in JSP/Servlet when you do casting on session attributes. Is there a better way to do this? Before you say:"OMG, why you don't use Servlets???", I should justify my reason as this: - because my uni sucks, its server can only work with Servlets generated by JSP, and I don't really want to learn how to fix issues like that. look at my previous question on this , and this is uni homework, so I've got no other choice, forget all about war, WEB-INF,etc, but "code everything directly into JSP" - because the professors do that too. :)

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• Throwing cats out of windows

  - by AndrewF

  Imagine you're in a tall building with a cat. The cat can survive a fall out of a low story window, but will die if thrown from a high floor. How can you figure out the longest drop that the cat can survive, using the least number of attempts? Obviously, if you only have one cat, then you can only search linearly. First throw the cat from the first floor. If it survives, throw it from the second. Eventually, after being thrown from floor f, the cat will die. You then know that floor f-1 was the maximal safe floor. But what if you have more than one cat? You can now try some sort of logarithmic search. Let's say that the build has 100 floors and you have two identical cats. If you throw the first cat out of the 50th floor and it dies, then you only have to search 50 floors linearly. You can do even better if you choose a lower floor for your first attempt. Let's say that you choose to tackle the problem 20 floors at a time and that the first fatal floor is #50. In that case, your first cat will survive flights from floors 20 and 40 before dying from floor 60. You just have to check floors 41 through 49 individually. That's a total of 12 attempts, which is much better than the 50 you would need had you attempted to use binary elimination. In general, what's the best strategy and it's worst-case complexity for an n-storied building with 2 cats? What about for n floors and m cats? Assume that all cats are equivalent: they will all survive or die from a fall from a given window. Also, every attempt is independent: if a cat survives a fall, it is completely unharmed. This isn't homework, although I may have solved it for school assignment once. It's just a whimsical problem that popped into my head today and I don't remember the solution. Bonus points if anyone knows the name of this problem or of the solution algorithm.

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• Find a base case for a recursive void method

  - by Evan S

  I am doing homework. I would like to build a base case for a recursion where ordering given numbers (list2) in ascending order. Purpose of writing this codes is that when all numbers are in ascending order then should stop calling a method called ascending(list2, list1); and all values in list2 should be shipped to list1. For instance, list2 = 6,5,4,3,2,1 then list2 becomes empty and list1 should be 1,2,3,4,5,6. I am trying to compare result with previous one and if matches then stop. But I can't find the base case to stop it. In addition, Both ascending() and fixedPoint() are void method. Anybody has idea? lol Took me 3 days... When I run my code then 6,5,4,3,2,1 5,6,4,3,2,1 4,5,6,3,2,1 3,4,5,6,2,1 2,3,4,5,6,1 1,2,3,4,5,6 1,2,3,4,5,6 1,2,3,4,5,6 1,2,3,4,5,6 1,2,3,4,5,6 infinite............. public class Flipper { public static void main(String[] args) { Flipper aFlipper = new Flipper(); List<Integer> content = Arrays.asList(6,5,4,3,2,1); ArrayList<Integer> l1 = new ArrayList<Integer>(content); ArrayList<Integer> l2 = new ArrayList<Integer>(); // empty list aFlipper.fixedPoint(l2,l1); System.out.println("fix l1 is "+l1); System.out.println("fix l2 is "+l2); } public void fixedPoint(ArrayList<Integer> list1, ArrayList<Integer> list2) { // data is in list2 ArrayList<Integer> temp1 = new ArrayList<Integer>(); // empty list if (temp1.equals(list2)) { System.out.println("found!!!"); } else { ascending(list2, list1); // data, null temp1 = list1; // store processed value System.out.println("st list1 is "+list1); System.out.println("st list2 is "+list2); } fixedPoint(list2, list1); // null, processed data }

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• Problem with OOP Class Definitions

  - by oben

  Hi, this is Oben from Turkey. I work for my homework in C++ and i have some problems with multiply definitions. My graph class ; class Graph{ private: string name; //Graph name fstream* graphFile; //Graph's file protected: string opBuf; //Operations buffer int containsNode(string); //Query if a node is present Node* nodes; //Nodes in the graph int nofNodes; //Number of nodes in the graph public: static int nOfGraphs; //Number of graphs produced Graph(); //Constructors and destructor Graph(int); Graph(string); Graph(const Graph &); ~Graph(); string getGraphName(); //Get graph name bool addNode(string); //add a node to the graph bool deleteNode(string); //delete a node from the graph bool addEdge(string,string); //add an edge to the graph bool deleteEdge(string,string); //delete an edge from the graph void intersect(const Graph&); //intersect the graph with the <par> void unite(const Graph&); //intersect the graph with the <par> string toString(); //get string representation of the graph void acceptTraverse(BreadthFirst*); void acceptTraverse(DepthFirst *); }; and my traversal class; class Traversal { public: string *visitedNodes; virtual string traverse (const Graph & ); }; class BreadthFirst : public Traversal { public : BreadthFirst(); string traverse(); }; class DepthFirst : public Traversal { public : DepthFirst(); string traverse(); }; My problem is in traversal class , i need to declare Graph class at the same time , in graph class i need traversal class to declare. I have big problems with declerations :) Could you please help me ?

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• ajaxSubmit and Other Code. Can someone help me determine what this code is doing?

  - by Matt Dawdy

  I've inherited some code that I need to debug. It isn't working at present. My task is to get it to work. No other requirements have been given to me. No, this isn't homework, this is a maintenance nightmare job. ASP.Net (framework 3.5), C#, jQury 1.4.2. This project makes heavy use of jQuery and AJAX. There is a drop down on a page that, when an item is chosen, is supposed to add that item (it's a user) to an object in the database. To accomplish this, the previous programmer first, on page load, dynamically loads the entire page through AJAX. To do this, he's got 5 div's, and each one is loaded from a jquery call to a different full page in the website. Somehow, the HTML and BODY and all the other stuff is stripped out and the contents of the div are loaded with the content of the aspx page. Which seems incredibly wrong to me since it relies on the browser to magically strip out html, head, body, form tags and merge with the existing html head body form tags. Also, as the "content" page is returned as a string, the previous programmer has this code running on it before it is appended to the div: function CleanupResponseText(responseText, uniqueName) { responseText = responseText.replace("theForm.submit();", "SubmitSubForm(theForm, $(theForm).parent());"); responseText = responseText.replace(new RegExp("theForm", "g"), uniqueName); responseText = responseText.replace(new RegExp("doPostBack", "g"), "doPostBack" + uniqueName); return responseText; } When the dropdown itself fires it's onchange event, here is the code that gets fired: function SubmitSubForm(form, container) { //ShowLoading(container); $(form).ajaxSubmit( { url: $(form).attr("action"), success: function(responseText) { $(container).html(CleanupResponseText(responseText, form.id)); $("form", container).css("margin-top", "0").css("padding-top", "0"); //HideLoading(container); } } ); } This blows up in IE, with the message that "Microsoft JScript runtime error: Object doesn't support this property or method" -- which, I think, has to be that $(form).ajaxSubmit method doesn't exist. What is this code really trying to do? I am so turned around right now that I think my only option is to scrap everything and start over. But I'd rather not do that unless necessary. Is this code good? Is it working against .Net, and is that why we are having issues?

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• circles and triangles problem

  - by Faken

  Hello everyone, I have an interesting problem here I've been trying to solve for the last little while: I have 3 circles on a 2D xy plane, each with the same known radius. I know the coordinates of each of the three centers (they are arbitrary and can be anywhere). What is the largest triangle that can be drawn such that each vertice of the triangle sits on a separate circle, what are the coordinates of those verticies? I've been looking at this problem for hours and asked a bunch of people but so far only one person has been able to suggest a plausible solution (though i have no way of proving it). The solution that we have come up with involves first creating a triangle about the three circle centers. Next we look at each circle individually and calculate the equation of a line that passes through the circle's center and is perpendicular to the opposite edge. We then calculate two intersection points of the circle. This is then done for the next two circles with a result of 6 points. We iterate over the 8 possible 3 point triangles that these 6 points create (the restriction is that each point of the big triangle must be on a separate circle) and find the maximum size. The results look reasonable (at least when drawn out on paper) and it passes the special case of when the centers of the circles all fall on a straight line (gives a known largest triangle). Unfortunate i have no way of proving this is correct or not. I'm wondering if anyone has encountered a problem similar to this and if so, how did you solve it? Note: I understand that this is mostly a math question and not programming, however it is going to be implemented in code and it must be optimized to run very fast and efficient. In fact, I already have the above solution in code and tested to be working, if you would like to take a look, please let me know, i chose not to post it because its all in vector form and pretty much impossible to figure out exactly what is going on (because it's been condensed to be more efficient). Lastly, yes this is for school work, though it is NOT a homework question/assignment/project. It's part of my graduate thesis (abet a very very small part, but still technically is part of it). Thanks for your help.

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• Best approach for using Scanner Objects in Java?

  - by devjeetroy

  Although I'm more of a C++/ASM guy, I have to work with java as a part of my undergrad course at college. Our teacher taught us input using Scanner(System.in), and told us that if multiple functions are were taking user input, it would be advisable that a single Scanner object is passed around so as to reduce chances of the input stream getting screwed up. Now using this approach has gotten me into a situation where I'm trying to use a Scanner.nextLine(), and this statement does not wait for user input. It just moves on to the following statement. I figured there may be some residual cr/lf or other characters in the Scanner that might not have been retrieved are causing the problem. Here is the code. while(lineScanner.hasNext()) { if(isPlaceHolder(temp = lineScanner.next())) { temp = temp.replace("<",""); temp = temp.replace(">", ""); System.out.print("Enter "+aOrA(temp.charAt(0)) +" " +temp + " : "); temp = consoleInput.nextLine(); } outputFileStream.print(temp + " "); } All of the code is inside a function which receives a Scanner object consoleInput. Ok, so what happens when i run it is that when the program enters the if() the first time, It carries out theSystem.out.print, does not wait for user input, and moves on to the second time that it enters the 'if' block. This time, it takes the input and the rest of the program operates normally. What is even more surprising is that when i check the output file created by the program, it is perfect, just as i want to be. Almost as if the first time input using the scanner is correct. I have solved this problem by creating a new system.in Scanner in the function itself, instead of receiving the Scanner object as a parameter. But I am still very curious to know what the hell is happening and why it couldn't be solved using a simple Scanner.reset(). Would it be better to just simply create a Scanner Object for each function? Thanks, Devjeet PS. Although I know how to take input using fileinputstreams and the like, we are not supposed to use it with the homework.

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• Finding good heuristic for A* search

  - by Martin

  I'm trying to find the optimal solution for a little puzzle game called Twiddle (an applet with the game can be found here). The game has a 3x3 matrix with the number from 1 to 9. The goal is to bring the numbers in the correct order using the minimum amount of moves. In each move you can rotate a 2x2 square either clockwise or counterclockwise. I.e. if you have this state 6 3 9 8 7 5 1 2 4 and you rotate the upper left 2x2 square clockwise you get 8 6 9 7 3 5 1 2 4 I'm using a A* search to find the optimal solution. My f() is simply the number of rotations need. My heuristic function already leads to the optimal solution but I don't think it's the best one you can find. My current heuristic takes each corner, looks at the number at the corner and calculates the manhatten distance to the position this number will have in the solved state (which gives me the number of rotation needed to bring the number to this postion) and sums all these values. I.e. You take the above example: 6 3 9 8 7 5 1 2 4 and this end state 1 2 3 4 5 6 7 8 9 then the heuristic does the following 6 is currently at index 0 and should by at index 5: 3 rotations needed 9 is currently at index 2 and should by at index 8: 2 rotations needed 1 is currently at index 6 and should by at index 0: 2 rotations needed 4 is currently at index 8 and should by at index 3: 3 rotations needed h = 3 + 2 + 2 + 3 = 10 But there is the problem, that you rotate 4 elements at once. So there a rare cases where you can do two (ore more) of theses estimated rotations in one move. This means theses heuristic overestimates the distance to the solution. My current workaround is, to simply excluded one of the corners from the calculation which solves this problem at least for my test-cases. I've done no research if really solves the problem or if this heuristic still overestimates in same edge-cases. So my question is: What is the best heuristic you can come up with? (Disclaimer: This is for a university project, so this is a bit of homework. But I'm free to use any resource if can come up with, so it's okay to ask you guys. Also I will credit Stackoverflow for helping me ;) )

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• A program where user enters a string and the program counts the instances of the letters

  - by user1865183

  This is the first C++ program I have ever written and I'm having trouble understanding the order in which operands must be put in. This is for a class, but it looks like I'm not supposed to use the homework tag. Sorry if I'm doing this wrong. This is my input // Get DNA string string st; cout << "Enter the DNA sequence to be analysed: "; cin >> st; This seems to work ok, but I thought I would include it incase this is what I'm doing wrong. This is what I have so far to check that the input is exclusively C,T,A, or G. It runs through the program and simply prints "Please enter a valid sequnce1, please enter a valid sequence2, ... ect. I'm sure I'm doing something very stupid, I just can't figure it out. // Check that the sequence is all C, T, A, G while (i <= st.size()){ if (st[i] != 'c' && st[i] != 'C' && st[i] != 'g' && st[i] != 'G' && st[i] != 't' && st[i] != 'T' && st[i] != 'a' && st[i] != 'A'); cout << "Please enter a valid sequence" << i++; else if (st[i] == c,C,G,t,T,a,A) i++; The second half of my program is to count the number of Cs and Gs in the sequence for (i < st.size() ; i++ ;); for (loop <= st.size() ; loop++;) if (st[loop] == 'c') { count_c++; } else if (st[loop] == C) { count_c++; } else if (st[loop] == g) { count_g++; } else if (st[loop] == G); { count_g++; } cout << "Number of instances of C = " << count_c; cout << "Number of instances of G = " << count_g; It seems like it's not looping, it will count 1 of one of the letters. How do I make it loop? I can't seem to put in endl; anywhere without getting an error back, although I know I'll need it somewhere. Any help or tips to point me in the right direction would be greatly appreciated - I've been working on this code for two days (this is embarrassing to admit).

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• How do I access the enumerated item with an indexer and assign array string to it for display?

  - by g00p3k

  EDITED: Updated 3/23/09. See rest of post at bottom. I'm still having trouble with the indexer. Anymore help or examples would really help me out. Write a class, MyCourses, that contains an enumeration of all the courses that you are currently taking. This enum should be nested inside of your class MyCourses. Your class should also have an array field that provides a short description (as a String) of each of your courses. Write an indexer that takes one of your enumerated courses as an index and returns the String description of the course. Write a class MyFriends that contains an indexer that provides access to the names of your friends. namespace IT274_Unit4Project { public class MyCourses { // enumeration that contains an enumeration of all the courses that // student is currently enrolled in public enum CourseName {IT274= 0,CS210 = 1} // array field that provides short description for each of classes, // returns string description of the course private String[] courseDescription = {"Intermediate C#: Teaches intermediate elements of C# programming and software design", "Career Development Strategies: Teaches principles for career progression, resume preparation, and overall self anaylsis"}; // indexer that takes one of the enumerated courses as an index // and returns the String description of the course public String this[CourseName index] { get { if (index == 1) return courseDescription[0]; else return courseDescription[1]; } set { if (index == 1) courseDescription[0] = value; else courseDescription[1] = value; } } } }//end public class MyCourses I'm working on this homework project and having trouble understanding the text explaining how to correctly take the accessed value of the enumeration and then apply the string array value to it. Can you please help me understand this? The text we are using is very difficult and poorly written for a beginner to understand, so I'm kind of on my own here. I've got the first parts written, but need some help on the accessing of the enumeration value and assigning, i think i'm close, but don't understand how to properly get and set the values on this. Please do not provide me with direct code answers, unless a MSDN style explanation that is generalized and not specific to my project. ie: public class MyClass { string field1; string field2; //properties public string Value1 get etc... Thanks!

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• makecontext segfault?

  - by cdietschrun

  I am working on a homework assignment that will be due in the next semester. It requires us to implement our own context switching/thread library using the ucontext API. The professor provides code that does it, but before a thread returns, he manually does some work and calls an ISR that finds another thread to use and swapcontexts to it or if none are left, exits. The point of the assignment is to use the uc_link field of the context so that when it hits a return it takes care of the work. I've created a function (type void/void args) that just does the work the functions did before (clean up and then calls ISR). The professor said he wanted this. So all that's left is to do a makecontext somewhere along the way on the context in the uc_link field so that it runs my thread, right? Well, when I do makecontext on seemingly any combination of ucontext_t's and function, I get a segfault and gdb provides no help.. I can skip the makecontext and my program exist 'normally' when it hits a return in the threads I created because (presumably) the uc_link field is not properly setup (which is what I'm trying to do). I also can't find anything on why makecontext would segfault. Can anyone help? stack2.ss_sp = (void *)(malloc(STACKSIZE)); if(stack2.ss_sp == NULL){ printf("thread failed to get stack space\n"); exit(8); } stack2.ss_size = STACKSIZE; stack2.ss_flags = 0; if(getcontext(&main_context) == -1){ perror("getcontext in t_init, rtn_env"); exit(5); } //main_context.uc_stack = t_state[i].mystk; main_context.uc_stack = stack2; main_context.uc_link = 0; makecontext(&main_context, (void (*)(void))thread_rtn, 0); I've also tried just thread_rtn, &thread_rtn and other things. thread_rtn is declared as void thread_rtn(void). later, in each thread. run_env is of type ucontext_t: ... t_state[i].run_env.uc_link = &main_context;

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• Java Error When correct code is put together

  - by Eric

  I have a few string problems that I need to put together for a complete homework assignment. They all work correctly by themselves, but when I put them together in the main function, the last one that finds the smallest word in a string gives an error. Anyone know why? public static void main(String[] args){ Scanner sc = new Scanner(System.in); //Length of Word String word1 = sc.next(); System.out.println(word1.length()); //Evens in one string odds in the other String word2 = sc.next(); StringBuilder even = new StringBuilder(); StringBuilder odd = new StringBuilder(); for(int i = 0; i < word2.length(); i++){ if(i % 2 == 0){ even.append(word2.charAt(i)); } else{ odd.append(word2.charAt(i)); } } System.out.println(even + " " + odd); //Diminishing Suffix String word3 = sc.next(); for(int j = 0; j < word3.length(); j++){ System.out.print(word3.substring(j, word3.length()) + " "); } System.out.printf("\n"); //Letter Replacement String word4 = sc.next(); String word5 = sc.next(); String word6 = sc.next(); String word7 = word4.replace(word5, word6); System.out.println(word7); //How many times x appears in xstring String word8 = sc.next(); String word9 = sc.next(); int index = word8.indexOf(word9); int count = 0; while (index != -1) { count++; word8 = word8.substring(index + 1); index = word8.indexOf(word9); } System.out.println(count); System.out.println(); //Lexicographically smallest word String Sentence = sc.nextLine(); String[] myWords = Sentence.split(" "); int shortestLengths, shortestLocation; shortestLengths=(myWords[1]).length(); shortestLocation=1; for (int i = 1; i <myWords.length; i++) { if ((myWords[i]).length() < shortestLengths) { shortestLengths=(myWords[i]).length(); shortestLocation=i; } } System.out.println(myWords[shortestLocation]); } } Talking about the lexicographically smallest one

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• Try out Windows Phone 7 on your PC today

  - by Matthew Guay

  Anticipation has been building for the new Windows Phone 7 Series ever since Microsoft unveiled it at the Mobile World Congress in February.  Now, thanks to free developer tools, you can get a first-hand experience of the basic Windows Phone 7 Series devices on your PC. Windows Phone 7 Series represents a huge change in the mobile field for Microsoft, bringing the acclaimed Zune HD UI to an innovative phone platform.  Windows Mobile has often been criticized for being behind other Smartphone platforms, but Microsoft seeks to regain the lead with this new upcoming release.  A platform must have developers behind it to be useful, so they have released a full set of free development tools so anyone can make apps for it today.  Or, if you simply want to play with Windows Phone 7, you can use the included emulator to try out the new Metro UI.  Here’s how to do this today on your Vista or 7 computer. Please note: These tools are a Customer Technology Preview release, so only install them if you’re comfortable using pre-release software. Getting Started First, download the Windows Phone Developer Tools CTP (link below), and run the installer.  This will install the Customer Technology Preview (CTP) versions of Visual Studio 2010 Express for Windows Phone, Windows Phone Emulator, Silverlight for Windows Phone, and XNA 4.0 Game Studio on your computer, all of which are required and cannot be installed individually. Accept the license agreement when prompted. Click “Install Now” to install the tools you need.  The only setup customization option is where to save the files, so choose Customize if you need to do so. Setup will now automatically download and install the components you need, and will additionally download either 32 or 64 bit programs depending on your operating system. About halfway thorough the installation, you’ll be prompted to reboot your system.  Once your computer is rebooted, setup will automatically resume without further input.   When setup is finished, click “Run the Product Now” to get started. Running Windows Phone 7 on your PC Now that you’ve got the Windows Phone Developer tools installed, it’s time to get the Windows Phone emulator running.  If you clicked “Run the Product Now” when the setup finished, Visual Studio 2010 Express for Windows Phone should have already started.   If not, simply enter “visual studio” in your start menu search and select “Microsoft Visual Studio 2010 Express for Windows Phone”. Now, to run the Windows Phone 7 emulator, we have to test an application.  So, even if you don’t know how to program, we can open a phone application template, and then test it to run the emulator.  First, click New Project on the left hand side of the front page. Any of the application templates would work for this, but here let’s select “Windows Phone Application”, and then click Ok. Here’s your new application template, which already contains the basic phone application framework.  This is where you’d start if you want to develop a Windows Phone app, but for now we just want to see Windows Phone 7 in action. So, to run the emulator, click Debug in the menu and then select Start Debugging. Your new application will launch inside the Windows Phone 7 Series emulator.  The default template doesn’t give us much, but it does show an example application running in Windows Phone 7.   Exploring Windows Phone 7 Click the Windows button on the emulator to go to the home screen.  Notice the Zune HD-like transition animation.  The emulator only includes Internet Explorer, your test application, and a few settings. Click the arrow on the right to see the available applications in a list. Settings lets you change the theme, regional settings, and the date and time in your emulator.  It also has an applications settings pane, but this currently isn’t populated. The Time settings shows a unique Windows Phone UI. You can return to the home screen by pressing the Windows button.  Here’s the Internet Explorer app running, with the virtual keyboard open to enter an address.  Please note that this emulator can also accept input from your keyboard, so you can enter addresses without clicking on the virtual keyboard. And here’s Google running in Internet Explorer on Windows Phone 7. Windows Phone 7 supports accelerometers, and you can simulate this in the emulator.  Click one of the rotate buttons to rotate the screen in that direction. Here’s our favorite website in Internet Explorer on Windows Phone 7 in landscape mode. All this, running right inside your Windows 7 desktop… Developer tools for Windows Phone 7 Although it may be fun to play with the Windows Phone 7 emulator, developers will be more excited to actually be able to create new and exciting apps for it.  The Windows Phone Developer Tools download includes Visual Studio Express and XNA Game Studio 4.0 which lets you create enticing games and apps for Windows Phones.  All development for Windows Phones will be in C#, Silverlight, and the XNA game framework.  Visual Studio Express for Windows Phone includes templates for these, and additionally has code samples to help you get started with development. Conclusion Many features are still not functional in this preview version, such as the search button and most of the included applications.  However, this still gives you a great way to experience firsthand the future of the Windows Phone platform.  And, for developers, this is your chance to set your mark on the Windows Phone 7 Series even before it is released to the public.  Happy playing and developing! Links Download Windows Phone Developer Tools CTP Windows Phone Developer Site Similar Articles Productive Geek Tips Keep Track of Homework Assignments with SoshikuWeekend Fun: Watch Television On Your PC With TVUPlayerEasily Manage Your Downloads with Download StatusbarCreate a Shortcut or Hotkey to Mute the System Volume in WindowsHow-To Geek on Lifehacker: How to Make Windows Vista Less Annoying TouchFreeze Alternative in AutoHotkey The Icy Undertow Desktop Windows Home Server – Backup to LAN The Clear & Clean Desktop Use This Bookmarklet to Easily Get Albums Use AutoHotkey to Assign a Hotkey to a Specific Window Latest Software Reviews Tinyhacker Random Tips Revo Uninstaller Pro Registry Mechanic 9 for Windows PC Tools Internet Security Suite 2010 PCmover Professional Convert the Quick Launch Bar into a Super Application Launcher Automate Tasks in Linux with Crontab Discover New Bundled Feeds in Google Reader Play Music in Chrome by Simply Dragging a File 15 Great Illustrations by Chow Hon Lam Easily Sync Files & Folders with Friends & Family

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• I have Oracle SQL Developer Installed, Now What?

  - by thatjeffsmith

  If you’re here because you downloaded a copy of Oracle SQL Developer and now you need help connecting to a database, then you’re in the right place. I’ll show you what you need to get up and going so you can finish your homework, teach yourself Oracle database, or get ready for that job interview. You’ll need about 30 minutes to set everything up…and about 5 years to become proficient with Oracle Oracle Database come with SQL Developer but SQL Developer doesn’t include a database If you install Oracle database, it includes a copy of SQL Developer. If you’re running that copy of SQL Developer, please take a second to upgrade now, as it is WAY out of date. But I’m here to talk to the folks that have downloaded SQL Developer and want to know what to do next. You’ve got it running. You see this ‘Connection’ dialog, and… Where am I connecting to, and who as? You NEED a database Installing SQL Developer does not give you a database. So you’re going to need to install Oracle and create a database, or connect to a database that is already up and running somewhere. Basically you need to know the following: where is this database, what’s it called, and what port is the listener running on? The Default Connection properties in SQL Developer These default settings CAN work, but ONLY if you have installed Oracle Database Express Edition (XE). Localhost is a network alias for 127.0.0.1 which is an IP address that maps to the ‘local’ machine, or the machine you are reading this blog post on. The listener is a service that runs on the server and handles connections for the databases on that machine. You can run a database without a listener and you can run a listener without a database, but you can’t connect to a database on a different server unless both that database and listener are up and running. Each listener ‘listens’ on one or more ports, you need to know the port number for each connection. The default port is 1521, but 1522 is often pretty common. I know all of this sounds very complicated Oracle is a very sophisticated piece of software. It’s not analogous to downloading a mobile phone app and and using it 10 seconds later. It’s not like installing Office/Access either – it requires services, environment setup, kernel tweaks, etc. However. Normally an administrator will setup and install Oracle, create the database, and configure the listener for everyone else to use. They’ll often also setup the connection details for everyone via a ‘TNSNAMES.ORA’ file. This file contains a list of database connection details for folks to browse – kind of like an Oracle database phoneboook. If someone has given you a TNSNAMES.ORA file, or setup your machine to have access to a TNSNAMES file, then you can just switch to the ‘TNS’ connection type, and use the dropdown to select the database you want to connect to. Then you don’t have to worry about the server names, database names, and the port numbers. ORCL – that sounds promising! ORCL is the default SID when creating a new database with the Database Creation Assistant (DBCA). It’s just me, and I need help! No administrator, no database, no nothing. What do you do? You have a few options: Buy a copy of Oracle and download, install, and create a database Download and install XE (FREE!) Download, import, and run our Developer Days Hands-on-Lab (FREE!) If you’re a student (or anyone else) with little to no experience with Oracle, then I recommend the third option. Oracle Technology Network Developer Day: Hands-on Database Application Development Lab The OTN lab runs on a A Virtual Box image which contains: 11gR2 Enterprise Edition copy of Oracle a database and listener running for you to connect to lots of demo data for you to play with SQL Developer installed and ready to connect Some browser based labs you can step through to learn Oracle You download the image, you download and install Virtual Box (also FREE!), then you IMPORT the image you previously downloaded. You then ‘Start’ the image. It will boot a copy of Oracle Enterprise Linux (OEL), start your database, and all that jazz. You can then start up and run SQL Developer inside the image OR you can connect to the database running on the image using the copy of SQL Developer you installed on your host machine. Setup Port Forwarding to Make It Easy to Connect From Your Host When you start the image, it will be assigned an IP address. Depending on what network adapter you select in the image preferences, you may get something that can get out to the internet from your image, something your host machine can see and connect to, or something that kind of just lives out there in a vacuum. You want to avoid the ‘vacuum’ option – unless you’re OK with running SQL Developer inside the Linux image. Open the Virtual Box image properties and go to the Networking options. We’re going to setup port forwarding. This will tell your machine that anything that happens on port 1521 (the default Oracle Listener port), should just go to the image’s port 1521. So I can connect to ‘localhost’ and it will magically get transferred to the image that is running. Oracle Virtual Box Port Forwarding 1521 listener database Now You Just Need a Username and Password The default passwords on this image are all ‘oracle’ – so you can connect as SYS, HR, or whatever – just use ‘oracle’ as the password. The Linux passowrds are all ‘oracle’ too, so you can login as ‘root’ or as ‘oracle’ in the Linux desktop. Connect! Connect as HR to your Oracle database running on the OTN Developer Days Virtual Box image If you’re connecting to someone else’s database, you need to ask the person that manages that environment to create for you an account. Don’t try to ‘guess’ or ‘figure out’ what the username and password is. Introduce yourself, explain your situation, and ask kindly for access. This is your first test – can you connect? I know it’s hard to get started with Oracle. There are however many things we offer to make this easier. You’ll need to do a bit of RTM first though. Once you know what’s required, you will be much more likely to succeed. Of course, if you need help, you know where to find me

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• Clarity is important, both in question and in answer.

  - by gerrylowry

  clarity is important ... i'm often reminded of the Clouseau movie in which Peter Sellers as Chief Inspector Clouseau asks a hotel clerk "Does your dog bite?" ... the clerk answers "no" ... after Clouseau has been bitten by the dog, he looks at the hotel clerk who says "That's not my dog".  Clarity is important, both in question and in answer. i've been a member of forums.asp.net since 2008 ... like many of my peers at forums.asp.net, i've answered my fair share of questions. FWIW, the purpose of this, my first web log post to http://weblogs.asp.net/gerrylowry is to help new members ask better questions and in turn get better answers. TIMTOWTDI  =.  there is more than one way to do it imho, the best way to ask a question in any forum, or even person to person, is to first formulate your question and then ask yourself to answer your own question. Things to consider when asking (the more complete your question, the more likely you'll get the answer you require): -- have you searched Google and/or your favourite search engine(s) before posting your question to forums.asp.net; examples: site:msdn.microsoft.com entity framework 5.0 c#http://lmgtfy.com/?q=site%3Amsdn.microsoft.com+entity+framework+5.0+c%23 site:forums.asp.net MVC tutorial c#http://lmgtfy.com/?q=site%3Aforums.asp.net+MVC+tutorial+c%23 -- are you asking your question in the correct forum?  look at the forums' descriptions at http://forums.asp.net/; examples: Getting Started If you have a general ASP.NET question on a topic that's not covered by one of the other more specific forums - ask it here. MVC Discussions regarding ASP.NET Model-View-Controller (MVC) C# Questions about using C# for ASP.NET development Note:  if your question pertains more to c# than to MVC, choosing the C# forum is likely to be more appropriate. -- is your post subject clear and concise, yet not too vague? compare these three subjects (all three had something to do with GridView):     (1)    please help     (2)    gridview      (3)    How to show newline in GridView  -- have you clearly explained your scenario? compare:  my leg hurts   with   when i walk too much, my right knee hurts in the knee joint  compare:  my code does not work    with    when i enter a date as 2012-11-8, i get a FormatException -- have you checked your spelling, your grammar, and your English? for better or worse, English is the language of forums.asp.net ... many of the currently 170000++ forums.asp.net are not native speakers of English; that's okay ... however, there are times when choosing the more appropriate words will likely get one a better answer; fortunately, there are web tools to help you formulate your question, for example, http://translate.google.com/.  -- have you provided relevant information about your environment? here are a few examples ... feel free to include other items to your question ... rule of thumb:  if you think a given detail is relevant, it likely is -- what technology are you using?    ASP.NET MVC 4, ASP.NET MVC 3, WebForms, ...  -- what version of Visual Studio are you using?  vs2012 (ultimate, professional, express), vs2010, vs2008 ... -- are you hosting your own website?  are you using a shared hosting service? -- are you experience difficulties in just one browser? more than one browser? -- what browser version(s) are you using?   ie8? ie9? ... -- what is your operating system?     win8, win7, vista, XP, server 2008 R2 ... -- what is your database?   SQL Server 2008 R2, ss2005, MySQL, Oracle, ... -- what is your web server?  iis 7.5, iis 6, .... -- have you provided enough information for someone to be able to answer your question? Here's an actual example from an O.P. that i hope is self-explanatory: I'm trying to make a simple calculator when i write the code in windows application it worked when i tried it in web application it doesn't work and there are no errors what should i do ??!! -- have you included unnecessary information? more than once, i've seen the O.P. (original post, original poster) include many extra lines of code that were not relevant to the actual question; the more unnecessary code that you include, the less likely your volunteer peers will be motivated to donate their time to help you. -- have you asked the question that you want answered? "Does this dog bite?" -- are your expectations reasonable? -- generally, persons who are going to answer your questions are your peers ... they are unpaid volunteers ... -- are you looking for help with your homework, work assignment, or hobby? or, are you expecting someone else to do your work for you?  -- do you expect a complete solution or are you simply looking for guidance and direction? -- you are likely to get more help by first making a reasonable effort to help yourself first Clarity is important, both in question and in answer. if you are answering someone else's question, please remember that clear answers are just as important as clear questions; would you understand your own answer? Things to consider when answering: -- have you tested your code example?  if you have, say so; if you've not tested your code example, also say so -- imho, it's okay to guess as long as you clearly state that you're guessing ... sometimes a wrong guess can still help the O.P. find her/his way to the right answer -- meanness does not contribute to being helpful; sometimes one may become frustrated with the O.P. and/or others participating in a thread, if that happens to you, be kind regardless; speaking from my own experience, at least once i've allowed myself to be frustrated into writing something inappropriate that i've regretted later ... being a meany does not feel good ... being kind and helpful feels fantastic! Tip:  before asking your question, read more than a few existing questions and answers to get a sense of how your peers ask and answer questions. Gerry P.S.:  try to avoid necroposting and piggy backing. necroposting is adding to an old post, especially one that was resolved months ago. piggy backing is adding your own question to someone else's thread.

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• MySQL Cluster 7.2: Over 8x Higher Performance than Cluster 7.1

  - by Mat Keep

  0 0 1 893 5092 Homework 42 11 5974 14.0 Normal 0 false false false EN-US JA X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:Cambria; mso-ascii-font-family:Cambria; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Cambria; mso-hansi-theme-font:minor-latin; mso-ansi-language:EN-US;} Summary The scalability enhancements delivered by extensions to multi-threaded data nodes enables MySQL Cluster 7.2 to deliver over 8x higher performance than the previous MySQL Cluster 7.1 release on a recent benchmark What’s New in MySQL Cluster 7.2 MySQL Cluster 7.2 was released as GA (Generally Available) in February 2012, delivering many enhancements to performance on complex queries, new NoSQL Key / Value API, cross-data center replication and ease-of-use. These enhancements are summarized in the Figure below, and detailed in the MySQL Cluster New Features whitepaper Figure 1: Next Generation Web Services, Cross Data Center Replication and Ease-of-Use Once of the key enhancements delivered in MySQL Cluster 7.2 is extensions made to the multi-threading processes of the data nodes. Multi-Threaded Data Node Extensions The MySQL Cluster 7.2 data node is now functionally divided into seven thread types: 1) Local Data Manager threads (ldm). Note – these are sometimes also called LQH threads. 2) Transaction Coordinator threads (tc) 3) Asynchronous Replication threads (rep) 4) Schema Management threads (main) 5) Network receiver threads (recv) 6) Network send threads (send) 7) IO threads Each of these thread types are discussed in more detail below. MySQL Cluster 7.2 increases the maximum number of LDM threads from 4 to 16. The LDM contains the actual data, which means that when using 16 threads the data is more heavily partitioned (this is automatic in MySQL Cluster). Each LDM thread maintains its own set of data partitions, index partitions and REDO log. The number of LDM partitions per data node is not dynamically configurable, but it is possible, however, to map more than one partition onto each LDM thread, providing flexibility in modifying the number of LDM threads. The TC domain stores the state of in-flight transactions. This means that every new transaction can easily be assigned to a new TC thread. Testing has shown that in most cases 1 TC thread per 2 LDM threads is sufficient, and in many cases even 1 TC thread per 4 LDM threads is also acceptable. Testing also demonstrated that in some instances where the workload needed to sustain very high update loads it is necessary to configure 3 to 4 TC threads per 4 LDM threads. In the previous MySQL Cluster 7.1 release, only one TC thread was available. This limit has been increased to 16 TC threads in MySQL Cluster 7.2. The TC domain also manages the Adaptive Query Localization functionality introduced in MySQL Cluster 7.2 that significantly enhanced complex query performance by pushing JOIN operations down to the data nodes. Asynchronous Replication was separated into its own thread with the release of MySQL Cluster 7.1, and has not been modified in the latest 7.2 release. To scale the number of TC threads, it was necessary to separate the Schema Management domain from the TC domain. The schema management thread has little load, so is implemented with a single thread. The Network receiver domain was bound to 1 thread in MySQL Cluster 7.1. With the increase of threads in MySQL Cluster 7.2 it is also necessary to increase the number of recv threads to 8. This enables each receive thread to service one or more sockets used to communicate with other nodes the Cluster. The Network send thread is a new thread type introduced in MySQL Cluster 7.2. Previously other threads handled the sending operations themselves, which can provide for lower latency. To achieve highest throughput however, it has been necessary to create dedicated send threads, of which 8 can be configured. It is still possible to configure MySQL Cluster 7.2 to a legacy mode that does not use any of the send threads – useful for those workloads that are most sensitive to latency. The IO Thread is the final thread type and there have been no changes to this domain in MySQL Cluster 7.2. Multiple IO threads were already available, which could be configured to either one thread per open file, or to a fixed number of IO threads that handle the IO traffic. Except when using compression on disk, the IO threads typically have a very light load. Benchmarking the Scalability Enhancements The scalability enhancements discussed above have made it possible to scale CPU usage of each data node to more than 5x of that possible in MySQL Cluster 7.1. In addition, a number of bottlenecks have been removed, making it possible to scale data node performance by even more than 5x. Figure 2: MySQL Cluster 7.2 Delivers 8.4x Higher Performance than 7.1 The flexAsynch benchmark was used to compare MySQL Cluster 7.2 performance to 7.1 across an 8-node Intel Xeon x5670-based cluster of dual socket commodity servers (6 cores each). As the results demonstrate, MySQL Cluster 7.2 delivers over 8x higher performance per data nodes than MySQL Cluster 7.1. More details of this and other benchmarks will be published in a new whitepaper – coming soon, so stay tuned! In a following blog post, I’ll provide recommendations on optimum thread configurations for different types of server processor. You can also learn more from the Best Practices Guide to Optimizing Performance of MySQL Cluster Conclusion MySQL Cluster has achieved a range of impressive benchmark results, and set in context with the previous 7.1 release, is able to deliver over 8x higher performance per node. As a result, the multi-threaded data node extensions not only serve to increase performance of MySQL Cluster, they also enable users to achieve significantly improved levels of utilization from current and future generations of massively multi-core, multi-thread processor designs.

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• MySQL Cluster 7.3 Labs Release – Foreign Keys Are In!

  - by Mat Keep

  0 0 1 1097 6254 Homework 52 14 7337 14.0 Normal 0 false false false EN-US JA X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:Cambria; mso-ascii-font-family:Cambria; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Cambria; mso-hansi-theme-font:minor-latin; mso-ansi-language:EN-US;} Summary (aka TL/DR): Support for Foreign Key constraints has been one of the most requested feature enhancements for MySQL Cluster. We are therefore extremely excited to announce that Foreign Keys are part of the first Labs Release of MySQL Cluster 7.3 – available for download, evaluation and feedback now! (Select the mysql-cluster-7.3-labs-June-2012 build) In this blog, I will attempt to discuss the design rationale, implementation, configuration and steps to get started in evaluating the first MySQL Cluster 7.3 Labs Release. Pace of Innovation It was only a couple of months ago that we announced the General Availability (GA) of MySQL Cluster 7.2, delivering 1 billion Queries per Minute, with 70x higher cross-shard JOIN performance, Memcached NoSQL key-value API and cross-data center replication.  This release has been a huge hit, with downloads and deployments quickly reaching record levels. The announcement of the first MySQL Cluster 7.3 Early Access lab release at today's MySQL Innovation Day event demonstrates the continued pace in Cluster development, and provides an opportunity for the community to evaluate and feedback on new features they want to see. What’s the Plan for MySQL Cluster 7.3? Well, Foreign Keys, as you may have gathered by now (!), and this is the focus of this first Labs Release. As with MySQL Cluster 7.2, we plan to publish a series of preview releases for 7.3 that will incrementally add new candidate features for a final GA release (subject to usual safe harbor statement below*), including: - New NoSQL APIs; - Features to automate the configuration and provisioning of multi-node clusters, on premise or in the cloud; - Performance and scalability enhancements; - Taking advantage of features in the latest MySQL 5.x Server GA. Design Rationale MySQL Cluster is designed as a “Not-Only-SQL” database. It combines attributes that enable users to blend the best of both relational and NoSQL technologies into solutions that deliver web scalability with 99.999% availability and real-time performance, including: Concurrent NoSQL and SQL access to the database; Auto-sharding with simple scale-out across commodity hardware; Multi-master replication with failover and recovery both within and across data centers; Shared-nothing architecture with no single point of failure; Online scaling and schema changes; ACID compliance and support for complex queries, across shards. Native support for Foreign Key constraints enables users to extend the benefits of MySQL Cluster into a broader range of use-cases, including: - Packaged applications in areas such as eCommerce and Web Content Management that prescribe databases with Foreign Key support. - In-house developments benefiting from Foreign Key constraints to simplify data models and eliminate the additional application logic needed to maintain data consistency and integrity between tables. Implementation The Foreign Key functionality is implemented directly within MySQL Cluster’s data nodes, allowing any client API accessing the cluster to benefit from them – whether using SQL or one of the NoSQL interfaces (Memcached, C++, Java, JPA or HTTP/REST.) The core referential actions defined in the SQL:2003 standard are implemented: CASCADE RESTRICT NO ACTION SET NULL In addition, the MySQL Cluster implementation supports the online adding and dropping of Foreign Keys, ensuring the Cluster continues to serve both read and write requests during the operation. An important difference to note with the Foreign Key implementation in InnoDB is that MySQL Cluster does not support the updating of Primary Keys from within the Data Nodes themselves - instead the UPDATE is emulated with a DELETE followed by an INSERT operation. Therefore an UPDATE operation will return an error if the parent reference is using a Primary Key, unless using CASCADE action, in which case the delete operation will result in the corresponding rows in the child table being deleted. The Engineering team plans to change this behavior in a subsequent preview release. Also note that when using InnoDB "NO ACTION" is identical to "RESTRICT". In the case of MySQL Cluster “NO ACTION” means “deferred check”, i.e. the constraint is checked before commit, allowing user-defined triggers to automatically make changes in order to satisfy the Foreign Key constraints. Configuration There is nothing special you have to do here – Foreign Key constraint checking is enabled by default. If you intend to migrate existing tables from another database or storage engine, for example from InnoDB, there are a couple of best practices to observe: 1. Analyze the structure of the Foreign Key graph and run the ALTER TABLE ENGINE=NDB in the correct sequence to ensure constraints are enforced 2. Alternatively drop the Foreign Key constraints prior to the import process and then recreate when complete. Getting Started Read this blog for a demonstration of using Foreign Keys with MySQL Cluster.  You can download MySQL Cluster 7.3 Labs Release with Foreign Keys today - (select the mysql-cluster-7.3-labs-June-2012 build) If you are new to MySQL Cluster, the Getting Started guide will walk you through installing an evaluation cluster on a singe host (these guides reflect MySQL Cluster 7.2, but apply equally well to 7.3) Post any questions to the MySQL Cluster forum where our Engineering team will attempt to assist you. Post any bugs you find to the MySQL bug tracking system (select MySQL Cluster from the Category drop-down menu) And if you have any feedback, please post them to the Comments section of this blog. Summary MySQL Cluster 7.2 is the GA, production-ready release of MySQL Cluster. This first Labs Release of MySQL Cluster 7.3 gives you the opportunity to preview and evaluate future developments in the MySQL Cluster database, and we are very excited to be able to share that with you. Let us know how you get along with MySQL Cluster 7.3, and other features that you want to see in future releases. * Safe Harbor Statement This information is intended to outline our general product direction. It is intended for information purposes only, and may not be incorporated into any contract. It is not a commitment to deliver any material, code, or functionality, and should not be relied upon in making purchasing decisions. The development, release, and timing of any features or functionality described for Oracle’s products remains at the sole discretion of Oracle.

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• Guide to MySQL & NoSQL, Webinar Q&A

  - by Mat Keep

  0 0 1 959 5469 Homework 45 12 6416 14.0 Normal 0 false false false EN-US JA X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:Cambria; mso-ascii-font-family:Cambria; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Cambria; mso-hansi-theme-font:minor-latin; mso-ansi-language:EN-US;} Yesterday we ran a webinar discussing the demands of next generation web services and how blending the best of relational and NoSQL technologies enables developers and architects to deliver the agility, performance and availability needed to be successful. Attendees posted a number of great questions to the MySQL developers, serving to provide additional insights into areas like auto-sharding and cross-shard JOINs, replication, performance, client libraries, etc. So I thought it would be useful to post those below, for the benefit of those unable to attend the webinar. Before getting to the Q&A, there are a couple of other resources that maybe useful to those looking at NoSQL capabilities within MySQL: - On-Demand webinar (coming soon!) - Slides used during the webinar - Guide to MySQL and NoSQL whitepaper  - MySQL Cluster demo, including NoSQL interfaces, auto-sharing, high availability, etc.  So here is the Q&A from the event  Q. Where does MySQL Cluster fit in to the CAP theorem? A. MySQL Cluster is flexible. A single Cluster will prefer consistency over availability in the presence of network partitions. A pair of Clusters can be configured to prefer availability over consistency. A full explanation can be found on the MySQL Cluster & CAP Theorem blog post.  Q. Can you configure the number of replicas? (the slide used a replication factor of 1) Yes. A cluster is configured by an .ini file. The option NoOfReplicas sets the number of originals and replicas: 1 = no data redundancy, 2 = one copy etc. Usually there's no benefit in setting it >2. Q. Interestingly most (if not all) of the NoSQL databases recommend having 3 copies of data (the replication factor).    Yes, with configurable quorum based Reads and writes. MySQL Cluster does not need a quorum of replicas online to provide service. Systems that require a quorum need > 2 replicas to be able to tolerate a single failure. Additionally, many NoSQL systems take liberal inspiration from the original GFS paper which described a 3 replica configuration. MySQL Cluster avoids the need for a quorum by using a lightweight arbitrator. You can configure more than 2 replicas, but this is a tradeoff between incrementally improved availability, and linearly increased cost. Q. Can you have cross node group JOINS? Wouldn't that run into the risk of flooding the network? MySQL Cluster 7.2 supports cross nodegroup joins. A full cross-join can require a large amount of data transfer, which may bottleneck on network bandwidth. However, for more selective joins, typically seen with OLTP and light analytic applications, cross node-group joins give a great performance boost and network bandwidth saving over having the MySQL Server perform the join. Q. Are the details of the benchmark available anywhere? According to my calculations it results in approx. 350k ops/sec per processor which is the largest number I've seen lately The details are linked from Mikael Ronstrom's blog The benchmark uses a benchmarking tool we call flexAsynch which runs parallel asynchronous transactions. It involved 100 byte reads, of 25 columns each. Regarding the per-processor ops/s, MySQL Cluster is particularly efficient in terms of throughput/node. It uses lock-free minimal copy message passing internally, and maximizes ID cache reuse. Note also that these are in-memory tables, there is no need to read anything from disk. Q. Is access control (like table) planned to be supported for NoSQL access mode? Currently we have not seen much need for full SQL-like access control (which has always been overkill for web apps and telco apps). So we have no plans, though especially with memcached it is certainly possible to turn-on connection-level access control. But specifically table level controls are not planned. Q. How is the performance of memcached APi with MySQL against memcached+MySQL or any other Object Cache like Ecache with MySQL DB? With the memcache API we generally see a memcached response in less than 1 ms. and a small cluster with one memcached server can handle tens of thousands of operations per second. Q. Can .NET can access MemcachedAPI? Yes, just use a .Net memcache client such as the enyim or BeIT memcache libraries. Q. Is the row level locking applicable when you update a column through memcached API? An update that comes through memcached uses a row lock and then releases it immediately. Memcached operations like "INCREMENT" are actually pushed down to the data nodes. In most cases the locks are not even held long enough for a network round trip. Q. Has anyone published an example using something like PHP? I am assuming that you just use the PHP memcached extension to hook into the memcached API. Is that correct? Not that I'm aware of but absolutely you can use it with php or any of the other drivers Q. For beginner we need more examples. Take a look here for a fully worked example Q. Can I access MySQL using Cobol (Open Cobol) or C and if so where can I find the coding libraries etc? A. There is a cobol implementation that works well with MySQL, but I do not think it is Open Cobol. Also there is a MySQL C client library that is a standard part of every mysql distribution Q. Is there a place to go to find help when testing and/implementing the NoSQL access? If using Cluster then you can use the [email protected] alias or post on the MySQL Cluster forum Q. Are there any white papers on this?  Yes - there is more detail in the MySQL Guide to NoSQL whitepaper If you have further questions, please don’t hesitate to use the comments below!

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• Clarity is important, both in question and in answer.

  - by gerrylowry

  clarity is important ... i'm often reminded of the Clouseau movie in which Peter Sellers as Chief Inspector Clouseau asks a hotel clerk "Does your dog bite?" ... the clerk answers "no" ... after Clouseau has been bitten by the dog, he looks at the hotel clerk who says "That's not my dog".  Clarity is important, both in question and in answer. i've been a member of forums.asp.net since 2008 ... like many of my peers at forums.asp.net, i've answered my fair share of questions. FWIW, the purpose of this, my first web log post to http://weblogs.asp.net/gerrylowry is to help new members ask better questions and in turn get better answers. TIMTOWTDI  =.  there is more than one way to do it imho, the best way to ask a question in any forum, or even person to person, is to first formulate your question and then ask yourself to answer your own question. Things to consider when asking (the more complete your question, the more likely you'll get the answer you require): -- have you searched Google and/or your favourite search engine(s) before posting your question to forums.asp.net; examples: site:msdn.microsoft.com entity framework 5.0 c#http://lmgtfy.com/?q=site%3Amsdn.microsoft.com+entity+framework+5.0+c%23 site:forums.asp.net MVC tutorial c#http://lmgtfy.com/?q=site%3Aforums.asp.net+MVC+tutorial+c%23 -- are you asking your question in the correct forum?  look at the forums' descriptions at http://forums.asp.net/; examples: Getting Started If you have a general ASP.NET question on a topic that's not covered by one of the other more specific forums - ask it here. MVC Discussions regarding ASP.NET Model-View-Controller (MVC) C# Questions about using C# for ASP.NET development Note:  if your question pertains more to c# than to MVC, choosing the C# forum is likely to be more appropriate. -- is your post subject clear and concise, yet not too vague? compare these three subjects (all three had something to do with GridView):     (1)    please help     (2)    gridview      (3)    How to show newline in GridView  -- have you clearly explained your scenario? compare:  my leg hurts   with   when i walk too much, my right knee hurts in the knee joint  compare:  my code does not work    with    when i enter a date as 2012-11-8, i get a FormatException -- have you checked your spelling, your grammar, and your English? for better or worse, English is the language of forums.asp.net ... many of the currently 170000++ forums.asp.net are not native speakers of English; that's okay ... however, there are times when choosing the more appropriate words will likely get one a better answer; fortunately, there are web tools to help you formulate your question, for example, http://translate.google.com/.  -- have you provided relevant information about your environment? here are a few examples ... feel free to include other items to your question ... rule of thumb:  if you think a given detail is relevant, it likely is -- what technology are you using?    ASP.NET MVC 4, ASP.NET MVC 3, WebForms, ...  -- what version of Visual Studio are you using?  vs2012 (ultimate, professional, express), vs2010, vs2008 ... -- are you hosting your own website?  are you using a shared hosting service? -- are you experience difficulties in just one browser? more than one browser? -- what browser version(s) are you using?   ie8? ie9? ... -- what is your operating system?     win8, win7, vista, XP, server 2008 R2 ... -- what is your database?   SQL Server 2008 R2, ss2005, MySQL, Oracle, ... -- what is your web server?  iis 7.5, iis 6, .... -- have you provided enough information for someone to be able to answer your question? Here's an actual example from an O.P. that i hope is self-explanatory: I'm trying to make a simple calculator when i write the code in windows application it worked when i tried it in web application it doesn't work and there are no errors what should i do ??!! -- have you included unnecessary information? more than once, i've seen the O.P. (original post, original poster) include many extra lines of code that were not relevant to the actual question; the more unnecessary code that you include, the less likely your volunteer peers will be motivated to donate their time to help you. -- have you asked the question that you want answered? "Does this dog bite?" -- are your expectations reasonable? -- generally, persons who are going to answer your questions are your peers ... they are unpaid volunteers ... -- are you looking for help with your homework, work assignment, or hobby? or, are you expecting someone else to do your work for you?  -- do you expect a complete solution or are you simply looking for guidance and direction? -- you are likely to get more help by first making a reasonable effort to help yourself first Clarity is important, both in question and in answer. if you are answering someone else's question, please remember that clear answers are just as important as clear questions; would you understand your own answer? Things to consider when answering: -- have you tested your code example?  if you have, say so; if you've not tested your code example, also say so -- imho, it's okay to guess as long as you clearly state that you're guessing ... sometimes a wrong guess can still help the O.P. find her/his way to the right answer -- meanness does not contribute to being helpful; sometimes one may become frustrated with the O.P. and/or others participating in a thread, if that happens to you, be kind regardless; speaking from my own experience, at least once i've allowed myself to be frustrated into writing something inappropriate that i've regretted later ... being a meany does not feel good ... being kind and helpful feels fantastic! Tip:  before asking your question, read more than a few existing questions and answers to get a sense of how your peers ask and answer questions. Gerry P.S.:  try to avoid necroposting and piggy backing. necroposting is adding to an old post, especially one that was resolved months ago. piggy backing is adding your own question to someone else's thread.

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• H1 Visa interview tips–What you must know before attending the interview?

  - by Gopinath

  USA’s H1 visa allows highly qualified professionals from other countries to work in America. Many IT professionals in India aspire to go to USA on H1 and work for their clients. Recently I had a chance to study H1 visa process to help one of my friends and I would like to share what I learned. With the assumption that your H1 petition is approved and you got an interview scheduled at US Embassy for your visa stamping, here are tips you must know before attending the interview Dress Code – Formals Say no to casuals or any fancy dress when you attend the interview. It’s not a party or friends home you are visiting. Consider H1 Visa interview as your job interview and dress up in formals. There is no option B for your, you must be in formals. A plain formal shirt with a matching pant is suggested for men. Tie and Suit would not be required, but if you are a professional at management level you can consider wearing suit. Women can wear either formal Salwar or formal pant-shirt. Avoid heavy jewellery, wear what is must as per your tradition or culture. Body Language -  Smile on your face Your body language reflects what you are and what’s going on in your mind. Don’t be nervous or restless, be relaxed and wear a beautiful smile on your face. A smile is a curve that sets everything straight. When you are called for the interview, greet the interviewer with a beautiful smile. Say Good Morning/Afternoon/Evening depending on time you are visiting them. Whenever appropriate say Thank You. Generally American professionals are very friendly people and they reciprocate for your greetings. Make sure that you make them comfortable to start the interview. Carry original documents in a separate folder I don’t want to talk much about the documents that are required for your H1B interview as it’s big subject on it’s own and it requires a separate post. I assume that your consultant or employer helped you in gathering all the required documents like – petition, DS 160 forms, education & job related documents, resume, interview call letters, client letters, etc. For all the documents you are going to submit at the interview make sure that you have originals in a separate folder.  If required interviewer may ask you show the originals of any of the document you submitted for visa processing. Don’t mix the original documents with the documents you need to submit for interview. Have a separate folder for them. For those who are going to stamping along with their spouse and children, they need to carry few extra original documents like – marriage certificate, marriage photos(30 numbers)/album, birth certificates, passports, education and profession related certificates of the spouse and children. Know your role & responsibilities The interviewer will ask you questions on your roles and responsibilities at client location. Be clear what is your day to day tasks at client place and prepared to face detailed questions on the same. When asked explain clearly and also make sure what you say is inline with what is mentioned in your petition and client invitation letter. At times they may ask you questions specific to the project/technology you are going to work. So doing some homework in this area will help you easily answer the questions. Failing to answer basic questions on your role & responsibilities may result in rejection. You work for your Employer at Client location but NOT FOR CLIENT One of the important things to keep in mind that you work for your employer and you are being deputed to client location on a work visa.  Your employer is going to be solely responsible for your salary, work, promotion, pay hikes or what so ever during your stay at USA. Your client will not be responsible for anything. Lets say you are employed with Company X in India and they are applying for H1B to work at your client(ex: Microsoft) in USA, you must keep in my mind that Microsoft is not your employer. Microsoft will not pay your salaries or responsible for any employment related activities. Company X will be solely responsible for all your employer related activities. If you don’t get this correctly and say to Visa interviewer that your client is responsible, then you may get into troubles. Know your client It’s always good to know the clients with whom you are going to work in USA and their business. If your client is a well know organisation then you may not get many questions from interviewer else you need to be well prepared to provide details like – nature of business, location, size of the organisation, etc.  Get to know the basic details about your client and be confident while providing those details to the interviewer. Also make sure that you never talk about any confidential details of your client projects and business. Revealing confidential details of your client may land your job itself in soup. Make sure that your spouse is also in sync with you If you’ve applied a H4 visa for your spouse along with your H1, make sure that spouse is in sync with you. Your spouse also should know the basic details of your job, your employer, client and location where you will be travelling. Your spouse should also be prepared to answers questions related to marriage, their profession(if working), kids, education, etc. Interviewers will try to asses your spouse communication skills, whereabouts while staying in USA and would they prefer to work USA or not. On H4, which is a dependent visa, your spouse is not allowed to work in USA and at any point your spouse should not show the intentions to search for work in USA. Less luggage more comfort You would have definitely heard that there are lot of restrictions on what you can carry along with you to an US Embassy while attending the interview. To be frank it’s not good to say there are many restrictions, but there are a hell a lot of restrictions. There are unbelievable restrictions and it’s for the safety of everyone. You are not allowed to carry mobile phones, CD/DVDs, USBs, bank cards, cameras, cosmetics, food(except baby food), water, wallets, backpacks, sealed covers, etc. Trust me most of the things we carry with us regularly every day are not allowed inside. As there are 100s of restrictions, it would be easier if you understand what you can carry along with you and just carry them alone. Ask your employer/consultant to provide you a checklist of items that you can carry. Most what you would require are H1B related documents provided by the employer/consultant Photographs All original documents supporting your H1B Passports Some cash for your travel expenses (avoid coins) Any important phone number / details written in a paper(like your cab driver number, etc.) If you carry restricted stuff then you will be stopped at security checks, you have to find people who can safely keep all the restricted items. Due to heavy restrictions in and around the US Embassy you will not find any  place to keep your luggage. So just carry the bare minimum things required so that you feel more comfortable. Useful Links THE U.S. NON IMMIGRANT VISA APPLICATION PROCESS U.S VISA SECURITY REGULATIONS GENERAL FAQS Hope this information is helpful to you and best of luck for your interview. Creative commons Image credit: Flickr/ alexfrance, vinothchandar. hughelectronic, architratan, striatic

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