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  • forks in C - exercise

    - by Zka
    I try to repeat and learn more advanced uses and options when cutting trees with forks in the jungle of C. But foolishly I find an example which should be very easy as I have worked with forks before and even written some code, but i can't understand it fully. Here comes : main() { if (fork() == 0) { if (fork() == 0) { printf("3"); } else if ((wait(NULL)) > 0) { printf("2"); } } else { if (fork() == 0) { printf("1"); exit(0); } if (fork() == 0) { printf("4"); } } printf("0"); return 0; } Possible solutions are : 3201040 3104200 1040302 4321000 4030201 1403020 where 2, 5 and 6 are correct answers. First of all, shouldn't there be four zeroes in the output? Second... How does one come to the solution at all? Been doing this on paper for almost an hour and I'm not even close to understanding why the given solution are more correct than the false ones (except for nr3 as it can't end with 2 since a 0 must follow). Anyone with his forks in check who can offer some good explanation?

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  • F# exercise help - Beginner

    - by bobjink
    I hope you can help me with these exercises I have been stuck with. I am not in particular looking for the answers. Tips that help me solve them myself are just as good :) 1. Write a function implode : char list - string so that implode s returns the characters concatenated into a string: let implode (cArray:char list) = List.foldBack (+) 0 cArray;; Error. I am thinking that i need to cast every char to strings before I do the above. I bet however, that there is a much simpler and better solution. 2. Write a function palindrome : string - bool, so that palindrome s returns true if the string s is a palindrome let isIdentical cArray1 cArray2 = (cArray1 = cArray2);; let palinDrome (word:string) = isIdentical(word.ToCharArray(), Array.rev(word.ToCharArray()));; I get the value: val palinDrome : string - (char [] * char [] - bool), which is not what I want. 3. Write a function combinePair : int list - int list so that combinePair xs returns the list with elements from xs combined into pairs. If xs contains an odd number of elements, then the last element is thrown away: I have no idea for this one.

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  • Refactoring exercise with generics

    - by Berryl
    I have a variation on a Quantity (Fowler) class that is designed to facilitate conversion between units. The type is declared as: public class QuantityConvertibleUnits<TFactory> where TFactory : ConvertableUnitFactory, new() { ... } In order to do math operations between dissimilar units, I convert the right hand side of the operation to the equivalent Quantity of whatever unit the left hand side is in, and do the math on the amount (which is a double) before creating a new Quantity. Inside the generic Quantity class, I have the following: protected static TQuantity _Add<TQuantity>(TQuantity lhs, TQuantity rhs) where TQuantity : QuantityConvertibleUnits<TFactory>, new() { var toUnit = lhs.ConvertableUnit; var equivalentRhs = _Convert<TQuantity>(rhs.Quantity, toUnit); var newAmount = lhs.Quantity.Amount + equivalentRhs.Quantity.Amount; return _Convert<TQuantity>(new Quantity(newAmount, toUnit.Unit), toUnit); } protected static TQuantity _Subtract<TQuantity>(TQuantity lhs, TQuantity rhs) where TQuantity : QuantityConvertibleUnits<TFactory>, new() { var toUnit = lhs.ConvertableUnit; var equivalentRhs = _Convert<TQuantity>(rhs.Quantity, toUnit); var newAmount = lhs.Quantity.Amount - equivalentRhs.Quantity.Amount; return _Convert<TQuantity>(new Quantity(newAmount, toUnit.Unit), toUnit); } ... same for multiply and also divide I need to get the typing right for a concrete Quantity, so an example of an add op looks like: public static ImperialLengthQuantity operator +(ImperialLengthQuantity lhs, ImperialLengthQuantity rhs) { return _Add(lhs, rhs); } The question is those verbose methods in the Quantity class. The only change between the code is the math operator (+, -, *, etc.) so it seems that there should be a way to refactor them into a common method, but I am just not seeing it. How can I refactor that code? Cheers, Berryl

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  • c++ exercise question

    - by Djecua
    in need of help on a C++ program that will help a deli owner help her customers.Prompt the user for the number of bagels.if then calculate the customers payment two ways. first it finds the price of the smallest multiple of 13 bagels that is closet to the customer's order. it then calculates the price of the customer's order so that the customer's payment is the smallest amount possible with the customer getting the exact number of bagels ordered. if the first method is the smallest amount the program outputs the number of bagels the customer will receive along with the dollar amount owed and the dollar amount saved. otherwise just print the number of bagels received the dollar amount owed $ 3.80 for a dozen bagels (13 bagels) half a dozen(6 bagels) sing bagel cost $.50 owner of the deli is a honest merchant, customers always get the best price on an order, even if they get more bagels than ordered, for example a customer that orders 10 bagels would pay $ 4.60 (2.60 for a half dozen bagels plus $2.00 for 4 single bagels.merchant gives her customer 13 bagels saving the customer $0.80 If someone can example to me how would i design to give customer extra bagels and how to calculate cost.

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  • Solve Physics exercise by brute force approach..

    - by Nils
    Being unable to reproduce a given result. (either because it's wrong or because I was doing something wrong) I was asking myself if it would be easy to just write a small program which takes all the constants and given number and permutes it with a possible operators (* / - + exp(..)) etc) until the result is found. Permutations of n distinct objects with repetition allowed is n^r. At least as long as r is small I think you should be able to do this. I wonder if anybody did something similar here..

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  • What are some IT jobs where you don't sit at a desk for 8-10hrs a day?

    - by zippy
    Like a lot of people in IT I sit at a desk for 8-10hrs/day working on stuff that needs to get done "now". That usually means eating unhealthy lunches at my desk, and sometimes dinner too. This does terrible things to your health. I have been trying to work some exercise into the workday but I was thinking it would be great if I worked somewhere where I was exercising all the time (walking around, lifting servers, etc.). Does anyone have a job in IT (or know someone) where you are actually moving around (not sitting) doing something for most of the day?

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  • Which method should I use ?

    - by Ivan
    I want to do this exercise but I don't know exactly which method should I use for an exercise like this and what data will I use to test the algorithm. The driving distance between Perth and Adelaide is 1996 miles. On the average, the fuel consumption of a 2.0 litre 4 cylinder car is 8 litres per 100 kilometres. The fuel tank capacity of such a car is 60 litres. Design and implement a JAVA program that prompts for the fuel consumption and fuel tank capacity of the aforementioned car. The program then displays the minimum number of times the car’s fuel tank has to be filled up to drive from Perth to Adelaide. Note that 62 miles is equal to 100 kilometres. What data will you use to test that your algorithm works correctly?

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  • Should I give the answer to a failed interview coding exercise?

    - by GlenH7
    We had a senior level interview candidate fail a nuance of the FizzBuzz question*. I mean, really, utterly, completely, failed the question - not even close. I even coached him through to thinking about using a loop and that 3 and 5 were really worth considering as special cases. He blew it. Just for QA purposes, I gave the same exact question to three teammates; gave them 5 minutes; and then came back to collect their pseudo-code. All of them nailed it and hadn't seen the question before. Two asked what the trick was... On a different logic exercise, the candidate showed some understanding of some of the features available within the language he chose to use (C#). So it's not as if he had never written a line of code. But his logic still stunk. My question is whether or not I should have given him the answer to the logic questions. He knew he blew them, and acknowledged it later in the interview. On the other hand, he never asked for the answer or what I was expecting to see. I know coding exercises can be used to set candidates up for failure (again, see second link from above). And I really tried to help him home in on answering the core of the question. But this was a senior level candidate and Fizz-Buzz is, frankly, ridiculously easy even with accounting for interview jitters. I felt like I should have shown him a way of solving the problem so that he could at least learn from the experience. But again, he didn't ask. What's the right way to handle that situation? *Okay, that's not the link to the actual FizzBuzz question, but it is a good P.SE discussion around FizzBuzz and links to the various aspects of it.

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  • How to make the constructor for the following exercise in c++?

    - by user40630
    This is the exercise I?m trying to solve. It's from C++, How to program book from Deitel and it's my homework. (Card Shuffling and Dealing) Create a program to shuffle and deal a deck of cards. The program should consist of class Card, class DeckOfCards and a driver program. Class Card should provide: a) Data members face and suit of type int. b) A constructor that receives two ints representing the face and suit and uses them to initialize the data members. c) Two static arrays of strings representing the faces and suits. d) A toString function that returns the Card as a string in the form “face of suit.” You can use the + operator to concatenate strings. Class DeckOfCards should contain: a) A vector of Cards named deck to store the Cards. b) An integer currentCard representing the next card to deal. c) A default constructor that initializes the Cards in the deck. The constructor should use vector function push_back to add each Card to the end of the vector after the Card is created and initialized. This should be done for each of the 52 Cards in the deck. d) A shuffle function that shuffles the Cards in the deck. The shuffle algorithm should iterate through the vector of Cards. For each Card, randomly select another Card in the deck and swap the two Cards. e) A dealCard function that returns the next Card object from the deck. f) A moreCards function that returns a bool value indicating whether there are more Cards to deal. The driver program should create a DeckOfCards object, shuffle the cards, then deal the 52 cards. The problem I'm facing is that I don't know exactly how to make the constructor for the second class. See description commented in the code bellow. #include <iostream> #include <vector> using namespace std; /* * */ //Class card. No problems here. class Card { public: Card(int, int); string toString(); private: int suit, face; static string faceNames[13]; static string suitNames[4]; }; string Card::faceNames[13] = {"Ace","Two","Three","Four","Five","Six","Seven","Eight","Nine","Ten","Queen","Jack","King"}; string Card::suitNames[4] = {"Diamonds","Clubs","Hearts","Spades"}; string Card::toString() { return faceNames[face]+" of "+suitNames[suit]; } Card::Card(int f, int s) :face(f), suit(s) { } /*The problem begins here. This class should create(when and object for it is created) a copy of the vector deck, right? But how exactly are these vector cards be initialized? I'll explain better in the constructor definition bellow.*/ class DeckOfCards { public: DeckOfCards(); void shuffleCards(); Card dealCard(); bool moreCards(); private: vector<Card> deck(52); int currentCard; }; int main(int argc, char** argv) { return 0; } DeckOfCards::DeckOfCards() { //This is where I'm stuck. I can't figure out how to set each of the 52 cards of the vector deck to have a specific suit and face every one of them, by using only the constructor of the Card class. //What you see bellow was one of my attempts to solve this problem but I blocked pretty soon in the middle of it. for(int i=0; i<deck.size(); i++) { deck[i]//....There is no function to set them. They must be set when initialized. But how?? } } For easier reading: http://pastebin.com/pJeXMH0f

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  • How do I resolve this exercise on C++? [closed]

    - by user40630
    (Card Shuffling and Dealing) Create a program to shuffle and deal a deck of cards. The program should consist of class Card, class DeckOfCards and a driver program. Class Card should provide: a) Data members face and suit of type int. b) A constructor that receives two ints representing the face and suit and uses them to initialize the data members. c) Two static arrays of strings representing the faces and suits. d) A toString function that returns the Card as a string in the form “face of suit.” You can use the + operator to concatenate strings. Class DeckOfCards should contain: a) A vector of Cards named deck to store the Cards. b) An integer currentCard representing the next card to deal. c) A default constructor that initializes the Cards in the deck. The constructor should use vector function push_back to add each Card to the end of the vector after the Card is created and initialized. This should be done for each of the 52 Cards in the deck. d) A shuffle function that shuffles the Cards in the deck. The shuffle algorithm should iterate through the vector of Cards. For each Card, randomly select another Card in the deck and swap the two Cards. e) A dealCard function that returns the next Card object from the deck. f) A moreCards function that returns a bool value indicating whether there are more Cards to deal. The driver program should create a DeckOfCards object, shuffle the cards, then deal the 52 cards. This above is the exercise I'm trying to solve. I'd be very much appreciated if someone could solve it and explain it to me. The main idea of the program is quite simple. What I don't get is how to build the constructor for the class DeckOfCards and how to generate the 52 cards of the deck with different suits and faces. Untill now I've managed to do this: #include <iostream> #include <vector> using namespace std; /* * */ /* a) Data members face and suit of type int. b) A constructor that receives two ints representing the face and suit and uses them to initialize the data members. c) Two static arrays of strings representing the faces and suits. d) A toString function that returns the Card as a string in the form “face of suit.” You can use the + operator to concatenate strings. */ class Card { public: Card(int, int); string toString(); private: int suit, face; static string faceNames[13]; static string suitNames[4]; }; string Card::faceNames[13] = {"Ace","Two","Three","Four","Five","Six","Seven","Eight","Nine","Ten","Queen","Jack","King"}; string Card::suitNames[4] = {"Diamonds","Clubs","Hearts","Spades"}; string Card::toString() { return faceNames[face]+" of "+suitNames[suit]; } Card::Card(int f, int s) :face(f), suit(s) { } /* Class DeckOfCards should contain: a) A vector of Cards named deck to store the Cards. b) An integer currentCard representing the next card to deal. c) A default constructor that initializes the Cards in the deck. The constructor should use vector function push_back to add each Card to the end of the vector after the Card is created and initialized. This should be done for each of the 52 Cards in the deck. d) A shuffle function that shuffles the Cards in the deck. The shuffle algorithm should iterate through the vector of Cards. For each Card, randomly select another Card in the deck and swap the two Cards. e) A dealCard function that returns the next Card object from the deck. f) A moreCards function that returns a bool value indicating whether there are more Cards to deal. */ class DeckOfCards { public: DeckOfCards(); void shuffleCards(); Card dealCard(); bool moreCards(); private: vector<Card> deck(52); int currentCard; }; int main(int argc, char** argv) { return 0; } DeckOfCards::DeckOfCards() { //I'm stuck here I have no idea of what to take out of here. //I still don't fully get the idea of class inside class and that's turning out as a problem. I try to find a way to set the suits and faces members of the class Card but I can't figure out how. for(int i=0; i<deck.size(); i++) { deck[i]//....There is no function to set them. They must be set when initialized. But how?? } } For easier reading: http://pastebin.com/pJeXMH0f

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  • Learning Python and trying to get first two letters and last two letters of a string.

    - by Sergio Tapia
    Here's my code: # B. both_ends # Given a string s, return a string made of the first 2 # and the last 2 chars of the original string, # so 'spring' yields 'spng'. However, if the string length # is less than 2, return instead the empty string. def both_ends(s): if len(s) <= 2: return "" else: return s[0] + s[1] + s[len(s)-2] + s[len(s-1)] # +++your code here+++ return Unfortunately my program doesn't run. :( I'm sure I'm overlooking something since I'm a newbie with Python. Here's the error: > Traceback (most recent call last): File "C:\Users\Sergio\Desktop\google-python-exercises\google-python-exercises\basic\string1.py", line 120, in <module> main() File "C:\Users\Sergio\Desktop\google-python-exercises\google-python-exercises\basic\string1.py", line 97, in main test(both_ends('spring'), 'spng') File "C:\Users\Sergio\Desktop\google-python-exercises\google-python-exercises\basic\string1.py", line 44, in both_ends return s[0] + s[1] + s[len(s)-2] + s[len(s-1)] TypeError: unsupported operand type(s) for -: 'str' and 'int' Thanks for the help guys. :D

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  • Use Math class to calculate

    - by LC
    Write a JAVA program that calculates the surface area of a cylinder, C= 2( p r2) + 2 p r h, where r is the radius and h is the height of the cylinder. Allow the user to enter in a radius and a height. Format the output to three decimal places. Use the constant PI and the method pow() from the Math class. This is what I've done so far but it can not run. Can anyone help me ? import Java.util Scanner; public class Ex5 { public static void main (String[] args) { Scanner input.new Scanner(System.in); double radius,height,area; System.out.print("Please enter the radius of the Cylinder"); radius = input.nextDouble(); System.out.print("Please enter the height of the Cylinder"); height = input.nextDouble(); area = (4*Math.PI*radius)+2*Math.PIMath.POW(radius,2); System.out.println("The surface of the cylinder" + area); } }

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  • Calculate car filled up times

    - by Ivan
    Here is the question: The driving distance between Perth and Adelaide is 1996 miles. On the average, the fuel consumption of a 2.0 litre 4 cylinder car is 8 litres per 100 kilometres. The fuel tank capacity of such a car is 60 litres. Design and implement a JAVA program that prompts for the fuel consumption and fuel tank capacity of the aforementioned car. The program then displays the minimum number of times the car’s fuel tank has to be filled up to drive from Perth to Adelaide. Note that 62 miles is equal to 100 kilometres. What data will you use to test that your algorithm works correctly? Here is what I've done so far: import java.util.Scanner;// public class Ex4{ public static void main( String args[] ){ Scanner input = new Scanner( System.in ); double distance, consumption, capacity, time; distance = Math.sqrt(1996/62*100); consumption = Math.sqrt(8/100); capacity = 60; time = Math.sqrt(distance*consumption/capacity); System.out.println("The car's fuel tank need to be filled up:" + time + "times"); } } I can compile it but the problem is that the result is always 0.0, can anyone help me what's wrong with it ?

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  • How do you match only valid roman numerals with a regular expression?

    - by Daniel Magliola
    Thinking about my other problem, i decided I can't even create a regular expression that will match roman numerals (let alone a context-free grammar that will generate them) The problem is matching only valid roman numerals. Eg, 990 is NOT "XM", it's "CMXC" My problem in making the regex for this is that in order to allow or not allow certain characters, I need to look back. Let's take thousands and hundreds, for example. I can allow M{0,2}C?M (to allow for 900, 1000, 1900, 2000, 2900 and 3000). However, If the match is on CM, I can't allow following characters to be C or D (because I'm already at 900). How can I express this in a regex? If it's simply not expressible in a regex, is it expressible in a context-free grammar? Thanks for any pointers!

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  • Can someone help me compare using F# over C# in this specific example (IP Address expressions)?

    - by Phobis
    So, I am writing code to parse and IP Address expression and turn it into a regular expression that could be run against and IP Address string and return a boolean response. I wrote the code in C# (OO) and it was 110 lines of code. I am trying to compare the amount of code and the expressiveness of C# to F# (I am a C# programmer and a noob at F#). I don't want to post both the C# and F#, just because I don't want to clutter the post. If needed, I will do so. Anyway, I will give an example. Here is an expression: 192.168.0.250,244-248,108,51,7;127.0.0.1 I would like to take that and turn it into this regular expression: ((192.168.0.(250|244|245|246|247|248|108|51|7))|(127.0.0.1)) Here are some steps I am following: Operations: Break by ";" 192.168.0.250,244-248,108,51,7 127.0.0.1 Break by "." 192 168 0 250,244-248,108,51,7 Break by "," 250 244-248 108 51 7 Break by "-" 244 248 I came up with F# that produces the output. I am trying to forward-pipe through my operations listed above, as I think that would be more expressive. Can anyone make this code better? Teach me something :) open System let createItemArray (group:bool) (y:char) (items:string[]) = [| let indexes = items.Length - 1 let group = indexes > 0 && group if group then yield "(" for i in 0 .. indexes do yield items.[i].ToString() if i < indexes then yield y.ToString() if group then yield ")" |] let breakBy (group:bool) (x:string) (y:char): string[] = x.Split(y) |> createItemArray group y let breakItem (x:string) (y:char): string[] = breakBy false x y let breakGroup (x:string) (y:char): string[] = breakBy true x y let AddressExpression address:string = let builder = new System.Text.StringBuilder "(" breakGroup address ';' |> Array.collect (fun octet -> breakItem octet '.') |> Array.collect (fun options -> breakGroup options ',') |> Array.collect (fun (ranges : string) -> match (breakGroup ranges '-') with | x when x.Length > 3 -> match (Int32.TryParse(x.[1]), Int32.TryParse(x.[3])) with | ((true, a) ,(true, b)) -> [|a .. b|] |> Array.map (int >> string) |> createItemArray false '-' | _ -> [|ranges|] | _ -> [|ranges|] ) |> Array.iter (fun item -> match item with | ";" -> builder.Append ")|(" | "." -> builder.Append "\." | "," | "-" -> builder.Append "|" | _ -> builder.Append item |> ignore ) builder.Append(")").ToString() let address = "192.168.0.250,244-248,108,51,7;127.0.0.1" AddressExpression address

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  • What is a good standard exercise to learn the OO features of a language?

    - by FarmBoy
    When I'm learning a new language, I often program some mathematical functions to get used to the control flow syntax. After that, I like to implement some sorting algorithms to get used to the array/list constructs. But I don't have a standard exercise for exploring the languages OO features. Does anyone have a stock exercise for this? A good answer would naturally lend to inheritance, polymorphism, etc., for a programmer already comfortable with these concepts. An ideal answer would be one that could be communicated in a few words, without ambiguity, in the way that "implement mergesort" is completely unambiguous. (As an example, answering "design a game" is so vague as to be useless.) Any ideas? EDIT: I have to remark that the results here are somewhat ironic. 10 upvotes and (originally) 5 favorites suggest that this is a question others are interested in. Yet the most upvoted answer is one that says there is no good answer. Oh well. I think I'll look at the textbook below, I've found games useful in the past for OO.

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  • In SICP exercise 2.26 using DrScheme, why does cons return a list, instead of a pair of lists?

    - by limist
    In SICP exercise 2.26, this Scheme code is given: (define x (list 1 2 3)) (define y (list 4 5 6)) Then this cons call is given: (cons x y) I expected a pair of lists would result, ((1 2 3) (4 5 6)) but the interpreter gives, ((1 2 3) 4 5 6) ...a list with 4 elements, the first being a list. Why is y treated differently? I've tried looking up other SICP answers for an explanation, but couldn't find something satisfactory. So could any Scheme/Lisp experts please shed some light on this aspect of cons? Thanks in advance for any insight.

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  • How do I write test code to exercise a C# generic Pair<TKey, TValue> ?

    - by Scott Davies
    Hi, I am reading through Jon Skeet's "C# in Depth", first edition (which is a great book). I'm in section 3.3.3, page 84, "Implementing Generics". Generics always confuse me, so I wrote some code to exercise the sample. The code provided is: using System; using System.Collections.Generic; public sealed class Pair<TFirst, TSecond> : IEquatable<Pair<TFirst, TSecond>> { private readonly TFirst first; private readonly TSecond second; public Pair(TFirst first, TSecond second) { this.first = first; this.second = second; } ...property getters... public bool Equals(Pair<TFirst, TSecond> other) { if (other == null) { return false; } return EqualityComparer<TFirst>.Default.Equals(this.First, other.First) && EqualityComparer<TSecond>.Default.Equals(this.Second, other.Second); } My code is: class MyClass { public static void Main (string[] args) { // Create new pair. Pair thePair = new Pair(new String("1"), new String("1")); // Compare a new pair to previous pair by generating a second pair. if (thePair.Equals(new Pair(new string("1"), new string("1")))) System.Console.WriteLine("Equal"); else System.Console.WriteLine("Not equal"); } } The compiler complains: "Using the generic type 'ManningListing36.Paie' requires 2 type argument(s) CS0305" What am I doing wrong ? Thanks, Scott

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  • Oracle Solaris 11 ZFS Lab for Openworld 2012

    - by user12626122
    Preface This is the content from the Oracle Openworld 2012 ZFS lab. It was well attended - the feedback was that it was a little short - thats probably because in writing it I bacame very time-concious after the ASM/ACFS on Solaris extravaganza I ran last year which was almost too long for mortal man to finish in the 1 hour session. Enjoy. Table of Contents Exercise Z.1: ZFS Pools Exercise Z.2: ZFS File Systems Exercise Z.3: ZFS Compression Exercise Z.4: ZFS Deduplication Exercise Z.5: ZFS Encryption Exercise Z.6: Solaris 11 Shadow Migration Introduction This set of exercises is designed to briefly demonstrate new features in Solaris 11 ZFS file system: Deduplication, Encryption and Shadow Migration. Also included is the creation of zpools and zfs file systems - the basic building blocks of the technology, and also Compression which is the compliment of Deduplication. The exercises are just introductions - you are referred to the ZFS Adminstration Manual for further information. From Solaris 11 onward the online manual pages consist of zpool(1M) and zfs(1M) with further feature-specific information in zfs_allow(1M), zfs_encrypt(1M) and zfs_share(1M). The lab is easily carried out in a VirtualBox running Solaris 11 with 6 virtual 3 Gb disks to play with. Exercise Z.1: ZFS Pools Task: You have several disks to use for your new file system. Create a new zpool and a file system within it. Lab: You will check the status of existing zpools, create your own pool and expand it. Your Solaris 11 installation already has a root ZFS pool. It contains the root file system. Check this: root@solaris:~# zpool list NAME SIZE ALLOC FREE CAP DEDUP HEALTH ALTROOT rpool 15.9G 6.62G 9.25G 41% 1.00x ONLINE - root@solaris:~# zpool status pool: rpool state: ONLINE scan: none requested config: NAME STATE READ WRITE CKSUM rpool ONLINE 0 0 0 c3t0d0s0 ONLINE 0 0 0 errors: No known data errors Note the disk device the root pool is on - c3t0d0s0 Now you will create your own ZFS pool. First you will check what disks are available: root@solaris:~# echo | format Searching for disks...done AVAILABLE DISK SELECTIONS: 0. c3t0d0 <ATA-VBOX HARDDISK-1.0 cyl 2085 alt 2 hd 255 sec 63> /pci@0,0/pci8086,2829@d/disk@0,0 1. c3t2d0 <ATA-VBOX HARDDISK-1.0 cyl 1534 alt 2 hd 128 sec 32> /pci@0,0/pci8086,2829@d/disk@2,0 2. c3t3d0 <ATA-VBOX HARDDISK-1.0 cyl 1534 alt 2 hd 128 sec 32> /pci@0,0/pci8086,2829@d/disk@3,0 3. c3t4d0 <ATA-VBOX HARDDISK-1.0 cyl 1534 alt 2 hd 128 sec 32> /pci@0,0/pci8086,2829@d/disk@4,0 4. c3t5d0 <ATA-VBOX HARDDISK-1.0 cyl 1534 alt 2 hd 128 sec 32> /pci@0,0/pci8086,2829@d/disk@5,0 5. c3t6d0 <ATA-VBOX HARDDISK-1.0 cyl 1534 alt 2 hd 128 sec 32> /pci@0,0/pci8086,2829@d/disk@6,0 6. c3t7d0 <ATA-VBOX HARDDISK-1.0 cyl 1534 alt 2 hd 128 sec 32> /pci@0,0/pci8086,2829@d/disk@7,0 Specify disk (enter its number): Specify disk (enter its number): The root disk is numbered 0. The others are free for use. Try creating a simple pool and observe the error message: root@solaris:~# zpool create mypool c3t2d0 c3t3d0 'mypool' successfully created, but with no redundancy; failure of one device will cause loss of the pool So destroy that pool and create a mirrored pool instead: root@solaris:~# zpool destroy mypool root@solaris:~# zpool create mypool mirror c3t2d0 c3t3d0 root@solaris:~# zpool status mypool pool: mypool state: ONLINE scan: none requested config: NAME STATE READ WRITE CKSUM mypool ONLINE 0 0 0 mirror-0 ONLINE 0 0 0 c3t2d0 ONLINE 0 0 0 c3t3d0 ONLINE 0 0 0 errors: No known data errors Back to topExercise Z.2: ZFS File Systems Task: You have to create file systems for later exercises. You can see that when a pool is created, a file system of the same name is created: root@solaris:~# zfs list NAME USED AVAIL REFER MOUNTPOINT mypool 86.5K 2.94G 31K /mypool Create your filesystems and mountpoints as follows: root@solaris:~# zfs create -o mountpoint=/data1 mypool/mydata1 The -o option sets the mount point and automatically creates the necessary directory. root@solaris:~# zfs list mypool/mydata1 NAME USED AVAIL REFER MOUNTPOINT mypool/mydata1 31K 2.94G 31K /data1 Back to top Exercise Z.3: ZFS Compression Task:Try out different forms of compression available in ZFS Lab:Create 2nd filesystem with compression, fill both file systems with the same data, observe results You can see from the zfs(1) manual page that there are several types of compression available to you, set with the property=value syntax: compression=on | off | lzjb | gzip | gzip-N | zle Controls the compression algorithm used for this dataset. The lzjb compression algorithm is optimized for performance while providing decent data compression. Setting compression to on uses the lzjb compression algorithm. The gzip compression algorithm uses the same compression as the gzip(1) command. You can specify the gzip level by using the value gzip-N where N is an integer from 1 (fastest) to 9 (best compression ratio). Currently, gzip is equivalent to gzip-6 (which is also the default for gzip(1)). Create a second filesystem with compression turned on. Note how you set and get your values separately: root@solaris:~# zfs create -o mountpoint=/data2 mypool/mydata2 root@solaris:~# zfs set compression=gzip-9 mypool/mydata2 root@solaris:~# zfs get compression mypool/mydata1 NAME PROPERTY VALUE SOURCE mypool/mydata1 compression off default root@solaris:~# zfs get compression mypool/mydata2 NAME PROPERTY VALUE SOURCE mypool/mydata2 compression gzip-9 local Now you can copy the contents of /usr/lib into both your normal and compressing filesystem and observe the results. Don't forget the dot or period (".") in the find(1) command below: root@solaris:~# cd /usr/lib root@solaris:/usr/lib# find . -print | cpio -pdv /data1 root@solaris:/usr/lib# find . -print | cpio -pdv /data2 The copy into the compressing file system takes longer - as it has to perform the compression but the results show the effect: root@solaris:/usr/lib# zfs list NAME USED AVAIL REFER MOUNTPOINT mypool 1.35G 1.59G 31K /mypool mypool/mydata1 1.01G 1.59G 1.01G /data1 mypool/mydata2 341M 1.59G 341M /data2 Note that the available space in the pool is shared amongst the file systems. This behavior can be modified using quotas and reservations which are not covered in this lab but are covered extensively in the ZFS Administrators Guide. Back to top Exercise Z.4: ZFS Deduplication The deduplication property is used to remove redundant data from a ZFS file system. With the property enabled duplicate data blocks are removed synchronously. The result is that only unique data is stored and common componenents are shared. Task:See how to implement deduplication and its effects Lab: You will create a ZFS file system with deduplication turned on and see if it reduces the amount of physical storage needed when we again fill it with a copy of /usr/lib. root@solaris:/usr/lib# zfs destroy mypool/mydata2 root@solaris:/usr/lib# zfs set dedup=on mypool/mydata1 root@solaris:/usr/lib# rm -rf /data1/* root@solaris:/usr/lib# mkdir /data1/2nd-copy root@solaris:/usr/lib# zfs list NAME USED AVAIL REFER MOUNTPOINT mypool 1.02M 2.94G 31K /mypool mypool/mydata1 43K 2.94G 43K /data1 root@solaris:/usr/lib# find . -print | cpio -pd /data1 2142768 blocks root@solaris:/usr/lib# zfs list NAME USED AVAIL REFER MOUNTPOINT mypool 1.02G 1.99G 31K /mypool mypool/mydata1 1.01G 1.99G 1.01G /data1 root@solaris:/usr/lib# find . -print | cpio -pd /data1/2nd-copy 2142768 blocks root@solaris:/usr/lib#zfs list NAME USED AVAIL REFER MOUNTPOINT mypool 1.99G 1.96G 31K /mypool mypool/mydata1 1.98G 1.96G 1.98G /data1 You could go on creating copies for quite a while...but you get the idea. Note that deduplication and compression can be combined: the compression acts on metadata. Deduplication works across file systems in a pool and there is a zpool-wide property dedupratio: root@solaris:/usr/lib# zpool get dedupratio mypool NAME PROPERTY VALUE SOURCE mypool dedupratio 4.30x - Deduplication can also be checked using "zpool list": root@solaris:/usr/lib# zpool list NAME SIZE ALLOC FREE CAP DEDUP HEALTH ALTROOT mypool 2.98G 1001M 2.01G 32% 4.30x ONLINE - rpool 15.9G 6.66G 9.21G 41% 1.00x ONLINE - Before moving on to the next topic, destroy that dataset and free up some space: root@solaris:~# zfs destroy mypool/mydata1 Back to top Exercise Z.5: ZFS Encryption Task: Encrypt sensitive data. Lab: Explore basic ZFS encryption. This lab only covers the basics of ZFS Encryption. In particular it does not cover various aspects of key management. Please see the ZFS Adminastrion Manual and the zfs_encrypt(1M) manual page for more detail on this functionality. Back to top root@solaris:~# zfs create -o encryption=on mypool/data2 Enter passphrase for 'mypool/data2': ******** Enter again: ******** root@solaris:~# Creation of a descendent dataset shows that encryption is inherited from the parent: root@solaris:~# zfs create mypool/data2/data3 root@solaris:~# zfs get -r encryption,keysource,keystatus,checksum mypool/data2 NAME PROPERTY VALUE SOURCE mypool/data2 encryption on local mypool/data2 keysource passphrase,prompt local mypool/data2 keystatus available - mypool/data2 checksum sha256-mac local mypool/data2/data3 encryption on inherited from mypool/data2 mypool/data2/data3 keysource passphrase,prompt inherited from mypool/data2 mypool/data2/data3 keystatus available - mypool/data2/data3 checksum sha256-mac inherited from mypool/data2 You will find the online manual page zfs_encrypt(1M) contains examples. In particular, if time permits during this lab session you may wish to explore the changing of a key using "zfs key -c mypool/data2". Exercise Z.6: Shadow Migration Shadow Migration allows you to migrate data from an old file system to a new file system while simultaneously allowing access and modification to the new file system during the process. You can use Shadow Migration to migrate a local or remote UFS or ZFS file system to a local file system. Task: You wish to migrate data from one file system (UFS, ZFS, VxFS) to ZFS while mainaining access to it. Lab: Create the infrastructure for shadow migration and transfer one file system into another. First create the file system you want to migrate root@solaris:~# zpool create oldstuff c3t4d0 root@solaris:~# zfs create oldstuff/forgotten Then populate it with some files: root@solaris:~# cd /var/adm root@solaris:/var/adm# find . -print | cpio -pdv /oldstuff/forgotten You need the shadow-migration package installed: root@solaris:~# pkg install shadow-migration Packages to install: 1 Create boot environment: No Create backup boot environment: No Services to change: 1 DOWNLOAD PKGS FILES XFER (MB) Completed 1/1 14/14 0.2/0.2 PHASE ACTIONS Install Phase 39/39 PHASE ITEMS Package State Update Phase 1/1 Image State Update Phase 2/2 You then enable the shadowd service: root@solaris:~# svcadm enable shadowd root@solaris:~# svcs shadowd STATE STIME FMRI online 7:16:09 svc:/system/filesystem/shadowd:default Set the filesystem to be migrated to read-only root@solaris:~# zfs set readonly=on oldstuff/forgotten Create a new zfs file system with the shadow property set to the file system to be migrated: root@solaris:~# zfs create -o shadow=file:///oldstuff/forgotten mypool/remembered Use the shadowstat(1M) command to see the progress of the migration: root@solaris:~# shadowstat EST BYTES BYTES ELAPSED DATASET XFRD LEFT ERRORS TIME mypool/remembered 92.5M - - 00:00:59 mypool/remembered 99.1M 302M - 00:01:09 mypool/remembered 109M 260M - 00:01:19 mypool/remembered 133M 304M - 00:01:29 mypool/remembered 149M 339M - 00:01:39 mypool/remembered 156M 86.4M - 00:01:49 mypool/remembered 156M 8E 29 (completed) Note that if you had created /mypool/remembered as encrypted, this would be the preferred method of encrypting existing data. Similarly for compressing or deduplicating existing data. The procedure for migrating a file system over NFS is similar - see the ZFS Administration manual. That concludes this lab session.

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  • Can't make my WCF extension work

    - by Sergio Romero
    I have a WCF solution that consists of the following class libraries: Exercise.Services: Contains the implementation classes for the services. Exercise.ServiceProxy: Contains the classes that are instantiated in the client. Exercise.HttpHost: Contains the services (*.svc files). I'm calling the service from a console application and the "first version" works really well so I took the next step which is to create a custom ServiceHostFactory, ServiceHost, and InstanceProvider so I can use constructor injection in my services as it is explained in this article. These classes are implemented in yet another class library: 4. Exercise.StructureMapWcfExtension Now even though I've modified my service this: <%@ ServiceHost Language="C#" Debug="true" Factory="Exercise.StructureMapWcfExtension.StructureMapServiceHostFactory" Service="Exercise.Services.PurchaseOrderService" %> I always get the following exception: System.ServiceModel.CommunicationException Security negotiation failed because the remote party did not send back a reply in a timely manner. This may be because the underlying transport connection was aborted. It fails in this line of code: public class PurchaseOrderProxy : ClientBase<IPurchaseOrderService>, IPurchaseOrderService { public PurchaseOrderResponse CreatePurchaseOrder(PurchaseOrderRequest purchaseOrderRequest) { return base.Channel.CreatePurchaseOrder(purchaseOrderRequest); //Fails here } } But that is not all, I added a trace to the web.config file and this is the error that appears in the log file: System.InvalidOperationException The service type provided could not be loaded as a service because it does not have a default (parameter-less) constructor. To fix the problem, add a default constructor to the type, or pass an instance of the type to the host. So this means that my ServiceHostFactory is never being hit, I even set a breakpoint in both its constructor and its method and they never get hit. I've added a reference of the StructureMapWcfExtension library to all the other ones (even the console client), one by one to no avail. I also tried to use the option in the host's web.config file to configure the factory like so: <serviceHostingEnvironment> <serviceActivations> <add service="Exercise.Services.PurchaseOrderService" relativeAddress="PurchaseOrderService.svc" factory="Exercise.StructureMapWcfExtension.StructureMapServiceHostFactory"/> </serviceActivations> </serviceHostingEnvironment> That didn't work either. Please I need help in getting this to work so I can incorporate it to our project. Thank you. UPDATE: Here's the service host factory's code: namespace Exercise.StructureMapWcfExtension { public class StructureMapServiceHostFactory : ServiceHostFactory { private readonly Container Container; public StructureMapServiceHostFactory() { Container = new Container(); new ContainerConfigurer().Configure(Container); } protected override ServiceHost CreateServiceHost(Type serviceType, Uri[] baseAddresses) { return new StructureMapServiceHost(Container, serviceType, baseAddresses); } } public class ContainerConfigurer { public void Configure(Container container) { container.Configure(r => r.For<IPurchaseOrderFacade>().Use<PurchaseOrderFacade>()); } } }

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  • How to pass a parameter to jQuery UI dialog event handler?

    - by bebraw
    I am currently trying to hook up jQuery UI dialog so that I may use it to create new items to my page and to modify ones existing already on the page. I managed in the former. I'm currently struggling in the latter problem, however. I just cannot find a nice way to pass the item to modify to the dialog. Here's some code to illustrate the issue better. Note especially the part marked with XXX. The {{}} parts are derived from Django template syntax: $(".exercise").click(function() { $.post("{{ request.path }}", { action: "create_dialog", exercise_name: $(this).text() }, function(data) { $("#modify_exercise").html(data.content); }, "json" ); $("#modify_exercise").dialog('open'); }); $("#modify_exercise").dialog({ autoOpen: false, resizable: false, modal: true, buttons: { '{% trans 'Modify' %}': function() { var $inputs = $('#modify_exercise :input'); var post_values = {}; $inputs.each(function() { post_values[this.name] = $(this).val(); }); post_values.action = 'validate_form'; //XXX: how to get the exercise name here? post_values.exercise_name = 'foobar'; $.post('{{ request.path }}', post_values, function(data) { if( data.status == 'invalid' ) { $('#modify_exercise').html(data.content); } else { location.reload(); } }, "json" ); } } }); Here's some markup to show how the code relates to the structure: <div id="modify_exercise" class="dialog" title="{% trans 'Modify exercise' %}"> </div> <ul> {% for exercise in exercises %} <li> <a class="exercise" href="#" title="{{ exercise.description }}"> {{ exercise.name }} </a> </li> {% endfor %} </ul>

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  • Trouble with this Python newbie exercise. Using Lists and finding if two adjacent elements are the s

    - by Sergio Tapia
    Here's what I got: # D. Given a list of numbers, return a list where # all adjacent == elements have been reduced to a single element, # so [1, 2, 2, 3] returns [1, 2, 3]. You may create a new list or # modify the passed in list. def remove_adjacent(nums): for number in nums: numberHolder = number # +++your code here+++ return I'm kind of stuck here. What can I do?

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  • Turing's Craft exercise stumped me... seems too easy.

    - by Chris
    "Write a for loop that prints the integers 1 through 40, separated by spaces or new lines. You may use only one variable, count which has already been declared as an integer." So I use... for(count = 1; count <= 40; count++) { cout << " " << count; } but they are using stdio.h as the only header and cout is not recognized. It hints that the output format should be (" ",count), but I can't figure out what print function to use. stdio.h can use fprintf or fwrite, but I don't have enough parameters for either function. Any ideas?

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