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  • How should I compress a file with multiple bytes that are the same with Huffman coding?

    - by Omega
    On my great quest for compressing/decompressing files with a Java implementation of Huffman coding (http://en.wikipedia.org/wiki/Huffman_coding) for a school assignment, I am now at the point of building a list of prefix codes. Such codes are used when decompressing a file. Basically, the code is made of zeroes and ones, that are used to follow a path in a Huffman tree (left or right) for, ultimately, finding a byte. In this Wikipedia image, to reach the character m the prefix code would be 0111 The idea is that when you compress the file, you will basically convert all the bytes of the file into prefix codes instead (they tend to be smaller than 8 bits, so there's some gain). So every time the character m appears in a file (which in binary is actually 1101101), it will be replaced by 0111 (if we used the tree above). Therefore, 1101101110110111011011101101 becomes 0111011101110111 in the compressed file. I'm okay with that. But what if the following happens: In the file to be compressed there exists only one unique byte, say 1101101. There are 1000 of such byte. Technically, the prefix code of such byte would be... none, because there is no path to follow, right? I mean, there is only one unique byte anyway, so the tree has just one node. Therefore, if the prefix code is none, I would not be able to write the prefix code in the compressed file, because, well, there is nothing to write. Which brings this problem: how would I compress/decompress such file if it is impossible to write a prefix code when compressing? (using Huffman coding, due to the school assignment's rules) This tutorial seems to explain a bit better about prefix codes: http://www.cprogramming.com/tutorial/computersciencetheory/huffman.html but doesn't seem to address this issue either.

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  • Seek first to understand, then to be understood

    - by BuckWoody
    One of the most important (and most difficult) lessons for a technical professional to learn is to not jump to the solution. Perhaps you’ve done this, or had it happen to you. As the person you’re “listening” to is speaking, your mind is performing a B-Tree lookup on possible solutions, and when the final node of the B-Tree in your mind is reached, you blurt out the “only” solution there is to the problem, whether they are done or not. There are two issues here – both of them fatal if you don’t factor them in. First, your B-Tree may not be complete, or correct. That of course leads to an incorrect response, which blows your credibility. People will not trust you if this happens often. The second danger is that the person may modify their entire problem with a single word or phrase. I once had a client explain a detailed problem to me – and I just KNEW the answer. Then they said at the end “well, that’s what it used to do, anyway. Now it doesn’t do that anymore.” Which of course negated my entire solution – happily I had kept my mouth shut until they finished. So practice listening, rather than waiting for your turn to speak. Let the person finish, let them get the concept out, give them your full attention. They’ll appreciate the courtesy, you’ll look more intelligent, and you both may find the right answer to the problem. Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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  • collectd does not work

    - by bery
    I have installed collectd-5.0.0 on Fedora12 server and would like to run its service for receiving data from clients. I have enabled network plugin and rddtool plugin as commented: collectd.conf in server: BaseDir "/opt/collectd/var/lib/collectd" LoadPlugin "logfile" LoadPlugin network LoadPlugin rrdtool <Plugin network> Listen "192.168.8.37" "25826" </Plugin> collectd.conf in client: LoadPlugin logfile LoadPlugin cpu LoadPlugin network LoadPlugin memory <Plugin network> Server"192.168.8.37" "25826" </Plugin> collectd.log in server: [2011-08-03 02:36:04] Exiting normally. [2011-08-03 02:36:04] rrdtool plugin: Shutting down the queue thread. [2011-08-03 02:36:04] network plugin: Stopping receive thread. [2011-08-03 02:36:04] network plugin: Stopping dispatch thread. [2011-08-03 02:37:11] Initialization complete, entering read-loop. collectd.log in client: [2011-08-02 17:31:44] Initialization complete, entering read-loop. results thst execute netstat on server: netstat -ulpn | grep 25826 udp 0 0 192.168.8.37:25826 0.0.0.0:* 4744/collectd problem: but there is noting in "/opt/collectd/var/lib/collectd/" on ser yes,I move the port number of "25826" as your propose(But I think this is the default port for coolectd).there is no rdd files recived on server. collectd.log in client collectd [2011-08-03 10:01:36] plugin_read_thread: Handling memory'. [2011-08-03 10:01:36] plugin_read_thread: Handlingcpu'. [2011-08-03 10:01:36] plugin_dispatch_values: time = 1312380096.431; interval = 10.000; host = uml; plugin = memory; plugin_instance = ; type = memory; type_instance = used; [2011-08-03 10:01:36] plugin_dispatch_values: time = 1312380096.431; interval = 10.000; host = uml; plugin = cpu; plugin_instance = 0; type = cpu; type_instance = user; [2011-08-03 10:01:36] uc_update: uml/memory/memory-used: ds[0] = 280412160.000000 [2011-08-03 10:01:36] plugin: plugin_write: Writing values via network. [2011-08-03 10:01:36] uc_update: uml/cpu-0/cpu-user: ds[0] = 0.100008 [2011-08-03 10:01:36] plugin: plugin_write: Writing values via network. [2011-08-03 10:01:36] plugin_dispatch_values: time = 1312380096.431; interval = 10.000; host = uml; plugin = memory; plugin_instance = ; type = memory; type_instance = buffered; [2011-08-03 10:01:36] plugin_dispatch_values: time = 1312380096.431; interval = 10.000; host = uml; plugin = cpu; plugin_instance = 0; type = cpu; type_instance = nice; [2011-08-03 10:01:36] uc_update: uml/memory/memory-buffered: ds[0] = 344182784.000000 [2011-08-03 10:01:36] plugin: plugin_write: Writing values via network. [2011-08-03 10:01:36] uc_update: uml/cpu-0/cpu-nice: ds[0] = 0.000000 [2011-08-03 10:01:36] plugin: plugin_write: Writing values via network. [2011-08-03 10:01:36] network plugin: flush_buffer: send_buffer_fill = 1340 [2011-08-03 10:01:36] network plugin: network_send_buffer: buffer_len = 1340 ... [2011-08-03 10:01:36] plugin_read_thread: Next read of the cpu plugin at 1312380106.429064774. collectd.log in server collectd: [2011-08-03 20:18:08] type = network [2011-08-03 20:18:08] type = rrdtool [2011-08-03 20:18:08] network plugin: sockent_open: node = 192.168.8.37; service = 25826; [2011-08-03 20:18:08] fd = 3; calling bind' [2011-08-03 20:18:08] Done parsing/opt/collectd//share/collectd/types.db' [2011-08-03 20:18:08] interval_g = 10; [2011-08-03 20:18:08] timeout_g = 2; [2011-08-03 20:18:08] hostname_g = localhost.localdomain; [2011-08-03 20:18:08] Initialization complete, entering read-loop. It looks like, data is sending but doesn't be recived. Where is the mistake?

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  • TVirtualStringTree - resetting non-visual nodes and memory consumption

    - by Remy Lebeau - TeamB
    I have an app that loads records from a binary log file and displays them in a virtual TListView. There are potentially millions of records in a file, and the display can be filtered by the user, so I do not load all of the records in memory at one time, and the ListView item indexes are not a 1-to-1 relation with the file record offsets (List item 1 may be file record 100, for instance). I use the ListView's OnDataHint event to load records for just the items the ListView is actually interested in. As the user scrolls around, the range specified by OnDataHint changes, allowing me to free records that are not in the new range, and allocate new records as needed. This works fine, speed is tolerable, and the memory footprint is very low. I am currently evaluating TVirtualStringTree as a replacement for the TListView, mainly because I want to add the ability to expand/collapse records that span multiple lines (I can fudge it with the TListView by incrementing/decrementing the item count dynamically, but this is not as straight forward as using a real tree). For the most part, I have been able to port the TListView logic and have everything work as I need. I notice that TVirtualStringTree's virtual paradigm is vastly different, though. It does not have the same kind of OnDataHint functionality that TListView does (I can use the OnScroll event to fake it, which allows my memory buffer logic to continue working), and I can use the OnInitializeNode event to associate nodes with records that are allocated. However, once a tree node is initialized, it sees that it remains initialized for the lifetime of the tree. That is not good for me. As the user scrolls around and I remove records from memory, I need to reset those non-visual nodes without removing them from the tree completely, or losing their expand/collapse states. When the user scrolls them back into view, I can re-allocate the records and re-initialize the nodes. Basically, I want to make TVirtualStringTree act as much like TListView as possible, as far as its virtualization is concerned. I have seen that TVirtualStringTree has a ResetNode() method, but I encounter various errors whenever I try to use it. I must be using it wrong. I also thought of just storing a data pointer inside each node to my record buffers, and I allocate and free memory, update those pointers accordingly. The end effect does not work so well, either. Worse, my largest test log file has ~5 million records in it. If I initialize the TVirtualStringTree with that many nodes at one time (when the log display is unfiltered), the tree's internal overhead for its nodes takes up a whopping 260MB of memory (without any records being allocated yet). Whereas with the TListView, loading the same log file and all the memory logic behind it, I can get away with using just a few MBs. Any ideas?

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  • TVirtualStringTree - resetting non-visual nodes and memory comsumption

    - by Remy Lebeau - TeamB
    I have an app that loads records from a binary log file and displays them in a virtual TListView. There are potentially millions of records in a file, and the display can be filtered by the user, so I do not load all of the records in memory at one time, and the ListView item indexes are not a 1-to-1 relation with the file record offsets (List item 1 may be file record 100, for instance). I use the ListView's OnDataHint event to load records for just the items the ListView is actually interested in. As the user scrolls around, the range specified by OnDataHint changes, allowing me to free records that are not in the new range, and allocate new records as needed. This works fine, speed is tolerable, and the memory footprint is very low. I am currently evaluating TVirtualStringTree as a replacement for the TListView, mainly because I want to add the ability to expand/collapse records that span multiple lines (I can fudge it with the TListView by incrementing/decrementing the item count dynamically, but this is not as straight forward as using a real tree). For the most part, I have been able to port the TListView logic and have everything work as I need. I notice that TVirtualStringTree's virtual paridigm is vastly different, though. It does not have the same kind of OnDataHint functionality that TListView does (I can use the OnScroll event to fake it, which allows my memory buffer logic to continue working), and I can use the OnInitializeNode event to associate nodes with records that are allocated. However, once a tree node is initialized, it sees that it remains initialized for the lifetime of the tree. That is not good for me. As the user scrolls around and I remove records from memory, I need to reset those non-visual nodes without removing them from the tree completely, or losing their expand/collapse states. When the user scrolls them back into view, I can re-allocate the records and re-initialize the nodes. Basically, I want to make TVirtualStringTree act as much like TListView as possible, as far as its virtualization is concerned. I have seen that TVirtualStringTree has a ResetNode() method, but I encounter various errors whenever I try to use it. I must be using it wrong. I also thought of just storing a data pointer inside each node to my record buffers, and I allocate and free memory, update those pointers accordingly. The end effect does not work so well, either. Worse, my largest test log file has ~5 million records in it. If I initialize the TVirtualStringTree with that many nodes at one time (when the log display is unfiltered), the tree's internal overhead for its nodes takes up a whopping 260MB of memory (without any records being allocated yet). Whereas with the TListView, loading the same log file and all the memory logic behind it, I can get away with using just a few MBs. Any ideas?

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  • What's the best way to do base36 arithmetic in perl?

    - by DVK
    What's the best way to do base36 arithmetic in Perl? To be more specific, I need to be able to do the following: Operate on positive N-digit numbers in base 36 (e.g. digits are 0-9 A-Z) N is finite, say 9 Provide basic arithmetic, at the very least the following 3: Addition (A+B) Subtraction (A-B) Whole division, e.g. floor(A/B). Strictly speaking, I don't really need a base10 conversion ability - the numbers will 100% of time be in base36. So I'm quite OK if the solution does NOT implement conversion from base36 back to base10 and vice versa. I don't much care whether the solution is brute-force "convert to base 10 and back" or converting to binary, or some more elegant approach "natively" performing baseN operations (as stated above, to/from base10 conversion is not a requirement). My only 3 considerations are: It fits the minimum specifications above It's "standard". Currently we're using and old homegrown module based on base10 conversion done by hand that is buggy and sucks. I'd much rather replace that with some commonly used CPAN solution instead of re-writing my own bicycle from scratch, but I'm perfectly capable of building it if no better standard possibility exists. It must be fast-ish (though not lightning fast). Something that takes 1 second to sum up 2 9-digit base36 numbers is worse than anything I can roll on my own :) P.S. Just to provide some context in case people decide to solve my XY problem for me in addition to answering the technical question above :) We have a fairly large tree (stored in DB as a bunch of edges), and we need to superimpose order on a subset of that tree. The tree dimentions are big both depth- and breadth- wise. The tree is VERY actively updated (inserts and deletes and branch moves). This is currently done by having a second table with 3 columns: parent_vertex, child_vertex, local_order, where local_order is an 9-character string built of A-Z0-9 (e.g. base 36 number). Additional considerations: It is required that the local order is unique per child (and obviously unique per parent), Any complete re-ordering of a parent is somewhat expensive, and thus the implementation is to try and assign - for a parent with X children - the orders which are somewhat evenly distributed between 0 and 36**10-1, so that almost no tree inserts result in a full re-ordering.

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  • How to generate and encode (for use in GA), random, strict, binary rooted trees with N leaves?

    - by Peter Simon
    First, I am an engineer, not a computer scientist, so I apologize in advance for any misuse of nomenclature and general ignorance of CS background. Here is the motivational background for my question: I am contemplating writing a genetic algorithm optimizer to aid in designing a power divider network (also called a beam forming network, or BFN for short). The BFN is intended to distribute power to each of N radiating elements in an array of antennas. The fraction of the total input power to be delivered to each radiating element has been specified. Topologically speaking, a BFN is a strictly binary, rooted tree. Each of the (N-1) interior nodes of the tree represents the input port of an unequal, binary power splitter. The N leaves of the tree are the power divider outputs. Given a particular power divider topology, one is still free to map the power divider outputs to the array inputs in an arbitrary order. There are N! such permutations of the outputs. There are several considerations in choosing the desired ordering: 1) The power ratio for each binary coupler should be within a specified range of values. 2) The ordering should be chosen to simplify the mechanical routing of the transmission lines connecting the power divider. The number of ouputs N of the BFN may range from, say, 6 to 22. I have already written a genetic algorithm optimizer that, given a particular BFN topology and desired array input power distribution, will search through the N! permutations of the BFN outputs to generate a design with compliant power ratios and good mechanical routing. I would now like to generalize my program to automatically generate and search through the space of possible BFN topologies. As I understand it, for N outputs (leaves of the binary tree), there are $C_{N-1}$ different topologies that can be constructed, where $C_N$ is the Catalan number. I would like to know how to encode an arbitrary tree having N leaves in a way that is consistent with a chromosomal description for use in a genetic algorithm. Also associated with this is the need to generate random instances for filling the initial population, and to implement crossover and mutations operators for this type of chromosome. Any suggestions will be welcome. Please minimize the amount of CS lingo in your reply, since I am not likely to be acquainted with it. Thanks in advance, Peter

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  • Idiomatic use of auto_ptr to transfer ownership to a container

    - by heycam
    I'm refreshing my C++ knowledge after not having used it in anger for a number of years. In writing some code to implement some data structure for practice, I wanted to make sure that my code was exception safe. So I've tried to use std::auto_ptrs in what I think is an appropriate way. Simplifying somewhat, this is what I have: class Tree { public: ~Tree() { /* delete all Node*s in the tree */ } void insert(const string& to_insert); ... private: struct Node { ... vector<Node*> m_children; }; Node* m_root; }; template<T> void push_back(vector<T*>& v, auto_ptr<T> x) { v.push_back(x.get()); x.release(); } void Tree::insert(const string& to_insert) { Node* n = ...; // find where to insert the new node ... push_back(n->m_children, auto_ptr<Node>(new Node(to_insert)); ... } So I'm wrapping the function that would put the pointer into the container, vector::push_back, and relying on the by-value auto_ptr argument to ensure that the Node* is deleted if the vector resize fails. Is this an idiomatic use of auto_ptr to save a bit of boilerplate in my Tree::insert? Any improvements you can suggest? Otherwise I'd have to have something like: Node* n = ...; // find where to insert the new node auto_ptr<Node> new_node(new Node(to_insert)); n->m_children.push_back(new_node.get()); new_node.release(); which kind of clutters up what would have been a single line of code if I wasn't worrying about exception safety and a memory leak. (Actually I was wondering if I could post my whole code sample (about 300 lines) and ask people to critique it for idiomatic C++ usage in general, but I'm not sure whether that kind of question is appropriate on stackoverflow.)

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  • ANTS CLR and Memory Profiler In Depth Review (Part 1 of 2 &ndash; CLR Profiler)

    - by ToStringTheory
    One of the things that people might not know about me, is my obsession to make my code as efficient as possible.  Many people might not realize how much of a task or undertaking that this might be, but it is surely a task as monumental as climbing Mount Everest, except this time it is a challenge for the mind…  In trying to make code efficient, there are many different factors that play a part – size of project or solution, tiers, language used, experience and training of the programmer, technologies used, maintainability of the code – the list can go on for quite some time. I spend quite a bit of time when developing trying to determine what is the best way to implement a feature to accomplish the efficiency that I look to achieve.  One program that I have recently come to learn about – Red Gate ANTS Performance (CLR) and Memory profiler gives me tools to accomplish that job more efficiently as well.  In this review, I am going to cover some of the features of the ANTS profiler set by compiling some hideous example code to test against. Notice As a member of the Geeks With Blogs Influencers program, one of the perks is the ability to review products, in exchange for a free license to the program.  I have not let this affect my opinions of the product in any way, and Red Gate nor Geeks With Blogs has tried to influence my opinion regarding this product in any way. Introduction The ANTS Profiler pack provided by Red Gate was something that I had not heard of before receiving an email regarding an offer to review it for a license.  Since I look to make my code efficient, it was a no brainer for me to try it out!  One thing that I have to say took me by surprise is that upon downloading the program and installing it you fill out a form for your usual contact information.  Sure enough within 2 hours, I received an email from a sales representative at Red Gate asking if she could help me to achieve the most out of my trial time so it wouldn’t go to waste.  After replying to her and explaining that I was looking to review its feature set, she put me in contact with someone that setup a demo session to give me a quick rundown of its features via an online meeting.  After having dealt with a massive ordeal with one of my utility companies and their complete lack of customer service, Red Gates friendly and helpful representatives were a breath of fresh air, and something I was thankful for. ANTS CLR Profiler The ANTS CLR profiler is the thing I want to focus on the most in this post, so I am going to dive right in now. Install was simple and took no time at all.  It installed both the profiler for the CLR and Memory, but also visual studio extensions to facilitate the usage of the profilers (click any images for full size images): The Visual Studio menu options (under ANTS menu) Starting the CLR Performance Profiler from the start menu yields this window If you follow the instructions after launching the program from the start menu (Click File > New Profiling Session to start a new project), you are given a dialog with plenty of options for profiling: The New Session dialog.  Lots of options.  One thing I noticed is that the buttons in the lower right were half-covered by the panel of the application.  If I had to guess, I would imagine that this is caused by my DPI settings being set to 125%.  This is a problem I have seen in other applications as well that don’t scale well to different dpi scales. The profiler options give you the ability to profile: .NET Executable ASP.NET web application (hosted in IIS) ASP.NET web application (hosted in IIS express) ASP.NET web application (hosted in Cassini Web Development Server) SharePoint web application (hosted in IIS) Silverlight 4+ application Windows Service COM+ server XBAP (local XAML browser application) Attach to an already running .NET 4 process Choosing each option provides a varying set of other variables/options that one can set including options such as application arguments, operating path, record I/O performance performance counters to record (43 counters in all!), etc…  All in all, they give you the ability to profile many different .Net project types, and make it simple to do so.  In most cases of my using this application, I would be using the built in Visual Studio extensions, as they automatically start a new profiling project in ANTS with the options setup, and start your program, however RedGate has made it easy enough to profile outside of Visual Studio as well. On the flip side of this, as someone who lives most of their work life in Visual Studio, one thing I do wish is that instead of opening an entirely separate application/gui to perform profiling after launching, that instead they would provide a Visual Studio panel with the information, and integrate more of the profiling project information into Visual Studio.  So, now that we have an idea of what options that the profiler gives us, its time to test its abilities and features. Horrendous Example Code – Prime Number Generator One of my interests besides development, is Physics and Math – what I went to college for.  I have especially always been interested in prime numbers, as they are something of a mystery…  So, I decided that I would go ahead and to test the abilities of the profiler, I would write a small program, website, and library to generate prime numbers in the quantity that you ask for.  I am going to start off with some terrible code, and show how I would see the profiler being used as a development tool. First off, the IPrimes interface (all code is downloadable at the end of the post): interface IPrimes { IEnumerable<int> GetPrimes(int retrieve); } Simple enough, right?  Anything that implements the interface will (hopefully) provide an IEnumerable of int, with the quantity specified in the parameter argument.  Next, I am going to implement this interface in the most basic way: public class DumbPrimes : IPrimes { public IEnumerable<int> GetPrimes(int retrieve) { //store a list of primes already found var _foundPrimes = new List<int>() { 2, 3 }; //if i ask for 1 or two primes, return what asked for if (retrieve <= _foundPrimes.Count()) return _foundPrimes.Take(retrieve); //the next number to look at int _analyzing = 4; //since I already determined I don't have enough //execute at least once, and until quantity is sufficed do { //assume prime until otherwise determined bool isPrime = true; //start dividing at 2 //divide until number is reached, or determined not prime for (int i = 2; i < _analyzing && isPrime; i++) { //if (i) goes into _analyzing without a remainder, //_analyzing is NOT prime if (_analyzing % i == 0) isPrime = false; } //if it is prime, add to found list if (isPrime) _foundPrimes.Add(_analyzing); //increment number to analyze next _analyzing++; } while (_foundPrimes.Count() < retrieve); return _foundPrimes; } } This is the simplest way to get primes in my opinion.  Checking each number by the straight definition of a prime – is it divisible by anything besides 1 and itself. I have included this code in a base class library for my solution, as I am going to use it to demonstrate a couple of features of ANTS.  This class library is consumed by a simple non-MVVM WPF application, and a simple MVC4 website.  I will not post the WPF code here inline, as it is simply an ObservableCollection<int>, a label, two textbox’s, and a button. Starting a new Profiling Session So, in Visual Studio, I have just completed my first stint developing the GUI and DumbPrimes IPrimes class, so now I want to check my codes efficiency by profiling it.  All I have to do is build the solution (surprised initiating a profiling session doesn’t do this, but I suppose I can understand it), and then click the ANTS menu, followed by Profile Performance.  I am then greeted by the profiler starting up and already monitoring my program live: You are provided with a realtime graph at the top, and a pane at the bottom giving you information on how to proceed.  I am going to start by asking my program to show me the first 15000 primes: After the program finally began responding again (I did all the work on the main UI thread – how bad!), I stopped the profiler, which did kill the process of my program too.  One important thing to note, is that the profiler by default wants to give you a lot of detail about the operation – line hit counts, time per line, percent time per line, etc…  The important thing to remember is that this itself takes a lot of time.  When running my program without the profiler attached, it can generate the 15000 primes in 5.18 seconds, compared to 74.5 seconds – almost a 1500 percent increase.  While this may seem like a lot, remember that there is a trade off.  It may be WAY more inefficient, however, I am able to drill down and make improvements to specific problem areas, and then decrease execution time all around. Analyzing the Profiling Session After clicking ‘Stop Profiling’, the process running my application stopped, and the entire execution time was automatically selected by ANTS, and the results shown below: Now there are a number of interesting things going on here, I am going to cover each in a section of its own: Real Time Performance Counter Bar (top of screen) At the top of the screen, is the real time performance bar.  As your application is running, this will constantly update with the currently selected performance counters status.  A couple of cool things to note are the fact that you can drag a selection around specific time periods to drill down the detail views in the lower 2 panels to information pertaining to only that period. After selecting a time period, you can bookmark a section and name it, so that it is easy to find later, or after reloaded at a later time.  You can also zoom in, out, or fit the graph to the space provided – useful for drilling down. It may be hard to see, but at the top of the processor time graph below the time ticks, but above the red usage graph, there is a green bar. This bar shows at what times a method that is selected in the ‘Call tree’ panel is called. Very cool to be able to click on a method and see at what times it made an impact. As I said before, ANTS provides 43 different performance counters you can hook into.  Click the arrow next to the Performance tab at the top will allow you to change between different counters if you have them selected: Method Call Tree, ADO.Net Database Calls, File IO – Detail Panel Red Gate really hit the mark here I think. When you select a section of the run with the graph, the call tree populates to fill a hierarchical tree of method calls, with information regarding each of the methods.   By default, methods are hidden where the source is not provided (framework type code), however, Red Gate has integrated Reflector into ANTS, so even if you don’t have source for something, you can select a method and get the source if you want.  Methods are also hidden where the impact is seen as insignificant – methods that are only executed for 1% of the time of the overall calling methods time; in other words, working on making them better is not where your efforts should be focused. – Smart! Source Panel – Detail Panel The source panel is where you can see line level information on your code, showing the code for the currently selected method from the Method Call Tree.  If the code is not available, Reflector takes care of it and shows the code anyways! As you can notice, there does seem to be a problem with how ANTS determines what line is the actual line that a call is completed on.  I have suspicions that this may be due to some of the inline code optimizations that the CLR applies upon compilation of the assembly.  In a method with comments, the problem is much more severe: As you can see here, apparently the most offending code in my base library was a comment – *gasp*!  Removing the comments does help quite a bit, however I hope that Red Gate works on their counter algorithm soon to improve the logic on positioning for statistics: I did a small test just to demonstrate the lines are correct without comments. For me, it isn’t a deal breaker, as I can usually determine the correct placements by looking at the application code in the region and determining what makes sense, but it is something that would probably build up some irritation with time. Feature – Suggest Method for Optimization A neat feature to really help those in need of a pointer, is the menu option under tools to automatically suggest methods to optimize/improve: Nice feature – clicking it filters the call tree and stars methods that it thinks are good candidates for optimization.  I do wish that they would have made it more visible for those of use who aren’t great on sight: Process Integration I do think that this could have a place in my process.  After experimenting with the profiler, I do think it would be a great benefit to do some development, testing, and then after all the bugs are worked out, use the profiler to check on things to make sure nothing seems like it is hogging more than its fair share.  For example, with this program, I would have developed it, ran it, tested it – it works, but slowly. After looking at the profiler, and seeing the massive amount of time spent in 1 method, I might go ahead and try to re-implement IPrimes (I actually would probably rewrite the offending code, but so that I can distribute both sets of code easily, I’m just going to make another implementation of IPrimes).  Using two pieces of knowledge about prime numbers can make this method MUCH more efficient – prime numbers fall into two buckets 6k+/-1 , and a number is prime if it is not divisible by any other primes before it: public class SmartPrimes : IPrimes { public IEnumerable<int> GetPrimes(int retrieve) { //store a list of primes already found var _foundPrimes = new List<int>() { 2, 3 }; //if i ask for 1 or two primes, return what asked for if (retrieve <= _foundPrimes.Count()) return _foundPrimes.Take(retrieve); //the next number to look at int _k = 1; //since I already determined I don't have enough //execute at least once, and until quantity is sufficed do { //assume prime until otherwise determined bool isPrime = true; int potentialPrime; //analyze 6k-1 //assign the value to potential potentialPrime = 6 * _k - 1; //if there are any primes that divise this, it is NOT a prime number //using PLINQ for quick boost isPrime = !_foundPrimes.AsParallel() .Any(prime => potentialPrime % prime == 0); //if it is prime, add to found list if (isPrime) _foundPrimes.Add(potentialPrime); if (_foundPrimes.Count() == retrieve) break; //analyze 6k+1 //assign the value to potential potentialPrime = 6 * _k + 1; //if there are any primes that divise this, it is NOT a prime number //using PLINQ for quick boost isPrime = !_foundPrimes.AsParallel() .Any(prime => potentialPrime % prime == 0); //if it is prime, add to found list if (isPrime) _foundPrimes.Add(potentialPrime); //increment k to analyze next _k++; } while (_foundPrimes.Count() < retrieve); return _foundPrimes; } } Now there are definitely more things I can do to help make this more efficient, but for the scope of this example, I think this is fine (but still hideous)! Profiling this now yields a happy surprise 27 seconds to generate the 15000 primes with the profiler attached, and only 1.43 seconds without.  One important thing I wanted to call out though was the performance graph now: Notice anything odd?  The %Processor time is above 100%.  This is because there is now more than 1 core in the operation.  A better label for the chart in my mind would have been %Core time, but to each their own. Another odd thing I noticed was that the profiler seemed to be spot on this time in my DumbPrimes class with line details in source, even with comments..  Odd. Profiling Web Applications The last thing that I wanted to cover, that means a lot to me as a web developer, is the great amount of work that Red Gate put into the profiler when profiling web applications.  In my solution, I have a simple MVC4 application setup with 1 page, a single input form, that will output prime values as my WPF app did.  Launching the profiler from Visual Studio as before, nothing is really different in the profiler window, however I did receive a UAC prompt for a Red Gate helper app to integrate with the web server without notification. After requesting 500, 1000, 2000, and 5000 primes, and looking at the profiler session, things are slightly different from before: As you can see, there are 4 spikes of activity in the processor time graph, but there is also something new in the call tree: That’s right – ANTS will actually group method calls by get/post operations, so it is easier to find out what action/page is giving the largest problems…  Pretty cool in my mind! Overview Overall, I think that Red Gate ANTS CLR Profiler has a lot to offer, however I think it also has a long ways to go.  3 Biggest Pros: Ability to easily drill down from time graph, to method calls, to source code Wide variety of counters to choose from when profiling your application Excellent integration/grouping of methods being called from web applications by request – BRILLIANT! 3 Biggest Cons: Issue regarding line details in source view Nit pick – Processor time vs. Core time Nit pick – Lack of full integration with Visual Studio Ratings Ease of Use (7/10) – I marked down here because of the problems with the line level details and the extra work that that entails, and the lack of better integration with Visual Studio. Effectiveness (10/10) – I believe that the profiler does EXACTLY what it purports to do.  Especially with its large variety of performance counters, a definite plus! Features (9/10) – Besides the real time performance monitoring, and the drill downs that I’ve shown here, ANTS also has great integration with ADO.Net, with the ability to show database queries run by your application in the profiler.  This, with the line level details, the web request grouping, reflector integration, and various options to customize your profiling session I think create a great set of features! Customer Service (10/10) – My entire experience with Red Gate personnel has been nothing but good.  their people are friendly, helpful, and happy! UI / UX (8/10) – The interface is very easy to get around, and all of the options are easy to find.  With a little bit of poking around, you’ll be optimizing Hello World in no time flat! Overall (8/10) – Overall, I am happy with the Performance Profiler and its features, as well as with the service I received when working with the Red Gate personnel.  I WOULD recommend you trying the application and seeing if it would fit into your process, BUT, remember there are still some kinks in it to hopefully be worked out. My next post will definitely be shorter (hopefully), but thank you for reading up to here, or skipping ahead!  Please, if you do try the product, drop me a message and let me know what you think!  I would love to hear any opinions you may have on the product. Code Feel free to download the code I used above – download via DropBox

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  • Silverlight Cream for February 10, 2011 -- #1045

    - by Dave Campbell
    In this Issue: Mark Monster, Jaime Rodriguez, Mark Hopkins, WindowsPhoneGeek, David Anson, Jesse Liberty, Jeremy Likness, Martin Krüger(-2-), Beth Massi, Joost van Schaik, Laurent Bugnion, and Arik Poznanski. Above the Fold: Silverlight: "Parsing the Visual Tree with LINQ" Jeremy Likness WP7: "Silverlight-ready PNG encoder implementation shows one way to use .NET IEnumerables effectively" David Anson Lightswitch: "How to Send Automated Appointments from a LightSwitch Application" Beth Massi Shoutouts: Be sure to visit SilverlightShow... check out their top hits last week: SilverlightShow for Jan 31- Feb 06, 2011 Jaime Rodriguez has a post up that all the WP7 folks will be interested in: FAQ about copy paste functionality in upcoming release From SilverlightCream.com: Make use of WCF FaultContracts in Silverlight clients Mark Monster takes a shot at answering “The remote server returned an error: NotFound” while connecting to a WCF Service problem we all see. Communication between HTML in WebBrowser and Silverlight app Jaime Rodriguez responds to questions he received about communication between HTML and SIlverlight with this post about the bi-directional communication between the control and HTML. WP7 - Real Apps, Real Code Mark Hopkins has a post up about some WP7 starter kits that you can get all the source for and actually download the app from the Marketplace first to see if it interests you! WP7 AboutPrompt in depth WindowsPhoneGeek has this cool post up about the AboutPrompt from the Coding4Fun toolkit in detail... great diagrams showing where all the elements are and code examples with images. Silverlight-ready PNG encoder implementation shows one way to use .NET IEnumerables effectively David Anson describes why he took it upon himself to write his own png encoder for Silverlight... and we all thank him for doing so and providing us with the code! Navigation 101–Cancelling Navigation Jesse Liberty's latest WP7 From Scratch episode is up (number 32), and he's talking about Navigation and how to cancel it if you need to. Parsing the Visual Tree with LINQ Jeremy Likness demonstrates using LINQ to rat out information in the visual tree of your XAML. To Quote Jeremy: "you can easily check for intersections between elements and find any type of element no matter how deep within the tree it is". SpriteAnimationBehavior Martin Krüger has a couple more fun things in the Expression Gallery that I haven't discussed. First up is a behavior that animates up to 999 images and lets you control the FramesPerSecond... great demo on the ExpressionGallery to play with. Second alternative: Storyboard should not start before the Silverlight application is loaded Martin Krüger's latest is a way to programmatically wait for the Loaded event so that you know you can let your animations fly. How to Send Automated Appointments from a LightSwitch Application Beth Massi's latest Lightswitch post follows up her Outlook automation one with sending appointments using the standard iCalendar format... all the code included of course. The case for the Bindable Application Bar for Windows Phone 7 Joost van Schaik posts about a bindable Application Bar for your WP7 apps... grab the code and don't leave home without it :) MVVM Light V4 preview (BL0014) release notes Laurent Bugnion posted an update to MVVMLight to Codeplex a couple days ago. This is an early preview of what he plans on having in version 4, so check out the post for what's new and fun. Search Digg on Windows Phone 7 Arik Poznanski followed up his RSS post from last week with this one on searching Digg on WP7... and he's discussing and providing a utility class for doing it. Stay in the 'Light! Twitter SilverlightNews | Twitter WynApse | WynApse.com | Tagged Posts | SilverlightCream Join me @ SilverlightCream | Phoenix Silverlight User Group Technorati Tags: Silverlight    Silverlight 3    Silverlight 4    Windows Phone MIX10

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  • Of C# Iterators and Performance

    - by James Michael Hare
    Some of you reading this will be wondering, "what is an iterator" and think I'm locked in the world of C++.  Nope, I'm talking C# iterators.  No, not enumerators, iterators.   So, for those of you who do not know what iterators are in C#, I will explain it in summary, and for those of you who know what iterators are but are curious of the performance impacts, I will explore that as well.   Iterators have been around for a bit now, and there are still a bunch of people who don't know what they are or what they do.  I don't know how many times at work I've had a code review on my code and have someone ask me, "what's that yield word do?"   Basically, this post came to me as I was writing some extension methods to extend IEnumerable<T> -- I'll post some of the fun ones in a later post.  Since I was filtering the resulting list down, I was using the standard C# iterator concept; but that got me wondering: what are the performance implications of using an iterator versus returning a new enumeration?   So, to begin, let's look at a couple of methods.  This is a new (albeit contrived) method called Every(...).  The goal of this method is to access and enumeration and return every nth item in the enumeration (including the first).  So Every(2) would return items 0, 2, 4, 6, etc.   Now, if you wanted to write this in the traditional way, you may come up with something like this:       public static IEnumerable<T> Every<T>(this IEnumerable<T> list, int interval)     {         List<T> newList = new List<T>();         int count = 0;           foreach (var i in list)         {             if ((count++ % interval) == 0)             {                 newList.Add(i);             }         }           return newList;     }     So basically this method takes any IEnumerable<T> and returns a new IEnumerable<T> that contains every nth item.  Pretty straight forward.   The problem?  Well, Every<T>(...) will construct a list containing every nth item whether or not you care.  What happens if you were searching this result for a certain item and find that item after five tries?  You would have generated the rest of the list for nothing.   Enter iterators.  This C# construct uses the yield keyword to effectively defer evaluation of the next item until it is asked for.  This can be very handy if the evaluation itself is expensive or if there's a fair chance you'll never want to fully evaluate a list.   We see this all the time in Linq, where many expressions are chained together to do complex processing on a list.  This would be very expensive if each of these expressions evaluated their entire possible result set on call.    Let's look at the same example function, this time using an iterator:       public static IEnumerable<T> Every<T>(this IEnumerable<T> list, int interval)     {         int count = 0;         foreach (var i in list)         {             if ((count++ % interval) == 0)             {                 yield return i;             }         }     }   Notice it does not create a new return value explicitly, the only evidence of a return is the "yield return" statement.  What this means is that when an item is requested from the enumeration, it will enter this method and evaluate until it either hits a yield return (in which case that item is returned) or until it exits the method or hits a yield break (in which case the iteration ends.   Behind the scenes, this is all done with a class that the CLR creates behind the scenes that keeps track of the state of the iteration, so that every time the next item is asked for, it finds that item and then updates the current position so it knows where to start at next time.   It doesn't seem like a big deal, does it?  But keep in mind the key point here: it only returns items as they are requested. Thus if there's a good chance you will only process a portion of the return list and/or if the evaluation of each item is expensive, an iterator may be of benefit.   This is especially true if you intend your methods to be chainable similar to the way Linq methods can be chained.    For example, perhaps you have a List<int> and you want to take every tenth one until you find one greater than 10.  We could write that as:       List<int> someList = new List<int>();         // fill list here         someList.Every(10).TakeWhile(i => i <= 10);     Now is the difference more apparent?  If we use the first form of Every that makes a copy of the list.  It's going to copy the entire list whether we will need those items or not, that can be costly!    With the iterator version, however, it will only take items from the list until it finds one that is > 10, at which point no further items in the list are evaluated.   So, sounds neat eh?  But what's the cost is what you're probably wondering.  So I ran some tests using the two forms of Every above on lists varying from 5 to 500,000 integers and tried various things.    Now, iteration isn't free.  If you are more likely than not to iterate the entire collection every time, iterator has some very slight overhead:   Copy vs Iterator on 100% of Collection (10,000 iterations) Collection Size Num Iterated Type Total ms 5 5 Copy 5 5 5 Iterator 5 50 50 Copy 28 50 50 Iterator 27 500 500 Copy 227 500 500 Iterator 247 5000 5000 Copy 2266 5000 5000 Iterator 2444 50,000 50,000 Copy 24,443 50,000 50,000 Iterator 24,719 500,000 500,000 Copy 250,024 500,000 500,000 Iterator 251,521   Notice that when iterating over the entire produced list, the times for the iterator are a little better for smaller lists, then getting just a slight bit worse for larger lists.  In reality, given the number of items and iterations, the result is near negligible, but just to show that iterators come at a price.  However, it should also be noted that the form of Every that returns a copy will have a left-over collection to garbage collect.   However, if we only partially evaluate less and less through the list, the savings start to show and make it well worth the overhead.  Let's look at what happens if you stop looking after 80% of the list:   Copy vs Iterator on 80% of Collection (10,000 iterations) Collection Size Num Iterated Type Total ms 5 4 Copy 5 5 4 Iterator 5 50 40 Copy 27 50 40 Iterator 23 500 400 Copy 215 500 400 Iterator 200 5000 4000 Copy 2099 5000 4000 Iterator 1962 50,000 40,000 Copy 22,385 50,000 40,000 Iterator 19,599 500,000 400,000 Copy 236,427 500,000 400,000 Iterator 196,010       Notice that the iterator form is now operating quite a bit faster.  But the savings really add up if you stop on average at 50% (which most searches would typically do):     Copy vs Iterator on 50% of Collection (10,000 iterations) Collection Size Num Iterated Type Total ms 5 2 Copy 5 5 2 Iterator 4 50 25 Copy 25 50 25 Iterator 16 500 250 Copy 188 500 250 Iterator 126 5000 2500 Copy 1854 5000 2500 Iterator 1226 50,000 25,000 Copy 19,839 50,000 25,000 Iterator 12,233 500,000 250,000 Copy 208,667 500,000 250,000 Iterator 122,336   Now we see that if we only expect to go on average 50% into the results, we tend to shave off around 40% of the time.  And this is only for one level deep.  If we are using this in a chain of query expressions it only adds to the savings.   So my recommendation?  If you have a resonable expectation that someone may only want to partially consume your enumerable result, I would always tend to favor an iterator.  The cost if they iterate the whole thing does not add much at all -- and if they consume only partially, you reap some really good performance gains.   Next time I'll discuss some of my favorite extensions I've created to make development life a little easier and maintainability a little better.

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  • How to recover data files from xampp-windows to xampp-linux after crash?

    - by David Buehler
    My Windows box died after I developed a database in xampp on it; fortunately I have a backup of the entire F:/TestWeb/Xampp partition. Unfortunately, I did not do an Export (nor dump) of the "Lws2" database before the crash. I have replaced the defunct machine with one running Mint7 (based on Ubuntu 9.04 "Jaunty Jackalope") and installed xampp-linux into the /opt partition, so the new xampp now runs fine in /opt/lampp, and says all the elements are secured by passwords (which I just assigned during this installation.) I assumed that Xamp-Windows installed in November would migrate easily to xampp-linux installed iin February -- a bad assumption. It apparently would have been simple if I had known enough to do an Export or a Dump before the crash, but.... The backup was done to a Network Attached Storage drive, which is formatted as "vfat" so the backup does not carry with it any valid ownership permissions from MySql on NTFS. I now see from my backup that the old data resided in \TestWeb\Xampp\Mysql\Data\Lws2\ and consists of 7 ".frm" files which define my tables. The actual data -- I suppose a ".sql" file or files -- has disappeared, and I am resigning myself to two days of retyping it. But I do not wish to do the table layouts all over again. So I copied Data tree to /opt/lampp/Data -- PhpMyAdmin does not see it. So I copied Lws2 tree to /opt/lampp/Lws2 -- PhpMyAdmin does not see it. So I copied Data tree to /opt/lampp/var/mysql/Data -- PhpMyAdmin does not see it. So I copied Lws2 tree to /opt/lampp/var/mysql/Lws2 -- PhpMyAdmin does not see it. So I adjusted all the permissions to stop saying owner "nobody" to owner "root" and gave full permissions to all groups and to all others, with permissions percolating down, in all 4 trees. You guessed it -- PhpMyAdmin does not see any database named Lws2, only its 4 default ones. I double-checked the permissions and rebooted Linux and repeated the tests. At some point in that process I did see PhpMyAdmin showing "lws2(7)" but when I clicked on it I saw a "no table found" message. I have not been able to recreate that experience. Apparently there are some setup files for MySql and for PhpMyAdmin which need to be set up by running a wizard or two or by editing the files directly. I grepped the TestWeb tree and found an old "ldir = "C:TestWeb\Xampp\MySql\" and a "DataDir = C:TestWeb\Xampp\MySql\" in a .php file and in a .bat file, but I cannot find the corresponding config file names on the /opt partition/ -- so it looks as if these wizards have not been run to create them. What config files files does Linux use to setup MySql config files for PhpMyAdmin? What wizards do I need to run to point the MySql engine and the PhpMyAdmin at the folder /opt/lampp/data/ with its lws2 folder inside it? Or which files do I need to edit, with a sample of what it normally says under Linux? Incidentally, I remember I converted from MyISAM with its .MYD and .MYI files to InnoDB after entering only a small amount of the data -- and I do not know what file types to look for -- perhaps my data is still there but under another guise or in another place? Is it something as simple as linux needing to see "/data/" instead of /Data? I will check that out while waiting for a response. If anyone can point me to documentation that discusses this level of detail -- I will read it avidly! In any case, thanks for any clarification you can give on this thorny problem. wizdum

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  • Is this fix to "PostSharp complains about CA1800:DoNotCastUnnecessarily" the best one?

    - by cad
    This question is about "is" and "as" in casting and about CA1800 PostSharp rule. I want to know if the solution I thought is the best one possible or if it have any problem that I can't see. I have this code (named OriginaL Code and reduced to the minimum relevant). The function ValidateSubscriptionLicenceProducts try to validate a SubscriptionLicence (that could be of 3 types: Standard,Credit and TimeLimited ) by casting it and checking later some stuff (in //Do Whatever). PostSharp complains about CA1800:DoNotCastUnnecessarily. The reason is that I am casting two times the same object to the same type. This code in best case will cast 2 times (if it is a StandardLicence) and in worst case 4 times (If it is a TimeLimited Licence). I know is possible to invalidate rule (it was my first approach), as there is no big impact in performance here, but I am trying a best approach. //Version Original Code //Min 2 casts, max 4 casts //PostSharp Complains about CA1800:DoNotCastUnnecessarily private void ValidateSubscriptionLicenceProducts(SubscriptionLicence licence) { if (licence is StandardSubscriptionLicence) { // All products must have the same products purchased List<StandardSubscriptionLicenceProduct> standardProducts = ((StandardSubscriptionLicence)licence).SubscribedProducts; //Do whatever } else if (licence is CreditSubscriptionLicence) { // All products must have a valid Credit entitlement & Credit interval List<CreditSubscriptionLicenceProduct> creditProducts = ((CreditSubscriptionLicence)licence).SubscribedProducts; //Do whatever } else if (licence is TimeLimitedSubscriptionLicence) { // All products must have a valid Time entitlement // All products must have a valid Credit entitlement & Credit interval List<TimeLimitedSubscriptionLicenceProduct> creditProducts = ((TimeLimitedSubscriptionLicence)licence).SubscribedProducts; //Do whatever } else throw new InvalidSubscriptionLicenceException("Invalid Licence type"); //More code... } This is Improved1 version using "as". Do not complain about CA1800 but the problem is that it will cast always 3 times (if in the future we have 30 or 40 types of licences it could perform bad) //Version Improve 1 //Minimum 3 casts, maximum 3 casts private void ValidateSubscriptionLicenceProducts(SubscriptionLicence licence) { StandardSubscriptionLicence standardLicence = Slicence as StandardSubscriptionLicence; CreditSubscriptionLicence creditLicence = Clicence as CreditSubscriptionLicence; TimeLimitedSubscriptionLicence timeLicence = Tlicence as TimeLimitedSubscriptionLicence; if (Slicence == null) { // All products must have the same products purchased List<StandardSubscriptionLicenceProduct> standardProducts = Slicence.SubscribedProducts; //Do whatever } else if (Clicence == null) { // All products must have a valid Credit entitlement & Credit interval List<CreditSubscriptionLicenceProduct> creditProducts = Clicence.SubscribedProducts; //Do whatever } else if (Tlicence == null) { // All products must have a valid Time entitlement // All products must have a valid Credit entitlement & Credit interval List<TimeLimitedSubscriptionLicenceProduct> creditProducts = Tlicence.SubscribedProducts; //Do whatever } else throw new InvalidSubscriptionLicenceException("Invalid Licence type"); //More code... } But later I thought in a best one. This is the final version I am using. //Version Improve 2 // Min 1 cast, Max 3 Casts // Do not complain about CA1800:DoNotCastUnnecessarily private void ValidateSubscriptionLicenceProducts(SubscriptionLicence licence) { StandardSubscriptionLicence standardLicence = null; CreditSubscriptionLicence creditLicence = null; TimeLimitedSubscriptionLicence timeLicence = null; if (StandardSubscriptionLicence.TryParse(licence, out standardLicence)) { // All products must have the same products purchased List<StandardSubscriptionLicenceProduct> standardProducts = standardLicence.SubscribedProducts; //Do whatever } else if (CreditSubscriptionLicence.TryParse(licence, out creditLicence)) { // All products must have a valid Credit entitlement & Credit interval List<CreditSubscriptionLicenceProduct> creditProducts = creditLicence.SubscribedProducts; //Do whatever } else if (TimeLimitedSubscriptionLicence.TryParse(licence, out timeLicence)) { // All products must have a valid Time entitlement List<TimeLimitedSubscriptionLicenceProduct> timeProducts = timeLicence.SubscribedProducts; //Do whatever } else throw new InvalidSubscriptionLicenceException("Invalid Licence type"); //More code... } //Example of TryParse in CreditSubscriptionLicence public static bool TryParse(SubscriptionLicence baseLicence, out CreditSubscriptionLicence creditLicence) { creditLicence = baseLicence as CreditSubscriptionLicence; if (creditLicence != null) return true; else return false; } It requires a change in the classes StandardSubscriptionLicence, CreditSubscriptionLicence and TimeLimitedSubscriptionLicence to have a "tryparse" method (copied below in the code). This version I think it will cast as minimum only once and as maximum three. What do you think about improve 2? Is there a best way of doing it?

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  • Simple prime number program - Weird issue with threads C#

    - by Para
    Hi! This is my code: using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading; namespace FirePrime { class Program { static bool[] ThreadsFinished; static bool[] nums; static bool AllThreadsFinished() { bool allThreadsFinished = false; foreach (var threadFinished in ThreadsFinished) { allThreadsFinished &= threadFinished; } return allThreadsFinished; } static bool isPrime(int n) { if (n < 2) { return false; } if (n == 2) { return true; } if (n % 2 == 0) { return false; } int d = 3; while (d * d <= n) { if (n % d == 0) { return false; } d += 2; } return true; } static void MarkPrimes(int startNumber,int stopNumber,int ThreadNr) { for (int j = startNumber; j < stopNumber; j++) nums[j] = isPrime(j); lock (typeof(Program)) { ThreadsFinished[ThreadNr] = true; } } static void Main(string[] args) { int nrNums = 100; int nrThreads = 10; //var threadStartNums = new List<int>(); ThreadsFinished = new bool[nrThreads]; nums = new bool[nrNums]; //var nums = new List<bool>(); nums[0] = false; nums[1] = false; for(int i=2;i<nrNums;i++) nums[i] = true; int interval = (int)(nrNums / nrThreads); //threadStartNums.Add(2); //int aux = firstStartNum; //int i = 2; //while (aux < interval) //{ // aux = interval*i; // i=i+1; // threadStartNums.Add(aux); //} int startNum = 0; for (int i = 0; i < nrThreads; i++) { var _thread = new System.Threading.Thread(() => MarkPrimes(startNum, Math.Min(startNum + interval, nrNums), i)); startNum = startNum + interval; //set the thread to run in the background _thread.IsBackground = true; //start our thread _thread.Start(); } while (!AllThreadsFinished()) { Thread.Sleep(1); } for (int i = 0; i < nrNums; i++) if(nums[i]) Console.WriteLine(i); } } } This should be a pretty simple program that is supposed to find and output the first nrNums prime numbers using nrThreads threads working in parallel. So, I just split nrNums into nrThreads equal chunks (well, the last one won't be equal; if nrThreads doesn't divide by nrNums, it will also contain the remainder, of course). I start nrThreads threads. They all test each number in their respective chunk and see if it is prime or not; they mark everything out in a bool array that keeps a tab on all the primes. The threads all turn a specific element in another boolean array ThreadsFinished to true when they finish. Now the weird part begins: The threads never all end. If I debug, I find that ThreadNr is not what I assign to it in the loop but another value. I guess this is normal since the threads execute afterwards and the counter (the variable i) is already increased by then but I cannot understand how to make the code be right. Can anyone help? Thank you in advance. P.S.: I know the algorithm is not very efficient; I am aiming at a solution using the sieve of Eratosthenes also with x given threads. But for now I can't even get this one to work and I haven't found any examples of any implementations of that algorithm anywhere in a language that I can understand.

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  • Ext JS Tab Panel - Dynamic Tabs - Tab Exists Not Working

    - by Joey Ezekiel
    Hi Would appreciate if somebody could help me on this. I have a Tree Panel whose nodes when clicked load a tab into a tab panel. The tabs are loading alright, but my problem is duplication. I need to check if a tab exists before adding it to the tab panel. I cant seem to have this resolved and it is eating my brains. This is pretty simple and I have checked stackoverflow and the EXT JS Forums for solutions but they dont seem to work for me or I'm being blind. This is my code for the tree: var opstree = new Ext.tree.TreePanel({ renderTo: 'opstree', border:false, width: 250, height: 'auto', useArrows: false, animate: true, autoScroll: true, dataUrl: 'libs/tree-data.json', root: { nodeType: 'async', text: 'Tool Actions' }, listeners: { render: function() { this.getRootNode().expand(); } } }) opstree.on('click', function(n){ var sn = this.selModel.selNode || {}; // selNode is null on initial selection renderPage(n.id); }); function renderPage(tabId) { var TabPanel = Ext.getCmp('content-tab-panel'); var tab = TabPanel.getItem(tabId); //Ext.MessageBox.alert('TabGet',tab); if(tab){ TabPanel.setActiveTab(tabId); } else{ TabPanel.add({ title: tabId, html: 'Tab Body ' + (tabId) + '', closable:true }).show(); TabPanel.doLayout(); } } }); and this is the code for the Tab Panel new Ext.TabPanel({ id:'content-tab-panel', region: 'center', deferredRender: false, enableTabScroll:true, activeTab: 0, items: [{ contentEl: 'about', title: 'About the Billing Ops Application', closable: true, autoScroll: true, margins: '0 0 0 0' },{ contentEl: 'welcomescreen', title: 'PBRT Application Home', closable: false, autoScroll: true, margins: '0 0 0 0' }] }) Can somebody please help?

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  • boost.serialization and lazy initialization

    - by niXman
    i need to serialize directory tree. i have no trouble with this type: std::map< std::string, // string(path name) std::vector<std::string> // string array(file names in the path) > tree; but for the serialization the directory tree with the content i need other type: std::map< std::string, // string(path name) std::vector< // files array std::pair< std::string, // file name std::vector< // array of file pieces std::pair< // <<<<<<<<<<<<<<<<<<<<<< for this i need lazy initialization std::string, // piece buf boost::uint32_t // crc32 summ on piece > > > > > tree; how can i serialize the object of type "std::pair" in the moment of its serialization?

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  • Hibernate SetParameter driving me nuts.

    - by cbmeeks
    This works hql = "from State where StateCode like 'T%'"; Query query = session.createQuery(hql); This does not hql = "from State where StateCode like :StateCode"; Query query = session.createQuery(hql); query.setParameter("StateCode", "T%"); I get this 1568 [main] DEBUG org.hibernate.hql.ast.ErrorCounter - throwQueryException() : no errors 1596 [main] DEBUG org.hibernate.hql.antlr.HqlSqlBaseWalker - select << begin [level=1, statement=select] 1608 [main] DEBUG org.hibernate.hql.ast.tree.FromElement - FromClause{level=1} : com.kencogroup.kkms.models.State (no alias) -> state0_ 1610 [main] DEBUG org.hibernate.hql.ast.tree.FromReferenceNode - Resolved : {synthetic-alias} -> {synthetic-alias} 1611 [main] DEBUG org.hibernate.hql.ast.tree.DotNode - getDataType() : StateCode -> org.hibernate.type.StringType@a39137 1611 [main] DEBUG org.hibernate.hql.ast.tree.FromReferenceNode - Resolved : {synthetic-alias}.StateCode -> state0_.StateCode SELECT Exception: java.lang.reflect.UndeclaredThrowableException Notice the UndeclaredThrowableException exception. What am I doing wrong? The database is SQL Server 2008 if that helps. But like I said, other queries work just fine. Thanks

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  • How to avoid an HttpException due to timeout

    - by Dan
    I'm working on a website powered by .NET asp/C# code. The clients require that sessions have a 25 minute timeout. However, sometimes the site is used, and a user stays connected for long periods of time (longer than 25 mins). Session_End is triggered: protected void Session_End(Object sender, EventArgs e) { Hashtable trackingInformaiton = (Hashtable)Application["trackingInformation"]; trackingInformaiton.Remove(Session["trackingID"]); } The user returns some time later, but when they interact with the website, they get an error, and we get this email notification: User: Unauthenticated User Error: System.Web.HttpException Description: Failed to load viewstate. The control tree into which viewstate is being loaded must match the control tree that was used to save viewstate during the previous request... The telling part of the stack trace is System.Web.UI.Control.AddedControl. Apparently, the server has thrown away the session data, and is sending new data, but the client is trying to deal with old data. Hence the error that "the control tree into which viewstate is being loaded [doesn't] match the control tree that was used to save the viewstate during the prevoius request." So here's the question. How can I force instruct the user's browser to redirect to a "you're logged out" screen when the connection times out? (Is it something I should add to the Session_End method?)

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  • viewstack causing error 1065 variable not defined issue?

    - by jason
    I've got an flex application where I have a left side TREE control and a viewstack on the right and when someone selects the tree it loads the named viewstack based on the hidden node value of the XML of the tree. But it's throwing a error 1065 variable not defined on a viewstack which worked on the last browser refresh/reload. It's not related to a particular viewstack from what I can tell it just seems to throw the error on certain render events. I've tried to use creationpolicy="all" on the viewstack but it seems to not be of any help. public function treeChanged(event:Event):void { selectedNode=Tree(event.target).selectedItem as XML; //trace(selectedNode.@hidden); //Alert.show([email protected]() + " *"); if([email protected]() == '' || [email protected]() == null){ //Alert.show("NULL !"); return; } mainviewstack.selectedChild = Container(mainviewstack.getChildByName([email protected]())); //Container(mainviewstack.getChildByName(selectedNode.@hidden)); If I add in an alert box before the getchildbyname option the viewstack has time to render and everything works fine, so it leads me to believe the app is not giving it enough time to load the viewstack?

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  • How do I send an XML document to an ASP.NET MVC page for manipuation

    - by Decker
    I have some hierarchical data stored as an multiple XML files on the server according to a vendor's schema. In my ASP.NET MVC (2!) application, I'd like the user to choose one of these hierarchies (i.e. file -- I provide a list in my controller's Index action). When the user selects one to "edit" my edit action should return a page that presents the XML hierarchy (it's a representation of a folder tree). So my thoughts are that the view would return HTML that contained a JQuery on load ajax call back to the server for the XML data -- at which point I would present the tree using one of the many JQuery tree controls. On the client side I'd like the user to manipulate the tree and when done, I'd like to post back the new hierarchy where I would replace the original XML file that represents that hierarchy. So my questions are: What form should I use to send the data down? XML or JSON?. If I send down XML then I would have to not only read the XML -- which JQuery can do -- but I would also have to be able to modify that XML and then send it back. Can I use JQuery to modify this XML DOM? And will all the namespace declarations be preserved? What form should I send the data back? If I originally sent the client the hierarchy as JSON (using JsonResult), then presumably I would have a hierarchy of javascript objects. What options would I have to post that back? Would I have to recreate the XML reprentation on the client and post that back? Or should I serialize back to JSON, post that to the server, and then have the server do the work of recreating the XML according to the schema. Thanks for any advice.

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  • JQuery printfunction: no content, no view

    - by Joris
    I got a JQuery printfunction: function doPrintPage() { myWindow = window.open('', '', 'titlebar=yes,menubar=yes,status=yes,scrollbars=yes,width=800,height=600'); myWindow.document.open(); myWindow.document.write(document.getElementById("studentnummer").value); myWindow.document.write(document.getElementById("Voornaam").value + " " + document.getElementById("Tussenvoegsel").value + " " + document.getElementById("Achternaam").value); myWindow.document.write("</br>"); myWindow.document.write("Result"); myWindow.document.write(document.getElementById('tab1').innerHTML); myWindow.document.write("</br>"); myWindow.document.write("Tree"); myWindow.document.write(document.getElementById('tab2').innerHTML); myWindow.document.write("</br>"); myWindow.document.write("Open"); myWindow.document.write(document.getElementById('tab3').innerHTML); myWindow.document.write("</br>"); myWindow.document.write("Free"); myWindow.document.write(document.getElementById('tab4').innerHTML); myWindow.document.close(); myWindow.focus(); } There are 3 gridviews (elements in "tab#"), and on the page that is generated by this script, eacht gridview gets a header (Results, Tree, Open, Free). It is possible that there is no gridview for "Tree". It would be nice if the "tree" header wouldn't be shown either. EDIT: I tried this: if ($('tab4')[0]) {myWindow.document.write("Free"); myWindow.document.write(document.getElementById('tab4').innerHTML); but it seems not to work either... Anyone knows the solution?

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  • jsTree: How to create a new ID for the new added node?

    - by marknt15
    Hi, I can normally get the ID of the default tree nodes but my problem is onCreate then jsTree will add a new node but it doesn't have an ID. My question is how can I add an ID to the newly created tree node? What I'm thinking to do is adding the ID HTML attribute to the newly created tree node but how? I need to get the ID of all of the nodes because it will serve as a reference for the node's respective div storage. HTML code: <div class="demo" id="demo_1"> <ul> <li id="phtml_1" class="file"><a href="#"><ins>&nbsp;</ins>Root node 1</a></li> <li id="phtml_2" class="file"><a href="#"><ins>&nbsp;</ins>Root node 2</a></li> </ul> </div> JS code: $("#demo_1").tree({ ui : { theme_name : "apple" }, callback : { onrename : function (NODE, TREE_OBJ) { alert(TREE_OBJ.get_text(NODE)); alert($(NODE).attr('id')); } } }); Cheers, Mark

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  • Find three numbers appeared only once

    - by shilk
    In a sequence of length n, where n=2k+3, that is there are k unique numbers appeared twice and three numbers appeared only once. The question is: how to find the three unique numbers that appeared only once? for example, in sequence 1 1 2 6 3 6 5 7 7 the three unique numbers are 2 3 5. Note: 3<=n<1e6 and the number will range from 1 to 2e9 Memory limits: 1000KB , this implies that we can't store the whole sequence. Method I have tried(Memory limit exceed): I initialize a tree, and when read in one number I try to remove it from the tree, if the remove returns false(not found), I add it to the tree. Finally, the tree has the three numbers. It works, but is Memory limit exceed. I know how to find one or two such number(s) using bit manipulation. So I wonder if we can find three using the same method(or some method similar)? Method to find one/two number(s) appeared only once: If there is one number appeared only once, we can apply XOR to the sequence to find it. If there are two, we can first apply XOR to the sequence, then separate the sequence into 2 parts by one bit of the result that is 1, and again apply XOR to the 2 parts, and we will find the answer.

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  • SWT Drag and Drop support for Text widget

    - by bryantsai
    I've written an application recently using SWT. In one of its dialog box, I have a few widgets, one of which is Text, which is designed to support DND with other widgets. I've first added DND support for the 2 Tree widgets on the same dialog box (both drag source and drop target). Before I added DND support for that Text widget, I noticed that on Linux platform (gtk), SWT Text widget automatically get drag and drop support. That is, I can already drag from the other Tree widgets and drop on this Text (at any position to inserted there), as well as selecting and dragging any text from this Text to other Tree or Text widget. However, this is only working on Linux platform but not on Windows. The same program, if running on Windows, will not have any DND support for that Text widget (Tree widgets of course have DND support since I specifically write for them). So here's what I want to achieve on Windows as well: drop text at any position in Text widget. before dropping and while hovering, able to see the caret position clearly where the intended position to drop. caret position should move along with the mouse cursor. support multi-line in Text widget SOLUTION: DropTarget target = new DropTarget(sytledText, DND.DROP_MOVE | DND.DROP_COPY); target.setTransfer(new Transfer[] { TextTransfer.getInstance() }); target.addDropListener(new StyleTextDropTargetEffect(sytledText)); Use StyledText instead of Text widget Use StyledTextDropTargetEffect (or extend it) and add it as dr op listener

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  • Query notation for the sitecore 'source' field in template builder

    - by M.R.
    I am trying to set the the source field of a template using the query notation (or xpath - whichever works), but none of them seems to be working. My content tree is a multisite content tree: France --Page 1 ----Page1A -------Page1AA --Page 2 --Page 3 --METADATA ----Regions US --Page 1 ----Page1A -------Page1AA --Page 2 --Page 3 --METADATA ----Regions Each site has its own METADATA folder, and I want it so that when adding a page inside each of the main country nodes, I want the values to reflect whatever is in the METADATA of that site. I have two different fields for now - a droplink and a treelistex field. So I thought I can just get the parent item that is a country site, and get the metadata folder for that. When I put the following query in both the fields, I get different results: query:./ancestor::*[@@templatename='CountryHome']/METADATA/Regions/* For the droplink field, I get only the first Region (one item) For the treelistex field, I get the entire content tree I then tried to modify the query a little bit and took the 'query' notation out ./ancestor::*[@@templatename='CountryHome']/METADATA/Regions/* If I go to the developer center/xpath builder, and set the context node to any item underneath the main country site, it returns me exactly what I need, but when I put this in the source, I get the entire content tree in both the cases. Help!

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