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  • How does static code run with multiple threads?

    - by Krisc
    I was reading http://stackoverflow.com/questions/1511798/threading-from-within-a-class-with-static-and-non-static-methods and I am in a similar situation. I have a static method that pulls data from a resource and creates some runtime objects based on the data. static class Worker{ public static MyObject DoWork(string filename){ MyObject mo = new MyObject(); // ... does some work return mo; } } The method takes awhile (in this case it is reading 5-10mb files) and returns an object. I want to take this method and use it in a multiple thread situation so I can read multiple files at once. Design issues / guidelines aside, how would multiple threads access this code? Let's say I have something like this... class ThreadedWorker { public void Run() { Thread t = new Thread(OnRun); t.Start(); } void OnRun() { MyObject mo = Worker.DoWork("somefilename"); mo.WriteToConsole(); } } Does the static method run for each thread, allowing for parallel execution?

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  • How to best future proof my application that needs to connect to Outlook?

    - by Troy
    I have a contact management application written in Delphi which has a “Sync with Outlook” feature that I developed 10 years ago. Now, I’m going back to add some features and fix some bugs. This sync feature uses the Outlook object model to get started, but it has an optional mode called “Use MAPI Enhancements” where it uses pure MAPI to speed up how it looks for changes, and it allows notes to be synced w/ RTF instead of just plain text. I'm wondering if supporting two parallel paths of execution is a good idea or not. If I went with all MAPI, I believe I'd avoid some security prompts, and I'd avoid situations where anti-virus has "script-blocking" features which block my app from connecting to Outlook. But I believe that on the down side, my 32-bit app would not be able to to connect with 64-bit Outlook 2010 using MAPI. And I wonder about the future of MAPI in general. If I stick with the Outlook object model, will my 32-bit app be able to connect to the Outlook object model (since it's out of process COM)? If so, this is a compelling reason to keep my Outlook object model execution path in place. But if not, and if my app needs to be compiled for x64, then why not just go with pure MAPI?

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  • KODO: how set up fetch plan for bidirectional relationships?

    - by BestPractices
    Running KODO 4.2 and having an issue inefficient queries being generated by KODO. This happens when fetching an object that contains a collection where that collection has a bidrectional relationship back to the first object. Class Classroom { List<Student> _students; } Class Student { Classroom _classroom; } If we create a fetch plan to get a list of Classrooms and their corresponding Students by setting up the following fetch plan: fetchPlan.addField(Classroom.class,”_students”); This will result in two queries (get the classrooms and then get all students that are in those classrooms), which is what we would expect. However, if we include the reference back to the classroom in our fetch plan in order for the _classroom field to get populated by doing fetchPlan.addField(Student.class, “_classroom”), this will result in X number of additional queries where X is the number of students in each classroom. Can anyone explain how to fix this? KODO already has the original Classroom objects at the point that it's executing the queries to retrieve the Classroom objects and set them in each Student object's _classroom field. So I would expect KODO to simply set those objects in the _classroom field on each Student object accordingly and not go back to the database. Once again, the documentation is sorely lacking with Kodo/JDO/OpenJPA but from what I've read it should be able to do this more efficiently. Note-- EAGER_FETCH.PARALLEL is turned on and I have tried this with caching (query and data caches) turned on and off and there is no difference in the resultant queries.

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  • Trigger ad-hoc activity within a workflow

    - by Chris Taylor
    I am looking to use WF 4 to replace an existing workflow solution we have. One feature that is currently used in the existing workflow engine is the ability to cancel a current activity and loopback to a FlowSwitch type activity. So given the following crude workflow where we start at 'O' and base in the input data the workflow follows the path to 'A2' which is currently blocking on s bookmark waiting for input. ---------A1--\ | \ /\ \ O------- ---->--(A2)-------| ^ \/ / | | | / | | ---------A3--/ | | | |----------------------| However in the meantime some out of band data comes in that means we should cancel 'A2' and return to the FlowSwitch to re-evaluate based on the new data. The question is what is the best way to handle the out of band data that arrived? My initial guess is to have a Parallel activity with one branch waiting for out of band data and the other branch containing the workflow sequence described above. If data came in on the brach waiting for the out of band data, how would I cancel the current activity in the workflow and force it to return to the FlowSwitch. Or of course is there a better way to handle this. I have not actually done any work with the WF4 stuff for WF3 for that matter so I might be missing something obvious here.

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  • How to optimize Conway's game of life for CUDA?

    - by nlight
    I've written this CUDA kernel for Conway's game of life: global void gameOfLife(float* returnBuffer, int width, int height) { unsigned int x = blockIdx.x*blockDim.x + threadIdx.x; unsigned int y = blockIdx.y*blockDim.y + threadIdx.y; float p = tex2D(inputTex, x, y); float neighbors = 0; neighbors += tex2D(inputTex, x+1, y); neighbors += tex2D(inputTex, x-1, y); neighbors += tex2D(inputTex, x, y+1); neighbors += tex2D(inputTex, x, y-1); neighbors += tex2D(inputTex, x+1, y+1); neighbors += tex2D(inputTex, x-1, y-1); neighbors += tex2D(inputTex, x-1, y+1); neighbors += tex2D(inputTex, x+1, y-1); __syncthreads(); float final = 0; if(neighbors < 2) final = 0; else if(neighbors 3) final = 0; else if(p != 0) final = 1; else if(neighbors == 3) final = 1; __syncthreads(); returnBuffer[x + y*width] = final; } I am looking for errors/optimizations. Parallel programming is quite new to me and I am not sure if I get how to do it right. The rest of the app is: Memcpy input array to a 2d texture inputTex stored in a CUDA array. Output is memcpy-ed from global memory to host and then dealt with. As you can see a thread deals with a single pixel. I am unsure if that is the fastest way as some sources suggest doing a row or more per thread. If I understand correctly NVidia themselves say that the more threads, the better. I would love advice on this on someone with practical experience.

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  • Is there a max recommended size on bundling js/css files due to chunking or packet loss?

    - by George Mauer
    So we all have heard that its good to bundle your javascript. Of course it is, but it seems to me that the story is too simple. See if my logic makes sense here. Obviously fewer HTTP requests is fewer round trips and hence better. However - and I don't know much about bare http - aren't http responses sent in chunks? And if a file is larger than one of those chunks doesn't it have to be downloaded as multiple (possibly synchronous?) round trips? As opposed to this, several requests for files just under the chunking size would arrive much quicker since modern web browsers download resources like javascripts in parallel. Even if chunking is not an issue, it seems like there would be some max recommended size just due to likelyhood of packet loss alone since a bundled file must wait till it is entirely downloaded to execute, versus the more lenient native rule that scripts must execute in order. Obviously there's also matters of browser caching and code volatility to consider but can someone confirm this or explain why I'm off base? Does anyone have any numbers to put to it?

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  • Boost binding a function taking a reference

    - by Jamie Cook
    Hi all, I am having problems compiling the following snippet int temp; vector<int> origins; vector<string> originTokens = OTUtils::tokenize(buffer, ","); // buffer is a char[] array // original loop BOOST_FOREACH(string s, originTokens) { from_string(temp, s); origins.push_back(temp); } // I'd like to use this to replace the above loop std::transform(originTokens.begin(), originTokens.end(), origins.begin(), boost::bind<int>(&FromString<int>, boost::ref(temp), _1)); where the function in question is // the third parameter should be one of std::hex, std::dec or std::oct template <class T> bool FromString(T& t, const std::string& s, std::ios_base& (*f)(std::ios_base&) = std::dec) { std::istringstream iss(s); return !(iss >> f >> t).fail(); } the error I get is 1>Compiling with Intel(R) C++ 11.0.074 [IA-32]... (Intel C++ Environment) 1>C:\projects\svn\bdk\Source\deps\boost_1_42_0\boost/bind/bind.hpp(303): internal error: assertion failed: copy_default_arg_expr: rout NULL, no error (shared/edgcpfe/il.c, line 13919) 1> 1> return unwrapper<F>::unwrap(f, 0)(a[base_type::a1_], a[base_type::a2_]); 1> ^ 1> 1>icl: error #10298: problem during post processing of parallel object compilation Google is being unusually unhelpful so I hope that some one here can provide some insights.

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  • What can I read from the iPad Camera Connection Kit?

    - by HELVETICADE
    I'm building a small controller device that I'd like to partner with a computer. I've settled on using OSC out from my custom built hardware and am pretty satisfied with what I can get from WOscLib. Two goals I'd like to achieve are portability and a very ratio between battery:computing power, and this has lured me towards using iPhoneOS to accomplish my goals. I think the iPad would suit my needs perfectly, except that using wifi to broadcast OSC out from my device requires a third device and would destroy the goal of portability, whilst also introducing potential latency and stability headaches. My question is pretty simple: Can I push my OSC-out FROM my controller TO an iPad via USB and the Camera Connection Kit? If I could accomplish this, the two major goals of my project would be fulfilled very nicely. This seems like it should be a simple little question, but researching this obsessively over the past few weeks has left me more almost more uncertain than if I had done no research at all. I'd really like some more confidence before I go down this route, and it seems like it should be possible. Any insight would be very, very appreciated.

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  • Neural Networks or Human-computer interaction

    - by Shahin
    I will be entering my third year of university in my next academic year, once I've finished my placement year as a web developer, and I would like to hear some opinions on the two modules in the Title. I'm interested in both, however I want to pick one that will be relevant to my career and that I can apply to systems I develop. I'm doing an Internet Computing degree, it covers web development, networking, database work and programming. Though I have had myself set on becoming a web developer I'm not so sure about that any more so am trying not to limit myself to that area of development. I know HCI would help me as a web developer, but do you think it's worth it? Do you think Neural Network knowledge could help me realistically in a system I write in the future? Thanks. EDIT: Hi guys, I thought it would be useful to follow-up with what I decided to do and how it's worked out. I picked Artificial Neural Networks over HCI, and I've really enjoyed it. Having a peek into cognitive science and machine learning has ignited my interest for the subject area, and I will be hoping to take on a postgraduate project a few years from now when I can afford it. I have got a job which I am starting after my final exams (which are in a few days) and I was indeed asked if I had done a module in HCI or similar. It didn't seem to matter, as it isn't a front-end developer position! I would recommend taking the module if you have it as an option, as well as any module consisting of biological computation, it will open up more doors should you want to go onto postgraduate research in the future. Thanks again, Shahin

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  • Is it possible to have asynchronous processing

    - by prashant2361
    Hi, I have a requirement where I need to send continuous updates to my clients. Client is browser in this case. We have some data which updates every sec, so once client connects to our server, we maintain a persistent connection and keep pushing data to the client. I am looking for suggestions of this implementation at the server end. Basically what I need is this: 1. client connects to server. I maintain the socket and metadata about the socket. metadata contains what updates need to be send to this client 2. server process now waits for new client connections 3. One other process will have the list of all the sockets opened and will go through each of them and send the updates if required. Can we do something like this in Apache module: 1. Apache process gets the new connection. It maintains the state for the connection. It keeps the state in some global memory and returns back to root process to signify that it is done so that it can accept the new connection 2. the Apache process though has returned the status to root process but it is also executing in parallel where it going through its global store and sending updates to the client, if any. So can a Apache process do these things: 1. Have more than one connection associated with it 2. Asynchronously waiting for new connection and at the same time processing the previous connections? Regards Prashant

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  • What should be taught in a "Fundamentals of programming" course at university?

    - by Dervin Thunk
    I have started a new question (see here), because I think the topic is of importance in a more general form. The question is now: If you were a professor at a Computer Science Dept. in some university, what would make it into your course? This is a programming course, second term, first year computer science/computer engineering. Remember you have a limited amount of time, and students are of different levels of competence, and some may be scientists, but some will also go on to be programmers in companies of different kinds. You have to cater to all. Bonus: What language? (Although see this question for my current thoughts about this...) Maybe you want to attach a course outline from some university? See here for an even more general question about this. Answer: I can't really summarize this post... I guess it was too subjective. However, it looks like we have to cover the history of computing up to a certain extent, computer architecture (memory, registers, whatever), C, and finally some basic algos and data structures in a problem solving fashion. This will be the bare bones of the course. Thanks all. I will accept the most voted up answer to close the thread, as it should be done.

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  • Using SMO to call Database.ExecuteNonQuery() concurrently?

    - by JimDaniel
    I have been banging my head against the wall trying to figure out how I can run update scripts concurrently against multiple databases in a single SQL Server instance using SMO. Our environments have an ever-increasing number of databases which need updating, and iterating through one at a time is becoming a problem (too slow). From what I understand SMO does not support concurrent operations, and my tests have bore that out. There seems to be shared memory at the Server object level, for things like DataReader context, keeps throwing exceptions such as "reader is already open." I apologize for not having the exact exceptions I am getting. I will try to get them and update this post. I am no expert on SMO and just feeling my way through to be honest. Not really sure I am approaching it the right way, but it's something that has to be done, or our productivity will slow to a crawl. So how would you guys do something like this? Am I using the wrong technology with SMO? All I am wanting to do is execute sql scripts against databases in a single sql server instance in parallel. Thanks for any help you can give, Daniel

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  • unroll nested for loops in C++

    - by Hristo
    How would I unroll the following nested loops? for(k = begin; k != end; ++k) { for(j = 0; j < Emax; ++j) { for(i = 0; i < N; ++i) { if (j >= E[i]) continue; array[k] += foo(i, tr[k][i], ex[j][i]); } } } I tried the following, but my output isn't the same, and it should be: for(k = begin; k != end; ++k) { for(j = 0; j < Emax; ++j) { for(i = 0; i+4 < N; i+=4) { if (j >= E[i]) continue; array[k] += foo(i, tr[k][i], ex[j][i]); array[k] += foo(i+1, tr[k][i+1], ex[j][i+1]); array[k] += foo(i+2, tr[k][i+2], ex[j][i+2]); array[k] += foo(i+3, tr[k][i+3], ex[j][i+3]); } if (i < N) { for (; i < N; ++i) { if (j >= E[i]) continue; array[k] += foo(i, tr[k][i], ex[j][i]); } } } } I will be running this code in parallel using Intel's TBB so that it takes advantage of multiple cores. After this is finished running, another function prints out what is in array[] and right now, with my unrolling, the output isn't identical. Any help is appreciated. Thanks, Hristo

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  • help me reason about F# threads

    - by Kevin Cantu
    In goofing around with some F# (via MonoDevelop), I have written a routine which lists files in a directory with one thread: let rec loop (path:string) = Array.append ( path |> Directory.GetFiles ) ( path |> Directory.GetDirectories |> Array.map loop |> Array.concat ) And then an asynchronous version of it: let rec loopPar (path:string) = Array.append ( path |> Directory.GetFiles ) ( let paths = path |> Directory.GetDirectories if paths <> [||] then [| for p in paths -> async { return (loopPar p) } |] |> Async.Parallel |> Async.RunSynchronously |> Array.concat else [||] ) On small directories, the asynchronous version works fine. On bigger directories (e.g. many thousands of directories and files), the asynchronous version seems to hang. What am I missing? I know that creating thousands of threads is never going to be the most efficient solution -- I only have 8 CPUs -- but I am baffled that for larger directories the asynchronous function just doesn't respond (even after a half hour). It doesn't visibly fail, though, which baffles me. Is there a thread pool which is exhausted? How do these threads actually work?

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  • Create new or update existing entity at one go with JPA

    - by Alex R
    A have a JPA entity that has timestamp field and is distinguished by a complex identifier field. What I need is to update timestamp in an entity that has already been stored, otherwise create and store new entity with the current timestamp. As it turns out the task is not as simple as it seems from the first sight. The problem is that in concurrent environment I get nasty "Unique index or primary key violation" exception. Here's my code: // Load existing entity, if any. Entity e = entityManager.find(Entity.class, id); if (e == null) { // Could not find entity with the specified id in the database, so create new one. e = entityManager.merge(new Entity(id)); } // Set current time... e.setTimestamp(new Date()); // ...and finally save entity. entityManager.flush(); Please note that in this example entity identifier is not generated on insert, it is known in advance. When two or more of threads run this block of code in parallel, they may simultaneously get null from entityManager.find(Entity.class, id) method call, so they will attempt to save two or more entities at the same time, with the same identifier resulting in error. I think that there are few solutions to the problem. Sure I could synchronize this code block with a global lock to prevent concurrent access to the database, but would it be the most efficient way? Some databases support very handy MERGE statement that updates existing or creates new row if none exists. But I doubt that OpenJPA (JPA implementation of my choice) supports it. Event if JPA does not support SQL MERGE, I can always fall back to plain old JDBC and do whatever I want with the database. But I don't want to leave comfortable API and mess with hairy JDBC+SQL combination. There is a magic trick to fix it using standard JPA API only, but I don't know it yet. Please help.

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  • Which MySQL Fork/Version to Pick??

    - by Drew
    As most of you know, Sun acquired MySQL (and later Oracle acquired Sun), and during these acquisitions, there were a lot of FUD in MySQL community which resulted in creation of various forks. Today we have MySQL from MySQL, Percona (XtraDB) MySQL, OurDelta MySQL, MariaDB, Drizzle to name a few. Which brings us to the source of the problem. We are in the process of upgrading our databases (hardware/software) and I would like to know which one of the forks should I go with. Each has their own set of pros/cons. We are currently using MySQL 5.0.x from MySQL/Linux on an 8-core machine. Our new hardware is a monster with 32 cores and 32GB of memory connecting to a fast NetApp Storage via FC. I would like to stick with MySQL from MySQL but I have heard horror stories on how badly MySQL 5.1 performs on many cores. I have also heard that MySQL 5.4 performs better on multi-core machines but that's still not production ready. In addition, I have also heard a lot of good things about Percona builds. This is what I know so far: MySQL 5.1 from MySQL: Reliable choice, but doesn't scale well on a big machine Percona: Scales well, good backing company. I don't have much experience with it MariaDB: Don't know much about it besides that it was founded by Original MySQL developers (including Monty) OurDelta: Don't know much Drizzle: Mostly optimized for cloud computing I would like to know what's the general notion about this problem. Which build/version should I go with? How are you guys picking your builds/versions? Thanks!

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  • Threading calls to web service in a web service - (.net 2.0)

    - by Ryan Ternier
    Got a question regarding best practices for doing parallel web service calls, in a web service. Our portal will get a message, split that message into 2 messages, and then do 2 calls to our broker. These need to be on separate threads to lower the timeout. One solution is to do something similar to (pseudo code): XmlNode DNode = GetaGetDemoNodeSomehow(); XmlNode ENode = GetAGetElNodeSomehow(); XmlNode elResponse; XmlNode demResponse; Thread dThread = new Thread(delegate { //Web Service Call GetDemographics d = new GetDemographics(); demResponse = d.HIALRequest(DNode); }); Thread eThread = new Thread(delegate { //Web Service Call GetEligibility ge = new GetEligibility(); elResponse = ge.HIALRequest(ENode); }); dThread.Start(); eThread.Start(); dThread.Join(); eThread.Join(); //combine the resulting XML and return it. //Maybe throw a bit of logging in to make architecture happy Another option we thought of is to create a worker class, and pass it the service information and have it execute. This would allow us to have a bit more control over what is going on, but could add additional overhead. Another option brought up would be 2 asynchronous calls and manage the returns through a loop. When the calls are completed (success or error) the loop picks it up and ends. The portal service will be called about 50,000 times a day. I don't want to gold plate this sucker. I'm looking for something light weight. The services that are being called on the broker do have time out limits set, and are already heavily logged and audited, so I'm not worried on that part. This is .NET 2.0 , and as much as I would love to upgrade I can't right now. So please leave all the goodies of 2.0 out please.

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  • Client-server synchronization pattern / algorithm?

    - by tm_lv
    I have a feeling that there must be client-server synchronization patterns out there. But i totally failed to google up one. Situation is quite simple - server is the central node, that multiple clients connect to and manipulate same data. Data can be split in atoms, in case of conflict, whatever is on server, has priority (to avoid getting user into conflict solving). Partial synchronization is preferred due to potentially large amounts of data. Are there any patterns / good practices for such situation, or if you don't know of any - what would be your approach? Below is how i now think to solve it: Parallel to data, a modification journal will be held, having all transactions timestamped. When client connects, it receives all changes since last check, in consolidated form (server goes through lists and removes additions that are followed by deletions, merges updates for each atom, etc.). Et voila, we are up to date. Alternative would be keeping modification date for each record, and instead of performing data deletes, just mark them as deleted. Any thoughts?

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  • Storing date/times as UTC in database

    - by James
    I am storing date/times in the database as UTC and computing them inside my application back to local time based on the specific timezone. Say for example I have the following date/time: 01/04/2010 00:00 Say it is for a country e.g. UK which observes DST (Daylight Savings Time) and at this particular time we are in daylight savings. When I convert this date to UTC and store it in the database it is actually stored as: 31/03/2010 23:00 As the date would be adjusted -1 hours for DST. This works fine when your observing DST at time of submission. However, what happens when the clock is adjusted back? When I pull that date from the database and convert it to local time that particular datetime would be seen as 31/03/2009 23:00 when in reality it was processed as 01/04/2010 00:00. Correct me if I am wrong but isn't this a bit of a flaw when storing times as UTC? Example of Timezone conversion Basically what I am doing is storing the date/times of when information is being submitted to my system in order to allow users to do a range report. Here is how I am storing the date/times: public DateTime LocalDateTime(string timeZoneId) { var tzi = TimeZoneInfo.FindSystemTimeZoneById(timeZoneId); return TimeZoneInfo.ConvertTimeFromUtc(DateTime.UtcNow, tzi).ToLocalTime(); } Storing as UTC: var localDateTime = LocalDateTime("AUS Eastern Standard Time"); WriteToDB(localDateTime.ToUniversalTime());

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  • ssh & script problem

    - by Nishanth
    I am having a strange problem while doing ssh. I am not sure where the term Unmatched ` is coming from. What I need to do is run script that logs information of what I am doing on the terminal to text file. After ssh - Sun Microsystems Inc. SunOS 5.8 Generic Patch October 2001 This is /etc/motd, last updated 3 Feb 2003. To learn about the UCS system and other aspects of computing at UL-Lafayette visit our home page http://helpdesk.louisiana.edu/ . For more information about system use, contact the Help Desk, Stephens Hall, Room 201, 482-5516 (x25516), during normal UL office hours; or send e-mail to [email protected]. ATTENTION: Unsecure Telnet and FTP will be turned off soon. Please make arrange to use ssh or sftp. Putty(telnet) and WinSCP(ftp) would be a good replacement. Unmatched ` d13.ucs.louisiana.edu% bash bash-2.04$ script -a myInformation.txt Script started, file is myInformation.txt Unmatched ` d13.ucs.louisiana.edu% When I tried to start the script with name myInformation.txt, you can see the message I am getting - Script started, file is myInformation.txt. But again I am getting that message Unmatched ` and is coming out of bash, as you can notice. What is the problem ? Any insights suggested would be very great. Note: file with name myInformation.txt is being created but nothing goes in to it. As I have even tried running certain commands like ls and then exited the script with ctrl+d. But when I open the file, nothing is there.

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  • jQuery: Trouble with draggable across cloned elements

    - by Rosarch
    I'm trying to implement: User drags a draggable li to a droppable li. The original li is no longer draggable A new li is cloned from the original li, and is appended to the droppable li. I can't get it to work. function moveToTerm(original_course, helper, term) { var cloned_course = original_course.clone(true); original_course.addClass('already-scheduled'); original_course.draggable('disable'); cloned_course.draggable(); cloned_course.appendTo(term).hide().fadeIn('slow'); } This works fine, except now the cloned_course is not draggable. A droppable li: <li class="term ui-droppable"> <strong>Fall 2010</strong> <li class="course">Computing Cultures</li> <!-- this course was just dropped. I want it to be draggable but it's not --> <li class="course ui-draggable" style="display: list-item;">New Media and Society</li> </li> What am I doing wrong?

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  • Is it possible to send OSC commands to an iPad via the Camera Connection Kit?

    - by HELVETICADE
    I'm building a small controller device that I'd like to partner with a computer. I've settled on using OSC out from my custom built hardware and am pretty satisfied with what I can get from WOscLib. Two goals I'd like to achieve are portability and a very nice ratio between battery:computing power, and this has lured me towards using iPhoneOS to accomplish my goals. I think the iPad would suit my needs perfectly, except that using wifi to broadcast OSC out from my device requires that device to be connected to a third device with a wifi chip, and this would destroy the goal of portability, whilst also introducing potential latency and stability headaches. My question is pretty simple: Can I push OSC commands FROM my controller TO an iPad via USB and the Camera Connection Kit? If I could accomplish this, the two major goals of my project would be fulfilled very nicely. This seems like it should be a simple little question, but researching this obsessively over the past few weeks has left me more almost more uncertain than if I had done no research at all. I'd really like some more confidence before I go down this route, and it seems like it should be possible. Any insight would be very, very appreciated.

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  • SQL Server race condition issue with range lock

    - by Freek
    I'm implementing a queue in SQL Server (please no discussions about this) and am running into a race condition issue. The T-SQL of interest is the following: set transaction isolation level serializable begin tran declare @RecordId int declare @CurrentTS datetime2 set @CurrentTS=CURRENT_TIMESTAMP select top 1 @RecordId=Id from QueuedImportJobs with (updlock) where Status=@Status and (LeaseTimeout is null or @CurrentTS>LeaseTimeout) order by Id asc if @@ROWCOUNT> 0 begin update QueuedImportJobs set LeaseTimeout = DATEADD(mi,5,@CurrentTS), LeaseTicket=newid() where Id=@RecordId select * from QueuedImportJobs where Id = @RecordId end commit tran RecordId is the PK and there is also an index on Status,LeaseTimeout. What I'm basically doing is select a record of which the lease happens to be expired, while simultaneously updating the lease time with 5 minutes and setting a new lease ticket. So the problem is that I'm getting deadlocks when I run this code in parallel using a couple of threads. I've debugged it up to the point where I found out that the update statement sometimes gets executing twice for the same record. Now, I was under the impression that the with (updlock) should prevent this (it also happens with xlock btw, not with tablockx). So it actually look like there is a RangeS-U and a RangeX-X lock on the same range of records, which ought to be impossible. So what am I missing? I'm thinking it might have something to do with the top 1 clause or that SQL Server does not know that where Id=@RecordId is actually in the locked range? Deadlock graph: Table schema (simplified):

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  • Thread-safty of boost RNG

    - by Maciej Piechotka
    I have a loop which should be nicely pararellized by insering one openmp pragma: boost::normal_distribution<double> ddist(0, pow(retention, i - 1)); boost::variate_generator<gen &, BOOST_TYPEOF(ddist)> dgen(rng, ddist); // Diamond const std::uint_fast32_t dno = 1 << i - 1; // #pragma omp parallel for for (std::uint_fast32_t x = 0; x < dno; x++) for (std::uint_fast32_t y = 0; y < dno; y++) { const std::uint_fast32_t diff = size/dno; const std::uint_fast32_t x1 = x*diff, x2 = (x + 1)*diff; const std::uint_fast32_t y1 = y*diff, y2 = (y + 1)*diff; double avg = (arr[x1][y1] + arr[x1][y2] + arr[x2][y1] + arr[x2][y2])/4; arr[(x1 + x2)/2][(y1 + y2)/2] = avg + dgen(); } (unless I make an error each execution does not depend on others at all. Sorry that not all of code is inserted). However my question is - are boost RNG thread-safe? They seems to refer to gcc code for gcc so even if gcc code is thread-safe it may not be the case for other platforms.

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  • Help thinking "Pythony"

    - by Josh
    I'm brand new to Python and trying to learn it by replicating the following C++ function into python // determines which words in a vector consist of the same letters // outputs the words with the same letters on the same line void equivalentWords(vector <string> words, ofstream & outFile) { outFile << "Equivalent words\n"; // checkedWord is parallel to the words vector. It is // used to make sure each word is only displayed once. vector <bool> checkedWord (words.size(), false); for(int i = 0; i < words.size(); i++) { if (!checkedWord[i]){ outFile << " "; for(int j = i; j < words.size(); j++){ if(equivalentWords(words[i], words[j], outFile)) { outFile << words[j] << " "; checkedWord[j] = true; } } outFile << "\n"; } } } In my python code (below), rather than having a second vector, I have a list ("words") of lists of a string, a sorted list of the chars in the former string (because strings are immutable), and a bool (that tells if the word has been checked yet). However, I can't figure out how to change a value as you iterate through a list. for word, s_word, checked in words: if not checked: for word1, s_word1, checked1 in words: if s_word1 == s_word: checked1 = True # this doesn't work print word1, print "" Any help on doing this or thinking more "Pythony" is appreciated.

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