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  • Licensing a collaborative research project

    - by Marcus Jones
    I am involved with an international research project which involves many different universities, national labs, and companies. The project is developed by national grants and in-kind support. One task in the project is to develop code to streamline workflow in our domain (energy simulation) by scripting common pre- and post-processing tasks for different tools. We want this code to be freely distributable to the simulation community. How can we ensure that this effort is digestible by the legal departments of these different parties such that the people involved can freely code?

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  • How do history generation algorithms work?

    - by Bane
    I heard of the game Dwarf Fortress, but only now one of the people I follow on Youtube made a commentary on it... I was more than surprised when I noticed how Dwarf Fortress actually generates a history for the world! Now, how do these algorithms work? What do they usually take as input, except the length of the simulation? How specific can they be? And more importantly; can they be made in Javascript, or is Javascript too slow? (I guess this depends on the depth of the simulation, but take Dwarf Fortress as an example.)

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  • Communication between Box2D and libGDX Stage (Scene2D) running in separate threads

    - by atok
    I'm making a physics based 2D game using libGDX and Box2D. I want to move the execution of the simulation out of render thread. I use immutable messages and the BlockingQueue to pass the information about player actions. The Box2D applies forces and runs a frame of simulation. In the next step I would like to sync back the changes and update Scene2D Actors accordingly. Making an immutable copy of the state of the game world and sending it back using Gdx.app.postRunnable() is one option but it seems inefficient. Is there any other option?

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  • How to distribute multiple executions of an app across many machines

    - by Salec
    I've got a simulation app (64-bit windows) that runs without any user interaction. This app gathers information and pushes it to a remote MS SQL Server. What I'd like to do is execute this simulation as many times as I can on multiple machines after our nightly build has finished and it has passed the test suite. If possible I'd love to have the ability to configure it to stop after x total runs or if the entire batch has taken over y hours. I've tried using Visual Studio's built in test framework since we already have a test lab set up with multiple agents. I created a single unit test that simply runs the simulation then I created an ordered test and added that single test multiple times (from what I gather, this is the only way to execute the same unit test more than once). I found that ordered tests are only run on a single agent and not distributed which is very limiting. We use TeamCity to perform our nightly builds and I suspect it's possible to implement this on top of that, but I'm fairly new to TeamCity. We also have Jenkins and Bamboo available and I'm open to any other software that would get the job done presuming it runs on a 64-bit Windows OS. Any suggestions?

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  • Compatibility between Qt and Boost sockets libraries

    - by cake
    Hello In my work, I'm developing a Viewer client for a Offshore simulation server, using sockets to send the simulation data from the Simulator to de Viewer. But, the server uses Boost.asio as it's sockets library. As the client uses Qt for it's GUI, I was wondering if there is any problem in using de Qt Networking library for handling the sockets. Is there any compatibility issues? Thanks in advance, and sorry for my bad english.

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  • Professional Scrum Developer (.NET) Training in London

    - by Martin Hinshelwood
    On the 26th - 30th July in Microsoft’s offices in London Adam Cogan from SSW will be presenting the first Professional Scrum Developer course in the UK. I will be teaching this course along side Adam and it is a fantastic experience. You are split into teams and go head-to-head to deliver units of potentially shippable work in four two hour sprints. The Professional Scrum Developer course is the only course endorsed by both Microsoft and Ken Schwaber and they have worked together very effectively in brining this course to fruition. This course is the brain child of Richard Hundhausen, a Microsoft Regional Director, and both Adam and I attending the Trainer Prep in Sydney when he was there earlier this year. He is a fantastic trainer and no matter where you do this course you can be safe in the knowledge that he has trained and vetted all of the teachers. A tools version of Ken if you will Find a course and register Download this syllabus Download the Scrum Guide What is the Professional Scrum Developer course all about? Professional Scrum Developer course is a unique and intensive five-day experience for software developers. The course guides teams on how to turn product requirements into potentially shippable increments of software using the Scrum framework, Visual Studio 2010, and modern software engineering practices. Attendees will work in self-organizing, self-managing teams using a common instance of Team Foundation Server 2010. Who should attend this course? This course is suitable for any member of a software development team – architect, programmer, database developer, tester, etc. Entire teams are encouraged to attend and experience the course together, but individuals are welcome too. Attendees will self-organize to form cross-functional Scrum teams. These teams require an aggregate of skills specific to the selected case study. Please see the last page of this document for specific details. Product Owners, ScrumMasters, and other stakeholders are welcome too, but keep in mind that everyone who attends will be expected to commit to work and pull their weight on a Scrum team. What should you know by the end of the course? Scrum will be experienced through a combination of lecture, demonstration, discussion, and hands-on exercises. Attendees will learn how to do Scrum correctly while being coached and critiqued by the instructor, in the following topic areas: Form effective teams Explore and understand legacy “Brownfield” architecture Define quality attributes, acceptance criteria, and “done” Create automated builds How to handle software hotfixes Verify that bugs are identified and eliminated Plan releases and sprints Estimate product backlog items Create and manage a sprint backlog Hold an effective sprint review Improve your process by using retrospectives Use emergent architecture to avoid technical debt Use Test Driven Development as a design tool Setup and leverage continuous integration Use Test Impact Analysis to decrease testing times Manage SQL Server development in an Agile way Use .NET and T-SQL refactoring effectively Build, deploy, and test SQL Server databases Create and manage test plans and cases Create, run, record, and play back manual tests Setup a branching strategy and branch code Write more maintainable code Identify and eliminate people and process dysfunctions Inspect and improve your team’s software development process What does the week look like? This course is a mix of lecture, demonstration, group discussion, simulation, and hands-on software development. The bulk of the course will be spent working as a team on a case study application delivering increments of new functionality in mini-sprints. Here is the week at a glance: Monday morning and most of the day Friday will be spent with the computers powered off, so you can focus on sharpening your game of Scrum and avoiding the common pitfalls when implementing it. The Sprints Timeboxing is a critical concept in Scrum as well as in this course. We expect each team and student to understand and obey all of the timeboxes. The timebox duration will always be clearly displayed during each activity. Expect the instructor to enforce it. Each of the ½ day sprints will roughly follow this schedule: Component Description Minutes Instruction Presentation and demonstration of new and relevant tools & practices 60 Sprint planning meeting Product owner presents backlog; each team commits to delivering functionality 10 Sprint planning meeting Each team determines how to build the functionality 10 The Sprint The team self-organizes and self-manages to complete their tasks 120 Sprint Review meeting Each team will present their increment of functionality to the other teams = 30 Sprint Retrospective A group retrospective meeting will be held to inspect and adapt 10 Each team is expected to self-organize and manage their own work during the sprint. Pairing is highly encouraged. The instructor/product owner will be available if there are questions or impediments, but will be hands-off by default. You should be prepared to communicate and work with your team members in order to achieve your sprint goal. If you have development-related questions or get stuck, your partner or team should be your first level of support. Module 1: INTRODUCTION This module provides a chance for the attendees to get to know the instructors as well as each other. The Professional Scrum Developer program, as well as the day by day agenda, will be explained. Finally, the Scrum team will be selected and assembled so that the forming, storming, norming, and performing can begin. Trainer and student introductions Professional Scrum Developer program Agenda Logistics Team formation Retrospective Module 2: SCRUMDAMENTALS This module provides a level-setting understanding of the Scrum framework including the roles, timeboxes, and artifacts. The team will then experience Scrum firsthand by simulating a multi-day sprint of product development, including planning, review, and retrospective meetings. Scrum overview Scrum roles Scrum timeboxes (ceremonies) Scrum artifacts Simulation Retrospective It’s required that you read Ken Schwaber’s Scrum Guide in preparation for this module and course. MODULE 3: IMPLEMENTING SCRUM IN VISUAL STUDIO 2010 This module demonstrates how to implement Scrum in Visual Studio 2010 using a Scrum process template*. The team will learn the mapping between the Scrum concepts and how they are implemented in the tool. After connecting to the shared Team Foundation Server, the team members will then return to the simulation – this time using Visual Studio to manage their product development. Mapping Scrum to Visual Studio 2010 User Story work items Task work items Bug work items Demonstration Simulation Retrospective Module 4: THE CASE STUDY In this module the team is introduced to their problem domain for the week. A kickoff meeting by the Product Owner (the instructor) will set the stage for the why and what that will take during the upcoming sprints. The team will then define the quality attributes of the project and their definition of “done.” The legacy application code will be downloaded, built, and explored, so that any bugs can be discovered and reported. Introduction to the case study Download the source code, build, and explore the application Define the quality attributes for the project Define “done” How to file effective bugs in Visual Studio 2010 Retrospective Module 5: HOTFIX This module drops the team directly into a Brownfield (legacy) experience by forcing them to analyze the existing application’s architecture and code in order to locate and fix the Product Owner’s high-priority bug(s). The team will learn best practices around finding, testing, fixing, validating, and closing a bug. How to use Architecture Explorer to visualize and explore Create a unit test to validate the existence of a bug Find and fix the bug Validate and close the bug Retrospective Module 6: PLANNING This short module introduces the team to release and sprint planning within Visual Studio 2010. The team will define and capture their goals as well as other important planning information. Release vs. Sprint planning Release planning and the Product Backlog Product Backlog prioritization Acceptance criteria and tests Sprint planning and the Sprint Backlog Creating and linking Sprint tasks Retrospective At this point the team will have the knowledge of Scrum, Visual Studio 2010, and the case study application to begin developing increments of potentially shippable functionality that meet their definition of done. Module 7: EMERGENT ARCHITECTURE This module introduces the architectural practices and tools a team can use to develop a valid design on which to develop new functionality. The teams will learn how Scrum supports good architecture and design practices. After the discussion, the teams will be presented with the product owner’s prioritized backlog so that they may select and commit to the functionality they can deliver in this sprint. Architecture and Scrum Emergent architecture Principles, patterns, and practices Visual Studio 2010 modeling tools UML and layer diagrams SPRINT 1 Retrospective Module 8: TEST DRIVEN DEVELOPMENT This module introduces Test Driven Development as a design tool and how to implement it using Visual Studio 2010. To maximize productivity and quality, a Scrum team should setup Continuous Integration to regularly build every team member’s code changes and run regression tests. Refactoring will also be defined and demonstrated in combination with Visual Studio’s Test Impact Analysis to efficiently re-run just those tests which were impacted by refactoring. Continuous integration Team Foundation Build Test Driven Development (TDD) Refactoring Test Impact Analysis SPRINT 2 Retrospective Module 9: AGILE DATABASE DEVELOPMENT This module lets the SQL Server database developers in on a little secret – they can be agile too. By using the database projects in Visual Studio 2010, the database developers can join the rest of the team. The students will see how to apply Agile database techniques within Visual Studio to support the SQL Server 2005/2008/2008R2 development lifecycle. Agile database development Visual Studio database projects Importing schema and scripts Building and deploying Generating data Unit testing SPRINT 3 Retrospective Module 10: SHIP IT Teams need to know that just because they like the functionality doesn’t mean the Product Owner will. This module revisits acceptance criteria as it pertains to acceptance testing. By refining acceptance criteria into manual test steps, team members can execute the tests, recording the results and reporting bugs in a number of ways. Manual tests will be defined and executed using the Microsoft Test Manager tool. As the Sprint completes and an increment of functionality is delivered, the team will also learn why and when they should create a branch of the codeline. Acceptance criteria Testing in Visual Studio 2010 Microsoft Test Manager Writing and running manual tests Branching SPRINT 4 Retrospective Module 11: OVERCOMING DYSFUNCTION This module introduces the many types of people, process, and tool dysfunctions that teams face in the real world. Many dysfunctions and scenarios will be identified, along with ideas and discussion for how a team might mitigate them. This module will enable you and your team to move toward independence and improve your game of Scrum when you depart class. Scrum-butts and flaccid Scrum Best practices working as a team Team challenges ScrumMaster challenges Product Owner challenges Stakeholder challenges Course Retrospective What will be expected of you and you team? This is a unique course in that it’s technically-focused, team-based, and employs timeboxes. It demands that the members of the teams self-organize and self-manage their own work to collaboratively develop increments of software. All attendees must commit to: Pay attention to all lectures and demonstrations Participate in team and group discussions Work collaboratively with other team members Obey the timebox for each activity Commit to work and do your best to deliver All teams should have these skills: Understanding of Scrum Familiarity with Visual Studio 201 C#, .NET 4.0 & ASP.NET 4.0 experience*  SQL Server 2008 development experience Software testing experience * Check with the instructor ahead of time for the exact technologies Self-organising teams Another unique attribute of this course is that it’s a technical training class being delivered to teams of developers, not pairs, and not individuals. Ideally, your actual software development team will attend the training to ensure that all necessary skills are covered. However, if you wish to attend an open enrolment course alone or with just a couple of colleagues, realize that you may be placed on a team with other attendees. The instructor will do his or her best to ensure that each team is cross-functional to tackle the case study, but there are no guarantees. You may be required to try a new role, learn a new skill, or pair with somebody unfamiliar to you. This is just good Scrum! Who should NOT take this course? Because of the nature of this course, as explained above, certain types of people should probably not attend this course: Students requiring command and control style instruction – there are no prescriptive/step-by-step (think traditional Microsoft Learning) labs in this course Students who are unwilling to work within a timebox Students who are unwilling to work collaboratively on a team Students who don’t have any skill in any of the software development disciplines Students who are unable to commit fully to their team – not only will this diminish the student’s learning experience, but it will also impact their team’s learning experience Find a course and register Download this syllabus Download the Scrum Guide Technorati Tags: Scrum,SSW,Pro Scrum Dev

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  • How to solve package issues/dependencies

    - by Wolfgang Kuehne
    Background info I am trying to install Veins simulation environment by following the tutorial provided by the author. In step 1 it is required to install some packages in Linux, the tutorial suggest this commands to be executed on Terminal: sudo apt-get install build-essential gcc g++ bison flex perl tcl-dev tk-dev blt libxml2-dev zlib1g-dev default-jre doxygen graphviz libwebkitgtk-1.0-0 openmpi-bin libopenmpi-dev libpcap-dev autoconf automake libtool libxerces-c2-dev proj libgdal1-dev libfox-1.6-dev When I execute this command, I immediately get: E: Package 'proj' has no installation candidate Then I remove the proj from the command and execute it again without proj in it, next I get: The following packages have unmet dependencies: libgdal1-dev : Depends: libgdal-dev but it is not going to be installed E: Unable to correct problems, you have held broken packages. So, I remove libgdal1-dev from the command as well. And it executes file, by downloading the remaining packages. To troubleshoot the problem with proj and libdgal1-dev I go to the Synaptic Package Manager. libgdal1-dev I search for libgdal1-dev in Synaptic Package Manager and I get an entry. I Mark for Installation and then Synaptic Package Manager suggests removing libxerces-c2-dev which is actually added via the initial command. Should I trust Synaptic Package Manager with this suggestion, and proceed further? proj What should I do about proj. There are some packages in Synaptic Package Manager such as proj-bin or libproj-dev. Should I install them? I think proj has to do with this and this What should I do to make sure that this simulation tool works fine?

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  • Ignore Partial Upgrade -- Google Earth Dependencies

    - by pyraz
    I'm running a 64-bit install of Xubuntu 12.04. It took me a little while to get Google Earth working. The 64-bit Google earth package requires some 32-bit gtk libraries provided by ia32-libs. However, when I ran a simulation to install ia32-libs and it's dependencies, it wanted to remove a ton of programs, including the xubuntu-desktop meta-package. As a work-around, I used getlibs to get the 32-bit libraries I needed, and then installed Google Earth with the deb package and the --ignore-depend option to dpkg. Awesome, Google Earth is installed and is working great! Now, however, Update Manager keeps complaining about a "Partial Upgrade", and apt-get won't let me install any new applications. It wants me to do a fix-broken install, but when I do a simulation of apt-get -f install I get some very bad news, they want to uninstall the Google Earth I just worked so hard to install! $> apt-get -f -s install Reading package lists... Done Building dependency tree Reading state information... Done Correcting dependencies... Done The following packages will be REMOVED: googleearth 0 upgraded, 0 newly installed, 1 to remove and 0 not upgraded. Remv googleearth [6.0.3.2197+0.7.0-1] TL;DR The --ignore-depends passed to dpkg is not propagating to apt-get, so now I can't install any new applications until I uninstall Google Earth, because of it's missing dependencies (even though it works fine without them). How can I fix this?

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  • How do I choose the scaling factor of a 3D game world?

    - by concept3d
    I am making a 3D tank game prototype with some physics simulation, am using C++. One of the decisions I need to make is the scale of the game world in relation to reality. For example, I could consider 1 in-game unit of measurement to correspond to 1 meter in reality. This feels intuitive, but I feel like I might be missing something. I can think of the following as potential problems: 3D modelling program compatibility. (?) Numerical accuracy. (Does this matter?) Especially at large scales, how games like Battlefield have huge maps: How don't they lose numerical accuracy if they use 1:1 mapping with real world scale, since floating point representation tend to lose more precision with larger numbers (e.g. with ray casting, physics simulation)? Gameplay. I don't want the movement of units to feel slow or fast while using almost real world values like -9.8 m/s^2 for gravity. (This might be subjective.) Is it ok to scale up/down imported assets or it's best fit with a world with its original scale? Rendering performance. Are large meshes with the same vertex count slower to render? I'm wondering if I should split this into multiple questions...

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  • Failed to spawn test

    - by Lost
    Running a simple test in Ubuntu 12.04: sudo lxc-execute -n test /bin/bash -l debug -o outout Got error message: lxc-execute: failed to spawn 'test' cat outout: lxc-execute 1347053658.113 DEBUG lxc_start - sigchild handler set lxc-execute 1347053658.113 INFO lxc_start - 'test' is initialized lxc-execute 1347053658.366 DEBUG lxc_start - Dropping cap_sys_boot and watching utmp lxc-execute 1347053658.366 DEBUG lxc_cgroup - checking '/' (rootfs) lxc-execute 1347053658.366 DEBUG lxc_cgroup - checking '/sys' (sysfs) lxc-execute 1347053658.366 DEBUG lxc_cgroup - checking '/proc' (proc) lxc-execute 1347053658.366 DEBUG lxc_cgroup - checking '/dev' (devtmpfs) lxc-execute 1347053658.366 DEBUG lxc_cgroup - checking '/dev/pts' (devpts) lxc-execute 1347053658.367 DEBUG lxc_cgroup - checking '/run' (tmpfs) lxc-execute 1347053658.367 DEBUG lxc_cgroup - checking '/' (ext3) lxc-execute 1347053658.367 DEBUG lxc_cgroup - checking '/sys/fs/fuse/connections' (fusectl) lxc-execute 1347053658.367 DEBUG lxc_cgroup - checking '/sys/kernel/debug' (debugfs) lxc-execute 1347053658.367 DEBUG lxc_cgroup - checking '/sys/kernel/security' (securityfs) lxc-execute 1347053658.367 DEBUG lxc_cgroup - checking '/run/lock' (tmpfs) lxc-execute 1347053658.367 DEBUG lxc_cgroup - checking '/run/shm' (tmpfs) lxc-execute 1347053658.367 DEBUG lxc_cgroup - checking '/run/rpc_pipefs' (rpc_pipefs) lxc-execute 1347053658.367 DEBUG lxc_cgroup - checking '/scratch/WAMC-Simulation' (nfs) lxc-execute 1347053658.367 DEBUG lxc_cgroup - checking '/share' (nfs) lxc-execute 1347053658.367 DEBUG lxc_cgroup - checking '/proj/WAMC-Simulation' (nfs) lxc-execute 1347053658.367 DEBUG lxc_cgroup - checking '/users/bhu' (nfs) lxc-execute 1347053658.367 ERROR lxc_start - failed to spawn 'test' Run command: sudo lxc-checkconfig Kernel config /proc/config.gz not found, looking in other places... Found kernel config file /boot/config-2.6.38.7-1.0emulab --- Namespaces --- Namespaces: enabled Utsname namespace: enabled Ipc namespace: enabled Pid namespace: enabled User namespace: enabled Network namespace: enabled Multiple /dev/pts instances: enabled --- Control groups --- Cgroup: enabled Cgroup namespace: enabled Cgroup device: enabled Cgroup sched: enabled Cgroup cpu account: enabled Cgroup memory controller: enabled Cgroup cpuset: enabled --- Misc --- Veth pair device: enabled Macvlan: enabled Vlan: enabled File capabilities: enabled Note : Before booting a new kernel, you can check its configuration usage : CONFIG=/path/to/config /usr/bin/lxc-checkconfig What's the problem? Thanks a lot

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  • Audio and video streaming using Network Simulator in Linux

    - by Parth_90
    I am working on a project which is to show the simulation of streaming of audio and video data in wireless networks. I want to show the simulation that involves a base station, with few wireless stations. The base station should start sending data once it computes a certain value . On receiving the data, each wireless must begin communicating with the base station. I have gone through basic NS-2 tutorials from over here but I am not getting how to go about integrating it with my project. Can anyone tell me how to do it using NS2 or any other network simulator?

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  • Day in the Life of Agile - The Forge Michigan November 27, 2012

    - by csmith18119
    Went to training at The Forge yesterday and did a Day in the life of Agile with Pillar.  It was pretty good. Check them out at: http://pillartechnology.com/ Abstract: A single-day agile project simulation that is engaging, educational, provocative, and fun. This simulation introduces concepts like time-boxed iterations, User Stories, collective estimation, commitment to a product owner for iteration scope, formal verification ritual at iteration conclusion, tracking velocity, and making results big and visible through charts. The exercise is designed to simulate not only how agile teams and practices work, but the inevitable challenges that arise as teams attempt to adopt such practices. One of the best parts of this training was getting some hands on experience with agile.  We used a program called Scratch to create an arcade video game.  Our team chose Frogger.  We had 3 iterations at 20 minutes each.  I think we did pretty good but in the panic of trying to get a bunch done in only 20 minutes made it interesting. To check out our project, I uploaded it to my CodePlex site Download Source Code (Under Scratch/Frogger) Cool class! I highly recommend if you get the opportunity.

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  • how to communicate in typical router switch router scenario?

    - by Kossel
    I'm learning routing using packet tracer simulation and I think this is a very commun scenario: let's say pc4 is the server... why I can't ping from PC1 to 192.168.2.253 (router1) but I can ping 192.168.2.2 (pc0) aren't they the same subnet? what am I missing or have to do in order to reach pc4? (192.168.100.254) from pc 1 (192.168.1.1) is there something like "default gateway" for router? thanks for advice PS: during the simulation it shows error "The routing table does not have a route to the destination IP address. The router drops the packe (from 192.168.2.253 to 192.168.1.1)"

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  • Is it possible to boot already installed version of Ubuntu from within Win7, e.g. with a vm?

    - by Fizzik
    I have both Ubuntu 12.10 and Win7 installed. I use the former mostly for scientific simulations and the latter for applications. The problem I came across with this configuration is that the simulations take quite a while, and I'm not satisfied enough with solutions like Wine to run the Windows apps while the simulation runs. I would rather not install the simulation programs again, since it took quite an effort. So, is it possible to boot the already installed version of Ubuntu from within Windows 7 via VirtualBox or or something else?

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  • RK4 Bouncing a Ball

    - by Jonathan Dickinson
    I am trying to wrap my head around RK4. I decided to do the most basic 'ball with gravity that bounces' simulation. I have implemented the following integrator given Glenn Fiedler's tutorial: /// <summary> /// Represents physics state. /// </summary> public struct State { // Also used internally as derivative. // S: Position // D: Velocity. /// <summary> /// Gets or sets the Position. /// </summary> public Vector2 X; // S: Position // D: Acceleration. /// <summary> /// Gets or sets the Velocity. /// </summary> public Vector2 V; } /// <summary> /// Calculates the force given the specified state. /// </summary> /// <param name="state">The state.</param> /// <param name="t">The time.</param> /// <param name="acceleration">The value that should be updated with the acceleration.</param> public delegate void EulerIntegrator(ref State state, float t, ref Vector2 acceleration); /// <summary> /// Represents the RK4 Integrator. /// </summary> public static class RK4 { private const float OneSixth = 1.0f / 6.0f; private static void Evaluate(EulerIntegrator integrator, ref State initial, float t, float dt, ref State derivative, ref State output) { var state = new State(); // These are a premature optimization. I like premature optimization. // So let's not concentrate on that. state.X.X = initial.X.X + derivative.X.X * dt; state.X.Y = initial.X.Y + derivative.X.Y * dt; state.V.X = initial.V.X + derivative.V.X * dt; state.V.Y = initial.V.Y + derivative.V.Y * dt; output = new State(); output.X.X = state.V.X; output.X.Y = state.V.Y; integrator(ref state, t + dt, ref output.V); } /// <summary> /// Performs RK4 integration over the specified state. /// </summary> /// <param name="eulerIntegrator">The euler integrator.</param> /// <param name="state">The state.</param> /// <param name="t">The t.</param> /// <param name="dt">The dt.</param> public static void Integrate(EulerIntegrator eulerIntegrator, ref State state, float t, float dt) { var a = new State(); var b = new State(); var c = new State(); var d = new State(); Evaluate(eulerIntegrator, ref state, t, 0.0f, ref a, ref a); Evaluate(eulerIntegrator, ref state, t + dt * 0.5f, dt * 0.5f, ref a, ref b); Evaluate(eulerIntegrator, ref state, t + dt * 0.5f, dt * 0.5f, ref b, ref c); Evaluate(eulerIntegrator, ref state, t + dt, dt, ref c, ref d); a.X.X = OneSixth * (a.X.X + 2.0f * (b.X.X + c.X.X) + d.X.X); a.X.Y = OneSixth * (a.X.Y + 2.0f * (b.X.Y + c.X.Y) + d.X.Y); a.V.X = OneSixth * (a.V.X + 2.0f * (b.V.X + c.V.X) + d.V.X); a.V.Y = OneSixth * (a.V.Y + 2.0f * (b.V.Y + c.V.Y) + d.V.Y); state.X.X = state.X.X + a.X.X * dt; state.X.Y = state.X.Y + a.X.Y * dt; state.V.X = state.V.X + a.V.X * dt; state.V.Y = state.V.Y + a.V.Y * dt; } } After reading over the tutorial I noticed a few things that just seemed 'out' to me. Notably how the entire simulation revolves around t at 0 and state at 0 - considering that we are working out a curve over the duration it seems logical that RK4 wouldn't be able to handle this simple scenario. Never-the-less I forged on and wrote a very simple Euler integrator: static void Integrator(ref State state, float t, ref Vector2 acceleration) { if (state.X.Y > 100 && state.V.Y > 0) { // Bounce vertically. acceleration.Y = -state.V.Y * t; } else { acceleration.Y = 9.8f; } } I then ran the code against a simple fixed-time step loop and this is what I got: 0.05 0.20 0.44 0.78 1.23 1.76 ... 74.53 78.40 82.37 86.44 90.60 94.86 99.23 103.05 105.45 106.94 107.86 108.42 108.76 108.96 109.08 109.15 109.19 109.21 109.23 109.23 109.24 109.24 109.24 109.24 109.24 109.24 109.24 109.24 109.24 109.24 109.24 109.24 109.24 109.24 ... As I said, I was expecting it to break - however I am unsure of how to fix it. I am currently looking into keeping the previous state and time, and working from that - although at the same time I assume that will defeat the purpose of RK4. How would I get this simulation to print the expected results?

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  • Dragging a Sprite (Cocos2D) while Chipmunk is simulating

    - by itai alter
    Hello all! I have a simple project built with Cocos2D and Chipmunk. So far it's just a Ball (body, shape & sprite) bouncing on the Ground (a static line segment at the bottom of the screen). I implemented the ccTouchesBegan/Moved/Ended methods to drag the ball around. I've tried both: cpBodySlew(ballBody, touchPoint, 1.0/60.0f); and ballBody->p = cgPointMake(touchPoint.x,touchPoint.y); and while the Ball does follow my dragging, it's still being affected by gravity and it tries to go down (which causes velocity problems and others). Does anyone know of the preferred way to Drag an active Body while the physics simulation is going on? Do I need somehow to stop the simulation and turn it back on afterwards? Thanks!

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  • Boost.Program_Options not working with short options

    - by inajamaica
    I have the following options_description: po::options_description config("Configuration File or Command Line"); config.add_options() ("run-time,t", po::value(&runTime_)-default_value(1440.0), "set max simulation duration") ("starting-iteration,i", po::value(&startingIteration_)-default_value(1), "set starting simulation iteration") ("repetitions,r", po::value(&repetitions_)-default_value(100), "set number of iterations") ... ; As you can see the three shown have a long,short names employed. The long versions all work. However, none of the short ones do, and each time I try a -t 12345.0 or a -i 12345, etc., I get the following from Program_Options: std::logic_error: in option 'starting-iteration': invalid option value I'm using Boost 1.42 on Win32. Any thoughts on what might be going on here? Thanks!

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  • C++ - Conway's Game of Life & Stepping Backwards

    - by Gabe
    I was able to create a version Conway's Game of Life that either stepped forward each click, or just ran forward using a timer. (I'm doing this using Qt.) Now, I need to be able to save all previous game grids, so that I can step backwards by clicking a button. I'm trying to use a stack, and it seems like I'm pushing the old gridcells onto the stack correctly. But when I run it in QT, the grids don't change when I click BACK. I've tried different things for the last three hours, to no avail. Any ideas? gridwindow.cpp - My problem should be in here somewhere. Probably the handleBack() func. #include <iostream> #include "gridwindow.h" using namespace std; // Constructor for window. It constructs the three portions of the GUI and lays them out vertically. GridWindow::GridWindow(QWidget *parent,int rows,int cols) : QWidget(parent) { QHBoxLayout *header = setupHeader(); // Setup the title at the top. QGridLayout *grid = setupGrid(rows,cols); // Setup the grid of colored cells in the middle. QHBoxLayout *buttonRow = setupButtonRow(); // Setup the row of buttons across the bottom. QVBoxLayout *layout = new QVBoxLayout(); // Puts everything together. layout->addLayout(header); layout->addLayout(grid); layout->addLayout(buttonRow); setLayout(layout); } // Destructor. GridWindow::~GridWindow() { delete title; } // Builds header section of the GUI. QHBoxLayout* GridWindow::setupHeader() { QHBoxLayout *header = new QHBoxLayout(); // Creates horizontal box. header->setAlignment(Qt::AlignHCenter); this->title = new QLabel("CONWAY'S GAME OF LIFE",this); // Creates big, bold, centered label (title): "Conway's Game of Life." this->title->setAlignment(Qt::AlignHCenter); this->title->setFont(QFont("Arial", 32, QFont::Bold)); header->addWidget(this->title); // Adds widget to layout. return header; // Returns header to grid window. } // Builds the grid of cells. This method populates the grid's 2D array of GridCells with MxN cells. QGridLayout* GridWindow::setupGrid(int rows,int cols) { isRunning = false; QGridLayout *grid = new QGridLayout(); // Creates grid layout. grid->setHorizontalSpacing(0); // No empty spaces. Cells should be contiguous. grid->setVerticalSpacing(0); grid->setSpacing(0); grid->setAlignment(Qt::AlignHCenter); for(int i=0; i < rows; i++) //Each row is a vector of grid cells. { std::vector<GridCell*> row; // Creates new vector for current row. cells.push_back(row); for(int j=0; j < cols; j++) { GridCell *cell = new GridCell(); // Creates and adds new cell to row. cells.at(i).push_back(cell); grid->addWidget(cell,i,j); // Adds to cell to grid layout. Column expands vertically. grid->setColumnStretch(j,1); } grid->setRowStretch(i,1); // Sets row expansion horizontally. } return grid; // Returns grid. } // Builds footer section of the GUI. QHBoxLayout* GridWindow::setupButtonRow() { QHBoxLayout *buttonRow = new QHBoxLayout(); // Creates horizontal box for buttons. buttonRow->setAlignment(Qt::AlignHCenter); // Clear Button - Clears cell; sets them all to DEAD/white. QPushButton *clearButton = new QPushButton("CLEAR"); clearButton->setFixedSize(100,25); connect(clearButton, SIGNAL(clicked()), this, SLOT(handlePause())); // Pauses timer before clearing. connect(clearButton, SIGNAL(clicked()), this, SLOT(handleClear())); // Connects to clear function to make all cells DEAD/white. buttonRow->addWidget(clearButton); // Forward Button - Steps one step forward. QPushButton *forwardButton = new QPushButton("FORWARD"); forwardButton->setFixedSize(100,25); connect(forwardButton, SIGNAL(clicked()), this, SLOT(handleForward())); // Signals to handleForward function.. buttonRow->addWidget(forwardButton); // Back Button - Steps one step backward. QPushButton *backButton = new QPushButton("BACK"); backButton->setFixedSize(100,25); connect(backButton, SIGNAL(clicked()), this, SLOT(handleBack())); // Signals to handleBack funciton. buttonRow->addWidget(backButton); // Start Button - Starts game when user clicks. Or, resumes game after being paused. QPushButton *startButton = new QPushButton("START/RESUME"); startButton->setFixedSize(100,25); connect(startButton, SIGNAL(clicked()), this, SLOT(handlePause())); // Deletes current timer if there is one. Then restarts everything. connect(startButton, SIGNAL(clicked()), this, SLOT(handleStart())); // Signals to handleStart function. buttonRow->addWidget(startButton); // Pause Button - Pauses simulation of game. QPushButton *pauseButton = new QPushButton("PAUSE"); pauseButton->setFixedSize(100,25); connect(pauseButton, SIGNAL(clicked()), this, SLOT(handlePause())); // Signals to pause function which pauses timer. buttonRow->addWidget(pauseButton); // Quit Button - Exits program. QPushButton *quitButton = new QPushButton("EXIT"); quitButton->setFixedSize(100,25); connect(quitButton, SIGNAL(clicked()), qApp, SLOT(quit())); // Signals the quit slot which ends the program. buttonRow->addWidget(quitButton); return buttonRow; // Returns bottom of layout. } /* SLOT method for handling clicks on the "clear" button. Receives "clicked" signals on the "Clear" button and sets all cells to DEAD. */ void GridWindow::handleClear() { for(unsigned int row=0; row < cells.size(); row++) // Loops through current rows' cells. { for(unsigned int col=0; col < cells[row].size(); col++) // Loops through the rows'columns' cells. { GridCell *cell = cells[row][col]; // Grab the current cell & set its value to dead. cell->setType(DEAD); } } } /* SLOT method for handling clicks on the "start" button. Receives "clicked" signals on the "start" button and begins game simulation. */ void GridWindow::handleStart() { isRunning = true; // It is running. Sets isRunning to true. this->timer = new QTimer(this); // Creates new timer. connect(this->timer, SIGNAL(timeout()), this, SLOT(timerFired())); // Connect "timerFired" method class to the "timeout" signal fired by the timer. this->timer->start(500); // Timer to fire every 500 milliseconds. } /* SLOT method for handling clicks on the "pause" button. Receives "clicked" signals on the "pause" button and stops the game simulation. */ void GridWindow::handlePause() { if(isRunning) // If it is running... this->timer->stop(); // Stops the timer. isRunning = false; // Set to false. } void GridWindow::handleForward() { if(isRunning); // If it's running, do nothing. else timerFired(); // It not running, step forward one step. } void GridWindow::handleBack() { std::vector<std::vector<GridCell*> > cells2; if(isRunning); // If it's running, do nothing. else if(backStack.empty()) cout << "EMPTYYY" << endl; else { cells2 = backStack.peek(); for (unsigned int f = 0; f < cells.size(); f++) // Loop through cells' rows. { for (unsigned int g = 0; g < cells.at(f).size(); g++) // Loop through cells columns. { cells[f][g]->setType(cells2[f][g]->getType()); // Set cells[f][g]'s type to cells2[f][g]'s type. } } cout << "PRE=POP" << endl; backStack.pop(); cout << "OYYYY" << endl; } } // Accessor method - Gets the 2D vector of grid cells. std::vector<std::vector<GridCell*> >& GridWindow::getCells() { return this->cells; } /* TimerFired function: 1) 2D-Vector cells2 is declared. 2) cells2 is initliazed with loops/push_backs so that all its cells are DEAD. 3) We loop through cells, and count the number of LIVE neighbors next to a given cell. --> Depending on how many cells are living, we choose if the cell should be LIVE or DEAD in the next simulation, according to the rules. -----> We save the cell type in cell2 at the same indice (the same row and column cell in cells2). 4) After check all the cells (and save the next round values in cells 2), we set cells's gridcells equal to cells2 gridcells. --> This causes the cells to be redrawn with cells2 types (white or black). */ void GridWindow::timerFired() { backStack.push(cells); std::vector<std::vector<GridCell*> > cells2; // Holds new values for 2D vector. These are the next simulation round of cell types. for(unsigned int i = 0; i < cells.size(); i++) // Loop through the rows of cells2. (Same size as cells' rows.) { vector<GridCell*> row; // Creates Gridcell* vector to push_back into cells2. cells2.push_back(row); // Pushes back row vectors into cells2. for(unsigned int j = 0; j < cells[i].size(); j++) // Loop through the columns (the cells in each row). { GridCell *cell = new GridCell(); // Creates new GridCell. cell->setType(DEAD); // Sets cell type to DEAD/white. cells2.at(i).push_back(cell); // Pushes back the DEAD cell into cells2. } // This makes a gridwindow the same size as cells with all DEAD cells. } for (unsigned int m = 0; m < cells.size(); m++) // Loop through cells' rows. { for (unsigned int n = 0; n < cells.at(m).size(); n++) // Loop through cells' columns. { unsigned int neighbors = 0; // Counter for number of LIVE neighbors for a given cell. // We know check all different variations of cells[i][j] to count the number of living neighbors for each cell. // We check m > 0 and/or n > 0 to make sure we don't access negative indexes (ex: cells[-1][0].) // We check m < size to make sure we don't try to access rows out of the vector (ex: row 5, if only 4 rows). // We check n < row size to make sure we don't access column item out of the vector (ex: 10th item in a column of only 9 items). // If we find that the Type = 1 (it is LIVE), then we add 1 to the neighbor. // Else - we add nothing to the neighbor counter. // Neighbor is the number of LIVE cells next to the current cell. if(m > 0 && n > 0) { if (cells[m-1][n-1]->getType() == 1) neighbors += 1; } if(m > 0) { if (cells[m-1][n]->getType() == 1) neighbors += 1; if(n < (cells.at(m).size() - 1)) { if (cells[m-1][n+1]->getType() == 1) neighbors += 1; } } if(n > 0) { if (cells[m][n-1]->getType() == 1) neighbors += 1; if(m < (cells.size() - 1)) { if (cells[m+1][n-1]->getType() == 1) neighbors += 1; } } if(n < (cells.at(m).size() - 1)) { if (cells[m][n+1]->getType() == 1) neighbors += 1; } if(m < (cells.size() - 1)) { if (cells[m+1][n]->getType() == 1) neighbors += 1; } if(m < (cells.size() - 1) && n < (cells.at(m).size() - 1)) { if (cells[m+1][n+1]->getType() == 1) neighbors += 1; } // Done checking number of neighbors for cells[m][n] // Now we change cells2 if it should switch in the next simulation step. // cells2 holds the values of what cells should be on the next iteration of the game. // We can't change cells right now, or it would through off our other cell values. // Apply game rules to cells: Create new, updated grid with the roundtwo vector. // Note - LIVE is 1; DEAD is 0. if (cells[m][n]->getType() == 1 && neighbors < 2) // If cell is LIVE and has less than 2 LIVE neighbors -> Set to DEAD. cells2[m][n]->setType(DEAD); else if (cells[m][n]->getType() == 1 && neighbors > 3) // If cell is LIVE and has more than 3 LIVE neighbors -> Set to DEAD. cells2[m][n]->setType(DEAD); else if (cells[m][n]->getType() == 1 && (neighbors == 2 || neighbors == 3)) // If cell is LIVE and has 2 or 3 LIVE neighbors -> Set to LIVE. cells2[m][n]->setType(LIVE); else if (cells[m][n]->getType() == 0 && neighbors == 3) // If cell is DEAD and has 3 LIVE neighbors -> Set to LIVE. cells2[m][n]->setType(LIVE); } } // Now we've gone through all of cells, and saved the new values in cells2. // Now we loop through cells and set all the cells' types to those of cells2. for (unsigned int f = 0; f < cells.size(); f++) // Loop through cells' rows. { for (unsigned int g = 0; g < cells.at(f).size(); g++) // Loop through cells columns. { cells[f][g]->setType(cells2[f][g]->getType()); // Set cells[f][g]'s type to cells2[f][g]'s type. } } } stack.h - Here's my stack. #ifndef STACK_H_ #define STACK_H_ #include <iostream> #include "node.h" template <typename T> class Stack { private: Node<T>* top; int listSize; public: Stack(); int size() const; bool empty() const; void push(const T& value); void pop(); T& peek() const; }; template <typename T> Stack<T>::Stack() : top(NULL) { listSize = 0; } template <typename T> int Stack<T>::size() const { return listSize; } template <typename T> bool Stack<T>::empty() const { if(listSize == 0) return true; else return false; } template <typename T> void Stack<T>::push(const T& value) { Node<T>* newOne = new Node<T>(value); newOne->next = top; top = newOne; listSize++; } template <typename T> void Stack<T>::pop() { Node<T>* oldT = top; top = top->next; delete oldT; listSize--; } template <typename T> T& Stack<T>::peek() const { return top->data; // Returns data in top item. } #endif gridcell.cpp - Gridcell implementation #include <iostream> #include "gridcell.h" using namespace std; // Constructor: Creates a grid cell. GridCell::GridCell(QWidget *parent) : QFrame(parent) { this->type = DEAD; // Default: Cell is DEAD (white). setFrameStyle(QFrame::Box); // Set the frame style. This is what gives each box its black border. this->button = new QPushButton(this); //Creates button that fills entirety of each grid cell. this->button->setSizePolicy(QSizePolicy::Expanding,QSizePolicy::Expanding); // Expands button to fill space. this->button->setMinimumSize(19,19); //width,height // Min height and width of button. QHBoxLayout *layout = new QHBoxLayout(); //Creates a simple layout to hold our button and add the button to it. layout->addWidget(this->button); setLayout(layout); layout->setStretchFactor(this->button,1); // Lets the buttons expand all the way to the edges of the current frame with no space leftover layout->setContentsMargins(0,0,0,0); layout->setSpacing(0); connect(this->button,SIGNAL(clicked()),this,SLOT(handleClick())); // Connects clicked signal with handleClick slot. redrawCell(); // Calls function to redraw (set new type for) the cell. } // Basic destructor. GridCell::~GridCell() { delete this->button; } // Accessor for the cell type. CellType GridCell::getType() const { return(this->type); } // Mutator for the cell type. Also has the side effect of causing the cell to be redrawn on the GUI. void GridCell::setType(CellType type) { this->type = type; redrawCell(); // Sets type and redraws cell. } // Handler slot for button clicks. This method is called whenever the user clicks on this cell in the grid. void GridCell::handleClick() { // When clicked on... if(this->type == DEAD) // If type is DEAD (white), change to LIVE (black). type = LIVE; else type = DEAD; // If type is LIVE (black), change to DEAD (white). setType(type); // Sets new type (color). setType Calls redrawCell() to recolor. } // Method to check cell type and return the color of that type. Qt::GlobalColor GridCell::getColorForCellType() { switch(this->type) { default: case DEAD: return Qt::white; case LIVE: return Qt::black; } } // Helper method. Forces current cell to be redrawn on the GUI. Called whenever the setType method is invoked. void GridCell::redrawCell() { Qt::GlobalColor gc = getColorForCellType(); //Find out what color this cell should be. this->button->setPalette(QPalette(gc,gc)); //Force the button in the cell to be the proper color. this->button->setAutoFillBackground(true); this->button->setFlat(true); //Force QT to NOT draw the borders on the button } Thanks a lot. Let me know if you need anything else.

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  • QTest::keyPress is not returning nativeScanCode

    - by vels
    Hi, I am simulating F1 key using QTest::keyPress() method to test keypress event, on simulation of F1 key when i check for nativeScanCode, it returns 0 value. can any one help? //Code snippet //To simulate F1 key press QTest::keyPress(&kboard, Qt::Key_F1); //To check keypress Event void keyboard::keyPressEvent(QKeyEvent* ke) { if ( ke->type() == QEvent::KeyPress ) { QKeyEvent* key_event = static_cast<QKeyEvent *>(ke); //To check F1 key simulation if (key_event->key() == Qt::Key_F1) { int nativeCode = key_event->nativeScanCode(); qDebug()<< nativeCode <<endl; } } } Thanks, vels

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  • How to best integrate generated code

    - by Arne
    I am evaluating the use of code generation for my flight simulation project. More specifically there is a requirement to allow "the average engineer" (no offense I am one myself) to define the differential equations that describe the dynamic system in a more natural syntax than C++ provides. The idea is to devise a abstract descriptor language that can be easily understood and edited to generate C++ code from. This descriptor is supplied by the modeling engineer and used by the ones implementing and maintaining the simulation evironment to generate code. I've got something like this in mind: model Aircraft has state x1, x2; state x3; input double : u; input bool : flag1, flag2; algebraic double : x1x2; model Engine : tw1, tw2; model Gear : gear; model ISA : isa; trim routine HorizontalFight; trim routine OnGround, General; constant double : c1, c2; constant int : ci1; begin differential equations x1' = x1 + 2.*x2; x2' = x2 + x1x2; begin algebraic equations x1x2 = x1*x2 + x1'; end model It is important to retain the flexibility of the C language thus the descriptor language is meant to only define certain parts of the definition and implementation of the model class. This way one enigneer provides the model in from of the descriptor language as examplified above and the maintenance enigneer will add all the code to read parameters from files, start/stop/pause the execution of the simulation and how a concrete object gets instatiated. My first though is to either generate two files from the descriptor file: one .h file containing declarations and one .cpp file containing the implementation of certain functions. These then need to be #included at appropriate places [File Aircarft.h] class Aircraft { public: void Aircraft(..); // hand-written constructor void ReadParameters(string &file_name); // hand-written private: /* more hand wirtten boiler-plate code */ /* generate declarations follow */ #include "Aircraft.generated.decl" }; [File Aircraft.cpp] Aircarft::Aircraft(..) { /* hand-written constructer implementation */ } /* more hand-written implementation code */ /* generated implementation code follows */ #include "Aircraft.generated.impl" Any thoughts or suggestions?

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  • Get status of servlet request before the response is returned

    - by Alex
    Good evening, I am in the process of writing a Java Servlet (Struts 2, Tomcat, JSP etc) which is capable of doing some fairly complex simulations. These can take up to 2 minutes to complete on the and will return a graph of the results. It is trivial to calculate the percentage of the simulation completed because the process works by repeating the same calculations 1000s of times. I would be interested to know if anyone has ever tried to use client side technology to provide any estimate of the percentage complete. I.e query the servlet processing to get the number of cycles completed at various point throughout the simulation. This could then be displayed as a bar in the client browser. Any thoughts, advice, resources would be much appreciated. Thanks, Alex

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  • MinGW linking problem

    - by Tobias Langner
    I have a linking problem with MinGW. These are the calls: g++ -enable-stdcall-fixup -Wl,-enable-auto-import -Wl,-enable-runtime-pseudo-reloc -mthreads -Wl -Wl,-subsystem,windows -o debug/Simulation.exe debug/LTNetSender.o debug/main.o debug/simulation.o debug/moc_simulation.o -L'c:/Programmieren/Qt/4.5.2/lib' -lmingw32 -lqtmaind -LC:\Programmieren\Qt\boost_1_39_0\distrib\lib -LC:\Programmieren\MinGW\lib -llibboost_system-mgw34-mt -llibws2_32 -lQtSqld4 -lQtGuid4 -lQtNetworkd4 -lQtCored4 C:\Programmieren\MinGW\bin\..\lib\gcc\mingw32\3.4.5\..\..\..\..\mingw32\bin\ ld.exe: cannot find -llibws2_32 The MinGW library directory is included in the library path and libws2_32.a is in this directory. Why isn't the linker finding the library?

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  • Concatenating databases with Squeryl

    - by Pengin
    I'm trying to use Squeryl to take the contents of a table from one database, and append it to the equivalent table in another database. The primary key will have to be reassigned in the process, but I'm getting the error NULL not allowed for column "SIMID". Why is this? object Concatenator { def main(args: Array[String]) { Class.forName("org.h2.Driver"); val seshA = Session.create( java.sql.DriverManager.getConnection("jdbc:h2:file:data/resultsA", "sa", "password"), new H2Adapter ) val seshB = Session.create( java.sql.DriverManager.getConnection("jdbc:h2:file:data/resultsB", "sa", "password"), new H2Adapter ) using(seshA){ import Library._ from(sims){s => select(s)}.foreach{item => using(seshB){ sims.insert(item); } } } } case class Simulation( @Column("SIMID") var id: Long, val date: Date ) extends KeyedEntity[Long] object Library extends Schema { val sims = table[Simulation] on(sims)(s => declare( s.id is(unique, indexed, autoIncremented) )) } }

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  • Increase efficiency for an R simulator of the Monty Hall Puzzle

    - by jahan_m
    The Monty Hall Problem is a simple puzzle involving probability that even stumps professionals in careers dealing with some heavy-duty math. Here's the basic problem: Suppose you're on a game show, and you're given the choice of three doors: Behind one door is a car; behind the others, goats. You pick a door, say No. 1, and the host, who knows what's behind the doors, opens another door, say No. 3, which has a goat. He then says to you, "Do you want to pick door No. 2?" Is it to your advantage to switch your choice? You can find numerous explanations of the solution here: http://en.wikipedia.org/wiki/Monty_Hall_problem Goal of my simulation: Prove that a switching strategy will win you the car 2/3 of the time. I got curious and wanted to write a little function that simulates the problem many times and returns the proportion of wins if you switched and the proportion of wins if you stayed with your first choice. The function then plots the cumulative wins. First and foremost, I'm interested in hearing if my simulation is indeed replicating the Monty Problem, or if some aspect of the code got it wrong. Secondly, this function takes a long time to run once I get to about 10,000 simulations. I know I don't need this many simulations to prove this but I'd love to hear some ideas on how to make it more efficient. Thanks for your feedback! Monty_Hall=function(repetitions){ doors=c('A','B','C') stay_wins=0 switch_wins=0 series=data.frame(sim_num=seq(repetitions),cum_sum_stay=replicate(repetitions,0),cum_sum_switch=replicate(repetitions,0)) for(i in seq(repetitions)){ winning_door=sample(doors,1) contestant_chooses=sample(doors,1) if(contestant_chooses==winning_door) stay_wins=stay_wins+1 else switch_wins=switch_wins+1 series[i,'cum_sum_stay']=stay_wins series[i,'cum_sum_switch']=switch_wins } plot(series$sim_num,series$cum_sum_switch,col=2,ylab='Cumulative # of wins', xlab='Simulation #',main=sprintf('%d Simulations of the Monty Hall Paradox',repetitions),type='l') lines(series$sim_num,series$cum_sum_stay,col=4) legend('topleft',legend=c('Cumulative wins from switching', 'Cumulative wins from staying'),col=c(2,4),lty=1) result=list(series=series,stay_wins=stay_wins,switch_wins=switch_wins, proportion_stay_wins=stay_wins/repetitions, proportion_switch_wins=switch_wins/repetitions) return(result) } #Theory predicts that it is to the contestant's advantage if he #switches his choice to the other door. This function simulates the game #many times, and shows you the proportion of games in which staying or #switching would win the car. It also plots the cumulative wins for each strategy. Monty_Hall(100)

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