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• Excel Solver vs Solver Foundation

  - by JoshReuben

  I recently read a book http://www.amazon.com/Scientific-Engineering-Cookbook-Cookbooks-OReilly/dp/0596008791/ref=sr_1_1?ie=UTF8&s=books&qid=1296593374&sr=8-1 - the Excel Scientific and Engineering Cookbook.     The 2 main tools that this book leveraged were the Data Analysis Pack and Excel Solver. I had previously been aquanted with Microsoft Solver Foundation - this is a full fledged API for solving optimization problems, and went beyond being a mere Excel plugin - it exposed a C# programmatic interface for in process and a web service interface for out of process integration. were they the same? apparently not!   2 different solver frameworks for Excel: http://www.solver.com/index.html http://www.solverfoundation.com/ I contacted both vendors to get their perspectives.   Heres what the Excel Solver guys had to say:   "The Solver Foundation requires you to learn and use a very specific modeling language (OML). The Excel solver allows you to formulate your optimization problems without learning any new language simply by entering the formulas into cells on the Excel spreadsheet, something that nearly everyone is already familiar with doing.   The Excel Solver also allows you to seamlessly upgrade to products that combine Monte Carlo Simulation capabilities (our Risk Solver Premium and Risk Solver Platform products) which allow you to include uncertainty into your models when appropriate.   Our advanced Excel Solver Products also have a number of built in reporting tools for advanced analysis of the your model and it's results"           And Heres what the Microsoft Solver Foundation guys had to say:   "  With the release of Solver Foundation 3.0, Solver Foundation has the same kinds of solvers (plus a few more) than what is found in Excel Solver. I think there are two main differences:   1.      Problems are described differently. In Excel Solver the goals and constraints are specified inside the spreadsheet, in formulas. In Solver Foundation they are described either in .Net code that uses the Solver Foundation Services API, or using the OML modeling language in Excel. 2.      Solver Foundation’s primary strength is on solving large linear, mixed integer, and constraint models. That is, models that contain arbitrary nonlinear functions (such as trig functions, IF(), powers, etc) are handled a bit better by the Excel Solver at this point. "

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• What Would a CyberWar Do To Your Business?

  - by [email protected]

  In mid-February the Bipartisan Policy Center in the United States hosted Cyber ShockWave, a simulation of how the country might respond to a catastrophic cyber event. An attack takes place, they can't isolate where it came from or who did it, simulated press reports and market impacts...and the participants in the exercise have to brief the President and advise him/her on what to do. Last week, Former Department of Homeland Security Secretary Michael Chertoff who participated in the exercise summarized his findings in Federal Computer Weekly. The article, given FCW's readership and the topic is obviously focused on the public sector and US Federal policies. However, it touches on some broader issues that impact the private sector as well--which are applicable to any government and country/region-- such as: · How would the US (or any) government collaborate to identify and defeat such an attack? Chertoff calls this out as a current gap. How do the public and private sector collaborate today? How would the massive and disparate collection of agencies and companies act together in a crunch? · What would the impact on industries and global economies be? Chertoff, and a companion article in Government Computer News, only touch briefly on the subject--focusing on the impact on capital markets. "There's no question this has a disastrous impact on the economy," said Stephen Friedman, former director of the National Economic Council under President George W. Bush who played the role of treasury secretary. "You have financial markets shut down at this point, ordinary transactions are dramatically depleted, there's no question that this has a major impact on consumer confidence." That Got Me Thinking · How would it impact Oracle's customers? I know they have business continuity plans--is this one of their scenarios? What if it's not? How would it impact manufacturing lines, ATM networks, customer call centers... · How would it impact me and the companies I rely on? The supermarket down the street, my Internet Service Provider, the service station where I bought gas last night. I sure don't have any answers, and neither do Chertoff or the participants in the exercise. "I have to tell you that ... we are operating in a bit of unchartered territory." said Jamie Gorelick, a former deputy attorney general who played the role of attorney general in the exercise. But it is a good thing that governments and businesses are considering this scenario and doing what they can to prevent it from happening.

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• ray collision with rectangle and floating point accuracy

  - by phq

  I'm trying to solve a problem with a ray bouncing on a box. Actually it is a sphere but for simplicity the box dimensions are expanded by the sphere radius when doing the collision test making the sphere a single ray. It is done by projecting the ray onto all faces of the box and pick the one that is closest. However because I'm using floating point variables I fear that the projected point onto the surface might be interpreted as being below in the next iteration, also I will later allow the sphere to move which might make that scenario more likely. Also the bounce coefficient might be as low as zero, making the sphere continue along the surface. So my naive solution is to project not only forwards but backwards to catch those cases. That is where I got into problems shown in the figure: In the first iteration the first black arrow is calculated and we end up at a point on the surface of the box. In the second iteration the "back projection" hits the other surface making the second black arrow bounce on the wrong surface. If there are several boxes close to each other this has further consequences making the sphere fall through them all. So my main question is how to handle possible floating point accuracy when placing the sphere on the box surface so it does not fall through. In writing this question I got the idea to have a threshold to only accept back projections a certain amount much smaller than the box but larger than the possible accuracy limitation, this would only cause the "false" back projection when the sphere hit the box on an edge which would appear naturally. To clarify my original approach, the arrows shown in the image is not only the path the sphere travels but is also representing a single time step in the simulation. In reality the time step is much smaller about 0.05 of the box size. The path traveled is projected onto possible sides to avoid traveling past a thinner object at higher speeds. In normal situations the floating point accuracy is not an issue but there are two situations where I have the concern. When the new position at the end of the time step is located very close to the surface, very unlikely though. When using a bounce factor of 0, here it happens every time the sphere hit a box. To add some loss of accuracy, the motivation for my concern, is that the sphere and box are in different coordinate systems and thus the sphere location is transformed for every test. This last one is why I'm not willing to stand on luck that one floating point value lying on top of the box always will be interpreted the same. I did not know voronoi regions by name, but looking at it I'm not sure how it would be used in a projection scenario that I'm using here.

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• box2d resize bodies arround point

  - by philipp

  I have a compound object, consisting of a b2Body, vector-graphics and a list polygons which describe the b2body's shapes. This object has its own transformation matrix to centralize the storage of transformations. So far everything is working quiet fine, even scaling works, but not if i scale around a point. In the initialization phase of the object it is scaled around a point. This happens in this order: transform the main matrix transform the vector graphics and the polygons recreate the b2Body After this function ran, the shapes and all the graphics are exactly where they should be, BUT: after the first steps of the b2World the graphical stuff moves away from the body. When I ran the debugger I found out that the position of the body is 0/0 the red dot shows the center of scaling. the first image shows the basic setup and the second the final position of the graphics. This distance stays constant for the rest of the simulation. If I set the position via myBody.SetPosition( sx, sy ); the whole scenario just plays a bit more distant for the origin. Any Idea how to fix this? EDIT:: I came deeper down to the problem and it lies in the fact that i must not scale the transform matrix for the b2body shapes around the center, but set the b2body's position back to the point after scaling. But how can I calculate that point? EDIT 2 :: I came ever deeper down to it, even solved it, but this is a slow solution and i hope that there is somebody who understands what formula I need. assuming to have a set polygons relative to an origin as basis shapes for a b2body: scaling the whole object around a certain point is done in the following steps: i scale everything around the center except the polygons i create a clone of the polygons matrix i scale this clone around the point i calculate dx, dy as difference of clone.tx - original.tx and clone.ty - original.ty i scale the original polygon matrix NOT around the point i recreate the body i create the fixture i set the position of the body to dx and dy done! So what i an interested in is a formula for dx and dy without cloning matrices, scaling the clone around a point, getting dx and dy and finally scale the vertex matrix.

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• A starting point for Use Cases and User Stories

  - by Mike Benkovich

  Originally posted on: http://geekswithblogs.net/benko/archive/2013/07/23/a-starting-point-for-use-cases-and-user-stories.aspxSoftware is a challenging business and is rife with opportunities to go wrong. Over the years a number of methodologies have evolved to help make sure that things go right. In an effort to contribute to this I’ve created a list of user stories that I think should be included and sometimes are just assumed. Note this is a work in progress, so I’m looking for your feedback. I’m curious what you would add or change in my list. · As a DBA I am working with a Normalized data model that reflects an agreed upon logical model for the system · As a DBA I am using consistent names for my fields which match the naming standards of my organization · As a DBA my model supports simple CRUD operations against all the entities · As an Application Architect the UI has been validated against the Business requirements and a complete set of user story’s have been created · As an Application Architect the database model has been validated against the UI · As an Application Architect we have a logical business model that describes all the known and/or expected usage of the system during the software’s expected lifecycle · As an Application Architect we have a Deployment diagram that describes how the application components will be deployed · As an Application Architect we have a navigation diagram that describes the typical application flow · As an Application Architect we have identified points of interaction which describes how the UI interacts with the services and the data storage · As an Application Architect we have identified external systems which may now or in the future use the data of this application and have adapted the logical model to include these interactions · As an Application Architect we have identified existing systems and tools that can be extended and/or reused to help this application achieve it’s business goals · As a Project Manager all team members understand the goals of each release and iteration as they are planned · As a Project Manager all team members understand their role and the roles of others · As a Project Manager we have support of the business to do the right thing even if it is not the expedient thing · As a Test/QA Analyst we have created a simulation environment for testing the system which does not use sensitive data and accurately reflects the scenarios of all the data that will be supported by the system · As a Test/QA Analyst we have identified the matrix of supported clients used to access the system including the likely browsers, mobile devices and other interfaces to work with the application · As a Test/QA Analyst we have created exit criteria for each user story that match the requirements of the business story that was used to create them · As a Test/QA Analyst we have access to a Test environment that is isolated from production and staging environments · As a Test/QA Analyst there we have a way to reset the environment so we can rerun tests when a new version of the software becomes available · As a Test/QA Analyst I am able to automate portions of the test process Thoughts? -mike

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• Investment scheme for a PC game the project

  - by Alex Kamen

  Good day everyone, I am working on a PC game project that has 3 phases planned, micro, macro and mmo versions [if confused, see a brief description at the bottom]. I have found a potential investor for the micro version of the game, but naturally, he requested a detailed plan of how the game will pay back. And the problem is that micro version itself is not supposed to be monetized much, other than some ads and limited in-game currency utilization. The idea is that with this combat demo already at hand, it should be possible to get a really large enough investment (millions of dollars) and use it to pay back the initial small one (thousands of dollars) and take the project into macro phase, which will really make profit. This way, everybody is going to win, provided that I can deliver the end-product. Yet while I am confident of that both the conception of the macro and the real game-play of the micro versions are going to be appealing, I don’t know how to obtain any guarantee of that I will be able to get funded once I have the prototype ready. And without that, I won’t receive the funds for the prototype in the first place! To summarize, my question is: how to figure out my future possibilities of getting funded once I have combat demo out, basically “whom to write to and what”. Ideally, I would like some sort of a preliminary agreement with a game publisher, something that would basically state “If the developer provides the product in time and in quality corresponding to the specifications given, the publisher guarantees to allocate funds for distribution and further development, thereby acquiring the right to X part of all future profits”. Does this sound sane? It’s just that I don’t want to sell all of my rights out straight away by taking a big outside investment while the project is in such early stage. I would appreciate if you would share your thoughts on this kind of scheme, and be sure to ask questions as I am sure I must have forgotten to mention a ton of important things, like the fact that initial funds are going to be spent on outsourcing (living in Siberia is really just great). [here’s a brief outline of what each version will feature] [micro] 1) turn based tactical combat rules 2) character development 3) arena/tournament system [macro] 4) ai-ruled dynamic interactive worlds 5) global map adventuring 6) strategic rpg + god simulator gameplay [mmo] 7) Persistent worlds system 8) Social structures system (“guilds/clans”) 9) god-simulation on the mmo scale P.S. Obviously, these features are incremental, so that mmo version has all 9.

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• Simulate 'Shock absorbtion' with tire rubber in PhysX (2.8.x)

  - by Mungoid

  This is a kinda tricky question and I fear there is no easy enough solution, but I figured I'd hit SE up before giving up on it and just doing what I can. A machine I am working on has no suspension or shocks or springs of any sort in the real machine, so you would think that when it drives over bumps, it would shake like crazy but because its tires (6 of them) are quite large they seem to absorb a lot of shock from the bumps. Part of this is because the machine is around 30k lbs and it just smashes/compresses any bumps in the ground down (This is another issue im still working on) and the other part is that the tires seem to have a lot of flex to them with a lot of air as well. So my current task is to simulate shock absorption in physx without visibly separating the tires from the spindle/axle.. I have been messing with all kinds of NxMaterial, NxSpring, Joints, etc. and have had no luck getting this to work. The main problem is that the spindle attached to the tire is directly in the center and the axle is basically solidly attached to the chassis, so if i give it any spring or suspension travel, that spindle on the tires will move upwards or downwards, looking very odd because now its not any longer in the center of the tire. I tried giving it a higher restitution but that just makes it bouncy without any shock absorption. Another avenue I am messing with is to actively smooth the terrain in front of the tires so that before it hits a bumpy patch, that patch is smoothed and it doesn't bounce. The only issue with this is that it is pretty expensive to do with 6 tires, high tesselation of the terrain and other complex things going on at the same time in this simulation. I am still working on this but I am hoping to mix and match a few different aspects to get the best possible outcome. This is a bit of a complex issue so I'm not expecting anyone to have a definitive answer, just hoping someone may think of something I haven't =-) -Side note: Yes i know PhysX 2.8.x is quite outdated but we have to stick with it for this implementation. We are in the process of going to another physics engine but it is out of scope to apply that engine to this project.

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• When attaching AI to a vehicle should I define all steps or try Line of Sight?

  - by ThorDivDev

  This problem is related to an intersection simulation I am building for university. I will try to make it as general as possible. I am trying to assign AI to a vehicle using the JMonkeyEngine platform. AIGama_JmonkeyEngine explains that if you wish to create a car that follows a path you can define the path in steps. If there was no physics attached whatsoever then all you need to do is define the x,y,z values of where you want the object to appear in all subsequent steps. I am attaching the vehicleControl that implements jBullet. In this case the author mentions that I would need to define the steering and accelerating behaviors at each step. I was trying to use ghost controls that represented waypoints and when on colliding the car would decide what to do next like stopping at a red light. This didn't work so well. Car doesn't face right. public void update(float tpf) { Vector3f currentPos = aiVehicle.getPhysicsLocation(); Vector3f baseforwardVector = currentPos.clone(); Vector3f forwardVector; Vector3f subsVector; if (currentState == ObjectState.Running) { aiVehicle.accelerate(-800); } else if (currentState == ObjectState.Seeking) { baseforwardVector = baseforwardVector.normalize(); forwardVector = aiVehicle.getForwardVector(baseforwardVector); subsVector = pointToSeek.subtract(currentPos.clone()); System.out.printf("baseforwardVector: %f, %f, %f\n", baseforwardVector.x, baseforwardVector.y, baseforwardVector.z); System.out.printf("subsVector: %f, %f, %f\n", subsVector.x, subsVector.y, subsVector.z); System.out.printf("ForwardVector: %f, %f, %f\n", forwardVector.x, forwardVector.y, forwardVector.z); if (pointToSeek != null && pointToSeek.x + 3 >= currentPos.x && pointToSeek.x - 3 <= currentPos.x) { aiVehicle.steer(0.0f); aiVehicle.accelerate(-40); } else if (pointToSeek != null && pointToSeek.x > currentPos.x) { aiVehicle.steer(-0.5f); aiVehicle.accelerate(-40); } else if (pointToSeek != null && pointToSeek.x < currentPos.x) { aiVehicle.steer(0.5f); aiVehicle.accelerate(-40); } } else if (currentState == ObjectState.Stopped) { aiVehicle.accelerate(0); aiVehicle.brake(40); } }

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• Physics Engine [Collision Response, 2-dimensional] experts, help!! My stack is unstable!

  - by Register Sole

  Previously, I struggle with the sequential impulse-based method I developed. Thanks to jedediah referring me to this paper, I managed to rebuild the codes and implement the simultaneous impulse based method with Projected-Gauss-Seidel (PGS) iterative solver as described by Erin Catto (mentioned in the reference of the paper as [Catt05]). So here's how it currently is: The simulation handles 2-dimensional rotating convex polygons. Detection is using separating-axis test, with a SKIN, meaning closest points between two polygons is detected and determined if their distance is less than SKIN. To resolve collision, simultaneous impulse-based method is used. It is solved using iterative solver (PGS-solver) as in Erin Catto's paper. Error-correction is implemented using Baumgarte's stabilization (you can refer to either paper for this) using J V = beta/dt*overlap, J is the Jacobian for the constraints, V the matrix containing the velocities of the bodies, beta an error-correction parameter that is better be < 1, dt the time-step taken by the engine, and overlap, the overlap between the bodies (true overlap, so SKIN is ignored). However, it is still less stable than I expected :s I tried to stack hexagons (or squares, doesn't really matter), and even with only 4 to 5 of them, they hardly stand still! Also note that I am not looking for a sleeping scheme. But I would settle if you have any explicit scheme to handle resting contacts. That said, I would be more than happy if you have a way of treating it generally (as continuous collision, instead of explicitly as a special state). Ideas I have: I would try adding a damping term (proportional to velocity) to the Baumgarte. Is this a good idea in general? If not I would not want to waste my time trying to tune the parameter hoping it magically works. Ideas I have tried: Using simultaneous position based error correction as described in the paper in section 5.3.2, turned out to be worse than the current scheme. If you want to know the parameters I used: Hexagons, side 50 (pixels) gravity 2400 (pixels/sec^2) time-step 1/60 (sec) beta 0.1 restitution 0 to 0.2 coeff. of friction 0.2 PGS iteration 10 initial separation 10 (pixels) mass 1 (unit is irrelevant for now, i modified velocity directly<-impulse method) inertia 1/1000 Thanks in advance! I really appreciate any help from you guys!! :)

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• IndexOutOfRangeException on World.Step after enabling/disabling a Farseer physics body?

  - by WilHall

  Earlier, I posted a question asking how to swap fixtures on the fly in a 2D side-scroller using Farseer Physics Engine. The ultimate goal being that the player's physical body changes when the player is in different states (I.e. standing, walking, jumping, etc). After reading this answer, I changed my approach to the following: Create a physical body for each state when the player is loaded Save those bodies and their corresponding states in parallel lists Swap those physical bodies out when the player state changes (which causes an exception, see below) The following is my function to change states and swap physical bodies: new protected void SetState(object nState) { //If mBody == null, the player is being loaded for the first time if (mBody == null) { mBody = mBodies[mStates.IndexOf(nState)]; mBody.Enabled = true; } else { //Get the body for the given state Body nBody = mBodies[mStates.IndexOf(nState)]; //Enable the new body nBody.Enabled = true; //Disable the current body mBody.Enabled = false; //Copy the current body's attributes to the new one nBody.SetTransform(mBody.Position, mBody.Rotation); nBody.LinearVelocity = mBody.LinearVelocity; nBody.AngularVelocity = mBody.AngularVelocity; mBody = nBody; } base.SetState(nState); } Using the above method causes an IndexOutOfRangeException when calling World.Step: mWorld.Step(Math.Min((float)nGameTime.ElapsedGameTime.TotalSeconds, (1f / 30f))); I found that the problem is related to changing the .Enabled setting on a body. I tried the above function without setting .Enabled, and there was no error thrown. Turning on the debug views, I saw that the bodies were updating positions/rotations/etc properly when the state was changes, but since they were all enabled, they were just colliding wildly with each other. Does Enabling/Disabling a body remove it from the world's body list, which then causes the error because the list is shorter than expected? Update: For such a straightforward issue, I feel this question has not received enough attention. Has anyone else experienced this? Would anyone try a quick test case? I know this issue can be sidestepped - I.e. by not disabling a body during the simulation - but it seems strange that this issue would exist in the first place, especially when I see no mention of it in the documentation for farseer or box2d. I can't find any cases of the issue online where things are more or less kosher, like in my case. Any leads on this would be helpful.

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• Getting current time in milliseconds

  - by user90293423

  How to get the current time in milliseconds? I'm working on a hacking simulation game and when ever someone connects to another computer/NPC, a login screen popups with a button on the side called BruteForce. When BruteForce is clicked, what i want the program to do is, calculate how many seconds cracking the password is going to take based on the player's CPU speed but that's the easy part. The hard part is i want to enter a character in the password's box every X milliseconds based on a TimeToCrack divided by PasswordLength formula. But since i don't know how to find how many milliseconds have elapsed since the second has passed, the program waits until the CurrentTime is higher than the TimeBeforeTheLoopStarted + HowLongItTakesToTypeaCharacter which is always going to be a second. How would you handle my problems? I've commented the game breaking part. std::vector<QString> hardware = user.getHardware(); QString CPU = hardware[0]; unsigned short Speed = 0; if(CPU == "OMG SingleCore 1.8GHZ"){ Speed = 2; } const short passwordLength = password.length(); /* It's equal to 16 */ int Time = passwordLength / Speed; double TypeSpeed = Time / passwordLength; time_t t = time(0); struct tm * now = localtime(&t); unsigned short EndTime = (now->tm_sec + Time) % 60; unsigned short CurrentTime = 0; short i = passwordLength - 1; do{ t = time(0); now = localtime(&t); CurrentTime = now->tm_sec; do{ t = time(0); now = localtime(&t); }while(now->tm_sec < CurrentTime + TypeSpeed); /* Highly flawed */ /* Do this while your integer value is under this double value */ QString tempPass = password; tempPass.chop(i); ui->lineEdit_2->setText(tempPass); i--; }while(CurrentTime != EndTime);

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• cron doesn't execute any task, but writes into log as executed

  - by FractalizeR

  I have strange problem on one of my servers. Cron does not execute any task, but it writes to it's log, that task has been executed successfully. Like some simulation mode is activated... Apr 30 03:03:08 nd-10049 crond[13387]: (root) CMD (php /usr/local/frb/backup.php) Apr 30 03:05:01 nd-10049 crond[13397]: (root) CMD (php /home/support/public_html/cron/cron_hourly.php>/home/support/public_html/cron/hourly.log) Apr 30 03:09:01 nd-10049 crond[19108]: (root) CMD (/etc/webmin/cron/tempdelete.pl ) Apr 30 03:10:01 nd-10049 crond[19467]: (root) CMD (php /home/support/public_html/cron/cron_hourly.php>/home/support/public_html/cron/hourly.log) Apr 30 03:14:44 nd-10049 crontab[21154]: (root) BEGIN EDIT (root) Apr 30 03:15:01 nd-10049 crond[21309]: (root) CMD (php /home/support/public_html/cron/cron_hourly.php>/home/support/public_html/cron/hourly.log) Apr 30 03:15:38 nd-10049 crontab[21154]: (root) REPLACE (root) Apr 30 03:15:38 nd-10049 crontab[21154]: (root) END EDIT (root) Apr 30 03:16:01 nd-10049 crond[14961]: (root) RELOAD (cron/root) Apr 30 03:20:02 nd-10049 crond[22620]: (root) CMD (php /home/support/public_html/cron/cron_hourly.php) There are no errors about cron in common log (messages). The OS is CentOS. What can I do to check what is the problem? What can the problem be?

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• FastGate A20 Line And Himem.sys Issue With Updating BIOS

  - by Boris_yo

  I have been persistent with a thought to perform my first BIOS update ever through MS-DOS but have been postponing this task until today. Despite people telling me any bootable ISO will do it either through CD-ROM or RAMDRIVE, I am still having problems. First is the problem with CD-ROM driver trying to make it work with 4 driver files (cd1.SYS, cd2.SYS, cd3.SYS, cd4.SYS) as well as starting RAMDISK proved to be failure: CD-ROM XMS Allocation Error RAMDISK XMS Allocaton Error (X: and R: drives not working) This A20 line seemed to be the obstacle which then after a couple of searches pointed me to this article on Microsoft website. It seems that FastGate is the culprit which takes over A20 line and conflicts with himem.sys which should be handling it causing the driver to be unable to allocate memory resources. Albeit article suggests 2 workarounds which is disabling FastGate option or adding switch, I read that the former workaround could cause problems which involves later tinkering BIOS, disabling shadow copy etc. while the latter workaround can just hang system as stated in the link above. I assume it just hangs the boot process from image file though. Summing up the above, I am cautious and think it is risky to follow both workarounds because disabling FastGate or trying adding switch by trying available switches from 1-14 or 16, could crash the BIOS update process by itself. I could do this without the need for himem.sys with bootable USB thumbdrive by making it to be seen as USB-HDD, but some time ago I read that it is never a good idea to update BIOS from hard drive so even thought it is simulation, who knows... Maybe it will deactivate hard drive in the middle of the BIOS update process or even USB thumbdrive per se? One forum discussion was about updating BIOS and somebody suggested to not load himem.sys for some reason, but now that I think of it, what if BIOS update needs upper memory?

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• Distributing processing for an application that wasn't designed with that in mind

  - by Tim

  We've got the application at work that just sits and does a whole bunch of iterative processing on some data files to perform some simulations. This is done by an "old" Win32 application that isn't multi-processor aware, so new(ish) computers and workstations are mostly sitting idle running this application. However, since it's installed by a typical Windows Install Shield installer, I can't seem to install and run multiple copies of the application. The work can be split up manually before processing, enabling the work to be distributed across multiple machines, but we still can't take advantage of multiple core CPUs. The results can be joined back together after processing to make a complete simulation. Is there a product out there that would let me "compartmentalize" an installation (or 4) so I can take advantage of a multi-core CPU? I had thought of using MS Softgrid, but I believe that still depends on a remote server to do the heavy lifting (though please correct me if I'm wrong). Furthermore, is there a way I can distribute the workload off the one machine? So an input could be split into 50 chunks, handed out to 50 machines, and worked on? All without really changing the initial application? In a perfect world, I'd get the application to take advantage of a DesktopGrid (BOINC), but like most "mission critical corporate applications", the need is there, but the money is not. Thank you in advance (and sorry if this isn't appropriate for serverfault).

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• jQuery Ajax call - Set variable value on success.

  - by Nathan

  Hey all, I have an application that I am writing that modifies data on a cached object in the server. The modifications are performed through an ajax call that basically updates properties of that object. When the user is done working, I have a basic 'Save Changes' button that allows them to Save the data and flush the cached object. In order to protect the user, I want to warn them if the try to navigate away from the page when modifications have been made to the server object if they have not saved. So, I created a web service method called IsInitialized that will return true or false based on whether or not changes have been saved. If they have not been saved, I want to prompt the user and give them a chance to cancel their navigation request. Here's my problem - although I have the calls working correctly, I can't seem to get the ajax success call to set the variable value on its callback function. Here's the code I have now. ////Catches the users to keep them from navigation off the page w/o saved changes... window.onbeforeunload = CheckSaveStatus; var IsInitialized; function CheckSaveStatus() { var temp = $.ajax({ type: "POST", url: "URL.asmx/CheckIfInstanceIsInitilized", data: "{}", contentType: "application/json; charset=utf-8", dataType: "json", success: function(result) { IsInitialized = result.d; }, error: function(xmlHttpRequest, status, err) { alert(xmlHttpRequest.statusText + " " + xmlHttpRequest.status + " : " + xmlHttpRequest.responseText); } }); if (IsInitialized) { return "You currently have unprocessed changes for this Simulation."; } } I feel that I might be trying to use the Success callback in an inappropriate manner. How do I set a javascript variable on the Success callback so that I can decide whether or not the user should be prompted w/ the unsaved changes message? As was just pointed out, I am making an asynchronous call, which means the rest of the code gets called before my method returns. Is there a way to use that ajax call, but still catch the window.onunload event? (without making synchronos ajax)

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• Need help with artificial neural network

  - by deckard cain

  I have an input data for neural network that consists of 2 vectors with 200 elements, that i got from some program for generating signals. So it is actually 2x200 input to my nnet. As target data, i have one 1x200 vector that i also got from the same program. That is my training data set. I gather as much of those sets as i want so i transfer them to matlab and save them as, for example, set1, set2,.... When i am creating neural net, using newfit function (backropagation algorithm and everyhting else is set by default because i am kind of unexperianced with neural nets so i will have to experiment) i'm creating it using set1 only for example. Then, when i am to train neural net i train it for set1 then load set2 and train for it and so on. so its like this function net = create_fit_net(inputs,targets) numHiddenNeurons = 20; net = newfit(inputs,targets,numHiddenNeurons); net=train(net,inputs,targets); load set2; net=train(net,inputs,targets); load set3; net=train(net,inputs,targets); load set4; net=train(net,inputs,targets); i am using 4 sets of data here and all sets have variables of same name and size. My quesion is, am i doing this the right way, because, when doing simulation in some other m file, i am getting bad results, and every time i get different results. Does it matter if i create network with one set and then train with others too, and does it matter what set do i use to train network 1st? Also, i am confused about the amount of neurons to use (im using in the example 20 but actually i tried 1, 10, 30, 50, 100 200 and even 300 and i get nothing). If you have any suggestions, i'd be glad to take them into consideration. Any help is welcome. thanks in advance

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• Why does Raphael's framerate slow down on this code?

  - by Bob

  So I'm just doing a basic orbit simulator using Raphael JS, where I draw one circle as the "star" and another circle as the "planet". It seems to be working just fine, with the one snag that as the simulation continues, its framerate progressively slows down until the orbital motion no longer appears fluid. Here's the code (note: uses jQuery only to initialize the page): $(function() { var paper = Raphael(document.getElementById('canvas'), 640, 480); var star = paper.circle(320, 240, 10); var planet = paper.circle(320, 150, 5); var starVelocity = [0,0]; var planetVelocity = [20.42,0]; var starMass = 3.08e22; var planetMass = 3.303e26; var gravConstant = 1.034e-18; function calculateOrbit() { var accx = 0; var accy = 0; accx = (gravConstant * starMass * ((star.attr('cx') - planet.attr('cx')))) / (Math.pow(circleDistance(), 3)); accy = (gravConstant * starMass * ((star.attr('cy') - planet.attr('cy')))) / (Math.pow(circleDistance(), 3)); planetVelocity[0] += accx; planetVelocity[1] += accy; planet.animate({cx: planet.attr('cx') + planetVelocity[0], cy: planet.attr('cy') + planetVelocity[1]}, 150, calculateOrbit); paper.circle(planet.attr('cx'), planet.attr('cy'), 1); // added to 'trace' orbit } function circleDistance() { return (Math.sqrt(Math.pow(star.attr('cx') - planet.attr('cx'), 2) + Math.pow(star.attr('cy') - planet.attr('cy'), 2))); } calculateOrbit(); }); It doesn't appear, to me anyway, that any part of that code would cause the animation to gradually slow down to a crawl, so any help solving the problem will be appreciated!

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• glitchy stuttery iphone game loop

  - by Adam

  This is a problem I've been trying to solve for a few days now, and I've looked at the various solutions on stackoverflow and nothing has really seemed to work for me. I'm making an iPhone game with OpenGLES graphics and accelerometer input, at this point it's very simple, but the rendering is already pretty bad... it stutters and seems to jump back or forward in time. It doesn't happen a lot, but it happens enough to be a problem. I mean, who wants to play a game where a bullet gets magically transported into the player, and then it's game over? No one. I've tried using NSTimer for the game loop, I've tried using a separate thread (with a frame rate and continuously) I've tried using different frame rates, from 30FPS to 60FPS (It seems to have a max frame rate around 45FPS, but no problems at 30FPS) I've tried using timeIntervalSince1970 and CFGetAbsoluteTime to measure loop time, with no noticeable diffence Anyone have any ideas on what is the best way to get this looking better? One of the posts I've read suggested running the simulation at a fixed frame rate and then just render as fast as possible, does that seem like a good idea?

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• Error mounting CloudDrive snapshot in Azure

  - by Dave

  Hi, I've been running a cloud drive snapshot in dev for a while now with no probs. I'm now trying to get this working in Azure. I can't for the life of me get it to work. This is my latest error: Microsoft.WindowsAzure.Storage.CloudDriveException: Unknown Error HRESULT=D000000D ---> Microsoft.Window.CloudDrive.Interop.InteropCloudDriveException: Exception of type 'Microsoft.WindowsAzure.CloudDrive.Interop.InteropCloudDriveException' was thrown. at ThrowIfFailed(UInt32 hr) at Microsoft.WindowsAzure.CloudDrive.Interop.InteropCloudDrive.Mount(String url, SignatureCallBack sign, String mount, Int32 cacheSize, UInt32 flags) at Microsoft.WindowsAzure.StorageClient.CloudDrive.Mount(Int32 cacheSize, DriveMountOptions options) Any idea what is causing this? I'm running both the WorkerRole and Storage in Azure so it's nothing to do with the dev simulation environment disconnect. This is my code to mount the snapshot: CloudDrive.InitializeCache(localPath.TrimEnd('\\'), size); var container = _blobStorage.GetContainerReference(containerName); var blob = container.GetPageBlobReference(driveName); CloudDrive cloudDrive = _cloudStorageAccount.CreateCloudDrive(blob.Uri.AbsoluteUri); string snapshotUri; try { snapshotUri = cloudDrive.Snapshot().AbsoluteUri; Log.Info("CloudDrive Snapshot = '{0}'", snapshotUri); } catch (Exception ex) { throw new InvalidCloudDriveException(string.Format( "An exception has been thrown trying to create the CloudDrive '{0}'. This may be because it doesn't exist.", cloudDrive.Uri.AbsoluteUri), ex); } cloudDrive = _cloudStorageAccount.CreateCloudDrive(snapshotUri); Log.Info("CloudDrive created: {0}", snapshotUri, cloudDrive); string driveLetter = cloudDrive.Mount(size, DriveMountOptions.None); The .Mount() method at the end is what's now failing. Please help as this has me royally stumped! Thanks in advance. Dave

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• Run a .java file using ProcessBuilder

  - by David K

  I'm a novice programmer working in Eclipse, and I need to get multiple processes running (this is going to be a simulation of a multi-computer system). My initial hackup used multiple threads to multiple classes, but now I'm trying to replace the threads with processes. From my reading, I've gleaned that ProcessBuilder is the way to go. I have tried many many versions of the input you see below, but cannot for the life of me figure out how to properly use it. I am trying to run the .java files I previously created as classes (which I have modified). I eventually just made a dummy test.java to make sure my process is working properly - its only function is to print that it ran. My code for the two files are below. Am I using ProcessBuilder correctly? Is this the correct way to read the output of my subprocess? Any help would be much appreciated. David primary process package Control; import java.io.*; import java.lang.*; public class runSPARmatch { /** * @param args */ public static void main(String args[]) { try { ProcessBuilder broker = new ProcessBuilder("javac.exe","test.java","src\\Broker\\"); Process runBroker = broker.start(); Reader reader = new InputStreamReader(runBroker.getInputStream()); int ch; while((ch = reader.read())!= -1) System.out.println((char)ch); reader.close(); runBroker.waitFor(); System.out.println("Program complete"); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } subprocess package Broker; public class test { /** * @param args */ public static void main(String[] args) { // TODO Auto-generated method stub System.out.println("This works"); } }

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• What version control system is best designed to *prevent* concurrent editing?

  - by Fred Hamilton

  We've been using CVS (with TortoiseCVS interface) for years for both source control and wide-ranging document control (including binaries such as Word, Excel, Framemaker, test data, simulation results, etc.). Unlike typical version control systems, 99% of the time we want to prevent concurrent editing - when a user starts editing a file, the pre-edit version of the file becomes read only to everyone else. Many of the people who will be using this are not programmers or even that computer savvy, so we're also looking for a system that let's people simply add documents to the repository, check out and edit a document (unless someone else is currently editing it), and check it back in with a minimum of fuss. We've gotten this to work reasonably well with CVS + TortoiseCVS, but we're now considering Subversion and Mercurial (and open to others if they're a better fit) for their better version tracking, so I was wondering which one supported locking files most transparently. For example, we'd like exclusive locking enabled as the default, and we want to make it as difficult as possible for someone to accidentally start editing a file that someone else has checked out. For example when someone checks out a file for editing, it checks with the master database first even if they have not recently updated their sandbox. Maybe it even won't let a user check out a document if it's off the network and can't check in with the mothership.

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• UINavigationController navigation stack problems in Landscape Mode

  - by David F

  I have a iPhone application that I am currently converting to a Universal Binary to work with the iPad. I have successfully implemented everything I need in terms of layout so that full landscape functionality is now supported in my app (previously I primarily used portrait mode to display content). But, I have one strange problem, and it ONLY occurs in landscape mode: when I push a view controller onto the stack, it takes two taps on the back button to return to the previous view controller!!! The first tap shows a blank view, but with the same name on the left-side back navigation button, the second tap takes the controller back to previous view like it should. I don't have an iPad to test, so I am relying on the simulator. The problem does not show up on the iPhone and doesn't show up if you rotate back to portrait mode. My app consists of a tabbarcontroller with navigation controllers loaded for its vc's: //application delegate - (void)applicationDidFinishLaunching:(UIApplication *)application //.... WebHelpViewController *vc8 = [[WebHelpViewController alloc] init]; UINavigationController *nv8 = [[UINavigationController alloc] initWithRootViewController:vc8]; [self.tabBarController setViewControllers:[NSArray arrayWithObjects:nv1,nv2,nv3,nv4,nv5,nv6,nv7,nv8,nil]]; To implement landscape capability, the UITabBarController is overridden to autorotate when required: //CustomTabBarController.m - (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation { return [[(UINavigationController *)self.selectedViewController topViewController] shouldAutorotateToInterfaceOrientation:interfaceOrientation]; } ... works fine. I navigate into new views using this method SomeViewController *vc = [[SomeViewController alloc] init]; [self.navigationController pushViewController:vc animated:YES]; [vc release]; Has anyone encountered this problem, and do they know if it's only a simulation error?

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• Use of const double for intermediate results

  - by Arne

  Hi, I a writing a Simulation program and wondering if the use of const double is of any use when storing intermediate results. Consider this snippet: double DoSomeCalculation(const AcModel &model) { (...) const double V = model.GetVelocity(); const double m = model.GetMass(); const double cos_gamma = cos(model.GetFlightPathAngleRad()); (...) return m*V*cos_gamma*Chi_dot; } Note that the sample is there only to illustrate -- it might not make to much sense from the engineering side of things. The motivation of storing for example cos_gamma in a variable is that this cosine is used many time in other expressions covered by (...) and I feel that the code gets more readable when using cos_gamma rather than cos(model.GetFlightPathAngleRad()) in various expressions. Now the actual is question is this: since I expect the cosine to be the same througout the code section and I actually created the thing only as a placeholder and for convenience I tend to declare it const. Is there a etablished opinion on wether this is good or bad practive or whether it might bite me in the end? Does a compiler make any use of this additional information or am I actually hindering the compiler from performing useful optimizations? Arne

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• List of objects or parallel arrays of properties?

  - by Headcrab

  The question is, basically: what would be more preferable, both performance-wise and design-wise - to have a list of objects of a Python class or to have several lists of numerical properties? I am writing some sort of a scientific simulation which involves a rather large system of interacting particles. For simplicity, let's say we have a set of balls bouncing inside a box so each ball has a number of numerical properties, like x-y-z-coordinates, diameter, mass, velocity vector and so on. How to store the system better? Two major options I can think of are: to make a class "Ball" with those properties and some methods, then store a list of objects of the class, e. g. [b1, b2, b3, ...bn, ...], where for each bn we can access bn.x, bn.y, bn.mass and so on; to make an array of numbers for each property, then for each i-th "ball" we can access it's 'x' coordinate as xs[i], 'y' coordinate as ys[i], 'mass' as masses[i] and so on; To me it seems that the first option represents a better design. The second option looks somewhat uglier, but might be better in terms of performance, and it could be easier to use it with numpy and scipy, which I try to use as much as I can. I am still not sure if Python will be fast enough, so it may be necessary to rewrite it in C++ or something, after initial prototyping in Python. Would the choice of data representation be different for C/C++? What about a hybrid approach, e.g. Python with C++ extension?

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• C# WinForms. Multiple Forms in separate threads

  - by Calum Murray

  I'm trying to run an ATM Simulation in C# with Windows Forms that can have more than one instance of an ATM machine transacting with a bank account simultaneously. The idea is to use semaphores/locking to block critical code that may lead to race conditions. My question is this: How can I run two Forms simultaneously on separate threads? In particular, how does all of this fit in with the Application.Run() that's already there? Here's my main class: public class Bank { private Account[] ac = new Account[3]; private ATM atm; public Bank() { ac[0] = new Account(300, 1111, 111111); ac[1] = new Account(750, 2222, 222222); ac[2] = new Account(3000, 3333, 333333); Application.Run(new ATM(ac)); } static void Main(string[] args) { new Bank(); } } ...that I want to run two of these forms on separate threads... public partial class ATM : Form { //local reference to the array of accounts private Account[] ac; //this is a reference to the account that is being used private Account activeAccount = null; private static int stepCount = 0; private string buffer = ""; // the ATM constructor takes an array of account objects as a reference public ATM(Account[] ac) { InitializeComponent(); //Sets up Form ATM GUI in ATM.Designer.cs this.ac = ac; } ... I've tried using Thread ATM2 = new Thread(new ThreadStart(/*What goes in here?*/)); But what method do I put in the ThreadStart constructor, since the ATM form is event-driven and there's no one method controlling it? Thanks, Calum

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