41) Message boards : News : Updates (Message 63769) Posted 25 Jun 2015 by Sidd Post: Hey all, Jake Weiss and I will be making fairly regular updates on the status of the project under the Application Code Discussion part of the forum. Cheers, Sidd

42) Message boards : Application Code Discussion : Nbody Status Update (Message 63768) Posted 25 Jun 2015 by Sidd Post: Hey All, Just a quick update on the status of Nbody. I discovered that the hanging that people were experiencing were due to the Newton Raphson root finding algorithm which would get stuck in an infinite loop. After looking for why this occurred for sometime, I decided to switch to a bisection method which is insured not to get stuck. The slow nature of the initialization of the plummer was found to be an error in the calculation of one of the limits of integration in a crucial integral that was being calculated. What a time it was finding that! With that limit fixed, it seems that the initialization takes a few seconds! I am currently unit testing the code and hopefully should get a lovely new version in a couple of weeks. Cheers, Sidd

43) Message boards : News : Windows Users-please abort Nbody tasks (Message 63670) Posted 4 Jun 2015 by Sidd Post: Cherokee150, Thank you! Your info is remarkably helpful. I think I have a line on a bug that might be occurring. If there is no checkpointing at all then that means it is probably the initialization that is getting stuck somewhere. I am looking into where. Thanks! Sidd

44) Message boards : News : server issues (Message 63664) Posted 3 Jun 2015 by Sidd Post: Hey all, We are currently having a few issues with the server. Everything seems to be up and running yet no work units are being sent out. If any of you see any erroneous behavior on your end please let us know. Thanks, Sidd

45) Message boards : News : Windows Users-please abort Nbody tasks (Message 63647) Posted 31 May 2015 by Sidd Post: Hey, I'd say keep it checked. When we next release we will make an announcement. Thanks! Sidd

46) Message boards : News : Windows Users-please abort Nbody tasks (Message 63644) Posted 29 May 2015 by Sidd Post: Hey all, I am sorry that there has been so many bugs in the Nbody recently. The reason for it all comes down to the fact that we are developing a lot of new code for the app. We completely changed how we did the initialization to properly align with the science. That change led to a longer initialization time, which was inevitable. Next we changed how the dark and light matter were assigned. We are currently working on changing the sampling method used in the initialization which is another very drastic change, but should greatly speed up the initialization. As was said by Wisesooth, with so much development and for so many different platforms, we are bound to run into numerous unexpected problems. We cannot fully predict all of the issues beforehand. For example, it is plausible that one set of simulation parameters can lead to an extremely long run time, longer than predicted. These very specific parameters may not have been in our test cases, especially since each parameter goes to the 14th decimal place. In fact, if were able to test all of the possible parameters, we wouldn't need to use MW@H for optimization. Also, I think this may be one of the reasons some people are having such long simulation time. From the error reporting I have seen, much of the reported errors are in fact platform dependent. As for the broken windows binary during this release, this was very unfortunate. Though, I believe this was a binary issue and not due to the algorithm, I understand the level of frustration it caused. I hope to have the issue resolved before the next release so that we can release a windows version of the app. Although I may not have responded right away, I have read all of your posts and your feedback is vital to debugging our algorithm. I know there are many issues that still need to be worked on. We are working hard to fix them all. Please remain patient as we do so. NBODY is an amazing concept and app and we are working tirelessly to try and get it working the way it should. With much thanks, Sidd

47) Message boards : News : Windows Users-please abort Nbody tasks (Message 63608) Posted 16 May 2015 by Sidd Post: Hey All, I apologize for the silence. I am looking into the problem. We had issues with getting the windows version ready for release, and I believe something went wrong in the process. I ran those binaries on windows and they seemed to have worked properly at the time. However, it seems that no windows runs are working. The other versions of the code are ok so far and I am getting results on my end. If you have nbody running and stalled abort it for now. I deprecated the windows version of the app but I believe some may still be sent out before it is completely down. This was an unexpected problem with the binaries as they worked on our end, and I apologize for the issues you are having and the frustration incurred. Please be patient, as we are working on the issues. Thanks, Sidd

48) Message boards : News : New Nbody Version 1.50 (Message 63607) Posted 16 May 2015 by Sidd Post: Hey All, I apologize for the silence. I am looking into the problem. We had issues with getting the windows version ready for release, and I believe something went wrong in the process. I ran those binaries on windows and they seemed to have worked properly at the time. However, it seems that no windows runs are working. The other versions of the code are ok so far and I am getting results on my end. If you have nbody running and stalled abort it for now. I deprecated the windows version of the app but I believe some may still be sent out before it is completely down. This was an unexpected problem with the binaries as they worked on our end, and I apologize for the issues you are having and the frustration incurred. Please be patient, as we are working on the issues. Thanks, Sidd

49) Message boards : News : New Nbody Version 1.50 (Message 63554) Posted 12 May 2015 by Sidd Post: Hey all, We have released a new version of Nbody. There are a few changes in this version. First and foremost, we changed the way dark and light matter in our model dwarf galaxy is assigned. Previously, we would have all the particles have the same mass and assign a certain number as dark or light, depending on the parameters of the simulation. This required a large number of bodies in order to get a good likelihood calculation. Now, we will have the same number of dark and light matter particles, but change the mass per light and dark matter particle in accordance to the parameters. This will allow us to lower the number of bodies from 50k to 20k, allowing for a much faster initialization and simulation run time. Secondly, we have moved the assignment of dark and light matter from lua to c, which should also provide significant speed up in the run time. Also, we fixed a number of bugs we found in the velocity assignment. All in all, a simulation should run at a fraction of the time previously. This will also hopefully fix the stalling issue some people have been having. Finally, if you have any runs from the previously version, you can go ahead and abort them. Since this is a new way of doing things, there may be some unforeseen issues. So, if there are any bugs let us know!

50) Message boards : News : New Nbody release tomorrow (Message 63520) Posted 4 May 2015 by Sidd Post: Hey All, I just wanted to let you know that we will be releasing a version of Nbody tomorrow. I will be more specific on the changes that have been made after releasing. However, this version should hopefully be much faster and fix some other bugs.

51) Message boards : News : New Bitcoin Utopia Campaign (Message 63459) Posted 24 Apr 2015 by Sidd Post: Hey All, Bitcoin Utopia is holding another fundraising campaign for MilkyWay@home! Check it out: http://www.bitcoinutopia.com/2014/07/milkywayhome/#.VTqEAic4l4u

52) Message boards : News : New Nbody version 1.48 (Message 63203) Posted 5 Mar 2015 by Sidd Post: Hey, The initialization procedure, unfortunately, is not currently worked into the time estimate. We are working on this. Since some parameters will take a bit longer to run than others, in some work units the estimate will say 100% but the simulation may still be running. However, if the simulation takes an egregious amount of time (on the order of a large fraction of the simulation time thus far) to finish after reaching 100% you can go ahead and cancel it. However, there should not be any infinite loops occurring in this version.

53) Message boards : News : New Nbody version 1.48 (Message 63191) Posted 2 Mar 2015 by Sidd Post: Hey, It seems some of the runs you had were v1.46. If these are stalled you can abort them.

54) Message boards : News : New Nbody version 1.48 (Message 63146) Posted 15 Feb 2015 by Sidd Post: Hey, We had multithreaded the assignments of radii and velocities to bodies. Both of these were done through rejection sampling, using random numbers. However, when that code ran with multiple threads the assignment of radii and velocity were different between runs even with the same random number seed and parameters. This was because which thread ran in which order was indeterminate, meaning which body was assign what radii and velocity was unpredictable. This was a very nasty bug, made nastier because it did not present itself. Runs would complete normally. However, because of the indeterminate nature of the algorithm, a poorer likelihood was reported than would be expected with a set of parameters, even if they were close. Therefore, overall, it led to poor convergence. Therefore, for now, we removed all multithreading of the initialization of the dwarf galaxy. This is why it will run only on one thread until the initialization completes. However, after performing a speed profile on the code, it was determined that a majority of the run time of the previous code was spent on a single function (thanks to Roland Judd for catching that!). We optimized this function, leading to a great decrease in the run time. Cheers, Sidd

55) Message boards : News : New Nbody version 1.48 (Message 63141) Posted 14 Feb 2015 by Sidd Post: Hi, This was expected. The initialization routine is longer than before since we are doing it by a more rigorous and scientifically accurate method. However, we have not yet multi-threaded it as of yet. We attempted to previously but it made the program indeterminate. This is something we will work on.

56) Message boards : News : New Nbody version 1.48 (Message 63137) Posted 13 Feb 2015 by Sidd Post: Hey All, I have released a new version of Nbody. This version corrects some bugs in the algorithm. Also, we performed some optimization on the initialization code which allows it to run much faster. We will be looking to change the time estimate to fully account for this initialization in the future. As always, thank you for your patience. Cheers, Sidd

57) Message boards : News : New Nbody version 1.46 (Message 63135) Posted 12 Feb 2015 by Sidd Post: Hey All, Your issues have not fallen on deaf ears! I looked into many of these errors and found some nasty little bugs. We will be releasing a new version soon which should rectify many of the issues you all are having. Thank you for your patience. Cheers, Sidd

58) Message boards : News : You saved MilkyWay@home!! (Message 62966) Posted 6 Jan 2015 by Sidd Post: Hi, Thank you for your offer. Please contact Walter Williams to find out how to go about doing this. His contact information is as follows: Walter Williams. Phone: 518-276-2974; E-mail: williw5@rpi.edu. Thank you, Sidd

59) Message boards : News : New Nbody version 1.46 (Message 62961) Posted 5 Jan 2015 by Sidd Post: Hey All, It seems there has been an issue with the newly added multithreading routines in this version. It seems this is the main error most people are having.I will work on finding a solution to this problem. This version's initialization algorithm requires significantly more time to complete which would explain why some people would have a low percentage increase at the start. We will try to change the time estimation routines to account for this properly. Cheers, Sidd

60) Message boards : News : New Nbody version 1.46 (Message 62863) Posted 19 Dec 2014 by Sidd Post: Hey Everyone, There is now a new version of Nbody, 1.46. This version calculates the initial Dwarf galaxy using a different method than previously. It should solve many of the work unit stalling issues some users were having. If there are any errors let us know. The runs currently up are: ps_nbody_12_19_orphan_sim_1 de_nbody_12_19_orphan_sim_1

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