tag:blogger.com,1999:blog-5822805028291837738.comments2017-11-18T11:45:16.556-05:00Various ConsequencesJoshua Stultshttp://www.blogger.com/profile/03506970399027046387noreply@blogger.comBlogger735125tag:blogger.com,1999:blog-5822805028291837738.post-30507407517169314182017-11-18T11:45:16.556-05:002017-11-18T11:45:16.556-05:00The bottom line: Download adobe Photoshop 7.0 grea...The bottom line: <a href="https://www.youtube.com/watch?v=y7dLFZv9NsM" rel="nofollow">Download adobe Photoshop 7.0</a> greatly expands the toolset that Adobe offers in its ... Operating Systems, Windows XP/Vista/7 ... Downloads Last Week, 1,466 ...Rajibhttps://www.blogger.com/profile/10808406775825439682noreply@blogger.comtag:blogger.com,1999:blog-5822805028291837738.post-84853551653450429142017-11-14T06:00:12.627-05:002017-11-14T06:00:12.627-05:00Here's an approach to speeding up a lattice-Bo...Here's an approach to speeding up a lattice-Boltzmann solver: <a href="http://www.variousconsequences.com/2017/11/deep-learning-to-accelerate-computational-fluid-dynamics.html" rel="nofollow">Deep Learning to Accelerate Computational Fluid Dynamics</a> Joshua Stultshttps://www.blogger.com/profile/03506970399027046387noreply@blogger.comtag:blogger.com,1999:blog-5822805028291837738.post-552648649134589252017-11-10T07:38:32.357-05:002017-11-10T07:38:32.357-05:00Machine learning for supper fast simulations has a...<a href="https://www.reddit.com/r/CFD/comments/5n91uz/cfd_machine_learning_for_super_fast_simulations/" rel="nofollow">Machine learning for supper fast simulations</a> has an interesting comment: "...While I find this an interesting approach, it seems to me to be really confusing to talk about 'acceleration' and 'speed-up' in the way you are, because you're doing a COMPLETELY different thing from what a standard solver is doing. "<br /><br />That's why it's surprising! <a href="http://www.shipulski.com/2017/11/08/the-power-of-surprise/" rel="nofollow">Surprise is powerful</a>... Joshua Stultshttps://www.blogger.com/profile/03506970399027046387noreply@blogger.comtag:blogger.com,1999:blog-5822805028291837738.post-40794640186232155102017-02-12T11:04:58.965-05:002017-02-12T11:04:58.965-05:00Somewhat related: Why We Mix Fact & Value Tal...Somewhat related: <a href="http://www.overcomingbias.com/2017/02/we-we-mix-fact-value-talk.html" rel="nofollow">Why We Mix Fact & Value Talk</a>Joshua Stultshttps://www.blogger.com/profile/03506970399027046387noreply@blogger.comtag:blogger.com,1999:blog-5822805028291837738.post-85754331432921768342017-02-12T10:35:43.091-05:002017-02-12T10:35:43.091-05:00ToPy is on github nowToPy is <a href="https://github.com/williamhunter/topy" rel="nofollow">on github</a> now Joshua Stultshttps://www.blogger.com/profile/03506970399027046387noreply@blogger.comtag:blogger.com,1999:blog-5822805028291837738.post-33818979864686134112016-12-18T09:41:36.260-05:002016-12-18T09:41:36.260-05:00Here's an example Parareal implementation in p...Here's an example Parareal implementation in python for 3D Burger's equation on <a href="https://github.com/Parallel-in-Time/PararealF90" rel="nofollow">github</a>; also <a href="https://arxiv.org/abs/1509.06935" rel="nofollow">the paper</a> to go with the code. <br />Joshua Stultshttps://www.blogger.com/profile/03506970399027046387noreply@blogger.comtag:blogger.com,1999:blog-5822805028291837738.post-83893380478378921122016-01-09T08:05:58.740-05:002016-01-09T08:05:58.740-05:00Thanks for your comments on this post. Definitely...Thanks for your comments on this post. Definitely provoked some more thought on my part. <br /><br />The similarity with converging Markov Chains, and sensitivity to initial conditions is a pretty good analogy. It's not perfect though. The reason you get different answers from two Markov Chains you started with different initializations is that you haven't run them long enough. So the difference is down to error. <br /><br />Jaynes' point is subtly different: <i>disagreement can legitimately exist without any error by either party</i>. Joshua Stultshttps://www.blogger.com/profile/03506970399027046387noreply@blogger.comtag:blogger.com,1999:blog-5822805028291837738.post-29115152334250614522015-11-26T09:21:58.068-05:002015-11-26T09:21:58.068-05:00Thanks for commenting. I agree: where you start ...Thanks for commenting. I agree: where you start matters in a couple of ways. The priors for the claim itself matter, and those are likely to be correlated with priors that effect how you evaluate incoming evidence. The evidence is hardly ever just "the evidence". It's usually another claim, and the who/what/where/how/why of the claim matter. Joshua Stultshttps://www.blogger.com/profile/03506970399027046387noreply@blogger.comtag:blogger.com,1999:blog-5822805028291837738.post-57539375067300114762015-10-23T15:14:49.194-04:002015-10-23T15:14:49.194-04:00Seems like a markov chain with differing starting ...Seems like a markov chain with differing starting points.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-5822805028291837738.post-70068781606802588352015-10-23T02:27:06.474-04:002015-10-23T02:27:06.474-04:00Ah, just reread my comment. I meant the probabilit...Ah, just reread my comment. I meant the probabilities of "given the claim is true, my opponent would have claimed it to be true " vs. "given the claim is false, my opponent would still have claimed it to be true". Of these two, the first one should have higher probability, which should shift my belief the appropriate (possibly infinitesimal) amount towards agreement.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-5822805028291837738.post-79225387860533997912015-10-23T02:22:43.381-04:002015-10-23T02:22:43.381-04:00Isn't it still irrational (i.e., ignoring the ...Isn't it still irrational (i.e., ignoring the result of a Bayesian calculation) to assign a higher probability to "the claim is false and my opponents claim it to be true despite it because that furthers their agenda" than to "the claim is true and my opponents claim it to be true either because it is true or because they would have done so in any case". The fact that my opponent whom I believe to be deceitful states a factual claim that supports his position should never lower my probability for this claim, since the probability that he will state the claim is still slightly higher if it is true than if it is false. For example, if it is false there is an incentive for my opponent to just not mention it instead of perpetuating it, because being found out as a fraud can have negative impact on one's cause.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-5822805028291837738.post-40290970539966218702015-09-07T17:10:26.408-04:002015-09-07T17:10:26.408-04:00Here's a good list of CAD software: Open Sour...Here's a good list of CAD software: <a href="http://opensourceecology.org/wiki/CAD_tools" rel="nofollow">Open Source Ecology: CAD Tools</a>Joshua Stultshttps://www.blogger.com/profile/03506970399027046387noreply@blogger.comtag:blogger.com,1999:blog-5822805028291837738.post-78594870759887295922015-08-21T21:38:36.238-04:002015-08-21T21:38:36.238-04:00Added the NASA CFD Utilities Library to the Open S...Added the <a href="http://sourceforge.net/projects/cfdutilities/" rel="nofollow">NASA CFD Utilities Library</a> to the <a href="http://www.variousconsequences.com/p/open-source-aeronautical-engineering.html" rel="nofollow">Open Source Aeronautical Engineering Tools</a> list.Joshua Stultshttps://www.blogger.com/profile/03506970399027046387noreply@blogger.comtag:blogger.com,1999:blog-5822805028291837738.post-53820978692561190082015-06-23T10:35:46.488-04:002015-06-23T10:35:46.488-04:00Boyd's book is free to download in pdf or brow...Boyd's book is free to <a href="https://scholar.google.com/scholar?q=boyd+chebyshev+and+fourier+spectral+methods" rel="nofollow">download in pdf</a> or <a href="https://books.google.com/books?id=lEWnQWyzLQYC&lpg=PA1&ots=WSdLuFo4uu&dq=boyd%20chebyshev%20and%20fourier%20spectral%20methods&lr&pg=PA1#v=onepage&q&f=false" rel="nofollow">browse on google books</a>.Joshua Stultshttps://www.blogger.com/profile/03506970399027046387noreply@blogger.comtag:blogger.com,1999:blog-5822805028291837738.post-60160810302659077212015-06-23T10:24:10.298-04:002015-06-23T10:24:10.298-04:00See the sections in Chapter 6 of Boyd's book w...See the sections in Chapter 6 of Boyd's book with the heading "Special Problems in Higher Dimensions:" for some pointers that might be helpful. Good luck with your calculation; would love to see your results when you get them. Joshua Stultshttps://www.blogger.com/profile/03506970399027046387noreply@blogger.comtag:blogger.com,1999:blog-5822805028291837738.post-84703092080092852722015-06-23T09:52:46.719-04:002015-06-23T09:52:46.719-04:00Hi Amit,
It's hard to tell what might be goi...Hi Amit, <br />It's hard to tell what might be going wrong with your code without more details. What grid point distribution are you using? For your periodic tests you probably used evenly spaced points. Are you using a Chebyshev roots grid for your non-periodic tests? Joshua Stultshttps://www.blogger.com/profile/03506970399027046387noreply@blogger.comtag:blogger.com,1999:blog-5822805028291837738.post-23781891628291629442015-06-02T22:26:36.083-04:002015-06-02T22:26:36.083-04:00Great blog! I am trying to compute laplacian of a...Great blog! I am trying to compute laplacian of a 2D function (non-periodic) using FFT technique. I first tested periodic functions and things work just fine. I am trying to extent your example to 2D function but cannot seem to figure our the recurrence for the derivative. My trial function is exp(x+y) sampled on grid with Nx and Ny points along x and y axis. The analytical result is 2.0*exp(x+y). I can send you my code if you want to see - but I have no luck so far. Any clues? Please help. Thx AmitAmit Sharmahttps://www.blogger.com/profile/17215657575191151707noreply@blogger.comtag:blogger.com,1999:blog-5822805028291837738.post-23291857618042967332015-04-11T17:03:19.966-04:002015-04-11T17:03:19.966-04:00The primary purpose of the Urban Aero Systems is t...The primary purpose of the Urban Aero Systems is to introduce cutting-edge aerospace technologies, while having its own modern infrastructure, with an experienced team in Aviation<br /><a href="http://www.urbanaerosystems.com/aeroboats/" title="Inflatable Boats in India" rel="nofollow">Inflatable Boats in India</a><br /><a href="http://www.urbanaerosystems.com/partners/" title="Fec Heliports" rel="nofollow">Fec Heliports</a><br />Surelia Devhttps://www.blogger.com/profile/00213607497253152006noreply@blogger.comtag:blogger.com,1999:blog-5822805028291837738.post-34515996029904430082015-03-28T07:40:55.584-04:002015-03-28T07:40:55.584-04:00Someone at facebook has done their drone history h...Someone at facebook has done their drone history homework. They are naming their <a href="http://blogs.wsj.com/digits/2015/03/26/facebook-moving-ahead-with-drone-plans-test-this-summer/" rel="nofollow">internet in the sky drone</a> "Aquila." Which was also the name of <a href="http://en.wikipedia.org/wiki/Lockheed_MQM-105_Aquila" rel="nofollow">a target designation drone</a> developed by DARPA and the Army. Joshua Stultshttps://www.blogger.com/profile/03506970399027046387noreply@blogger.comtag:blogger.com,1999:blog-5822805028291837738.post-10418197784480112392015-02-07T08:32:34.978-05:002015-02-07T08:32:34.978-05:00The gpml software is very well documented. I like...The gpml software is very well documented. I like the way their user documentation (doc/index.html in the download) links directly to all the source scripts that they mention. Great way to introduce the reader to the code. Joshua Stultshttps://www.blogger.com/profile/03506970399027046387noreply@blogger.comtag:blogger.com,1999:blog-5822805028291837738.post-49943403219626703682015-01-24T21:17:15.600-05:002015-01-24T21:17:15.600-05:00Well, I didn't read far enough in chapter 8, t...Well, I didn't read far enough in chapter 8, they actually do mention the improved Gauss transform method, and then far too quickly dismiss "iterative methods" from their subsequent comparisons. <br /><br />I think there are plenty of times when an approximate solution to the whole problem is more useful than an exact solution to a partial problem.Joshua Stultshttps://www.blogger.com/profile/03506970399027046387noreply@blogger.comtag:blogger.com,1999:blog-5822805028291837738.post-545614173815034792015-01-24T21:04:13.225-05:002015-01-24T21:04:13.225-05:00Here's what's missing from the book, itera...Here's what's missing from the book, iterative methods to avoid N^3 scaling of direct inversion for the linear system solution: <br /> - Improved Fast Gauss Transform <a href="http://www.umiacs.umd.edu/labs/cvl/pirl/vikas/Software/IFGT/IFGT_code.htm" rel="nofollow">code</a>, <a href="http://www.umiacs.umd.edu/labs/cvl/pirl/vikas/Software/IFGT/IFGT_user_manual.pdf" rel="nofollow">user's manual</a>, <a href="http://www.umiacs.umd.edu/labs/cvl/pirl/vikas/publications/IFGT_slides_lean.pdf" rel="nofollow">slides</a>, <a href="http://www.umiacs.umd.edu/labs/cvl/pirl/vikas/publications/raykar_learning_workshop_2007_slides.pdf" rel="nofollow">slides</a><br /> - <a href="http://stanford.edu/~rezab/nips2013workshop/accepted/preconditioned.pdf" rel="nofollow">Preconditioned Krylov Solvers for Kernel Regression</a><br /><br />The strategies are to get an approximate solution using an iterative method, and also to approximate the matrix-vector multiply (N or NlogN instead of N^2), of course preconditioning is useful for any method relying on Krylov subspace approaches. The interesting thing about the matrix-vector multiply approximation is that it can be done with <i>worse</i> accuracy as the solution progresses, further saving wall-time. <br /><br />Another acceleration approach is to fit on only a subset of the data or do a direct inversion on a reduced rank approximation of the matrix (this is covered in <a href="http://www.gaussianprocess.org/gpml/chapters/RW8.pdf" rel="nofollow">Chapter 8</a>):<br /> - <a href="http://jmlr.org/papers/volume6/quinonero-candela05a/quinonero-candela05a.pdf" rel="nofollow">A Unifying View of Sparse Approximate Gaussian Process Regression</a><br /><br />The really cool thing is that all of these acceleration approaches can, in concept, be combined. I haven't found a demonstration that actually does combine them all, so if you know of someone who has published on that please share a link! Joshua Stultshttps://www.blogger.com/profile/03506970399027046387noreply@blogger.comtag:blogger.com,1999:blog-5822805028291837738.post-27032977520436735622014-12-14T16:09:15.699-05:002014-12-14T16:09:15.699-05:00Just added a couple astro ones to the list: GMAT,...Just added a couple astro ones to <a href="http://www.variousconsequences.com/p/open-source-aeronautical-engineering.html" rel="nofollow">the list</a>: <a href="http://gmat.gsfc.nasa.gov/" rel="nofollow">GMAT</a>, <a href="http://odtbx.sourceforge.net/" rel="nofollow">ODTBX</a>Joshua Stultshttps://www.blogger.com/profile/03506970399027046387noreply@blogger.comtag:blogger.com,1999:blog-5822805028291837738.post-82945432181601043792014-12-04T17:44:41.425-05:002014-12-04T17:44:41.425-05:00Any future updates will be on this permanent page:...Any future updates will be on this permanent page: <br /> <a href="http://www.variousconsequences.com/p/open-source-aeronautical-engineering.html" rel="nofollow">Open Source Aeronautical Engineering Tools </a>Joshua Stultshttps://www.blogger.com/profile/03506970399027046387noreply@blogger.comtag:blogger.com,1999:blog-5822805028291837738.post-45183486417327733372014-11-18T21:58:41.962-05:002014-11-18T21:58:41.962-05:00From the New York Times:
This occasional column e...From the New York Times: <br />This occasional column explores topics covered in Science Times 25 years ago to see what has changed, and what has not.<br />The National Aero-Space Plane was to be a revolutionary advance beyond the space shuttle.<br />In his 1986 State of the Union address, President Ronald Reagan promised "a new Orient Express that could, by the end of the next decade, take off from Dulles Airport and accelerate up to 25 times the speed of sound, attaining low-earth orbit or flying to Tokyo within two hours."<br /><br />[...]<br /><br />Was the X-30 technologically feasible?<br /><br />"No, and it's still not," said Jess Sponable, a program manager in the tactical technology office at Darpa, the Defense Advanced Research Projects Agency.<br /><a href="http://www.nytimes.com/2014/10/21/science/25-years-ago-nasa-envisioned-its-own-orient-express.html" rel="nofollow">25 Years Ago, NASA Envisioned Its Own 'Orient Express'</a><br /><br />Joshua Stultshttps://www.blogger.com/profile/03506970399027046387noreply@blogger.com