Product of 2 positive definite matrix
Is the product of symmetric positive semidefinite matrices positive definite?
Mirror modifier. Mirrored half is not aligned, but rotated I was working on my character's hand when I realized half of the body was suddenly deleted. I am trying to recreate the other half, but it just won't mirror properly in the center. I tried moving the origin to the 3D cursor while it was completely centered, but the mirror modifier is still applied at an angle. Is there a way to show statistic info? Is there a way to get Statistic info in Blender? Or heads up display? Like when I select a group of vertices, I need a way to know how many vertices are selected and How many polygons "or triangles my scene has. How to select the most recent set of dated records from a mysql table I am storing the response to various rpc calls in a mysql table with the following fields:  Table: rpc_responses  timestamp   (date) method      (varchar) id          (varchar) response    (mediumtext)  PRIMARY KEY(timestamp,method,id)   What is the best method of selecting the most recent responses for all existing combinations of method and id?   For each date there can only be one response for a given method/id. Not all call combinations are necessarily present for a given date. There are dozens of methods, thousands of ids and at least 365 different dates    Sample data:  timestamp  method  id response 2009-01-10 getThud 16 "....." 2009-01-10 getFoo  12 "....." 2009-01-10 getBar  12 "....." 2009-01-11 getFoo  12 "....." 2009-01-11 getBar  16 "....."   Desired result:  2009-01-10 getThud 16 "....." 2009-01-10 getBar 12 "....." 2009-01-11 getFoo 12 "....." 2009-01-11 getBar 16 "....."   (I don't think  is the same question - it won't give me the most recent response) Can I have my iPhone play sound for MacBook? Say I am playing a video on my MacBook Pro, and I don't want to distract others with the sound. The problem is, I don't have a 3.5 mm Headphone or AirPods at my hand, but I have an iPhone 8 Plus and its EarPods with Lightning Connector. Can I play the sound from the video playing on macOS with the iPhone, preferably without connecting the iPhone to the Mac so that I can plug in the EarPods to the iPhone's socket?  This is basically the reverse of How do I create a D&D character correctly as a total newbie? Corrupt MXD Causes? Do mankind and manmade activities/constructions have any effect on the rotation of the Earth? ArcGIS Python Tool - Importing Custom Script Into ToolValidator Class Preamble: I know that 'give a reason when downvoting' is a very common request, and I assure you that I have read these posts and the discussions in them and my request is very different. This isn't about encouraging people to comment and is more about gathering metrics.  I'd like to see a feature whereby people who are downvoted get some better feedback on why they were downvoted, especially given that people rarely leave comments in practice.  So my suggestion is that when user clicks on the downvote, they are prompted to pick from a short list (No more than 5) of common reasons. It would be a popup that replaces the existing "Please consider adding a comment" box.  The user receiving the downvote would see how many people downvoted them for each reason, but not who did it. It would significantly address the issue of people being too lazy to comment or not wanting to comment (for fear of retaliation or any other reason) while helping to ensure the user gets useful feedback.  Perhaps the downvote could also be weighted based on whether or not a reason is picked.  For questions the list might look something like:   Not a question Not relevant to the subject area Trivial question with no research effort Poorly asked question Other   And for answers, this might be:   Nonconstructive or not an answer Incorrect or dangerous answer Poor explanation Doesn't answer the original question Other How do I concatenate JavaScript files into one file? Tiny white very hard cell bug! Please help to identify! I found these bugs walking on the floor/ wall and on my laptop.  And unfortunately I think they could be in my bed, too, since I bring my laptop to bed sometimes.   I live in a big city in the Netherlands without pets. My house has humidity issues.  I have noticed that the bugs are very tough to exterminate; meaning that when trying to squeeze them it really needs a lot of effort for their size. Their size is about 1 - 2 mm and their color is whitish.    Please note that my lightbulb is having a yellow color.so it makes it look darker than normal. It's more white than looks in the picture          This is a pic of it walking on my screen... Proving $\arg(zw)=\arg(z)+\arg(w)$ When is it appropriate to use a hyphen? How to ignore deprecation warnings in Python "Failed to create user" due to regular expression error I'm running Ubuntu 12.10 desktop 32 bit. Currently I have only a user, type administrator. I'd like to create another administrator user but I keep getting the following error:  Failed to create user GDBus.Error:org.freedesktop.Accounts.Error.Failed: running '/usr/sbin/adduser' failed: /usr/sbin/adduser returned an error (1): adduser: Please enter a username matching the regular expression configured via the NAME_REGEX[_SYSTEM] configuration variable.  Use the `--force-badname' option to relax this check or reconfigure NAME_REGEX.  Any suggestion is appreciated. Yes, I'm a moron, and I tried to manually install a higher point release of python 2.7.16 to /usr/bin/  (i did ./configure --prefix=/usr) on my Ubuntu 16.04 machine. It seems to work fine EXCEPT for packages that depended on python, like apt-listchanges, which fails with messages like ImportError: No module named apt_pkg  there's no make uninstall available, I've tried manually removing files, and still when I try apt --reinstall install python, Nothing gets overwritten and the python executable still gives the new 2.7.16 version...   Any idea how to get the official repository version back?? How can I specify a long list of math operators? The preambles of my LaTeX documents often include many many lines of \DeclareMathOperator instructions, e.g.  \DeclareMathOperator{\Rep}{Rep} \DeclareMathOperator{\Tet}{Tet} \DeclareMathOperator{\Maps}{Maps} \DeclareMathOperator{\Diff}{Diff}   Is there a nice way to map some macro over a list, so I could do this more concisely, and with less copying and pasting when I add a new math operator? Why do I keep getting told I posted less than 15 characters when I posted more than 15? I tried to post the following comment and it claims it was less than 15 when it was more.  Based on Tim's comment and testing I believe it would not let me post because with @Shadow removed it is less than 15. However, the characters left message indicates I have passed the 15 character minimum thus it is wrong.  This is the bug I'm reporting:  The characters remaining message and the characters left message do not take into account striping out @name prefixes. Blender saves a new file every time When I click save or hit Command + S what appears to be a new version of the document is created. So if I save 2 times, I get 2 documents, filename.blend1 and filename.blend2.  What exactly are these files and why is Blender creating them? Namespaces and Operator Overloading in C++ When authoring a library in a particular namespace, it's often convenient to provide overloaded operators for the classes in that namespace.  It seems (at least with g++) that the overloaded operators can be implemented either in the library's namespace:  namespace Lib { class A { };  A operator+(const A&amp;, const A&amp;); } // namespace Lib   or the global namespace  namespace Lib { class A { }; } // namespace Lib  Lib::A operator+(const Lib::A&amp;, const Lib::A&amp;);   From my testing, they both seem to work fine.  Is there any practical difference between these two options?  Is either approach better?