My Thinkpad runs Windows 8.1 and Ubuntu 14.4 on dual boot. But since I tried Puppy Linux via a bootable USB stick my Ubuntu does not show up, Windows 8.1 just boots. Any solutions?  My BIOS is UEFI.
I installed Windows 7, which ate Ubuntu's boot file. When starting up the computer, it now goes straight to Windows, without giving me the option of booting Ubuntu.   How can I get Ubuntu back?
Where should collision detection logic be placed? I am developing a small 2D game engine. The characters have a paint method which currently does the following:   Calculate the new position of the character as per its speed, etc. Update the collision grid cell ** Draw the character at the new position   ** I have created a collision grid to reduce the number of intersection checks  Now the basic algorithm which I have thought for detecting collision is:   For Each Character     Check intersection with characters in surrounding 8 cells   I can simply place this code in the paint method. But here is the problem I anticipate.  Suppose two characters A and B lie in adjacent cells in the collision grid. Now as per the above algorithm in the iteration of character A it will detect that it has collided with B. In the iteration for character B it will detect that it has collided with A.  But I have an idea that when A detects that it has collided with B, it should inform B that it has collided with A. This would save lot of comparisons when there are more than 2 actors colliding. But I am not sure how to handle this. I think instead of every character checking for its collision, I should check for the collision inside the game loop.   Would this approach be correct? How have you handled this kind of problem? I thought of the collision grid thing myself. Are there any alternatives to collision grid logic? How to get the center line between two linestrings Where is the track of a ship when it is shipping always in the center of the   between the coasts of Great Britain and France?   I started with 2 linestrings and I created a lot of points on the linestring with a . After that I created a distance matrix with Raster/Analysis/Proximity in QGIS. Finally I created an aspect raster from the output raster.     Is the red line really the "center line" between these two linestrings?  Is there a more efficient way to do this? I have gcc 7.3.0 on Ubuntu 18.04. But I am working on a project where I need gcc less than version 6. When I tried to install gcc 5.4 using sudo apt install gcc-5.4, I got this error:  Reading package lists... Done Building dependency tree        Reading state information... Done E: Unable to locate package gcc-5.4 E: Couldn't find any package by glob 'gcc-5.4' E: Couldn't find any package by regex 'gcc-5.4'     What is the appropriate way to install gcc 5.4? Latest NVIDIA driver on Ubuntu 16.04 How to typeset a primed vector I write a vector with an arrow above the letter using \vec{p} and sometimes the vector needs to be primed using ' (or ^{\prime}, equivalently).  However, neither  \vec{p}'     nor  \vec{p'}     looks satisfactory (first option: prime dash overlaps with vector arrow, second option: arrow looks misplaced).  How would one write a primed vector? What is the command to truncate a SQL Server log file? I need to empty an LDF file before sending to a colleague.  How do I force SQL Server to truncate the log? Protect .NET code from reverse engineering? Obfuscation is one way, but it can't protect from breaking the piracy protection security of the application. How do I make sure that the application is not tampered with, and how do I make sure that the registration mechanism can't be reverse engineered?  Also it is possible to convert a C# application to native code, and  is too costly.  C# provides lot of features, and is the ideal language for my code, so writing the whole codebase again in C++ is out of the question.  Secure certificates can be easily removed from the signed assemblies in .NET. Get Age of a person in MySQL Feature request: Add pronouns to usercards? One of the questions people have raised about the new rules about pronouns is how users will know what pronouns are preferred.   We've had a trolling question which got  when the user included their preferred pronouns at the bottom of the question, and I agree that particularly on Stackoverflow (rather than sites like Interpersonal Skills or Workplace), this should be considered as 'noise' since it isn't the strict Q&amp;A this site is about. (The codez should work whatever your gender).  Currently, the suggested way of displaying your pronouns is to put it in your profile's 'About Me' section. However, this is suboptimal, since it requires opening a new page.  I suggest adding a 'preferred pronouns' field in the user profile, and displaying this on a user's usercard. There's currently a 'new contributor' label, so it could be similar to that, with she/her pronouns or whatever they choose.  In comments, it could be appended to the reputation score that currently gets shown when you hover over a name:   4,305 reputation, she/her pronouns  The default would be blank. No flair updates, no hover-in-comments update. If a user fills in this field in their profile, then it will show. Which spells or abilities are affected by things that care about targeting? Note: this is intended to be a canonical question about whether or not a spell or ability targets so there are multiple sub-questions.   Can Hexproof or Shroud save my creature from ? What about a  that was cast for it's Overload cost? Does shroud prevent me from using the Monstrosity ability of a creature, or from giving it more counters with Proliferate? Can I cast an Aura Enchantment on one of my creatures with Shroud, or an opponent's creature with Hexproof? Or can I use the Equip ability to attach an equipment to one of my creatures with Shroud? Will 's ability trigger when my opponent plays ? And will I have to sacrifice my  if my opponent casts ? Will Shroud or Hexproof prevent an opponent from choosing me with 's ability? Will Hexproof keep one of my creatures from being affected by ? If an Aura or Equipment is attached to a creature with Hexproof, does the Hexproof protect the attached permanent? Adding layers to GeoPackage using PyQGIS When water climbs up a piece of paper, where is the energy coming from? Take a glass of water and piece of toilet paper. If you keep the paper vertical, and touch the surface of the water with the tip of the paper, you can see the water being absorbed and climbing up the paper. This climbing up is intriguing me. Where is the energy coming from?  Supposedly, a lot of water molecules are moving up and gaining potential energy. This has to be balanced by something. I can think of a few possibilities, but I can't tell which one it is.   When the water molecules dilute into the paper, they are at a state of lower potential binding energy. Some molecular interaction (van der Waals?) is at lower energy when you have a water+paper solution, compared to a water-only solution. This compensates the gain in gravitational energy. The surface between the paper and the water is at lower pressure than the atmosphere. This causes the water to be pushed into the paper by the atmospheric pressure, up until the point that the column of water above the surface is heavy enough to counterbalance. The potential energy would be a result of work done by the atmosphere. Some water molecules climb up randomly and loose kinetic energy going up, and somehow get "stuck" up there. Something else? Where can we find frequently updated details about travel/entry restrictions due to Coronavirus (nCoV-19)? has been, have been , had been Why is the content of /run/resolvconf/interface/NetworkManager changed every time I reboot? System.Exception: Too many SOQL queries: 101 I am getting a Too many SOQL queries: 101 error on a trigger when I am trying to deploy another trigger.  I am posting the trigger which is causing the error.  trigger rollupAccountShowings on Account (before insert, before update) {    if (trigger.isinsert) {       for (Account a:Trigger.new){           a.No_of_Viewings__c = 0;        }    } else {      for (account a : [select                   id,                  (select id from pb__Showings__r)                  from account                   where id in:trigger.new LIMIT 1]) {           trigger.newMap.get(a.id).No_of_Viewings__c = a.pb__Showings__r.size();      } }   Can anyone correct me where I have gone wrong and suggest me the changes.  Thanks When there are X New Questions, the views don't update untill you refresh the page Let $f,g:X\to Y$ be maps of spaces such that $f\simeq g$. Is it true that the mapping cones $\operatorname{cone}(f)$ and $\operatorname{cone}(g)$ are homotopy equivalent?  Can we write down an explicit homotopy equivalence? It ought not to be too hard to get a map $\operatorname{cone}(f)\to \operatorname{cone}(g)$ from the existence of a homotopy $H:X\times I\to Y$, but I haven't been able to find a sensible candidate, despite trying for quite a while. Hidden features of Python I've got a circuit in the basement carrying a handful of outlets.  This circuit has no ground wire.  I want to add a couple of outlets and want them to be grounded.  I may even want gfci outlets on them in the future.  I have no reasonable way of getting a ground wire to the panel but I do have easy access to another circuit that does have a ground wire.  Is it acceptable to borrow or share a ground wire between circuits?  If not, why not?  Both circuits are 20A with 12 AWG wire.