I have upgraded from Ubuntu 19.10 to 20.04, and now I have a problem with my graphics rendering (strange squares on background and font problems). I use the i915 driver. Graphics card: Skylake GT2 HD Graphics 520. I tried to reinstall GNOME shell and Xorg server. Nothing helped. Also Chrome browser breaks on most of pages.
I have recently upgraded Ubuntu 19.10 to latest LTS Ubuntu 20.04. After updating, I get serious artifacts on my screen. Every time I reboot (or log-in), my screen is fuzzy or scrambled (picture attached):     This is temporary. The fuzzy screen goes away when I change the background. But it reappears the moment I reboot or log back in.   I have Intel HD Graphics 520 (Skylake GT2).  The output of lspci -nn |grep -E 'VGA|Display' is:  00:02.0 VGA compatible controller [0300]: Intel Corporation Skylake GT2 [HD Graphics 520] [8086:1916] (rev 07)   Update:   On enabling Wayland in Ubuntu 20.04 and logging in to, these artifacts are however cured.   This is okay for now, but I am not sure about Wayland as I have not yet used it before.   Is there a way to correct the graphic issue with normal Ubuntu startup?
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So, to test highlighting here in the sandbox:  , you can use GitHub-flavor fenced code blocks in your posts, specifying the language after the opening fence: ```html While not hinted otherwise: &lt;html&gt;&lt;/html&gt; source &lt;b&gt;goes&lt;/b&gt; &quot;here&quot;. ```  ```js var a = 3; while (not (a &gt; 0)) {     alert(&quot;JavaScript code &lt;b&gt;goes&lt;/b&gt; here.&quot;); } ```   Or:  Create code blocks in any way (using the fence notation above, the four-space indent form, or using HTML &lt;pre&gt;&lt;code&gt; tags).  Save your post.  Use your browser's developer tools to edit the resulting HTML. To open developer tools, press F12, or ⌥⌘ I on Mac.  Find the &lt;pre&gt; element and add the attribute class=&quot;prettyprint&quot;, or change it into one of the valid syntax hints linked above, like class=&quot;lang-vb prettyprint&quot;.  Run the following in the location bar: javascript:prettyPrint(); or prettyPrint() in the console.     Answers that are considered annoying or obnoxious, or that cause breakage for users, will be deleted. This is . So, I'm working creating a lamp... yes, newbie here.  After modeling for a bit, I noticed that my point of origin was no longer the center of my object:    How to I reset an object origin point to the center of it's geometry? How do I prove that $m(TE)=\left|\det(T)\right|m(E)$? Let $m$ be the $n$-dimensional Lebesgue measure and $T$ be a linear operator on $\mathbb{R}^n$. Let $\Sigma$ be the sigma-algebra of Lebesgue measurable sets. How do prove that (1) $\forall E\in\Sigma, T(E)\in \Sigma$ and $m(T(E))=\left|\det(T)\right|m(E)|$? Since the $\sigma$-algebra of Lebesgue measurable sets is strictly larger than the borel algebra, I think it cannot be proven by showing that $T$ is continuous. How do I prove this formally? I have a script from UC Davis and every thing is proven precisely here, except for one lemma which is critical for rest proofs in the script. That is,  Define $\mathbb{B}=\big\{\prod_{i=1}^n [a_i,b_i) : a_i,b_i\in\mathbb{R}\big\}$. Let $T$ be a unitary operator on $\mathbb{R}^n$. Let $A\in \mathbb{B}$ and $\{A_k\}_{1≦k≦m}$ be a finite disjoint sequence such that $\bigcup_{1≦k≦m} A_k \subset T(A)$. Then $\sum_{1≦k≦m} m(A_k) ≦ m(A)$.  It's written in the script: &quot;This result is geometrically obvious, but a formal proof seems to require a fuller discussion of the volume function on elementary geometrical sets, which is included in the theory of valuation in convex geometry. We omit the details&quot; It's okay to me to go through full discussion of volume function if that is precise. If it cannot be proven another easier way(so I can prove it in a day), please recommend me a &quot;convex geometry&quot; text which explains this. Deleted comments are persisting in the global inbox I realise that there is other questions out there about the  (First open one I found is ), but this is marked .  I often get the below issue where it will notify me about comments on my  (in this case what appears to be the user re-writing after deleting their comment) that no longer exist.  Also, occasionally, I see comment snippets with text that doesn't match what is on the page when I view it.  Let me know if I should be trying to edit that one to remove the tag indicating that it has been fixed, and add the above as another answer. Inequality involving $\limsup$ and $\liminf$: $ \liminf(a_{n+1}/a_n) \le \liminf((a_n)^{(1/n)}) \le \limsup((a_n)^{(1/n)}) \le \limsup(a_{n+1}/a_n)$ How do I force a column-break in a two-column document? If you provide 0 as the dayValue in Date.setFullYear you get the last day of the previous month:  d = new Date(); d.setFullYear(2008, 11, 0); //  Sun Nov 30 2008   There is reference to this behaviour at . Is this a reliable cross-browser feature or should I look at alternative methods? New top bar quick reference guide / Where has the link to  gone? Since the new top bar has been rolled out - a number of different people, established and new users alike, have asked questions on where a specific link has disappeared to with the new top bar design. Where has the link to &lt;X&gt; gone? Ok guys, continuing my passage through edwards... here is the question... thanks for hints/solutions in advance:  Suppose $f(x,y,z)=0$ can be solved for each of the three variables $x,y,z$ as a differentiable function of the other two. Then prove that  $\displaystyle \frac{\partial x}{\partial y} \frac{\partial y}{\partial z} \frac{\partial z}{\partial x} = -1$  Verify this is the case for the ideal gas equation $pv =RT$ where (where $p,v,T$ are the three variables and $R$ is the constant). How do I stop Windows 10 from updating my graphics driver? Listing layers from .mxd file using ArcPy for ArcGIS Pro? Proving that $\lim_{k\to \infty}\frac{f(x_k)-f(y_k)}{x_k-y_k}=f'(c)$ where $\lim_{k\to \infty}x_k=\lim_{k\to \infty}y_k=c$ with $x_k<c<y_k$ Question.  Suppose that a function $f$ is defined on an interval $I$, $c$ is a point of $I$, and {$x_k$} and {$y_k$} are any two sequences in $I$ such that $\lim_{k\to \infty}x_k=\lim_{k\to \infty}y_k=c$ with $x_k&lt;c&lt;y_k$ for all $k$. Prove that, if $f'(c)$ exists, then $\lim_{k\to \infty}\frac{f(x_k)-f(y_k)}{x_k-y_k}=f'(c).$   My Attempt.  Let $\epsilon_k=\frac{1}{k}$ be given.  For $\epsilon_1=1,$ there exists $\delta_1&gt;0$ such that $x_1,y_1\in I, x_1,y_1\in N'(c;\delta_1)$ implies $\vert \frac{f(x_1)-f(y_1)}{x_1-y_1} -f'(c) \vert&lt;\epsilon_1.$  For $\epsilon_2=\frac{1}{2},$ there exists $0&lt;\delta_2&lt;$min$\{\vert x_1-c \vert,\vert y_1-c \vert,\epsilon_2\}$ such that $x_2,y_2\in I, x_2,y_2\in N'(c;\delta_2)$ implies $\vert \frac{f(x_2)-f(y_2)}{x_2-y_2} -f'(c) \vert&lt;\epsilon_2.$  Similarly, for $\epsilon_{k}=\frac{1}{k},$ there exists $0&lt;\delta_k&lt;$min$\{\vert x_{k-1}-c \vert,\vert y_{k-1}-c \vert,\epsilon_k\}$ such that $x_k,y_k\in I, x_k,y_k\in N'(c;\delta_k)$ implies $\vert \frac{f(x_k)-f(y_k)}{x_k-y_k} -f'(c) \vert&lt;\epsilon_k.$  Then by taking the limit to infinity, we obtain $\lim_{k\to \infty}\frac{f(x_k)-f(y_k)}{x_k-y_k}=f'(c).$   It really took me a lot of time to finish the proof and I need this to be checked by an expert:) Is the proof okay? Any response would be appreciated! Updating the repository isn't working When I run sudo apt-get update get this output:   sudo apt-get update E: Type '&lt;!DOCTYPE' is not known on line 1 in source list /etc/apt/sources.list.d/playonlinux.list E: The list of sources could not be read.   Also Ubuntu software Center is not opening. I read the following dev email  and when i read this part:  Note that this does not completely remove the ability for extensions (e.g. Dropbox) to add emblems programmatically by using the libnautilus-extension library, just the user-added emblems from the properties dialog/emblems sidebar.   There is ability to bring emblems programmatically. So, How can i use libnautilus-extension library to add some emblems like Dropbox does? Or is there any tweak tool for this? Agreement in "[Singular Noun] Is/Are [Plural Noun]"? The hidden flaw in "singular they"—what to do about reflexive pronouns? We have  to a question about gender-neutral pronouns, in which he points to the "singular they" and its long history of use in English. (Note that he also advises against using it.) Example:     If someone wants to watch TV tonight, they'll have to do the dishes.   This avoids having to say "he or she" in mixed-gender situations. Okay, fine. I'm not going to get my panties in a bunch if people want to talk this way.  But it occurrs to me that "singular they"—infelicitous at the best of times—really falls apart when extended into the realm of reflexive pronouns:     If someone wants to watch TV tonight, they'll have to do the dishes all by themselves. [?]   That feels very wrong. The only alternative, if one paints oneself into that corner, is to flip it back to singular:     If someone wants to watch TV tonight, they'll have to do the dishes all by themself. [???]   That feels worse.  If I'm to state this as a question, I guess I would put it thus: How can use of a "singular they" truly be reconciled? Is it really as much of a linguistic dead end as it feels to me? How to secure database passwords in PHP? "The train will leave" vs. "is going to leave" vs. "leaves" vs. "is leaving" How to know that your machine learning problem is hopeless? Imagine a standard machine-learning scenario:     You are confronted with a large multivariate dataset and you have a   pretty blurry understanding of it. What you need to do is to make   predictions about some variable based on what you have. As usual, you   clean the data, look at descriptive statistics, run some models,   cross-validate them etc., but after several attempts, going back and   forth and trying multiple models nothing seems to work and your   results are miserable. You can spend hours, days, or weeks on such a   problem...   The question is: when to stop? How do you know that your data actually is hopeless and all the fancy models wouldn't do you any more good than predicting the average outcome for all cases or some other trivial solution?  Of course, this is a forecastability issue, but as far as I know, it is hard to assess forecastability for multivariate data before trying something on it. Or am I wrong?   Disclaimer: this question was inspired by this one  that did not attract much attention. It would be nice to have detailed answer to such question for reference. How to set environment variable in systemd service? I have an  and I've created my own service. The configuration service at /etc/systemd/system/myservice.service looks like this:  [Unit] Description=My Daemon  [Service] ExecStart=/bin/myforegroundcmd  [Install] WantedBy=multi-user.target   Now I want to have an environment variable set for the /bin/myforegroundcmd. How do I do that?