As pointed out in a comment to the question this was about gfx.xrender.enabled. The answer can be found in the marked dupe, but it is easy to miss in all the noise talking about ssh and the X11 protocol. Direct link to answer:  My problem started happening about a month ago. I'm currently on Firefox 89.0.1. Up until this point, Firefox ran just fine over ssh -X. I'm running it from an Ubuntu machine (server) to an Ubuntu VM (client) and a different Ubuntu machine (server) to Windows 10 (client), both showing the same symptoms. It's not my hardware setup or -X as all machines are wired to a local gigabit switch and other applications (including Thunderbird) run just fine. They are a little slower than if I was running them on their own desktop, but perfectly usable. After it happened, Firefox is just .... slow. I'm using it with --no-remote and the actual window for Firefox appears in under a second. It then hangs there for about 2 minutes until the tabs become usable. The output in my ssh shell reads: $ firefox --no-remote &amp; libGL error: No matching fbConfigs or visuals found libGL error: failed to load driver: swrast  (firefox:757486): GLib-GIO-CRITICAL **: 10:39:54.241: g_dbus_proxy_new: assertion 'G_IS_DBUS_CONNECTION (connection)' failed  (firefox:757486): GLib-GIO-CRITICAL **: 10:39:54.241: g_dbus_proxy_new: assertion 'G_IS_DBUS_CONNECTION (connection)' failed  (firefox:757486): GLib-GIO-CRITICAL **: 10:39:54.241: g_dbus_proxy_new: assertion 'G_IS_DBUS_CONNECTION (connection)' failed [GFX1-]: Failed GL context creation for WebRender: 0 [GFX1-]: FEATURE_FAILURE_WEBRENDER_INITIALIZE_UNSPECIFIED [GFX1-]: Failed to connect WebRenderBridgeChild. [GFX1-]: Fallback WR to SW-WR libGL error: No matching fbConfigs or visuals found libGL error: failed to load driver: swrast libGL error: No matching fbConfigs or visuals found libGL error: failed to load driver: swrast  but that doesn't look too different to what I had before. Can anyone please suggest anything that might speed it up? I'm not really looking for answers telling me that ssh -X is slow (it is, but it's acceptable to me on all other applications) or things to do with compression or cypher suites. My link is fine, except for Firefox.
I try to launch Firefox over SSH, using  ssh -X user@hostname   and then  firefox -no-remote   but it's very very slow.  How can I fix this? Is it a connection problem?
I found this problem on a well-known problem solving website. It is apparently from Ramanujan.     With   $$\LARGE{a = \frac{1}{1 + \frac{e^{-2\pi}}{1 + \frac{e^{-4\pi}}{1 + \ddots}}}},$$   what is $a$?   The basic methods I know for questions of this type were not helpful to me.  I do not require a full solution, but feel free to post one if you would like. Hints or lecture notes on how to solve problems of this nature would be appreciated.   Keep in mind that I am at an undergraduate level in mathematics. It is commonly stated that there are four fundamental forces, or interactions, in nature. It is natural to consider which of those is responsible for the normal force we meet in elementary physics. What is the nature of the force exerted on a body by the floor on which it rests?  Of the four forces, the only one that seems relevant is the electromagnetic force, and I always assumed the repelling force in question is ultimately the EM one. The Wikipedia article on  seems to agree:     Molecular and quantum physics show that the electromagnetic force is the fundamental interaction responsible for contact forces.    An alternative explanation is that the force results from Pauli's Exclusion Principle; however, reasonable as it may seem, it doesn't seem to answer the question of what force is actually at play here. The exclusion principle isn't a force, or at least it's not normally described as such.  I've recently come across a rather forcefully presented argument that states that the normal force is a macroscopic force that is not directly reducible to the EM force, or to any of the other forces; rather, it does indeed result from Pauli's Exclusion Principle by way of interaction of electron wave functions. The argument further claims that attempts to correct the Wikipedia article have met with the usual "source needed" objections, and that this topic is either misunderstood by or poorly covered in the standard texts.  (The argument can be found ).   Which way is it? If I want to use objects as the keys for a Dictionary, what methods will I need to override to make them compare in a specific way?  Say I have a a class which has properties:  class Foo {     public string Name { get; set; }     public int FooID { get; set; }      // elided }    And I want to create a:  Dictionary&lt;Foo, List&lt;Stuff&gt;&gt;   I want Foo objects with the same FooID to be considered the same group.  Which methods will I need to override in the Foo class?  To summarize: I want to categorize Stuff objects into lists, grouped by Foo objects. Stuff objects will have a FooID to link them to their category. MySQL Syntax error message "Operand should contain 1 column(s)" I tried running the following statement:  INSERT INTO VOUCHER (VOUCHER_NUMBER, BOOK_ID, DENOMINATION) SELECT (a.number, b.ID, b.DENOMINATION)  FROM temp_cheques a, BOOK b WHERE a.number BETWEEN b.START_NUMBER AND b.START_NUMBER+b.UNITS-1;   which, as I understand it, should insert into VOUCHER each record from temp_cheques with the ID and DENOMINATION fields corresponding to entries in the BOOK table (temp_cheques comes from a database backup, which I'm trying to recreate in a different format). However, when I run it, I get an error:  Error: Operand should contain 1 column(s) SQLState:  21000 ErrorCode: 1241   I'm running this in SQuirrel and have not had issues with any other queries. Is there something wrong with the syntax of my query?  EDIT:  The structure of BOOK is:  ID  int(11) START_NUMBER    int(11) UNITS   int(11) DENOMINATION    double(5,2)   The structure of temp_cheques is:  ID  int(11) number  varchar(20) Can't remove URL on ALL profiles There is a bug removing URL from the profile.   Website link has some URL. Remove URL (empty field). "Save and copy changes to all Stack Exchange communities" button pressed.   Observed result: Empty URL only on the current SE site.    Expected result: Empty URL on all Stack Exchange sites. Evaluating logistic regression and interpretation of Hosmer-Lemeshow Goodness of Fit As we all know, there are 2 methods to evaluate the logistic regression model and they are testing very different things  Predictive power: Get a statistic that measures how well you can predict the dependent variable based on the independent variables. The well-known Pseudo R^2 are McFadden (1974) and Cox and Snell (1989).  Goodness-of-fit statistics The test is telling whether you could do even better by making the model more complicated, which is actually testing whether there are any non-linearities or interactions that you have missed.   I implemented both tests on my model, which added quadratic and interaction already:     &gt;summary(spec_q2)      Call:     glm(formula = result ~ Top + Right + Left + Bottom + I(Top^2) +       I(Left^2) + I(Bottom^2) + Top:Right + Top:Bottom + Right:Left,       family = binomial())       Coefficients:                  Estimate Std. Error z value Pr(&gt;|z|)         (Intercept)  0.955431   8.838584   0.108   0.9139         Top          0.311891   0.189793   1.643   0.1003         Right       -1.015460   0.502736  -2.020   0.0434 *       Left        -0.962143   0.431534  -2.230   0.0258 *       Bottom       0.198631   0.157242   1.263   0.2065         I(Top^2)    -0.003213   0.002114  -1.520   0.1285         I(Left^2)   -0.054258   0.008768  -6.188 6.09e-10 ***     I(Bottom^2)  0.003725   0.001782   2.091   0.0366 *       Top:Right    0.012290   0.007540   1.630   0.1031         Top:Bottom   0.004536   0.002880   1.575   0.1153         Right:Left  -0.044283   0.015983  -2.771   0.0056 **      ---     Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1     (Dispersion parameter for binomial family taken to be 1)     Null deviance: 3350.3  on 2799  degrees of freedom     Residual deviance: 1984.6  on 2789  degrees of freedom     AIC: 2006.6  and the predicted power is as below, the MaFadden is 0.4004, and the value between 0.2~0.4 should be taken to present very good fit of the model(Louviere et al (2000), Domenich and McFadden (1975))                                                :  &gt; PseudoR2(spec_q2)     McFadden     Adj.McFadden        Cox.Snell       Nagelkerke McKelvey.Zavoina           Effron            Count        Adj.Count     0.4076315        0.4004680        0.3859918        0.5531859        0.6144487        0.4616466        0.8489286        0.4712500           AIC    Corrected.AIC  2006.6179010     2006.7125925   and the goodness-of-fit statistics:  &gt; hoslem.test(result,phat,g=8)       Hosmer and Lemeshow goodness of fit (GOF) test    data:  result, phat   X-squared = 2800, df = 6, p-value &lt; 2.2e-16  As my understanding, GOF is actually testing the following null and alternative hypothesis:   H0: The models does not need interaction and non-linearity   H1: The models needs interaction and non-linearity  Since my models added interaction, non-linearity already and the p-value shows H0 should be rejected, so I came to the conclusion that my model needs interaction, non-linearity indeed. Hope my interpretation is correct and thanks for any advise in advance, thanks. How bug prioritization works in agile projects vs non agile When reporting a defect, we are setting the priority and severity of the defect. How this works with agile development? Is there any specific way ?  How bug prioritization works in agile projects vs non agile.?  Is there any other way of measuring the priority of a bug in agile projects? I have this run.sh file, and I've create a symbolic link into my desktop.   When I double-click on it the file the following dialog appearsr    And I have to click on "run" each time. How can I create a link that runs by default? While I was reading the book Exploratory examples for real analysis, I came across this:     to show that : $$\lim_{x\rightarrow x_o}\frac{1}{h(x)} = \frac{1}{\lim_{x\rightarrow x_o}{h(x)}} = \frac{1}{M}$$      Discussion:Let $\epsilon \gt 0$.we want to find $\delta \gt 0$ such that       if  $0 \lt |x-x_0| \lt \delta $,then $\Big|\frac{1}{h(x)}-\frac{1}{M}\Big|\lt \epsilon$.      In order to get expression involving $|h(x)-M|$,we first find the common denominator:        $\Big|\frac{1}{h(x)}-\frac{1}{M}\Big|=\Big|\frac{M-h(x)}{M~h(x)}\Big|$      $~=\Big|\frac{h(x)-M}{|M|~|h(x)|}\Big|$.      As we have to deal with variable term $|h(x)|$ in denominator.We can construct bound .Let $\epsilon =\frac{|M|}{2}$ ,since lim$_{x\to x_o}h(x)=M$,there exists $\delta_1\gt 0~~$ s.t.       if $0 \lt |x-x_0| \lt \delta_1 $,then $|h(x)-{M}|\lt \frac{|M|}{2}$.      As you study steps below,identify that step where $h(x)\neq 0$ for all $0 \lt |x-x_0| \lt \delta_1 $ plays a critical role:      $|M|=|M-h(x)+h(x)|$      $~~~~~~\leq |M-h(x)|+|h(x)|$      $~~~~~~= |h(x)-M|+|h(x)|$      $~~~~~~\lt \frac{M}{2}+|h(x)| \implies$      $\frac{|M|}{2} \lt |h(x)| \implies$      $\frac{1}{h(x)}\lt \frac{2}{|M|}$,where $0 \lt |x-x_0| \lt \delta_1 $.      Now that we've bound for $1/h(x)$,we can apply the definition to term $|h(x)-M|$.      Since     lim$_{x\rightarrow x_o}h(x)=M$,we can find $\delta_2 \gt 0$ such that,       $~~~~~~~~~~~~~~~~~~~~~~~~~~~~$if  $0 \lt |x-x_0| \lt \delta_2$, then $|h(x)-M|\lt \frac{|M|^2 \epsilon }{2}$   The thing I can't understand is for what purpose did the author work with such complicated expression involving $\epsilon $ in the end of the discussion? Robot arm move a box How can I check if the editor that is currently being used is Gutenberg in a WordPress plugin?  I need this because Gutenberg lacks post_submitbox_misc_actions, so I need a fallback which will only be used if the current editor is Gutenberg. Did Dolores Umbridge Have Any Association with Voldemort (or Death Eaters) before His Return? Since I want to protect my ssh connections, I set some global cipher suite options to restrict set of used algorithms. But recently I've encountered a server which doesn't support some of those algorithms. So, I need to selectively enable deprecated algorithms for a specific host record in client (my system) configuration.  I found out that the options override is not working as I expected. Let's take a minimal (not-)working example for the github:  HostKeyAlgorithms ssh-ed25519-cert-v01@openssh.com,ssh-ed25519,ecdsa-sha2-nistp521-cert-v01@openssh.com,ecdsa-sha2-nistp521,ecdsa-sha2-nistp256  Host github     HostKeyAlgorithms ssh-rsa     Hostname        github.com     Port            22     User            git     PubkeyAuthentication yes     IdentityFile    ~/.ssh/some-filename-here   Having that, I receive the following error (HostKeyAlgorithms is not overriden at all):  debug1: /home/username/.ssh/config line 14: Applying options for github &lt;...&gt; debug2: kex_parse_kexinit: ssh-ed25519-cert-v01@openssh.com,ssh-ed25519,ecdsa-sha2-nistp521-cert-v01@openssh.com,ecdsa-sha2-nistp521,ecdsa-sha2-nistp256 &lt;...&gt; Unable to negotiate with 192.30.252.130: no matching host key type found. Their offer: ssh-dss,ssh-rsa   It is similarly not working for the global PubkeyAuthentication no options with an override in a host configuration.  Also, the match doesn't help either:  match host github     HostKeyAlgorithms ssh-rsa   So, is there a way to selectively redefine those options?  NOTE: I'm using the openssh-7.1_p2-r1 on gentoo. Am I technically allowed to look up cards during a Magic tournament match? Am I allowed to look up a card during a game, if it's being played with serious Rules Enforcement? Either to read the full card from the Gatherer, or to try to find the exact card I'm vaguely thinking of.  Two possible scenarios:   An opponent has revealed a card previously, and I want to remember the exact details. (Something like the exact wording of a sorcery, mana cost, keywords on a creature, subtypes, etc. etc.) I have a "name a card and remove it from the opponent's deck" type card, and I want to, say, ask google for "Blue Gearhulk" to remember that it's that that one is called "Torrential Gearhulk".   Obviously, in casual or semi-casual games neither of these are a problem. Any reasonable opponent will just re-reveal the known card (assuming it IS still guaranteed to be known) or will accept "I name the Blue Gearhulk".  Also obviously, it seems unlikely that I (or anyone else) would get to the stage of playing at the REL without knowing the cards too thoroughly for this to be relevant.  But in principle... is it permitted? Or not? (and if not, is there a good reason, or just "we decided 'No'"?) Can anyone explain to me why I would want to use IList over List in C#?  Related question: I am trying to think of a non-colloquial word or phrase that means "practice what you preach." I would appreciate any suggestions. Thank you! Egyptian fractions with prime power denominators summing to 1? Inspired by        Can we solve the equation $$1=\frac{1}{a_1}+\frac{1}{a_2}+\frac{1}{a_3}+\cdots +\frac{1}{a_n}$$ where $a_1,a_2,a_3,\cdots ,a_n$ are distinct prime powers (primes are allowed) ?   I tried a modified greedy-algorithm with different starting vectors and brute force with $6$ entris with limit $200$, but did not find a representation. I remember that a couple of years ago a friend showed me and some other people the following expression:  $$\lim_{n\to \infty}\frac{1^n+2^n+\cdots+(n-1)^n}{n^n}.$$  As shown below, I can prove that this limit exists by the monotone convergence theorem. I also remember that my friend gave a very dubious "proof" that the value of the limit is $\frac{1}{e-1}$. I cannot remember the details of the proof, but I am fairly certain that it made the common error of treating $n$ as a variable in some places at some times and as a constant in other places at other times. Nevertheless, numerical analysis suggests that the value my friend gave was correct, even if his methods were flawed. My question is then:  What is the value of this limit and how do we prove it rigorously?  (Also, for bonus points, What might my friend's original proof have been and what exactly was his error, if any?)  I give my convergence proof below in two parts. In both parts, I define the sequence $a_n$ by $a_n=\frac{1^n+2^n+\cdots+(n-1)^n}{n^n}$ for all integers $n\ge 2$. First, I prove that $a_n$ is bounded above by $1$. Second, I prove that $a_n$ is increasing.   (1) The sequence $a_n$ satisfies $a_n&lt;1$ for all $n\ge 2$.  Note that $a_n&lt;1$ is equivalent to $1^n+2^n+\cdots+(n-1)^n&lt;n^n$. I prove this second statement by induction. Observe that $1^2=1&lt;4=2^2$. Now suppose that $1^n+2^n+\cdots+(n-1)^n&lt;n^n$ for some integer $n\ge 2$. Then  $$1^{n+1}+2^{n+1}+\cdots+(n-1)^{n+1}+n^{n+1}\le(n-1)(1^n+2^n+\cdots+(n-1)^n)+n^{n+1}&lt;(n-1)n^n+n^{n+1}&lt;(n+1)n^n+n^{n+1}\le n^{n+1}+(n+1)n^n+\binom{n+1}{2}n^{n-1}+\cdots+1=(n+1)^{n+1}.$$  (2) The sequence $a_n$ is increasing for all $n\ge 2$.  We must first prove the following preliminary proposition. (I'm not sure if "lemma" is appropriate for this.)  (2a) For all integers $n\ge 2$ and $2\le k\le n$, $\left(\frac{k-1}{k}\right)^n\le\left(\frac{k}{k+1}\right)^{n+1}$.  We observe that $k^2-1\le kn$, so upon division by $k(k^2-1)$, we get $\frac{1}{k}\le\frac{n}{k^2-1}$. By , we may find:  $$\frac{k+1}{k}\le 1+\frac{n}{k^2-1}\le\left(1+\frac{1}{k^2-1}\right)^n=\left(\frac{k^2}{k^2-1}\right)^n.$$  A little multiplication and we arrive at $\left(\frac{k-1}{k}\right)^n\le\left(\frac{k}{k+1}\right)^{n+1}$.  We may now first apply this to see that $\left(\frac{n-1}{n}\right)^n\le\left(\frac{n}{n+1}\right)^{n+1}$. Then we suppose that for some integer $2\le k\le n$, we have $\left(\frac{k}{n}\right)^n\le\left(\frac{k+1}{n+1}\right)^{n+1}$. Then:  $$\left(\frac{k-1}{n}\right)^n=\left(\frac{k}{n}\right)^n\left(\frac{k-1}{k}\right)^n\le\left(\frac{k+1}{n+1}\right)^{n+1}\left(\frac{k}{k+1}\right)^{n+1}=\left(\frac{k}{n+1}\right)^{n+1}.$$  By backwards (finite) induction from $n$, we have that $\left(\frac{k}{n}\right)^n\le\left(\frac{k+1}{n+1}\right)^{n+1}$ for all integers $1\le k\le n$, so:  $$a_n=\left(\frac{1}{n}\right)^n+\left(\frac{2}{n}\right)^n+\cdots+\left(\frac{n-1}{n}\right)^n\le\left(\frac{2}{n+1}\right)^{n+1}+\left(\frac{3}{n+1}\right)^{n+1}+\cdots+\left(\frac{n}{n+1}\right)^{n+1}&lt;\left(\frac{1}{n+1}\right)^{n+1}+\left(\frac{2}{n+1}\right)^{n+1}+\left(\frac{3}{n+1}\right)^{n+1}+\cdots+\left(\frac{n}{n+1}\right)^{n+1}=a_{n+1}.$$  (In fact, this proves that $a_n$ is strictly increasing.) By the monotone convergence theorem, $a_n$ converges.  I should note that I am not especially well-practiced in proving these sorts of inequalities, so I may have given a significantly more complicated proof than necessary. If this is the case, feel free to explain in a comment or in your answer. I'd love to get a better grip on these inequalities in addition to finding out what the limit is.  Thanks! Is the null set a subset of every set? Ever since day one of of my Mathematical Logic course, this fact has really bothered me. I cannot wrap my head around how an empty set is a subset of every possible set. Could someone kindly explain how this is true? Any help is appreciated! Rest mass of the photon Why is the rest mass of the photon is taken to be zero?  If rest mass of the photon is non zero, then it leads to infinite energy of the photon (by $E=mc^2$ equation) and there is a violation of conservation of energy. Is this a reason?  Also, is there any thing called the relativistic mass of the photon?