I'm traveling to India from the US, I've a F1 visa in the US and I'm an Indian national. My flight is through YYZ (Toronto Pearson International Airport), a layover more than an hour there.  Do I need to get a transit visa?
I'm passing through Canada, on my way to somewhere else. I'm staying only a short time.   Is there a website, or some other way of find out out if I need a visa?
How to wait in a bash script for several subprocesses spawned from that script to finish and return exit code !=0 when any of the subprocesses ends with code !=0 ?  Simple script:  #!/bin/bash for i in `seq 0 9`; do   doCalculations $i &amp; done wait   The above script will wait for all 10 spawned subprocesses, but it will always give exit status 0 (see help wait). How can I modify this script so it will discover exit statuses of spawned subprocesses and return exit code 1 when any of subprocesses ends with code !=0?  Is there any better solution for that than collecting PIDs of the subprocesses, wait for them in order and sum exit statuses? What's a good SSH tunneling client for OS X? I've been using SSH Tunnel manager to easily set up and stop port tunneling over SSH to various servers at my company. That saved me the pain of opening up a new terminal window which will hang out there just for the sake of having a tunnel open.  This worked great (well , sort of) but SSH Tunnel Manager is a PowerPC application. With Lion, it is not supported any more.  What is a good replacement? What's the difference between using > and >> in shell? Why didn't Star Trek TOS have better medical equipment for Vulcans? In  when Ambassador Sarek became critically ill, why didn't they send him home or send for a Vulcan medical expert? Since they were hosting many prominent political figures from many races, it seems strange that they did not have much medical support for a race so common as Vulcans (who are part of the Federation). Finite $G$ with involutory automorphism $\alpha$ with no nontrivial fixed points. Proving properties of $\alpha$. The question at hand is:     Let G be a finite group and $\alpha$ an involutory automorphism of G, which doesn't fixate any element aside from the trivial one.    1) Prove that $ g \mapsto g^{-1}g^{\alpha} $ is an injection    2) Prove that $\alpha$ maps every element to its inverse    3) Prove that G is abelian    I think I've found 1).  I assume $ g_1^{-1}g_1^{\alpha} = g_2^{-1}g_2^{\alpha} $ and from this I get $ (g_2g_1^{-1})^\alpha = g_2g_1^{-1} $, so $g_2 = g_1$ (is this correct?)   For 2) I'm sort of stumped though, not sure how to start proving that, so any help please? Correlating filename with package Say, I'm given a filename like libasound.so.2. Is there a way to query the package manager to correlate the filename with its corresponding package?  I'm interested to get answers for any package manager, but my primary focus is on apt and yum. Ubuntu 14.04.5/16.04 and newer on AMD graphics I have 14.04.5/16.04 or newer and an AMD GPU. I'm not getting the performance I want, and some programs say they need things like OpenCL.  I've heard about fglrx, but if I try to install it on my machine, it breaks and I have no GUI.  Is there anything I can do to get my AMD card working to its full potential? Proof of the formula $1+x+x^2+x^3+ \cdots +x^n =\frac{x^{n+1}-1}{x-1}$ Show that the cardinality of $\mathbb N$ is the same as the cardinality of $\mathbb N \times \mathbb N$ Show that $| \mathbb N | = | \mathbb N \times \mathbb N |$, i.e., the cardinality  of $\mathbb N$ is the same as the cardinality of $\mathbb N \times \mathbb N$.   How do I show it using the Fundamental Theorem of Arithmetic and the Schröder–Bernstein Theorem? Consider the equation $$|2^x-3^y|=1$$ in the unknowns $x \in \mathbb{N}$ and $y \in \mathbb{N}$. Is it possible to prove that the only solutions are $(1,1)$, $(2,1)$ and $(3,2)$? UK visit visa: What documents prove genuine relationship with the visitor? In the UK immigration rules for visitor visa  it states if;      Funds, maintenance and accommodation provided by a third party      V 4.3 A visitor’s travel, maintenance and accommodation may be   provided by a third party where the decision maker is satisfied that   they:      (a) have a genuine professional or personal relationship with the   visitor;and      (b) are not, or will not be, in breach of UK immigration laws at the   time of decision or the visitor’s entry to the UK; and      (c) can and will provide support to the visitor for the intended   duration of their stay.   I'm a UK  citizen. I'm planning to invite my brother-in-law and another close friend to the UK. In my invitation letter, I have clearly mentioned that I'm going to provide them accommodation only. They have prove sufficient funds to support themselves. I have sent them an invitation letter along with a copy of my passport and tenant agreement.   What other documents do I need to provide to indicate that it is a genuine professional or personal relationship with the visitor? Ambiguity of “not.... because” You are not hired because you are qualified.   I think this means you are hired but it is not because you are qualified. But I think this can  also means you are not hired, and the reason for it is that you are qualified.   Does this ambiguity really exist or do I mistake anything? Connect two computers with SSH in a home LAN I have two ubuntu computer shared the same wifi and desire to reach another from one's terminal.  First create an user on the second computer named "Second" and hostname "Algorithms"    Then tried to reach it from the other with SSH,  but get error report as   $ ssh second@Algorithms   ssh: Could not resolve hostname algorithms: nodename nor servname provided, or not known   The solution I tried is based on   What's the problem with my experiment? Equal simple field extensions? I have a question about simple field extensions.  For a field $F$, if $[F(a):F]$ is odd, then why is $F(a)=F(a^2)$? Why do I need multiple sites for the same property in Google Webmaster Tools? In researching the best practice for adding sites to the Search Console, I've often seen it suggested to add separate properties for different versions of the same website. Even in  it states:     "Similarly, if your site has http:// and https:// versions, you should   add each as a separate site."   I've seen the same suggested for www/non-www. So if a site is accessible at all the variations of http/s and www/non-www we should have four properties.  But what if the site is only accessible at one variant? i.e. https and www are forced via htaccess, so only  can ever be accessed - should we still add all the variants?   In essence, the problem is that I don't know why Google wants us to do this, so I can't work out if it'll be ok just to have one instance. Is it possible for test error to be lower than training error Is it possible to have test error lower than training error?  I have a classification problem with 2000 samples, 500 of which are positives, 1500 are negatives. I split my data into 70% training data, 30% test data.  Run random forest with 200 estimators and cv=10. I did this several times and compared the recall and precision score and notice the scores for my test set is significantly better. Is this possible? Web colors: how to compensate for differences in monitors I am developing a PHP application in which I am in need to store values bigger than 1 million, but with the flexibility of having floating points. I know the traditional float and double. I am looking to store only up to two decimal points, and will only handle operations with numbers that have 2 decimals exclusively.  I have chosen my column type of double and unsigned, but whenever I store a row with a value bigger than one million, it gets truncated to 999999.99  Why is this? I am looking for the right datatype/solution. If you could point me in the right direction, I will appreciate it a lot!  Thank you for your time in advance!  Cheers. How to inset a face? I am trying to set up a Minecraft rig mouth that will have more controls and will be rounded, but I am having issues trying to figure out what this guy did here. First, he did what looked like a loop cut and slide, but instead of drawing a line it selected all the edges it passed through. He then cut to a new clip where the mouth was already set up like this.    The video is in 3 times speed but if you download a youtube plugin you can slow it down to 0.25 speed of the video and then if you do the spacebar trick you can slow it down so it shows 1 frame at a time and it is really slow.  if you want or need to see the video.  All I am asking is how can I create those 8 basic segments. Summarize the mathematical problem at the heart of breaking a Curve25519 public key It's pretty easy to generate a Curve25519 private key: generate 32 random bytes of data and then do:  e[0] &amp;= 248 e[31] &amp;= 127 e[31] |= 64   You can then generate a public key by doing  on the private key. For example, here's a random keypair I just generated:  public: e40ed268dff20db8497d0691421d00b086aad1efedcd5bd223d9eb6c0b85665f secret: e3c0e8b20ba7894882ddb37522dbe90867befcf9f31a5ce29c0d7997e0bd856d   The whole safety of public key encryption is that it is hard to take a public key and reverse the operation. Elliptic curve cryptography, as I understand it, relies on the fact that a  is hard to find. In particular, for a given large b and g, it is hard to find an integer k such that  $b^k = g$  How does that equation relate to Curve25519? Specifically, if I had a public key like the one above, how would I express, in math terms, the problem I need to solve to find the private key? How does it relate to the equation I see from time to time - $y^2 = x^3+486662x^2+x$, and the number $2^{255} - 19$?  I am guessing it is not as simple as "the private key is k and the public key is b and/or g" in the equation above. I'm also a little confused because the keys would appear to have roughly the same number of digits, which would seem to imply that there aren't many feasible values for k?