Truncating a hash function's output should, in theory, not increase the likelihood of a collision more than you would expect based on the truncated output size. This makes sense when thinking about the the ideal hash function, a random function.  Since real-world hashes are not random functions, what properties of algorithms like sha2 make us comfortable with truncating, and what (popular) hashes exist out there that are known to have issues?
When I need to generate unique id's based on some information hashing is typical choice. However, sometimes that id needs to be of a particular size.  I've seen a lot of schemes (HMAC-MD5-96 in SSH, CGA in SeND for IPv6) that use a portion of a hash, so I'm thinking it might be alright to use it that way.    Which properties of a hash are preserved and which do not apply anymore?  Obviously, with less bits, the chance of collision goes up, but can I still rely on the partial hash for uniform character distribution?  What about the ?  I'm guessing that if a hash modifies the entire hash upon the smallest change to the input, that would imply that a portion of that hash would be equally well changed.  Am I thinking about this correctly?  Also, would these behaviors be different for different hashing algorithms?
Setting environment variables for latex and bibtex in .bashrc Possible Duplicate:          I recently started using TeX to write journal articles. I use TeX Live version 2009-10 on a laptop running Ubuntu 10.10 (64-bit). I edit and compile the tex files using vim and vim-latexsuite.   Currently for each journal article I have all associated tex, bib, eps, etc. files in individual folders. I would like to simplify my life a bit and have a dedicated folder containing a "master" bib file - And maybe another folder for my custom style files.   My problem is that can't figure out how I should define the PATH, and other environment variables in my .bashrc file to find the necessary support files (e.g., the .bib file). Which variables do I need to set? PATH? MANPATH? TEXINPUTS? BIBINPUTS? There are no compact minimal surfaces Customize feed on stack exchange android app How to know number of cores of a system in Linux? I wanted to find out how many cores my system has, so I searched the same question in Google. I got some commands such as the lscpu command. When I tried this command, it gave me the following result:  $ lscpu Architecture:          x86_64 CPU op-mode(s):        32-bit, 64-bit Byte Order:            Little Endian CPU(s):                4 On-line CPU(s) list:   0-3 Thread(s) per core:    1 Core(s) per socket:    4 Socket(s):             1 NUMA node(s):          1 Vendor ID:             GenuineIntel CPU family:            6 Model:                 23 Stepping:              10 CPU MHz:               1998.000 BogoMIPS:              5302.48 Virtualization:        VT-x L1d cache:             32K L1i cache:             32K L2 cache:              2048K NUMA node0 CPU(s):     0-3   In particular, this output shows:   CPU(s): 4 Core(s) per socket: 4 CPU family: 6   Which of those indicates cores of a Linux system?  Is there any other command to tell the number of cores, or am I assuming it is completely wrong? How can I install Ubuntu without removing Windows? I need my pre-installed version of Windows 7 (or any other version of Windows), how could I install Ubuntu without erasing it? How can I prove: if $p $ is prime and $n>1$, then $ p^{\frac1n} $ is irrational? With the following circuits as examples :    and    How will the current I know how much to flow? Would any other wave travel first in the circuit and then come back and say so much current should flow? Can I get US sales taxes refunded for electronics purchased while on vacation? In single-blind peer-review, can you reveal your identity without the editor's consent? In my field (chemistry), review is always done in a single blind process, i.e. the author does not know who the referees were, but the referees do know who the authors are. In ten years, I have never seen a referee breaching this anonymity, e.g. by signing their review, unless they got prior approval by the editor (in order to continue discuss things further with the authors, once the manuscript was accepted for publication).  So, it seemed logical to assume that in single blind peer-review, the reviewer should not disclose his identity without the editor's consent. Yet, some people have told me ( and ; also IRL a friend from human sciences) that they have seen people sign their reviews, or write emails to them after the review but before the paper is published.  So, in single-blind peer-review, can you reveal your identity without the editor's consent? Does it depends on the customs of each field, or is there a hard rule? (in which case, the few anecdotes I heard were outliers) The Monty Hall Problem - where does our intuition fail us? When I search for my address on Google Maps it cannot be found which means I can't order takeaway etc.  Is there a way of adding my address to Google Maps or even add a street address?  I want the address to be publicly available so others can search it. Show the post's comments on the "Suggested Edits" review interface Having recently reviewed a few suggested edits, I've found that not being able to see the comments on the post is hindering my understanding of the context of some edits.  In particular, there have been a few posts where someone has made a substantial edit to a question or answer which significantly alters its meaning. Typically I'd reject that as "too radical", since it can't be known that the new meaning of the post was what the original author intended.  However, in some cases it is clear from the comments that the original author is aware of the intended change, and as such the editor is not in fact misrepresenting the author's intentions. In these cases, it would have been useful to see the comments when making the review decision.  As an example, a common cause of this is when an inexperienced user is asked to clarify their question, and ends up writing a comment that would be better off as an edit to the question (due to length, excess code content, etc), presumably due to lack of awareness that the question can be edited. Often, other users will helpfully edit the question to include the information the OP put in the comment (see ,  and  for examples). In this situation, it is clear that the edit reflects the OP's intentions, but this information is only present in the comments which are not visible in the review interface.  Following is the suggested edit screen showing the suggested edit. It seems indentation is increased and one line is moved a few lines upwards and some empty lines added to increase readability. But it look like an invalid edit since changing the related line may cause alteration on the runtime. So not looks lie a valid edit. Better open the answer and examine it        Checking the Q&amp;A itself reveals that a talk had taken place between the OP and the answerer and revision done by the OP with the permission of the answerer. So it was indeed a valid edit.        In short: is there any particular reason comments are not displayed in the suggested edit review interface? I think it would add useful contextual information when making review decisions, and presumably this would be trivial to implement.  Note: this is not a dupe of , as it does not concern comments posted after the suggested edit. I was working on a Beamer presentation, and noticed that, if I open a group scope and use a \tiny, the font size will bet set, but there will be a large space between lines. However, if I issue a \par at the end of the paragraph, it works as intended:  \documentclass[t]{beamer} \newcommand{\shortlipsum} {Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Ut purus elit, vestibulum ut, placerat ac, adipiscing vitae, felis. Curabitur dictum gravida mauris. Nam arcu libero, nonummy eget, consectetuer id, vulputate a, magna. Donec vehicula augue euneque. Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas. Mauris ut leo. Cras viverra}  \begin{document} \begin{frame} \shortlipsum  {\tiny \shortlipsum\par   % &lt;--- removing this \par will break line spacing } \end{frame} \end{document}   Here's a comparison between not using and using \par:    Am I doing it the right way? Why is \par the right way? There's a story my grandpa use to tell me when I was younger, about the sole survivor of of an attack on a mining vessel in space. The man lives in space for months/years, ignored by the company he worked for and never rescued. Then when he thinks he is being rescued, it's actually another set of raiders who attack him and kidnap him.  He then wakes up in captivity in some sort of prison inside of an asteroid, and has a word tattooed on his forehead. My grandpa called him Ronin (that's what the tattoo on his forehead said) but I don't know what the character's real name is. Anyways, he learns that he has the ability to teleport after having a brush with death and decides to make his way back to Earth so that he can exact revenge on the mining company who abandoned him and left him floating to die.  Does anyone know what this story or book may be? My grandpa told it to me when I was little, he said that he got it from a book he use to love reading when he was younger. I'm assuming the book is very old (possibly pre 1940's as he was born in the 20s). I can't ask him as he is no longer alive. I'm also unsure as to whether or not all the details in the story he told me, are the same as in the original. How many String objects will be created when using a plus sign? Intellij shortcut for quick call hierarchy Is there a shortcut key to bring up the call hierarchy of a method inline with the code, in the quick menu format, rather than bringing up the call hierarchy panel? Looking for Anime with a prince faking being mentally handicapped hiding a giant mech suit wreaking havoc This is all I can remember.  There are four worlds whose people and technology were all swapped so humans ended up with high tech mech suits that they used to kill each other. There was a supposedly handicapped prince who faked being mentally handicapped and had a giant mech suit hidden underground that he eventually used to wreak havoc on earth.  The protagonist also had a suit and he saved the day. He was in love with a girl who was from another world and when he saved the day, all the people and technology from the different worlds were sent back to their original one causing the girl to leave him. She had colored hair and the final scene was her waking up somewhere with some children commenting on her hair.  There may or may not have been a reference to the protagonists scars in the shape of the constellation of orion on his body.  Any ideas? I've searched the internet for two years trying to find it. My PDO Statement doesn't work To all the 'sed' doctors out there:  How can you get 'sed' to extract a regular expression it has matched in a  line?   In other words words, I want just the string corresponding to the regular  expression with all the non-matching characters from the containing line stripped away.  I tried using the back-reference feature like below  regular expression to be isolated           gets `inserted`                here                     |                v    sed -n 's/.*\( \).*/\1/p    this works for some expressions like   sed -n 's/.*\(CONFIG_[a-zA-Z0-9_]*\).*/\1/p    which neatly extracts all macro names starting with 'CONFIG_ ....' ( found in some '*.h' file ) and prints them all out line by line             CONFIG_AT91_GPIO           CONFIG_DRIVER_AT91EMAC                    .                    .              CONFIG_USB_ATMEL           CONFIG_USB_OHCI_NEW                    .                  e.t.c.    BUT the above breaks down for something like    sed -n 's/.*\([0-9][0-9]*\).*/\1/p    this always returns single digits like                    7                  9                  .                  .                    6   rather than extracting a contiguous number field such as.                 8908078               89670890                    .                  .                    .                23019                     .                e.t.c.     P.S.: I would be grateful to feedback on how this is achieved in 'sed'.        I know how to do this with 'grep' and 'awk'       I would like to find out if my - albeit limited - understanding of        'sed' has holes in it and if there is way to do this in 'sed' which I       have simply overlooked. What are the uses of "using" in C#? User  answered the wonderful  question by mentioning the using keyword. Can you elaborate on that? What are the uses of using?