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  • ISP issue browsing "sonos.com" - need to diagnose and prove [closed]

    - by john
    I am unable to browse to a website "sonos.com" with my ISP (virgin). I have ruled out browsers, PCs, macs, routers, wifi, etc. Other ISPs (even other virgin connections in different areas!) supply this site no problem. I am 99% convinced there is a DNS issue lurking here. There is something fishy about the DNS for the site : What I notice is that online DNS sites tell me the right IP address for "sonos.com", but not for "www.sonos.com". Anyway when I type "sonos.com" the browser (any/all of the 4 I tried) fail to display the page. Firefox gives a "connection was reset" error. If I browse to sonos.com using the IP address it works OK. Browsing to www.sonos.com or sonos.com works fine with other ISPs of course. Questions: 1 Does anyone have any idea what might be going on here? 2 Any suggestions as to tools/monitors to help investigate/prove what is going on I can then take this up with virgin and/or sonos. Thanks

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  • A good example project to 'prove' my skills [closed]

    - by David Archer
    I've been a commercial programmer for about 3 years now but all of my commercial work is based upon PHP (with Cake PHP, Wordpress and Wildfire) and ASP.Net (on C#, including MVC 3, Umbraco and Kentico) as well as plenty of HTML/CSS/jQuery examples to show. A future employer has asked me to show my Ruby on Rails potential. I've done Ruby on Rails before for fun, but nothing worthy of commercial showing. What I'd like to know, from a group of programmers, is what would be a good 'portfolio demo' piece for you? What have you seen in the past that impressed you? What are you looking for? For Ruby lead developers specifically, what sort of things are you looking to see in the code? Cheers!

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  • Need an idea for an iOS project for a trainee to prove his skills

    - by Umair Khan Jadoon
    I am teaching iOS development to a trainee who has recently joined our startup. He already has strong background and experience in .net. At first phase, he will learn the following things: Basics of Objective C. Views and View Controllers(Navigation, Table, Tabs), gester recognizers, table views, segues etc. Protocols, gesters, delegates. Blocks and multithreading. Now, I have to give him some kind of homework assignment or project to get his skills to action and to know what he has learnt. Any ideas?

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  • Unit testing to prove balanced tree

    - by Darrel Hoffman
    I've just built a self-balancing tree (red-black) in Java (language should be irrelevant for this question though), and I'm trying to come up with a good means of testing that it's properly balanced. I've tested all the basic tree operations, but I can't think of a way to test that it is indeed well and truly balanced. I've tried inserting a large dictionary of words, both pre-sorted and un-sorted. With a balanced tree, those should take roughly the same amount of time, but an unbalanced tree would take significantly longer on the already-sorted list. But I don't know how to go about testing for that in any reasonable, reproducible way. (I've tried doing millisecond tests on these, but there's no noticeable difference - probably because my source data is too small.) Is there a better way to be sure that the tree is really balanced? Say, by looking at the tree after it's created and seeing how deep it goes? (That is, without modifying the tree itself by adding a depth field to each node, which is just wasteful if you don't need it for anything other than testing.)

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  • Prove this Tautology (No Truth Tables)

    - by FSM
    This is for homework for my Discrete Math class. I understand how to prove tautologies with a truth table. I'm having trouble figuring out how to do it without though. I found this example in our text, but the solution is not provided. I was hoping someone could answer it as best they could so I could apply it to my other questions. Thanks! ! = not/invert ^ = and V = or - = if then [!P ^ (P V Q) ] - Q I also am completely lost for this question (I fear I'll be tested on something of this difficulty) [ (P - Q) ^ (Q - R) ] - (P - R) Thanks for the help all!

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  • Does this prove a network bandwidth bottleneck?

    - by Yuji Tomita
    I've incorrectly assumed that my internal AB testing means my server can handle 1k concurrency @3k hits per second. My theory at at the moment is that the network is the bottleneck. The server can't send enough data fast enough. External testing from blitz.io at 1k concurrency shows my hits/s capping off at 180, with pages taking longer and longer to respond as the server is only able to return 180 per second. I've served a blank file from nginx and benched it: it scales 1:1 with concurrency. Now to rule out IO / memcached bottlenecks (nginx normally pulls from memcached), I serve up a static version of the cached page from the filesystem. The results are very similar to my original test; I'm capped at around 180 RPS. Splitting the HTML page in half gives me double the RPS, so it's definitely limited by the size of the page. If I internally ApacheBench from the local server, I get consistent results of around 4k RPS on both the Full Page and the Half Page, at high transfer rates. Transfer rate: 62586.14 [Kbytes/sec] received If I AB from an external server, I get around 180RPS - same as the blitz.io results. How do I know it's not intentional throttling? If I benchmark from multiple external servers, all results become poor which leads me to believe the problem is in MY servers outbound traffic, not a download speed issue with my benchmarking servers / blitz.io. So I'm back to my conclusion that my server can't send data fast enough. Am I right? Are there other ways to interpret this data? Is the solution/optimization to set up multiple servers + load balancing that can each serve 180 hits per second? I'm quite new to server optimization, so I'd appreciate any confirmation interpreting this data. Outbound traffic Here's more information about the outbound bandwidth: The network graph shows a maximum output of 16 Mb/s: 16 megabits per second. Doesn't sound like much at all. Due to a suggestion about throttling, I looked into this and found that linode has a 50mbps cap (which I'm not even close to hitting, apparently). I had it raised to 100mbps. Since linode caps my traffic, and I'm not even hitting it, does this mean that my server should indeed be capable of outputting up to 100mbps but is limited by some other internal bottleneck? I just don't understand how networks at this large of a scale work; can they literally send data as fast as they can read from the HDD? Is the network pipe that big? In conclusion 1: Based on the above, I'm thinking I can definitely raise my 180RPS by adding an nginx load balancer on top of a multi nginx server setup at exactly 180RPS per server behind the LB. 2: If linode has a 50/100mbit limit that I'm not hitting at all, there must be something I can do to hit that limit with my single server setup. If I can read / transmit data fast enough locally, and linode even bothers to have a 50mbit/100mbit cap, there must be an internal bottleneck that's not allowing me to hit those caps that I'm not sure how to detect. Correct? I realize the question is huge and vague now, but I'm not sure how to condense it. Any input is appreciated on any conclusion I've made.

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  • Prove correctness of unit test

    - by Timo Willemsen
    I'm creating a graph framework for learning purposes. I'm using a TDD approach, so I'm writing a lot of unit tests. However, I'm still figuring out how to prove the correctness of my unit tests For example, I have this class (not including the implementation, and I have simplified it) public class SimpleGraph(){ //Returns true on success public boolean addEdge(Vertex v1, Vertex v2) { ... } //Returns true on sucess public boolean addVertex(Vertex v1) { ... } } I also have created this unit tests @Test public void SimpleGraph_addVertex_noSelfLoopsAllowed(){ SimpleGraph g = new SimpleGraph(); Vertex v1 = new Vertex('Vertex 1'); actual = g.addVertex(v1); boolean expected = false; boolean actual = g.addEdge(v1,v1); Assert.assertEquals(expected,actual); } Okay, awesome it works. There is only one crux here, I have proved that the functions work for this case only. However, in my graph theory courses, all I'm doing is proving theorems mathematically (induction, contradiction etc. etc.). So I was wondering is there a way I can prove my unit tests mathematically for correctness? So is there a good practice for this. So we're testing the unit for correctness, instead of testing it for one certain outcome.

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  • How do you prove a function works?

    - by glenn I.
    I've recently gotten the testing religion and have started primarily with unit testing. I code unit tests which illustrate that a function works under certain cases, specifically using the exact inputs I'm using. I may do a number of unit tests to exercise the function. Still, I haven't actually proved anything other than the function does what I expect it to do under the scenarios I've tested. There may be other inputs and scenarios I haven't thought of and thinking of edge cases is expensive, particularly on the margins. This is all not very satisfying to do me. When I start to think of having to come up with tests to satisfy branch and path coverage and then integration testing, the prospective permutations can become a little maddening. So, my question is, how can one prove (in the same vein of proving a theorem in mathematics) that a function works (and, in a perfect world, compose these 'proofs' into a proof that a system works)? Is there a certain area of testing that covers an approach where you seek to prove a system works by proving that all of its functions work? Does anybody outside of academia bother with an approach like this? Are there tools and techniques to help? I realize that my use of the word 'work' is not precise. I guess I mean that a function works when it does what some spec (written or implied) states that it should do and does nothing other than that. Note, I'm not a mathematician, just a programmer.

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  • How to Prove that using subselect queries in SQL is killing performance of server

    - by adopilot
    One of my jobs it to maintain our database, usually we have troubles with lack of performance while getting reports and working whit that base. When I start looking at queries which our ERP sending to database I see a lot of totally needlessly subselect queries inside main queries. As I am not member of developers which is creator of program we using, they do not like much when I criticize they code and job. Let say they do not taking my review as serious statements. So I asking you few questions about subselect in SQL Does subselect is taking a lot of more time then left outer joins? Does exists any blog, article or anything where I subselect is recommended not to use ? How I can prove that if we avoid subselesct in query that query is going to be faster ? Our database server is MSSQL2005

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  • Prove 2^sqrt(log(n))= O(n^a)

    - by user1830621
    I posted a question similar to this earlier, although it seemed like it was much easier. I know the underlying principle of Big-O notation says that to prove that 2^sqrt(log(n)) is O(n^a), there must exist a positive value c for which c(n^a) = 2^sqrt(log(n)) for all values n = N. c*n^a >= 2^sqrt(log(n)) c >= 2^sqrt(log(n)) / n^a This number will always be positive so long as n 0. I suppose I could make N = 1 just to be safe. c = 2^sqrt(log(n)) / n^a N = 1 c*n^a = 2^sqrt(log(n) <= 2^log(n) for all values of n >= 1 Now, I know this is incorrect, because I could just as easily claim that the function 2^sqrt(log(n)) is O(n)...

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  • How to prove writing specifications beats code cowboys?

    - by Andrew Grant
    So I have a problem. Or rather my friend has a problem, since I would never write about my company on an internet forum. At my friend's company specification writing is, shall we say, a little underused. There's a deeply ingrained culture of writing code first and asking questions later, whether it's for a library routine or a new tool to inflict on their long suffering designers. This of course leads to situations where functionality is partially correct, incorrect, or just completely missing ("oh, just save before trying anything you may want to undo"). This usually results in a loss of productivity for those poor designers, or beta periods where bug-fixing is largely spent implementing things correctly. My friend's found his suggestions of writing (and testing against) specifications to be generally well received. Most of his colleagues have embraced the wonderful feeling of discovering false-assumptions on paper, instead of at 11pm on a Sunday in the middle of beta. Viva La Revolution! However there are a few who poo-poo anything that stands between their task and a keyboard. They laugh at the thought of actually designing anything, and write code with merry abandon. Mostly these are senior, long employed developers, reluctant to "waste time". The problem is that this second group of heretics invariably produce things (or at least something) quicker than the first. Subsequently this becomes justification along the lines of "It's pointless to write specifications for something as simple as an image resizer! Oh and those bugs where width!=height or the image uses RLE just need a few tweaks". And now the question :) Other than saying "told you so" at the end of a project, what are some good short-term ways to demonstrate how the practice of writing functional or technical specifications leads to better software in the long run? Cheers!

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  • Using Closure Properties to prove Regularity

    - by WATWF
    Here's a homework problem: Is L_4 Regular? Let L_4 = L*, where L={0^i1^i | i>=1}. I know L is non-regular and I know that Kleene Star is a closed operation, so my assumption is that L_4 is non-regular. However my professor provided an example of the above in which L = {0^p | p is prime}, which he said was regular by proving that L* was equal to L(000* + e) by saying each was a subset of one another (e in this case means the empty word). So his method involved forming a regex of 0^p, but how I can do that when I essentially have one already?

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  • IE6 and IE7 Standalone: Prove they're not the real thing

    - by yar
    It's common knowledge on SO (see this question) that to run IE6 and IE7 you need a Windows box (or virtual box) with only those apps installed. I doubt this is true (they are the real versions, I think). The two browsers I'm interested in are: Standalone IE6 from the MultipleIEs install Standalone IE7 also from Tredosoft (but published elsewhere) These two plus a "real" install of IE8 give you three IE versions in one Windows install. While we all know that "You're out of luck if you're trying to run them all reliably in one VM," but can someone please show me JS, CSS, or HTML (or a plugin, etc.) that does not work on the standalone versions as it should?

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  • How do I prove or disprove "god" objects are wrong?

    - by honestduane
    Problem Summary: Long story short, I inherited a code base and an development team I am not allowed to replace and the use of God Objects is a big issue. Going forward, I want to have us re-factor things but I am getting push-back from the teams who want to do everything with God Objects "because its easier" and this means I would not be allowed to re-factor. I pushed back citing my years of dev experience, that I'm the new boss who was hired to know these things, etc, and so did the third party offshore companies account sales rep, and this is now at the executive level and my meeting is tomorrow and I want to go in with a lot of technical ammo to advocate best practices because I feel it will be cheaper in the long run (And I personally feel that is what the third party is worried about) for the company. My issue is from a technical level, I know its good long term but I'm having trouble with the ultra short term and 6 months term, and while its something I "know" I cant prove it with references and cited resources outside of one person (Robert C. Martin, aka Uncle Bob), as that is what I am being asked to do as I have been told having data from one person and only one person (Robert C Martin) is not good enough of an argument. Question: What are some resources I can cite directly (Title, year published, page number, quote) by well known experts in the field that explicitly say this use of "God" Objects/Classes/Systems is bad (or good, since we are looking for the most technically valid solution)? Research I have already done: I have a number of books here and I have searched their indexes for the use of the words "god object" and "god class". I found that oddly its almost never used and the copy of the GoF book I have for example, never uses it (At least according to the index in front of me) but I have found it in 2 books per the below, but I want more I can use. I checked the Wikipedia page for "God Object" and its currently a stub with little reference links so although I personally agree with that it says, It doesn't have much I can use in an environment where personal experience is not considered valid. The book cited is also considered too old to be valid by the people I am debating these technical points with as the argument they are making is that "it was once thought to be bad but nobody could prove it, and now modern software says "god" objects are good to use". I personally believe that this statement is incorrect, but I want to prove the truth, whatever it is. In Robert C Martin's "Agile Principles, Patterns, and Practices in C#" (ISBN: 0-13-185725-8, hardcover) where on page 266 it states "Everybody knows that god classes are a bad idea. We don't want to concentrate all the intelligence of a system into a single object or a single function. One of the goals of OOD is the partitioning and distribution of behavior into many classes and many function." -- And then goes on to say sometimes its better to use God Classes anyway sometimes (Citing micro-controllers as an example). In Robert C Martin's "Clean Code: A Handbook of Agile Software Craftsmanship" page 136 (And only this page) talks about the "God class" and calls it out as a prime example of a violation of the "classes should be small" rule he uses to promote the Single Responsibility Principle" starting on on page 138. The problem I have is all my references and citations come from the same person (Robert C. Martin), and am from the same single person/source. I am being told that because he is just one guy, my desire to not use "God Classes" is invalid and not accepted as a standard best practice in the software industry. Is this true? Am I doing things wrong from a technical perspective by trying to keep to the teaching of Uncle Bob? God Objects and Object Oriented Programming and Design: The more I think of this the more I think this is more something you learn when you study OOP and its never explicitly called out; Its implicit to good design is my thinking (Feel free to correct me, please, as I want to learn), The problem is I "know" this, but but not everybody does, so in this case its not considered a valid argument because I am effectively calling it out as universal truth when in fact most people are statistically ignorant of it since statistically most people are not programmers. Conclusion: I am at a loss on what to search for to get the best additional results to cite, since they are making a technical claim and I want to know the truth and be able to prove it with citations like a real engineer/scientist, even if I am biased against god objects due to my personal experience with code that used them. Any assistance or citations would be deeply appreciated.

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  • Problem with Closure properties of context free languages

    - by altius
    hello i have the following sentence a language L1={a^n * b^n : n=0} and L2={b^n * a^n : n=0} are context free languages so they are close a=under the L1L2 so L={a^n * b^2n A^n : n=0} must be context free too because it is generated by a close property I have to prove if this sentence is true or not so i check the L language and i do not think that it is context free then i also saw that L2 is L1 reversed do i have to check if L1, L2 are deterministic ? please help because i am in a dead end

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  • Partner Webcast - Is your Application Ready? Prove it with the Oracle Exastack Program

    - by Thanos
    At Oracle we design Engineered Systems that are pre-integrated to reduce the cost and complexity of IT infrastructures while increasing productivity and performance. Oracle innovates and optimizes performance at every IT layer to simplify business operations, drive down costs and accelerate business innovation.As the Engineered System foundation platform, Oracle Exadata and Oracle Exalogic, run all of Oracle Cloud's services across a range of global data centers, delivering extreme performance, massive scalability, and fault tolerance that has no single point of failure.The Oracle Exastack Program enables you as an ISV to leverage Oracle's scalable, integrated infrastructure to test, tune and optimize your applications for high performance. By getting Exastack Ready and Exastack Optimized, your applications get formal recognition from Oracle and additional visibility, while you as an ISV receive additional set of OPN benefits. Don't miss this opportunity to learn more about how you can optimize your applications to run faster and more reliably leveraging Oracle Exastack, but also become more competitive letting everybody know you are ready. Agenda: Oracle Engineered Systems Strategy OPN Exastack Program Benefits & Objectives Value for You Oracle is resourced for your success How to Apply –Demo Next Steps & Useful contacts Delivery FormatThis FREE online LIVE eSeminar will be delivered over the Web. Registrations received less than 24hours prior to start time may not receive confirmation to attend. Thursday 06 December 2012, 10.00 CET (GMT+1) Duration: 1 hour Register Now! " height="6"> For any questions please contact us at [email protected] our ISV Migration Center blog Or Follow us @oracleimc to learn more on Oracle Technologies, upcoming partner webcasts and events. Existing content available YouTube - SlideShare - Oracle Mix

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  • Website content copied - How can I prove that I wrote it?

    - by Remy
    One of our competitors constantly copies all our website content. Now, I assume the trouble is to proof that we wrote the content first and that it is not the other way round. I checked on http://www.archive.org, but there is nothing. Any other way to proof that? FYI: We are a swiss company, so different laws will apply. Solution: [Found later] You can upload your content to this service and that they basically timestamp it. https://myows.com/ Another way we found, is to just print out your copy/design, etc. put it into an envelop and send it to ourself (without actually opening it later of course).

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  • Is it possible to calculate or mathematically prove if a game is balanced / fair?

    - by Lurca
    This question is not focussed on video games but games in general. I went to a boardgame trade fair yesterday and asked myself if there is a way to calculate the fairness of a game. Sure, some of them require a good portion of luck, but it might be possible to calculate if some character is overpowered. Especially in role-playing games and trading card games. How, for example, can the creators of "Magic: The Gathering" make sure that there isn't the "one card that beats them all", given the impressive number of available cards?

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  • How to prove that an email has been sent?

    - by bguiz
    I have a dispute on my hands in which the other party (landlord's real estate agent) dishonestly claims to not have received an email that I truly did send. My questions is, what are the ways to prove that the email was indeed sent? Thus far, the methods that I have already thought of are: Screenshot of the mail in the outbox Forwarding a copy of the original email I am aware of other things like HTTP/ SMTP headers etc that would exist as well. Are these useful for my purposes, and if so how do I extract these? The email in question was sent using Yahoo webmail ( http://au.mail.yahoo.com/ ). Edit: I am not seeking legal advice here, just technical advice as to how to gather this information.

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  • What is the best way to prove a processor is overheating / running too hot?

    - by Cheesegraterr
    Hello all! recently I noticed that my sister's laptop was getting very very hot when it sat on my lap, she had also complained that it just turned off on her without warning... so I decided to run Coretemp and Everest to test processor temperature.(It is an AMD Athlon X2... not sure what it runs at.) It seemed to idle around 75-80 Celsius and under 100% load it peaked at 115 ! I realize that laptops run a lot hotter than desktop but I think that is ridiculously hot...am I right? Anyway... Her laptop is still under warranty and I was wondering what is the best way to prove to future shop that it is running that hot. Should I give them a printout of a stress test or something like that? Or should I just bring it in to them and tell them what I think is wrong and let them test it. Thanks for the help!

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  • How to prove that an email has been sent?

    - by bguiz
    Hi, I have a dispute on my hands in which the other party (landlord's real estate agent) dishonestly claims to not have received an email that I truly did send. My questions is, what are the ways to prove that the email was indeed sent? Thus far, the methods that I have already thought of are: Screenshot of the mail in the outbox Forwarding a copy of the original email I am aware of other things like HTTP/ SMTP headers etc that would exist as well. Are these useful for my purposes, and if so how do I extract these? The email in question was sent using Yahoo webmail ( http://au.mail.yahoo.com/ ). Edit: I am not seeking legal advice here, just technical advice as to how to gather this information.

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