Search Results

Search found 745 results on 30 pages for 'proof'.

facebook twitter digg google delicious technorati stumbleupon myspace wordpress linkedin gmail igoogle windows live tumblr viadeo yahoo buzz yahoo mail yahoo bookmarks favorites email print

Page 3/30 | < Previous Page | 1 2 3 4 5 6 7 8 9 10 11 12  | Next Page >

  • Future proofing client-server code?

    - by Koran
    Hi, We have a web based client-server product. The client is expected to be used in the upwards of 1M users (a famous company is going to use it). Our server is set up in the cloud. One of the major questions while designing is how to make the whole program future proof. Say: Cloud provider goes down, then move automatically to backup in another cloud Move to a different server altogether etc The options we thought till now are: DNS: Running a DNS name server on the cloud ourselves. Directory server - The directory server also lives on the cloud Have our server returning future movements and future URLs etc to the client - wherein the client is specifically designed to handle those scenarios Since this should be a usual problem, which is the best solution for the same? Since our company is a very small one, we are looking at the least technically and financially expensive solution (say option 3 etc)? Could someone provide some pointers for the same? K

    Read the article

  • Valid Email Addresses - XSS and SQL Injection

    - by PAAMAYIM_NEKUDOTAYIM
    Since there are so many valid characters for email addresses, are there any valid email addresses that can in themselves be XSS attacks or SQL injections? I couldn't find any information on this on the web. The local-part of the e-mail address may use any of these ASCII characters: Uppercase and lowercase English letters (a–z, A–Z) Digits 0 to 9 Characters ! # $ % & ' * + - / = ? ^ _ ` { | } ~ Character . (dot, period, full stop) provided that it is not the last character, and provided also that it does not appear two or more times consecutively (e.g. [email protected]). http://en.wikipedia.org/wiki/E-mail_address#RFC_specification I'm not asking how to prevent these attacks (I'm already using parametrized queries and HTML purifier), this is more a proof-of-concept. The first thing that came to mind was 'OR [email protected], except that spaces are not allowed. Do all SQL injections require spaces?

    Read the article

  • What would you think of a job based on mostly doing the proof of concept?

    - by davsan
    I'm working as a developer in a small software company whose main job is interfacing between separate applications, like between a telephony system and an environment control system, between IP TVs and hospitality systems, etc...And it seems like I am the candidate for a new job title in the company, as the person who does the proof of concept of a new interfacing project and does some R&D for prototyping. What do you think the pros and cons of such a job would be, considering mainly the individual progress/regress of a person as a software engineer? And what aspects would you consider essential in a person to put him/her in such a job position?

    Read the article

  • Ask the Readers: How Do You Set Up a Novice-Proof Computer?

    - by Jason Fitzpatrick
    You’re into technology, you like tweaking and tinkering with computers, and, most importantly, you know how to keep your computer from turning into a virus-laden and fiery wreck. What about the rest of your family and friends? How do you set up a novice-proof computer to keep them secure, updated, and happy? It’s no small task protecting a computer from an inexperienced user, but for the benefit of both the novice and the innocent computer it’s an important undertaking. This week we want to hear all about your tips, tricks, and techniques for configuring the computers of your friends and relatives to save them from themselves (and keep their computer running smoothly in the process). Sound off in the comments with your tricks and check back in on Friday for the What You Said roundup to add see how your fellow readers get the job done. How Hackers Can Disguise Malicious Programs With Fake File Extensions Can Dust Actually Damage My Computer? What To Do If You Get a Virus on Your Computer

    Read the article

  • How do people prove the correctness of Computer Vision methods?

    - by solvingPuzzles
    I'd like to pose a few abstract questions about computer vision research. I haven't quite been able to answer these questions by searching the web and reading papers. How does someone know whether a computer vision algorithm is correct? How do we define "correct" in the context of computer vision? Do formal proofs play a role in understanding the correctness of computer vision algorithms? A bit of background: I'm about to start my PhD in Computer Science. I enjoy designing fast parallel algorithms and proving the correctness of these algorithms. I've also used OpenCV from some class projects, though I don't have much formal training in computer vision. I've been approached by a potential thesis advisor who works on designing faster and more scalable algorithms for computer vision (e.g. fast image segmentation). I'm trying to understand the common practices in solving computer vision problems.

    Read the article

  • Formal Equivalence between programming languages

    - by Ketan
    Hello We have 2 languages which are (informally) semantically equivalent but syntactically different. One is xml and another is script based. How can I go about formally proving that both languages are in fact equivalent. Script approach is just a convenient way to write a same program that would be tedious to write in xml. Thanks Ketan

    Read the article

  • 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.

    Read the article

  • Have I checked every consecutive subset of this list?

    - by Nathan
    I'm trying to solve problem 50 on Project Euler. Don't give me the answer or solve it for me, just try to answer this specific question. The goal is to find the longest sum of consecutive primes that adds to a prime below one million. I use wrote a sieve to find all the primes below n, and I have confirmed that it is correct. Next, I am going to check the sum of each subset of consecutive primes using the following method: I have a empty list sums. For each prime number, I add it to each element in sums and check the new sum, then I append the prime to sums. Here it is in python primes = allPrimesBelow(1000000) sums = [] for p in primes: for i in range(len(sums)): sums[i] += p check(sums[i]) sums.append(p) I want to know if I have called check() for every sum of two or more consecutive primes below one million The problem says that there is a prime, 953, that can be written as the sum of 21 consecutive primes, but I am not finding it.

    Read the article

  • How do I determine how future-proof and stable a router is?

    - by Aarthi
    I mentioned in my last question that my wireless router had a bad habit of crashing. After consulting with the Super User chatroom, as well as my sysadmin, I've decided I may as well purchase a new router. However, I'm unsure how to evaluate all these tech specs that get touted about. The two things that seem to be the most important to me are: (1) keeping my router future-proof (as standards evolve and change), and (2) ensuring its stability. Unfortunately, I'm not sure what, exactly, I should be looking for in the tech specs or the item description that can give me a good idea of how stable or future-proof my decide will be. What should I look for? Can I determine stability without having to try the device out myself? Please note: I'm not a battle-hardened power user by any means, so I'll likely be reliant on the given firmware for my router. My last router lasted me like four years, so I mostly just want something that'll cover a 500 sqft apartment in New York with minimal crashing, so that I can watch Hulu in peace. And make Skype calls. If it helps, the router models that I'm currently decided between are this ASUS one and this LinkSys one.

    Read the article

  • F# performance vs Erlang performance, is there proof the Erlang's VM is faster?

    - by afuzzyllama
    I've been putting time into learning functional programming and I've come to the part where I want to start writing a project instead of just dabbling in tutorials/examples. While doing my research, I've found that Erlang seems to be a pretty powerful when it comes to writing concurrent software (which is my goal), but resources and tools for development aren't as mature as Microsoft development products. F# can run on linux (Mono) so that requirement is met, but while looking around on the internet I cannot find any comparisons of F# vs Erlang. Right now, I am leaning towards Erlang just because it seems to have the most press, but I am curious if there is really any performance difference between the two languages. Since I am use to developing in .NET, I can probably get up to speed with F# a lot faster than Erlang, but I cannot find any resource to convince me that F# is just as scalable as Erlang. I am most interested in simulation, which is going to be firing a lot of quickly processed messages to persistant nodes. If I have not done a good job with what I am trying to ask, please ask for more verification.

    Read the article

  • How to future-proof my touch-enabled web application?

    - by Rice Flour Cookies
    I recently went out and purchased a touch-screen monitor with the intention of learning how to program touch-enabled web applications. I had reviewed the MDN documentation about touch events, as well as the W3C specification. To get started, I wrote a very short test page with two event handlers: one for the mousedown event and one for the touchstart event. I fired up the web page in IE and touched the document and found that only the mousedown event fired. I saw the same behavior with Firefox, only to find out later that Firefox can be set to enable the touchstart event using about:config. When touch events are enabled, the touchstart event fires, but not mousedown. Chrome was even stranger: it fired both events when I touched the document: touchstart and mousedown, in that order. Only on my Android phone does it appear to be the case that only the touchstart event fires when I touch the document. I did a a Google search and ended up on two interesting pages. First, I found the page on CanIUse for touch events: http://caniuse.com/#feat=touch Can I Use clearly indicates that IE does not support touch events as of this writing, and Firefox only supports touch events if they are manually enabled. Furthermore, all four browsers I mentioned treat the touch in a completely different way. It boils down to this: IE: simulated mouse click Firefox with touch disabled: simulated mouse click Firefox with touch enabled: touch event Chrome: touch event and simulated mouse click Android: touch event What is more frustrating is that Google also found a Microsoft page called RethinkIE. RethinkIE brags about touch support in IE; as a matter of fact, one of their slogans is "Touch the Web". It links to a number of touch-based application. I followed some of these links, and as best I can tell, it's just like CanIUse described; no proper touch support; just simulated mouse clicks. The MDN (https://developer.mozilla.org/en-US/docs/Web/API/Touch) and W3C (http://www.w3.org/TR/touch-events/) documentation describe a far richer interface; an interface that doesn't just simulate mouse clicks, but keeps track of multiple touches at once, the contact area, rotation, and force of each touch, and unique identifiers for each touch so that they can be tracked individually. I don't see how simulated mouse clicks can ever touch the above described functionality, which, once again, is part of the W3C specification, although it is listed as "non-normative", meaning that a browser can claim to be standards-compliant without implementing it. (Why bother making it part of the standard, then?) What motivated my research is that I've written an HTML5 application that doesn't work on Android because Android doesn't fire mouse events. I'm now afraid to try to implement touch for my application because the browsers all behave so differently. I imagine that at some time in the future, the browsers might start handling touch similarly, but how can I tell how they might be handled in the future short of writing code to handle the behavior of each individual browser? Is it possible to write code today that will work with touch-enabled browsers for years to come? If so, how?

    Read the article

  • Is it not possible to make a C++ application "Crash Proof"?

    - by Enno Shioji
    Let's say we have an SDK in C++ that accepts some binary data (like a picture) and does something. Is it not possible to make this SDK "crash-proof"? By crash I primarily mean forceful termination by the OS upon memory access violation, due to invalid input passed by the user (like an abnormally short junk data). I have no experience with C++, but when I googled, I found several means that sounded like a solution (use a vector instead of an array, configure the compiler so that automatic bounds check is performed, etc.). When I presented this to the developer, he said it is still not possible.. Not that I don't believe him, but if so, how is language like Java handling this? I thought the JVM performs everytime a bounds check. If so, why can't one do the same thing in C++ manually? UPDATE By "Crash proof" I don't mean that the application does not terminate. I mean it should not abruptly terminate without information of what happened (I mean it will dump core etc., but is it not possible to display a message like "Argument x was not valid" etc.?)

    Read the article

  • Need an idiot-proof picture resizing program for Windows.

    - by marcusw
    My friend needs to resize some pictures as part of a web publishing job, but he is rather clueless when it comes to computers. I am in charge of teaching him how to do this, but only have Linux (albeit with Wine installed) at my disposal for testing. Could you guys recommend a fast, easy, batch-capable, and hopefully open-source program that will resize pictures to the resolution he wants? It doesn't have to be anything fancy, but it needs to be quick and easy to use. Thanks!

    Read the article

  • Need an idiot-proof picture resizing program for Windblows.

    - by marcusw
    My friend needs to resize some pictures as part of a web publishing job, but he is rather clueless when it comes to computers. I am in charge of teaching him how to do this, but only have Linux (albeit with Wine installed) at my disposal for testing. Could you guys recommend a fast, easy, batch-capable, and hopefully open-source program that will resize pictures to the resolution he wants? It doesn't have to be anything fancy, but it needs to be quick and easy to use. Thanks!

    Read the article

  • What's the most reliable (i.e. time-proof) solution for organizing photos?

    - by digitxp
    I pooled together my photos from an old external hard drive, various Picasa Web caches, flickr, flash drives, and an old computer. They're all on my external hard drive, using extremely creative labeling, like allpictures pixix pix2 images familyphotos and so on (hey, I was 7 when I organized them last). My computer's hard drive can die at any minute, and the external is new but who knows what that means? I am planning to start reorganizing these picture, probably by face or time. I have Bridge CS5, Picasa, etc., but which one is the most likely to not crash and burn like my Vista laptop did with a ZIP file filled with pictures of a funeral?

    Read the article

  • How to best future proof my application that needs to connect to Outlook?

    - by Troy
    I have a contact management application written in Delphi which has a “Sync with Outlook” feature that I developed 10 years ago. Now, I’m going back to add some features and fix some bugs. This sync feature uses the Outlook object model to get started, but it has an optional mode called “Use MAPI Enhancements” where it uses pure MAPI to speed up how it looks for changes, and it allows notes to be synced w/ RTF instead of just plain text. I'm wondering if supporting two parallel paths of execution is a good idea or not. If I went with all MAPI, I believe I'd avoid some security prompts, and I'd avoid situations where anti-virus has "script-blocking" features which block my app from connecting to Outlook. But I believe that on the down side, my 32-bit app would not be able to to connect with 64-bit Outlook 2010 using MAPI. And I wonder about the future of MAPI in general. If I stick with the Outlook object model, will my 32-bit app be able to connect to the Outlook object model (since it's out of process COM)? If so, this is a compelling reason to keep my Outlook object model execution path in place. But if not, and if my app needs to be compiled for x64, then why not just go with pure MAPI?

    Read the article

  • SOA &amp; Application Grid Specialization &ndash; 6 steps to success &ndash; part 1 OMM

    - by Jürgen Kress
    SOA Specialization – Oracle Open Market Model (OMM) Dear Application Grid SOA Partners, Or goal is to SOA Specialize you, in the next weeks we will inform you in a series how you can achieve SOA Specialization. Specialization is key the be recognized by Oracle and to be preferred by our Customers. The first step to become SOA Specialized is to proof 2 transactions. You can either resell, co-sell or referral – as a proof point we do use our Open Market Model (OMM). To create your account go to our new Partner Portal: go to login of your OPN-Homepage: http://oraclepartnernetwork.oracle.com click on: "Sales" "Create a PRM User Account" Enter your User ID: Enter Company Identifier: ((please ask your OPN IC)) Finish Wait for a Confirmation Email If you need OMM support please contact out dedicated team: Nordics  please ask: [email protected] Portugal, Spain please ask: [email protected] Austria, Belgium, Germany, Luxembourg, Netherlands, Switzerland, United Arab Emirates, United Kingdom please ask: [email protected] For more information about OMM watch our on-demand webcast “Recognising the Value of Partners: Register Oracle Deals through the Open Market Model (OMM)”. Become SOA Specialized today SOA Specialized & Application Grid Specialized Create your references, create your OMM Entry, take the SOA Sales assessment, take the SOA Pre-Sales assessment, take the Support assessment and register for the SOA Implementation assessment. For more information on Specialization please visit our OPN Specialized Webcast Series To get support on Specialization please contact the Partner Business Centers.   SOA Specialized Application Grid Specialized Proof 2 transactions with OMM Proof 2 transactions with OMM Create your 2 references Create your 2 references SOA Sales assessment 3, Oracle Application Grid Sales Specialist  SOA Pre-Sales assessment 3 Oracle Application Grid PreSales Specialist Support assessment 1 Support assessment 2 SOA Implementation assessment 4 Application Grid Implementation assessment 4

    Read the article

  • Django: select_related and GenericRelation

    - by Parand
    Does select_related work for GenericRelation relations, or is there a reasonable alternative? At the moment Django's doing individual sql calls for each item in my queryset, and I'd like to avoid that using something like select_related. class Claim(models.Model): proof = generic.GenericRelation(Proof) class Proof(models.Model): content_type = models.ForeignKey(ContentType) object_id = models.PositiveIntegerField() content_object = generic.GenericForeignKey('content_type', 'object_id') I'm selecting a bunch of Claims, and I'd like the related Proofs to be pulled in instead of queried individually.

    Read the article

  • Solving Big Problems with Oracle R Enterprise, Part II

    - by dbayard
    Part II – Solving Big Problems with Oracle R Enterprise In the first post in this series (see https://blogs.oracle.com/R/entry/solving_big_problems_with_oracle), we showed how you can use R to perform historical rate of return calculations against investment data sourced from a spreadsheet.  We demonstrated the calculations against sample data for a small set of accounts.  While this worked fine, in the real-world the problem is much bigger because the amount of data is much bigger.  So much bigger that our approach in the previous post won’t scale to meet the real-world needs. From our previous post, here are the challenges we need to conquer: The actual data that needs to be used lives in a database, not in a spreadsheet The actual data is much, much bigger- too big to fit into the normal R memory space and too big to want to move across the network The overall process needs to run fast- much faster than a single processor The actual data needs to be kept secured- another reason to not want to move it from the database and across the network And the process of calculating the IRR needs to be integrated together with other database ETL activities, so that IRR’s can be calculated as part of the data warehouse refresh processes In this post, we will show how we moved from sample data environment to working with full-scale data.  This post is based on actual work we did for a financial services customer during a recent proof-of-concept. Getting started with the Database At this point, we have some sample data and our IRR function.  We were at a similar point in our customer proof-of-concept exercise- we had sample data but we did not have the full customer data yet.  So our database was empty.  But, this was easily rectified by leveraging the transparency features of Oracle R Enterprise (see https://blogs.oracle.com/R/entry/analyzing_big_data_using_the).  The following code shows how we took our sample data SimpleMWRRData and easily turned it into a new Oracle database table called IRR_DATA via ore.create().  The code also shows how we can access the database table IRR_DATA as if it was a normal R data.frame named IRR_DATA. If we go to sql*plus, we can also check out our new IRR_DATA table: At this point, we now have our sample data loaded in the database as a normal Oracle table called IRR_DATA.  So, we now proceeded to test our R function working with database data. As our first test, we retrieved the data from a single account from the IRR_DATA table, pull it into local R memory, then call our IRR function.  This worked.  No SQL coding required! Going from Crawling to Walking Now that we have shown using our R code with database-resident data for a single account, we wanted to experiment with doing this for multiple accounts.  In other words, we wanted to implement the split-apply-combine technique we discussed in our first post in this series.  Fortunately, Oracle R Enterprise provides a very scalable way to do this with a function called ore.groupApply().  You can read more about ore.groupApply() here: https://blogs.oracle.com/R/entry/analyzing_big_data_using_the1 Here is an example of how we ask ORE to take our IRR_DATA table in the database, split it by the ACCOUNT column, apply a function that calls our SimpleMWRR() calculation, and then combine the results. (If you are following along at home, be sure to have installed our myIRR package on your database server via  “R CMD INSTALL myIRR”). The interesting thing about ore.groupApply is that the calculation is not actually performed in my desktop R environment from which I am running.  What actually happens is that ore.groupApply uses the Oracle database to perform the work.  And the Oracle database is what actually splits the IRR_DATA table by ACCOUNT.  Then the Oracle database takes the data for each account and sends it to an embedded R engine running on the database server to apply our R function.  Then the Oracle database combines all the individual results from the calls to the R function. This is significant because now the embedded R engine only needs to deal with the data for a single account at a time.  Regardless of whether we have 20 accounts or 1 million accounts or more, the R engine that performs the calculation does not care.  Given that normal R has a finite amount of memory to hold data, the ore.groupApply approach overcomes the R memory scalability problem since we only need to fit the data from a single account in R memory (not all of the data for all of the accounts). Additionally, the IRR_DATA does not need to be sent from the database to my desktop R program.  Even though I am invoking ore.groupApply from my desktop R program, because the actual SimpleMWRR calculation is run by the embedded R engine on the database server, the IRR_DATA does not need to leave the database server- this is both a performance benefit because network transmission of large amounts of data take time and a security benefit because it is harder to protect private data once you start shipping around your intranet. Another benefit, which we will discuss in a few paragraphs, is the ability to leverage Oracle database parallelism to run these calculations for dozens of accounts at once. From Walking to Running ore.groupApply is rather nice, but it still has the drawback that I run this from a desktop R instance.  This is not ideal for integrating into typical operational processes like nightly data warehouse refreshes or monthly statement generation.  But, this is not an issue for ORE.  Oracle R Enterprise lets us run this from the database using regular SQL, which is easily integrated into standard operations.  That is extremely exciting and the way we actually did these calculations in the customer proof. As part of Oracle R Enterprise, it provides a SQL equivalent to ore.groupApply which it refers to as “rqGroupEval”.  To use rqGroupEval via SQL, there is a bit of simple setup needed.  Basically, the Oracle Database needs to know the structure of the input table and the grouping column, which we are able to define using the database’s pipeline table function mechanisms. Here is the setup script: At this point, our initial setup of rqGroupEval is done for the IRR_DATA table.  The next step is to define our R function to the database.  We do that via a call to ORE’s rqScriptCreate. Now we can test it.  The SQL you use to run rqGroupEval uses the Oracle database pipeline table function syntax.  The first argument to irr_dataGroupEval is a cursor defining our input.  You can add additional where clauses and subqueries to this cursor as appropriate.  The second argument is any additional inputs to the R function.  The third argument is the text of a dummy select statement.  The dummy select statement is used by the database to identify the columns and datatypes to expect the R function to return.  The fourth argument is the column of the input table to split/group by.  The final argument is the name of the R function as you defined it when you called rqScriptCreate(). The Real-World Results In our real customer proof-of-concept, we had more sophisticated calculation requirements than shown in this simplified blog example.  For instance, we had to perform the rate of return calculations for 5 separate time periods, so the R code was enhanced to do so.  In addition, some accounts needed a time-weighted rate of return to be calculated, so we extended our approach and added an R function to do that.  And finally, there were also a few more real-world data irregularities that we needed to account for, so we added logic to our R functions to deal with those exceptions.  For the full-scale customer test, we loaded the customer data onto a Half-Rack Exadata X2-2 Database Machine.  As our half-rack had 48 physical cores (and 96 threads if you consider hyperthreading), we wanted to take advantage of that CPU horsepower to speed up our calculations.  To do so with ORE, it is as simple as leveraging the Oracle Database Parallel Query features.  Let’s look at the SQL used in the customer proof: Notice that we use a parallel hint on the cursor that is the input to our rqGroupEval function.  That is all we need to do to enable Oracle to use parallel R engines. Here are a few screenshots of what this SQL looked like in the Real-Time SQL Monitor when we ran this during the proof of concept (hint: you might need to right-click on these images to be able to view the images full-screen to see the entire image): From the above, you can notice a few things (numbers 1 thru 5 below correspond with highlighted numbers on the images above.  You may need to right click on the above images and view the images full-screen to see the entire image): The SQL completed in 110 seconds (1.8minutes) We calculated rate of returns for 5 time periods for each of 911k accounts (the number of actual rows returned by the IRRSTAGEGROUPEVAL operation) We accessed 103m rows of detailed cash flow/market value data (the number of actual rows returned by the IRR_STAGE2 operation) We ran with 72 degrees of parallelism spread across 4 database servers Most of our 110seconds was spent in the “External Procedure call” event On average, we performed 8,200 executions of our R function per second (110s/911k accounts) On average, each execution was passed 110 rows of data (103m detail rows/911k accounts) On average, we did 41,000 single time period rate of return calculations per second (each of the 8,200 executions of our R function did rate of return calculations for 5 time periods) On average, we processed over 900,000 rows of database data in R per second (103m detail rows/110s) R + Oracle R Enterprise: Best of R + Best of Oracle Database This blog post series started by describing a real customer problem: how to perform a lot of calculations on a lot of data in a short period of time.  While standard R proved to be a very good fit for writing the necessary calculations, the challenge of working with a lot of data in a short period of time remained. This blog post series showed how Oracle R Enterprise enables R to be used in conjunction with the Oracle Database to overcome the data volume and performance issues (as well as simplifying the operations and security issues).  It also showed that we could calculate 5 time periods of rate of returns for almost a million individual accounts in less than 2 minutes. In a future post, we will take the same R function and show how Oracle R Connector for Hadoop can be used in the Hadoop world.  In that next post, instead of having our data in an Oracle database, our data will live in Hadoop and we will how to use the Oracle R Connector for Hadoop and other Oracle Big Data Connectors to move data between Hadoop, R, and the Oracle Database easily.

    Read the article

  • Opinion on "loop invariants", and are these frequently used in the industry?

    - by Michael Aaron Safyan
    I was thinking back to my freshman year at college (five years ago) when I took an exam to place-out of intro-level computer science. There was a question about loop invariants, and I was wondering if loop invariants are really necessary in this case or if the question was simply a bad example... the question was to write an iterative definition for a factorial function, and then to prove that the function was correct. The code that I provided for the factorial function was as follows: public static int factorial(int x) { if ( x < 0 ){ throw new IllegalArgumentException("Parameter must be = 0"); }else if ( x == 0 ){ return 1; }else{ int result = 1; for ( int i = 1; i <= x; i++ ){ result*=i; } return result; } } My own proof of correctness was a proof by cases, and in each I asserted that it was correct by definition (x! is undefined for negative values, 0! is 1, and x! is 1*2*3...*x for a positive value of x). The professor wanted me to prove the loop using a loop invariant; however, my argument was that it was correct "by definition", because the definition of "x!" for a positive integer x is "the product of the integers from 1... x", and the for-loop in the else clause is simply a literal translation of this definition. Is a loop invariant really needed as a proof of correctness in this case? How complicated must a loop be before a loop invariant (and proper initialization and termination conditions) become necessary for a proof of correctness? Additionally, I was wondering... how often are such formal proofs used in the industry? I have found that about half of my courses are very theoretical and proof-heavy and about half are very implementation and coding-heavy, without any formal or theoretical material. How much do these overlap in practice? If you do use proofs in the industry, when do you apply them (always, only if it's complicated, rarely, never)?

    Read the article

facebook twitter digg google delicious technorati stumbleupon myspace wordpress linkedin gmail igoogle windows live tumblr viadeo yahoo buzz yahoo mail yahoo bookmarks favorites email print

< Previous Page | 1 2 3 4 5 6 7 8 9 10 11 12  | Next Page >