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  • Exclusive use of a Jini server during long-running call

    - by Matthew Flint
    I'm trying to use Jini, in a "Masters/Workers" arrangement, but the Worker jobs may be long running. In addition, each worker needs to have exclusive access to a singleton resource on that machine. As it stands, if a Worker receives another request while a previous request is running, then the new request is accepted and executed in a second thread. Are there any best-practices to ensure that a Worker accepts no further jobs until the current job is complete? Things I've considered: synchronize the job on the server, with a lock on the singleton resource. This would work, but is far from ideal. A call from a Master would block until the current Worker thread completes, even if other Workers become free in the meantime unregister the Worker from the registry while the job is running, then re-register when it completes. Might work OK, but something doesn't smell right with this idea... Of course, I'm quite happy to be told that there are more appropriate technologies than Jini... but I wouldn't want anything too heavyweight, like rolling out EJB containers all over the place.

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  • What is the relationship between the business logic layer and the data access layer?

    - by Matt Fenwick
    I'm working on an MVC-ish app (I'm not very experienced with MVC, hence the "-ish"). My model and data access layer are hard to test because they're very tightly coupled, so I'm trying to uncouple them. What is the nature of the relationship between them? Should just the model know about the DAL? Should just the DAL know about the model? Or should both the model and the DAL be listeners of the other? In my specific case, it's: a web application the model is client-side (javascript) the data is accessed from the back-end using Ajax persistence/back-end is currently PHP/MySQL, but may have to switch to Python/GoogleDataStore on the GAE

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  • What are basic programming directions? [closed]

    - by Goward Gerald
    What are basic programming directions? Can you please list them and give a brief review of each? Would be nice to have a list for each direction (web-development/*enterprise*/standalone/*mobile*/etc, correct me if I skipped something) like this: 1). Most popular languages of this direction (php for web, objective C for iOS mobile development etc) 2). It's demand on market (from 0 to 5, subjective) 3). How much tasks differ (do you always create same-of-a-kind programs which are like clones of each oother or projects change and you often get to create something interesting, new and fresh?) 4). Freelance demand (from 0 to 5) 5). Fun factor (from 0 to 5, totally subjective but still write it please) Thanks!

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  • Parsing stdout with custom format or standard format?

    - by linquize
    To integrate with other executables, a executable may launch another executable and capture its output from stdout. But most programs writes the output message to stdout in custom format and usually in human readable format. So it requires the system integrator to write a function to parse the output, which is considered trouble and the parser code may be buggy. Do you think this is old fashioned? Most Unix-style programs do that. Very few programs write to stdout in standard format such as XML or JSON, which is more modern. Example: Veracity (DVCS) writes JSON to stdout. Should we switch to use modern formats? For a console program, human readable or easy parsable: which is more important ?

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  • Best questions to ask a startup founder, CTO, or CEO

    - by YGomez
    This is not a duplicate of this SE post. Most questions of this sort center around an interview experience. I want questions that you might be genuinely interested in, even if they are not at all appropriate to ask during a job interview. If you have read the book Founders at Work, that is the kind of question I am talking about. So I guess, what would you ask if you were interviewing them? I am specially interested in questions that might give a possible future startup founder insight.

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  • Why does it take so long to finalize the HTML 5 spec?

    - by EpsilonVector
    I was reading this and one sentence caught my eye (emphasis mine): So Ian Hickson, XHTML’s biggest critic, fathered HTML 5, an action-oriented toddler specification that won’t reach adulthood until 2022, although some of it can be used today. Is that true? Is that really the HTML 5 development cycle? Why is it taking so long? What makes it so difficult to get right that it won't be final until 11 years from now?

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  • How should I safely send bulk mail? [closed]

    - by Jerry Dodge
    First of all, we have a large software system we've developed and have a number of clients using it in their own environment. Each of them is responsible for using their own equipment and resources, we don't provide any services to share with them. We have introduced an automated email system which sends emails automatically via SMTP. Usually, it only sends around 10-20 emails a day, but it's very possible to send bulk email up to thousands of people in a single day. This of course requires a big haul of work, which isn't necessarily the problem. The issue arises when it comes to the SMTP server we're using. An email server is issued a number of relays a day, which is paid for. This isn't really necessarily the issue either. The risk is getting the email server blacklisted. It's inevitable, and we need to carefully take all this into consideration. As far as I can see, the ideal setup would be to have at least 50 IP addresses on multiple servers, each of which hosts its own SMTP server. When sending bulk email, it will divide them up across these servers, and each one will process its own queue. If one of those IP's gets blacklisted, it will be decommissioned and a new IP will replace it. Is there a better way that doesn't require us to invest in a large handful of servers? Perhaps a third party service which is meant exactly for this?

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  • is Microsoft LC random generator patented?

    - by user396672
    I need a very simple pseudo random generator (no any specific quality requirements) and I found Microsoft's variant of LCG algorithm used for rand() C runtime library function fit my needs (gcc's one seems too complex). I found the algorithm here: http://rosettacode.org/wiki/Linear_congruential_generator#C However, I worry the algorithm (including its "magic numbers" i.e coefficients) may by patented or restricted for use in some another way. Is it allowed to use this algorithm without any licence or patent restrictions or not? I can't use library rand() because I need my results to be exactly reproducible on different platforms

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  • How Did we get from CLI to Graphics?

    - by Nathaniel Bennett
    I'm confused when looking into graphics - specifically with operating systems. I mean, how can a computer render a CLI/console along with a GUI. GUI's are completely different from Text. and How Can we have GUI windows that Display Text interfaces, ie how can we have CLI in modern Graphics Operating system - that's what I'm mainly trying to grip on to. How Do Graphic's get rendered to display? is there some sort of memory address that a GPU access which holds all pixel data, and there system's within OS's that Gather the pixel position of Windows and Widgets, along with the Z Index and rasterize them to that memory address, which then the GPU loads to the screen? How About the CLI's integrated with Graphics? how does the OS Tell the GPU that a certain part of the screen wants to display text while the rest, whats to display pixel data? it's all very confusing. Shed some light in it, will ya?

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  • Extreme Programming Dying? [closed]

    - by jonny
    Is Extreme Programming Dying? I've been reviewing my fellow students reports on extreme programming.(I am a student myself) Some students are claiming that extreme programming lacks in empirical evidences, and is relevantly new, hence lacking in empirical evidence. XP is already 13 years old it should be considered as new, from my perspective. I guess the practices of XP has been tweaked and used in newer methodologies such as scrum. What are your point of view on this, do you guys think XP is Dying?

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  • What is the difference between Static code analysis and code review?

    - by Xander
    I just wanted to know what is the difference between static code analysis and code review. How these two are done? What are the tools available today for code review/ static analysis of PHP. I also like to know about good tools for any language code review. Thanks in Advance. Xander Cage Note: I am asking this because I was not able to understand the difference. Please, I expect some answers than "I am Mr.Geek and you asked an irrelevant bla bla..... this is closed". I know this sounds mean. But I am sorry.

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  • C# or .Net features to cut off assuming no backward compatibility needed?

    - by Gulshan
    Any product or framework evolves. Mainly it's done to catch up the needs of it's users, leverage new computing powers and simply make it better. Sometimes the primary design goal also changes with the product. C# or .net framework is no exception. As we see, the present day 4th version is very much different comparing with the first one. But thing comes as a barricade to this evolution- backward compatibility. In most of frameworks/products there are features would have been cut off if there was no need to support backward compatibility. According to you, what are these features in C#/.net? Please mention one feature per answer.

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  • PHP ORM style of querying

    - by Petah
    Ok so I have made an ORM library for PHP. It uses syntax like so: *(assume that $business_locations is an array)* Business::type(Business:TYPE_AUTOMOTIVE)-> size(Business::SIZE_SMALL)-> left_join(BusinessOwner::table(), BusinessOwner::business_id(), SQL::OP_EQUALS, Business::id())-> left_join(Owner::table(), SQL::OP_EQUALS, Owner::id(), BusinessOwner::owner_id())-> where(Business::location_id(), SQL::in($business_locations))-> group_by(Business::id())-> select(SQL::count(BusinessOwner::id()); Which can also be represented as: $query = new Business(); $query->set_type(Business:TYPE_AUTOMOTIVE); $query->set_size(Business::SIZE_SMALL); $query->left_join(BusinessOwner::table(), BusinessOwner::business_id(), SQL::OP_EQUALS, $query->id()); $query->left_join(Owner::table(), SQL::OP_EQUALS, Owner::id(), BusinessOwner::owner_id()); $query->where(Business::location_id(), SQL::in($business_locations)); $query->group_by(Business::id()); $query->select(SQL::count(BusinessOwner::id()); This would produce a query like: SELECT COUNT(`business_owners`.`id`) FROM `businesses` LEFT JOIN `business_owners` ON `business_owners`.`business_id` = `businesses`.`id` LEFT JOIN `owners` ON `owners`.`id` = `business_owners`.`owner_id` WHERE `businesses`.`type` = 'automotive' AND `businesses`.`size` = 'small' AND `businesses`.`location_id` IN ( 1, 2, 3, 4 ) GROUP BY `businesses`.`id` Please keep in mind that the syntax might not be prefectly correct (I only wrote this off the top of my head) Any way, what do you think of this style of querying? Is the first method or second better/clearer/cleaner/etc? What would you do to improve it?

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  • In a SSL web application, what would be the vulnerabilities of using session based authentication?

    - by Thomas C. G. de Vilhena
    I'm not sure the term even exists, so let me explain what I mean by "session based authentication" through some pseudo-code: void PerformLogin(string userName, string password) { if(AreValidCredentials(userName, password)) { Session.Set("IsAuthenticated", true); } else { Message.Show("Invalid credentials!"); } } So the above method simply verifies the provided credentials are valid and then sets a session flag to indicate that the session user is authenticated. Under plain HTTP that is obviously unsafe, because anyone could hijack the session cookie/querystring and breach security. However, under HTTPS the session cookie/querystring is protected because client-server communication is encrypted, so I believe this authentication approach would be safe, wouldn't it? I'm asking this because I want to know how authentication tickets can improve web applications security. Thanks in advance!

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  • What are the steps to grouping related classes into packages

    - by user2368481
    I've been googling this for some time, but what I haven't found are the clear steps needed to be taken to group related classes into packages in Java. In my case, I have about a number of .java files that I'd like to group into 3 packages according to the MVC pattern. One package for Model classes, one package for View classes and one package for Controller classes. I've identified which belong in what package, but not sure of the next step.

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  • MATLAB: Best fitness vs mean fitness, initial range

    - by Sa Ta
    Based on the example of Rastrigin's function. At the plot function, if I chose 'best fitness', on the same graph 'mean fitness' will also be plotted. I understand well about 'best fitness' whereby it plots the best function value in each generation versus iteration number. It will reach value zero after some times. I don't understand about 'mean fitness'in the graph plotted. What do those 'mean fitness' values mean? How does the 'mean fitness' graph help to understand Rastrigin's function? What are the meaning of the term initial population, initial score and initial range? I wish to have a better understanding of these terms. The default value for initial range is [0,1]. Does it mean that 0 is the lower bound (lb) and 1 is the upper bound (ub)? Do these values interfere with the lb and ub values I set in the constraints? I try to better understand about lb and ub. If my lb is 0 and ub is 5, does it mean that my final point values will be within 0 and 5? If I know the lb and ub for my problem is between 0 and 5, do I just set the initial range as [0,5] at all times and may I assume that this is the best option for initial range, and I need not try it with any other values?

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  • Finding Database issue for iphone app

    - by David Liu
    I know this is a dumb question and it might not be "conceptual" but, as a self-starter I really want to know how to get connected to some sort of "commercial database"? I'm recently designing my local gas station utility app for iphone and ipad. I have absolutely no clue of find a relevant database. For example, if I want to make an app for pizza ordering in the great Chicago area. How do I get info (price, menu, location, etc.) of those pizza stores scattered all over Chicago? Can any one light something for me? I appreciated your help. **If this question is not suitable here please tell me and I will delete this post. Thank you.

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  • Strategy for clients to retrieve real-time log from HTTP server

    - by Jerry Dodge
    I have an HTTP Server Service application which has its own logging mechanism. It's written in Delphi. I would like to provide a way for multiple clients to connect to this service and get a real-time update of the log. The log in the service moves rather fast, there's a lot of things to log. There may be up to 50 messages within 1 second at times. The existing log which is already implemented is not saved, it's only kept in the memory of the server service - where I will need to distribute it to any client which needs it. Once all clients have a log message, it should be deleted. I intend to use HTTP to "ask" the server for the log, and respond with an XML packet. The connections are not keep-alive. The only problem is, the server should only send the client those log records which it needs, not everything. I have no way of the server pushing the log to the clients in real-time, so each client needs to repeatedly ask the server for the latest log records. This HTTP Server is very lightweight, and there is no session management. There isn't even any type of authentication. The only way I see is for a client to register its self on the server, and whenever a log is issued on the server, it creates a copy of the log for each client, where each client has a log queue (string list). However, suppose there are 100 clients connected and expecting to receive this log. That means the server must create 100 copies of each log, add this log to the end of each client log queue, and wait for the client to request it. At that point, when the server replies with the XML log, it should flush (delete) whatever's in the queue. I'm worried however that this could cause memory issues. Each client log queue might get 100 log messages before the client requests the latest logs. How should I go about doing this in the fastest way possible without hindering the performance of the server? I'm trying to avoid having to create a copy of each log for each client.

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  • Drawing Flowchart for function calculate a number in the Fibonacci Series

    - by truongvan
    I'm trying make Flowchart for function calculate a number in the Fibonacci Series. But It looks like not right. I don't how draw the recursive function. Please help me how to fix it. My flowchart: DIA This is my code: #include <iostream> using namespace std; long long Fibonacci(int input); int main() { cout << "Input Fibonacci Index number: "; int Index = 0; cin >> Index; cout << Fibonacci(i) << endl; return 0; } long long Fibonacci(int input) { if (input < 2) return input; else { return Fibonacci(input - 1) + Fibonacci(input - 2); } }

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  • Class instance clustering in object reference graph for multi-entries serialization

    - by Juh_
    My question is on the best way to cluster a graph of class instances (i.e. objects, the graph nodes) linked by object references (the -directed- edges of the graph) around specifically marked objects. To explain better my question, let me explain my motivation: I currently use a moderately complex system to serialize the data used in my projects: "marked" objects have a specific attributes which stores a "saving entry": the path to an associated file on disc (but it could be done for any storage type providing the suitable interface) Those object can then be serialized automatically (eg: obj.save()) The serialization of a marked object 'a' contains implicitly all objects 'b' for which 'a' has a reference to, directly s.t: a.b = b, or indirectly s.t.: a.c.b = b for some object 'c' This is very simple and basically define specific storage entries to specific objects. I have then "container" type objects that: can be serialized similarly (in fact their are or can-be "marked") they don't serialize in their storage entries the "marked" objects (with direct reference): if a and a.b are both marked, a.save() calls b.save() and stores a.b = storage_entry(b) So, if I serialize 'a', it will serialize automatically all objects that can be reached from 'a' through the object reference graph, possibly in multiples entries. That is what I want, and is usually provides the functionalities I need. However, it is very ad-hoc and there are some structural limitations to this approach: the multi-entry saving can only works through direct connections in "container" objects, and there are situations with undefined behavior such as if two "marked" objects 'a'and 'b' both have a reference to an unmarked object 'c'. In this case my system will stores 'c' in both 'a' and 'b' making an implicit copy which not only double the storage size, but also change the object reference graph after re-loading. I am thinking of generalizing the process. Apart for the practical questions on implementation (I am coding in python, and use Pickle to serialize my objects), there is a general question on the way to attach (cluster) unmarked objects to marked ones. So, my questions are: What are the important issues that should be considered? Basically why not just use any graph parsing algorithm with the "attach to last marked node" behavior. Is there any work done on this problem, practical or theoretical, that I should be aware of? Note: I added the tag graph-database because I think the answer might come from that fields, even if the question is not.

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  • What to do when the programming activity becomes a problem?

    - by gablin
    I once saw a program (can't remember which) where it talked about people "experiencing flow" when they are doing something they are passionate about. When "in flow", they tend to lose track of time and surrounding, concentrating only on their activity at hand. This happens a lot for me when I program; most particularly when I face a problem. I refuse to give up until it's solved. This usually leads to hours just rushing by and I forget to eat lunch, dinner gets pushed into far into the evening, and when I finally look at the clock, it's way into the wee-hours of the night and I will only get a few hours of sleep before having to rise early in the morning. (This is not to say that I'm in flow only when facing a problem - but I find it particularly hard to stop programming and step back when there's something I can't solve immediately.) I love programming, but I hate it when it disrupts my normal routines (most importantly eating and sleeping patterns). And sitting still for so many hours, staring a screen, is not healthy. Please, any ideas on how I can get my rampant programming activity under control?

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  • Why doesn't my IDE do background compiling/building?

    - by MKO
    Today I develop on a fairly complex computer, it has multiple cores, SSD drives and what not. Still, most of the time I'm programming the computer is leasurely doing nothing. When I need to compile and run/deploy a somewhat complex project at best it still takes a couple of seconds. Why? Now that we're living more and more in the "age of instant" why can't I press F5 in Visual studio and launch/deploy my application instantly? A couple of seconds might not sound so bad but it's still cognitive friction and time that adds up, and frankly it makes programming less fun. So how could compilation be instant? Well, People tend to edit files in different assemblies, what if Visual Studio/The IDE constantly did compilation/and building of everything that I modified anytime that it might be appropriate. Heck if they wanted to go really advanced they could do per-class compilation. The compilation might not work but then it could just silently do nothing (except adding error messages to the error window). Surely todays computer could dedicate a core or two to this task, and if someone found it annoying it could be disabled by option. I know there's probably a thousand technical issues and some fancy shadow copying that would need to be resolved for this to be seamless and practical but it sure would make programming more seamless. Is there any practical reason why this scenario isn't possible? Would the wear and tear of continually writing binaries be too much? Couldn't assemblies be held in memory until deployed/run?

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  • For what types of applications is Python a bad choice?

    - by Casey Patton
    I just started learning Python, and I'd like to get some more context on the language. I realize that Python is a slow language relative to C or C++, etc. Thus, Python is probably not the best choice for applications that need to run quickly. Outside of this, it seems like Python is a great general purpose language that is easy to read and write. The available libraries give it a huge amount of functionality. Outside of performance critical applications, where is it a bad choice to use Python (and why)?

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  • Using which technique does facebook and pininterest show images?

    - by manish
    If anybody has ever noticed that when you open a image in Facebook something like this happens:- suppose you are at your homepage on Facebook:- the URL is https://www.facebook.com/ now if you open a image it gets opened in new modal like window and URL changes to:- https://www.facebook.com/photo.php?fbid=10151125374887397&set=a.338008237396.161268.36922302396&type=1&theater As far as I know in any common case a modal overlay would have kept the url in the address bar the same , My question is how does facebook / pintrest achieve this behaviour of not re-loading the whole page but still achieving the change in the address bar. Is there any jquery or javascript plugin for this?

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  • Resources on learning to program in machine code?

    - by AceofSpades
    I'm a student, fresh into programming and loving it, from Java to C++ and down to C. I moved backwards to the barebones and thought to go further down to Assembly. But, to my surprise, a lot of people said it's not as fast as C and there is no use. They suggested learning either how to program a kernel or writing a C compiler. My dream is to learn to program in binary (machine code) or maybe program bare metal (program micro-controller physically) or write bios or boot loaders or something of that nature. The only possible thing I heard after so much research is that a hex editor is the closest thing to machine language I could find in this age and era. Are there other things I'm unaware of? Are there any resources to learn to program in machine code? Preferably on a 8-bit micro-controller/microprocessor. This question is similar to mine, but I'm interested in practical learning first and then understanding the theory.

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