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  • Interpreters: How much simplification?

    - by Ray
    In my interpreter, code like the following x=(y+4)*z echo x parses and "optimizes" down to four single operations performed by the interpreter, pretty much assembly-like: add 4 to y multiply <last operation result> with z set x to <last operation result> echo x In modern interpreters (for example: CPython, Ruby, PHP), how simplified are the "opcodes" for which are in end-effect run by the interpreter? Could I achieve better performance when trying to keep the structures and commands for the interpreter more complex and high-level? That would be surely a lot harder, or?

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  • Why does Java not have any destructor like C++?

    - by Abhishek Jain
    Java has its own garbage collection implementation so it does not require any destructor like C++ . This makes Java developer lazy in implementing memory management. And Garbage Collection is very expensive. Still we can have destructor along with garbage collector where developer can free resources and which can save garbage collector's work. This might improves the performance of application. Why does Java not provide any destructor kind of mechanism? Developer does not have control over GC but he/she can control or create object. Then why not give them ability to destruct the objects?

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  • How to organise a php based website

    - by bsandrabr
    I am putting my php /mysql website up and this is my scenario The users are grouped into sites each site with their own unique database. There will be about 40 users per site. the two options I'm trying to decide between are have a central website running the php and directing the users off to their own database using sub domains for each user each with their own php in htdocs I dont even know if 2 is possible/stupid but if it was, would it make any difference to performance as they're all being run by the same server. Any other ideas/ advice much appreciated as I want to organise it the best way from the start

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  • What parallel programming model do you recommend today to take advantage of the manycore processors

    - by Doctor J
    If you were writing a new application from scratch today, and wanted it to scale to all the cores you could throw at it tomorrow, what parallel programming model/system/language/library would you choose? Why? I am particularly interested in answers along these axes: Programmer productivity / ease of use (can mortals successfully use it?) Target application domain (what problems is it (not) good at?) Concurrency style (does it support tasks, pipelines, data parallelism, messages...?) Maintainability / future-proofing (will anybody still be using it in 20 years?) Performance (how does it scale on what kinds of hardware?) I am being deliberately vauge on the nature of the application in anticipation of getting good general answers useful for a variety of applications.

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  • AES acceleration for Java

    - by chris_l
    I want to encrypt/decrypt lots of small (2-10kB) pieces of data. The performance is ok for now: On a Core2Duo, I get about 90 MBytes/s AES256 (when using 2 threads). But I may need to improve that in the future - or at least reduce the impact on the CPU. Is it possible to use dedicated AES encryption hardware with Java (using JCE, or maybe a different API)? Would Java take advantage of special CPU features (SSE5?!), if I get a better CPU? Or are there faster JCE providers? (I tried SunJCE and BouncyCastle - no big difference.) Other possiblilities?

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  • Flex 4.5 - to long build process

    - by Idob
    We are developing an app using flex 4.5. The app runs just fine (no performance issues at all) but it takes us forever to compile and build it. A minor change, like just add a comment or press enter in an mxml file and rebuild takes about 3 minutes. You just cant work that way. It is a large project with about 1300 files. We also use Parsley as IOC container and a beat of cairngorm navigation. We also use Maven (Flex mojos) but I am talking about a normal eclipse build (Ctrl + B). We separated some of the code to a different SWC and all of our graphics are stored in a different resource SWF. Please, Do you have any suggestions? Regards, Ido

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  • Speed up the loop operation in R

    - by Kay
    Hi, i have a big performance problem in R. I wrote a function that iterates over an data.frame object. It simply adds a new col to a data.frame and accumulate sth. (simple operation). The data.frame has round about 850.000 rows. My PC is still working about 10h now and i have no idea about the runtime. dayloop2 <- function(temp){ for (i in 1:nrow(temp)){ temp[i,10] <- i if (i > 1) { if ((temp[i,6] == temp[i-1,6]) & (temp[i,3] == temp[i-1,3])) { temp[i,10] <- temp[i,9] + temp[i-1,10] } else { temp[i,10] <- temp[i,9] } } else { temp[i,10] <- temp[i,9] } } names(temp)[names(temp) == "V10"] <- "Kumm." return(temp) } Any ideas how to speed up this operation ?

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  • EJB3.1 Remote invocation - is it distributed automatically? is it expensive?

    - by Hank
    I'm building a JEE6 application with performance and scalability in the forefront of my mind. Business logic and JPA2-facade is held in stateless session beans (EJB3.1). As of right now, the SLSBs implement only @Remote-interfaces. When a bean needs to access another bean, it does so via RMI. My reasoning behind this is the assumption that, once the application runs on a bunch of clustered application servers, the RMI-part allows the execution to be distributed across the whole cluster automagically. Is that a correct assumption? I'm fine with dealing with the downsides of that (objects lose entityManager session, pass-by-value), at least I think so. But I am wondering if constant remote invocation isn't adding more load then necessary.

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  • Lock HTML select element, allow value to be sent on submit

    - by ILMV
    I have a select box (for a customer field) on a complex order form, when the user starts to add lines to the order they should not be allowed to change the customer select box (unless all lines are deleted). My immediate thought was that I could use the disabled attribute, but when the box is disabled the selected value is no longer passed to the target. When the problem arose a while ago one of the other developers worked around this by looping through all the options and disabling all but the selected option, and sure enough the value was passed to the target and we've been using since. But now I'm looking for a proper solution, I don't want to loop through all the options because are data is expanding and it's starting to introduce performance issues. I'd prefer not to enable this / all the elements when the submit button is hit. How can I lock the input, whilst maintaining the selected option and passing that value to the target script? I would prefer a non-JavaScript solution if possible, but if needed we are running jQuery 1.4.2 so that could be used.

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  • Hibernate criteria with projection not performing query for @OneToMany mapping

    - by Josh
    I have a domain object, Expense, that has a field called initialFields. It's annotated as so: @OneToMany(fetch = FetchType.EAGER, cascade = { CascadeType.ALL }, orphanRemoval = true) @JoinTable(blah blah) private final List<Field> initialFields; Now I'm trying to use Projections in order to only pull certain fields for performance reasons, but when doing so the initialFields field is always null. It's the only OneToMany field and the only field I am trying to retrieve with the projection that is behaving this way. If I use a regular HQL query initialFields is populated appropriately, but of course I can't limit the fields. Anyone ever seen anything like this?

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  • How do you handle passwords or credentials for standalone applications?

    - by Abel Morelos
    Let's say that you have a standalone application (a Java application in my case) and that this application has a configuration file (a XML file in my case) where you store the credentials (user and password) for a bunch of databases you need to connect. Everything works great, but now you discover (or your are given a new requirement like me) that you have to put this application in a different server and that you can't have these credentials in the configuration files because of security and/or compliance considerations. I'm considering to use data sources hosted in the application server (a WAS server), but I think this could have poor performance and maybe it's not the best approach since I'm connecting from a standalone application. I was also considering to use some sort of encryption, but I would like to keep things as simple as possible. How would you handle this case? Where would you put these credentials or protect them from being compromised? Or how would you connect to your databases in this scenario?

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  • database design suggesion

    - by Bharanikumar
    Hi , am going to start new travel site, I want some advise from guru's regarding database design , Things coming to picture are, Book taxi online , This is the core idea, So i like to implement lot of jquery,ajax stuff in my site , Main thing site must run veryt fast,safe,security, In mysql , which typw shall i use, MYISAM OR INNODB Which is best type for ajax works, fast,safe ,secure ,performance view . This is my demo site, Just look this site, i implemented some ajax stuff here, my-url In this site please choose the postcode in the taxifrom tab, It ask you value please enter, just enter nw7 , See How long it will take for response,some time no response and system goes to hang or idle mode, Also please look the diversion , select No diversion, There you will list of textbox, enter the nw3 then hit the search icon , See after 80seconds only , you will get response from DB, See this too bad response ... This is DB , my Database type if myisam ,no idexing , no fulltext and nothing...no constraints, So please advise me , which database type i choose, Myisam or innodb, Thanks Bharanikumar

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  • std::for_each on a member function with 1 argument

    - by Person
    I'm wondering how to implement what is stated in the title. I've tried something like... std::for_each( a.begin(), a.end(), std::mem_fun_ref( &myClass::someFunc ) ) but I get an error saying that the "term" (I"m assuming it means the 3rd argument) doesn't evaluate to a function with 1 argument, even though someFunc does take one argument - the type of the objects stored in a. I'm wondering if what I'm trying to do is possible using the standard library (I know I can do it easily using boost). P.S. Does using for_each and mem_fun_ref have any performance implications in comparison to just iterating through a manually and passing the object to someFunc?

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  • Possible to InvalidateVisual() on a given region instead of entire WPF control?

    - by Scott Bilas
    I have a complex WPF control that draws a lot of primitives in its OnRender (it's sort of like a map). When a small portion of it changes, I'd only like to re-issue render commands for the affected elements, instead of running the entire OnRender over. While I'm fine with my OnRender function's performance on a resize or whatever, it's not fast enough for mouse hover-based highlighting of primitives. Currently the only way I know how to force a screen update is to call InvalidateVisual(). No way to send in a dirty rect region to invalidate. Is the lowest granularity of WPF screen composition the UI element? Will I need to do my renders of primitives into an intermediate target and then have that use InvalidateVisual() to update to the screen?

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  • Javascript - Determine if String Is In List

    - by Emtucifor
    In SQL we can see if a string is in a list like so: Column IN ('a', 'b', 'c') What's a good way to do this in javascript? I realize one can use the switch function: var str = 'a' var flag = false; switch (str) { case 'a': case 'b': case 'c': flag = true; default: } if (thisthing || thatthing || flag === true) { // do something } But this is a horrible mess. It's also clunky to do this: if (thisthing || thatthing || str === 'a' || str === 'b' || str = 'c') { // do something } And I'm not sure about the performance or clarity of this: if (thisthing || thatthing || {a:1, b:1, c:1}[str]) { // do something } Any ideas?

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  • What is the preferred way to associate css styles with GWT widgets (using UiBinder)?

    - by smallbec
    From the GWT page (http://code.google.com/webtoolkit/doc/latest/DevGuideUiCss.html#cssfiles), it mentions 2 ways (for modern application): Using a CssResource contained within a ClientBundle. Using an inline element in a UiBinder template. Modern GWT applications typically use a combination of CssResource and UiBinder. So my question is, when should I use a css file and create a CssResource for it, and when should I define styles directly in the ui.xml file using <ui:style>? Are there any performance implication (i.e. resource size to download on the client) with either of these ways?

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  • Android: How to invalidate multiple parts of screen

    - by user342731
    I need to be able to selectively invalidate multiple (about 20) rectangles on the screen for performance reasons, so tried the following: Vector<Rect> myRects = new Vector<Rect>(); // ... add some Rects to myRects for (Rect r : myRects) { invalidate(r); } However this seems to invalidates a union of all the Rect's, forming one large rectangle which covers all of small ones I'm trying to invalidate. How can one invalidate multiple areas on the screen, and only those areas?

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  • How do I use compiler intrinsic __fmul_?

    - by Eric Thoma
    I am writing a massively parallel GPU application. I have been optimizing it by hand. I received a 20% performance increase with _fdividef(x, y), and according to The Cuda C Programming Guide (section C.2.1), using similar functions for multiplication and adding is also beneficial. The function is stated as this: "_fmulrn,rz,ru,rd". __fdividef(x,y) was not stated with the arguments in brackets. I was wondering, what are those brackets? If I run the simple code: int t = __fmul_(5,4); I a compiler error about how _fmul is undefined. I have the CUDA runtime included, so I don't think it is a setup thing; rather it is something to do with those square brackets. How do I correctly use this function? Thank you.

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  • postgreSQL - pg_class question

    - by Sachin Chourasiya
    PostgreSQL stores statistics about tables in the system table called pg_class. The query planner accesses this table for every query. These statistics may only be updated using the analyze command. If the analyze command is not run often, the statistics in this table may not be accurate and the query planner may make poor decisions which can degrade system performance. Another strategy is for the query planner to generate these statistics for each query (including selects, inserts, updates, and deletes). This approach would allow the query planner to have the most up-to-date statistics possible. Why postgres always rely on pg_class instead?

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  • Data access strategy for a site like SO - sorted SQL queries and simultaneous updates that affect th

    - by Kaleb Brasee
    I'm working on a Grails web app that would be similar in access patterns to StackOverflow or MyLifeIsAverage - users can vote on entries, and their votes are used to sort a list of entries based on the number of votes. Votes can be placed while the sorted select queries are being performed. Since the selects would lock a large portion of the table, it seems that normal transaction locking would cause updates to take forever (given enough traffic). Has anyone worked on an app with a data access pattern such as this, and if so, did you find a way to allow these updates and selects to happen more or less concurrently? Does anyone know how sites like SO approach this? My thought was to make the sorted selects dirty reads, since it is acceptable if they're not completely up to date all of the time. This is my only idea for possibly improving performance of these selects and updates, but I thought someone might know a better way.

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  • Will GTK's pango and cairo work well in Cocoa and MFC applications.

    - by Lothar
    I'm writing a GUI program and decided to go native on all platforms. But for all the stuff i need to draw myself i would like to use the same drawing routines because font and unicode handling is so difficult and complex. Do you see any negative points in useing Pango/Cairo. Well on MacOSX i havent succeded installing Pango/Cairo yet. Looks like a bad Omen. I would also like to hear about the performance penality. The first time i looked at Pango i thought, yes thats the reason why Software is still getting despite better hardware.

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  • asp.net membership provider api. usability. best-practice

    - by Andrew Florko
    Hello everybody, Membership/Role/Profile providers API appeared in early days of asp.net Nearly everytime I can't live with standard API & have to add some extra functionality (for sorting, retrieving e.t.c.). I also have to use different database structure often (with foreign key to some tables for example) or think about performance improvements. These considerations forced teams I took part in to build own providers but I can't stand to implement providers API (because we don't use 70% of standard functionality at least). Moreover, providers that were built for exact projects were rarely reused. I wonder if someone found swiss-knife early-days-API providers implementation that is usefull for any kind of project without refactoring... Or do you use your own implementations of early-days-API's Or may be you abandon standard architecture and use lightweight implementations ? Thank you in advance

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  • Mysql query taking too much time

    - by aditya
    I have problem related to mysql database. i am linux webserver admin and i am facing a problem with a mysql query. The database is very small. I tried to track in logs and found that a query is taking minimum 5 sec to respond . The first page of site is coming from the database. Client are using cms. when the server gets some number of hits database server starts to give response very slowly and wait time increases from 5 sec to several seconds. I checked slow query logs { Query_time: 11.480138 Lock_time: 0.003837 Rows_sent: 921 Rows_examined: 3333 SET timestamp=1346656767; SELECT `Tender`.`id`, `Tender`.`department_id`, `Tender`.`title_english`, `Tender`.`content_english`, `Tender`.`title_hindi`, `Tender`.`content_hindi`, `Tender`.`file_name`, `Tender`.`start_publish`, `Tender`.`end_publish`, `Tender`.`publish`, `Tender`.`status`, `Tender`.`createdBy`, `Tender`.`created`, `Tender`.`modifyBy`, `Tender`.`modified` FROM `mcms_tenders` AS `Tender` WHERE `Tender`.`department_id` IN ( 31, 33, 32, 30 ); } Every line in the log is same only there is diff in Query time. Is there any way tweak the performance?

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  • foreign key constraints on primary key columns - issues ?

    - by zzzeek
    What are the pros/cons from a performance/indexing/data management perspective of creating a one-to-one relationship between tables using the primary key on the child as foreign key, versus a pure surrogate primary key on the child? The first approach seems to reduce redundancy and nicely constrains the one-to-one implicitly, while the second approach seems to be favored by DBAs, even though it creates a second index: create table parent ( id integer primary key, data varchar(50) ) create table child ( id integer primary key references parent(id), data varchar(50) ) pure surrogate key: create table parent ( id integer primary key, data varchar(50) ) create table child ( id integer primary key, parent_id integer unique references parent(id), data varchar(50) ) the platforms of interest here are Postgresql, Microsoft SQL Server.

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  • P/Invoke or C++/CLI for wrapping a C library

    - by Ian G
    Have a moderate size (40-odd function) C API that needs to be called from a C# project. The functions logically break up to form a few classes that will be API presented to the rest of the project. Are there any objective reasons to prefer P/Invoke or C++/CLI for the interoperability underneath that API, in terms of robustness, maintainability, deployment, ...? The issues I could think of that might be, but aren't problematic are: C++/CLI will require an separate assembly, the P/Invoke classes can be in the main assembly. (We've already got multiple assemblies and there'll be the C dlls anyway so not a major issue). Performance doesn't seem differ noticeable between the two methods. Issues that I'm not sure about are: My feeling is C++/CLI will be easier to debug if there's inter-op problem, is this true? Language familiarity enough people know C# and C++ but knowledge of details of C++/CLI are rarer here. Anything else?

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