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iPhone , core data, whether NSManagedObject use lazy load mechanism when it was create ?

- by Robin

Hi, all, I have use core data in app, I have definite a class that most like as follows: @interface Master : NSManagedObject { } @property (nonatomic, retain) NSSet* Details; .... the entity Master contains a property 'Details' that is relate to another table, this is typical Master-Details relationship, I trace the app , but I find a issue that the property 'Details' value was construct even it never be invoked ..... but I consider that the core data 'should' use some lazy mechanism to improve performance, or maybe I miss some configure step ? because the Master entity contains at least five 'Child' table properties , I have to consider this problem before use the core data .... any help ? thanks for your time!

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Where is the best place to put <script> tags in HTML markup?

- by mipadi

When embedding JavaScript in an HTML document, where is the best place to put the <script> tags and included JavaScript? I seem to recall that you are not supposed to place these in the <head> section, but placing at the beginning of the <body> section is bad, too, since the JavaScript will have to be parsed before the page is rendered completely (or something like that). This seems to leave the end of the <body> section as a logical place for <script> tags. So, where is the best place to put the <script> tags? (This question references this question, in which it was suggested that JavaScript function calls should be moved from <a> tags to <script> tags. I'm specifically using JQuery, but more general answers are also appropriate.)

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jQuery textbox required validation based on another text box having text

- by doug

Pretty basic question, however, I am very new to jQuery and javascript in general. I have a jQuery validation that is requiring a text box to have text in it, if a checkbox is checked. <script type="text/javascript"> $(document).ready(function () { $("form").validate( { rules: { Comments: { required: "#IsAbnormal:checked" } }, messages: { Comments: { required: "Comments are required" } }, onkeyup: false, wrapper: "", errorLabelContainer: "#ErrorMessageBox" }); }); Pretty straight forward, if you check the IsAbnormal checkbox, it will throw a validation if there are no comments. What I am trying to do is require a textbox based on if another text box has any text in it, for instance require the old password if a user enters a new password into a textbox. Is there an easy way to get the required: "#NewPassword:NotBlank" to work?

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Measuring the time to create and destroy a simple object

- by portoalet

From Effective Java 2nd Edition Item 7: Avoid Finalizers "Oh, and one more thing: there is a severe performance penalty for using finalizers. On my machine, the time to create and destroy a simple object is about 5.6 ns. Adding a finalizer increases the time to 2,400 ns. In other words, it is about 430 times slower to create and destroy objects with finalizers." How can one measure the time to create and destroy an object? Do you just do: long start = System.nanoTime(); SimpleObject simpleObj = new SimpleObject(); simpleObj.finalize(); long end = System.nanoTime(); long time = end - start;

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ruby parametrized regular expression

- by astropanic

I have a string like "{some|words|are|here}" or "{another|set|of|words}" So in general the string consists of an opening curly bracket,words delimited by a pipe and a closing curly bracket. What is the most efficient way to get the selected word of that string ? I would like do something like this: @my_string = "{this|is|a|test|case}" @my_string.get_column(0) # => "this" @my_string.get_column(2) # => "is" @my_string.get_column(4) # => "case" What should the method get_column contain ?

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C++ Multiple Inheritance Question

- by John

The scenario generating this is quite complex so I'll strip out a few pieces and give an accurate representation of the classes involved. /* This is inherited using SI by many classes, as normal */ class IBase { virtual string toString()=0; }; /* Base2 can't inherit IBase due to other methods on IBase which aren't appropriate */ class Base2 { string toString() { ... } }; /* a special class, is this valid? */ class Class1 : public IBase, public Base2 { }; So, is this valid? Will there be conflicts on the toString? Or can Class1 use Base2::toString to satisfy IBase? Like I say there are lots of other things not shown, so suggestions for major design changes on this example are probably not that helpful... though any general suggestions/advice are welcome.

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Should I use "id" or "unique username"?

- by roa3

I am using PHP, AS3 and mysql. I have a website. A flash(as3) website. The flash website store the members' information in mysql database through php. In "members" table, i have "id" as the primary key and "username" as a unique field. Now my situation is: When flash want to display a member's profile. My questions: Should Flash pass the member "ID" or "username" to php to process the mysql query? Is there any different passing the "id" or "username"? Which one is more secure? Which one you recommend? I would like to optimize my website in terms of security and performance.

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<= vs < when proving big-o notation

- by user600197

We just started learning big-o in class. I understand the general concept that f(x) is big-o of g(x) if there exists two constants c,k such that for all xk |f(x)|<=c|g(x)|. I had a question whether or not it is required that we include the <= to sign or whether it is just sufficient to put the < sign? For example: suppose f(x)=17x+11 and we are to prove that this is O(x^2). Then if we take c=28 and xk=1 we know that 17x+11<=28x^2. So since we know that x will always be greater than 1 this implies that 28x^2 will always be greater than 17x+11. So, do we really need to include the equal sign (<=) or is it okay if we just write (<)? Thanks in advance.

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[PHP] background upload

- by Robijntje007

I am working with a form that allows me to upload files via a local folder and FTP. So I want to move files over ftp (which already works) Because of performance reasons I chose this process to run in the background so I use nfcftpput (linux) In CLI the following command works perfectly: ncftpput-b-u name -p password -P 1980 127.0.0.1 /upload/ /home/Downloads/upload.zip (Knowing that the b-parameter triggers background process) But if I run it via PHP it does not work (without the-b parameter it does) PHP code: $cmd = "ncftpput -b -u name -p password -P 1980 127.0.0.1 /upload/ /home/Downloads/upload.zip"; $return = exec($cmd);

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Read XML from an XDocument with silverlight

- by user625310

Hi I have managed to load an XDocument with xml data from this link http://go.yr.no/go/e/main/http://www.yr.no/place/Norway/Telemark/Sauherad/Gvarv/forecast.xml. I am using C# and .Net in Blend and producing a web app (ie some of the normal .Net functions is not included in the silverlight plugin). I have researched this a lot but can not figure out: how to put the "text" in the link node in a string variable and how to all put the "-11" from ? in a array and link it to the "time from"? I think i have to use LINQ, but the stuff on MSDN and other tutorials is confusing and to general. huge thank in advance Regards Arnt I am sorry to ask such novice questions, but i have searched a lot. Also please excuse the typos, English is not my first language. Huge thank in advance Arnt

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Can I tell Borland C++ Builder to copy a file somewhere else after it is built?

- by MrVimes

I have two computers. One is intended to be left 'free' for high-performance activities (such as playing games) The other is my 'all purpose' computer where I install all the apps I use for creating things, and so on. On the second computer I use Codegear C++ Builder to work on an app that I use on the first computer. If I have BCB compile to comp 1 it is hopeless. It becomes unresponsive. It compiles locally very quickly. So what I do is compile locally and then copy the exe to the other machine. Well, I'm all for streamlining processes, so I want a way to compile on PC2 and use on PC1 without any intermediate steps. So is it possible to have BCB do the compiling on PC2 and create a local exe file, then copy the file to PC 1?

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"Single NSMutableArray" vs. "Multiple C-arrays" --Which is more Efficient/Practical?

- by RexOnRoids

Situation: I have a DAY structure. The DAY structure has three variables or attributes: a Date (NSString*), a Temperature (float), and a Rainfall (float). Problem: I will be iterating through an array of about 5000 DAY structures and graphing a portion of these onto the screen using OpenGL. Question: As far as drawing performance, which is better? I could simply create an NSMutableArray of DAY structures (NSObjects) and iterate on the array on each draw call -- which I think would be hard on the CPU. Or, I could instead manually manage three different C-Arrays -- One for the Date String (2-Dimensional), One for the temperature (1-Dimensional) and One for the Rainfall (1-Dimensional). I could keep track of the current Day by referencing the current index of the iterated C-Arrays.

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CAD/CAM without C++

- by zaladane

Hello, Is it possible to do CAD/CAM software without having to use C++? My company developed their software with c/C++ but that was more than 10 years ago. Today,there is a lot of legacy code that switching would force us to get rid of but i was wondering what the actual risks are. We have a lot of mathematical algorithms for toolpath calculations, feature recognition and simulation and 3D Rendering and i was wondering if C# can handles all of that without great performance loss. Is it a utopia to rewrite such algorithms in c# or should that language only deal with UI. We are not talking about game development here (Halo 3 or Call Of Duty) so how much processing does CAD/CAM really need? Can anybody enlighten me on this matter? Most of my colleagues are hardcore C++ programmers and although i program in c++ i love .NET but i am having a hard time selling .NET to them other than basic UI. Does it make sense to consider switching to .NET in such a field, or is it just not a wise idea? Thank you

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Cleanest way to store lists of filter coefficients in a C header

- by Nick T

I have many (~100 or so) filter coefficients calculated with the aid of some Matlab and Excel that I want to dump into a C header file for general use, but I'm not sure what the best way to do this would be. I was starting out as so: #define BUTTER 1 #define BESSEL 2 #define CHEBY 3 #if FILT_TYPE == BUTTER #if FILT_ROLLOFF == 0.010 #define B0 256 #define B1 512 #define B2 256 #define A1 467 #define A2 -214 #elif FILT_ROLLOFF == 0.015 #define B0 256 #define B1 512 // and so on... However, if I do that and shove them all into a header, I need to set the conditionals (FILT_TYPE, FILT_ROLLOFF) in my source before including it, which seems kinda nasty. What's more, if I have 2+ different filters that want different roll-offs/filter types it won't work. I could #undef my 5 coefficients (A1-2, B0-2) in that coefficients file, but it still seems wrong to have to insert an #include buried in code.

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Background upload in PHP

- by Robijntje007

I am working with a form that allows me to upload files via a local folder and FTP. So I want to move files over ftp (which already works) Because of performance reasons I chose this process to run in the background so I use nfcftpput (linux) In CLI the following command works perfectly: ncftpput-b-u name -p password -P 1980 127.0.0.1 /upload/ /home/Downloads/upload.zip (Knowing that the b-parameter triggers background process) But if I run it via PHP it does not work (without the-b parameter it does) PHP code: $cmd = "ncftpput -b -u name -p password -P 1980 127.0.0.1 /upload/ /home/Downloads/upload.zip"; $return = exec($cmd);

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"Socket operation on non-socket" error due to strange sytax

- by Robert S. Barnes

I ran across the error Socket operation on non-socket in some of my networking code when calling connect and spent a lot of time trying to figure out what was causing it. I finally figured out that the following line of code was causing the problem: if ((sockfd = socket( ai->ai_family, ai->ai_socktype, ai->ai_protocol) < 0)) { See the problem? Here's what the line should look like: if ((sockfd = socket( ai->ai_family, ai->ai_socktype, ai->ai_protocol)) < 0) { What I don't understand is why the first, incorrect line doesn't produce a warning. To put it another way, shouldn't the general form: if ( foo = bar() < baz ) do_somthing(); look odd to the compiler, especially running with g++ -Wall -Wextra? If not, shouldn't it at least show up as "bad style" to cppcheck, which I'm also running as part of my compile?

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Apache2 on Ubuntu Server w/ CGI, FastCGI, mod_php

- by illegal3alien

I've looked at various websites on configuring Apache with cgi and can't get mod_fcgid to work. It works fine using mod_php5, but I wanted to compare performance using cgi and fastcgi. I tried methods using FGCIWrapper among various other techniques and the only one that didn't result in an unlogged 403 or download of the file was using "Action application/x-httpd-php /usr/bin/php-cgi" When trying to configure mod_fcgid the file normally just started a download of an unprocessed file. I used wget to check headers and type was "application/x-httpd-php" At one point I was able to get to the page, but it resulted in a 403, which was listed in access.log, but not error.log (I was told it should be in there too) I tried to get it working on a fresh install of Ubuntu Server 10.04 LTS and 10.10 and had the same results on both, so I'm not doing something correctly in terms of configuration. I tried virtualmin and could only get mod_php to work. The page just prompted a download when selecting cgi or fcgi from the control panel.

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Giving Users an Option Between UDP & TCP?

- by cam

After studying TCP/UDP difference all week, I just can't decide which to use. I have to send a large amount of constant sensor data, while at the same time sending important data that can't be lost. This made a perfect split for me to use both, then I read a paper (http://www.isoc.org/INET97/proceedings/F3/F3_1.HTM) that says using both causes packet/performance loss in the other. Is there any issue presented if I allow the user to choose which protocol to use (if I program both server side) instead of choosing myself? Are there any disadvantages to this? The only other solution I came up with is to use UDP, and if there seems to be too great of loss of packets, switch to TCP (client-side).

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How to add user customized data to database?

- by CSharperWithJava

I am trying to design a sqlite database that will store notes. Each of these notes will have common fields like title, due date, details, priority, and completed. In addition though, I would like to add data for more specialized notes like price for shopping list items and author/publisher data for books. I also want to have a few general purpose fields that users can fill with whatever text data they want. How can I design my database table in this case? I could just have a field for each piece of data for every note, but that would waste a lot of fields and I'd like to have other options and suggestions.

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Can the lock function be used to implement thread-safe enumeration?

- by Daniel

I'm working on a thread-safe collection that uses Dictionary as a backing store. In C# you can do the following: private IEnumerable<KeyValuePair<K, V>> Enumerate() { if (_synchronize) { lock (_locker) { foreach (var entry in _dict) yield return entry; } } else { foreach (var entry in _dict) yield return entry; } } The only way I've found to do this in F# is using Monitor, e.g.: let enumerate() = if synchronize then seq { System.Threading.Monitor.Enter(locker) try for entry in dict -> entry finally System.Threading.Monitor.Exit(locker) } else seq { for entry in dict -> entry } Can this be done using the lock function? Or, is there a better way to do this in general? I don't think returning a copy of the collection for iteration will work because I need absolute synchronization.

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Nested loop with dependent bounds trip count

- by aaa

hello. just out of curiosity I tried to do the following, which turned out to be not so obvious to me; Suppose I have nested loops with runtime bounds, for example: t = 0 // trip count for l in 0:N for k in 0:N for j in max(l,k):N for i in k:j+1 t += 1 t is loop trip count is there a general algorithm/way (better than N^4 obviously) to calculate loop trip count? I am working on the assumption that the iteration bounds depend only on constant or previous loop variables.

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FlockDB - What is it? And best cases for it uses.

- by Guru

Just came across FlockDB graph database. Details at github /flockDB. Twitter claims it uses FlockDB for the following: Twitter runs FlockDB on a large cluster of machines. we use it to store social graphs (who follows whom, who blocks whom) and secondary indices at twitter. At first glance, setup and trying it doesn't look straight forward. Have anyone already used it / setup this? If so, please answer the following general queries. What kind of applications is it better suited for? (Twitter claims it is simple and very rough, it remains to see what it meant though) How is FlockDB better than other graph db / noSQL db. Have you setup FlockDB, used it for a application? Early advices any? Note: I am evaluating the FlockDB and other graph databases mainly for learning them. Perhaps, I will build an application for that.

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Controlling read and write access width to memory mapped registers in C

- by srking

I'm using and x86 based core to manipulate a 32-bit memory mapped register. My hardware behaves correctly only if the CPU generates 32-bit wide reads and writes to this register. The register is aligned on a 32-bit address and is not addressable at byte granularity. What can I do to guarantee that my C (or C99) compiler will only generate full 32-bit wide reads and writes in all cases? For example, if I do a read-modify-write operation like this: volatile uint32_t* p_reg = 0xCAFE0000; *p_reg |= 0x01; I don't want the compiler to get smart about the fact that only the bottom byte changes and generate 8-bit wide read/writes. Since the machine code is often more dense for 8-bit operations on x86, I'm afraid of unwanted optimizations. Disabling optimizations in general is not an option.

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Advise on starting a new job

- by Sisiutl

I hope this isn't too off-topic, but in a week I will start a new job at a manufacturing company managing the development of a new eCommerce site. The company scores about a 3 on the "Joel" test. I will inherit 3 programmers who developed the company web site and do general IT programming. I have the grey hair and credentials to have their initial respect but I'm an engineer, not a manager. I'm looking for practical advise - particularly for the first 90 days - on how to establish myself, keep the team together, and move forward.

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Detecting similar words among n text documents

- by javanes

Hi; I have n documents and want to find common words that are included in these documents. For example I want to say (n-3) documents include the word "web". Certainly I can do this by basic data structures but there maybe efficient algorithm or a way to handle same words with different suffix. Is there any algorithm for such purposes? I am unfamiliar with datamining world. In general manner is there a term used for efforts of finding similarities between different documents? If there is then I will make my research easily. Thanks.

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