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  • Reading email address from contacts fails with weird memory issue

    - by CapsicumDreams
    Hi all, I'm stumped. I'm trying to get a list of all the email address a person has. I'm using the ABPeoplePickerNavigationController to select the person, which all seems fine. I'm setting my ABRecordRef personDealingWith; from the person argument to - (BOOL)peoplePickerNavigationController:(ABPeoplePickerNavigationController *)peoplePicker shouldContinueAfterSelectingPerson:(ABRecordRef)person property:(ABPropertyID)property identifier:(ABMultiValueIdentifier)identifier { and everything seems fine up till this point. The first time the following code executes, all is well. When subsequently run, I can get issues. First, the code: // following line seems to make the difference (issue 1) // NSLog(@"%d", ABMultiValueGetCount(ABRecordCopyValue(personDealingWith, kABPersonEmailProperty))); // construct array of emails ABMultiValueRef multi = ABRecordCopyValue(personDealingWith, kABPersonEmailProperty); CFIndex emailCount = ABMultiValueGetCount(multi); if (emailCount 0) { // collect all emails in array for (CFIndex i = 0; i < emailCount; i++) { CFStringRef emailRef = ABMultiValueCopyValueAtIndex(multi, i); [emailArray addObject:(NSString *)emailRef]; CFRelease(emailRef); } } // following line also matters (issue 2) CFRelease(multi); If compiled as written, the are no errors or static analysis problems. This crashes with a *** -[Not A Type retain]: message sent to deallocated instance 0x4e9dc60 error. But wait, there's more! I can fix it in either of two ways. Firstly, I can uncomment the NSLog at the top of the function. I get a leak from the NSLog's ABRecordCopyValue every time through, but the code seems to run fine. Also, I can comment out the CFRelease(multi); at the end, which does exactly the same thing. Static compilation errors, but running code. So without a leak, this function crashes. To prevent a crash, I need to haemorrhage memory. Neither is a great solution. Can anyone point out what's going on?

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  • Hardware acceleration issue with WPF application - Analyzing crash dumps

    - by Appu
    I have a WPF application crashing on the client machine. My initial analysis shows that this is because of H/W acceleration and disabling H/W acceleration at a registry level solves the issue. Now I have to make sure that this is caused because of H/W acceleration. I have the crash dumps available which has a stack trace, 9c52b020 80636ac7 9c52b0bc e1174818 9c52b0c0 nt!_SEH_prolog+0x1a 9c52b038 806379d6 e10378a4 9c52b0bc e1174818 nt!CmpQuerySecurityDescriptorInfo+0x23 9c52b084 805bfe5b e714b160 00000001 9c52b0bc nt!CmpSecurityMethod+0xce 9c52b0c4 805c01c8 e714b160 9c52b0f0 e714b15c nt!ObpGetObjectSecurity+0x99 9c52b0f4 8062f28f e714b160 8617f008 00000001 nt!ObCheckObjectAccess+0x2c 9c52b140 8062ff30 e1038008 0066a710 cde2b714 nt!CmpDoOpen+0x2d5 9c52b340 805bf488 0066a710 0066a710 8617f008 nt!CmpParseKey+0x5a6 9c52b3b8 805bba14 00000000 9c52b3f8 00000240 nt!ObpLookupObjectName+0x53c 9c52b40c 80625696 00000000 8acad448 00000000 nt!ObOpenObjectByName+0xea 9c52b508 8054167c 9c52b828 82000000 9c52b5ac nt!NtOpenKey+0x1c8 9c52b508 80500699 9c52b828 82000000 9c52b5ac nt!KiFastCallEntry+0xfc 9c52b58c 805e701e 9c52b828 82000000 9c52b5ac nt!ZwOpenKey+0x11 9c52b7fc 805e712a 00000002 805e70a0 00000000 nt!RtlpGetRegistryHandleAndPath+0x27a 9c52b844 805e73e3 9c52b864 00000014 9c52bbb8 nt!RtlpQueryRegistryGetBlockPolicy+0x2e 9c52b86c 805e79eb 00000003 e8af79dc 00000014 nt!RtlpQueryRegistryDirect+0x4b 9c52b8bc 805e7f10 e8af79dc 00000003 9c52b948 nt!RtlpCallQueryRegistryRoutine+0x369 9c52bb58 b8f5bca4 00000005 e6024b30 9c52bbb8 nt!RtlQueryRegistryValues+0x482 WARNING: Stack unwind information not available. Following frames may be wrong. 9c52bc00 b8f20a5b 00000005 85f4204c 85f4214c igxpmp32+0x44ca4 9c52c280 b8f1cc7b 890bd358 9c52c2b0 00000000 igxpmp32+0x9a5b 9c52c294 b8f11729 890bd358 9c52c2b0 00000a0c igxpmp32+0x5c7b 9c52c358 804ef19f 890bd040 86d2dad0 0000080c VIDEOPRT!pVideoPortDispatch+0xabf 9c52c368 bf85e8c2 9c52c610 bef6ce84 00000014 nt!IopfCallDriver+0x31 9c52c398 bf85e93c 890bd040 00232150 9c52c3f8 win32k!GreDeviceIoControl+0x93 9c52c3bc bebafc7b 890bd040 00232150 9c52c3f8 win32k!EngDeviceIoControl+0x1f 9c52d624 bebf3fa9 890bd040 bef2a28c bef2a284 igxpdx32+0x8c7b 9c52d6a0 8054167c 9c52da28 b915d000 9c52d744 igxpdx32+0x4cfa9 9c52d6a0 00000000 9c52da28 b915d000 9c52d744 nt!KiFastCallEntry+0xfc How do I ensure that crash is caused by H/W acceleration issue by looking at the above data? I am guessing VIDEOPRT!pVideoPortDispatch+0xabf indicates some error with the rendering. Is that correct? I am using WinDebug to view the crash dump.

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  • When optimizing database queries, what exactly is the relationship between number of queries and siz

    - by williamjones
    To optimize application speed, everyone always advises to minimize the number of queries an application makes to the database, consolidating them into fewer queries that retrieve more wherever possible. However, this also always comes with the caution that data transferred is still data transferred, and just because you are making fewer queries doesn't make the data transferred free. I'm in a situation where I can over-include on the query in order to cut down the number of queries, and simply remove the unwanted data in the application code. Is there any type of a rule of thumb on how much of a cost there is to each query, to know when to optimize number of queries versus size of queries? I've tried to Google for objective performance analysis data, but surprisingly haven't been able to find anything like that. Clearly this relationship will change for factors such as when the database grows in size, making this somewhat individualized, but surely this is not so individualized that a broad sense of the landscape can't be drawn out? I'm looking for general answers, but for what it's worth, I'm running an application on Heroku.com, which means Ruby on Rails with a Postgres database.

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  • Where is my python script spending time? Is there "missing time" in my cprofile / pstats trace?

    - by fmark
    I am attempting to profile a long running python script. The script does some spatial analysis on raster GIS data set using the gdal module. The script currently uses three files, the main script which loops over the raster pixels called find_pixel_pairs.py, a simple cache in lrucache.py and some misc classes in utils.py. I have profiled the code on a moderate sized dataset. pstats returns: p.sort_stats('cumulative').print_stats(20) Thu May 6 19:16:50 2010 phes.profile 355483738 function calls in 11644.421 CPU seconds Ordered by: cumulative time List reduced from 86 to 20 due to restriction <20> ncalls tottime percall cumtime percall filename:lineno(function) 1 0.008 0.008 11644.421 11644.421 <string>:1(<module>) 1 11064.926 11064.926 11644.413 11644.413 find_pixel_pairs.py:49(phes) 340135349 544.143 0.000 572.481 0.000 utils.py:173(extent_iterator) 8831020 18.492 0.000 18.492 0.000 {range} 231922 3.414 0.000 8.128 0.000 utils.py:152(get_block_in_bands) 142739 1.303 0.000 4.173 0.000 utils.py:97(search_extent_rect) 745181 1.936 0.000 2.500 0.000 find_pixel_pairs.py:40(is_no_data) 285478 1.801 0.000 2.271 0.000 utils.py:98(intify) 231922 1.198 0.000 2.013 0.000 utils.py:116(block_to_pixel_extent) 695766 1.990 0.000 1.990 0.000 lrucache.py:42(get) 1213166 1.265 0.000 1.265 0.000 {min} 1031737 1.034 0.000 1.034 0.000 {isinstance} 142740 0.563 0.000 0.909 0.000 utils.py:122(find_block_extent) 463844 0.611 0.000 0.611 0.000 utils.py:112(block_to_pixel_coord) 745274 0.565 0.000 0.565 0.000 {method 'append' of 'list' objects} 285478 0.346 0.000 0.346 0.000 {max} 285480 0.346 0.000 0.346 0.000 utils.py:109(pixel_coord_to_block_coord) 324 0.002 0.000 0.188 0.001 utils.py:27(__init__) 324 0.016 0.000 0.186 0.001 gdal.py:848(ReadAsArray) 1 0.000 0.000 0.160 0.160 utils.py:50(__init__) The top two calls contain the main loop - the entire analyis. The remaining calls sum to less than 625 of the 11644 seconds. Where are the remaining 11,000 seconds spent? Is it all within the main loop of find_pixel_pairs.py? If so, can I find out which lines of code are taking most of the time?

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  • Pattern for limiting number of simultaneous asynchronous calls

    - by hitch
    I need to retrieve multiple objects from an external system. The external system supports multiple simultaneous requests (i.e. threads), but it is possible to flood the external system - therefore I want to be able to retrieve multiple objects asynchronously, but I want to be able to throttle the number of simultaneous async requests. i.e. I need to retrieve 100 items, but don't want to be retrieving more than 25 of them at once. When each request of the 25 completes, I want to trigger another retrieval, and once they are all complete I want to return all of the results in the order they were requested (i.e. there is no point returning the results until the entire call is returned). Are there any recommended patterns for this sort of thing? Would something like this be appropriate (pseudocode, obviously)? private List<externalSystemObjects> returnedObjects = new List<externalSystemObjects>; public List<externalSystemObjects> GetObjects(List<string> ids) { int callCount = 0; int maxCallCount = 25; WaitHandle[] handles; foreach(id in itemIds to get) { if(callCount < maxCallCount) { WaitHandle handle = executeCall(id, callback); addWaitHandleToWaitArray(handle) } else { int returnedCallId = WaitHandle.WaitAny(handles); removeReturnedCallFromWaitHandles(handles); } } WaitHandle.WaitAll(handles); return returnedObjects; } public void callback(object result) { returnedObjects.Add(result); }

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  • Entity Framework 4 / POCO - Where to start?

    - by Basiclife
    Hi, I've been programming for a while and have used LINQ-To-SQL and LINQ-To-Entities before (although when using entities it has been on a Entity/Table 1-1 relationship - ie not much different than L2SQL) I've been doing a lot of reading about Inversion of Control, Unit of Work, POCO and repository patterns and would like to use this methodology in my new applications. Where I'm struggling is finding a clear, concise beginners guide for EF4 which doesn't assume knowledge of EF1. The specific questions I need answered are: Code first / model first? Pros/cons in regards to EF4 (ie what happens if I do code first, change the code at a later date and need to regenerate my DB model - Does the data get preserved and transformed or dropped?) Assuming I'm going code-first (I'd like to see how EF4 converts that to a DB schema) how do I actually get started? Quite often I've seen articles with entity diagrams stating "So this is my entity model, now I'm going to ..." - Unfortunately, I'm unclear if they're created the model in the designer, saved it to generate code then stopped any further auto-code generation -or- They've coded (POCO)? classes and the somehow imported them into the deisgner view? I suppose what I really need is an understanding of where the "magic" comes from and how to add it myself if I'm not just generating an EF model directly from a DB. I'm aware the question is a little vague but I don't know what I don't know - So any input / correction / clarification appreciated. Needless to say, I don't expect anyone to sit here and teach me EF - I'd just like some good tutorials/forums/blogs/etc. for complete entity newbies Many thanks in advance

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  • How to reliably replace a library-defined error handler with my own?

    - by sharptooth
    On certain error cases ATL invokes AtlThrow() which is implemented as ATL::AtlThrowImpl() which in turn throws CAtlException. The latter is not very good - CAtlException is not even derived from std::exception and also we use our own exceptions hierarchy and now we will have to catch CAtlException separately here and there which is lots of extra code and error-prone. Looks like it is possible to replace ATL::AtlThrowImpl() with my own handler - define _ATL_CUSTOM_THROW and define AtlThrow() to be the custom handler before including atlbase.h - and ATL will call the custom handler. Not so easy. Some of ATL code is not in sources - it comes compiled as a library - either static or dynamic. We use the static - atls.lib. And... it is compiled in such way that it has ATL::ThrowImpl() inside and some code calling it. I used a static analysis tool - it clearly shows that there're paths on which the old default handler is called. To ensure I even tried to "reimplement" ATL::AtlThrowImpl() in my code. Now the linker says it sees two declarations of ATL::AtlThrowImpl() which I suppose confirms that there's another implementation that can be called by some code. How can I handle this? How do I replace the default handler completely and ensure that the default handler is never called?

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  • DDD and MVC: Difference between 'Model' and 'Entity'

    - by Nathan Loding
    I'm seriously confused about the concept of the 'Model' in MVC. Most frameworks that exist today put the Model between the Controller and the database, and the Model almost acts like a database abstraction layer. The concept of 'Fat Model Skinny Controller' is lost as the Controller starts doing more and more logic. In DDD, there is also the concept of a Domain Entity, which has a unique identity to it. As I understand it, a user is a good example of an Entity (unique userid, for instance). The Entity has a life-cycle -- it's values can change throughout the course of the action -- and then it's saved or discarded. The Entity I describe above is what I thought Model was supposed to be in MVC? How off-base am I? To clutter things more, you throw in other patterns, such as the Repository pattern (maybe putting a Service in there). It's pretty clear how the Repository would interact with an Entity -- how does it with a Model? Controllers can have multiple Models, which makes it seem like a Model is less a "database table" than it is a unique Entity. So, in very rough terms, which is better? No "Model" really ... class MyController { public function index() { $repo = new PostRepository(); $posts = $repo->findAllByDateRange('within 30 days'); foreach($posts as $post) { echo $post->Author; } } } Or this, which has a Model as the DAO? class MyController { public function index() { $model = new PostModel(); // maybe this returns a PostRepository? $posts = $model->findAllByDateRange('within 30 days'); while($posts->getNext()) { echo $posts->Post->Author; } } } Both those examples didn't even do what I was describing above. I'm clearly lost. Any input?

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  • I have two choices of Master's classes this fall. Which is the most useful?

    - by ahplummer
    (For background purposes and context): I am a Software Engineer, and manage other Software Engineers currently. I kind of wear two hats right now: one of a programmer, and one as a 'team lead'. In this regard, I've started going back to school to get my Master's degree with an emphasis in Computer Science. I already have a Bachelor's in Computer Science, and have been working in the field for about 13 years. Our primary development environment is a Windows environment, writing in .NET, Delphi, and SQL Server. Choice #1: CST 798 DATA VISUALIZATION Course Description: Basically, this is a course on the "Processing" language: http://processing.org/ Choice #2: CST 711 INFORMATICS Course Description: (From catalog): Informatics is the science of the use and processing of data, information, and knowledge. This course covers a variety of applied issues from information technology, information management at a variety of levels, ranging from simple data entry, to the creation, design and implementation of new information systems, to the development of models. Topics include basic information representation, processing, searching, and organization, evaluation and analysis of information, Internet-based information access tools, ethics and economics of information sharing.

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  • How to get rid of the GUI access from shared library.

    - by Inso Reiges
    Hello, In my project i have a shared library with cross-platform code that provides a very convenient abstraction for a number of its clients. To be more specific, this library provides data access to encrypted files generated by main application on a number of platforms. There is a great deal of complicated code there that implements cryptographic protocols and as such is very error-prone and should be shared as much as possible across clients and platforms. However parsing all this encrypted stuff requires asking user for a number of different secrets ones in a while. The secret can be either a password, a number of shared passwords or a public key file and this list is a hot target for extension in the future. I can't really ask the user for any of those secrets beforehand from main application, because i really don't know what i need to ask for until i start working with the encrypted data directly in the library code. So i will have to create dialogs and call them from the library code. However i really see this as a bad idea, because (among other things) there is a possibility of a windows service using it and services can't have GUI access. The question is, are there any known ways or patterns to get rid of the GUI calls that are suitable for my case? Thank you.

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  • Two objects with dependencies for each other. Is that bad?

    - by Kasper Grubbe
    Hi SO. I am learning a lot about design patterns these days. And I want to ask you about a design question that I can't find an answer to. Currently I am building a little Chat-server using sockets, with multiple Clients. Currently I have three classes. Person-class which holds information like nick, age and a Room-object. Room-class which holds information like room-name, topic and a list of Persons currently in that room. Hotel-class which have a list of Persons and a list of Rooms on the server. I have made a diagram to illustrate it (Sorry for the big size!): http://i.imgur.com/Kpq6V.png I have a list of players on the server in the Hotel-class because it would be nice to keep track of how many there are online right now (Without having to iterate through all of the rooms). The persons live in the Hotel-class because I would like to be able to search for a specific Person without searching the rooms. Is this bad design? Is there another way of achieve it? Thanks.

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  • Best practices for managing updating a database with a complex set of changes

    - by Sarge
    I am writing an application where I have some publicly available information in a database which I want the users to be able to edit. The information is not textual like a wiki but is similar in concept because the edits bring the public information increasingly closer to the truth. The changes will affect multiple tables and the update needs to be automatically checked before affecting the public tables. I'm working on the design and I'm wondering if there are any best practices that might help with some particular issues. I want to provide undo capability. I want to show the user the combined result of all their changes. When the user says they're done, I need to check the underlying public data to make sure it hasn't been changed by somebody else. My current plan is to have the user work in a set of tables setup to be a private working area. Once they're ready they can kick off a process to check everything and update the public tables. Undo can be recorded using Command pattern saving to a table. Are there any techniques I might have missed or useful papers or patterns? Thanks in advance!

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  • Writing catch block with cleanup operations in Java ...

    - by kedarmhaswade
    I was not able to find any advise on catch blocks in Java that involve some cleanup operations which themselves could throw exceptions. The classic example is that of stream.close() which we usually call in the finally clause and if that throws an exception, we either ignore it by calling it in a try-catch block or declare it to be rethrown. But in general, how do I handle cases like: public void doIt() throws ApiException { //ApiException is my "higher level" exception try { doLower(); } catch(Exception le) { doCleanup(); //this throws exception too which I can't communicate to caller throw new ApiException(le); } } I could do: catch(Exception le) { try { doCleanup(); } catch(Exception e) { //ignore? //log? } throw new ApiException(le); //I must throw le } But that means I will have to do some log analysis to understand why cleanup failed. If I did: catch(Exception le) { try { doCleanup(); } catch(Exception e) { throw new ApiException(e); } It results in losing the le that got me here in the catch block in the fist place. What are some of the idioms people use here? Declare the lower level exceptions in throws clause? Ignore the exceptions during cleanup operation?

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  • Collecting high-volume video viewing data

    - by DanK
    I want to add tracking to our Flash-based media player so that we can provide analytics that show what sections of videos are being watched (at the moment, we just register a view when a video starts playing) For example, if a viewer watches the first 30 seconds of a video and then clicks away to something else, we want the data to reflect that. Likewise, if someone watches the first 10 seconds, then scrubs the timeline to the last minute of the video and watches that, we want to register viewing on the parts watched and not the middle section. My first thought was to collect up the viewing data in the player and send it all to the server at the end of a viewing session. Unfortunately, Flash does not seem to have an event that you can hook into when a viewer clicks away from the page the movie is on (probably a good thing - it would be open to abuse) So, it looks like we're going to have to make regular requests to the server as the video is playing. This is obviously going to lead to a high volume of requests when there are large numbers of simultaneous viewers. The simple approach of dumping all these 'heartbeat' events from clients to a database feels like it will quickly become unmanageable so I'm wondering whether I should be taking an approach where viewing sessions are cached in memory and flushed to database when they become inactive (based on a timeout). That way, the data could be stored as time spans rather than individual heartbeats. So, to the question - what is the best way to approach dealing with this kind of high-volume viewing data? Are there any good existing architectures/patterns? Thanks, Dan.

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  • Encryption puzzle / How to create a ProxyStub for a Remote Assistance ticket

    - by Jon Clegg
    I am trying to create a ticket for Remote Assistance. Part of that requires creating a PassStub parameter. As of the documenation: http://msdn.microsoft.com/en-us/library/cc240115(PROT.10).aspx PassStub: The encrypted novice computer's password string. When the Remote Assistance Connection String is sent as a file over e-mail, to provide additional security, a password is used.<16 In part 16 they detail how to create as PassStub. In Windows XP and Windows Server 2003, when a password is used, it is encrypted using PROV_RSA_FULL predefined Cryptographic provider with MD5 hashing and CALG_RC4, the RC4 stream encryption algorithm. As PassStub looks like this in the file: PassStub="LK#6Lh*gCmNDpj" If you want to generate one yourself run msra.exe in Vista or run the Remote Assistance tool in WinXP. The documentation says this stub is the result of the function CryptEncrypt with the key derived from the password and encrypted with the session id (Those are also in the ticket file). The problem is that CryptEncrypt produces a binary output way larger then the 15 byte PassStub. Also the PassStub isn't encoding in any way I've seen before. Some interesting things about the PassStub encoding. After doing statistical analysis the 3rd char is always a one of: !#$&()+-=@^. Only symbols seen everywhere are: *_ . Otherwise the valid characters are 0-9 a-z A-Z. There are a total of 75 valid characters and they are always 15 bytes. Running msra.exe with the same password always generates a different PassStub, indicating that it is not a direct hash but includes the rasessionid as they say. Some other ideas I've had is that it is not the direct result of CryptEncrypt, but a result of the rasessionid in the MD5 hash. In MS-RA (http://msdn.microsoft.com/en-us/library/cc240013(PROT.10).aspx). The "PassStub Novice" is simply hex encoded, and looks to be the right length. The problem is I have no idea how to go from any hash to way the ProxyStub looks like.

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  • Do you use an architectural framework for Flex/AIR development?

    - by Christophe Herreman
    Given that Flex is still a relatively young technology, there are already a bunch of architectural frameworks available for Flex/AIR (and Flash) development, the main ones being Cairngorm and PureMVC. The amount of architectural frameworks is remarkable compared to other technologies. I was wondering how many of you use an architectural framework for Flex development. If so, why, or why not if you don't use any? To share my own experience and point of view: I have used Cairngorm (and ARP for Flash development) on a variety of projects and found that at times, we needed to write extra code just to fit into the framework, which obviously didn't feel right. Although I haven't used PureMVC on many occasions, I have the same gut feeling after looking at the examples applications. Architectural frameworks equal religion in some way. Most followers are convinced that their framework is THE framework and are not open or very skeptical when it comes to using other frameworks. (I also find myself hesitant and skeptical to check out new frameworks, but that is mainly because I would rather wait until the hype is over.) In conclusion, I'm thinking that it is better to have a sound knowledge of patterns and practices that you can apply in your application instead of choosing a framework and sticking to it. There is simply no right or wrong and I don't believe that there will ever be a framework that is considered the holy grail.

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  • ECM (Niche Vs Mass Market)

    - by Luj Reyes
    Hi Everyone, I recently started a little company with a couple of guys. Ours is the typical startup, a lot of ideas, dreams, talent and work hours :P. Our initial business plan was to develop a DM (Document Manager) with several features found on DropBox and other tools but with a big differentiator. Then we got in the team this Business Guy (I must say that several of us could be called 'Business Guys' but we are mainly hackers, he is just Another 'Networking Guy'), and along with him came this market analysis for a DM aimed at a very specific and narrow niche. We have many elements to believe in his market study and the idea is the classic "The market is X million, so if we grab a 10%...", and the market is really there to grab because all big providers deemed it too little and fled, let's say that the market is 5 million USD and demand very specific features. If we decide to go for this niche product we face a sales cycle of about 7 months, and the main goal of these revenue is to develop more ambitious projects. (Institutional VC is out of the question if you want to keep a marginal ownership of your company in my country). The only overlap between the niche and the mass market product features is the ability to store documents; everything else requires that we focus all of our efforts towards one or the other. I've studied a lot about the differences between Mass and Niche Markets, but I want to hear from people with actual experience. So everything comes down to this: If you have a really “saleable” idea what is the right thing to do: to go for the niche or go for the big prize and target primarily the mass market? Thanks for your input

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  • An unusual type signature

    - by Travis Brown
    In Monads for natural language semantics, Chung-Chieh Shan shows how monads can be used to give a nicely uniform restatement of the standard accounts of some different kinds of natural language phenomena (interrogatives, focus, intensionality, and quantification). He defines two composition operations, A_M and A'_M, that are useful for this purpose. The first is simply ap. In the powerset monad ap is non-deterministic function application, which is useful for handling the semantics of interrogatives; in the reader monad it corresponds to the usual analysis of extensional composition; etc. This makes sense. The secondary composition operation, however, has a type signature that just looks bizarre to me: (<?>) :: (Monad m) => m (m a -> b) -> m a -> m b (Shan calls it A'_M, but I'll call it <?> here.) The definition is what you'd expect from the types; it corresponds pretty closely to ap: g <?> x = g >>= \h -> return $ h x I think I can understand how this does what it's supposed to in the context of the paper (handle question-taking verbs for interrogatives, serve as intensional composition, etc.). What it does isn't terribly complicated, but it's a bit odd to see it play such a central role here, since it's not an idiom I've seen in Haskell before. Nothing useful comes up on Hoogle for either m (m a -> b) -> m a -> m b or m (a -> b) -> a -> m b. Does this look familiar to anyone from other contexts? Have you ever written this function?

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  • Concurrency and Coordination Runtime (CCR) Learning Resources

    - by Harry
    I have recently been learning the in's and out's of the Concurrency and Coordination Runtime (CCR). Finding good learning resources for this relatively new technology has been quite difficult. (A quick google search brings up "Creedence Clearwater Revival" as the top result!) Some of the resources I have found: Free e-book chapter from WROX on the Robotics Developer Studio Good Article/post on InfoQ Robotic's Member blog Very active MSDN CCR Forum - Got plenty of help from here! Great MSDN Magazine by Jeffrey Richter Official CCR User Guide - Didn't find this very helpful Great blogging series on CCR iodyner CCR Related Blog - Update: Moved to here Eight or so Videos on Channel9.msdn.com CCR Patterns page on MS Robotics Studio - I haven't read this yet 4 x CCR Questions on Stackoverflow - Most of the questions have been Mine! LOL CCR and DSS toolkit has now been released to MSDN Members Do you have any good learning resources for the CCR? I really hope that Microsoft will publish more material, so far it has been too Robotics specific. I believe that MS needs to acknowledge that most people are using the CCR in issolation from the DSS and Robotics Studio. Update The Mix 2010 conference had a presentation by Myspace about how they have used the CCR framework in their middle tier. They also open sourced the code base. MySpace DataRelay Mix Video Presentation

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  • How much of STL is too much?

    - by Darius Kucinskas
    I am using a lot of STL code with std::for_each, bind, and so on, but I noticed that sometimes STL usage is not good idea. For example if you have a std::vector and want to do one action on each item of the vector, your first idea is to use this: std::for_each(vec.begin(), vec.end(), Foo()) and it is elegant and ok, for a while. But then comes the first set of bug reports and you have to modify code. Now you should add parameter to call Foo(), so now it becomes: std::for_each(vec.begin(), vec.end(), std::bind2nd(Foo(), X)) but that is only temporary solution. Now the project is maturing and you understand business logic much better and you want to add new modifications to code. It is at this point that you realize that you should use old good: for(std::vector::iterator it = vec.begin(); it != vec.end(); ++it) Is this happening only to me? Do you recognise this kind of pattern in your code? Have you experience similar anti-patterns using STL?

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  • Java method keyword "final" and its use

    - by Lukas Eder
    When I create complex type hierarchies (several levels, several types per level), I like to use the final keyword on methods implementing some interface declaration. An example: interface Garble { int zork(); } interface Gnarf extends Garble { /** * This is the same as calling {@link #zblah(0)} */ int zblah(); int zblah(int defaultZblah); } And then abstract class AbstractGarble implements Garble { @Override public final int zork() { ... } } abstract class AbstractGnarf extends AbstractGarble implements Gnarf { // Here I absolutely want to fix the default behaviour of zblah // No Gnarf shouldn't be allowed to set 1 as the default, for instance @Override public final int zblah() { return zblah(0); } // This method is not implemented here, but in a subclass @Override public abstract int zblah(int defaultZblah); } I do this for several reasons: It helps me develop the type hierarchy. When I add a class to the hierarchy, it is very clear, what methods I have to implement, and what methods I may not override (in case I forgot the details about the hierarchy) I think overriding concrete stuff is bad according to design principles and patterns, such as the template method pattern. I don't want other developers or my users do it. So the final keyword works perfectly for me. My question is: Why is it used so rarely in the wild? Can you show me some examples / reasons where final (in a similar case to mine) would be very bad?

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  • Memory usage in Flash / Flex / AS3

    - by ggambett
    I'm having some trouble with memory management in a flash app. Memory usage grows quite a bit, and I've tracked it down to the way I load assets. I embed several raster images in a class Embedded, like this [Embed(source="/home/gabriel/text_hard.jpg")] public static var ASSET_text_hard_DOT_jpg : Class; I then instance the assets this way var pClass : Class = Embedded[sResource] as Class; return new pClass() as Bitmap; At this point, memory usage goes up, which is perfectly normal. However, nulling all the references to the object doesn't free the memory. Based on this behavior, looks like the flash player is creating an instance of the class the first time I request it, but never ever releases it - not without references, calling System.gc(), doing the double LocalConnection trick, or calling dispose() on the BitmapData objects. Of course, this is very undesirable - memory usage would grow until everything in the SWFs is instanced, regardless of whether I stopped using some asset long ago. Is my analysis correct? Can anything be done to fix this?

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  • Encryption puzzle / How to create a PassStub for a Remote Assistance ticket

    - by Jon Clegg
    I am trying to create a ticket for Remote Assistance. Part of that requires creating a PassStub parameter. As of the documentation: http://msdn.microsoft.com/en-us/library/cc240115(PROT.10).aspx PassStub: The encrypted novice computer's password string. When the Remote Assistance Connection String is sent as a file over e-mail, to provide additional security, a password is used.<16 In part 16 they detail how to create as PassStub. In Windows XP and Windows Server 2003, when a password is used, it is encrypted using PROV_RSA_FULL predefined Cryptographic provider with MD5 hashing and CALG_RC4, the RC4 stream encryption algorithm. As PassStub looks like this in the file: PassStub="LK#6Lh*gCmNDpj" If you want to generate one yourself run msra.exe in Vista or run the Remote Assistance tool in WinXP. The documentation says this stub is the result of the function CryptEncrypt with the key derived from the password and encrypted with the session id (Those are also in the ticket file). The problem is that CryptEncrypt produces a binary output way larger then the 15 byte PassStub. Also the PassStub isn't encoding in any way I've seen before. Some interesting things about the PassStub encoding. After doing statistical analysis the 3rd char is always a one of: !#$&()+-=@^. Only symbols seen everywhere are: *_ . Otherwise the valid characters are 0-9 a-z A-Z. There are a total of 75 valid characters and they are always 15 bytes. Running msra.exe with the same password always generates a different PassStub, indicating that it is not a direct hash but includes the rasessionid as they say. Some other ideas I've had is that it is not the direct result of CryptEncrypt, but a result of the rasessionid in the MD5 hash. In MS-RA (http://msdn.microsoft.com/en-us/library/cc240013(PROT.10).aspx). The "PassStub Novice" is simply hex encoded, and looks to be the right length. The problem is I have no idea how to go from any hash to way the PassStub looks like.

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  • ploting 3d graph in matlab?

    - by lytheone
    Hello, I am currently a begineer, and i am using matlab to do a data analysis. I have a a text file with data at the first row is formatted as follow: time;wave height 1;wave height 2;....... I have column until wave height 19 and rows total 4000 rows. Data in the first column is time in second. From 2nd column onwards, it is wave height elevation which is in meter. At the moment I like to ask matlab to plot a 3d graph with time on the x axis, wave elevation on the y axis, and wave elevation that correspond to wave height number from 1 to 19, i.e. data in column 2 row 10 has a let say 8m which is correspond to wave height 1 and time at the column 1 row 10. I have try the following: clear; filename='abc.daf'; path='C:\D'; a=dlmread([path '\' filename],' ', 2, 1); [nrows,ncols]=size(a); t=a(1:nrows,1);%define t from text file for i=(1:20), j=(2:21); end wi=a(:,j); for k=(2:4000), l=k; end r=a(l,:); But everytime i use try to plot them, the for loop wi works fine, but for r=a(l,:);, the plot only either give me the last time data only but i want all data in the file to be plot. Is there a way i can do that. I am sorry as it is a bit confusing but i will be very thankful if anyone can help me out. Thank you!!!!!!!!!!

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  • Reconstructing trees from a "fingerprint"

    - by awshepard
    I've done my SO and Google research, and haven't found anyone who has tackled this before, or at least, anyone who has written about it. My question is, given a "universal" tree of arbitrary height, with each node able to have an arbitrary number of branches, is there a way to uniquely (and efficiently) "fingerprint" arbitrary sub-trees starting from the "universal" tree's root, such that given the universal tree and a tree's fingerprint, I can reconstruct the original tree? For instance, I have a "universal" tree (forgive my poor illustrations), representing my universe of possibilities: Root / / / | \ \ ... \ O O O O O O O (Level 1) /|\/|\...................\ (Level 2) etc. I also have tree A, a rooted subtree of my universe Root / /|\ \ O O O O O / Etc. Is there a way to "fingerprint" the tree, so that given that fingerprint, and the universal tree, I could reconstruct A? I'm thinking something along the lines of a hash, a compression, or perhaps a functional/declarative construction? Big-O analysis (in time or space) is a plus. As a for-instance, a nested expression like: {{(Root)},{(1),(2),(3)},{(2,3),(1),(4,5)}...} representing the actual nodes present at each level in the tree is probably valid, but can it be done more efficiently?

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