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• ORM solutions (JPA; Hibernate) vs. JDBC

  - by Grasper

  I need to be able to insert/update objects at a consistent rate of at least 8000 objects every 5 seconds in an in-memory HSQL database. I have done some comparison performance testing between Spring/Hibernate/JPA and pure JDBC. I have found a significant difference in performance using HSQL.. With Spring/Hib/JPA, I can insert 3000-4000 of my 1.5 KB objects (with a One-Many and a Many-Many relationship) in 5 seconds, while with direct JDBC calls I can insert 10,000-12,000 of those same objects. I cannot figure out why there is such a huge discrepancy. I have tweaked the Spring/Hib/JPA settings a lot trying to get close in performance without luck. I want to use Spring/Hib/JPA for future purposes, expandability, and because the foreign key relationships (one-many and many-many) are difficult to maintain by hand; but the performance requirements seem to point towards using pure JDBC. Any ideas of why there would be such a huge discrepancy?

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• TStringList, Dynamic Array or Linked List in Delphi?

  - by lkessler

  I have a choice. I have an array of ordered strings that I need to store and access. It looks like I can choose between using: A TStringList A Dynamic Array of strings, and A Linked List of strings In what circumstances is each of these better than the others? Which is best for small lists (under 10 items)? Which is best for large lists (over 1000 items)? Which is best for huge lists (over 1,000,000 items)? Which is best tor minimize memory use? Which is best to minimize loading and/or access time? For reference, I am using Delphi 2009.

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• About local Final varibles in java

  - by Sathish

  In java Program, parameters which is defined as String in method declaration.But in method definition it is accessed as final String variable. Whether it'll lead to some issues (like security, memory problem)? For Example: Method Declaration join(String a,String b); Method definition public void join(final String a,final String b) { Authenticator au = new Authenticator(){ public PasswordAuthentication getPasswordAuthentication(){ return new PasswordAuthentication(a,b)} }; } Please help for me and clarify my doubts. Thanks in advance P.S. I;m accessing a and b as final variable because i've to use it in the inner class.

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• Lamp with mod_fastcgi

  - by Jonathan

  Hi! I am building a cgi application, and now I would like it to be like an application that stands and parses each connection, with this, I can have all session variables saved in memory instead of saving them to file(or anyother place) and loading them again on a new connection I am using lamp within a linux vmware but I can't seem to find how to install the module for it to work and what to change in the httpd.conf. I tried to compile the module, but I couldn't because my apache isn't a regular instalation, its a lamp already built one, and it seems that the mod needs the apache directory to be compiled. I saw some coding examples out there, so I guess is not that hard once its runing ok with Apache Can you help me with this please? Thanks, Joe

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• Performance monitor shows 4294967293 sessions active

  - by TGnat

  I have an ASP.Net 3.5 website running in IIS 6 on Windows Server 2003 R2. It is a relatively small internal application that probably serves less than ten users at any given time. The server has 4 Gig of memory and shows that 3+ Gig is available while the site is active. Just minutes after restarting the web application Performance monitor shows that there is a whopping 4,294,967,293 sessions active! I am fairly certain that this number is incorrect; at the time this reading there were only 100 requests to the website. Has anyone else experienced this kind odd behavior from perf mon? Any ideas on how to get an accurate reading? UPDATE: After running for about an hour the number of active sessions has dropped by 4. So it does seem to be responding to sessions timing out.

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• Why do AlarmManager broadcasts get cancelled when app gets killed?

  - by skooter

  Ok so I have two BroadcastReceiver registered. When the app is closed they both fire at the appropriate times and do the appropriate things. If the app is closed then killed (say with an AppKiller), the receivers never receive their broadcasts, and nothing happens. Presumably the same thing happens if the parent app is killed due to low memory, so how do I ensure those broadcasts are fired/received. The API states that even if the app is killed it should fire, does anyone else have experience with this situation? If it helps my manifest is: <!-- receivers for AlarmManager --> <receiver android:exported="true" android:label="Shift roster updating calendar." android:name="com.skooter.shiftroster.backend.service.UpdateCalendar" > </receiver> <receiver android:exported="true" android:label="Shift roster checking alarm." android:name="com.skooter.shiftroster.backend.service.SetWakeup" > </receiver> and nothing esoteric is going on in the AlarmManager/BroadcastReceivers

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• Refactor/rewrite code or continue?

  - by Dan

  I just completed a complex piece of code. It works to spec, it meets performance requirements etc etc but I feel a bit anxious about it and am considering rewriting and/or refactoring it. Should I do this (spending time that could otherwise be spent on features that users will actually notice)? The reasons I feel anxious about the code are: The class hierarchy is complex and not obvious Some classes don't have a well defined purpose (they do a number of unrelated things) Some classes use others internals (they're declared as friend classes) to bypass the layers of abstraction for performance, but I feel they break encapsulation by doing this Some classes leak implementation details (eg, I changed a map to a hash map earlier and found myself having to modify code in other source files to make the change work) My memory management/pooling system is kinda clunky and less-than transparent They look like excellent reasons to refactor and clean code, aiding future maintenance and extension, but could be quite time consuming. Also, I'll never be perfectly happy with any code I write anyway... So, what does stackoverflow think? Clean code or work on features?

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• Whats the problem with int *p; *p=23;

  - by piemesons

  Yesterday in my interview I was asked this question. (At that time I was highly pressurized by so many abrupt questions). int *p; *p=23; printf('%d',*p); Is there any problem with this code? I explained him that you are trying to assign value to a pointer to whom memory is not allocated. But the way he reacted, it was like I am wrong. Although I got the job but after that he said Mohit think about this question again. I don't know what he was trying to say. Please let me know is there any problem in my answer?

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• What is the difference between a 32-bit and 64-bit processor?

  - by JJG

  I have been trying to read up on 32-bit and 64-bit processors (http://en.wikipedia.org/wiki/32-bit_processing). My understanding is that a 32-bit processor (like x86) has registers 32-bits wide. I'm not sure what that means. So it has special "memory spaces" that can store integer values up to 2^32? I don't want to sound stupid, but I have no idea about processors. I'm assuming 64-bits is, in general, better than 32-bits. Although my computer now (one year old, Win 7, Intel Atom) has a 32-bit processor.

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• SQLAlchemy automatically converts str to unicode on commit

  - by Victor Stanciu

  Hello, When inserting an object into a database with SQLAlchemy, all it's properties that correspond to String() columns are automatically transformed from <type 'str'> to <type 'unicode'>. Is there a way to prevent this behavior? Here is the code: from sqlalchemy import create_engine, Table, Column, Integer, String, MetaData from sqlalchemy.orm import mapper, sessionmaker engine = create_engine('sqlite:///:memory:', echo=False) metadata = MetaData() table = Table('projects', metadata, Column('id', Integer, primary_key=True), Column('name', String(50)) ) class Project(object): def __init__(self, name): self.name = name mapper(Project, table) metadata.create_all(engine) session = sessionmaker(bind=engine)() project = Project("Lorem ipsum") print(type(project.name)) session.add(project) session.commit() print(type(project.name)) And here is the output: <type 'str'> <type 'unicode'> I know I should probably just work with unicode, but this would involve digging through some third-party code and I don't have the Python skills for that yet :)

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• Simple File-based Record Storage with Fast Text Searching for Compact Framework and Silverlight

  - by Eric Farr

  I have a single table with lots of records ( 100k) that I need to be able to index and search on several text fields. The easiest searches will have the first part of the string specified (eg, LIKE 'ABC%' in SQL). The tougher searches will need to search for any substring within the text fields (eg, LIKE '%ABC%' in SQL). I need to run on the Compact Framework. SQL Compact is a memory hog and overkill for my one table. Besides, I'd like to be able to run on Silverlight 4 eventually. The file and indexes can be generated on the full .NET Framework and I only need read capability on the Compact Framework. My records are not especially large and can be expressed in fix length format. I'm looking for some existing code or libraries to avoid having to write a file-based BTree implementation from scratch.

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• A hooked DirectX 9 program crashes on window resize, texture related.

  - by Ben

  I'm using EasyHook and SlimDX to overlay some graphics using SlimDX's Sprite and Texture classes. When I resize windows some programs fine, but others will crash - Winamp's MilkDrop 2 gives me an ambiguous memory error for example. I expect this is due to the after market Texture I created. The question is what VTable function should I hook and/or how/when do I dispose and recreate the Texture? Reset perhaps? If it isn't obvious I don't know much about DirectX.

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• How would I UPDATE these table entries with SQL?

  - by CT

  I am working on an Asset Database problem. I enter assets into a database. Every object is an asset and has variables within the asset table. An object is also a type of asset. In this example the type is server. Here is the Query to retrieve all necessary data: SELECT asset.id ,asset.company ,asset.location ,asset.purchaseDate ,asset.purchaseOrder ,asset.value ,asset.type ,asset.notes ,server.manufacturer ,server.model ,server.serialNumber ,server.esc ,server.warranty ,server.user ,server.prevUser ,server.cpu ,server.memory ,server.hardDrive FROM asset LEFT JOIN server ON server.id = asset.id WHERE asset.id = '$id' How would I write a query to update an asset?

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• C++ smart pointer for a non-object type?

  - by Brian

  Hi, I'm trying to use smart pointers such as auto_ptr, shared_ptr. However, I don't know how to use it in this situation. CvMemStorage *storage = cvCreateMemStorage(); ... use the pointer ... cvReleaseMemStorage(&storage); I'm not sure, but I think that the storage variable is just a malloc'ed memory, not a C++ class object. Is there a way to use the smart pointers for the storage variable? Thank you.

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• java - volatile keyword

  - by Tiyoal

  Say I have two threads and an object. One thread assigns the object: public void assign(MyObject o) { myObject = o; } Another thread uses the object: public void use() { myObject.use(); } Does the variable myObject have to be declared as volatile? I am trying to understand when to use volatile and when not, and this is puzzling me. Is it possible that the second thread keeps a reference to an old object in its local memory cache? If not, why not? Thanks a lot.

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• Java - Creating a Compiler Help

  - by Brian

  So for my programming class we have had a project to create a virtual machine including a memory unit, cpu, Input, Output, Instruction Register, Program Counter, MAR, MDR and so on. Now we need to create a compiler using Java Code that will take a .exe file written in some txt editor and convert it to java byte code and run the code. The code we will be writing in the .exe file is machine code along the lines of: IN X IN Y ADD X STO Y OUT Y STOP DC X 0 DC Y 0 I am just a beginner and only have 2 days to write this and am very lost and have no idea where to start....Any Help will be much appreciated. Thanks

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• Why should i use EJB?

  - by Nitesh Panchal

  Hello, As we all know that EJB's in 3.1 or 3.0 are simple POJOs. You just need to give annotations here and there and it gets converted to EJB from simple class. So, now my question is why should i use EJBs at all? Can i not do without them? In .Net i created class library and got things done. I never felt the need for anything like EJB. Simple classes were enough. Then, why in Java people stress on EJB? What is difference between a simple POJO and EJB in terms of execution and memory? Further which function should i write in EJB and which should i write in simple class? Should i dump every function in EJB only? or there is some kind of strategy? Does EJB provide anything special?

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• Fast, lightweight XML parser

  - by joe90

  I have a specific format XML document that I will get pushed. This document will always be the same type so it's very strict. I need to parse this so that I can convert it into JSON (well, a slightly bastardized version so someone else can use it with DOJO). My question is, shall I use a very fast lightweight (no need for SAX, etc.) XML parser (any ideas?) or write my own, basically converting into a StringBuffer and spinning through the array? Basically, under the covers I assume all HTML parsers will spin thru the string (or memory buffer) and parse, producing output on the way through. Thanks //edit Thanks for the responses so far :) The xml will be between 3/4 lines to about 50 max (at the extreme)..

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• Swapping UIImages causing 'unrecognized selector sent to instance' ?

  - by user158103

  Error: [__NSCFDate drawAtPoint:]: unrecognized selector sent to instance 0xd251e0 Termininating app due to uncaught exception 'NSInvalidArgumentException' Scenario: for the most part this works. But I notice this error, even on the simulator, when I swapping UIImages, slowly, but consistently. For example, I have a retained reference to a UIImage that im drawing. By the click of a picker control I am changing the face image (this occurs in another view-controller). I can consistently recreate this error by continuously changing the faces. It usually crashes at about the 4th swap or more. My theory: It's not loading the image, therefore the image reference is nil. I know ive read a bit about UIImage being cached, so I wouldnt think im running out of memory. Any ideas? Thanks!

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• C# "Could not find a part of the path" - Creating Local File

  - by Pyronaut

  I am trying to write to a folder that is located on my C:\ drive. I keep getting the error of : Could not find a part of the path .. etc My filepath looks basically like this : C:\WebRoot\ManagedFiles\folder\thumbs\5c27a312-343e-4bdf-b294-0d599330c42d\Image\lighthouse.jpg And I am writing to it like so : using (MemoryStream memoryStream = new MemoryStream()) { thumbImage.Save(memoryStream, ImageFormat.Jpeg); using (FileStream diskCacheStream = new FileStream(cachePath, FileMode.CreateNew)) { memoryStream.WriteTo(diskCacheStream); } memoryStream.WriteTo(context.Response.OutputStream); } Don't worry too much about the memory stream. It is just outputting it (After I save it). Since I am creating a file, I am a bit perplexed as to why it cannot find the file (Shouldn't it just write to where I tell it to, regardless?). The strange thing is, It has no issue when I'm testing it above using File.Exists. Obviously that is returning false, But it means that atleast my Filepath is semi legit. Any help is much appreciated.

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• Error after updating to the latest version Azure SDK

  - by Mikael Johansson

  After I updated to the newest version the Azure SDK I have started to get this error several times each day when I press build in Visual Studio. The only way for me to fix it at the moment is to restart my visual studio. The error I get is: Windows Azure Tools: Invalid access to memory location Is there someone else that have got this error? And also what did you do to fix it? Thanks in advance! Update 2012-08-28: The same error still exist in VS2012 and Azure 1.7 SDK. However the frequency have gone down with VS2012.

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• iPad crashes that aren't happening on iPhone or iPod Touch

  - by alyoshak

  Has anyone had difficulty getting what has otherwise been a solid iPhone app working on the iPad? I was under the impression that iPhone apps would run without problems on the iPad. We are are experiencing crashes (not intermittent - same place, at same time) that we've never gotten on the iPhone or iPod Touch. I have become suspicious that the crashes are memory-management related, but even if so, why only on the iPad? 2010-05-17 10:19:06.474 ASSIST[82:207] *** Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[<UISectionRowData 0x6041480> valueForUndefinedKey:]: this class is not key value coding-compliant for the key deliveryDate.' 2010-05-17 10:19:06.481 ASSIST[82:207] Stack: ( 852041337, 861292157, 852040861, 850755255, 850750995, 850758945, 81279, 123007, 126693, 149141, 851599725, 827486573, 827486477, 827486431, 827485745, 827487359, 827454123, 851903137, 851590065, 851588321, 819339483, 819339655, 827151561, 827144691, 9461, 9324 ) terminate called after throwing an instance of 'NSException' Program received signal: “SIGABRT”.

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• Is there a distributed VCS that can manage large files?

  - by joelhardi

  Is there a distributed version control system (git, bazaar, mercurial, darcs etc.) that can handle files larger than available RAM? I need to be able to commit large binary files (i.e. datasets, source video/images, archives), but I don't need to be able to diff them, just be able to commit and then update when the file changes. I last looked at this about a year ago, and none of the obvious candidates allowed this, since they're all designed to diff in memory for speed. That left me with a VCS for managing code and something else ("asset management" software or just rsync and scripts) for large files, which is pretty ugly when the directory structures of the two overlap.

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• How to create a custom ADO Multi Demensional Catalog with no database

  - by Alan Clark

  Does anyone know of an example of how to dynamically define and build ADO MD (ActiveX Data Objects Multidimensional) catalogs and cube definitions with a set of data other than a database? Background: we have a huge amount of data in our application that we export to a database and then query using the usual SQL joins, groups, sums etc to produce reports. The data in the application is originally in objects and arrays. The problem is the amount of data is so large the export can take 2 hours. So I am trying to figure out a good way of querying the objects in memory, either by a custom OLAP algorithm or library, or ADO MD. But I haven't been able to find an example of using ADO MD without a database behind it. We are using Delphi 2010 so would use ADO ActiveX but I imagine the ADO.NET MD is similar. I realize that if the application data was already stored in a database the problem would solve itself. Also if Delphi had LINQ capability I could query the objects and arrays that way.

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• Expression Tree : C#

  - by nettguy

  My understanding of expression tree is : Expression trees are in-memory representation of expression like arithmetic or boolean expression.The expressions are stored into the parsed tree.so we can easily transalate into any other language. Linq to SQL uses expression tree.Normally when our LINQ to SQL query compiler translates it to parsed expression trees.These are passed to Sql Server as T-SQL Statements.The Sql server executes the T-SQL query and sends down the result back.That is why when you execute LINQ to SQL you gets IQueryable<T> not IEnumetrable<T>.Because IQuerybale contains public IQueryable:IEnumerable { Type Element {get;} Expression Expression {get;} IQueryaleProvider Provider {get;} } Questions : Microsoft uses Expression trees to play with LINQ-to-Sql.What are the different ways can i use expression trees to boost my code. Apart from LINQ to SQL,Linq to amazon ,who used expression trees in their applications? Linq to Object return IEnumerable,Linq to SQL return IQueryable ,What does LINQ to XML return?

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