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• How many instructions to access pointer in C?

  - by Derek

  Hi All, I am trying to figure out how many clock cycles or total instructions it takes to access a pointer in C. I dont think I know how to figure out for example, p-x = d-a + f-b i would assume two loads per pointer, just guessing that there would be a load for the pointer, and a load for the value. So in this operations, the pointer resolution would be a much larger factor than the actual addition, as far as trying to speed this code up, right? This may depend on the compiler and architecture implemented, but am I on the right track? I have seen some code where each value used in say, 3 additions, came from a f2->sum = p1->p2->p3->x + p1->p2->p3->a + p1->p2->p3->m type of structure, and I am trying to define how bad this is

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• C++ Class Inheritance architecture - preventing casting

  - by Some One

  I have a structure of base class and a couple of inherited classed. Base class should be pure virtual class, it should prevent instantiation. Inherited classes can be instantiated. Code example below: class BaseClass { public: BaseClass(void); virtual ~BaseClass(void) = 0; }; class InheritedClass : public BaseClass { public: InheritedClass1(void); ~InheritedClass1(void); }; class DifferentInheritedClass : public BaseClass { public: DifferentInheritedClass(void); ~DifferentInheritedClass(void); }; I want to prevent the following operations to happen: InheritedClass *inherited1 = new InheritedClass(); DifferentInheritedClass *inherited2 = new DifferentInheritedClass (); BaseClass *base_1 = inherited1; BaseClass *base_2 = inherited2; *base_1 = *base_2;

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• Have the default security settings changed in Windows 7 that would affect IPrincipal.IsInRole?

  - by adrianbanks

  We use NTLM auth in our application to determine whether a user can perform certain operations. We use the IPrincipal of their current Windows login (in WinForms applications), calling IsInRole to check for specific group memberships. To check that a user is a local administrator on the machine, we use: AppDomain.CurrentDomain.SetPrincipalPolicy(PrincipalPolicy.WindowsPrincipal); ... bool allowed = Thread.CurrentPrincipal.IsInRole(@"Builtin\Administrators") This works if the current user is the Administrator user, or is another user that is a member of the Builtin\Administrators group. In our testing on Windows 7, we have found that this no longer works as expected. The Administrator user still works fine, but any other user that is a member of the Builtin\Administrators group returns false for the IsInRole call. What could be causing this difference? I have a gut feeling that a default setting has changed somewhere (possible in gpedit), but cannot find anything that looks like the culprit.

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• What is the most efficient way to store a mapping "key -> event stream"?

  - by jkff

  Suppose there are ~10,000's of keys, where each key corresponds to a stream of events. I'd like to support the following operations: push(key, timestamp, event) - pushes event to the event queue for key, marked with the given timestamp. It is guaranteed that event timestamps for a particular key are pushed in sorted or almost sorted order. tail(key, timestamp) - get all events for key since the given timestamp. Usually the timestamp requests for a given key are almost monotonically increasing, almost synchronously with pushes for the same key. This stuff has to be persistent (although it is not absolutely necessary to persist pushes immediately and to keep tails with pushes strictly in sync), so I'm going to use some kind of database. What is the optimal kind of database structure for this task? Would it be better to use a relational database, a key-value storage, or something else?

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• Custom User Management for Google App Engine Java

  - by Gopi

  I am using GAE Java for a multi-user application. There are multiple users with different roles. Each user can login, do some operations and logout. The business restricts me from using Google User Service and I need to implement my own for authentication and session management. Can anyone please share with me how should I go about implementing my own user management? I have read its very tricky to implement own user management. Any pointers in terms of best approaches/ design / existing frameworks if any ? I could see some similar posts but they are for python.

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• Are there ways to improve NHibernate's performance regarding entity instantiation?

  - by denny_ch

  Hi folks, while profiling NHibernate with NHProf I noticed that a lot of time is spend for entity building or at least spend outside the query duration (database roundtrip). The project I'm currently working on prefetches some static data (which goes into the 2nd level cache) at application start. There are about 3000 rows in the result set (and maybe 30 columns) that is queried in 75 ms. The overall duration observed by NHProf is about 13 SECONDS! Is this typical beheviour? I know that NHibernate shouldn't be used for bulk operations, but I didn't thought that entity instantiation would be so expensive. Are there ways to improve performance in such situations or do I have to live with it? Thx, denny_ch

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• Making sure unsigned int/long always execute in checked context in C#

  - by theburningmonk

  Has anyone found it strange that the default context for uint and ulong is unchecked rather than checked considering that they are meant to represent values that can never be negative? So if some code is trying to violate that constraint it seems to me the natural and preferred behaviour would be to throw an exception rather than returning the max value instead (which can easily leave important pieces of data in an invalid state and impossible to revert..). Is there an existing attribute which can be applied to either class/assembly so that it always performs arithmetic operations in a checked context? I was thinking of writing one myself (as an aspect using PostSharp) but would be great if there's one already. Many thanks,

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• Typecasting a floating value or using the math.h floor* functions?

  - by nobody

  Hi, I am coding up an implementation of Interpolation Search in C. The question is actually rather simple, I need to use the floating operations to do linear interpolation to find the correct index which will eventually be an integer result. In particular my probe index is: t = i + floor((((k-low)/(high-low)) * (j-i))); where, i,j,k,t are unsigned ints, and high,low are doubles. Would this be equivalent to: t = i + (unsigned int)(((k-low)/(high-low)) * (j-i)); Is there any reason I would actually want to use math.h floor* functions over just a simple (int) typecast?

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• How can i add an image in html email from lotus domino agent?

  - by mike_x_

  i want to add a simple image into an email which i want to send from a lotus agent. I paste below a part of the code: StringBuilder sb = new StringBuilder(); sb.append("<div><img src=\"http://goo.gl/lziMZN\"></div>"); email.setHTMLPart(sb.toString()); email.send("[email protected]"); I also tried to use an image from my image resources in the nsf. Whatever i tried i get an empty image area (browser-no-image icon) in the email i receive. I also have checked "Allow restricted operations" in my agent. I would prefer it if there is a solution to use an image from my resources and not an external link. Any solutions?

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• Want procmail to run a custom python script, everytime a new mail shows up

  - by Maddy

  I have a pretty usual requirement with procmail but I am unable to get the results somehow. I have procmailrc file with this content: :0 * ^To.*@myhost | /usr/bin/python /work/scripts/privilege_emails_forward.py Wherein my custom python script(privilege_emails_forward.py) will be scanning through the email currently received and do some operations on the mail content. But I am unable to get the script getting executed at the first shot(let alone scanning through the mail content). Is this a correct way of invoking an external program(python) as soon as new mail arrives? And how does my python program(privilege_emails_forward.py) will receive the mail as input? I mean as sys.argv or stdin????

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• Why might different computers calculate different arithmetic results in VB.NET?

  - by Eyal

  I have some software written in VB.NET that performs a lot of calculations, mostly extracting jpegs to bitmaps and computing calculations on the pixels like convolutions and matrix multiplication. Different computers are giving me different results despite having identical inputs. What might be the reason? Edit: I can't provide the algorithm because it's proprietary but I can provide all the relevant operations: ULong \ ULong (Turuncating division) Bitmap.Load("filename.bmp') (Load a bitmap into memory) Bitmap.GetPixel(Integer, Integer) (Get a pixel's brightness) Double + Double Double * Double Math.Sqrt(Double) Math.PI Math.Cos(Double) ULong - ULong ULong * ULong ULong << ULong List.OrderBy(Of Double)(Func) Hmm... Is it possible that OrderBy is using a non-stable QuickSort and that QuickSort is using a random pivot? Edit: Just tested, nope. The sort is stable.

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• DataType for storing a long serial number (10 bytes)

  - by CrimsonX

  We have a device which has a 10 byte serial number which must be read into our application and stored into a .net datatype. In the device it is stored as an unsigned 10-byte (80-bit) number. I don't expect we will be performing any mathematical operations on this number, but only displaying it to the user. The .NET framework doesn't have a built in UNIT128 to store this datatype. My suggestion for storing this datatype is to create a 10 element byte array and read in the data into this array. Are there any better solutions to this problem? Note: I have seen in this question that a GUID is a 128 byte signed integer, but it seems like a bad idea to use a GUID in this fashion. Any other suggestions?

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• Prolog - Finding the current directory, relative directory for 'tell' predicate

  - by Bharat

  I'm having trouble trying to figure out how to get prolog to spit out a text file where I want it to. I'm currently doing a bunch of operations and then using tell('output.txt') to record the output. Now the problem is that when I do this, it creates this file in the SWI \bin\ folder. I was wondering if there's a way to make it create this file in the directory containing the actual .pl file. So even if the file was moved (and it will be), the text file gets created right where the source file is. Long story short, is there a way to get the location of the source file once the source file has been consulted? Many Thanks!

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• Tweak Data in Doctrine Migration (say, by running some arbitrary queries)

  - by timdev

  I've got a migration that creates a couple of columns that act as foreign keys. In particular, I'm adding a creator_id and owner_id column to a model. These foreign keys indicate who created, and who currently owns, a particular kind of domain object. Users are managed by sfDoctrineGuardPlugin. What I'd like to do, for the purpose of the migration, is look up the (active) user with the lowest id, and default creator_id/owner_id to that. I don't see any particularly obvious/proper way to run arbitrary operations on the database during a migration. Does anyone know how?

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• Strategies for generating Zend Cache Keys

  - by emeraldjava

  ATM i'm manually generating a cache key based on the method name and parameters, then follow to the normal cache pattern. This is all done in the Controller and i'm calling a model class that 'extends Zend_Db_Table_Abstract'. public function indexAction() { $cache = Zend_Registry::get('cache'); $individualleaguekey = sprintf("getIndividualLeague_%d_%s",$leagueid,$division->code); if(!$leaguetable = $cache->load($individualleaguekey)) { $table = new Model_DbTable_Raceresult(); $leaguetable = $table->getIndividualLeague($leagueid,$division,$races); $cache->save($leaguetable, $individualleaguekey); } $this->view->leaguetable = $leaguetable; .... I want to avoid the duplication of parameters to the cache creation method and also to the model method, so i'm thinking of moving the caching logic away from my controller class and into model class packaged in './model/DbTable', but this seems incorrect since the DB model should only handle SQL operations. Any suggestions on how i can implement a clean patterned solution?

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• PHP: OOP and methods

  - by Pirkka

  Hello I`ve been wondering how to implement methods in a class. Could someone explain me what means if one does OOP in procedural style? Here is an example: class Fld extends Model { private $file; private $properties = array(); public function init($file) { $this->file = $file; $this->parseFile(); } private function parseFile() { // parses the file foreach($this->file as $line)...... .................. $this->properties = $result; } } I mean is it a good thing to have methods like these that do operations for the class properties like that. Or should I pass the class property as method parameter... I mean this would cause error if the file property wouldnt be declared.

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• App engine downtime

  - by DutrowLLC

  I've noticed that google app engine seems to have a fair amount of downtime where they place the datastore into read-only mode. Frequently this downtime is in the middle of the day. Is this something that is happening only during early development, or is this something that I can expect to be always be occurring? I've developing an application that helps small businesses handle their operations. One thing that it does is take appointments, another is route phone calls. I'd like some suggestions on how to handle times when the datastore is in read-only such as: What if our client is on the phone with the customer and is taking down an appointment and the datastore is in read-only? It would not be acceptable to ask the client to come back later to save, especially if its in the middle of the day. What if there is an incoming call and the application can not store the record or properly route the call due to database writes being unavailable? How are these types of issues normally handled?

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• SmartGWT Server File Browser

  - by jluzwick

  Hi All: I have been looking for a SmartGWT example that would show me how to build a File Browser widget that takes the files from the local server's root directory. The user would be shown the files through the browser which they could then select to perform some processing operations. So far I have thought of using SmartGWT's Tree-Data Binding-Load from Local Data Widget and then grabbing a list of the directories using: new File("\").listFiles(); My Question is: Is there a better way to do this? Has someone already thought of this and has an example of their code that I can see? PS: I'm fairly new to GWT and Web Services but fairly competent with Java. If you believe there is a better way to do this (while still doing this through the web and not using Applets, please tell me). Thanks

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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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• How to replace values in multi-valued ESE column?

  - by Soonts

  I have a multi-valued short ASCII text column in one of the tables in my ESE database, that holds the person's phone numbers. I have the new set of values, and I'd like to wipe the old values completely, and only use the new values. The JET_bitSetRevertToDefaultValue bit doesn't seem to work. While the MSDN documentation says "It causes the column to return the default column value on subsequent retrieve column operations. All existing column values are removed.", I found that it does nothing (no return value is returned). Or, is there an easy way to find out how many values does the column contain (this could be zero, e.g. when I'm doing an insertion, not update)? If it was, I could just run a loop from 'nValues' to 1, erasing the value by setting it to the null while providing the itagSequence value, to achieve what I want. I'm programming C#, and using the latest version of ManagedEsent library. Thanks in advance!

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• jQuery : how to manipulate indexes?

  - by Gabriel Theron

  Should not be such a hard question... I'm just having a hard time figuring out how to make operations on some jquery elements, particularly their indexes. Teh codez: $( "#docSlider" ).css("background-image", "url(../../bundles/mypath/images/maquette/img" + $( "#selectable li" ).index( this ) + (".jpg)")); I want to make the name of the picture I load depend on the index of a jQuery selectable. So I grab the index and try to add 1... but it can't work because "+" is also a concatenator. I've tried to parseInt as well, but it was always worth 0. How do I simply transform the index to an integer and then concatenate it with the rest of the string? Thank you in advance! Edit : I'm using a function that already exists, so I can hardly change the parameters (well, I guess I can't...)

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• Why does order matter for ImageMagick's -colorspace operation?

  - by Mark Trapp

  Starting with ImageMagick 6, the command style changed to solve a bunch of problems outlined in the Basic Usage document. That document does imply that for simple operations, one should only need to move the options from before the source file to between the source and output files to convert from the "old" style to the "new" style. However, this doesn't seem to work for the -colorspace operation. When I use the following command, I get an output file with the correct colors: convert -colorspace rgb input.pdf output.png But when I try to use the new command style, the -colorspace operation is never applied: convert input.pdf -colorspace rgb output.png Samples: Why does this occur?

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• Int PK inner join Vs Guid PK inner Join on SQL Server. Execution plan.

  - by bigb

  I just did some testing for Int PK join Vs Guid PK. Tables structure and number of records looking like that: Performance of CRUD operations using EF4 are pretty similar in both cases. As we know Int PK has better performance rather than strings. So SQL server execution plan with INNER JOINS are pretty different Here is an execution plan. As i understand according with execution plan from attached image Int join has better performance because it is taking less resources for Clustered index scan and it is go in two ways, am i right? May be some one may explain this execution plan in more details?

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• How should I port this Prototype to JQuery?

  - by blu

  There is currently this Prototype code that does a PUT: new Ajax.Request(someUrl, { method: 'put', parameters: { 'foo': bar }, onSuccess: function(response) { } .bind(this) }); I found this post but the solution uses an extra parameter supported by RoR, however I am targeting an ASP.NET backend. I searched a bit and found that not all browsers support PUT operations so apparently this could fail in certain browsers? This is already in prod, so a direct port would be fine for now I suppose. As an aside, what is the deal with the bind(this) in the onSuccess function?

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• Comparison of collection datatypes in C#

  - by Joel in Gö

  Does anyone know of a good overview of the different C# collection types? I am looking for something showing which basic operations such as Add, Remove, RemoveLast etc. are supported, and giving the relative performance. It would be particularly interesting for the various generic classes - and even better if it showed eg. if there is a difference in performance between a List<T> where T is a class and one where T is a struct. A start would be a nice cheat-sheet for the abstract data structures, comparing Linked Lists, Hash Tables etc. etc. Thanks!

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