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  • Why is thread local storage so slow?

    - by dsimcha
    I'm working on a custom mark-release style memory allocator for the D programming language that works by allocating from thread-local regions. It seems that the thread local storage bottleneck is causing a huge (~50%) slowdown in allocating memory from these regions compared to an otherwise identical single threaded version of the code, even after designing my code to have only one TLS lookup per allocation/deallocation. This is based on allocating/freeing memory a large number of times in a loop, and I'm trying to figure out if it's an artifact of my benchmarking method. My understanding is that thread local storage should basically just involve accessing something through an extra layer of indirection, similar to accessing a variable via a pointer. Is this incorrect? How much overhead does thread-local storage typically have? Note: Although I mention D, I'm also interested in general answers that aren't specific to D, since D's implementation of thread-local storage will likely improve if it is slower than the best implementations.

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  • ASP.NET MVC Data passing

    - by user295541
    Hi, I need a good example or guideline which could give me a pattern for data passing between view and partial view. For example I have a view which contains several partial views. I refresh these partial view by ajax. So I need to pass data among view and its partial views. The best way would be if I could pass data without using Temp data dictionary. Anybody know a good article about this? l.

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  • SQL Query slow in .NET application but instantaneous in SQL Server Management Studio

    - by user203882
    Here is the SQL SELECT tal.TrustAccountValue FROM TrustAccountLog AS tal INNER JOIN TrustAccount ta ON ta.TrustAccountID = tal.TrustAccountID INNER JOIN Users usr ON usr.UserID = ta.UserID WHERE usr.UserID = 70402 AND ta.TrustAccountID = 117249 AND tal.trustaccountlogid = ( SELECT MAX (tal.trustaccountlogid) FROM TrustAccountLog AS tal INNER JOIN TrustAccount ta ON ta.TrustAccountID = tal.TrustAccountID INNER JOIN Users usr ON usr.UserID = ta.UserID WHERE usr.UserID = 70402 AND ta.TrustAccountID = 117249 AND tal.TrustAccountLogDate < '3/1/2010 12:00:00 AM' ) Basicaly there is a Users table a TrustAccount table and a TrustAccountLog table. Users: Contains users and their details TrustAccount: A User can have multiple TrustAccounts. TrustAccountLog: Contains an audit of all TrustAccount "movements". A TrustAccount is associated with multiple TrustAccountLog entries. Now this query executes in milliseconds inside SQL Server Management Studio, but for some strange reason it takes forever in my C# app and even timesout (120s) sometimes. Here is the code in a nutshell. It gets called multiple times in a loop and the statement gets prepared. cmd.CommandTimeout = Configuration.DBTimeout; cmd.CommandText = "SELECT tal.TrustAccountValue FROM TrustAccountLog AS tal INNER JOIN TrustAccount ta ON ta.TrustAccountID = tal.TrustAccountID INNER JOIN Users usr ON usr.UserID = ta.UserID WHERE usr.UserID = @UserID1 AND ta.TrustAccountID = @TrustAccountID1 AND tal.trustaccountlogid = (SELECT MAX (tal.trustaccountlogid) FROM TrustAccountLog AS tal INNER JOIN TrustAccount ta ON ta.TrustAccountID = tal.TrustAccountID INNER JOIN Users usr ON usr.UserID = ta.UserID WHERE usr.UserID = @UserID2 AND ta.TrustAccountID = @TrustAccountID2 AND tal.TrustAccountLogDate < @TrustAccountLogDate2 ))"; cmd.Parameters.Add("@TrustAccountID1", SqlDbType.Int).Value = trustAccountId; cmd.Parameters.Add("@UserID1", SqlDbType.Int).Value = userId; cmd.Parameters.Add("@TrustAccountID2", SqlDbType.Int).Value = trustAccountId; cmd.Parameters.Add("@UserID2", SqlDbType.Int).Value = userId; cmd.Parameters.Add("@TrustAccountLogDate2", SqlDbType.DateTime).Value =TrustAccountLogDate; // And then... reader = cmd.ExecuteReader(); if (reader.Read()) { double value = (double)reader.GetValue(0); if (System.Double.IsNaN(value)) return 0; else return value; } else return 0;

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  • Database warehoue design: fact tables and dimension tables

    - by morpheous
    I am building a poor man's data warehouse using a RDBMS. I have identified the key 'attributes' to be recorded as: sex (true/false) demographic classification (A, B, C etc) place of birth date of birth weight (recorded daily): The fact that is being recorded My requirements are to be able to run 'OLAP' queries that allow me to: 'slice and dice' 'drill up/down' the data and generally, be able to view the data from different perspectives After reading up on this topic area, the general consensus seems to be that this is best implemented using dimension tables rather than normalized tables. Assuming that this assertion is true (i.e. the solution is best implemented using fact and dimension tables), I would like to see some help in the design of these tables. 'Natural' (or obvious) dimensions are: Date dimension Geographical location Which have hierarchical attributes. However, I am struggling with how to model the following fields: sex (true/false) demographic classification (A, B, C etc) The reason I am struggling with these fields is that: They have no obvious hierarchical attributes which will aid aggregation (AFAIA) - which suggest they should be in a fact table They are mostly static or very rarely change - which suggests they should be in a dimension table. Maybe the heuristic I am using above is too crude? I will give some examples on the type of analysis I would like to carryout on the data warehouse - hopefully that will clarify things further. I would like to aggregate and analyze the data by sex and demographic classification - e.g. answer questions like: How does male and female weights compare across different demographic classifications? Which demographic classification (male AND female), show the most increase in weight this quarter. etc. Can anyone clarify whether sex and demographic classification are part of the fact table, or whether they are (as I suspect) dimension tables.? Also assuming they are dimension tables, could someone elaborate on the table structures (i.e. the fields)? The 'obvious' schema: CREATE TABLE sex_type (is_male int); CREATE TABLE demographic_category (id int, name varchar(4)); may not be the correct one.

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  • Javascript window.onunload fires off after Page_Load

    - by gnomixa
    I have noticed that window.onunload event fires off AFTER page_load event which makes no sense. This behaviour is creating an issue for me - in my unonload I clear the session, so if the Page_Load first BEFORE onunload, there are errors on the page displayed. I would expect the javascript onunload to fire BEFORE Page_Load....is that the correct assumption? TO CLARIFY: Let's assume I am on page test.aspx, then I click on the link that goes to the same page (say I click on a menu), what I observe is that Page_Load fires first, then onunload fires off. Makes no sense at all.

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  • Data Processing in Business Intelligence Applications

    - by Manoj
    Is data processing a part of business intelligence tools? If no how else is it done or if yes can you give a few examples. My use case: I am using pentaho reporting to generate tables and graphs of my test data. Now I want to compare the data against the spec and see if it passes or fails and report the same. The spec is also in the database. How best to do it?

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  • SQL Server high CPU and I/O activity database tuning

    - by zapping
    Our application tends to be running very slow recently. On debugging and tracing found out that the process is showing high cpu cycles and SQL Server shows high I/O activity. Can you please guide as to how it can be optimised? The application is now about an year old and the database file sizes are not very big or anything. The database is set to auto shrink. Its running on win2003, SQL Server 2005 and the application is a web application coded in c# i.e vs2005

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  • How to extract data from a PDF?

    - by Fermin
    Hi, My company receives data from an external company via Excel. We export this into SQL Server to run reports on the data. They are now changing to PDF format, is there a way to reliably port the data from the PDF and insert it into our SQL Server 2008 database? Would this require writing an app or is there an automated way of doing this?

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  • Ruby data structure to render a certain JSON format

    - by dt
    [{"id":"123","name":"House"}, {"id":"1456","name":"Desperate Housewives"}, {"id":"789","name":"Dollhouse"}, {"id":"10","name":"Full House"} ] How can I render to produce this JSON format from within Ruby? I have all the data from the DB (@result) and don't know what data structure to use in Ruby that will render to this when I do this: respond_to do |format| format.json { render :json = @result} end What data structure should @result be and how can I iterate to produce it? Thank you!

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  • Is regex too slow? Real life examples where simple non-regex alternative is better

    - by polygenelubricants
    I've seen people here made comments like "regex is too slow!", or "why would you do something so simple using regex!" (and then present a 10+ lines alternative instead), etc. I haven't really used regex in industrial setting, so I'm curious if there are applications where regex is demonstratably just too slow, AND where a simple non-regex alternative exists that performs significantly (maybe even asymptotically!) better. Obviously many highly-specialized string manipulations with sophisticated string algorithms will outperform regex easily, but I'm talking about cases where a simple solution exists and significantly outperforms regex. What counts as simple is subjective, of course, but I think a reasonable standard is that if it uses only String, StringBuilder, etc, then it's probably simple.

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  • Trying to speed up a SQLITE UNION QUERY

    - by user142683
    I have the below SQLITE code SELECT x.t, CASE WHEN S.Status='A' AND M.Nomorebets=0 THEN S.PriceText ELSE '-' END AS Show_Price FROM sb_Market M LEFT OUTER JOIN (select 2010 t union select 2020 t union select 2030 t union select 2040 t union select 2050 t union select 2060 t union select 2070 t ) as x LEFT OUTER JOIN sb_Selection S ON S.MeetingId=M.MeetingId AND S.EventId=M.EventId AND S.MarketId=M.MarketId AND x.t=S.team WHERE M.meetingid=8051 AND M.eventid=3 AND M.Name='Correct Score' With the current interface restrictions, I have to use the above code to ensure that if one selection is missing, that a '-' appears. Some feed would be something like the following SelectionId Name Team Status PriceText =================================== 1 Barney 2010 A 10 2 Jim 2020 A 5 3 Matt 2030 A 6 4 John 2040 A 8 5 Paul 2050 A 15/2 6 Frank 2060 S 10/11 7 Tom 2070 A 15 Is using the above SQL code the quickest & efficient?? Please advise of anything that could help. Messages with updates would be preferable.

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  • WinForms data binding with a Save button?

    - by Mat
    How is data binding in C# WinForms supposed to work when you have a Save button? I don't want the data updated until I press Save! I have two forms (list and detail) backed by a BindingList<T> collection and my custom object from that collection, respectively. I can bind each form to the list or object appropriately. However, any changes made in the detail form are immediately reflected in the list form - I don't want to save the changes and update the details shown in the list until the Save button is pressed. Is data binding designed to support this? Is there a common pattern for doing so? Whichever way I look at it, binding doesn't seem to be able to support this scenario. I've considered the following: Pass a clone of the object to the detail form, but then I have to reconcile the changes on Save - changes may have been made to the copy in the list in the meantime. Implementing IEditableObject and calling EndEdit on save almost works as I can prevent the list being notified of the changes made until Save is pressed, but if something else causes a refresh the list is updated with the interim data. I'm currently left with dispensing with data binding in my detail view, and doing it all manually. Which is rather annoying.

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  • Benchmarking a particular method in Objective-C

    - by Jasconius
    I have a critical method in an Objective-C application that I need to optimize as much as possible. I first need to take some easy benchmarks on this one single method so I can compare my progress as I optimize. What is the easiest way to track the execution time of a given method in, say, milliseconds, and print that to console.

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  • Which is faster in Python: x**.5 or math.sqrt(x)?

    - by Casey
    I've been wondering this for some time. As the title say, which is faster, the actual function or simply raising to the half power? UPDATE This is not a matter of premature optimization. This is simply a question of how the underlying code actually works. What is the theory of how Python code works? I sent Guido van Rossum an email cause I really wanted to know the differences in these methods. My email: There are at least 3 ways to do a square root in Python: math.sqrt, the '**' operator and pow(x,.5). I'm just curious as to the differences in the implementation of each of these. When it comes to efficiency which is better? His response: pow and ** are equivalent; math.sqrt doesn't work for complex numbers, and links to the C sqrt() function. As to which one is faster, I have no idea...

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  • Is this good code? Linked List Stack Implementation

    - by Quik Tester
    I have used the following code for a stack implementation. The top keeps track of the topmost node of the stack. Now since top is a data member of the node function, each node created will have a top member, which ideally we wouldn't want. Firstly, is this good approach to coding? Secondly, will making top as static make it a better coding practice? Or should I have a global declaration of top? #include<iostream> using namespace std; class node { int data; node *top; node *link; public: node() { top=NULL; link=NULL; } void push(int x) { node *n=new node; n->data=x; n->link=top; top=n; cout<<"Pushed "<<n->data<<endl; } void pop() { node *n=new node; n=top; top=top->link; n->link=NULL; cout<<"Popped "<<n->data<<endl; delete n; } void print() { node *n=new node; n=top; while(n!=NULL) { cout<<n->data<<endl; n=n->link; } delete n; } }; int main() { node stack; stack.push(5); stack.push(7); stack.push(9); stack.pop(); stack.print(); } Any other suggestions welcome. I have also seen codes where there are two classes, where the second one has the top member. What about this? Thanks. :)

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  • Source Controlled Database Data import strategies.

    - by H. Abraham Chavez
    So I've gotten a project and got the db team sold on source control for the db (weird right?) anyway, the db already exists, it is massive, and the application is very dependent on the data. The developers need up to three different flavors of the data to work against when writing SPROCs and so on. Obviously I could script out data inserts. But my question is what tools or strategies do you use to build a db from source control and populate it with multiple large sets of data?

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  • Updating multiple related tables in SQLite with C#

    - by PerryJ
    Just some background, sorry so long winded. I'm using the System.Data.SQLite ADO.net adapter to create a local sqlite database and this will be the only process hitting the database, so I don't need to worry about concurrency. I'm building the database from various sources and don't want to build this all in memory using datasets or dataadapters or anything like that. I want to do this using SQL (DdCommands). I'm not very good with SQL and complete noob in sqlite. I'm basically using sqlite as a local database / save file structure. The database has a lot of related tables and the data has nothing to do with People or Regions or Districts, but to use a simple analogy, imagine: Region table with auto increment RegionID, RegionName column and various optional columns. District table with auto increment DistrictID, DistrictName, RegionId, and various optional columns Person table with auto increment PersonID, PersonName, DistrictID, and various optional columns So I get some data representing RegionName, DistrictName,PersonName, and other Person related data. The Region, District and/or Person may or may not be created at this point. Once again, not being the greatest with this, my thoughts would be something like: Check to see if Region exists and if so get the RegionID else create it and get RegionID Check to see if District exists and if so get the DistrictID else create it adding in RegionID from above and get DistrictID Check to see if Person exists and if so get the PersonID else create it adding in DistrictID from above and get PersonID Update Person with rest of data. In MS SQL Server I would create a stored procedure to handle all this. Only way I can see to do this with sqlite is a lot of commands. So I'm sure I'm not getting this. I've spent hours looking around on various sites but just don't feel like I'm going down the right road. Any suggestions would be greatly appreciated.

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  • Retrieving FBO data in GLSL

    - by Tom Savage
    I'm trying to get MRT working in OpenGL to try out deferred rendering. Here's the situation as I understand it. Create 3 render buffers (for example). Two RGBA8 and one Depth32. Create an FBO. Attach render buffers to FBO. ColorAttachment0/1 for color buffers, DepthAttachment for depth buffer. Bind the FBO. Draw geometry. Send data to different attachments using gl_FragData[] in the frag shader. At this point I would want to take the data in another pass using GLSL, how can a) retrieve data from the framebuffer color attachments, b) get data from the depth component.

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  • HttpWebRequest is extremely slow!

    - by Earlz
    Hello, I am using an open source library to connect to my webserver. I was concerned that the webserver was going extremely slow and then I tried doing a simple test in Ruby and I got these results Ruby program: 2.11seconds for 100 HTTP GETs C# library: 20.81seconds for 100 HTTP GETs I have profiled and found the problem to be this function: private HttpWebResponse GetRawResponse(HttpWebRequest request) { HttpWebResponse raw = null; try { raw = (HttpWebResponse)request.GetResponse(); //This line! } catch (WebException ex) { if (ex.Response is HttpWebResponse) { raw = ex.Response as HttpWebResponse; } } return raw; } The marked line is takes over 1 second to complete by itself while the ruby program making 1 request takes .3 seconds. I am also doing all of these tests on 127.0.0.1, so network bandwidth is not an issue. What could be causing this huge slow down?

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