Search Results

Search found 13341 results on 534 pages for 'obiee performance tuning'.

Page 141/534 | < Previous Page | 137 138 139 140 141 142 143 144 145 146 147 148  | Next Page >

  • 'echo' or drop out of 'programming' write HTML then start PHP code again

    - by thecoshman
    For the most part, when I want to display some HTML code to be actually rendered I would use a 'close PHP' tag, write the HTML, then open the PHP again. eg <?php // some php code ?> <p>HTML that I want displayed</p> <?php // more php code ?> But I have seen lots of people who would just use echo instead, so they would have done the above something like <?php // some php code echo("<p>HTML that I want displayed</p>"); // more php code ?> Is their any performance hit for dropping out and back in like that? I would assume not as the PHP engine would have to process the entire file either way. What about when you use the echo function in the way that dose not look like a function, eg echo "<p>HTML that I want displayed</p>" I would hope that this is purely a matter of taste, but I would like to know if I was missing out on something. I personally find the first way preferable (dropping out of PHP then back in) as it helps draw a clear distinction between PHP and HTML and also lets you make use of code highlighting and hinting for your HTML, which is always handy.

    Read the article

  • Which LINQ expression is faster

    - by Vlad Bezden
    Hi All In following code public class Person { public string Name { get; set; } public uint Age { get; set; } public Person(string name, uint age) { Name = name; Age = age; } } void Main() { var data = new List<Person>{ new Person("Bill Gates", 55), new Person("Steve Ballmer", 54), new Person("Steve Jobs", 55), new Person("Scott Gu", 35)}; // 1st approach data.Where (x => x.Age > 40).ToList().ForEach(x => x.Age++); // 2nd approach data.ForEach(x => { if (x.Age > 40) x.Age++; }); data.ForEach(x => Console.WriteLine(x)); } in my understanding 2nd approach should be faster since it iterates through each item once and first approach is running 2 times: Where clause ForEach on subset of items from where clause. However internally it might be that compiler translates 1st approach to the 2nd approach anyway and they will have the same performance. Any suggestions or ideas? I could do profiling like suggested, but I want to understand what is going on compiler level if those to lines of code are the same to the compiler, or compiler will treat it literally. Thanks in advance for your help.

    Read the article

  • Linq-to-sql Add item and a one-to-many record at once

    - by Oskar Kjellin
    I have a function where I can add articles and users can comment on them. This is done with a one to many relationship like= "commentId=>ArticleId". However when I try to add the comment to the database at the same time as I add the one to many record, the commentId is not known. Like this code: Comment comment = new Comment(); comment.Date = DateTime.UtcNow; comment.Text = text; comment.UserId = userId; db.Comments.InsertOnSubmit(comment); comment.Articles.Add(new CommentsForArticle() { ArticleId = articleId, CommentId = comment.CommentId }); The commentId will be 0 before i press submit. Is there any way arround not having to submit in between or do I simply have to cut out the part where I have a one-to-many relationship and just use a CommentTable with a column like "ArticleId". What is best in a performance perspective? I understand the underlying issue, I just want to know which solution works best.

    Read the article

  • Delphi, PGDac vs Zeos, Fetch, Lookup?

    - by durumdara
    Hi! I used Zeos to test to know: is ZTable uses fetch technics, or not? May in the future we migrate our lesser system to PGSQL, and this used now "Table" components (as BDE, but it have an SQL-like server). These tables use real cursors, a "Window" with N record, so lookup is very fast, because the Locate/Lookup is started on server, and only these N records are refreshed, no matter, how many records in the lookup table. PGSQL uses fetch technics as I know, and I tested it with a table (id int, name varchar(100)), and 1 million records. (I also trying this with mysql). The adapter is Zeos. ID, sec to find, allocated memory in bytes on client. MySQL 500000 2,761 113 196 344 1000000 3,214 225 471 232 313800 0,437 225 471 232 328066 0,468 225 471 232 276374 0,390 225 471 232 905984 1,264 225 471 232 260253 0,359 225 471 232 PGSQL 500000 3,042 113 188 184 1000000 3,744 225 463 064 313800 0,436 225 463 064 328066 0,452 225 463 064 276374 0,375 225 463 064 905984 1,295 225 463 064 260253 0,359 225 463 064 142023 0,203 225 463 064 As you see the records are fetched locally, this cause the 225 MB usage, and searches are slow a little, based where is the record we must find. I want to ask more things: a.) Is PGDAC have some technics to we can use the lookups without pay the fetch with memory and secs? b.) Or is PG ODBC driver can help in this problem with ADO? (As I know ADO can use server side cursors)? c.) Have anybody some experience with lookup tables, and performance? Is this critical question or it is not? (With client memory usage too). d.) If no chance to avoid fetch hell with lookups, what we can do? Server Side Joins, and unique code for Lookup field changing without real Lookup? Thanks for your help: dd

    Read the article

  • MySQL ORDER BY DESC is fast but ASC is very slow

    - by Pepper
    Hello, I'm completely stumped on this one. For some reason when I sort this query by DESC it's super fast, but if sorted by ASC it's extremely slow. This takes about 150 milliseconds: SELECT posts.id FROM posts USE INDEX (published) WHERE posts.feed_id IN ( 4953,622,1,1852,4952,76,623,624,10 ) ORDER BY posts.published DESC LIMIT 0, 50; This takes about 32 seconds: SELECT posts.id FROM posts USE INDEX (published) WHERE posts.feed_id IN ( 4953,622,1,1852,4952,76,623,624,10 ) ORDER BY posts.published ASC LIMIT 0, 50; The EXPLAIN is the same for both queries. id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE posts index NULL published 5 NULL 50 Using where I've tracked it down to "USE INDEX (published)". If I take that out it's the same performance both ways. But the EXPLAIN shows the query is less efficient overall. id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE posts range feed_id feed_id 4 \N 759 Using where; Using filesort And here's the table. CREATE TABLE `posts` ( `id` int(20) NOT NULL AUTO_INCREMENT, `feed_id` int(11) NOT NULL, `post_url` varchar(255) NOT NULL, `title` varchar(255) NOT NULL, `content` blob, `author` varchar(255) DEFAULT NULL, `published` int(12) DEFAULT NULL, `updated` datetime NOT NULL, `created` datetime NOT NULL, PRIMARY KEY (`id`), UNIQUE KEY `post_url` (`post_url`,`feed_id`), KEY `feed_id` (`feed_id`), KEY `published` (`published`) ) ENGINE=InnoDB AUTO_INCREMENT=196530 DEFAULT CHARSET=latin1; Is there a fix for this? Thanks!

    Read the article

  • Aggregating / Collecting AJAX requests

    - by Ganesh Shankar
    I have situation where a user can manipulate a large set of data (presented in a table) by using a bunch of filters represented as checkboxes. The page is AJAXed up so the user doesn't have to wait for a full page refresh every time they click a filter. The way it's currently implemented is by having an event handler watch all the checkboxes and request filtered data from the server when a click event is triggered. This works fine. However, there is a usability & performance issue with doing it this way. For example, if a user clicks 6 checkboxes, 6 AJAX requests are triggered and they all come back at various intervals causing the page to be updated 6 times. This will most probably annoy the user and seems rather inefficient. I want to put some kind of timeout on the event handler to do something like this: "Wait for 1 second and if there are no more filters clicked trigger the AJAX request". However, at the moment I've only been able to delay all 6 requests by 1 second. I'm not sure how to aggregate / collect the filter info into 1 AJAX request. Any suggestions would be greatly appreciated!

    Read the article

  • sybase - fails to use index unless string is hard-coded

    - by Garrett
    I'm using Sybase 12.5.3 (ASE); I'm new to Sybase though I've worked with MSSQL pretty extensively. I'm running into a scenario where a stored procedure is really very slow. I've traced the issue to a single SELECT stmt for a relatively large table. Modifying that statement dramatically improves the performance of the procedure (and reverting it drastically slows it down; i.e., the SELECT stmt is definitely the culprit). -- Sybase optimizes and uses multi-column index... fast!<br> SELECT ID,status,dateTime FROM myTable WHERE status in ('NEW','SENT') ORDER BY ID -- Sybase does not use index and does very slow table scan<br> SELECT ID,status,dateTime FROM myTable WHERE status in (select status from allowableStatusValues) ORDER BY ID The code above is an adapted/simplified version of the actual code. Note that I've already tried recompiling the procedure, updating statistics, etc. I have no idea why Sybase ASE would choose an index only when strings are hard-coded and choose a table scan when choosing from another table. Someone please give me a clue, and thank you in advance.

    Read the article

  • SQL Server Index cost

    - by yellowstar
    I have read that one of the tradeoffs for adding table indexes in SQL Server is the increased cost of insert/update/delete queries to benefit the performance of select queries. I can conceptually understand what happens in the case of an insert because SQL Server has to write entries into each index matching the new rows, but update and delete are a little more murky to me because I can't quite wrap my head around what the database engine has to do. Let's take DELETE as an example and assume I have the following schema (pardon the pseudo-SQL) TABLE Foo col1 int ,col2 int ,col3 int ,col4 int PRIMARY KEY (col1,col2) INDEX IX_1 col3 INCLUDE col4 Now, if I issue the statement DELETE FROM Foo WHERE col1=12 AND col2 > 34 I understand what the engine must do to update the table (or clustered index if you prefer). The index is set up to make it easy to find the range of rows to be removed and do so. However, at this point it also needs to update IX_1 and the query that I gave it gives no obvious efficient way for the database engine to find the rows to update. Is it forced to do a full index scan at this point? Does the engine read the rows from the clustered index first and generate a smarter internal delete against the index? It might help me to wrap my head around this if I understood better what is going on under the hood, but I guess my real question is this. I have a database that is spending a significant amount of time in delete and I'm trying to figure out what I can do about it. When I display the execution plan for the deletion, it just shows an entry for "Clustered Index Delete" on table Foo which lists in the details section the other indices that need to be updated but I don't get any indication of the relative cost of these other indices. Are they all equal in this case? Is there some way that I can estimate the impact of removing one or more of these indices without having to actually try it?

    Read the article

  • Why is MySQL with InnoDB doing a table scan when key exists and choosing to examine 70 times more ro

    - by andysk
    Hello, I'm troubleshooting a query performance problem. Here's an expected query plan from explain: mysql> explain select * from table1 where tdcol between '2010-04-13:00:00' and '2010-04-14 03:16'; +----+-------------+--------------------+-------+---------------+--------------+---------+------+---------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+--------------------+-------+---------------+--------------+---------+------+---------+-------------+ | 1 | SIMPLE | table1 | range | tdcol | tdcol | 8 | NULL | 5437848 | Using where | +----+-------------+--------------------+-------+---------------+--------------+---------+------+---------+-------------+ 1 row in set (0.00 sec) That makes sense, since the index named tdcol (KEY tdcol (tdcol)) is used, and about 5M rows should be selected from this query. However, if I query for just one more minute of data, we get this query plan: mysql> explain select * from table1 where tdcol between '2010-04-13 00:00' and '2010-04-14 03:17'; +----+-------------+--------------------+------+---------------+------+---------+------+-----------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+--------------------+------+---------------+------+---------+------+-----------+-------------+ | 1 | SIMPLE | table1 | ALL | tdcol | NULL | NULL | NULL | 381601300 | Using where | +----+-------------+--------------------+------+---------------+------+---------+------+-----------+-------------+ 1 row in set (0.00 sec) The optimizer believes that the scan will be better, but it's over 70x more rows to examine, so I have a hard time believing that the table scan is better. Also, the 'USE KEY tdcol' syntax does not change the query plan. Thanks in advance for any help, and I'm more than happy to provide more info/answer questions.

    Read the article

  • Speeding up a soap powered website

    - by ChrisRamakers
    Hi all, We're currently looking into doing some performance tweaking on a website which relies heavily on a Soap webservice. But ... our servers are located in Belgium and the webservice we connect to is locate in San Francisco so it's a long distance connection to say the least. Our website is PHP powered, using PHP's built in SoapClient class. On average a call to the webservice takes 0.7 seconds and we are doing about 3-5 requests per page. All possible request/response caching is already implemented so we are now looking at other ways to improved the connection speed. This is the code which instantiates the SoapClient, what i'm looking for now is other ways/methods to improve speed on single requestes. Anyone has idea's or suggestions? private function _createClient() { try { $wsdl = sprintf($this->config->wsUrl.'?wsdl', $this->wsdl); $client = new SoapClient($wsdl, array( 'soap_version' => SOAP_1_1, 'encoding' => 'utf-8', 'connection_timeout' => 5, 'cache_wsdl' => 1, 'trace' => 1, 'features' => SOAP_SINGLE_ELEMENT_ARRAYS )); $header_tags = array('username' => new SOAPVar($this->config->wsUsername, XSD_STRING, null, null, null, $this->ns), 'password' => new SOAPVar(md5($this->config->wsPassword), XSD_STRING, null, null, null, $this->ns)); $header_body = new SOAPVar($header_tags, SOAP_ENC_OBJECT); $header = new SOAPHeader($this->ns, 'AuthHeaderElement', $header_body); $client->__setSoapHeaders($header); } catch (SoapFault $e){ controller('Error')->error($id.': Webservice connection error '.$e->getCode()); exit; } $this->client = $client; return $this->client; }

    Read the article

  • Slow Databinding setup time in C# .NET 4.0

    - by Svisstack
    Hello, I have got a problem. I have windows forms application with dynamic generated layout, but i have a problem in performance. In this form i use DataBinding from .NET 4.0 and databinding after setup works fine, but he binding setup time for ONE control blocking my application on approx 0.7 second. I have some controls and time of binging setuping is around 2 minutes. I trying all possible solutions, I dont have any ideas without write self binding class. Why is wrong with my code? case "Boolean": { Binding b = new Binding("Checked", __bindingsource, __ep.Name); CheckBox cb = new CheckBox(); /* * HERE is the problem */ cb.DataBindings.Add(b); /* * HERE is the end of problem */ __flp.Controls.Add(cb); __bindingcontrol.AddBinding(b); break; } Without problem code lines all works fast and without binding ;-( but i want binding turn on in normal speed. PS1. I have suspended layout in generation time. PS2. I have same problem with binding TextBox'es, PictureBoxe's, CheckBox is only example. How to do that?

    Read the article

  • Why is it not good to use $_SESSION in Restful Implementations?

    - by keisimone
    Original Question: i read that for RESTful websites. it is not good to use $_SESSION. Why is it not good? how then do i properly authenticate users without looking up database all the time to check for the user's roles? I read that it is not good to use $_SESSION. http://www.recessframework.org/page/towards-restful-php-5-basic-tips I am creating a WEBSITE, not web service in PHP. and i am trying to make it more RESTful. at least in spirit. right now i am rewriting all the action to use Form tags POST and add in a hidden value called _method which would be "delete" for deleting action and "put" for updating action. however, i am not sure why it is recommended NOT to use $_SESSION. i would like to know why and what can i do to improve. To allow easy authorization checking, what i did was to after logging in the user, the username is stored in the $_SESSION. Everytime the user navigates to a page, the page would check if the username is stored inside $_SESSION and then based on the $_SESSION retrieves all the info including privileges from the database and then evaluates the authorization to access the page based on the info retrieved. Is the way I am implementing bad? not RESTful? how do i improve performance and security? Thank you.

    Read the article

  • Pros/cons of reading connection string from physical file vs Application object (ASP.NET)?

    - by HaterTot
    my ASP.NET application reads an xml file to determine which environment it's currently in (e.g. local, development, production). It checks this file every single time it opens a connection to the database, in order to know which connection string to grab from the Application Settings. I'm entering a phase of development where efficiency is becoming a concern. I don't think it's a good idea to have to read a file on a physical disk ever single time I wish to access the database (very often). I was considering storing the connection string in Application["ConnectionString"]. So the code would be public static string GetConnectionString { if (Application["ConnectionString"] == null) { XmlDocument doc = new XmlDocument(); doc.Load(HttpContext.Current.Request.PhysicalApplicationPath + "bin/ServerEnvironment.xml"); XmlElement xe = (XmlElement) xnl[0]; switch (xe.InnerText.ToString().ToLower()) { case "local": connString = Settings.Default.ConnectionStringLocal; break; case "development": connString = Settings.Default.ConnectionStringDevelopment; break; case "production": connString = Settings.Default.ConnectionStringProduction; break; default: throw new Exception("no connection string defined"); } Application["ConnectionString"] = connString; } return Application["ConnectionString"].ToString(); } I didn't design the application so I figure there must have been a reason for reading the xml file every time (to change settings while the application runs?) I have very little concept of the inner workings here. What are the pros and cons? Do you think I'd see a small performance gain by implementing the function above? THANKS

    Read the article

  • What is optimal hardware configuration for heavy load LAMP application

    - by Piotr Kochanski
    I need to run Linux-Apache-PHP-MySQL application (Moodle e-learning platform) for a large number of concurrent users - I am aiming 5000 users. By concurrent I mean that 5000 people should be able to work with the application at the same time. "Work" means not only do database reads but writes as well. The application is not very typical, since it is doing a lot of inserts/updates on the database, so caching techniques are not helping to much. We are using InnoDB storage engine. In addition application is not written with performance in mind. For instance one Apache thread usually occupies about 30-50 MB of RAM. I would be greatful for information what hardware is needed to build scalable configuration that is able to handle this kind of load. We are using right now two HP DLG 380 with two 4 core processors which are able to handle much lower load (typically 300-500 concurrent users). Is it reasonable to invest in this kind of boxes and build cluster using them or is it better to go with some more high-end hardware? I am particularly curious how many and how powerful servers are needed (number of processors/cores, size of RAM) what network equipment should be used (what kind of switches, network cards) any other hardware, like particular disc storage solutions, etc, that are needed Another thing is how to put together everything, that is what is the most optimal architecture. Clustering with MySQL is rather hard (people are complaining about MySQL Cluster, even here on Stackoverflow).

    Read the article

  • Precision of cos(atan2(y,x)) versus using complex <double>, C++

    - by Ivan
    Hi all, I'm writing some coordinate transformations (more specifically the Joukoswky Transform, Wikipedia Joukowsky Transform), and I'm interested in performance, but of course precision. I'm trying to do the coordinate transformations in two ways: 1) Calculating the real and complex parts in separate, using double precision, as below: double r2 = chi.x*chi.x + chi.y*chi.y; //double sq = pow(r2,-0.5*n) + pow(r2,0.5*n); //slow!!! double sq = sqrt(r2); //way faster! double co = cos(atan2(chi.y,chi.x)); double si = sin(atan2(chi.y,chi.x)); Z.x = 0.5*(co*sq + co/sq); Z.y = 0.5*si*sq; where chi and Z are simple structures with double x and y as members. 2) Using complex : Z = 0.5 * (chi + (1.0 / chi)); Where Z and chi are complex . There interesting part is that indeed the case 1) is faster (about 20%), but the precision is bad, giving error in the third decimal number after the comma after the inverse transform, while the complex gives back the exact number. So, the problem is on the cos(atan2), sin(atan2)? But if it is, how the complex handles that? Thanks!

    Read the article

  • Optimizing processing and management of large Java data arrays

    - by mikera
    I'm writing some pretty CPU-intensive, concurrent numerical code that will process large amounts of data stored in Java arrays (e.g. lots of double[100000]s). Some of the algorithms might run millions of times over several days so getting maximum steady-state performance is a high priority. In essence, each algorithm is a Java object that has an method API something like: public double[] runMyAlgorithm(double[] inputData); or alternatively a reference could be passed to the array to store the output data: public runMyAlgorithm(double[] inputData, double[] outputData); Given this requirement, I'm trying to determine the optimal strategy for allocating / managing array space. Frequently the algorithms will need large amounts of temporary storage space. They will also take large arrays as input and create large arrays as output. Among the options I am considering are: Always allocate new arrays as local variables whenever they are needed (e.g. new double[100000]). Probably the simplest approach, but will produce a lot of garbage. Pre-allocate temporary arrays and store them as final fields in the algorithm object - big downside would be that this would mean that only one thread could run the algorithm at any one time. Keep pre-allocated temporary arrays in ThreadLocal storage, so that a thread can use a fixed amount of temporary array space whenever it needs it. ThreadLocal would be required since multiple threads will be running the same algorithm simultaneously. Pass around lots of arrays as parameters (including the temporary arrays for the algorithm to use). Not good since it will make the algorithm API extremely ugly if the caller has to be responsible for providing temporary array space.... Allocate extremely large arrays (e.g. double[10000000]) but also provide the algorithm with offsets into the array so that different threads will use a different area of the array independently. Will obviously require some code to manage the offsets and allocation of the array ranges. Any thoughts on which approach would be best (and why)?

    Read the article

  • PHP: Profiling code and strict environment ~ Improving my coding

    - by DavidYell
    I would like to update my local working environment to be stricter in an effort to improve my code. I know that my code is okay, but as with most things there is always room for improvement. I use XAMPP on my local machine, for simplicities sake Apache Friends XAMPP (Basic Package) version 1.7.2 So I've updated my php.ini : error_reporting to be E_ALL | E_STRICT to help with the code standard. I've also enabled the XDebug extension zend_extension = "C:\xampp\php\ext\php_xdebug.dll" which seems to be working, having tested some broken code and got the nice standard orange error notice. However, having read this question, http://stackoverflow.com/questions/133686/what-is-the-best-way-to-profile-php-code and enabled the profiler, I cannot seem to create a cachegrind file. Many of the guides that I've looked at seem to think you need to install XDebug in XAMPP which leads me to think they are out of date, as XDebug is bundled with XAMPP these days. So I would appreciate it if anyone can help point me in the right direction with both configuring XDebug to output grind files, and or just a great set of default settings for the XDebug config in XAMPP. Seems there is very little documentation to go on. If people have tips on integrating these tools with Netbeans, that would be awesomesauce. I'm happy to get suggestions on other things that I can do to help tighten up my php code, both syntactically and performance wise Thanks, and apologies for the rambling question(s)! Ninja edit I should menion that I'm using named vhosts as my Apache configuration, which I think is why running XDebug on port 9000 isn't working for me. I guess I'd need to edit my vhost to include port 9000

    Read the article

  • How can I track the last location of a shipment effeciently using latest date of reporting?

    - by hash
    I need to find the latest location of each cargo item in a consignment. We mostly do this by looking at the route selected for a consignment and then finding the latest (max) time entered against nodes of this route. For example if a route has 5 nodes and we have entered timings against first 3 nodes, then the latest timing (max time) will tell us its location among the 3 nodes. I am really stuck on this query regarding performance issues. Even on few hundred rows, it takes more than 2 minutes. Please suggest how can I improve this query or any alternative approach I should acquire? Note: ATA= Actual Time of Arrival and ATD = Actual Time of Departure SELECT DISTINCT(c.id) as cid,c.ref as cons_ref , c.Name, c.CustRef FROM consignments c INNER JOIN routes r ON c.Route = r.ID INNER JOIN routes_nodes rn ON rn.Route = r.ID INNER JOIN cargo_timing ct ON c.ID=ct.ConsignmentID INNER JOIN (SELECT t.ConsignmentID, Max(t.firstata) as MaxDate FROM cargo_timing t GROUP BY t.ConsignmentID ) as TMax ON TMax.MaxDate=ct.firstata AND TMax.ConsignmentID=c.ID INNER JOIN nodes an ON ct.routenodeid = an.ID INNER JOIN contract cor ON cor.ID = c.Contract WHERE c.Type = 'Road' AND ( c.ATD = 0 AND c.ATA != 0 ) AND (cor.contract_reference in ('Generic','BP001','020-543-912')) ORDER BY c.ref ASC

    Read the article

  • Same query has nested loops when used with INSERT, but Hash Match without.

    - by AaronLS
    I have two tables, one has about 1500 records and the other has about 300000 child records. About a 1:200 ratio. I stage the parent table to a staging table, SomeParentTable_Staging, and then I stage all of it's child records, but I only want the ones that are related to the records I staged in the parent table. So I use the below query to perform this staging by joining with the parent tables staged data. --Stage child records INSERT INTO [dbo].[SomeChildTable_Staging] ([SomeChildTableId] ,[SomeParentTableId] ,SomeData1 ,SomeData2 ,SomeData3 ,SomeData4 ) SELECT [SomeChildTableId] ,D.[SomeParentTableId] ,SomeData1 ,SomeData2 ,SomeData3 ,SomeData4 FROM [dbo].[SomeChildTable] D INNER JOIN dbo.SomeParentTable_Staging I ON D.SomeParentTableID = I.SomeParentTableID; The execution plan indicates that the tables are being joined with a Nested Loop. When I run just the select portion of the query without the insert, the join is performed with Hash Match. So the select statement is the same, but in the context of an insert it uses the slower nested loop. I have added non-clustered index on the D.SomeParentTableID so that there is an index on both sides of the join. I.SomeParentTableID is a primary key with clustered index. Why does it use a nested loop for inserts that use a join? Is there a way to improve the performance of the join for the insert?

    Read the article

  • Parallel version of loop not faster than serial version

    - by Il-Bhima
    I'm writing a program in C++ to perform a simulation of particular system. For each timestep, the biggest part of the execution is taking up by a single loop. Fortunately this is embarassingly parallel, so I decided to use Boost Threads to parallelize it (I'm running on a 2 core machine). I would expect at speedup close to 2 times the serial version, since there is no locking. However I am finding that there is no speedup at all. I implemented the parallel version of the loop as follows: Wake up the two threads (they are blocked on a barrier). Each thread then performs the following: Atomically fetch and increment a global counter. Retrieve the particle with that index. Perform the computation on that particle, storing the result in a separate array Wait on a job finished barrier The main thread waits on the job finished barrier. I used this approach since it should provide good load balancing (since each computation may take differing amounts of time). I am really curious as to what could possibly cause this slowdown. I always read that atomic variables are fast, but now I'm starting to wonder whether they have their performance costs. If anybody has some ideas what to look for or any hints I would really appreciate it. I've been bashing my head on it for a week, and profiling has not revealed much.

    Read the article

  • PHP: What is an efficient way to parse a text file containing very long lines?

    - by Shaun
    I'm working on a parser in php which is designed to extract MySQL records out of a text file. A particular line might begin with a string corresponding to which table the records (rows) need to be inserted into, followed by the records themselves. The records are delimited by a backslash and the fields (columns) are separated by commas. For the sake of simplicity, let's assume that we have a table representing people in our database, with fields being First Name, Last Name, and Occupation. Thus, one line of the file might be as follows [People] = "\Han,Solo,Smuggler\Luke,Skywalker,Jedi..." Where the ellipses (...) could be additional people. One straightforward approach might be to use fgets() to extract a line from the file, and use preg_match() to extract the table name, records, and fields from that line. However, let's suppose that we have an awful lot of Star Wars characters to track. So many, in fact, that this line ends up being 200,000+ characters/bytes long. In such a case, taking the above approach to extract the database information seems a bit inefficient. You have to first read hundreds of thousands of characters into memory, then read back over those same characters to find regex matches. Is there a way, similar to the Java String next(String pattern) method of the Scanner class constructed using a file, that allows you to match patterns in-line while scanning through the file? The idea is that you don't have to scan through the same text twice (to read it from the file into a string, and then to match patterns) or store the text redundantly in memory (in both the file line string and the matched patterns). Would this even yield a significant increase in performance? It's hard to tell exactly what PHP or Java are doing behind the scenes.

    Read the article

  • Extending the .NET type system so the compiler enforces semantic meaning of primitive values in cert

    - by Drew Noakes
    I'm working with geometry a bit at the moment and am converting a lot between degrees and radians. Unfortunately, both of these are represented by double, so there's compile time warning/error if I try to pass a value in degrees where radians are expected. I believe F# has a compile-time solution for this (called units of measure.) I'd like to do something similar in C#. As another example, imagine a SQL library that accepts various query parameters as strings. It'd be good to have a way of enforcing that only clean strings were allowed to be passed in at runtime, and the only way to get a clean string was to pass through some SQL injection attack preventing logic. The obvious solution is to wrap the double/string/whatever in a new type to give it the type information the compiler needs. I'm curious if anyone has an alternative solution. If you do think wrapping is the only/best way, then please go into some of the downsides of the pattern (and any upsides I haven't mentioned too.) I'm especially concerned about the performance of abstracted primitive numeric types on my calculations at runtime.

    Read the article

  • Wrappers of primitive types in arraylist vs arrays

    - by ismail marmoush
    Hi, In "Core java 1" I've read CAUTION: An ArrayList is far less efficient than an int[] array because each value is separately wrapped inside an object. You would only want to use this construct for small collections when programmer convenience is more important than efficiency. But in my software I've already used Arraylist instead of normal arrays due to some requirements, though "The software is supposed to have high performance and after I've read the quoted text I started to panic!" one thing I can change is changing double variables to Double so as to prevent auto boxing and I don't know if that is worth it or not, in next sample algorithm public void multiply(final double val) { final int rows = getSize1(); final int cols = getSize2(); for (int i = 0; i < rows; i++) { for (int j = 0; j < cols; j++) { this.get(i).set(j, this.get(i).get(j) * val); } } } My question is does changing double to Double makes a difference ? or that's a micro optimizing that won't affect anything ? keep in mind I might be using large matrices.2nd Should I consider redesigning the whole program again ?

    Read the article

  • Is there really such a thing as a char or short in modern programming?

    - by Dean P
    Howdy all, I've been learning to program for a Mac over the past few months (I have experience in other languages). Obviously that has meant learning the Objective C language and thus the plainer C it is predicated on. So I have stumbles on this quote, which refers to the C/C++ language in general, not just the Mac platform. With C and C++ prefer use of int over char and short. The main reason behind this is that C and C++ perform arithmetic operations and parameter passing at integer level, If you have an integer value that can fit in a byte, you should still consider using an int to hold the number. If you use a char, the compiler will first convert the values into integer, perform the operations and then convert back the result to char. So my question, is this the case in the Mac Desktop and IPhone OS environments? I understand when talking about theses environments we're actually talking about 3-4 different architectures (PPC, i386, Arm and the A4 Arm variant) so there may not be a single answer. Nevertheless does the general principle hold that in modern 32 bit / 64 bit systems using 1-2 byte variables that don't align with the machine's natural 4 byte words doesn't provide much of the efficiency we may expect. For instance, a plain old C-Array of 100,000 chars is smaller than the same 100,000 ints by a factor of four, but if during an enumeration, reading out each index involves a cast/boxing/unboxing of sorts, will we see overall lower 'performance' despite the saved memory overhead?

    Read the article

  • Analyzing Web Application Speed

    - by Amy
    I'm a bit confused because the logical/programmer brain in me says that if all things are constant, the speed of a function must be constant. I am working on a PHP web application with jqGrid as a front end for showing the data. I am testing on my personal computer, so network traffic does not apply. I make an HTTP request to a PHP function, it returns the data, and then jqGrid renders it. What has me befuddled is that sometimes, Firebug reports that this is taking 300-600 milliseconds sometimes, and sometimes, it's taking 3.68 seconds. I can run the request over and over again, with very radically different response times. The query is the same. The number of users on the system is the same. No network latency. Same code. I'm not running other applications on the computer while testing. I could understand query caching improving performance on subsequent requests, but the speed is just fluctuating wildly with no rhyme or reason. So, my question is, what else can cause such variability in the response time? How can I determine what's doing it? More importantly, is there any way to get things more consistent?

    Read the article

< Previous Page | 137 138 139 140 141 142 143 144 145 146 147 148  | Next Page >