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• SQL SERVER – Find Most Expensive Queries Using DMV

  - by pinaldave

  The title of this post is what I can express here for this quick blog post. I was asked in recent query tuning consultation project, if I can share my script which I use to figure out which is the most expensive queries are running on SQL Server. This script is very basic and very simple, there are many different versions are available online. This basic script does do the job which I expect to do – find out the most expensive queries on SQL Server Box. SELECT TOP 10 SUBSTRING(qt.TEXT, (qs.statement_start_offset/2)+1, ((CASE qs.statement_end_offset WHEN -1 THEN DATALENGTH(qt.TEXT) ELSE qs.statement_end_offset END - qs.statement_start_offset)/2)+1), qs.execution_count, qs.total_logical_reads, qs.last_logical_reads, qs.total_logical_writes, qs.last_logical_writes, qs.total_worker_time, qs.last_worker_time, qs.total_elapsed_time/1000000 total_elapsed_time_in_S, qs.last_elapsed_time/1000000 last_elapsed_time_in_S, qs.last_execution_time, qp.query_plan FROM sys.dm_exec_query_stats qs CROSS APPLY sys.dm_exec_sql_text(qs.sql_handle) qt CROSS APPLY sys.dm_exec_query_plan(qs.plan_handle) qp ORDER BY qs.total_logical_reads DESC -- logical reads -- ORDER BY qs.total_logical_writes DESC -- logical writes -- ORDER BY qs.total_worker_time DESC -- CPU time You can change the ORDER BY clause to order this table with different parameters. I invite my reader to share their scripts. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, SQL, SQL Authority, SQL Optimization, SQL Performance, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, SQLAuthority News, SQLServer, T SQL, Technology Tagged: SQL DMV

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• SQLAuthority News – 18 Seconds of Fame – My PASS Experience

  - by pinaldave

  Happy Holidays to All of YOU! Life is full of little and happy surprises. I think Christmas and Santa are based on it. I just received very interesting email earlier today, I had no idea about it. Earlier this year, I had visited Seattle to attend SQLPASS – read the complete summary over here: SQLAuthority News – SQLPASS Nov 8-11, 2010-Seattle – An Alternative Look at Experience. While I was walking down, someone has stopped me and asked if they can talk to me for 15 seconds, I said yes and they had shot quick movie with mobile. The conversation was very quick and I had forgotten about it. Today I received email from one of the blog reader about it being on YouTube. Honestly, I did not know if this was ever going to be on YouTube. I am surprised and thrilled. Watch my 18 seconds fame movie. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: About Me, Pinal Dave, SQL, SQL Authority, SQL Optimization, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, SQLAuthority Author Visit, T SQL, Technology

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• Starting a Java activity in Unity3d Android

  - by Matthew Pavlinsky

  I wrote a small Java activity extension of UnityPlayerActivity similar to what is described in the Unity docs. It has a method for displaying a song picking interface using an ACTION_GET_CONTENT intent. I start this activity using startActivityForResult() and it absolutely kills the performance of my Unity game when it is finished, it drops to about .1 FPS afterwords. I've changed removed the onActivityResult function and even tried starting the activity from inside an onKeyDown event in Java to make sure my method of starting the activity from Unity was not the problem. Heres the code in a basic sense: package com.company.product; import com.unity3d.player.UnityPlayerActivity; import com.unity3d.player.UnityPlayer; import android.os.Bundle; import android.util.Log; import android.content.Intent; public class SongPickerActivity extends UnityPlayerActivity { private Intent myIntent; final static int PICK_SONG = 1; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); Log.i("SongPickerActivity", "OnCreate"); myIntent = new Intent(Intent.ACTION_GET_CONTENT); myIntent.setType("audio/*"); } public void Pick() { Log.i("SongPickerActivity", "Pick"); startActivityForResult(myIntent, PICK_SONG); } @Override protected void onActivityResult(int requestCode, int resultCode, Intent data) { super.onActivityResult(requestCode, resultCode, data); } } This is causing me a bit more of a headache than it should and I would be thankful for any sort of advice. Does anyone have any experience with using custom activities in Unity Android or any insight on why this is happening or how to resolve this?

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• Python — Time complexity of built-in functions versus manually-built functions in finite fields

  - by stackuser

  Generally, I'm wondering about the advantages versus disadvantages of using the built-in arithmetic functions versus rolling your own in Python. Specifically, I'm taking in GF(2) finite field polynomials in string format, converting to base 2 values, performing arithmetic, then output back into polynomials as string format. So a small example of this is in multiplication: Rolling my own: def multiply(a,b): bitsa = reversed("{0:b}".format(a)) g = [(b<<i)*int(bit) for i,bit in enumerate(bitsa)] return reduce(lambda x,y: x+y,g) Versus the built-in: def multiply(a,b): # a,b are GF(2) polynomials in binary form .... return a*b #returns product of 2 polynomials in gf2 Currently, operations like multiplicative inverse (with for example 20 bit exponents) take a long time to run in my program as it's using all of Python's built-in mathematical operations like // floor division and % modulus, etc. as opposed to making my own division, remainder, etc. I'm wondering how much of a gain in efficiency and performance I can get by building these manually (as shown above). I realize the gains are dependent on how well the manual versions are built, that's not the question. I'd like to find out 'basically' how much advantage there is over the built-in's. So for instance, if multiplication (as in the example above) is well-suited for base 10 (decimal) arithmetic but has to jump through more hoops to change bases to binary and then even more hoops in operating (so it's lower efficiency), that's what I'm wondering. Like, I'm wondering if it's possible to bring the time down significantly by building them myself in ways that maybe some professionals here have already come across.

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• SQL SERVER – Plan Cache and Data Cache in Memory

  - by pinaldave

  I get following question almost all the time when I go for consultations or training. I often end up providing the scripts to my clients and attendees. Instead of writing new blog post, today in this single blog post, I am going to cover both the script and going to link to original blog posts where I have mentioned about this blog post. Plan Cache in Memory USE AdventureWorks GO SELECT [text], cp.size_in_bytes, plan_handle FROM sys.dm_exec_cached_plans AS cp CROSS APPLY sys.dm_exec_sql_text(plan_handle) WHERE cp.cacheobjtype = N'Compiled Plan' ORDER BY cp.size_in_bytes DESC GO Further explanation of this script is over here: SQL SERVER – Plan Cache – Retrieve and Remove – A Simple Script Data Cache in Memory USE AdventureWorks GO SELECT COUNT(*) AS cached_pages_count, name AS BaseTableName, IndexName, IndexTypeDesc FROM sys.dm_os_buffer_descriptors AS bd INNER JOIN ( SELECT s_obj.name, s_obj.index_id, s_obj.allocation_unit_id, s_obj.OBJECT_ID, i.name IndexName, i.type_desc IndexTypeDesc FROM ( SELECT OBJECT_NAME(OBJECT_ID) AS name, index_id ,allocation_unit_id, OBJECT_ID FROM sys.allocation_units AS au INNER JOIN sys.partitions AS p ON au.container_id = p.hobt_id AND (au.TYPE = 1 OR au.TYPE = 3) UNION ALL SELECT OBJECT_NAME(OBJECT_ID) AS name, index_id, allocation_unit_id, OBJECT_ID FROM sys.allocation_units AS au INNER JOIN sys.partitions AS p ON au.container_id = p.partition_id AND au.TYPE = 2 ) AS s_obj LEFT JOIN sys.indexes i ON i.index_id = s_obj.index_id AND i.OBJECT_ID = s_obj.OBJECT_ID ) AS obj ON bd.allocation_unit_id = obj.allocation_unit_id WHERE database_id = DB_ID() GROUP BY name, index_id, IndexName, IndexTypeDesc ORDER BY cached_pages_count DESC; GO Further explanation of this script is over here: SQL SERVER – Get Query Plan Along with Query Text and Execution Count Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, SQL, SQL Authority, SQL Optimization, SQL Performance, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL Tagged: SQL Memory

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• Is 1GB RAM with integrated graphics sufficient for Unity 3D on 12.04?

  - by Anwar Shah

  I have been using Ubuntu since Hardy Heron (8.04). I used Natty, Oneiric with Unity. But When I recently (more than 1 month now) upgraded My Ubuntu to Precise (12.04), the performance of my laptop is not satisfactory. It is too unresponsive compared to older releases. For example, the Unity in 12.04 is very unresponsive. Sometimes, it requires 2 seconds to show up the dash (which was not the case with Natty, though people always saying that Natty's version of Unity is buggiest). I am assuming that, May be my 1GB RAM now becomes too low to run Unity of Precise. But I also think, Since Unity is improved in Precise, It may not be the case. So, I am not sure. Do you have any ideas? Will upgrading RAM fix it? How much I need if upgrade is required? Laptop model: "Lenovo 3000 Y410" Graphic : "Intel GMA X3100" on Intel 965GM Chipset. RAM/Memory : "1 GB DDR2" (1 slot empty). Swap space : 1.1GB Resolution: 1280x800 widescreen Shared RAM for Graphics: 256 MB as below output suggests $ dmesg | grep AGP [ 0.825548] agpgart-intel 0000:00:00.0: AGP aperture is 256M @ 0xd0000000

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• Slower site with the *same* configuration than a mirror copy…?

  - by Rosamunda Rosamunda

  I´ve got this Drupal site (ligadelconsorcista.org) that I have to move it from one server to another. The reason was that my older host even when it was pretty decent, it started a couple of months now to have many short downtimes, wich drove me crazy. The thing is that I´ve made a sort of mirror copy of the site: I´ve copied all the files exactly the same, and after that I´ve imported the database. The problem is that the new site connects much slower than my old hosting! (the new one is mediatemple) I´ve contacted their support and they tell me that there are several factors that can contribute to that... but that has nothing to do with their hosting service. The thing is that I don´t even know where to start looking for the problem. Notes: The new configuration is the same that the one I had with the older hosting account. Today I´ve set an account with cloudflare´s CDN to try to solve the problem. Even if the CDN is configured ok (I´ve asked their help desk) it won´t add any performance improvement. Any clues of what may I do about this? Thanks!!

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• Caching WCF javascript proxy on browser

  - by oazabir

  When you use WCF services from Javascript, you have to generate the Javascript proxies by hitting the Service.svc/js. If you have five WCF services, then it means five javascripts to download. As browsers download javascripts synchronously, one after another, it adds latency to page load and slows down page rendering performance. Moreover, the same WCF service proxy is downloaded from every page, because the generated javascript file is not cached on browser. Here is a solution that will ensure the generated Javascript proxies are cached on browser and when there is a hit on the service, it will respond with HTTP 304 if the Service.svc file has not changed. Here’s a Fiddler trace of a page that uses two WCF services. You can see there are two /js hits and they are sequential. Every visit to the same page, even with the same browser session results in making those two hits to /js. Second time when the same page is browsed: You can see everything else is cached, except the WCF javascript proxies. They are never cached because the WCF javascript proxy generator does not produce the necessary caching headers to cache the files on browser. Here’s an HttpModule for IIS and IIS Express which will intercept calls to WCF service proxy. It first checks if the service is changed since the cached version on the browser. If it has not changed then it will return HTTP 304 and not go through the service proxy generation process. Thus it saves some CPU on server. But if the request is for the first time and there’s no cached copy on browser, it will deliver the proxy and also emit the proper cache headers to cache the response on browser. http://www.codeproject.com/Articles/360437/Caching-WCF-javascript-proxy-on-browser Don’t forget to vote.

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• Where is a good place to start to learn about custom caching in .Net

  - by John

  I'm looking to make some performance enhancements to our site, but I'm not sure exactly where to begin. We have some custom object caching, but I think that we can do better. Our Business We aggregate news stories on a news type of web site. We get approximately 500-1000 new stories per week. We have index pages that show various lists of the items and details pages that show the individual stories. Our Current Use case: Getting an Individual Story User makes a request The Data Access Layer(DAL) checks to see if the item is in cache and if item is fresh (15 minutes). If the item is not in cache or is not fresh, retrieve the item from SQL Server, save to cache and return to user. Problems with this approach The pull nature of caching means that users have to pay the waiting cost every time that the cache is refreshed. Once a story is published, it changes infrequently and I think that we should replace the pull model with something better. My initial thoughts My initial thought is that stories should ALL be stored locally in some type of dictionary. (Cache or is there another, better way?). If the story is not found, then make a trip to the database, update the local dictionary and send the item back. Since there may be occasional updates to stories, this should be an entirely process from the user. I watched a video by Brent Ozar, How StackOverflow Scales SQL Server, in which Brent states "the fastest database query is the one that you don't make". Where do I start? At this point, I don't know exactly what the solution is. Is it caching? Is there a better way of using local storage? Do I use a Dictionary, OrderedDictionary, List ? It seems daunting and I'm just looking for some good starting points to learn more about how to do this type of optimization.

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• Perfomance of 8 bit operations on 64 bit architechture

  - by wobbily_col

  I am usually a Python / Database programmer, and I am considering using C for a problem. I have a set of sequences, 8 characters long with 4 possible characters. My problem involves combining sets of these sequences and filtering which sets match a criteria. The combinations of 5 run into billions of rows and takes around an hour to run. So I can represent each sequence as 2 bytes. If I am working on a 64 bit architechture will I gain any advantage by keeping these data structures as 2 bytes when I generate the combinations, or will I be as well storing them as 8 bytes / double ? (64 bit = 8 x 8) If I am on a 64 bit architecture, all registers will be 64 bit, so in terms of operations that shouldn´t be any faster (please correct me if I am wrong). Will I gain anything from the smaller storage requirements - can I fit more combinations in memory, or will they all take up 64 bits anyway? And finally, am I likley to gain anything coding in C. I have a first version, which stores the sequence as a small int in a MySQL database. It then self joins the tabe to itself a number of times in order to generate all the possible combinations. The performance is acceptable, depending on how many combinations are generated. I assume the database must involve some overhead.

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• Is there a better way to consume an ASP.NET Web API call in an MVC controller?

  - by davidisawesome

  In a new project I am creating for my work I am creating a fairly large ASP.NET Web API. The api will be in a separate visual studio solution that also contains all of my business logic and database interactions, Model classes as well. In the test application I am creating (which is asp.net mvc4), I want to be able to hit an api url I defined from the control and cast the return JSON to a Model class. The reason behind this is that I want to take advantage of strongly typing my views to a Model. This is all still in a proof of concept stage, so I have not done any performance testing on it, but I am curious if what I am doing is a good practice, or if I am crazy for even going down this route. Here is the code on the client controller: public class HomeController : Controller { protected string dashboardUrlBase = "http://localhost/webapi/api/StudentDashboard/"; public ActionResult Index() //This view is strongly typed against User { //testing against Joe Bob string adSAMName = "jBob"; WebClient client = new WebClient(); string url = dashboardUrlBase + "GetUserRecord?userName=" + adSAMName; //'User' is a Model class that I have defined. User result = JsonConvert.DeserializeObject<User>(client.DownloadString(url)); return View(result); } . . . } If I choose to go this route another thing to note is I am loading several partial views in this page (as I will also do in subsequent pages). The partial views are loaded via an $.ajax call that hits this controller and does basically the same thing as the code above: Instantiate a new WebClient Define the Url to hit Deserialize the result and cast it to a Model Class. So it is possible (and likely) I could be performing the same actions 4-5 times for a single page. Is there a better method to do this that will: Let me keep strongly typed views. Do my work on the server rather than on the client (this is just a preference since I can write C# faster than I can write javascript).

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• How to diagnose Ubuntu CPU spikes / IO wait?

  - by Jeff Welling

  I'm using Ubuntu and every couple minutes it goes unresponsive for a half second to a full second, which isn't normally a problem but makes trying to code extremely frustrating when your trying to hit backspace or navigate the code and nothing is happening. The problem is, the freezes are so brief that top doesn't have time to show me what is spiking the CPU (assuming something is, but I don't know what else could cause this). Does anyone know how to troubleshoot this performance issue? Edit: I've tried login in with Gnome Classic (No Effects) instead of Unity but it still freezes up every once in awhile. Edit: The CPU graph doesn't seem to be showing any actual spikes so it seems you were right and my original diagnosis of CPU spikes being the problem was incorrect, I now suspect IO wait. I don't recall this happening for the brief few weeks I had Windows 7 Starter running on it though, which leads me to believe it isn't (just?) the hardware.. is there anything I can tweak to improve this? I'm using an Acer Aspire One D257, with Ubuntu 11.10. Edit: Output of dmesg is at http://paste.ubuntu.com/1060054/ and kern.log is at http://paste.ubuntu.com/1060055/

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• Ubuntu Slow - What architecture does the Windows Installer install?

  - by Benjamin Yep

  I feel absolutely limited by using Windows, and I need to switch to a Unix environment. I once installed Red Hat on my lappie (screen + external monitor setup; 4GB ram; x64; runs fast) and it worked fine, but I saw that the computer cluster that is the birthplace of my unix knowledge switched to Ubuntu, so naturally I follow. To the point. When I installed Ubuntu onto my machine via the Windows Installer, it ran quite slow. Opening Firefox takes about 8-9 seconds, it freezes up often, unable to handle its own background processes. I saw in a thread that, perhaps, it is running slow because the Windows Installer is installing an x64 version. Of course, my computer has had no performance issues in the past(except that time with the trojans but you know, know one is perfect ;) ) Anyways, I uninstalled Ubuntu, freeing up the max allocated memory it took up, and continue to be sad, trapped in my MS world with only a buggy Cygwin, any assistance is greatly appreciated! :) Thanks ~Ben

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• ATI Radeon 5800 series dual monitor unity not 3D accelerated

  - by Victor S

  When I had a single monitor setup, without Xinerama, with my current setup of Ubuntu 11.10, ATI 5800 series card, Unity showed transparencies, shadows, etc. (although graphics was reported as 'Standard' in the control/settings panel). Having switched to a dual monitor setup, dell 24" UltraSharp and a smaller Acer monitor, Unity shows only as 2d, even though I'm not loggin in to that display manager. WebGL performance is very sluggish, I'm getting the impression that the processor is doing all the work and the card isn't even accessible even though the drivers are installed (from the ubuntu repository, I did not compile custom drivers). Any tips on how to enable full 3D accelerationn and video card support. Here is my xorg.conf file: Section "Monitor" Identifier "0-DFP3" Option "VendorName" "ATI Proprietary Driver" Option "ModelName" "Generic Autodetecting Monitor" Option "DPMS" "true" Option "PreferredMode" "1680x1050" Option "TargetRefresh" "60" Option "Position" "0 0" Option "Rotate" "normal" Option "Disable" "false" EndSection Section "Monitor" Identifier "0-DFP4" Option "VendorName" "ATI Proprietary Driver" Option "ModelName" "Generic Autodetecting Monitor" Option "DPMS" "true" Option "PreferredMode" "1920x1200" Option "TargetRefresh" "60" Option "Position" "0 0" Option "Rotate" "normal" Option "Disable" "false" EndSection Section "Screen" Identifier "Default Screen" DefaultDepth 24 SubSection "Display" EndSubSection EndSection Section "Screen" Identifier "amdcccle-Screen[1]-0" Device "amdcccle-Device[1]-0" DefaultDepth 24 SubSection "Display" Viewport 0 0 Depth 24 EndSubSection EndSection Section "Screen" Identifier "amdcccle-Screen[1]-1" Device "amdcccle-Device[1]-1" DefaultDepth 24 SubSection "Display" Viewport 0 0 Depth 24 EndSubSection EndSection Section "Module" Load "glx" EndSection Section "ServerLayout" Identifier "amdcccle Layout" Screen 0 "amdcccle-Screen[1]-0" 0 0 Screen "amdcccle-Screen[1]-1" 1920 0 EndSection Section "Device" Identifier "amdcccle-Device[1]-0" Driver "fglrx" Option "Monitor-DFP4" "0-DFP4" BusID "PCI:1:0:0" EndSection Section "Device" Identifier "amdcccle-Device[1]-1" Driver "fglrx" Option "Monitor-DFP3" "0-DFP3" BusID "PCI:1:0:0" Screen 1 EndSection Section "ServerFlags" Option "Xinerama" "on" EndSection More info: fglrxinfo display: :0 screen: 0 OpenGL vendor string: ATI Technologies Inc. OpenGL renderer string: ATI Radeon HD 5800 Series OpenGL version string: 4.1.11005 Compatibility Profile Context

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• Why is rvalue write in shared memory array serialised?

  - by CJM

  I'm using CUDA 4.0 on a GPU with computing capability 2.1. One of my device functions is the following: device void test(int n, int* itemp) // itemp is shared memory pointer { const int tid = threadIdx.x; const int bdim = blockDim.x; int i, j, k; bool flag = 0; itemp[tid] = 0; for(i=tid; i<n; i+=bdim) { // { code that produces some values of "flag" } } itemp[tid] = flag; } Each thread is checking some conditions and producing a 0/1 flag. Then each thread is writing flag at the tid-th location of a shared int array. The write statement "itemp[tid] = flag;" gets serialized -- though "itemp[tid] = 0;" is not. This is causing huge performance lag which technically should not be there -- I want to avoid it. Please help.

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• The clock problem - to if or not to if?

  - by trejder

  Let's say, we have a simple digital clock. To "power" it, we use a routine executed every second. We update seconds part in it. But, what about minutes and hours part? What is better / more professional / offers better performance: Ignore all checking and update hour, minute and seconds part each time, every second. Use if + a variable for checking, if 60 (or 3600) seconds passed and update minute / hour part only at that precise moments. This leads us to a question, what is better -- unnecessary drawings (first approach) or extra ifs? I've just spotted a Javascript digital clock, one of millions similar on one of billions pages. And I noticed that all three parts (hours, minutes and seconds) are updated every second, though first changes its value only once per 3600 seconds and second once per 60 seconds. I'm not to experienced developer, so I might me wrong. But everything, what I've learnt up until now, tells me, that if are far better then executing drawing / refreshing sequences only to draw the same content.

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• Cuda driver, CPU/GPU performances issue

  - by elect

  I implemented a RNS Montgomery exponentiation in Cuda and on cpu for comparison. Everything nice everything fine. It runs on just one SM. However I am going to tell you some strange regression in both cpu/gpu performances. During the devoloping, about two month ago, I was using Cuda 5 preview on Ubuntu 11.04 64b. In this time, I reach the following performances: cpu 460ms gpu 120ms Then one day when I turn on the pc, the graphical environment didnt start. I dont know which was the problem, however I switched to the console and installed again the Cuda driver. At the following boot performances changed: cpu 310ms gpu 80ms I was like Q.Q...uhm ok, nice to see this, but I was wondering how that could be possible However, I went then in holiday for 10 days and I continued developing and optimizing on my notebook (but not the same part of the code, some additional stuff) When I was back, I just updated the source files, and performances came back to 460/120ms.. I couldnt believe it, I tried to install Cuda 5 RC, updating the video driver too... nothing changed... I checked Debug/Release, Cuda computability, but the problem seems being somewhere else.. Looking around the net I found this, I am pretty sure it must have something to do with the driver, because the performance change affected both cpu and gpu Do you have some tips/ideas/suggestions?

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• My first blog post…

  - by steveh99999

  I’ve been meaning to start a blog for a while now, (OK, for several years…..) - finally now, here it begins First post, something really simple but, a wise-man once told me about the best way to improve SQL server performance. Store Less Data. That's it.. that's all there is to it... Over the years, I've seen the following :- -  a 200Gb database which held 3 days data. Once business requirements changed, we were able to hold only 1 days data in this database. -  a table developed by DBAs to hold application table cardinality information - that information was collected at 2 hour intervals every day for 7 years ! After 7 years the DBA space-info table had become the largest table in the database - 60 million rows !  It was a simple change to remove alot of the historical intra-day data and change the schedule to run only once per evening. Suddenly that table held 6 million rows instead of 60 million.... - lots of backup and restore history held in msdb. See this post by Brent Ozar for more details on this issue. Imagine how much faster the backups, DBCC Checks and reindexes ran when the above 3 changes were implemented ?   How often do you review your big databases \ tables to see if you’re actually holding only data that is really required by the business ?

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• Why is quicksort better than other sorting algorithms in practice?

  - by Raphael

  This is a repost of a question on cs.SE by Janoma. Full credits and spoils to him or cs.SE. In a standard algorithms course we are taught that quicksort is O(n log n) on average and O(n²) in the worst case. At the same time, other sorting algorithms are studied which are O(n log n) in the worst case (like mergesort and heapsort), and even linear time in the best case (like bubblesort) but with some additional needs of memory. After a quick glance at some more running times it is natural to say that quicksort should not be as efficient as others. Also, consider that students learn in basic programming courses that recursion is not really good in general because it could use too much memory, etc. Therefore (and even though this is not a real argument), this gives the idea that quicksort might not be really good because it is a recursive algorithm. Why, then, does quicksort outperform other sorting algorithms in practice? Does it have to do with the structure of real-world data? Does it have to do with the way memory works in computers? I know that some memories are way faster than others, but I don't know if that's the real reason for this counter-intuitive performance (when compared to theoretical estimates).

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• Use a SQL Database for a Desktop Game

  - by sharethis

  Developing a Game Engine I am planning a computer game and its engine. There will be a 3 dimensional world with first person view and it will be single player for now. The programming language is C++ and it uses OpenGL. Data Centered Design Decision My design decision is to use a data centered architecture where there is a global event manager and a global data manager. There are many components like physics, input, sound, renderer, ai, ... Each component can trigger and listen to events. Moreover, each component can read, edit, create and remove data. The question is about the data manager. Whether to Use a Relational Database Should I use a SQL Database, e.g. SQLite or MySQL, to store the game data? This contains virtually all game content like items, characters, inventories, ... Except of meshes and textures which are even more performance related, so I will keep them in memory. Is a SQL database fast enough to use it for realtime reading and writing game informations, like the position of a moving character? I also need to care about cross-platform compatibility. Aside from keeping everything in memory, what alternatives do I have? Advantages Would Be The advantages of using a relational database like MySQL would be the data orientated structure which allows fast computation. I would not need objects for representing entities. I could easily query data of objects near the player needed for rendering. And I don't have to take care about data of objects far away. Moreover there would be no need for savegames since the hole game state is saved in the database. Last but not least, expanding the game to an online game would be relative easy because there already is a place where the hole game state is stored.

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• HTML5 - Does it have the power to handle a large 2D game with a huge world?

  - by user15858

  I have been using XNA game studio, but due to private reasons (as well as the ability to publish anywhere & my heavy interest in isogenic engine), I would like to switch to HTML5. However, I have very high 2D graphic demands for my game. The game itself will have a HDD size of anywhere between 6GB (min) to 12GB (max) which would be a full game deployed offline. The size of the images aren't significantly large, so streaming would be entirely possible if only those assets required were streamed as needed. The game has a massive file size because of the sheer amount of content. For some images or spritesheets, they would be quite massive. (ex. a very large Dragon, which if animated in a spritesheet would be split into two 4096x4096 sheets or one 8192x8192 sheet). Most assets would be very small, and about 7MB for a full character with 15 animations in every direction (all animations not required immediately) so in the size of a few hundred KB to download before the game loads. My question, however, is if the graphical power of HTML5 is enough to animate several characters on screen at once, when it flips through frames quite rapidly. All my sprites have about 25 frames per animation, 5 directions (a spritesheet for each direction & animation), and run at 30fps. Upon changing direction, animation, or a new character entering, spritesheets would change and be constantly loading/unloading. If I pack all directions in a single sheet, it would be about 2048x2048 per sheet. Most frameworks have no problem with this, but I am afraid from what I read that HTML5's graphical capabilities will limit me. Since it takes significant time simply to animate characters in any language, I'd like a quick answer.

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• Desktop runs very slick, animations are all fast and flawless. Moving windows around, however, is very laggy. Why?

  - by Muu

  This isn't a question about Ubuntu being laggy in general - not at all, in fact, it's very slick and fast for me. Clicking the "Workspace Switcher" in the dock performs the animation immediately and very smoothly. Switching between workspaces with the arrow keys - again, flawlessly. My computer has a resolution of 2560x1440 on a 27" display (no, not an Apple product - though my monitor has the same panel that Apple use in their cinema displays). It's powered by an Nvidia GeForce GTX 470 - easily enough to handle it - and an Intel i3. Hardware is not the issue. I am running Ubuntu 11.10 (upgraded from 11.04). I had the same issue in 11.04. I'm running the "NVIDIA accelerated graphics driver (post-release updates) (version current-updates)" from the additional drivers dialogue. Two drivers have been suggested to me via that dialogue and I've tried both - same effect with each. The driver is "activated and currently in use". Any other information required, let me know and I'll post it. I'm a programmer who works with Linux daily (both as a job and as an interest) so technical instructions are fine. I've noticed that Compiz uses a lot of CPU when moving windows around and it's memory usage is relatively high (though possibly expected for Compiz): 1671 user 20 0 478m 286m 33m S 1 7.3 12:44.05 compiz And one more thing - occasionally moving windows around is fast. But it only happens when all applications are closed, and even then it sometimes doesn't. Something must be interfering, but what? I'll try and find out but in the meantime, any suggestions are much appreciated :-)

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• Java single Array best choice for accessing pixels for manipulation?

  - by Petrol

  I am just watching this tutorial https://www.youtube.com/watch?v=HwUnMy_pR6A and the guy (who seems to be pretty competent) is using a single array to store and access the pixels of his to-be-rendered image. I was wondering if this really is the best way to do this. The alternative of Multi-Array does have one pointer more, but Arrays do have an O(1) for accessing each index and calculating the index in a single array seems to take one addition and one multiplication operation per pixel. And if Multi-Arrays really are bad, can't you use something with Hashing to avoid those addition and multiplication operations? EDIT: here is his code... public class Screen { private int width, height; public int[] pixels; public Screen(int width, int height) { this.width = width; this.height = height; // creating array the size of one index/int for every pixel // single array has better performance than multi-array pixels = new int[width * height]; } public void render() { for (int y = 0; y < height; y++) { for (int x = 0; x < width; x++) { pixels[x + y * width] = 0xff00ff; } } } }

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• What is the Relative Performance of Pseudo-Class and Custom Selectors?

  - by James Wiseman

  It's my understanding that, in terms of selector speed, that #ID selectors are fastest, followed by element selectors, and then .class selectors. I have always assumed that pseudo-class selectors and custom selectors (those in the form ':selector') are similar to .class selectors, but I realised that I'm just not sure. I realise that this does depend on the complexity of the code within the pseudo-class/custom selector, so I guess I'd like to know the answer with this excluded as factor. Any help would be appreciated. Thanks.

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• Is there a performance disadvantage for WPF''s Control properties?

  - by Joan Venge

  I am learning WPF and it seems like some properties like Content are of type Object. When you have a very complex UI with 1000s of controls, would this be a problem with boxing, etc? I see that this provides a lot of power (having Content to take anything), but just thought I should ask people's opinions about this.

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