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• Using a subset of GetHashCode() to increase AzureTable performance through partitioning

  - by makerofthings7

  Generally speaking, Azure Table IO performance improves as more partitions are used (with some tradeoffs in continuation tokens and batch updates I won't go into). Since the partition key is always a string I am considering using a "natural" load balancing technique based on a subset of the GetHashCode() of the partition key, and appending this subset to the partition key itself. This will allow all direct PK/RK queries to be computed with little overhead and with ease. Batch updates may just need an intermediate to group similar PKs together prior to submission. Question: Should I use GetHashCode() to compute the partition key? Is a better function available? If I use GetHashCode() does it matter which character I use for my PK? Is there an abstraction for Azure Table and Blob storage that does this for me already?

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• Improving grepping over a huge file performance

  - by rogerio_marcio

  I have FILE_A which has over 300K lines and FILE_B which has over 30M lines. I created a bash script that greps each line in FILE_A over in FILE_B and writes the result of the grep to a new file. This whole process is taking over 5+ hours. I'm looking for suggestions on whether you see any way of improving the performance of my script. I'm using grep -F -m 1 as the grep command. FILE_A looks like this: 123456789 123455321 and FILE_B is like this: 123456789,123456789,730025400149993, 123455321,123455321,730025400126097, So with bash I have a while loop that picks the next line in FILE_A and greps it over in FILE_B. When the pattern is found in FILE_B i write it to result.txt. while read -r line; do grep -F -m1 $line 30MFile done < 300KFile Thanks a lot in advance for your help.

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• game performance

  - by iQue

  I'm making a game for android, and earlier today I was trying to add some cool stuff to my game. The problem is this thing needs like 5 timers. I build my timers like this: timer += deltaTime; if(timer >= 2.0f){ doStuff; timer -= 2.0f; } // this timers gets stuff done every 2 secs Will having to many timers like this, getting checked every frame, screw up my games performance? The effect I wanted to add was a crosshair every 2 sec, then remove it after 2 sec and do a timed animation. So an array of crosshairs dependent on a bunch of timers to be exact. This caused my game to shut down when used, so thats why Im wondering if using that many timers causes my game to flip out.

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• Video capture Performance

  - by volting

  I have noticed high CPU utilization in a number of applications (except mplayer) which read from the embedded webcam on my laptop. Bizarrely CPU utilization varies proportionately to the level of illumination present. I know that that high CPU usage has nothing to do with rendering the video, as I have written a simple app using the OpenCV library to simply grab frames from the webcam, and cpu usage is still high. I think that mplayer might be using my GPU (and the other apps aren't), but since its not an issue with rendering, I dont think this explains anything. Cheese Low light --- ~12% CPU Bright Light ---- ~63% CPU Camorama Low light --- ~7% CPU Bright Light ---- ~30% CPU Opencv C++ library, (display in a single highgui window) Low light --- ~13% CPU Bright Light ---- ~40% CPU (same test on windows 7, 4-9%) Mplayer No problem, 1-2% regardless of light levels Note: If all I want't to do is capture a feed from my webcam I would use mplayer and forget about it, but I'm developing an application which uses the OpenCV to capture a video feed among other things, performance is important.

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• perf tuning for ESX vmfs3 on RAID

  - by maruti

  looking for recommendations on ESX4 OS - VMFS version3: RAID-5 : matching the stripe size with VMFS block size? (64K, 128K etc) RAID controller options: "adaptive read ahead, write-back" on PERC 6i 90% VMs on server are Windows (2008, 2003, Vista etc, SQL 2005 etc) i have read that smaller stipes are good for writes and larger for reads. Since this is virtual env, not sure whats good.

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• perf tuning for vmfs3 on RAID

  - by maruti

  recommendations for ESX4 OS - VMFS version3: matching: RAID-5 stripe size with VMFS block size? (64K, 128K etc) enabled "adaptive read ahead, write-back" on PERC 6i 90% VMs on server are Windows (2008, 2003, Vista etc, SQL 2005 etc) i have read that smaller stipes are good for writes and larger for reads. Since this is virtual env, not sure whats good.

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• Missing processor/memory counters in the Windows XP Performance Monitor application (perfmon)

  - by Jader Dias

  Perfmon is a Windows utility that helps the developer to find bottlenecks in his applications, by measuring system counters. I was reading a perfmon tutorial and from this list of essential counters I have found the following ones on my machine: PhysicalDisk\Bytes/sec_Total Network Interface\Bytes Total/Sec\nic name But I haven't found the following counters nowhere: Processor\% Processor Time_Total Process\Working Set_Total Memory\Available MBytes Where do I find them? Note that my Windows is pt-BR (instead of en-US). Where do I find language specific documentation for windows tools like PerfMon?

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• WCF Service Layer in n-layered application: performance considerations

  - by Marconline

  Hi all. When I went to University, teachers used to say that in good structured application you have presentation layer, business layer and data layer. This is what I heard for more than 5 years. When I started working I discovered that this is true but sometimes is better to have more than just three layers. Two or three days ago I discovered this article by John Papa that explain how to use Entity Framework in layered application. According to that article you should have: UI Layer and Presentation Layer (Model View Pattern) Service Layer (WCF) Business Layer Data Access Layer Service Layer is, to me, one of the best ideas I've ever heard since I work. Your UI is then completely "diconnected" from Business and Data Layer. Now when I went deeper by looking into provided source code, I began to have some questions. Can you help me in answering them? Question #0: is this a good enterpise application template in your opinion? Question #1: where should I host the service layer? Should it be a Windows Service or what else? Question #2: in the source code provided the service layer expose just an endpoint with WSHttpBinding. This is the most interoperable binding but (I think) the worst in terms of performances (due to serialization and deserializations of objects). Do you agree? Question #3: if you agree with me at Question 2, which kind of binding would you use? Looking forward to hear from you. Have a nice weekend! Marco

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• What causes bad performance in consumer apps?

  - by Crashworks

  My Comcast DVR takes at least three seconds to respond to every remote control keypress, making the simple task of watching television into a frustrating button-mashing experience. My iPhone takes at least fifteen seconds to display text messages and crashes ¼ of the times I try to bring up the iPad app; simply receiving and reading an email often takes well over a minute. Even the navcom in my car has mushy and unresponsive controls, often swallowing successive inputs if I make them less than a few seconds apart. These are all fixed-hardware end-consumer appliances for which usability should be paramount, and yet they all fail at basic responsiveness and latency. Their software is just too slow. What's behind this? Is it a technical problem, or a social one? Who or what is responsible? Is it because these were all written in managed, garbage-collected languages rather than native code? Is it the individual programmers who wrote the software for these devices? In all of these cases the app developers knew exactly what hardware platform they were targeting and what its capabilities were; did they not take it into account? Is it the guy who goes around repeating "optimization is the root of all evil," did he lead them astray? Was it a mentality of "oh it's just an additional 100ms" each time until all those milliseconds add up to minutes? Is it my fault, for having bought these products in the first place? This is a subjective question, with no single answer, but I'm often frustrated to see so many answers here saying "oh, don't worry about code speed, performance doesn't matter" when clearly at some point it does matter for the end-user who gets stuck with a slow, unresponsive, awful experience. So, at what point did things go wrong for these products? What can we as programmers do to avoid inflicting this pain on our own customers?

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• Do or can robots cause considerable performance issues?

  - by Anicho

  So the question in the title is exactly what I am trying to find out. My case is: At work we are in a discussion with team members who seem to think bots will cause us problems relating to performance when running on our services website. Out setup: Lets say I have site www.mysite.co.uk this is a shop window to our online services which sit on www.mysiteonline.co.uk. When people search in google for mysite they see mysiteonline.co.uk as well as mysite.co.uk. Cases against stopping bots crawling: We don't store gb's of data publicly available on the web Most friendly bots, if they were to cause issues would have done so already In our instance the bots can't crawl the site because it requires username & password Stopping bots with robot .txt causes an issue with seo (ref.1) If it was a malicious bot, it would ignore robot.txt or meta tags anyway Ref 1. If we were to block mysiteonline.co.uk from having robots crawl this will affect seo rankings and make it inconvenient for users who actively search for mysite to find mysiteonline. Which we can prove is the case for a good portion of our users.

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• android game performance regarding timers

  - by iQue

  Im new to the game-dev world and I have a tendancy to over-simplify my code, and sometimes this costs me alot fo memory. Im using a custom TimerTask that looks like this: public class Task extends TimerTask { private MainGamePanel panel; public Task(MainGamePanel panel) { this.panel=panel; } /** * When the timer executes, this code is run. */ public void run() { panel.createEnemies(); } } this task calls this method from my view: public void createEnemies() { Bitmap bmp = BitmapFactory.decodeResource(getResources(), R.drawable.female); if(enemyCounter < 24){ enemies.add(new Enemy(bmp, this)); } enemyCounter++; } Since I call this in the onCreate-method instead of in my views contructor (because My enemies need to get width and height of view). Im wondering if this will work when I have multiple levels in game (start a new intent). And if this kind of timer really is the best way to add a delay between the spawning-time of my enemies performance-wise. adding code for my timer if any1 came here cus they dont understand timers: private Timer timer1 = new Timer(); private long delay1 = 5*1000; // 5 sec delay public void surfaceCreated(SurfaceHolder holder) { timer1.schedule(new Task(this), 0, delay1); //I call my timer and add the delay thread.setRunning(true); thread.start(); }

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• 12.10 visual performance using nvidia driver

  - by user100485

  My fresh ubuntu 12.10 install is slow, not something extreme but dragging windows, switching workspaces and things like that are just slow and look horrible. it feels like the fps is dropping in a game. Doing some photoshop work in windows was even a relief! This effect gets worse if I connect my external monitor. My system is an intel pentium dual core T4500 with 4gb memory and a GeForce 8200M G/integrated/SSE2 graphics chip. Nothing fancy but should be able to run ok. My "experience" in ubuntu is set to standard. (MSI cr500 laptop) I've installed the nvidia drivers, tried current and experimental and the experimental drivers seem to perform a bit better but overall bad anyway. I set the mode to adaptive in the nvidia-settings tool and it goes to maximum setting directly and doesn't come back. Using htop I found out that compiz or the X server always use a few percent of my cpu, more than I think it should and the time consumed is 5:18 for compiz, 4:33 for /usr/bin/X and 2:41 for google chrome(about 30 tabs open so not too strange I think.) What can I do to increase the visual performance cause this makes me not want to use ubuntu in public!

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• Count a row VS Save the Row count after each update

  - by SAFAD

  I want to know whether saving row count in a table is better than counting it each time of the proccess. Quick Example : A visitor goes to Group Clan, the page displays clan information and Members who have joined the group,Should the page look for all the users who joined the clan and count them, or just display the number of members already saved in table ? I think the first one is not possible to get manipulated with but IT MIGHT cost performance Your Ideas ?

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• SQL SERVER – What is Incremental Statistics? – Performance improvements in SQL Server 2014 – Part 1

  - by Pinal Dave

  This is the first part of the series Incremental Statistics. Here is the index of the complete series. What is Incremental Statistics? – Performance improvements in SQL Server 2014 – Part 1 Simple Example of Incremental Statistics – Performance improvements in SQL Server 2014 – Part 2 DMV to Identify Incremental Statistics – Performance improvements in SQL Server 2014 – Part 3 Statistics are considered one of the most important aspects of SQL Server Performance Tuning. You might have often heard the phrase, with related to performance tuning. “Update Statistics before you take any other steps to tune performance”. Honestly, I have said above statement many times and many times, I have personally updated statistics before I start to do any performance tuning exercise. You may agree or disagree to the point, but there is no denial that Statistics play an extremely vital role in the performance tuning. SQL Server 2014 has a new feature called Incremental Statistics. I have been playing with this feature for quite a while and I find that very interesting. After spending some time with this feature, I decided to write about this subject over here. New in SQL Server 2014 – Incremental Statistics Well, it seems like lots of people wants to start using SQL Server 2014′s new feature of Incremetnal Statistics. However, let us understand what actually this feature does and how it can help. I will try to simplify this feature first before I start working on the demo code. Code for all versions of SQL Server Here is the code which you can execute on all versions of SQL Server and it will update the statistics of your table. The keyword which you should pay attention is WITH FULLSCAN. It will scan the entire table and build brand new statistics for you which your SQL Server Performance Tuning engine can use for better estimation of your execution plan. UPDATE STATISTICS TableName(StatisticsName) WITH FULLSCAN Who should learn about this? Why? If you are using partitions in your database, you should consider about implementing this feature. Otherwise, this feature is pretty much not applicable to you. Well, if you are using single partition and your table data is in a single place, you still have to update your statistics the same way you have been doing. If you are using multiple partitions, this may be a very useful feature for you. In most cases, users have multiple partitions because they have lots of data in their table. Each partition will have data which belongs to itself. Now it is very common that each partition are populated separately in SQL Server. Real World Example For example, if your table contains data which is related to sales, you will have plenty of entries in your table. It will be a good idea to divide the partition into multiple filegroups for example, you can divide this table into 3 semesters or 4 quarters or even 12 months. Let us assume that we have divided our table into 12 different partitions. Now for the month of January, our first partition will be populated and for the month of February our second partition will be populated. Now assume, that you have plenty of the data in your first and second partition. Now the month of March has just started and your third partition has started to populate. Due to some reason, if you want to update your statistics, what will you do? In SQL Server 2012 and earlier version You will just use the code of WITH FULLSCAN and update the entire table. That means even though you have only data in third partition you will still update the entire table. This will be VERY resource intensive process as you will be updating the statistics of the partition 1 and 2 where data has not changed at all. In SQL Server 2014 You will just update the partition of Partition 3. There is a special syntax where you can now specify which partition you want to update now. The impact of this is that it is smartly merging the new data with old statistics and update the entire statistics without doing FULLSCAN of your entire table. This has a huge impact on performance. Remember that the new feature in SQL Server 2014 does not change anything besides the capability to update a single partition. However, there is one feature which is indeed attractive. Previously, when table data were changed 20% at that time, statistics update were triggered. However, now the same threshold is applicable to a single partition. That means if your partition faces 20% data, change it will also trigger partition level statistics update which, when merged to your final statistics will give you better performance. In summary If you are not using a partition, this feature is not applicable to you. If you are using a partition, this feature can be very helpful to you. Tomorrow: We will see working code of SQL Server 2014 Incremental Statistics. Reference: Pinal Dave (http://blog.sqlauthority.com)Filed under: PostADay, SQL, SQL Authority, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, T SQL Tagged: SQL Statistics, Statistics

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• Increase application performance

  - by Prayos

  I'm writing a program for a company that will generate a daily report for them. All of the data that they use for this report is stored in a local SQLite database. For this report, the utilize pretty much every bit of the information in the database. So currently, when I query the datbase, I retrieve everything, and store the information in lists. Here's what I've got: using (var dataReader = _connection.Select(query)) { if (dataReader.HasRows) { while (dataReader.Read()) { _date.Add(Convert.ToDateTime(dataReader["date"])); _measured.Add(Convert.ToDouble(dataReader["measured_dist"])); _bit.Add(Convert.ToDouble(dataReader["bit_loc"])); _psi.Add(Convert.ToDouble(dataReader["pump_press"])); _time.Add(Convert.ToDateTime(dataReader["timestamp"])); _fob.Add(Convert.ToDouble(dataReader["force_on_bit"])); _torque.Add(Convert.ToDouble(dataReader["torque"])); _rpm.Add(Convert.ToDouble(dataReader["rpm"])); _pumpOneSpm.Add(Convert.ToDouble(dataReader["pump_1_strokes_pm"])); _pumpTwoSpm.Add(Convert.ToDouble(dataReader["pump_2_strokes_pm"])); _pullForce.Add(Convert.ToDouble(dataReader["pull_force"])); _gpm.Add(Convert.ToDouble(dataReader["flow"])); } } } I then utilize these lists for the calculations. Obviously, the more information that is in this database, the longer the initial query will take. I'm curious if there is a way to increase the performance of the query at all? Thanks for any and all help. EDIT One of the report rows is called Daily Drilling Hours. For this calculation, I use this method: // Retrieves the timestamps where measured depth == bit depth and PSI >= 50 public double CalculateDailyProjectDrillingHours(DateTime date) { var dailyTimeStamps = _time.Where((t, i) => _date[i].Equals(date) && _measured[i].Equals(_bit[i]) && _psi[i] >= 50).ToList(); return _dailyDrillingHours = Convert.ToDouble(Math.Round(TimeCalculations(dailyTimeStamps).TotalHours, 2, MidpointRounding.AwayFromZero)); } // Checks that the interval is less than 10, then adds the interval to the total time private static TimeSpan TimeCalculations(IList<DateTime> timeStamps) { var interval = new TimeSpan(0, 0, 10); var totalTime = new TimeSpan(); TimeSpan timeDifference; for (var j = 0; j < timeStamps.Count - 1; j++) { if (timeStamps[j + 1].Subtract(timeStamps[j]) <= interval) { timeDifference = timeStamps[j + 1].Subtract(timeStamps[j]); totalTime = totalTime.Add(timeDifference); } } return totalTime; }

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• Learn about the Performance and Tuning Improvements made to Oracle's E-Business Suite

  Cliff speaks with Ahmed Alomari, Sr. Director, Oracle Applications Performance about key performance improvements that have been made to Oracle's E-Business Suite 11.5.10, the top 3 tuning tips to improve Workflow performance, why customers should adopt Oracle Applications Tablespace Model, Java monitoring, and J2SE 5 performance improvements.

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• JVM tuning on Amazon EC2

  - by Shadowman

  We will be deploying a production application to Amazon EC2 very shortly. Initially, we'll just be using a "small" instance, but have plans to scale up not long afterwards. My question is, has any investigation been done on JVM tuning for the EC2 environment? Are there any specific changes that we should make to our JVM parameters to compensate for quirks/characteristics of Amazon EC2? Or, do the normal tuning methodologies apply here as they would in a physical environment? Our application will be deployed on Tomcat 6.x. It is built using JBoss Seam 2.2.x, and uses PostgreSQL 8.x as the backend database. Any advice you can give is greatly appreciated!

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• Programming with midi, and tuning notes to specific frequencies

  - by froggie0106

  I am working on a project in which I need to be able to generate midi notes of varying frequencies with as much accuracy as possible. I originally tried to write my program in Java, but it turns out that the sound.midi package does not support changing the tunings of notes unless the frequencies are Equal Tempered frequencies (or at least it didn't in 1.4, and I haven't been able to find evidence that this has been fixed in recent versions). I have been trying to find a more appropriate language/library to accomplish this task, but since this is my first time programming with MIDI and my need for specific tuning functionality is essential, I have been having considerable trouble finding exactly what I need. I am looking for advice from people who have experience writing MIDI programs as to what languages are useful, especially for tuning notes to specific frequencies. Any links to websites with API docs and example code would also be extremely helpful.

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• need for tcp fine-tuning on heavily used proxy server

  - by Vijay Gharge

  Hi all, I am using squid like Internet proxy server on RHEL 4 update 6 & 8 with quite heavy load i.e. 8k established connections during peak hour. Without depending much on application provider's expertise I want to achieve maximum o/p from linux. W.r.t. that I have certain questions as following: How to find out if there is scope for further tcp fine-tuning (without exhausting available resources) as the benchmark values given by vendor looks poor! Is there any parameter value that is available from OS / network stack that will show me the results. If at all there is scope, how shall I identify & configure OS tcp stack parameters i.e. using sysctl or any specific parameter Post tuning how shall I clearly measure performance enhancement / degradation ?

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• How to use caching to increase render performance?

  - by Christian Ivicevic

  First of all I am going to cover the basic design of my 2d tile-based engine written with SDL in C++, then I will point out what I am up to and where I need some hints. Concept of my engine My engine uses the concept of GameScreens which are stored on a stack in the main game class. The main methods of a screen are usually LoadContent, Render, Update and InitMultithreading. (I use the last one because I am using v8 as a JavaScript bridge to the engine. The main game loop then renders the top screen on the stack (if there is one; otherwise, it exits the game) - actually it calls the render methods, but stores all items to be rendered in a list. After gathering all this information the methods like SDL_BlitSurface are called by my GameUIRenderer which draws the enqueued content and then draws some overlay. The code looks like this: while(Game is running) { Handle input if(Screens on stack == 0) exit Update timer etc. Clear the screen Peek the screen on the stack and collect information on what to render Actually render the enqueue screen stuff and some overlay etc. Flip the screen } The GameUIRenderer uses as hinted a std::vector<std::shared_ptr<ImageToRender>> to hold all necessary information described by this class: class ImageToRender { private: SDL_Surface* image; int x, y, w, h, xOffset, yOffset; }; This bunch of attributes is usually needed if I have a texture atlas with all tiles in one SDL_Surface and then the engine should crop one specific area and draw this to the screen. The GameUIRenderer::Render() method then just iterates over all elements and renders them something like this: std::for_each( this->m_vImageVector.begin(), this->m_vImageVector.end(), [this](std::shared_ptr<ImageToRender> pCurrentImage) { SDL_Rect rc = { pCurrentImage->x, pCurrentImage->y, 0, 0 }; // For the sake of simplicity ignore offsets... SDL_Rect srcRect = { 0, 0, pCurrentImage->w, pCurrentImage->h }; SDL_BlitSurface(pCurrentImage->pImage, &srcRect, g_pFramework->GetScreen(), &rc); } ); this->m_vImageVector.clear(); Current ideas which need to be reviewed The specified approach works really good and IMHO it is really has a good structure, however the performance could be definitely increased. I would like to know what do you suggest, how to implement efficient caching of surfaces etc so that there is no need to redraw the same scene over and over again? The map itself would be almost static, only when the player moves, we would need to move the map. Furthermore animated entities would either require updates of the whole map or updates of only the specific areas the entities are currently moving in. My first approaches were to include a flag IsTainted which should be used by the GameUIRenderer to decide whether to redraw everything or use cached version (or to not render anything so that we do not have to Clear the screen and let the last frame persist). However this seems to be quite messy if I have to manually handle in my Render method of the screen class if something has changed or not.

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• JBoss AS Performance Tuning de Francesco Marchioni, critique par Gomes Rodrigues Antonio

  Bonjour, Vous pouvez trouver sur http://java.developpez.com/livres/?p...L9781849514026 la critique de l'excellent livre "JBoss AS Performance Tuning" [IMG]http://images-eu.amazon.com/images/P/184951402X.01.LZZZZZZZ.jpg[/IMG] Comme il couvre plus que seulement le tuning de JBoss, je préfère mettre cette discussion ici A propos du livre, il couvre la création d'un test de charge avec Jmeter, le tuning de JBoss, le profiling de l'application et de la JVM, de l'OS ... Il se lit plutôt bien et on y trouve pas mal d'informations Si vous avez un avis sur ce livre, je serais intéressé de le connaitre...

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• New Whitepaper: Oracle E-Business Suite on Exadata

  - by Steven Chan

  Our Maximum Availability Architecture (MAA) team has quietly been amassing a formidable set of whitepapers about the Oracle Exadata Database Machine.  They're available here:MAA Best Practices - Exadata Database MachineIf you're one of the lucky ones with access to this hardware platform, you'll be pleased to hear that the MAA team has just published a new whitepaper with best practices for EBS environments:Oracle E-Business Suite on ExadataThis whitepaper covers the following topics:Getting to Exadata -- a high level overview of fresh installation on, and migration to, Exadata Database Machine with pointers to more detailed documentation High Availability and Disaster Recovery -- an overview of our MAA best practices with pointers to our detailed MAA Best Practices documentation Performance and Scalability -- best practices for running Oracle E-Business Suite on Exadata Database Machine based on our internal testing

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• theoretical and practical matrix multiplication FLOP

  - by mjr

  I wrote traditional matrix multiplication in c++ and tried to measure and compare its theoretical and practical FLOP. As I know inner loop of MM has 2 operation therefore simple MM theoretical Flops is 2*n*n*n (2n^3) but in practice I get something like 4n^3 + number of operation which is 2 i.e. 6n^3 also if I just try to add up only one array a[i][j]++ practical flops then calculate like 3n^3 and not n^3 as you see again it is 2n^3 +1 operation and not 1 operation * n^3 . This is in case if I use 1D array in three nested loops as Matrix multiplication and compare flop, practical flop is the same (near) the theoretical flop and depend exactly as the number of operation in inner loop.I could not find the reason for this behaviour. what is the reason in both case? I know that theoretical flop is not the same as practical one because of some operations like load etc. system specification: Intel core2duo E4500 3700g memory L2 cache 2M x64 fedora 17 sample results: Matrix matrix multiplication 512*512 Real_time: 1.718368 Proc_time: 1.227672 Total flpops: 807,107,072 MFLOPS: 657.429016 Real_time: 3.608078 Proc_time: 3.042272 Total flpops: 807,024,448 MFLOPS: 265.270355 theoretical flop: 2*512*512*512=268,435,456 Practical flops= 6*512^3 =807,107,072 Using 1 dimensional array float d[size][size]:512 or any size for (int j = 0; j < size; ++j) { for (int k = 0; k < size; ++k) { d[k]=d[k]+e[k]+f[k]+g[k]+r; } } Real_time: 0.002288 Proc_time: 0.002260 Total flpops: 1,048,578 MFLOPS: 464.027161 theroretical flop: *4n^2=4*512^2=1,048,576* practical flop : 4n^2+overhead (other operation?)=1,048,578 3 loop version: Real_time: 1.282257 Proc_time: 1.155990 Total flpops: 536,872,000 MFLOPS: 464.426117 theoretical flop:4n^3 = 536,870,912 practical flop: *4n^3=4*512^3+overheads(other operation?)=536,872,000* thank you

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• Strategy to find bottleneck in a network

  - by Simone

  Our enterprise is having some problem when the number of incoming request goes beyond a certain amount. To make things simpler, we have N websites that uses, amongst other, a local web service. This service is hosted by IIS, and it's a .NET 4.0 (C#) application executed in a farm. It's REST-oriented, built around OpenRasta. As already mentioned, by stress testing it with JMeter, we've found that beyond a certain amount of request the service's performance drop. Anyway, this service is, amongst other, a client itself of other 3 distinct web services and also a client for a DB server, so it's not very clear what really is the culprit of this abrupt decay. In turn, these 3 other web services are installed in our farm too, and client of other DB servers (and services, possibly, that are out of my team control). What strategy do you suggest to try to locate where the bottleneck(s) are? Do you have any high-level suggestions?

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• T-SQL Tuesday #13: Clarifying Requirements

  - by Alexander Kuznetsov

  When we transform initial ideas into clear requirements for databases, we typically have to make the following choices: Frequent maintenance vs doing it once. As we are clarifying the requirements, we need to determine whether we want to concinue spending considerable time maintaining the system, or if we want to finish it up and move on to other tasks. Race car maintenance vs installing electric wiring is my favorite analogy for this kind of choice. In some cases we need to sqeeze every last bit...(read more)

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