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  • Why do I get rows of zeros in my 2D fft?

    - by Nicholas Pringle
    I am trying to replicate the results from a paper. "Two-dimensional Fourier Transform (2D-FT) in space and time along sections of constant latitude (east-west) and longitude (north-south) were used to characterize the spectrum of the simulated flux variability south of 40degS." - Lenton et al(2006) The figures published show "the log of the variance of the 2D-FT". I have tried to create an array consisting of the seasonal cycle of similar data as well as the noise. I have defined the noise as the original array minus the signal array. Here is the code that I used to plot the 2D-FT of the signal array averaged in latitude: import numpy as np from numpy import ma from matplotlib import pyplot as plt from Scientific.IO.NetCDF import NetCDFFile ### input directory indir = '/home/nicholas/data/' ### get the flux data which is in ### [time(5day ave for 10 years),latitude,longitude] nc = NetCDFFile(indir + 'CFLX_2000_2009.nc','r') cflux_southern_ocean = nc.variables['Cflx'][:,10:50,:] cflux_southern_ocean = ma.masked_values(cflux_southern_ocean,1e+20) # mask land nc.close() cflux = cflux_southern_ocean*1e08 # change units of data from mmol/m^2/s ### create an array that consists of the seasonal signal fro each pixel year_stack = np.split(cflux, 10, axis=0) year_stack = np.array(year_stack) signal_array = np.tile(np.mean(year_stack, axis=0), (10, 1, 1)) signal_array = ma.masked_where(signal_array > 1e20, signal_array) # need to mask ### average the array over latitude(or longitude) signal_time_lon = ma.mean(signal_array, axis=1) ### do a 2D Fourier Transform of the time/space image ft = np.fft.fft2(signal_time_lon) mgft = np.abs(ft) ps = mgft**2 log_ps = np.log(mgft) log_mgft= np.log(mgft) Every second row of the ft consists completely of zeros. Why is this? Would it be acceptable to add a randomly small number to the signal to avoid this. signal_time_lon = signal_time_lon + np.random.randint(0,9,size=(730, 182))*1e-05 EDIT: Adding images and clarify meaning The output of rfft2 still appears to be a complex array. Using fftshift shifts the edges of the image to the centre; I still have a power spectrum regardless. I expect that the reason that I get rows of zeros is that I have re-created the timeseries for each pixel. The ft[0, 0] pixel contains the mean of the signal. So the ft[1, 0] corresponds to a sinusoid with one cycle over the entire signal in the rows of the starting image. Here are is the starting image using following code: plt.pcolormesh(signal_time_lon); plt.colorbar(); plt.axis('tight') Here is result using following code: ft = np.fft.rfft2(signal_time_lon) mgft = np.abs(ft) ps = mgft**2 log_ps = np.log1p(mgft) plt.pcolormesh(log_ps); plt.colorbar(); plt.axis('tight') It may not be clear in the image but it is only every second row that contains completely zeros. Every tenth pixel (log_ps[10, 0]) is a high value. The other pixels (log_ps[2, 0], log_ps[4, 0] etc) have very low values.

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  • Using imtophat in Matlab

    - by jaff12
    I'm trying to do top hat filtering in matlab. The imtophat function looks promising, but I have no idea how to use it. I dont have a lot of work with Matlab before. I am trying to look find basically small spots several pixels wide that are local max in my 2 dimensional array.

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  • How to read time from recorded surveillance camera video?

    - by stressed_geek
    I have a problem where I have to read the time of recording from the video recorded by a surveillance camera. The time shows up on the top-left area of the video. Below is a link to screen grab of the area which shows the time. Also, the digit color(white/black) keeps changing during the duration of the video. http://i55.tinypic.com/2j5gca8.png Please guide me in the direction to approach this problem. I am a Java programmer so would prefer an approach through Java. EDIT: Thanks unhillbilly for the comment. I had looked at the Ron Cemer OCR library and its performance is much below our requirement. Since the ocr performance is less than desired, I was planning to build a character set using the screen grabs for all the digits, and using some image/pixel comparison library to compare the frame time with the character-set which will show a probabilistic result after comparison. So I was looking for a good image comparison library(I would be OK with a non-java library which I can run using the command-line). Also any advice on the above approach would be really helpful.

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  • Extracting DCT coefficients from encoded images and video

    - by misha
    Is there a way to easily extract the DCT coefficients (and quantization parameters) from encoded images and video? Any decoder software must be using them to decode block-DCT encoded images and video. So I'm pretty sure the decoder knows what they are. Is there a way to expose them to whomever is using the decoder? I'm implementing some video quality assessment algorithms that work directly in the DCT domain. Currently, the majority of my code uses OpenCV, so it would be great if anyone knows of a solution using that framework. I don't mind using other libraries (perhaps libjpeg, but that seems to be for still images only), but my primary concern is to do as little format-specific work as possible (I don't want to reinvent the wheel and write my own decoders). I want to be able to open any video/image (H.264, MPEG, JPEG, etc) that OpenCV can open, and if it's block DCT-encoded, to get the DCT coefficients. In the worst case, I know that I can write up my own block DCT code, run the decompressed frames/images through it and then I'd be back in the DCT domain. That's hardly an elegant solution, and I hope I can do better. Presently, I use the fairly common OpenCV boilerplate to open images: IplImage *image = cvLoadImage(filename); // Run quality assessment metric The code I'm using for video is equally trivial: CvCapture *capture = cvCaptureFromAVI(filename); while (cvGrabFrame(capture)) { IplImage *frame = cvRetrieveFrame(capture); // Run quality assessment metric on frame } cvReleaseCapture(&capture); In both cases, I get a 3-channel IplImage in BGR format. Is there any way I can get the DCT coefficients as well?

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  • Finding center of fingerprints.

    - by an_ant
    If we suppose that every fingerprint is made of concentric curves (ellipses or circles) - and I'm aware of the fact that not every fingerprint is - how can I find center of those concentric curves? Let's take this "ideal" fingerprint and try to find out its center ... My approaches were to try: Find the spectrum through columns/rows of the image and try to find columns/rows that maximize particular band of the spectrum. I thought that column going through the center would have most regular pattern of changing amplitudes - therefore, most recognizible harmonic. My second approach was to try to count the changes of black-and-white also through the columns and rows, and to maximize that amount among rows and columns also. While these methods work to the some extant, with some additional filtering, they fail, when fingerprint is "not ideal as this one is". Can you think of any different approach? Are there standard ways to do it?

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  • Efficiently separating Read/Compute/Write steps for concurrent processing of entities in Entity/Component systems

    - by TravisG
    Setup I have an entity-component architecture where Entities can have a set of attributes (which are pure data with no behavior) and there exist systems that run the entity logic which act on that data. Essentially, in somewhat pseudo-code: Entity { id; map<id_type, Attribute> attributes; } System { update(); vector<Entity> entities; } A system that just moves along all entities at a constant rate might be MovementSystem extends System { update() { for each entity in entities position = entity.attributes["position"]; position += vec3(1,1,1); } } Essentially, I'm trying to parallelise update() as efficiently as possible. This can be done by running entire systems in parallel, or by giving each update() of one system a couple of components so different threads can execute the update of the same system, but for a different subset of entities registered with that system. Problem In reality, these systems sometimes require that entities interact(/read/write data from/to) each other, sometimes within the same system (e.g. an AI system that reads state from other entities surrounding the current processed entity), but sometimes between different systems that depend on each other (i.e. a movement system that requires data from a system that processes user input). Now, when trying to parallelize the update phases of entity/component systems, the phases in which data (components/attributes) from Entities are read and used to compute something, and the phase where the modified data is written back to entities need to be separated in order to avoid data races. Otherwise the only way (not taking into account just "critical section"ing everything) to avoid them is to serialize parts of the update process that depend on other parts. This seems ugly. To me it would seem more elegant to be able to (ideally) have all processing running in parallel, where a system may read data from all entities as it wishes, but doesn't write modifications to that data back until some later point. The fact that this is even possible is based on the assumption that modification write-backs are usually very small in complexity, and don't require much performance, whereas computations are very expensive (relatively). So the overhead added by a delayed-write phase might be evened out by more efficient updating of entities (by having threads work more % of the time instead of waiting). A concrete example of this might be a system that updates physics. The system needs to both read and write a lot of data to and from entities. Optimally, there would be a system in place where all available threads update a subset of all entities registered with the physics system. In the case of the physics system this isn't trivially possible because of race conditions. So without a workaround, we would have to find other systems to run in parallel (which don't modify the same data as the physics system), other wise the remaining threads are waiting and wasting time. However, that has disadvantages Practically, the L3 cache is pretty much always better utilized when updating a large system with multiple threads, as opposed to multiple systems at once, which all act on different sets of data. Finding and assembling other systems to run in parallel can be extremely time consuming to design well enough to optimize performance. Sometimes, it might even not be possible at all because a system just depends on data that is touched by all other systems. Solution? In my thinking, a possible solution would be a system where reading/updating and writing of data is separated, so that in one expensive phase, systems only read data and compute what they need to compute, and then in a separate, performance-wise cheap, write phase, attributes of entities that needed to be modified are finally written back to the entities. The Question How might such a system be implemented to achieve optimal performance, as well as making programmer life easier? What are the implementation details of such a system and what might have to be changed in the existing EC-architecture to accommodate this solution?

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  • multi user web game with scheduled processing?

    - by Rooq
    I have an idea for a game which I am in the process of designing, but I am struggling to establish if the way I plan to implement it is possible. The game is a text based sports management simulation. This will require players to take certain actions through a web browser which will interact with a database - adding/updating and selecting. Most of the code required to be executed at this point will be fairly straightforward. The main processing will take place by applications which are scheduled to run on the server at certain times. These apps will process transactions added by the players and also perform some automatic processing based on the game date. My plan was to use an SQL server database (at last count I require about 20 tables) and VB.net for all the coding (coming from a mainframe programming background this language is the simplist for me to get to grips with). I will also need a scheduling tool on the server. Can anyone tell me if what I am planning is feasible before I dive into the actual coding stage of my project?

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  • Installing Oracle Event Processing 11g by Antoney Reynolds

    - by JuergenKress
    Earlier this month I was involved in organizing the Monument Family History Day. It was certainly a complex event, with dozens of presenters, guides and 100s of visitors. So with that experience of a complex event under my belt I decided to refresh my acquaintance with Oracle Event Processing (CEP). CEP has a developer side based on Eclipse and a runtime environment. Server install The server install is very straightforward (documentation). It is recommended to use the JRockit JDK with CEP so the steps to set up a working CEP server environment are: Download required software JRockit - I used Oracle “JRockit 6 - R28.2.5” which includes “JRockit Mission Control 4.1” and “JRockit Real Time 4.1”. Oracle Event Processor - I used “Complex Event Processing Release 11gR1 (11.1.1.6.0)” Install JRockit Run the JRockit installer, the download is an executable binary that just needs to be marked as executable. Install CEP Unzip the downloaded file Run the CEP installer, the unzipped file is an executable binary that may need to be marked as executable. Choose a custom install and add the examples if needed. It is not recommended to add the examples to a production environment but they can be helpful in development. Developer Install The developer install requires several steps (documentation). A developer install needs access to the software for the server install, although JRockit isn’t necessary for development use. Read the full article by Antony Reynolds. SOA & BPM Partner Community For regular information on Oracle SOA Suite become a member in the SOA & BPM Partner Community for registration please visit  www.oracle.com/goto/emea/soa (OPN account required) If you need support with your account please contact the Oracle Partner Business Center. Blog Twitter LinkedIn Mix Forum Technorati Tags: SOA Community,Oracle SOA,Oracle BPM,Community,OPN,Jürgen Kress,CEP,Reynolds

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  • Parallelize incremental processing in Tabular #ssas #tabular

    - by Marco Russo (SQLBI)
    I recently came in a problem trying to improve the parallelism of Tabular processing. As you know, multiple tables can be processed in parallel, whereas the processing of several partitions within the same table cannot be parallelized. When you perform an incremental update by adding only new rows to existing table, what you really do is adding rows to a partition, so adding rows to many tables means adding rows to several partitions. The particular condition you have in this case is that every partition in which you add rows belongs to a different table. Adding rows implies using the ProcessAdd command; its QueryBinding parameter specifies a SQL syntax to read new rows, otherwise the original query specified for the partition will be used, and it could generate duplicated data if you don’t have a dynamic behavior on the SQL side. If you create the required XMLA code manually, you will find that the QueryBinding node that should be part of the ProcessAdd command has to be moved out from ProcessAdd in case you are using a Batch command with more than one Process command (which is the reason why you want to use a single batch: run multiple process operations in parallel!). If you use AMO (Analysis Management Objects) you will find that this combination is not supported, even if you don’t have a syntax error compiling the code, but you might obtain this error at execution time: The syntax for the 'Process' command is incorrect. The 'Bindings' keyword cannot appear under a 'Process' command if the 'Process' command is a part of a 'Batch' command and there are more than one 'Process' commands in the 'Batch' or the 'Batch' command contains any out of line related information. In this case, the 'Bindings' keyword should be a part of the 'Batch' command only. If this is happening to you, the best solution I’ve found is manipulating the XMLA code generated by AMO moving the Binding nodes in the right place. A more detailed description of the issue and the code required to send a correct XMLA batch to Analysis Services is available in my article Parallelize ProcessAdd with AMO. By the way, the same technique (and code) can be used also if you have the same problem in a Multidimensional model.

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  • Command Pattern refactor for input processing?

    - by Casey
    According to Game Coding Complete 4th. ed. processing input via the following is considered unmanagable and inflexible. But does not show an example. I've used the Command pattern to represent GUI button commands but could not figure out how to represent the input from the keyboard and/or mouse. if(g_keyboard->KeyDown(KEY_ESC)) { quit = true; return; } //Processing if(g_keyboard->KeyDown(KEY_T)) { g_show_test_gateway = !g_show_test_gateway; } if(g_mouse->ButtonDown(a2de::Mouse::BUTTON2)) { g_selected_part = GWPart::PART_NONE; SetMouseImageToPartImage(); } ResetButtonStates(); g_prevButton = g_curButton; g_curButton = GetButtonHovered(); if(g_curButton) { g_mouse->SetImageToDefault(); if(g_mouse->ButtonDown(a2de::Mouse::BUTTON1) || g_mouse->ButtonPress(a2de::Mouse::BUTTON1)) { ButtonPressCommand curCommand(g_curButton); curCommand.Execute(); } else if(g_mouse->ButtonUp(a2de::Mouse::BUTTON1)) { if(g_prevButton == g_curButton) { ButtonReleaseCommand curCommand(g_curButton); curCommand.Execute(); if(g_curButton->GetType() == "export") { ExportCommand curCommand(g_curButton, *g_gateway); curCommand.Execute(); } } else { ResetButtonStates(); } } else { ButtonHoverCommand curCommand(g_curButton); curCommand.Execute(); } } else { g_status_message.clear(); SetMouseImageToPartImage(); if(g_mouse->ButtonDown(a2de::Mouse::BUTTON1)) { CreatePartCommand curCommand(*g_gateway, g_selected_part, a2de::Vector2D(g_mouse->GetX(), g_mouse->GetY())); curCommand.Execute(); } }

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  • Question regarding Readability vs Processing Time

    - by Jordy
    I am creating a flowchart for a program with multiple sequential steps. Every step should be performed if the previous step is succesful. I use a c-based programming language so the lay-out would be something like this: METHOD 1: if(step_one_succeeded()) { if(step_two_succeeded()) { if(step_three_succeeded()) { //etc. etc. } } } If my program would have 15+ steps, the resulting code would be terribly unfriendly to read. So I changed my design and implemented a global errorcode that I keep passing by reference, make everything more readable. The resulting code would be something like this: METHOD 2: int _no_error = 0; step_one(_no_error); if(_no_error == 0) step_two(_no_error); if(_no_error == 0) step_three(_no_error); if(_no_error == 0) step_two(_no_error); The cyclomatic complexibility stays the same. Now let's say there are N number of steps. And let's assume that checking a condition is 1 clock long and performing a step doesn't take up time. The processing speed of Method1 can be anywhere between 1 and N. The processing speed of Method2 however is always equal to N-1. So Method1 will be faster most of the time. Which brings me to my question, is it bad practice to sacrifice time in order to make the code more readable? And why (not)?

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  • Customizing the processing of ListItems for asp:RadioButtonList with "Flow" layout and "Horizontal"

    - by evovision
    Hi, recently I was asked to add an ability to pad specific elements from each other to a certain distance in RadioButtonList control. Not quite common everyday task I would say :)   Ok, let's get started!   Prerequisites: ASP.NET Page having RadioButtonList control with RepeatLayout="Flow" RepeatDirection="Horizontal" properties set.   Implementation:  The underlying data was coming from another source, so the only fast way to add meta information about padding was the text value itself (yes, not very optimal solution): Id = 1, Name = "This is first element" and for padding we agreed to use <space/> meta tag: Id = 2, Name = "<space padcount="30px"/>This is second padded element"   To handle items rendering in RadioButtonList control I've created custom class and subclassed from it:    public class CustomRadioButtonList : RadioButtonList    {        private Action<ListItem, HtmlTextWriter> _preProcess;         protected override void RenderItem(ListItemType itemType, int repeatIndex, RepeatInfo repeatInfo, HtmlTextWriter writer)        {            if (_preProcess != null)            {                _preProcess(this.Items[repeatIndex], writer);            }             base.RenderItem(itemType, repeatIndex, repeatInfo, writer);        }         public void SetPrePrenderItemFunction(Action<ListItem, HtmlTextWriter> func)        {            _preProcess = func;        }    }   It is pretty straightforward approach, the key is to override RenderItem method. Class has SetPrePrenderItemFunction method which is used to pass custom processing function that takes 2 parameters: ListItem and HtmlTextWriter objects.   Now update existing RadioButtonList control in Default.aspx: add this to beginning of the page:   <%@ Register Namespace="Sample.Controls" TagPrefix="uc1" %>   and update the control to:   <uc1:CustomRadioButtonList ID="customRbl" runat="server" DataValueField="Id" DataTextField="Name"            RepeatLayout="Flow" RepeatDirection="Horizontal"></uc1:CustomRadioButtonList>   Now, from codebehind of the page:   Add regular expression that will be used for parsing:   private Regex _regex = new Regex(@"(?:[<]space padcount\s*?=\s*?(?:'|"")(?<padcount>\d+)(?:(?:\s+)?px)?(?:'|"")\s*?/>)(?<content>.*)?", RegexOptions.IgnoreCase | RegexOptions.Compiled);   and finally setup the processing function in Page_Load:   protected void Page_Load(object sender, EventArgs e)    {        customRbl.DataSource = DataObjects;         customRbl.SetPrePrenderItemFunction((listItem, writer) =>        {            Match match = _regex.Match(listItem.Text);            if (match.Success)            {                writer.Write(string.Format(@"<span style=""padding-left:{0}"">Extreme values: </span>", match.Groups["padcount"].Value + "px"));                 // if you need to pad listitem use code below                //x.Attributes.CssStyle.Add("padding-left", match.Groups["padcount"].Value + "px");                 // remove meta tag from text                listItem.Text = match.Groups["content"].Value;            }        });         customRbl.DataBind();    }   That's it! :)   Run the attached sample application:     P.S.: of course several other approaches could have been used for that purpose including events and the functionality for processing could also be embedded inside control itself. Current solution suits slightly better due some other reasons for situation where it was used, in your case consider this as a kick start for your own implementation :)   Source application: CustomRadioButtonList.zip

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  • Exitus Acta Probat: The Post-Processing Module

    - by Phil Factor
    Sometimes, one has to make certain ethical compromises to ensure the success of a corporate IT project. Exitus Acta Probat (literally 'the result validates the deeds' meaning that the ends justify the means)It was a while back, whilst working as a Technical Architect for a well-known international company, that I was given the task of designing the architecture of a rather specialized accounting system. We'd tried an off-the-shelf (OTS) Windows-based solution which crashed with dispiriting regularity, and didn't quite do what the business required. After a great deal of research and planning, we commissioned a Unux-based system that used X-terminals for the desktops of  the participating staff. X terminals are now obsolete, but were then hot stuff; stripped-down Unix workstations that provided client GUIs for networked applications long before the days of AJAX, Flash, Air and DHTML. I've never known a project go so smoothly: I'd been initially rather nervous about going the Unix route, believing then that  Unix programmers were excitable creatures who were prone to  indulge in role-play enactments of elves and wizards at the weekend, but the programmers I met from the company that did the work seemed to be rather donnish, earnest, people who quickly grasped our requirements and were faultlessly professional in their work.After thinking lofty thoughts for a while, there was considerable pummeling of keyboards by our suppliers, and a beautiful robust application was delivered to us ahead of dates.Soon, the department who had commissioned the work received shiny new X Terminals to replace their rather depressing lavatory-beige PCs. I modestly hung around as the application was commissioned and deployed to the department in order to receive the plaudits. They didn't come. Something was very wrong with the project. I couldn't put my finger on the problem, and the users weren't doing any more than desperately and futilely searching the application to find a fault with it.Many times in my life, I've come up against a predicament like this: The roll-out of an application goes wrong and you are hearing nothing that helps you to discern the cause but nit-*** noise. There is a limit to the emotional heat you can pack into a complaint about text being in the wrong font, or an input form being slightly cramped, but they tried their best. The answer is, of course, one that every IT executive should have tattooed prominently where they can read it in emergencies: In Vino Veritas (literally, 'in wine the truth', alcohol loosens the tongue. A roman proverb) It was time to slap the wallet and get the department down the pub with the tab in my name. It was an eye-watering investment, but hedged with an over-confident IT director who relished my discomfort. To cut a long story short, The real reason gushed out with the third round. We had deprived them of their PCs, which had been good for very little from the pure business perspective, but had provided them with many hours of happiness playing computer-based minesweeper and solitaire. There is no more agreeable way of passing away the interminable hours of wage-slavery than minesweeper or solitaire, and the employees had applauded the munificence of their employer who had provided them with the means to play it. I had, unthinkingly, deprived them of it.I held an emergency meeting with our suppliers the following day. I came over big with the notion that it was in their interests to provide a solution. They played it cool, probably knowing that it was my head on the block, not theirs. In the end, they came up with a compromise. they would temporarily descend from their lofty, cerebral stamping grounds  in order to write a server-based Minesweeper and Solitaire game for X Terminals, and install it in a concealed place within the system. We'd have to pay for it, though. I groaned. How could we do that? "Could we call it a 'post-processing module?" suggested their account executive.And so it came to pass. The application was a resounding success. Every now and then, the staff were able to indulge in some 'post-processing', with what turned out to be a very fine implementation of both minesweeper and solitaire. There were several refinements: A single click in a 'boss' button turned the games into what looked just like a financial spreadsheet.  They even threw in a multi-user version of Battleships. The extra payment for the post-processing module went through the change-control process without anyone untoward noticing, and peace once more descended. Only one thing niggles. Those games were good. Do they still survive, somewhere in a Linux library? If so, I'd like to claim a small part in their production.

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  • Understanding the 'High Performance' meaning in Extreme Transaction Processing

    - by kyap
    Despite my previous blogs entries on SOA/BPM and Identity Management, the domain where I'm the most passionated is definitely the Extreme Transaction Processing, commonly called XTP.I came across XTP back to 2007 while I was still FMW Product Manager in EMEA. At that time Oracle acquired a company called Tangosol, which owned an unique product called Coherence that we renamed to Oracle Coherence. Beside this innovative renaming of the product, to be honest, I didn't know much about it, except being a "distributed in-memory cache for Extreme Transaction Processing"... not very helpful still.In general when people doesn't fully understand a technology or a concept, they tend to find some shortcuts, either correct or not, to justify their lack-of understanding... and of course I was part of this category of individuals. And the shortcut was "Oracle Coherence Cache helps to improve Performance". Excellent marketing slogan... but not very meaningful still. By chance I was able to get away quickly from that group in July 2007* at Thames Valley Park (UK), after I attended one of the most interesting workshops, in my 10 years career in Oracle, delivered by Brian Oliver. The biggest mistake I made was to assume that performance improvement with Coherence was related to the response time. Which can be considered as legitimus at that time, because after-all caches help to reduce latency on cached data access, hence reduce the response-time. But like all caches, you need to define caching and expiration policies, thinking about the cache-missed strategy, and most of the time you have to re-write partially your application in order to work with the cache. At a result, the expected benefit vanishes... so, not very useful then?The key mistake I made was my perception or obsession on how performance improvement should be driven, but I strongly believe this is still a common problem to most of the developers. In fact we all know the that the performance of a system is generally presented by the Capacity (or Throughput), with the 2 important dimensions Speed (response-time) and Volume (load) :Capacity (TPS) = Volume (T) / Speed (S)To increase the Capacity, we can either reduce the Speed(in terms of response-time), or to increase the Volume. However we tend to only focus on reducing the Speed dimension, perhaps it is more concrete and tangible to measure, and nicer to present to our management because there's a direct impact onto the end-users experience. On the other hand, we assume the Volume can be addressed by the underlying hardware or software stack, so if we need more capacity (scale out), we just add more hardware or software. Unfortunately, the reality proves that IT is never as ideal as we assume...The challenge with Speed improvement approach is that it is generally difficult and costly to make things already fast... faster. And by adding Coherence will not necessarily help either. Even though we manage to do so, the Capacity can not increase forever because... the Speed can be influenced by the Volume. For all system, we always have a performance illustration as follow: In all traditional system, the increase of Volume (Transaction) will also increase the Speed (Response-Time) as some point. The reason is simple: most of the time the Application logics were not designed to scale. As an example, if you have a while-loop in your application, it is natural to conceive that parsing 200 entries will require double execution-time compared to 100 entries. If you need to "Speed-up" the execution, you can only upgrade your hardware (scale-up) with faster CPU and/or network to reduce network latency. It is technically limited and economically inefficient. And this is exactly where XTP and Coherence kick in. The primary objective of XTP is about designing applications which can scale-out for increasing the Volume, by applying coding techniques to keep the execution-time as constant as possible, independently of the number of runtime data being manipulated. It is actually not just about having an application running as fast as possible, but about having a much more predictable system, with constant response-time and linearly scale, so we can easily increase throughput by adding more hardwares in parallel. It is in general combined with the Low Latency Programming model, where we tried to optimize the network usage as much as possible, either from the programmatic angle (less network-hoops to complete a task), and/or from a hardware angle (faster network equipments). In this picture, Oracle Coherence can be considered as software-level XTP enabler, via the Distributed-Cache because it can guarantee: - Constant Data Objects access time, independently from the number of Objects and the Coherence Cluster size - Data Objects Distribution by Affinity for in-memory data grouping - In-place Data Processing for parallel executionTo summarize, Oracle Coherence is indeed useful to improve your application performance, just not in the way we commonly think. It's not about the Speed itself, but about the overall Capacity with Extreme Load while keeping consistant Speed. In the future I will keep adding new blog entries around this topic, with some sample codes experiences sharing that I capture in the last few years. In the meanwhile if you want to know more how Oracle Coherence, I strongly suggest you to start with checking how our worldwide customers are using Oracle Coherence first, then you can start playing with the product through our tutorial.Have Fun !

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  • Concurrent NFS access

    - by Kristian
    Similar to Concurrent FTP access. How is concurrent file access handled for NFS? Say that one client is updating/overwriting a file on a NFS server, and a process on the server is reading that same file directly from the file system at the same time. Is there some sort of atomic handling of file read/write in NFS/Linux or do I have to work with tmp files to ensure data consistency? I'm worried that the process reading the file will get corrupt data.

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  • Free or very Cheap VPN server software with high concurrent users count

    - by Martin KS
    I'm hoping to implement a VPN whereby about 200 concurrent users can log in to briefly access my network. I had a look at OpenVPN and this seemed excellent, but was hoping that there would be a less costly option on a per-concurrent-user basis. I've no need for particularly strong security, and my only other requirement is that I would need to be able to add users in bulk via csv or similar. Does anyone have any suggestions?

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  • Ubuntu 10.04 - unable to install Arduino

    - by Newbie
    Hello! At the moment, I try to install Arduino on my Ubuntu 10.04 (32 Bit) computer. I downloaded the latest release at http://arduino.cc/en/Main/Software, cd'ed to the directory and unziped the package. When I try to run ./arduino , I get following error: Exception in thread "main" java.lang.ExceptionInInitializerError at processing.app.Base.main(Base.java:112) Caused by: java.awt.HeadlessException at sun.awt.HeadlessToolkit.getMenuShortcutKeyMask(HeadlessToolkit.java:231) at processing.core.PApplet.<clinit>(Unknown Source) ... 1 more Here is my java -version output: java version "1.6.0_20" OpenJDK Runtime Environment (IcedTea6 1.9.5) (6b20-1.9.5-0ubuntu1~10.04.1) OpenJDK Server VM (build 19.0-b09, mixed mode) Any suggestions on this? I try to install arduino without the 'arduino' package. I tried to install it with apt-get (sudo apt-get install arduino). When I try to start arduino (using arduino command) will cause following error: Exception in thread "main" java.lang.ExceptionInInitializerError at processing.app.Preferences.load(Preferences.java:553) at processing.app.Preferences.load(Preferences.java:549) at processing.app.Preferences.init(Preferences.java:142) at processing.app.Base.main(Base.java:188) Caused by: java.awt.HeadlessException at sun.awt.HeadlessToolkit.getMenuShortcutKeyMask(HeadlessToolkit.java:231) at processing.core.PApplet.<clinit>(PApplet.java:224) ... 4 more Update: I saw that I installed several versions of jre (sun and open). So I uninstalled the open jre. Now, when calling arduino I get a new error: java.lang.UnsatisfiedLinkError: no rxtxSerial in java.library.path thrown while loading gnu.io.RXTXCommDriver Exception in thread "main" java.lang.UnsatisfiedLinkError: no rxtxSerial in java.library.path at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1734) at java.lang.Runtime.loadLibrary0(Runtime.java:823) at java.lang.System.loadLibrary(System.java:1028) at gnu.io.CommPortIdentifier.<clinit>(CommPortIdentifier.java:123) at processing.app.Editor.populateSerialMenu(Editor.java:965) at processing.app.Editor.buildToolsMenu(Editor.java:717) at processing.app.Editor.buildMenuBar(Editor.java:502) at processing.app.Editor.<init>(Editor.java:194) at processing.app.Base.handleOpen(Base.java:698) at processing.app.Base.handleOpen(Base.java:663) at processing.app.Base.handleNew(Base.java:578) at processing.app.Base.<init>(Base.java:318) at processing.app.Base.main(Base.java:207)

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  • ADO.NET Data Services business logic processing

    a simple approach that provides business logic processing before forwarding data to the clients with ADO.NET Data Services.  read moreBy Siyamand AyubiDid you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • .NET processing unit [closed]

    - by configurator
    Do you think we'll ever see an IL (or other bytecode) processing unit? It sounds possible and would have a major benefit, because we wouldn't need the JITter. This isn't the same as compiling .NET directly to machine code, since the bytecode here is designed to be programmed and disassembled easily, unlike the bytecode used in x86 processors which is designed to work faster. What's stopping Intel (for example) from partnering with Microsoft and making such a .NET-optimised processor?

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  • Running & Managing Concurrent Queries in SQL Developer

    - by thatjeffsmith
    We’ve all been there – you’ve managed to write a query that takes longer than a few seconds to execute. Tuning aside, sometimes it takes longer than you want for a query to run. So what’s a SQL Developer user to do? I say, keep going! While you’re waiting for your query to finish, there’s no reason why you can’t continue on with your work. If you need to execute something else in a worksheet, there’s no reason to launch a 2nd or 3rd copy of SQL Developer. Just open an un-shared worksheet. Now while you’ve got 1 or more queries running, you can easily get yourself into a situation where you’re not sure what’s running where. Or maybe you want to cancel a query or just check how long something’s been running. Just open the Task Progress Panel If a query or task in SQL Developer takes more than 3-5 seconds, it will appear in the Task Progress panel. You can then watch the throbbers go back and forth while you sip your coffee/soda/Red Bull. Run a query, spawn a new worksheet, run another query, watch them in the Task Progress panel. Kudos and thanks to @leight0nn for helping me get the title of this post right If you’re looking for help in managing and monitoring sessions in general, check out this post.

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  • A better way to do concurrent programming

    - by Alex.Davies
    Programming to take advantage of multicore processors is hard. If you let multiple threads access the same memory, bad things happen. To avoid this, you use the lock keyword, but if you use that in the wrong way, your code deadlocks. It's all a nightmare. Luckily, there's a better way - Actors. They're really easy to think about. They're really safe (if you follow a couple of simple rules). And high-performance, type-safe actors are now available for .NET by using this open-source library: http://code.google.com/p/n-act/ Have a look at the site for details. I'll blog with more reasons to use actors and tips and tricks to get the best parallelism from them soon.

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