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  • Designing Mobile SMS text advertising system

    - by Ramraj Edagutti
    Currently, I am working on a product where we have an SMS text advertising system, and using this, we setup advertising campaigns for clients, and later these campaigns are sent to the end users. This is very similar to Google Adwords, but targeted to Mobile users via SMS. Just to give an overview of the system Each Campaign is mapped to an advertiser Campaign has start date and end date Campaign has a filter condition(s) or query to select the target user base from our database (to whom we send Campaigns) Target user base can be fixed, for e.g send campaign to 10000 users Target user base can also be dynamic based on query condition, for e.g send campaign to users who are active and from a particular state, district, town etc. (this way user base will be keep changing on daily basis) Campaign can have multiple campaign messages Each campaign message has start date and end date Each campaign message can have multiple message texts for different locales, for e.g English,Hindi,Telugu etc After creating an advertisement campaign, we run daily night job to provision the target user base for that a particular campaign in a separate table, and another daily job runs on morning times and checks provisioned table for campaigns and targeted users and sends the campaign to users via SMS. Problem is, current UI for creating advertising campaigns is designed in a very technical manner, I mean, normal user or business owner or clients can not use the UI to create a campaign. Below are reasons why the UI is very technical in nature Filter condition(s) or query input filed, takes user ids or mobile numbers or SQL queries. Most of times or almost every time, we use big SQL queries So we end up storing SQL queries in a database for a campaign, later we use this SQL query to fetch targeted user base. For scheduling these campaigns, we have input filed on UI which takes quartz cron expression(s) ( for e.g. send campaign on "0 0 9 1-10 MAR 2012" ), again very technical in nature Normal user or business owner, can not use the UI for creating campaigns for reasons mentioned above, Currently, we ourself (developers) helping clients to setup/create campaigns. we are trying to re-design the UI to make it more user friendly so that any user can go to UI and create an advertisement campaign by himself. I am thinking of re-designing the current UI similar to Google Adwords interface, especially for selecting target users based on user geography like country, state, city etc. I also need to select users based user subscription(s), which might make system even more complex. And also, for campaign scheduling, I am thinking of using weekdays with hours. For example, I will shows Monday to Sunday on UI, and user can select the from hours, to hours etc. Any better ideas or suggestion on how to design UI in very user friendly manner and what design should be followed on server side code (we write backend code on java/jpa/spring/quartz)? And I am looking for ideas or design patterns on how to build SQL queries (using JPA/Hinernate) programmatically on server side, based on varies conditions like based on country, state, town, village, and user subscriptions.

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  • Monitoring Your Servers

    - by Grant Fritchey
    If you are the DBA in a large scale enterprise, you’re probably already monitoring your servers for up-time and performance. But if you work for a medium-sized business, a small shop, or even a one-man operation, chances are pretty good that you’re not doing that sort of monitoring. You know that you’re supposed to be doing it, but other things, more important at-the-moment things, keep getting in the way. After all, which is more important, some monitoring or backup testing?  Backup testing, of course. Monitoring is frequently one of those things that you do when can get around to it.  Well, as you can see at the right, I have your round tuit ready to go. What if I told you that you could get monitoring on your servers for up-time, job completion, performance, all the standard stuff? And what if I told you that you wouldn’t need to install and configure another server in your environment to get it done? And what if I told you that you’d be able to set up and customize your alerts so you could know if your server was offline or a drive was full? Almost nothing for you to do, and you’ll have a full-blown monitoring process. Sounds to good to be true doesn’t it? Well, it’s coming. We’re creating an online, remote, monitoring system here at Red Gate. You’ll be able to use our SQL Monitor tool (which you can see here, monitoring SQL Server Central in real time) to keep track of your systems, but without having to set up a server and a database for storing the information collected. Instead, we’re taking advantage of services available through the internet to enable collection and storage of this information remotely, off your systems. All you have to do is install a piece of software that will communicate between our service and your servers and you’ll be off and running. It’s that easy. Before you get too excited, let me break the news that this is the near future I’m talking about. We’re setting up the program and there’s a sign-up you can use to get in on the initial tests.

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  • SQL Azure and Trust Services

    - by BuckWoody
    Microsoft is working on a new Windows Azure service called “Trust Services”. Trust Services takes a certificate you upload and uses it to encrypt and decrypt sensitive data in the cloud. Of course, like any security service, there’s a bit more to it than that. I’ll give you a quick overview of how you can use this product to protect data you send to SQL Azure. The primary issue with storing data in the cloud is that you are in an environment that isn’t under your control – in fact, that’s the benefit of being in a distributed computing environment in the first place. On premises you’re able to encrypt data you don’t want anyone else to see, using various methods such as passwords (not very strong) or certificates (stronger). When you use a certificate, it’s vital that you create (or procure) and protect it yourself. When you store data remotely, regardless of IaaS, PaaS or SaaS, you don’t own the machines where the data lives. That means if you use a certificate from the cloud vendor to encrypt the data, you have to trust that the data won’t be accessed by the vendor. In some cases having a signed agreement with the vendor that they won’t access your data is sufficient, in other cases that doesn’t meet the requirements your system has for security. With the new Trust Services service, the basic process is that you use a Portal to create a Trust Server using policies and other controls. You place a X.509 Certificate you create or procure in that server. Using the Software development Kit (SDK), the developer has access to an Application Layer Encryption Framework to set fields of data they want to encrypt. From there, the data can be stored in SQL Azure as a standard field – only it is encrypted before it ever arrives. The portion of the client software that decrypts the data uses the same service, so the authenticated user sees the data if they are allowed to do so. The data remains encrypted “at rest”.  You can learn more about this product and check it out in the SQL Azure labs at Microsoft Codename "Trust Services"

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  • Alternatives for comparing data from different databases

    - by Alex
    I have two huge tables on separate databases. One of them has the information of all the SMS that passed through the company's servers while the other one has the information of the actual billing of those SMS. My job is to compare samples of both of these tables (for example, the records between 1 and 2 pm) to see if there are any differences: SMS that were sent but not charged to the user for whatever reason that may be happening. The columns I will be using to compare are the remitent's phone number and the exact date the SMS was sent. An issue here is that dates usually are the same on both sides, but in many cases differ by 1 or 2 seconds. I have, so far, two alternatives to do this: (PL/SQL) Create two tables where i'm going to temporarily store all the records of that 1hour sample. One for each of the main tables. Then, for each distinct phone number, select the time of every SMS sent from that phone from both my temporary tables and start comparing one by one using cursors. In this case, the procedure would be ran on the server where one of the sources is so the contents of the other one would be looked up using a dblink. (sqlplus + c++) Instead of storing the 1hour samples in new tables, output the query to a text file. I will have two text files, one for each source. Then, open the first file and load all of it's content on a hash_map (key-value) using c++, where the key will be the phone number and the value a list of times of SMS sent from that phone. Finally, open the second file, grab each line (in this format: numberX timeX), look for numberX's entry on the hash_map (wich will be a list of times) and then check if timeX is on that list. If it isn't, save it somewhere to finally store it on a "uncharged" table (this would also be the final step on case 1) My main concern is efficiency. These samples have about 2 million records on each source, so just grabbing one record on one side and looking it up on the other would not be possible. That's the reason I wanted to use hash_maps Which do you think is a better option?

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  • Move Data into the grid for scalable, predictable response times

    - by JuergenKress
    CloudTran is pleased to introduce the availability of the CloudTran Transaction and Persistence Manager for creating scalable, reliable data services on the Oracle Coherence In-Memory Data Grid (IMDG). Use of IMDG architectures has been key to handling today’s web-scale loads because it eliminates database latency by storing important and frequently access data in memory instead of on disk. The CloudTran product lets developers easily use an IMDG for full ACID-compliant transactions without having to be concerned about the location or spread of data. The system has its own implementation of fast, scalable distributed transactions that does NOT depend on XA protocols but still guarantees all ACID properties. Plus, CloudTran asynchronously replicates data going into the IMDG to back-end datastores and back-up data centers, again ensuring ACID properties. CloudTran can be accessed through Java Persistence API (JPA via TopLink Grid) and now, through a new Low-Level API, or LLAPI. This is ideal for use in SOA applications that need data reliability, high availability, performance, and scalability. It is still in its limited beta release, the LLAPI gives developers the ability to use standard put/remove logic available in Coherence and then wrap logic with simple Spring annotations or XML+AspectJ to start transactions. An important feature of LLAPI is the ability to join transactions. This is a common outcome for SOA applications that need to reduce network traffic by aggregating data into single cache entries and then doing SOA service processing in the node holding the data. This results in the need to orchestrate transaction processing across multiple service calls. CloudTran has the capability to handle these “multi-client” transactions at speed with no loss in ACID properties. Developing software around an IMDG like Oracle Coherence is an important choice for today’s web-scale applications and services. But this introduces new architectural considerations to maintain scalability in light of increased network loads and data movement. Without using CloudTran, developers are faced with an incredibly difficult task to ensure data reliability, availability, performance, and scalability when working with an IMDG. Working with highly distributed data that is entirely volatile while stored in memory presents numerous edge cases where failures can result in data loss. The CloudTran product takes care of all of this, leaving developers with the confidence and peace of mind that all data is processed correctly. For those interested in evaluating the CloudTran product and IMDGs, take a look at this link for more information: http://www.CloudTran.com/downloadAPI.ph , or send your questions to [email protected]. 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: CloudTran,data grid,M,SOA Community,Oracle SOA,Oracle BPM,BPM,Community,OPN,Jürgen Kress

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  • SOA Community Newsletter September 2012

    - by JuergenKress
    Dear SOA partner community member Are you ready for Oracle Open World 2012? If you are planning to attend, make sure that you prepare your trip to San Francisco. If you could not make it, watch the keynotes live on-demand. You can also plan and decide to visit the SOA, Cloud and Service Technology Symposium 2012 and meet Tim Hall and Demed Lher from our product management team in London. As an Oracle partner you will get 50% discount on the conference pass, please use the code DJMXZ370 and avail your discount. The BPM Solution Catalogue is now live, make sure you use the process examples and contribute your processes. SOA Proactive support is the best resource to support your SOA implementations. To administrate your SOA systems Enterprise Manager Cloud Control 12c is the best tool, you can now attend thefree on-demand training. EM12c, Real User Experience Insight 12R1 gives you all the details, checkout our new demo. The BPM11g demo for Oracle E-Business Suite has become available. A wonderful SOA demo case is the Fusion Order Demo, Antony Reynolds posted an article how to update it on SOA Suite PS5. If you do use Coherence e.g. for SOA Suite, checkout the extension from our partner CloudTran. In this edition to this you will also find articles from: Automatically Disable Proxy Service to avoid overloading OSB By Jian Liang & Storing SCA Metadata in the Oracle Metadata Services Repository by Nicolás Fonnegra Martinez and Markus Lohn & Exploring MDS Explorer by Mark Nelson & Using Cloud OER to Find Fusion Applications On-Premise Service Concrete WSDL URL by Rajesh Raheja & Oracle Service Bus duplicate message check using Coherence by Jan van Zoggel & Installing Oracle SOA Suite10g on Oracle Enterprise Linux Lonneke Dikmans & Generating an EJB SDO Service Interface for Oracle SOA Suite by Edwin Biemond. Jürgen Kress Oracle SOA & BPM Partner Adoption EMEA To read the newsletter please visit http://tinyurl.com/soanewsSeptember2012 (OPN Account required) To become a member of the SOA Partner Community please register at http://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 newsletter,SOA Community,Oracle SOA,Oracle BPM,BPM Community,OPN,Jürgen Kress

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  • Drawing multiple objects from one Vertex Buffer Object in OpenGL/OpenTK

    - by stoney78us
    I am trying to experimenting drawing method using VBO in OpenGL. Many people normally use 1 vbo to store one object data array. I was trying to do something quite opposite which is storing multiple object data into 1 vbo then drawing it. There is story behind why i want to do this. I want to group many of objects as a single object sometime. However my code doesn't do the justice. Following is my pseudo code: //Data double[] vertices = {line strip 1, line strip 2, line strip 3}; //series of vertices int linestrip1offset = index of the first vertex in line strip 1; int linestrip2offset = index of the first vertex in line strip 2; int linestrip3offset = index of the first vertex in line strip 3; int linestrip1VertexNum = number of vertices in linestrip 1; int linestrip2VertexNum = number of vertices in linestrip 2; int linestrip3VertexNum = number of vertices in linestrip 3; //Setting Up void init() { int[] vBO = new int[1]; GL.GenBuffer(1, vBO); GL.BindBuffer(BufferTarget.ArrayBuffer, vBO[0]); GL.BufferData(BufferTarget.ArrayBuffer, new IntPtr(_vertices.Length * sizeof(double)), _vertices, BufferUsageHint.StaticDraw); GL.EnableClientState(Array.VertexArray); } //Drawing void draw() { GL.BindBuffer(BufferTarget.ArrayBuffer, vBO[0]); GL.EnableClientState(ArrayCap.VertexArray); GL.VertexPointer(3, VertexPointerType.Double, 0, linestrip1offset); //drawing first linestrip GL.DrawArrays(drawMode, linestrip1offset , linestrip1VertexNum ); GL.VertexPointer(3, VertexPointerType.Double, 0, linestrip2offset); //drawing second linestrip GL.DrawArrays(drawMode, linestrip2offset , linestrip2VertexNum ); GL.VertexPointer(3, VertexPointerType.Double, 0, linestrip3offset); //drawing third linestrip GL.DrawArrays(drawMode, linestrip3offset , linestrip3VertexNum ); GL.DisableClientState(ArrayCap.VertexArray); GL.BindBuffer(BufferTarget.ArrayBuffer, 0); } I don't know what i did wrong but i think technically it should work where we can tell OpenGL which part of the data in the vBO to be drawn.

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  • Efficient inline templates and C++

    - by Darryl Gove
    I've talked before about calling inline templates from C++, I've also talked about calling inline templates efficiently. This time I want to talk about efficiently calling inline templates from C++. The obvious starting point is that I need to declare the inline templates as being extern "C": extern "C" { int mytemplate(int); } This enables us to call it, but the call may not be very efficient because the compiler will treat it as a function call, and may produce suboptimal code based on that premise. So we need to add the no_side_effect pragma: extern "C" { int mytemplate(int); #pragma no_side_effect(mytemplate) } However, this may still not produce optimal code. We've discussed how the no_side_effect pragma cannot be combined with exceptions, well we know that the code cannot produce exceptions, but the compiler doesn't know that. If we tell the compiler that information it may be able to produce even better code. We can do this by adding the "throw()" keyword to the template declaration: extern "C" { int mytemplate(int) throw(); #pragma no_side_effect(mytemplate) } The following is an example of how these changes might improve performance. We can take our previous example code and migrate it to C++, adding the use of a try...catch construct: #include <iostream extern "C" { int lzd(int); #pragma no_side_effect(lzd) } int a; int c=0; class myclass { int routine(); }; int myclass::routine() { try { for(a=0; a<1000; a++) { c=lzd(c); } } catch(...) { std::cout << "Something happened" << std::endl; } return 0; } Compiling this produces a slightly suboptimal code sequence in the hot loop: $ CC -O -xtarget=T4 -S t.cpp t.il ... /* 0x0014 23 */ lzd %o0,%o0 /* 0x0018 21 */ add %l6,1,%l6 /* 0x001c */ cmp %l6,1000 /* 0x0020 */ bl,pt %icc,.L77000033 /* 0x0024 23 */ st %o0,[%l7] There's a store in the delay slot of the branch, so we're repeatedly storing data back to memory. If we change the function declaration to include "throw()", we get better code: $ CC -O -xtarget=T4 -S t.cpp t.il ... /* 0x0014 21 */ add %i1,1,%i1 /* 0x0018 23 */ lzd %o0,%o0 /* 0x001c 21 */ cmp %i1,999 /* 0x0020 */ ble,pt %icc,.L77000019 /* 0x0024 */ nop The store has gone, but the code is still suboptimal - there's a nop in the delay slot rather than useful work. However, it's good enough for this example. The point I'm making is that the compiler produces the better code with both the "throw()" and the no side effect pragma.

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  • OpenGL position from depth is wrong

    - by CoffeeandCode
    My engine is currently implemented using a deferred rendering technique, and today I decided to change it up a bit. First I was storing 5 textures as so: DEPTH24_STENCIL8 - Depth and stencil RGBA32F - Position RGBA10_A2 - Normals RGBA8 x 2 - Specular & Diffuse I decided to minimize it and reconstruct positions from the depth buffer. Trying to figure out what is wrong with my method currently has not been fun :/ Currently I get this: which changes whenever I move the camera... weird Vertex shader really simple #version 150 layout(location = 0) in vec3 position; layout(location = 1) in vec2 uv; out vec2 uv_f; void main(){ uv_f = uv; gl_Position = vec4(position, 1.0); } Fragment shader Where the fun (and not so fun) stuff happens #version 150 uniform sampler2D depth_tex; uniform sampler2D normal_tex; uniform sampler2D diffuse_tex; uniform sampler2D specular_tex; uniform mat4 inv_proj_mat; uniform vec2 nearz_farz; in vec2 uv_f; ... other uniforms and such ... layout(location = 3) out vec4 PostProcess; vec3 reconstruct_pos(){ float z = texture(depth_tex, uv_f).x; vec4 sPos = vec4(uv_f * 2.0 - 1.0, z, 1.0); sPos = inv_proj_mat * sPos; return (sPos.xyz / sPos.w); } void main(){ vec3 pos = reconstruct_pos(); vec3 normal = texture(normal_tex, uv_f).rgb; vec3 diffuse = texture(diffuse_tex, uv_f).rgb; vec4 specular = texture(specular_tex, uv_f); ... do lighting ... PostProcess = vec4(pos, 1.0); // Just for testing } Rendering code probably nothing wrong here, seeing as though it always worked before this->gbuffer->bind(); gl::Clear(gl::COLOR_BUFFER_BIT | gl::DEPTH_BUFFER_BIT); gl::Enable(gl::DEPTH_TEST); gl::Enable(gl::CULL_FACE); ... bind geometry shader and draw models and shiz ... gl::Disable(gl::DEPTH_TEST); gl::Disable(gl::CULL_FACE); gl::Enable(gl::BLEND); ... bind textures and lighting shaders shown above then draw each light ... gl::BindFramebuffer(gl::FRAMEBUFFER, 0); gl::Clear(gl::COLOR_BUFFER_BIT | gl::DEPTH_BUFFER_BIT); gl::Disable(gl::BLEND); ... bind screen shaders and draw quad with PostProcess texture ... Rinse_and_repeat(); // not actually a function ;) Why are my positions being output like they are?

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  • Pragmas and exceptions

    - by Darryl Gove
    The compiler pragmas: #pragma no_side_effect(routinename) #pragma does_not_write_global_data(routinename) #pragma does_not_read_global_data(routinename) are used to tell the compiler more about the routine being called, and enable it to do a better job of optimising around the routine. If a routine does not read global data, then global data does not need to be stored to memory before the call to the routine. If the routine does not write global data, then global data does not need to be reloaded after the call. The no side effect directive indicates that the routine does no I/O, does not read or write global data, and the result only depends on the input. However, these pragmas should not be used on routines that throw exceptions. The following example indicates the problem: #include <iostream extern "C" { int exceptional(int); #pragma no_side_effect(exceptional) } int exceptional(int a) { if (a==7) { throw 7; } else { return a+1; } } int a; int c=0; class myclass { public: int routine(); }; int myclass::routine() { for(a=0; a<1000; a++) { c=exceptional(c); } return 0; } int main() { myclass f; try { f.routine(); } catch(...) { std::cout << "Something happened" << a << c << std::endl; } } The routine "exceptional" is declared as having no side effects, however it can throw an exception. The no side effects directive enables the compiler to avoid storing global data back to memory, and retrieving it after the function call, so the loop containing the call to exceptional is quite tight: $ CC -O -S test.cpp ... .L77000061: /* 0x0014 38 */ call exceptional ! params = %o0 ! Result = %o0 /* 0x0018 36 */ add %i1,1,%i1 /* 0x001c */ cmp %i1,999 /* 0x0020 */ ble,pt %icc,.L77000061 /* 0x0024 */ nop However, when the program is run the result is incorrect: $ CC -O t.cpp $ ./a.out Something happend00 If the code had worked correctly, the output would have been "Something happened77" - the exception occurs on the seventh iteration. Yet, the current code produces a message that uses the original values for the variables 'a' and 'c'. The problem is that the exception handler reads global data, and due to the no side effects directive the compiler has not updated the global data before the function call. So these pragmas should not be used on routines that have the potential to throw exceptions.

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  • Grub rescue - error: unknown filesystem

    - by user53817
    I have a multiboot system set up. The system has three drives. Multiboot is configured with Windows XP, Windows 7, and Ubuntu - all on the first drive. I had a lot of unpartitioned space left on the drive and was reserving it for adding other OSes and for storing files there in the future. One day I went ahead and downloaded Partition Wizard and created a logical NTFS partition from within Windows 7, still some unpartitioned space left over. Everything worked fine, until I rebooted the computer a few days later. Now I'm getting: error: unknown filesystem. grub rescue First of all I was surprised not to find any kind of help command, by trying: help, ?, man, --help, -h, bash, cmd, etc. Now I'm stuck with non-bootable system. I have started researching the issue and finding that people usually recommend to boot to a Live CD and fix the issue from there. Is there a way to fix this issue from within grub rescue without the need for Live CD? UPDATE By following the steps from persist commands typed to grub rescue, I was able to boot to initramfs prompt. But not anywhere further than that. So far from reading the manual on grub rescue, I was able to see my drives and partitions using ls command. For the first hard drive I see the following: (hd0) (hd0,msdos6) (hd0,msdos5) (hd0,msdos2) (hd0,msdos1) I now know that (hd0,msdos6) contains Linux on it, since ls (hd0,msdos6)/ lists directories. Others will give "error: unknown filesystem." UPDATE 2 After the following commands I am now getting to the boot menu and can boot into Windows 7 and Ubuntu, but upon reboot I have to repeat these steps. ls ls (hd0,msdos6)/ set root=(hd0,msdos6) ls / set prefix=(hd0,msdos6)/boot/grub insmod /boot/grub/linux.mod normal UPDATE 3 Thanks Shashank Singh, with your instructions I have simplified my steps to the following. I have learned from you that I can replace msdos6 with just a 6 and that I can just do insmod normal instead of insmod /boot/grub/linux.mod. Now I just need to figure out how to save this settings from within grub itself, without booting into any OS. set root=(hd0,6) set prefix=(hd0,6)/boot/grub insmod normal normal UPDATE 4 Well, it seems like it is a requirement to boot into Linux. After booting into Ubuntu I have performed the following steps described in the manual: sudo update-grub udo grub-install /dev/sda This did not resolve the issue. I still get the grub rescue prompt. What do I need to do to permanently fix it? I have also learned that drive numbers as in hd0 need to be translated to drive letters as in /dev/sda for some commands. hd1 would be sdb, hd2 would be sdc, and so on. Partitions listed in grub as (hd0,msdos6) would be translated to /dev/sda6.

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  • Is MongoDB a good choice or not for my application?

    - by shubham
    I have a Reporting application which stores the reports in xml format as recieved from source (XML schema is not defined, it can be any format) and those reports contain some keys and values. Like jobid, setid be keys for 1 type of report and userid, groupId for another type of report etc. The type of keys that can be referred from the document is determined by the namespaces used in the xml doc. These keys are stored on the basis of namespace used in the xml document. For e.g. If a tag in xml fragment uses namespace= "myspace1", then I have keys A and B for myspace1 stored in another table. It will fetch those keys from that table for this namespace, look for their values in xml doc and store it in another table along with the pointer to this xml document (Id of a record storing complete xml document in a cell). Use cases: When the user comes and queries for that key and value, I return the document or a set of documents that are having those key/value pairs. When the user comes and queries for a certain key and provide a name for xslt (pre stored), I fetch the set of documents fulfilling that criteria and convert that xml to html with the specified xslt. When the user comes and asks for a particular fragment of a doc then it can fetch a subset from a particular document also. When the user comes and queries for top x values of a certain key, I return the set of documents that are having top 10 values of that key. I am using DB2 database for its support of xml along with relational capabilities. That makes easier for me to run xpath expressions and fetch values of keys and also aggregate a set of documents fullfilling a criteria, all on the database side. Problems: DB2 stores XML doc of upto 2GB in size. Retrieval is very slow. If some thing involves many documents, then it takes significant time for things to show up in browser, and the user has to wait. Can MongoDb help in this case, as it is document oriented? can I do xml related xpath queries and document transformations on db side? Or is it ok to use both in such a case?

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  • What algorithms can I use to detect if articles or posts are duplicates?

    - by michael
    I'm trying to detect if an article or forum post is a duplicate entry within the database. I've given this some thought, coming to the conclusion that someone who duplicate content will do so using one of the three (in descending difficult to detect): simple copy paste the whole text copy and paste parts of text merging it with their own copy an article from an external site and masquerade as their own Prepping Text For Analysis Basically any anomalies; the goal is to make the text as "pure" as possible. For more accurate results, the text is "standardized" by: Stripping duplicate white spaces and trimming leading and trailing. Newlines are standardized to \n. HTML tags are removed. Using a RegEx called Daring Fireball URLs are stripped. I use BB code in my application so that goes to. (ä)ccented and foreign (besides Enlgish) are converted to their non foreign form. I store information about each article in (1) statistics table and in (2) keywords table. (1) Statistics Table The following statistics are stored about the textual content (much like this post) text length letter count word count sentence count average words per sentence automated readability index gunning fog score For European languages Coleman-Liau and Automated Readability Index should be used as they do not use syllable counting, so should produce a reasonably accurate score. (2) Keywords Table The keywords are generated by excluding a huge list of stop words (common words), e.g., 'the', 'a', 'of', 'to', etc, etc. Sample Data text_length, 3963 letter_count, 3052 word_count, 684 sentence_count, 33 word_per_sentence, 21 gunning_fog, 11.5 auto_read_index, 9.9 keyword 1, killed keyword 2, officers keyword 3, police It should be noted that once an article gets updated all of the above statistics are regenerated and could be completely different values. How could I use the above information to detect if an article that's being published for the first time, is already existing within the database? I'm aware anything I'll design will not be perfect, the biggest risk being (1) Content that is not a duplicate will be flagged as duplicate (2) The system allows the duplicate content through. So the algorithm should generate a risk assessment number from 0 being no duplicate risk 5 being possible duplicate and 10 being duplicate. Anything above 5 then there's a good possibility that the content is duplicate. In this case the content could be flagged and linked to the article's that are possible duplicates and a human could decide whether to delete or allow. As I said before I'm storing keywords for the whole article, however I wonder if I could do the same on paragraph basis; this would also mean further separating my data in the DB but it would also make it easier for detecting (2) in my initial post. I'm thinking weighted average between the statistics, but in what order and what would be the consequences...

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  • Client-Server connection response timeout issues

    - by Srikar
    User creates a folder in client and in the client-side code I hit an API to the server to make this persistent for that user. But in some cases, my server is so busy that the request timesout. The server has executed my request but timedout before sending a response back to client. The timeout set is 10 seconds in client. At this point the client thinks that server has not executed its request (of creating a folder) and ends up sending it again. Now I have 2 folders on the server but the user has created only 1 folder in the client. How to prevent this? One of the ways to solve this is to use a unique ID with each new request. So the ID acts as a distinguisher between old and new requests from client. But this leads to storing these IDs on my server and do a lookup for each API call which I want to avoid. Other way is to increase the timeout duration. But I dont want to change this from 10 seconds. Something tells me that there are better solutions. I have posted this question in stackoverflow but I think its better suited here. UPDATE: I will make my problem even more explicit. The client is a webbrowser and the server is running nginx+django+mysql (standard stack). The user creates a folder in webbrowser. As a result I need to hit a server API. The API call responds back, thereby client knows API call was success. This is normal scenario. Sometimes though, server successfully completes the API request but the client-side (webbrowser) connection timesout before server can respond back. The client has no clue at this point. The user thinks the request was a fail & clicks again. This time it was a success but when the UI refreshes he sees 2 folders. I want to remedy this situation.

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  • Behaviour Trees with irregular updates

    - by Robominister
    I'm interested in behaviour trees that aren't iterated every game tick, but every so often. (Edit: the tree could specify how many frames within the main game loop to wait before running its tick function again). Every theoretical implementation I have seen of behaviour trees talks of the tree search being carried out every game update - which seems necessary, because a leaf node (eg a behaviour, like 'return to base') needs to be constantly checked to see if is still running, failed or completed. Can anyone suggest how I might start implementing a tree that isnt run every tick, or point me in the direction of good material specific to this case (I am struggling to find anything)? My thoughts so far: action leaf nodes (when they start) must only push some kind of action object onto a list for an entity, rather than directly calling any code that makes the entity do something. The list of actions for the entity would be run every frame (update any that need to run, pop any that have completed from the list). the return state from a given action must be fed back into the tree, so that when we run the tree iteration again (and reach the same action leaf node - so the tree has so far determined that we ought to still be trying this action) - that the action has completed, or is still running etc. If my actual action code is running from an action list on an entity, then I possibly need to cancel previously running actions in the list - i am thinking that I can just delete the entire stack of queued up actions. I've seen the idea of ActionLists which block lower priority actions when a higher priority one is added, but this seems like very close logic to behaviour trees, and I dont want to be duplicating behaviour. This leaves me with some questions 1) How would I feed the action return state back into the tree? Its obvious I need to store some information relating to 'currently executing actions' on the entity, and check that in the tree tick, but I can't imagine how. 2) Does having a seperate behaviour tree (for deciding behaviour) and action list (for carrying out actual queued up actions) sound like a reasonable approach? 3) Is the approach of updating a behaviour tree irregularly actually used by anyone? It seems like a nice idea for budgeting ai search time when you have a lot of ai entities to process. (Edit) - I am also thinking about storing a single instance of a given behaviour tree in memory, and providing it by reference to any entity that uses it. So any information about what action was last selected for execution on an entity must be stored in a data context relative to the entity (which the tree can check). (I am probably answering my own questions as i go!) I hope I have expressed my questions adequately! Thanks in advance for any help :)

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  • Are there any concerns with using a static read-only unit of work so that it behaves like a cache?

    - by Rowan Freeman
    Related question: How do I cache data that rarely changes? I'm making an ASP.NET MVC4 application. On every request the security details about the user will need to be checked with the area/controller/action that they are accessing to see if they are allowed to view it. The security information is stored in the database. For example: User Permission UserPermission Action ActionPermission A "Permission" is a token that is applied to an MVC action to indicate that the token is required in order to access the action. Once a user is given the permission (via the UserPermission table) then they have the token and can therefore access the action. I've been looking in to how to cache this data (since it rarely changes) so that I'm only querying in-memory data and not hitting a database (which is a considerable performance hit at the moment). I've tried storing things in lists, using a caching provider but I either run in to problems or performance doesn't improve. One problem that I constantly run in to is that I'm using lazy loading and dynamic proxies with EntityFramework. This means that even if I ToList() everything and store them somewhere static, the relationships are never populated. For example, User.Permissions is an ICollection but it's always null. I don't want to Include() everything because I'm trying to keep things simple and generic (and easy to modify). One thing I know is that an EntityFramework DbContext is a unit of work that acts with 1st-level caching. That is, for the duration of the unit of work, everything that is accessed is cached in memory. I want to create a read-only DbContext that will exist indefinitely and will only be used to read about permission data. Upon testing this it worked perfectly; my page load times went from 200ms+ to 20ms. I can easily force the data to refresh at certain intervals or simply leave it to refresh when the application pool is recycled. Basically it will behave like a cache. Note that the rest of the application will interact with other contexts that exist per request as normal. Is there any disadvantage to this approach? Could I be doing something different?

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  • As the current draft stands, what is the most significant change the "National Strategy for Trusted Identities in Cyberspace" will provoke?

    - by mfg
    A current draft of the "National Strategy for Trusted Identities in Cyberspace" has been posted by the Department of Homeland Security. This question is not asking about privacy or constitutionality, but about how this act will impact developers' business models and development strategies. When the post was made I was reminded of Jeff's November blog post regarding an internet driver's license. Whether that is a perfect model or not, both approaches are attempting to handle a shared problem (of both developers and end users): How do we establish an online identity? The question I ask here is, with respect to the various burdens that would be imposed on developers and users, what are some of the major, foreseeable implementation issues that will arise from the current U.S. Government's proposed solution? For a quick primer on the setup, jump to page 12 for infrastructure components, here are two stand-outs: An Identity Provider (IDP) is responsible for the processes associated with enrolling a subject, and establishing and maintaining the digital identity associated with an individual or NPE. These processes include identity vetting and proofing, as well as revocation, suspension, and recovery of the digital identity. The IDP is responsible for issuing a credential, the information object or device used during a transaction to provide evidence of the subject’s identity; it may also provide linkage to authority, roles, rights, privileges, and other attributes. The credential can be stored on an identity medium, which is a device or object (physical or virtual) used for storing one or more credentials, claims, or attributes related to a subject. Identity media are widely available in many formats, such as smart cards, security chips embedded in PCs, cell phones, software based certificates, and USB devices. Selection of the appropriate credential is implementation specific and dependent on the risk tolerance of the participating entities. Here are the first considered actionable components of the draft: Action 1: Designate a Federal Agency to Lead the Public/Private Sector Efforts Associated with Achieving the Goals of the Strategy Action 2: Develop a Shared, Comprehensive Public/Private Sector Implementation Plan Action 3:Accelerate the Expansion of Federal Services, Pilots, and Policies that Align with the Identity Ecosystem Action 4:Work Among the Public/Private Sectors to Implement Enhanced Privacy Protections Action 5:Coordinate the Development and Refinement of Risk Models and Interoperability Standards Action 6: Address the Liability Concerns of Service Providers and Individuals Action 7: Perform Outreach and Awareness Across all Stakeholders Action 8: Continue Collaborating in International Efforts Action 9: Identify Other Means to Drive Adoption of the Identity Ecosystem across the Nation

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  • Validate if aTextBox Value Start with a Specific Letter

    - by Vincent Maverick Durano
    In case you will be working on a page that needs to validate the first character of the TextBox entered by a user then here are two options that you can use: Option 1: Using an array   1: <asp:Content ID="Content1" ContentPlaceHolderID="HeadContent" runat="server"> 2: <script type="text/javascript"> 3: function CheckFirstChar(o) { 4: var arr = ['A', 'B', 'C', 'D']; 5: if (o.value.length > 0) { 6: for (var i = 0; i < arr.length; i++) { 7: if (o.value.charAt(0) == arr[i]) { 8: alert('Valid'); 9: return true; 10: } 11: else { 12: alert('InValid'); 13: return false; 14: } 15: } 16: } 17: } 18: </script> 19: </asp:Content> 20: <asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server"> 21: <asp:TextBox ID="TextBox1" runat="server" onblur="return CheckFirstChar(this);"></asp:TextBox> 22: </asp:Content>   The example above uses an array of string for storing the list of  characters that a TextBox value should start with. We then iterate to the array and compare the first character of TextBox value to see if it matches any characters from the array. Option 2: Using Regular Expression (Preferred way)   1: <asp:Content ID="Content1" ContentPlaceHolderID="HeadContent" runat="server"> 2: <script type="text/javascript"> 3: function CheckFirstChar(o) { 4: pattern = /^(A|B|C|D)/; 5: if (!pattern.test(o.value)) { 6: alert('InValid'); 7: return false; 8: } else { 9: alert('Valid'); 10: return true; 11: } 12: } 13: </script> 14: </asp:Content> 15: <asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server"> 16: <asp:TextBox ID="TextBox1" runat="server" onblur="return CheckFirstChar(this);"></asp:TextBox> 17: </asp:Content>   The example above uses regular expression with the pattern  /^(A|B|C|D)/. This will check if the TextBox value starts with A,B,C or D. Please note that it's case sensitive. If you want to allow lower case then you can alter the patter to this /^(A|B|C|D)/i. The i in the last part will cause a case-insensitive search.   That's it! I hope someone find this post useful!

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  • Move Data into the Grid for Scalable, Predictable Response Times

    - by JuergenKress
    CloudTran is pleased to introduce the availability of the CloudTran Transaction and Persistence Manager for creating scalable, reliable data services on the Oracle Coherence In-Memory Data Grid (IMDG). Use of IMDG architectures has been key to handling today’s web-scale loads because it eliminates database latency by storing important and frequently access data in memory instead of on disk. The CloudTran product lets developers easily use an IMDG for full ACID-compliant transactions without having to be concerned about the location or spread of data. The system has its own implementation of fast, scalable distributed transactions that does NOT depend on XA protocols but still guarantees all ACID properties. Plus, CloudTran asynchronously replicates data going into the IMDG to back-end datastores and back-up data centers, again ensuring ACID properties. CloudTran can be accessed through Java Persistence API (JPA via TopLink Grid) and now, through a new Low-Level API, or LLAPI. This is ideal for use in SOA applications that need data reliability, high availability, performance, and scalability. Still in limited beta release, the LLAPI gives developers the ability to use standard put/remove logic available in Coherence and then wrap logic with simple Spring annotations or XML+AspectJ to start transactions. An important feature of LLAPI is the ability to join transactions. This is a common outcome for SOA applications that need to reduce network traffic by aggregating data into single cache entries and then doing SOA service processing in the node holding the data. This results in the need to orchestrate transaction processing across multiple service calls. CloudTran has the capability to handle these “multi-client” transactions at speed with no loss in ACID properties. Developing software around an IMDG like Oracle Coherence is an important choice for today’s web-scale applications and services. But this introduces new architectural considerations to maintain scalability in light of increased network loads and data movement. Without using CloudTran, developers are faced with an incredibly difficult task to ensure data reliability, availability, performance, and scalability when working with an IMDG. Working with highly distributed data that is entirely volatile while stored in memory presents numerous edge cases where failures can result in data loss. The CloudTran product takes care of all of this, leaving developers with the confidence and peace of mind that all data is processed correctly. For those interested in evaluating the CloudTran product and IMDGs, take a look at this link for more information: http://www.CloudTran.com/downloadAPI.php, or, send your questions to [email protected]. WebLogic Partner Community For regular information become a member in the WebLogic Partner Community please visit: http://www.oracle.com/partners/goto/wls-emea ( OPN account required). If you need support with your account please contact the Oracle Partner Business Center. BlogTwitterLinkedInMixForumWiki Technorati Tags: Coherence,cloudtran,cache,WebLogic Community,Oracle,OPN,Jürgen Kress

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  • Analysing SQLBits Feedback

    - by jamiet
    Earlier this week I received all the feedback that people offered on my session at SQLBits 7 in York – “SSIS Dataflow Performance Tuning” (the video is available online if you wish to see it). As you may have gathered from previous posts on this blog and my less-SQLy-focused Wordpress blog I am a big fan of collecting and tracking both personal and public data and session feedback lends itself very well to tracking because it is quantitative rather than qualitative; by that I mean attendees are invited to provide marks out of ten rather than (or, in the case of SQLBits, as well as) written comments. The SQLBits feedback is also useful because they use a consistent format – the same questions are asked each time – this means it is particularly easy to to track whether the scores that people give are trending up or down. I suspect that somewhere the SQLBits organisers have a big Analysis Services cube (ok, perhaps its an Excel pivot table) that allows them to analyse these scores per conference, speaker, track etc.… and there’s no reason that we as session speakers cannot do the same thing. To that end I have started to store my feedback in an Excel spreadsheet of my own which in the interests of transparency is available for public viewing (only a web browser required) on SkyDrive at http://cid-550f681dad532637.office.live.com/view.aspx/Public/Misc/Personal%20SQLBits%20Session%20Feedback.xlsx. I have used a pivot table to aggregate all that feedback and here is a screenshot: I am hereby making a public plea to the SQLBits organisers (on the off-chance that they are reading) to please continue to keep the feedback format consistent in the future and I encourage them to publish all of the feedback in an anonymised form. I would also encourage anyone doing conference speaking to track their conference feedback in the same way that I am doing so that you get an insight into whether or not you are improving over time. It is not difficult to setup and maintaining it as you do more sessions takes very little effort. Storing feedback data like this leads me to wider thoughts about well-known conventions and data format standardisation. Let’s imagine a utopia where there were a standard set of questions for capturing session feedback that were leveraged at every conference regardless of subject matter, location or culture; that would give rise to immense cross-conference and cross-discipline analysis – the data analyst in me goes giddy at the thought of it. It is scenarios like this that drive my interest both in data formats such as iCalendar, microformats and RDF, and in emerging movements such as the semantic web and linked data, all things which I have written about in the past. I don’t know whether we will ever reach the stage where every piece of data has structured, descriptive metadata associated with it but I live in hope. @Jamiet

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  • PASS Summit for SQL Starters

    - by Davide Mauri
    I’ve received a buch of emails from PASS Summit “First Timers” that are also somehow new to SQL Server (for “somehow” I mean people with less than 6 month experience but with some basic knowledge of SQL Server engine) or are catching up from SQL Server 2000. The common question regards the session one should not miss to have a broad view of the entire SQL Server platform have some insight into some specific areas of SQL Server Given that I’m on (semi-)vacantion and that I have more free time (not true, I have to prepare slides & demos for several conferences, PASS Summit  - Building the Agile Data Warehouse with SQL Server 2012 - and PASS 24H - Agile Data Warehousing with SQL Server 2012 - among them…but let’s pretend it to be true), I’ve decided to make a post to answer to this common questions. Of course this is my personal point of view and given the fact that the number and quality of session that will be delivered at PASS Summit is so high that is very difficoult to make a choice, fell free to jump into the discussion and leave your feedback or – even better – answer with another post. I’m sure it will be very helpful to all the SQL Server beginners out there. I’ve imposed to myself to choose 6 session at maximum for each Track. Why 6? Because it’s the maximum number of session you can follow in one day, and given that all the session will be on the Summit DVD, they are the answer to the following question: “If I have one day to spend in training, which session I should watch?”. Of course a Summit is not like a Course so a lot of very basics concept of well-established technologies won’t be found here. Analysis Services, Integration Services, MDX are not part of the Summit this time (at least for the basic part of them). Enough with that, let’s start with the session list ideal to have a good Overview of all the SQL Server Platform: Geospatial Data Types in SQL Server 2012 Inside Unstructured Data: SQL Server 2012 FileTable and Semantic Search XQuery and XML in SQL Server: Common Problems and Best Practice Solutions Microsoft's Big Play for Big Data Dashboards: When to Choose Which MSBI Tool Microsoft BI End-User Tools 360° for what concern Database Development, I recommend the following sessions Understanding Transaction Isolation Levels What to Look for in Execution Plans Improve Query Performance by Fixing Bad Parameter Sniffing A Window into Your Data: Using SQL Window Functions Practical Uses and Optimization of New T-SQL Features in SQL Server 2012 Taking MERGE Beyond the Basics For Business Intelligence Information Delivery Analyzing SSAS Data with Excel Building Compelling Power View Reports Managed Self-Service BI PowerPivot 101  SharePoint for Business Intelligence The Best Microsoft BI Tools You've Never Heard Of and for Business Intelligence Architecture & Development BI Power Hour Building a Tabular Model Database Enterprise Information Management: Bringing Together SSIS, DQS, and MDS SSIS Design Patterns Storing Columnstore Indexes Hadoop and Its Ecosystem Components in Action Beside the listed sessions, First Timers should also take a look the the page PASS set up for them: http://www.sqlpass.org/summit/2012/Connect/FirstTimers.aspx See you at PASS Summit!

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  • Ubuntu 13.XX unable to mount USB HDD. Tried everything. I/O error boot sector/file system

    - by XaviGG
    I know that there are many posts related but none of them helped me. I will jump to the last test because it is the one that should work, but it does not. An external HDD with single partition slow NTFS formatted in Windows, empty and clean. Checked for errors, it tells that not errors where found. Moving to Ubutnu 13.04... Gparted throws the first error when trying to read the disk: Input/output error It appears as unknown the content of the disk. Unable to create partition table or format it, getting the same error when trying. If I try to mount it in the terminal it tells me the same, specifying that also there is an I/O error reading the boot sector. I have this problem since I upgraded (always with fresh install) to 13.04. I thought it will be solved by the 13.10 but it has the same behavior. I tried with two different HDD (HD and SSHD) that work perfectly in Windows 7. In 13.04 at least I got a trying of mounting where the icon of the drive started showing and disappearing until finally it disappeared. But now it doesn't even try. Possible causes: -The HDD was my old main HDD, so it had WIN,RECOVERY,SYSTEM,UBU,SWAP partitions. Maybe the way or place where the partition table is defined is not the best for an external HDD but I don't know a lot in that topic. I would appreciate a lot if someone can give me a guideline to convert one of these HDD in a working external HDD. No files to recover, nothing to care about. Just format completely the disk and be able to use it for storing backups without having to move the files first to the windows partition, load windows and then copy them to the external HDD. Because I want to use a file comparator for the backups. Thanks a lot Edit 1: I found an option in Windows to convert it to a dynamic HDD that warns me that I wont be able to run O.S. after changing. I suppose that is what I need because in the current mode I cannot safely extract it. But it tells me an error that it couldn't change the mode.

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  • SharePoint 2010 HierarchicalConfig Caching Problem

    - by Damon
    We've started using the Application Foundations for SharePoint 2010 in some of our projects at work, and I came across a nasty issue with the hierarchical configuration settings.  I have some settings that I am storing at the Farm level, and as I was testing my code it seemed like the settings were not being saved - at least that is what it appeared was the case at first.  However, I happened to reset IIS and the settings suddenly appeared.  Immediately, I figured that it must be a caching issue and dug into the code base.  I found that there was a 10 second caching mechanism in the SPFarmPropertyBag and the SPWebAppPropertyBag classes.  So I ran another test where I waited 10 seconds to make sure that enough time had passed to force the caching mechanism to reset the data.  After 10 minutes the cache had still not cleared.  After digging a bit further, I found a double lock check that looked a bit off in the GetSettingsStore() method of the SPFarmPropertyBag class: if (_settingStore == null || (DateTime.Now.Subtract(lastLoad).TotalSeconds) > cacheInterval)) { //Need to exist so don't deadlock. rrLock.EnterWriteLock(); try { //make sure first another thread didn't already load... if (_settingStore == null) { _settingStore = WebAppSettingStore.Load(this.webApplication); lastLoad = DateTime.Now; } } finally { rrLock.ExitWriteLock(); } } What ends up happening here is the outer check determines if the _settingStore is null or the cache has expired, but the inner check is just checking if the _settingStore is null (which is never the case after the first time it's been loaded).  Ergo, the cached settings are never reset.  The fix is really easy, just add the cache checking back into the inner if statement. //make sure first another thread didn't already load... if (_settingStore == null || (DateTime.Now.Subtract(lastLoad).TotalSeconds) > cacheInterval) { _settingStore = WebAppSettingStore.Load(this.webApplication); lastLoad = DateTime.Now; } And then it starts working just fine. as long as you wait at least 10 seconds for the cache to clear.

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  • ClearTrace Performance on 170GB of Trace Files

    - by Bill Graziano
    I’ve always worked to make ClearTrace perform well.  That’s probably because I spend so much time watching it work.  I’m often going through two or three gigabytes of trace files but I rarely get the chance to run it on a really large set of files. One of my clients wanted to run a full trace for a week and then analyze the results.  At the end of that week we had 847 200MB trace files for a total of nearly 170GB. I regularly use 200MB trace files when I monitor production systems.  I usually get around 300,000 statements in a file that size if it’s mostly stored procedures.  So those 847 trace files contained roughly 250 million statements.  (That’s 730 bytes per statement if you’re keeping track.  Newer trace files have some compression in them but I’m not exactly sure what they’re doing.)  On a system running 1,000 statements per second I get a new file every five minutes or so. It took 27 hours to process these files on an older development box.  That works out to 1.77MB/second.  That means ClearTrace processed about 2,654 statements per second. You can query the data while you’re loading it but I’ve found it works better to use a second instance of ClearTrace to do this.  I’m not sure why yet but I think there’s still some dependency between the two processes. ClearTrace is almost always CPU bound.  It’s really just a huge, ugly collection of regular expressions.  It only writes a summary to its database at the end of each trace file so that usually isn’t a bottleneck.  At the end of this process, the executable was using roughly 435MB of RAM.  Certainly more than when it started but I think that’s acceptable. The database where all this is stored started out at 100MB.  After processing 170GB of trace files the database had grown to 203MB.  The space savings are due to the “datawarehouse-ish” design and only storing a summary of each trace file. You can download ClearTrace for SQL Server 2008 or test out the beta version for SQL Server 2012.  Happy Tuning!

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  • Movement prediction for non-shooters

    - by ShadowChaser
    I'm working on an isometric (2D) game with moderate-scale multiplayer - 20-30 players. I've had some difficulty getting a good movement prediction implementation in place. Right now, clients are authoritative for their own position. The server performs validation and broad-scale cheat detection, and I fully realize that the system will never be fully robust against cheating. However, the performance and implementation tradeoffs work well for me right now. Given that I'm dealing with sprite graphics, the game has 8 defined directions rather than free movement. Whenever the player changes their direction or speed (walk, run, stop), a "true" 3D velocity is set on the entity and a packet it sent to the server with the new movement state. In addition, every 250ms additional packets are transmitted with the player's current position for state updates on the server as well as for client prediction. After the server validates the packet, it gets automatically distributed to all of the other "nearby" players. Client-side, all entities with non-zero velocity (ie/ moving entities) are tracked and updated by a rudimentary "physics" system - basically nothing more than changing the position by the velocity according to the elapsed time slice (40ms or so). What I'm struggling with is how to implement clean movement prediction. I have the nagging suspicion that I've made a design mistake somewhere. I've been over the Unreal, Half-life, and all other movement prediction/lag compensation articles I could find, but they all seam geared toward shooters: "Don't send each control change, send updates every 120ms, server is authoritative, client predicts, etc". Unfortunately, that style of design won't work well for me - there's no 3D environment so each individual state change is important. 1) Most of the samples I saw tightly couple movement prediction right into the entities themselves. For example, storing the previous state along with the current state. I'd like to avoid that and keep entities with their "current state" only. Is there a better way to handle this? 2) What should happen when the player stops? I can't interpolate to the correct position, since they might need to walk backwards or another strange direction if their position is too far ahead. 3) What should happen when entities collide? If the current player collides with something, the answer is simple - just stop the player from moving. But what happens if two entities take up the same space on the server? What if the local prediction causes a remote entity to collide with the player or another entity - do I stop them as well? If the prediction had the misfortune of sticking them in front of a wall that the player has gone around, the prediction will never be able to compensate and once the error gets to high the entity will snap to the new position.

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