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  • Apache2 - rewrite a bunch of specified pathname URLs to one URL

    - by James Nine
    I need to rewrite a bunch of urls (about 100 or so) for SEO purposes, and there may be more being added in the future (probably another 50-100 later on). I need a flexible way of doing this and so far, the only way I can think of is to edit the .htaccess file using the rewrite engine. For example, I have a bunch of urls like this (please note that the query string is irrelevant, and dynamic; it could be anything. I was only using them purely as an example. I am only focusing on the pathname--the part between the hostname and query string, as marked in bold below): http://example.com/seo_term1?utm_source=google&utm_medium=cpc&utm_campaign=seo_term http://example.com/another_seo_term2?utm_source=facebook&utm_medium=cpc&utm_campaign=seo_term http://example.com/yet_another_seo_term3?utm_source=example_ad_network&utm_medium=cpc&utm_campaign=seo_term http://example.com/foobar_seo_term4 http://example.com/blah_seo_term5?test=1 etc... And they are all being rewritten to (for now): http://example.com/ What's the most efficient/effective way of doing this so that I may be able to add more terms in the future? One solution I came across is to do this (in the .htaccess file): RewriteEngine on RewriteCond %{REQUEST_FILENAME} !-f RewriteCond %{REQUEST_FILENAME} !-d RewriteRule ^(.*)$ / [NC,QSA] However, the problem with this solution is that even invalid urls (such as http://example.com/blah) will be rewritten to http://example.com instead of giving a 404 code (which is what it is supposed to do anyway). I'm still trying to figure out how all this works, and the only way I can think of is to write 100 more RewriteCond statements (such as: RewriteCond %{REQUEST_URI} =/seo_term1 [NC,OR]) before the RewriteRule directive. For example: RewriteEngine on RewriteCond %{REQUEST_FILENAME} !-f RewriteCond %{REQUEST_FILENAME} !-d RewriteCond %{REQUEST_URI} =/seo_term1 [NC,OR] RewriteCond %{REQUEST_URI} =/another_seo_term2 [NC,OR] RewriteCond %{REQUEST_URI} =/yet_another_seo_term3 [NC,OR] RewriteCond %{REQUEST_URI} =/foobar_seo_term4 [NC,OR] RewriteCond %{REQUEST_URI} =/blah_seo_term5 [NC] RewriteRule ^(.*)$ / [NC,QSA] But that doesn't sound very efficient to me. Is there a better way?

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  • Synchronize two directories on linux pc

    - by Gab
    I need a distributed filesystem (or a synchronization tool) that is capable of keeping a directory synchronized across 4 pc. My requirements are: offline access (data must be available offline on each pc) preserve execution rights: some files are marked executable on a linux partition. This flag should be replicated. efficient sync strategy: some of my files are 20GB, they are changed quite often, but in very little parts (Virtualbox images). Delta transmissions are welcome. efficient handling of space: no history for files, files shouldn't be copied to temp directories "just in case you break it". it must propagate deletions of files modification can happen in any of the 4 pcs, they should be propagated when other pc are connected. Other specs of my solution are: Sync is over a lan, the total amount of data to be synced is around 180GB, in some ten thousand files. Changes are small, but can happen in big files. At the moment i'm interested in a linux only solution. conflicts either don't happen or are solved with "last one wins" I haven't found any good solution. I've been trying: unison: it is the only one working at the moment, but during the hashing phase it hangs my pc for some minute, disk light steady on. Sparkleshare doesn't handle large files nicely. It keeps an history of all your changes that grows up indefinitely. They promise it will be fixed in next releases, but at the moment it still doesn't fit my needs. owncloud (keeps history of each file i change) coda ? (help! i couldn't set it up correctly!) git-annex assistant transforms all your files in symlinks and mark the original file as read only ("just in case you make a mistake while you modify it"!). Before you edit a file you have to issue a special command "git-annex unlock", that creates a local copy of the file, and you have to remember to lock it again if you want it synchronized. What to try next?

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  • Linux RHEL : Making disk image efficiently

    - by TheProfoundGeek
    I have a linux box having RHEL. Its disk (hda1) is having free space of about 25GB. I have an another disk (hda2) which is of 250GB having another RHEL instance, it's partitioned for 200GB. Data on the disk occupies about 21GB of data. The image of hda2 needs to be taken and restored on other disk of same specs. What is the best way to make image file of the hda2? Ideally the images size should be around 25GBs as the actual data on the disk is just 21GB. I am aware about the following two methods. Method 1 : Raw Image dd if=/dev/hda2 of=/path/to/image dd if=/path/to/image of=/dev/hda3 Question 1 : Will the above method make a gigantic image of 250GBs? Is it efficient? Method 2 : Compressed Image. dd if=/dev/hda2 | gzip > /path/to/image.gz gzip -dc /path/to/image.gz | dd of=/dev/hda2 Question 2 : I tried the method 2, its taking too long. What are the pit falls of this methods? Which of the above method id efficient and why? Is there any other Linux utility which can do the job? Third party tools are no no.

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  • Mobile App Data Syncronization

    - by Matt Rogish
    Let's say I have a mobile app that uses HTML5 SQLite DB (and/or the HTML5 key-value store). Assets (media files, PDFs, etc.) are stored locally on the mobile device. Luckily enough, the mobile device is a read-only copy of the "centralized" storage, so the mobile device won't have to propagate changes upstream. However, as the server changes assets (creates new ones, modifies existing, deletes old ones) I need to propagate those changes back to the mobile app. Assume that server changes are grouped into changesets (version number n) that contain some information (added element XYZ, deleted id = 45, etc.) and that the mobile device has limited CPU/bandwidth, so most of the processing has to take place on the server. I can think of a couple of methods to do this. All have trade-offs and at this point, I'm unsure which is the right course of action... Method 1: For change set n, store the "diff" of the current n and previous n-1. When a client with version y asks if there have been any changes, send the change sets from version y up to the current version. e.g. added item 334, contents: xxx. Deleted picture 44. Deleted PDF 11. Changed 33. added picture 99. Characteristics: Diffs take up space, although in theory would be kept small. However, all diffs must be kept around indefinitely (should a v1 app have not been updated for a year, must apply v2..v100). High latency devices (mobile apps) will incur a penalty to send lots of small files (assume cannot be zipped or tarr'd up into one file) Very few server CPU resources required, as all it does is send the client a list of files "Dumb" - if I change an item in change set 3, and change it to something else in 4, the client is going to perform both actions, even though #3 is rendered moot by #4. Or, if an asset is added in #4 and removed in #5 - the client will download a file just to delete it later. Method 2: Very similar to method 1 except on the server, do some sort of a diff between the change sets represented by the app version and server version. Package that up and send that single change set to the client. Characteristics: Client-efficient: The client only has to process one file, duplicate or irrelevant changes are stripped out. Server CPU/space intensive. The change sets must be diff'd and then written out to a file that is then sent to the client. Makes diff server scalability an issue. Possibly ways to cache the results and re-use them, but in the wild there's likely to be a lot of different versions so the diff re-use has a limit Diff algorithm is complicated. The change sets must be structured in such a way that an efficient and effective diff can be performed. Method 3: Instead of keeping diffs, write out the entire versioned asset collection to a mobile-database import file. When client requests an update, send the entire database to client and have them update their assets appropriately. Characteristics: Conceptually simple -- easy to develop and deploy Very inefficient as the client database is restored every update. If only one new thing was added, the whole database is refreshed. Server space and CPU efficient. Only the latest version DB needs kept around and the server just throws the file to the client. Others?? Thoughts? Thanks!!

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  • (Ordered) Set Partitions in fixed-size Blocks

    - by Eugen
    Here is a function I would like to write but am unable to do so. Even if you don't / can't give a solution I would be grateful for tips. For example, I know that there is a correlation between the ordered represantions of the sum of an integer and ordered set partitions but that alone does not help me in finding the solution. So here is the description of the function I need: The Task Create an efficient* function List<int[]> createOrderedPartitions(int n_1, int n_2,..., int n_k) that returns a list of arrays of all set partions of the set {0,...,n_1+n_2+...+n_k-1} in number of arguments blocks of size (in this order) n_1,n_2,...,n_k (e.g. n_1=2, n_2=1, n_3=1 -> ({0,1},{3},{2}),...). Here is a usage example: int[] partition = createOrderedPartitions(2,1,1).get(0); partition[0]; // -> 0 partition[1]; // -> 1 partition[2]; // -> 3 partition[3]; // -> 2 Note that the number of elements in the list is (n_1+n_2+...+n_n choose n_1) * (n_2+n_3+...+n_n choose n_2) * ... * (n_k choose n_k). Also, createOrderedPartitions(1,1,1) would create the permutations of {0,1,2} and thus there would be 3! = 6 elements in the list. * by efficient I mean that you should not initially create a bigger list like all partitions and then filter out results. You should do it directly. Extra Requirements If an argument is 0 treat it as if it was not there, e.g. createOrderedPartitions(2,0,1,1) should yield the same result as createOrderedPartitions(2,1,1). But at least one argument must not be 0. Of course all arguments must be = 0. Remarks The provided pseudo code is quasi Java but the language of the solution doesn't matter. In fact, as long as the solution is fairly general and can be reproduced in other languages it is ideal. Actually, even better would be a return type of List<Tuple<Set>> (e.g. when creating such a function in Python). However, then the arguments wich have a value of 0 must not be ignored. createOrderedPartitions(2,0,2) would then create [({0,1},{},{2,3}),({0,2},{},{1,3}),({0,3},{},{1,2}),({1,2},{},{0,3}),...] Background I need this function to make my mastermind-variation bot more efficient and most of all the code more "beautiful". Take a look at the filterCandidates function in my source code. There are unnecessary / duplicate queries because I'm simply using permutations instead of specifically ordered partitions. Also, I'm just interested in how to write this function. My ideas for (ugly) "solutions" Create the powerset of {0,...,n_1+...+n_k}, filter out the subsets of size n_1, n_2 etc. and create the cartesian product of the n subsets. However this won't actually work because there would be duplicates, e.g. ({1,2},{1})... First choose n_1 of x = {0,...,n_1+n_2+...+n_n-1} and put them in the first set. Then choose n_2 of x without the n_1 chosen elements beforehand and so on. You then get for example ({0,2},{},{1,3},{4}). Of course, every possible combination must be created so ({0,4},{},{1,3},{2}), too, and so on. Seems rather hard to implement but might be possible. Research I guess this goes in the direction I want however I don't see how I can utilize it for my specific scenario. http://rosettacode.org/wiki/Combinations

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  • Organizations &amp; Architecture UNISA Studies &ndash; Chap 7

    - by MarkPearl
    Learning Outcomes Name different device categories Discuss the functions and structure of I/.O modules Describe the principles of Programmed I/O Describe the principles of Interrupt-driven I/O Describe the principles of DMA Discuss the evolution characteristic of I/O channels Describe different types of I/O interface Explain the principles of point-to-point and multipoint configurations Discuss the way in which a FireWire serial bus functions Discuss the principles of InfiniBand architecture External Devices An external device attaches to the computer by a link to an I/O module. The link is used to exchange control, status, and data between the I/O module and the external device. External devices can be classified into 3 categories… Human readable – e.g. video display Machine readable – e.g. magnetic disk Communications – e.g. wifi card I/O Modules An I/O module has two major functions… Interface to the processor and memory via the system bus or central switch Interface to one or more peripheral devices by tailored data links Module Functions The major functions or requirements for an I/O module fall into the following categories… Control and timing Processor communication Device communication Data buffering Error detection I/O function includes a control and timing requirement, to coordinate the flow of traffic between internal resources and external devices. Processor communication involves the following… Command decoding Data Status reporting Address recognition The I/O device must be able to perform device communication. This communication involves commands, status information, and data. An essential task of an I/O module is data buffering due to the relative slow speeds of most external devices. An I/O module is often responsible for error detection and for subsequently reporting errors to the processor. I/O Module Structure An I/O module functions to allow the processor to view a wide range of devices in a simple minded way. The I/O module may hide the details of timing, formats, and the electro mechanics of an external device so that the processor can function in terms of simple reads and write commands. An I/O channel/processor is an I/O module that takes on most of the detailed processing burden, presenting a high-level interface to the processor. There are 3 techniques are possible for I/O operations Programmed I/O Interrupt[t I/O DMA Access Programmed I/O When a processor is executing a program and encounters an instruction relating to I/O it executes that instruction by issuing a command to the appropriate I/O module. With programmed I/O, the I/O module will perform the requested action and then set the appropriate bits in the I/O status register. The I/O module takes no further actions to alert the processor. I/O Commands To execute an I/O related instruction, the processor issues an address, specifying the particular I/O module and external device, and an I/O command. There are four types of I/O commands that an I/O module may receive when it is addressed by a processor… Control – used to activate a peripheral and tell it what to do Test – Used to test various status conditions associated with an I/O module and its peripherals Read – Causes the I/O module to obtain an item of data from the peripheral and place it in an internal buffer Write – Causes the I/O module to take an item of data form the data bus and subsequently transmit that data item to the peripheral The main disadvantage of this technique is it is a time consuming process that keeps the processor busy needlessly I/O Instructions With programmed I/O there is a close correspondence between the I/O related instructions that the processor fetches from memory and the I/O commands that the processor issues to an I/O module to execute the instructions. Typically there will be many I/O devices connected through I/O modules to the system – each device is given a unique identifier or address – when the processor issues an I/O command, the command contains the address of the address of the desired device, thus each I/O module must interpret the address lines to determine if the command is for itself. When the processor, main memory and I/O share a common bus, two modes of addressing are possible… Memory mapped I/O Isolated I/O (for a detailed explanation read page 245 of book) The advantage of memory mapped I/O over isolated I/O is that it has a large repertoire of instructions that can be used, allowing more efficient programming. The disadvantage of memory mapped I/O over isolated I/O is that valuable memory address space is sued up. Interrupts driven I/O Interrupt driven I/O works as follows… The processor issues an I/O command to a module and then goes on to do some other useful work The I/O module will then interrupts the processor to request service when is is ready to exchange data with the processor The processor then executes the data transfer and then resumes its former processing Interrupt Processing The occurrence of an interrupt triggers a number of events, both in the processor hardware and in software. When an I/O device completes an I/O operations the following sequence of hardware events occurs… The device issues an interrupt signal to the processor The processor finishes execution of the current instruction before responding to the interrupt The processor tests for an interrupt – determines that there is one – and sends an acknowledgement signal to the device that issues the interrupt. The acknowledgement allows the device to remove its interrupt signal The processor now needs to prepare to transfer control to the interrupt routine. To begin, it needs to save information needed to resume the current program at the point of interrupt. The minimum information required is the status of the processor and the location of the next instruction to be executed. The processor now loads the program counter with the entry location of the interrupt-handling program that will respond to this interrupt. It also saves the values of the process registers because the Interrupt operation may modify these The interrupt handler processes the interrupt – this includes examination of status information relating to the I/O operation or other event that caused an interrupt When interrupt processing is complete, the saved register values are retrieved from the stack and restored to the registers Finally, the PSW and program counter values from the stack are restored. Design Issues Two design issues arise in implementing interrupt I/O Because there will be multiple I/O modules, how does the processor determine which device issued the interrupt? If multiple interrupts have occurred, how does the processor decide which one to process? Addressing device recognition, 4 general categories of techniques are in common use… Multiple interrupt lines Software poll Daisy chain Bus arbitration For a detailed explanation of these approaches read page 250 of the textbook. Interrupt driven I/O while more efficient than simple programmed I/O still requires the active intervention of the processor to transfer data between memory and an I/O module, and any data transfer must traverse a path through the processor. Thus is suffers from two inherent drawbacks… The I/O transfer rate is limited by the speed with which the processor can test and service a device The processor is tied up in managing an I/O transfer; a number of instructions must be executed for each I/O transfer Direct Memory Access When large volumes of data are to be moved, an efficient technique is direct memory access (DMA) DMA Function DMA involves an additional module on the system bus. The DMA module is capable of mimicking the processor and taking over control of the system from the processor. It needs to do this to transfer data to and from memory over the system bus. DMA must the bus only when the processor does not need it, or it must force the processor to suspend operation temporarily (most common – referred to as cycle stealing). When the processor wishes to read or write a block of data, it issues a command to the DMA module by sending to the DMA module the following information… Whether a read or write is requested using the read or write control line between the processor and the DMA module The address of the I/O device involved, communicated on the data lines The starting location in memory to read from or write to, communicated on the data lines and stored by the DMA module in its address register The number of words to be read or written, communicated via the data lines and stored in the data count register The processor then continues with other work, it delegates the I/O operation to the DMA module which transfers the entire block of data, one word at a time, directly to or from memory without going through the processor. When the transfer is complete, the DMA module sends an interrupt signal to the processor, this the processor is involved only at the beginning and end of the transfer. I/O Channels and Processors Characteristics of I/O Channels As one proceeds along the evolutionary path, more and more of the I/O function is performed without CPU involvement. The I/O channel represents an extension of the DMA concept. An I/O channel ahs the ability to execute I/O instructions, which gives it complete control over I/O operations. In a computer system with such devices, the CPU does not execute I/O instructions – such instructions are stored in main memory to be executed by a special purpose processor in the I/O channel itself. Two types of I/O channels are common A selector channel controls multiple high-speed devices. A multiplexor channel can handle I/O with multiple characters as fast as possible to multiple devices. The external interface: FireWire and InfiniBand Types of Interfaces One major characteristic of the interface is whether it is serial or parallel parallel interface – there are multiple lines connecting the I/O module and the peripheral, and multiple bits are transferred simultaneously serial interface – there is only one line used to transmit data, and bits must be transmitted one at a time With new generation serial interfaces, parallel interfaces are becoming less common. In either case, the I/O module must engage in a dialogue with the peripheral. In general terms the dialog may look as follows… The I/O module sends a control signal requesting permission to send data The peripheral acknowledges the request The I/O module transfers data The peripheral acknowledges receipt of data For a detailed explanation of FireWire and InfiniBand technology read page 264 – 270 of the textbook

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  • SQL SERVER – Video – Beginning Performance Tuning with SQL Server Execution Plan

    - by pinaldave
    Traveling can be most interesting or most exhausting experience. However, traveling is always the most enlightening experience one can have. While going to long journey one has to prepare a lot of things. Pack necessary travel gears, clothes and medicines. However, the most essential part of travel is the journey to the destination. There are many variations one prefer but the ultimate goal is to have a delightful experience during the journey. Here is the video available which explains how to begin with SQL Server Execution plans. Performance Tuning is a Journey Performance tuning is just like a long journey. The goal of performance tuning is efficient and least resources consuming query execution with accurate results. Just as maps are the most essential aspect of performance tuning the same way, execution plans are essentially maps for SQL Server to reach to the resultset. The goal of the execution plan is to find the most efficient path which translates the least usage of the resources (CPU, memory, IO etc). Execution Plans are like Maps When online maps were invented (e.g. Bing, Google, Mapquests etc) initially it was not possible to customize them. They were given a single route to reach to the destination. As time evolved now it is possible to give various hints to the maps, for example ‘via public transport’, ‘walking’, ‘fastest route’, ‘shortest route’, ‘avoid highway’. There are places where we manually drag the route and make it appropriate to our needs. The same situation is with SQL Server Execution Plans, if we want to tune the queries, we need to understand the execution plans and execution plans internals. We need to understand the smallest details which relate to execution plan when we our destination is optimal queries. Understanding Execution Plans The biggest challenge with maps are figuring out the optimal path. The same way the  most common challenge with execution plans is where to start from and which precise route to take. Here is a quick list of the frequently asked questions related to execution plans: Should I read the execution plans from bottoms up or top down? Is execution plans are left to right or right to left? What is the relational between actual execution plan and estimated execution plan? When I mouse over operator I see CPU and IO but not memory, why? Sometime I ran the query multiple times and I get different execution plan, why? How to cache the query execution plan and data? I created an optimal index but the query is not using it. What should I change – query, index or provide hints? What are the tools available which helps quickly to debug performance problems? Etc… Honestly the list is quite a big and humanly impossible to write everything in the words. SQL Server Performance:  Introduction to Query Tuning My friend Vinod Kumar and I have created for the same a video learning course for beginning performance tuning. We have covered plethora of the subject in the course. Here is the quick list of the same: Execution Plan Basics Essential Indexing Techniques Query Design for Performance Performance Tuning Tools Tips and Tricks Checklist: Performance Tuning We believe we have covered a lot in this four hour course and we encourage you to go over the video course if you are interested in Beginning SQL Server Performance Tuning and Query Tuning. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Optimization, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology, Video Tagged: Execution Plan

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  • Developer Training – Importance and Significance – Part 1

    - by pinaldave
    Developer Training - Importance and Significance - Part 1 Developer Training – Employee Morals and Ethics – Part 2 Developer Training – Difficult Questions and Alternative Perspective - Part 3 Developer Training – Various Options for Developer Training – Part 4 Developer Training – A Conclusive Summary- Part 5 Can anyone remember their final day of schooling?  This is probably a silly question because – of course you can!  Many people mark this as the most exciting, happiest day of their life.  It marks the end of testing, the end of following rules set by teachers, and the beginning of finally being able to earn money and work in your chosen field. Beginning in Real World However, many former-students will be disappointed to find out that once they become employees, learning is not over.  Many companies are discovering the importance and benefits to training their employees.  You can breathe a sigh of relief, though, because much for this kind of training there are not usually tests! We often think that we go to school for our younger years so that we do all our learning all at once, and then for the rest of our lives we use that knowledge.  But in so many cases, but especially for developers, the opposite is true.  It takes many years of schools to learn the basics of a field, and then our careers are spent learning to become experts. For this, and so many other reasons, training is very important.  Example one: developer training leads to better employees.  A company is only as good as the people it employs, and one way to ensure that you have employed the right candidate is through training.  Training can take a regular “stone” and polish it into a “diamond.”  Employees who have been well-trained will be better at their jobs and produce a better product. Most Expensive Resource Did you know that one of the most expensive operating costs for any company is not buying goods, or advertising, but its employees – especially having to hire new employees.  Bringing in new people, getting them up to speed, and providing them with perks to attract them to a company is a huge cost for companies.  So employee retention – keep the employees you already have, and keeping them happy – is incredibly important from a business aspect.  And research shows that a well-trained employee is a happy employee.  They feel more confident in their job, happier with their position, and more cared-about – and therefore less likely to leave in search of a better job.  Employee training leads to better retention. Good Moral On the subject of keeping employees happy in order to keep them at a company, the complement to that research shows that happier employees are more efficient and overall better at their jobs.  You don’t have to be a scientist to figure out why this is true.  An employee who feel that his company cares about him and his educational future will work harder for the company.  He or she will put in that extra hour during the busy season that makes all the difference in the end.  Good morale is good for the company. If good morale is better for the company, you know that it goes hand-in-hand with something even better – better efficiency.  An employee who is well trained obviously knows more about their job and all the technical aspects.  That means when a problem crops up – and they inevitably do – this employee will be well-equipped to deal with that problem with fewer problems, and no need to go searching for help from higher up.  When employees are well trained, companies run more smoothly. A Better Product Of course, all of these “pros” for employee training are leading up to the one thing that companies truly care about – a better product.  We have shown that employees who have been trained to be competitive in the market are happier at the company, they are more efficient, and their morale is better.  The overall result is that the company’s product – whether it is a database, piece of equipment, or even a physical good – is better.  And a better product will always be more competitive on the market. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Developer Training, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • SQL SERVER – Guest Post – Jacob Sebastian – Filestream – Wait Types – Wait Queues – Day 22 of 28

    - by pinaldave
    Jacob Sebastian is a SQL Server MVP, Author, Speaker and Trainer. Jacob is one of the top rated expert community. Jacob wrote the book The Art of XSD – SQL Server XML Schema Collections and wrote the XML Chapter in SQL Server 2008 Bible. See his Blog | Profile. He is currently researching on the subject of Filestream and have submitted this interesting article on the very subject. What is FILESTREAM? FILESTREAM is a new feature introduced in SQL Server 2008 which provides an efficient storage and management option for BLOB data. Many applications that deal with BLOB data today stores them in the file system and stores the path to the file in the relational tables. Storing BLOB data in the file system is more efficient that storing them in the database. However, this brings up a few disadvantages as well. When the BLOB data is stored in the file system, it is hard to ensure transactional consistency between the file system data and relational data. Some applications store the BLOB data within the database to overcome the limitations mentioned earlier. This approach ensures transactional consistency between the relational data and BLOB data, but is very bad in terms of performance. FILESTREAM combines the benefits of both approaches mentioned above without the disadvantages we examined. FILESTREAM stores the BLOB data in the file system (thus takes advantage of the IO Streaming capabilities of NTFS) and ensures transactional consistency between the BLOB data in the file system and the relational data in the database. For more information on the FILESTREAM feature, visit: http://beyondrelational.com/filestream/default.aspx FILESTREAM Wait Types Since this series is on the different SQL Server wait types, let us take a look at the various wait types that are related to the FILESTREAM feature. FS_FC_RWLOCK This wait type is generated by FILESTREAM Garbage Collector. This occurs when Garbage collection is disabled prior to a backup/restore operation or when a garbage collection cycle is being executed. FS_GARBAGE_COLLECTOR_SHUTDOWN This wait type occurs when during the cleanup process of a garbage collection cycle. It indicates that that garbage collector is waiting for the cleanup tasks to be completed. FS_HEADER_RWLOCK This wait type indicates that the process is waiting for obtaining access to the FILESTREAM header file for read or write operation. The FILESTREAM header is a disk file located in the FILESTREAM data container and is named “filestream.hdr”. FS_LOGTRUNC_RWLOCK This wait type indicates that the process is trying to perform a FILESTREAM log truncation related operation. It can be either a log truncate operation or to disable log truncation prior to a backup or restore operation. FSA_FORCE_OWN_XACT This wait type occurs when a FILESTREAM file I/O operation needs to bind to the associated transaction, but the transaction is currently owned by another session. FSAGENT This wait type occurs when a FILESTREAM file I/O operation is waiting for a FILESTREAM agent resource that is being used by another file I/O operation. FSTR_CONFIG_MUTEX This wait type occurs when there is a wait for another FILESTREAM feature reconfiguration to be completed. FSTR_CONFIG_RWLOCK This wait type occurs when there is a wait to serialize access to the FILESTREAM configuration parameters. Waits and Performance System waits has got a direct relationship with the overall performance. In most cases, when waits increase the performance degrades. SQL Server documentation does not say much about how we can reduce these waits. However, following the FILESTREAM best practices will help you to improve the overall performance and reduce the wait types to a good extend. Read all the post in the Wait Types and Queue series. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, Readers Contribution, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQL Wait Stats, SQL Wait Types, T SQL, Technology Tagged: Filestream

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  • F# and the rose-tinted reflection

    - by CliveT
    We're already seeing increasing use of many cores on client desktops. It is a change that has been long predicted. It is not just a change in architecture, but our notions of efficiency in a program. No longer can we focus on the asymptotic complexity of an algorithm by counting the steps that a single core processor would take to execute it. Instead we'll soon be more concerned about the scalability of the algorithm and how well we can increase the performance as we increase the number of cores. This may even lead us to throw away our most efficient algorithms, and switch to less efficient algorithms that scale better. We might even be willing to waste cycles in order to speculatively execute at the algorithm rather than the hardware level. State is the big headache in this parallel world. At the hardware level, main memory doesn't necessarily contain the definitive value corresponding to a particular address. An update to a location might still be held in a CPU's local cache and it might be some time before the value gets propagated. To get the latest value, and the notion of "latest" takes a lot of defining in this world of rapidly mutating state, the CPUs may well need to communicate to decide who has the definitive value of a particular address in order to avoid lost updates. At the user program level, this means programmers will need to lock objects before modifying them, or attempt to avoid the overhead of locking by understanding the memory models at a very deep level. I think it's this need to avoid statefulness that has led to the recent resurgence of interest in functional languages. In the 1980s, functional languages started getting traction when research was carried out into how programs in such languages could be auto-parallelised. Sadly, the impracticality of some of the languages, the overheads of communication during this parallel execution, and rapid improvements in compiler technology on stock hardware meant that the functional languages fell by the wayside. The one thing that these languages were good at was getting rid of implicit state, and this single idea seems like a solution to the problems we are going to face in the coming years. Whether these languages will catch on is hard to predict. The mindset for writing a program in a functional language is really very different from the way that object-oriented problem decomposition happens - one has to focus on the verbs instead of the nouns, which takes some getting used to. There are a number of hybrid functional/object languages that have been becoming more popular in recent times. These half-way houses make it easy to use functional ideas for some parts of the program while still allowing access to the underlying object-focused platform without a great deal of impedance mismatch. One example is F# running on the CLR which, in Visual Studio 2010, has because a first class member of the pack. Inside Visual Studio 2010, the tooling for F# has improved to the point where it is easy to set breakpoints and watch values change while debugging at the source level. In my opinion, it is the tooling support that will enable the widespread adoption of functional languages - without this support, people will put off any transition into the functional world for as long as they possibly can. Without tool support it will make it hard to learn these languages. One tool that doesn't currently support F# is Reflector. The idea of decompiling IL to a functional language is daunting, but F# is potentially so important I couldn't dismiss the idea. As I'm currently developing Reflector 6.5, I thought it wise to take four days just to see how far I could get in doing so, even if it achieved little more than to be clearer on how much was possible, and how long it might take. You can read what happened here, and of the insights it gave us on ways to improve the tool.

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  • Encode two integers into colour values and compare them in a HLSL shader

    - by Ben Slinger
    I am writing a 2D point and click adventure game in Monogame, and I'd like to be able to create an image mask for every room which defines which parts of the background a character can walk behind, and at which Y value a character needs to be at for the background to be drawn above the character. I haven't done any shader work before but after doing some reading I thought the following solution should work: Create a mask for the room with different walk behind areas painted in a colour that defines the baseline Y value (Walk Behind Mask) Render all objects to a RenderTarget2D (Base Texture) Render all objects to a different RenderTarget2D, but changing every pixel of each object to a colour that defines its Y value (Position Mask) Pass these two textures plus the image mask into the shader, and for each pixel compare the colour of the image mask to the colour of the Position Mask to the Walk Behind Mask - if the Position Mask pixel is larger (thus lower on the screen and closer to the camera) than the Walk Behind Mask, draw the pixel from the Base Texture, otherwise draw a transparent pixel (allowing the background to show through). I've got it mostly working, but I'm having trouble packing and unpacking the Y values into colours and retrieving them correctly in the shader. Here are some code examples of how I'm doing it so far: (When drawing to the Position Mask RenderTarget2D) Color posColor = new Color(((int)Position.Y >> 16) & 255, ((int)Position.Y >> 8) & 255, (int)Position.Y & 255); So as far as I can tell, this should be taking the first 3 bytes of the position integer and encoding them into a 4 byte colour (ignoring the alpha as the 4th byte). This seems to work fine, as when my character is at Y = 600, the resulting Color from this is: {[Color: R=0, G=2, B=88, A=255, PackedValue=4283957760]}. I then have an area in my Walk Behind Mask that I only want the character to be displayed behind if his Y value is lower than 655, so I've painted it with R=0, G=2, B=143, A=255. Now, I think I have the shader OK as well, here's what I have: sampler BaseTexture : register(s0); sampler MaskTexture : register(s1); sampler PositionTexture : register(s2); float4 mask( float2 coords : TEXCOORD0 ) : COLOR0 { float4 color = tex2D(BaseTexture, coords); float4 maskColor = tex2D(MaskTexture, coords); float4 positionColor = tex2D(PositionTexture, coords); float maskCompare = (maskColor.r * pow(2,24)) + (maskColor.g * pow(2,16)) + (maskColor.b * pow(2,8)); float positionCompare = (positionColor.r * pow(2,24)) + (positionColor.g * pow(2,16)) + (positionColor.b * pow(2,8)); return positionCompare < maskCompare ? float4(0,0,0,0) : color; } technique Technique1 { pass NoEffect { PixelShader = compile ps_3_0 mask(); } } This isn't working, however - currently all characters are displayed behind the walk behind area, regardless of their Y value. I tried printing out some debug info by grabbing the pixel from both the Position Mask and the Walk Under Mask under the current mouse position, and it seems like maybe the colours aren't being rendered to the Position Mask correctly? When calculating the colour in that code above I'm getting R=0, G=2, B=88, A=255, but when I mouseover my character I get R=0, G=0, B=30, A=255. Any ideas what I'm doing wrong? It seems like maybe I'm losing some information when rendering to the RenderTarget2D, but I'm now knowledgeable enough to figure out what's happening. Also, I should probably ask, is this an efficient way to do this? Will there be a performance impact? Edit: Whoops, turns out there was a bug that I'd introduced myself, I was drawing out the Position Mask with the position Color, left over from some early testing I was doing. So this solution is working perfectly, though I'm still interested in whether this is an efficient solution performance wise.

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  • SSIS Technique to Remove/Skip Trailer and/or Bad Data Row in a Flat File

    - by Compudicted
    I noticed that the question on how to skip or bypass a trailer record or a badly formatted/empty row in a SSIS package keeps coming back on the MSDN SSIS Forum. I tried to figure out the reason why and after an extensive search inside the forum and outside it on the entire Web (using several search engines) I indeed found that it seems even thought there is a number of posts and articles on the topic none of them are employing the simplest and the most efficient technique. When I say efficient I mean the shortest time to solution for the fellow developers. OK, enough talk. Let’s face the problem: Typically a flat file (e.g. a comma delimited/CSV) needs to be processed (loaded into a database in most cases really). Oftentimes, such an input file is produced by some sort of an out of control, 3-rd party solution and would come in with some garbage characters and/or even malformed/miss-formatted rows. One such example could be this imaginary file: As you can see several rows have no data and there is an occasional garbage character (1, in this example on row #7). Our task is to produce a clean file that will only capture the meaningful data rows. As an aside, our output/target may be a database table, but for the purpose of this exercise we will simply re-format the source. Let’s outline our course of action to start off: Will use SSIS 2005 to create a DFT; The DFT will use a Flat File Source to our input [bad] flat file; We will use a Conditional Split to process the bad input file; and finally Dump the resulting data to a new [clean] file. Well, only four steps, let’s see if it is too much of work. 1: Start the BIDS and add a DFT to the Control Flow designer (I named it Process Dirty File DFT): 2, and 3: I had added the data viewer to just see what I am getting, alas, surprisingly the data issues were not seen it:   What really is the key in the approach it is to properly set the Conditional Split Transformation. Visually it is: and specifically its SSIS Expression LEN([After CS Column 0]) > 1 The point is to employ the right Boolean expression (yes, the Conditional Split accepts only Boolean conditions). For the sake of this post I re-named the Output Name “No Empty Rows”, but by default it will be named Case 1 (remember to drag your first column into the expression area)! You can close your Conditional Split now. The next part will be crucial – consuming the output of our Conditional Split. Last step - #4: Add a Flat File Destination or any other one you need. Click on the Conditional Split and choose the green arrow to drop onto the target. When you do so make sure you choose the No Empty Rows output and NOT the Conditional Split Default Output. Make the necessary mappings. At this point your package must look like: As the last step will run our package to examine the produced output file. F5: and… it looks great!

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  • Educational, well-written FOSS projects to read, study or discuss

    - by Godot
    Before you say it: yes, this "question" has been asked other times. However, I could not fine many of such questions and not that easily, and those I found had similar results. What I'm trying to say that there are no comprehensive lists of well written Open Source projects, so I decided to set some requirements for the entries (one or possibly more): Idiomatic use of the language in which they are written The project should be lightweight. Not as in "a few kbs", as in "clean" and possibly following the UNIX philosophy, making an efficient use of resources and performing its duty and nothing more. No code bloat, most importantly. Projects like Firefox and GNOME wouldn't qualify, for example. Minimal reliance on external, non-standard libraries, with exceptions for some common FOSS libraries (curses, Xlib, OpenGL and possibly "usual suspects" like gtk+, webkit and Boost). Reliance on well-written libraries is welcome. No reliance on proprietary software - for obvious reasons (programs that rely on XNA, DirectX, Cocoa and similar, for example). Well-documented code is welcome. Include link to web interfaces to their repositories if possible. Here are some sample projects that often pop up in these threads: Operating Systems Plan 9 from Bell Labs: More or less, the official "sequel" to UNIX. Written in C by the same people who invented C! NetBSD: The most portable BSD implementation, written in C and also a good example of portable and organized code. Network and Databases Sqlite: Extremely lightweight and extremely efficient, one of the best pieces of C software I've seen. Count the lines yourself! Lighttpd: A small but pretty reliable web server written in C. Programming languages and VMs Lua: extremely lightweight multi-paradigm programming language. Written in C. Tiny C Compiler: Really tiny C compiler. Not really comparable to GCC or Clang but does its job. PyPy: A Python implementation written in Python. Pharo: OK, I admit it, I'm not really a Smalltalk expert but Pharo is a fork of Squeak and looked rather interesting. Stackless Python - An implementation of Python that doesn't rely on the C call stack - written in C (with some parts in Python) Games and 3D: Angband: One of the most accessible roguelike codebases around here, written in C. Ogre3D: Cross-platform 3D engine. Gets bloated if you don't skip the platform-specific implementation code, otherwise is a pretty solid example of good C++ OO. Simon Tatham's Portable Puzzle Collection: Title says it all. Other - dwm: Lightweight window manager. Written in C. Emulation and Reverse Engineering - Bochs: x86 emulator, written in C++ and tiny enough. - MAME: If you want to see C at one of its lowest levels, MAME is for you. May not be as clean as the other projects but it can teach you A LOT. Before you ask: I didn't mention Linux because it has become quite bloated in the last few years, Linus has also confirmed it. Nonetheless, it'd be a great educational read the same, even if for other reasons. Same for GCC. Feel free to edit or wikify my post. I hope you won't lock my question, I'm only trying to organize a little community effort for the good of all those people who want to enhance their coding skills.

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  • Consolidation in a Database Cloud

    - by B R Clouse
    Consolidation of multiple databases onto a shared infrastructure is the next step after Standardization.  The potential consolidation density is a function of the extent to which the infrastructure is shared.  The three models provide increasing degrees of sharing: Server: each database is deployed in a dedicated VM. Hardware is shared, but most of the software infrastructure is not. Standardization is often applied incompletely since operating environments can be moved as-is onto the shared platform. The potential for VM sprawl is an additional downside. Database: multiple database instances are deployed on a shared software / hardware infrastructure. This model is very efficient and easily implemented with the features in the Oracle Database and supporting products. Many customers have moved to this model and achieved significant, measurable benefits. Schema: multiple schemas are deployed within a single database instance. The most efficient model, it places constraints on the environment. Usually this model will be implemented only by customers deploying their own applications.  (Note that a single deployment can combine Database and Schema consolidations.) Customer value: lower costs, better system utilization In this phase of the maturity model, under-utilized hardware can be used to host more workloads, or retired and those workloads migrated to consolidation platforms. Customers benefit from higher utilization of the hardware resources, resulting in reduced data center floor space, and lower power and cooling costs. And, the OpEx savings from Standardization are multiplied, since there are fewer physical components (both hardware and software) to manage. Customer value: higher productivity The OpEx benefits from Standardization are compounded since not only are there fewer types of things to manage, now there are fewer entities to manage. In this phase, customers discover that their IT staff has time to move away from "day-to-day" tasks and start investing in higher value activities. Database users benefit from consolidating onto shared infrastructures by relieving themselves of the requirement to maintain their own dedicated servers. Also, if the shared infrastructure offers capabilities such as High Availability / Disaster Recovery, which are often beyond the budget and skillset of a standalone database environment, then moving to the consolidation platform can provide access to those capabilities, resulting in less downtime. Capabilities / Characteristics In this phase, customers will typically deploy fixed-size clusters and consolidate on a cluster until that cluster is deemed "full," at which point a new cluster is built. Customers will define one or a few cluster architectures that are used wherever possible; occasionally there may be deployments which must be handled as exceptions. The "full" policy may be based on number of databases deployed on the cluster, or observed peak workload, etc. IT will own the provisioning of new databases on a cluster, making the decision of when and where to place new workloads. Resources may be managed dynamically, e.g., as a priority workload increases, it may be given more CPU and memory to handle the spike. Users will be charged at a fixed, relatively coarse level; or in some cases, no charging will be applied. Activities / Tasks Oracle offers several tools to plan a successful consolidation. Real Application Testing (RAT) has a feature to help plan and validate database consolidations. Enterprise Manager 12c's Cloud Management Pack for Database includes a planning module. Looking ahead, customers should start planning for the Services phase by defining the Service Catalog that will be made available for database services.

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  • On a BPM Mission with Process Accelerators. Part 1: BPM as an ATV

    - by Cesare Rotundo
    Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} Part 1: BPM as an ATV It’s always exciting to talk to customers that are in the middle of a BPM transformational journey. Their thirst for new processes to improve with BPM makes them explorers in a landscape of opportunities. They have discovered that with BPM the can “go places” they couldn’t reach before. In a way, learning how to generate value with BPM is like adopting a new mean of transportation. Apps are like regular cars: very efficient, but to be used on paved roads: the road/process has been traced, and there are fixed paths to follow to get from “opportunity to quote” or from “quote to cash”. Getting off the road is risky, and laying down new asphalt is slow and expensive. Custom development is like running: you can go virtually anywhere, following any path you like, yet it’s slow, and a lot of sweat. BPM allows you to go “off the beaten path” laid out by packaged apps, yet make fast progress compared to custom development. BPM is therefore more like an All-Terrain Vehicle (ATV): less efficient than a car, but much faster than running, with a powerful enough engine that can get you places. The similarities between BPM and ATVs don’t stop here: you must learn to ride it even if you already know how to drive a car; you can reach places but figuring out the path to your destination is harder. Ultimately, with BPM as with an ATV, you reach places that you thought you could never reach, and you discover new destinations that provide great benefit to you … and that you didn’t even know existed! That’s where the sense of accomplishment that we heard from our BPM customers comes from, as well as the desire to share their experience, or even, as in the case of a County, the willingness to contribute their BPM solutions to help other agencies that face the same challenges. The question we wanted to answer is how can we teach organizations to drive ATV/BPM, thus leading them to deeper success with BPM, while increasing their awareness of the potential for reaching new targets, and finally equip them with the right tools. Like with ATVs, getting from point A to point B is more of a work of art than cruising on the highway by car. There is a lot we can do: after all many sought after destinations are common: someone else has been on the same path before. If only you could learn from their experience …

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  • How to restore/change Alt+Tab behaviour/ram usage and a few other things after Ubuntu upgrade from 11.04 to 11.10?

    - by fiktor
    I use Ubuntu for programming. I recently updated it from 11.04 to 11.10. There are some things I don't like in the new version of Unity desktop interface. I don't actually know if it is hard to restore previous behavior or not, and if it is not, where should I look to do that. I know a bit of programming, but I really don't know much about Linux settings. I used to have 3-6 terminal windows and switch between them with Alt+Tab and Shift+Alt+Tab. I liked half-transparent terminal windows, since with them I could open web-page with some instruction in Firefox, press Alt+Tab and type commands in a console window, being able to recognize text on a web-page under it. Now I have problems with my usual work-style because of the following. List of "negative" changes Alt+Tab shows just one icon for all console windows. When I wait some time, it, however, shows all windows, but I don't like to wait. I prefer to remember order of windows and press Alt+Tab as many times as I need to switch to the right window. Alt+Shift+Tab to switch in reverse order doesn't work now. Console windows are not transparent any more. When I don't wait, and switch to this icon, it shows all console windows altogether. So even if they were transparent, I wouldn't be able to see anything below them (I can read something only from the window, which is directly under current one, not a few levels under). When I run a few console windows in Unity I had 740Mb used on Ubuntu 11.04, but I have 1050Mb now. The question is how to make it back to 750-. I really need my memory, since I use my computer to work with 1512Mb of data and I try to save every 10Mb possible (if it doesn't take too much of machine and, more importantly, my time). When I press "The Super key" I have a field to type the name of the program I want to run. But now it sometimes shows this field, but when I'm trying to type nothing happens. Probably, focus is not on the right field. I don't really mean to restore exactly the same behavior, but I want to make my work in Ubuntu 11.10 efficient (at least as efficient as in Ubuntu 11.04). I would be happy if there are some ways to accomplish that. What have I tried I have installed CompizConfig Settings Manager. I have read this question. However enabling "Static Application Switcher" makes Alt+Tab crazy: after enabling it It says about key-binding conflicts with "Ubuntu Unity Plugin"; "Alt+Tab" switching doesn't change, but "Shift+Alt+Tab" now works and shows all windows; Memory usage increases. I have tried turning off Ubuntu Unity Plugin, but this doesn't seem right thing to do, since it seems to turn off all menus, a lot of keystrokes and app-launcher, which usually activates with "The Super key". I have found, that window transparency can be enabled by "Opacity, Brightness and Saturation" plugin from Accessibility. However I don't know if enabling it is the right thing to do (at least it increases memory usage). Update: everything solved but #3: see my own answer below. I have made a separate question about issue #3 (transparency).

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  • SQL Server Management Studio – tips for improving the TSQL coding process

    - by kristof
    I used to work in a place where a common practice was to use Pair Programming. I remember how many small things we could learn from each other when working together on the code. Picking up new shortcuts, code snippets etc. with time significantly improved our efficiency of writing code. Since I started working with SQL Server I have been left on my own. The best habits I would normally pick from working together with other people which I cannot do now. So here is the question: What are you tips on efficiently writing TSQL code using SQL Server Management Studio? Please keep the tips to 2 – 3 things/shortcuts that you think improve you speed of coding Please stay within the scope of TSQL and SQL Server Management Studio 2005/2008 If the feature is specific to the version of Management Studio please indicate: e.g. “Works with SQL Server 2008 only" Thanks EDIT: I am afraid that I could have been misunderstood by some of you. I am not looking for tips for writing efficient TSQL code but rather for advice on how to efficiently use Management Studio to speed up the coding process itself. The type of answers that I am looking for are: use of templates, keyboard-shortcuts, use of IntelliSense plugins etc. Basically those little things that make the coding experience a bit more efficient and pleasant. Thanks again

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  • Creating a multi-step process with mysql and php

    - by Paul Atkins
    Hi, I am working on a script which allows users to create a stepped process. The steps will consist of sending visitors to urls where they will fill out a form then be directed to the next step the user has created. Each user can create as many steps as they wish and the url for each step will be unique. I am not sure if I am doing this in the correct/most efficient way so I have a few questions about this. Before I begin here is a simple version of my table structure: step_id user_id step_url step_order 1 1 example.com?step=1 1 2 2 test.com?step=1 1 3 1 example.com?step=3 2 A visitor will be directed to step_url: example.com?step=1 by user_id: 1 On this page there will be a form which contains a hidden field with the value of the step_id like this: <input type="hidden" name="step_id" value="1"> Once the visitor has filled out this form it will be processed by my script at a url similar to: http://mysite.com/form-process.php Once the form has been submitted I then need to direct the visitor to the next step my user has created. I would currently do this using code similar to this: SELECT step_url FROM table WHERE step_order='$current_step_order'+1 Here are my questions about this: Is this the best most efficient way to accomplish this? Or is there a better way? As the step_id column is auto increment...how would I increment the order column by 1 each time a user inserts a new step? Thanks for taking the time to read this. Paul

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  • What are good NoSQL and non-relational database solutions for audit/logging database

    - by Juha Syrjälä
    What would be suitable database for following? I am especially interested about your experiences with non-relational NoSQL systems. Are they any good for this kind of usage, which system you have used and would recommend, or should I go with normal relational database (DB2)? I need to gather audit trail/logging type information from bunch of sources to a centralized server where I could generate reports efficiently and examine what is happening in the system. Typically a audit/logging event would consist always of some mandatory fields, for example globally unique id (some how generated by program that generated this event) timestamp event type (i.e. user logged in, error happened etc) some information about source (server1, server2) Additionally the event could contain 0-N key-value pairs, where value might be up to few kilobytes of text. It must run on Linux server It should work with high amount of data (100GB for example) it should support some kind of efficient full text search It should allow concurrent reading and writing It should be flexible to add new event types and add/remove key-value pairs to new events. Flexible=no changes should be required to database schema, application generating the events can just add new event types/new fields as needed. it should be efficient to make queries against database. For reporting and exploring what happened. For example: How many events with type=X occurred in some time period. Get all events where field A has value Y. Get all events with type X and field A has value 1 and field B is not 2 and event occurred in last 24h

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  • Choosing random numbers efficiently

    - by Frederik Wordenskjold
    I have a method, which uses random samples to approximate a calculation. This method is called millions of times, so its very important that the process of choosing the random numbers is efficient. I'm not sure how fast javas Random().nextInt really are, but my program does not seem to benefit as much as I would like it too. When choosing the random numbers, I do the following (in semi pseudo-code): // Repeat this 300000 times Set set = new Set(); while(set.length != 5) set.add(randomNumber(MIN,MAX)); Now, this obviously has a bad worst-case running time, as the random-function in theory can add duplicated numbers for an eternity, thus staying in the while-loop forever. However, the numbers are chosen from {0..45}, so a duplicated value is for the most part unlikely. When I use the above method, its only 40% faster than my other method, which does not approximate, but yields the correct result. This is ran ~ 1 million times, so I was expecting this new method to be at least 50% faster. Do you have any suggestions for a faster method? Or maybe you know of a more efficient way of generation a set of random numbers.

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  • What's are the best readings to start using WPF instead of WinForms?

    - by Ivan
    Keeping in mind what CannibalSmith once said - "All the answers are saying "WPF is different". That's a huge understatement. You not only have to learn lots of new stuff - you must forget everything you've learned from Forms. It's a completely new way of doing UI." .. and having many years of experience with visual Windows desktop applications development (VB6, Borland C++ Builder VCL, WinForms) (which is hard to forget), how do I quickly move to developing to say well-formed WPF applications with Visual Studio? I don't need boozy-woozy graphics to give my app look and feel of a Hollywood blockbuster or a million dollar pyjamas. I always loved tidiness of standard Windows common controls and UI design guidelines, end even more I enjoyed them under Vista Glass Aero Graphite sauce. I am perfectly satisfied with WinForms but I want to my applications to be built of the most efficient and up-to-date standard technologies and architectured according to the most efficient and flexible patterns of today and tomorrow, leveraging interface-based integration and functionality reuse and to take all advantages of modern hardware and APIs to maximize performance, usability, reliability, maintainability, extensibility, etc. I very much like the idea of separating view, logic and data, letting a view to take all advantages of the platform (may it run as a web browser applet on a thin client or as a desktop application on a PC with a latest GPU), letting logic be reused, parallelized and seamlessly evolve, storing data in a well structured format in a right place. But... while moving from VB6 to Borland C++ Builder was very easy (no books/tutorials needed to turn it on and start working) (assuming I already knew C++), moving from BCB to WinForms was the same seamless, it does not seem any obvious to me how to do with WPF. So how do I best convert myself from a WinForms developer into a right-way thinking and doing WPF developer?

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  • "Work stealing" vs. "Work shrugging (tm)"?

    - by John
    Why is it that I can find lots of information on "work stealing" and nothing on a "work shrugging(tm)" as a load-balancing strategy? I am surprised because work-stealing seems to me to have an inherent weakness when implementating efficient fine-grained load-balancing. Vis:- Relying on consumer processors to implement distribution (by actively stealing) begs the question of what these processors do when they find no work? None of the work-stealing references and implementations I have come across so far address this issue satisfactorarily for me. They either:- 1) Manage not to disclose what they do with idle processors! [Cilk] (?anyone know?) 2) Have all idle processors sleep and wake periodically and scatter messages to the four winds to see if any work has arrived [e.g. JAWS] (= way too latent & inefficient for me). 3) Assume that it is acceptable to have processors "spinning" looking for work ( = non-starter for me!) Unless anyone thinks there is a solution for this I will move on to consider a "Work Shrugging(tm)" strategy. Having the task-producing processor distribute excess load seems to me inherently capable of a much more efficient implementation. However a quick google didn't show up anything under the heading of "Work Shrugging" so any pointers to prior-art would be welcome. tx Tags I would have added if I was allowed to [work-stealing]

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  • C++ .NET DLL vs C# Managed Code ? (File Encrypting AES-128+XTS)

    - by Ranhiru
    I need to create a Windows Mobile Application (WinMo 6.x - C#) which is used to encrypt/decrypt files. However it is my duty to write the encryption algorithm which is AES-128 along with XTS as the mode of operation. RijndaelManaged just doesn't cut it :( Very much slower than DES and 3DES CryptoServiceProviders :O I know it all depends on how good I am at writing the algorithm in the most efficient way. (And yes I my self have to write it from scratch but i can take a look @ other implementations) Nevertheless, does writing a C++ .NET DLL to create the encryption/decryption algorithm + all the file handling and using it from C# have a significant performance advantage OVER writing the encryption algorithm + file handling in completely managed C# code? If I use C++ .NET to create the encryption algorithm, should I use MFC Smart Device DLL or ATL? What is the difference and is there any impact on which one I choose? And can i just add a reference to the C++ DLL from C# or should I use P/Invoke? I am fairly competent with C# than C++ but performance plays a major role as I have convinced my lecturers that AES is a very efficient cryptographic algorithm for resource constrained devices. Thanx a bunch :)

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  • How to keep only duplicates efficiently?

    - by Marc Eaddy
    Given an STL vector, I'd like an algorithm that outputs only the duplicates in sorted order, e.g., INPUT : { 4, 4, 1, 2, 3, 2, 3 } OUTPUT: { 2, 3, 4 } The algorithm is trivial, but the goal is to make it as efficient as std::unique(). My naive implementation modifies the container in-place: My naive implementation: void keep_duplicates(vector<int>* pv) { // Sort (in-place) so we can find duplicates in linear time sort(pv->begin(), pv->end()); vector<int>::iterator it_start = pv->begin(); while (it_start != pv->end()) { size_t nKeep = 0; // Find the next different element vector<int>::iterator it_stop = it_start + 1; while (it_stop != pv->end() && *it_start == *it_stop) { nKeep = 1; // This gets set redundantly ++it_stop; } // If the element is a duplicate, keep only the first one (nKeep=1). // Otherwise, the element is not duplicated so erase it (nKeep=0). it_start = pv->erase(it_start + nKeep, it_stop); } } If you can make this more efficient, elegant, or general, please let me know. For example, a custom sorting algorithm, or copy elements in the 2nd loop to eliminate the erase() call.

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  • Database migration pattern for Java?

    - by Eno
    Im working on some database migration code in Java. Im also using a factory pattern so I can use different kinds of databases. And each kind of database im using implements a common interface. What I would like to do is have a migration check that is internal to the class and runs some database schema update code automatically. The actual update is pretty straight forward (I check schema version in a table and compare against a constant in my app to decide whether to migrate or not and between which versions of schema). To make this automatic I was thinking the test should live inside (or be called from) the constructor. OK, fair enough, that's simple enough. My problem is that I dont want the test to run every single time I instantiate a database object (it runs a query so having it run on every construction is not efficient). So maybe this should be a class static method? I guess my question is, what is a good design pattern for this type of problem? There ought to be a clean way to ensure the migration test runs only once OR is super-efficient.

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