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  • How do you measure latency in low-latency environments?

    - by Ajaxx
    Here's the setup... Your system is receiving a stream of data that contains discrete messages (usually between 32-128 bytes per message). As part of your processing pipeline, each message passes through two physically separate applications which exchange the data using a low-latency approach (such as messaging over UDP) or RDMA and finally to a client via the same mechanism. Assuming you can inject yourself at any level, including wire protocol analysis, what tools and/or techniques would you use to measure the latency of your system. As part of this, I'm assuming that every message that is delivered to the system results in a corresponding (though not equivalent) message being pushed through the system and delivered to the client. The only tool that I've seen on the market like this is TS-Associates TipOff. I'm sure that with the right access you could probably measure the same information using a wire analysis tool (ala wireshark) and the right dissectors, but is this the right approach or are there any commodity solutions that I can use?

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  • Pros and cons of ways of storing an unsigned int without an unsigned int data type

    - by fields
    I have values that are 64-bit unsigned ints, and I need to store them in mongodb, which has no unsigned int type. I see three main possibilities for storing them in other field types, and converting on going in and out: Using a signed int is probably easiest and most space efficient, but has the disadvantage that they're not human readable and if someone forgets to do the conversion, some of them will work, which may obscure errors. Raw binary is probably most difficult for inexperienced programmers to deal with, and also suffers from non-human-readability. A string representation is the least space efficient (~40 bytes in unicode vs 8 bytes per field), but then at least all of the possible values will map properly, and for querying only a conversion to string is required instead of a more complicated conversion. I need these values to be available from different platforms, so a single driver-specific solution isn't an option. Any major pros and cons I've missed? Which one would you use?

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  • Sorting By Multiple Conditions in Ruby

    - by viatropos
    I have a collection of Post objects and I want to be able to sort them based on these conditions: First, by category (news, events, labs, portfolio, etc.) Then by date, if date, or by position, if a specific index was set for it Some posts will have dates (news and events), others will have explicit positions (labs, and portfolio). I want to be able to call posts.sort!, so I've overridden <=>, but am looking for the most effective way of sorting by these conditions. Below is a pseudo method: def <=>(other) # first, everything is sorted into # smaller chunks by category self.category <=> other.category # then, per category, by date or position if self.date and other.date self.date <=> other.date else self.position <=> other.position end end It seems like I'd have to actually sort two separate times, rather than cramming everything into that one method. Something like sort_by_category, then sort!. What is the most ruby way to do this?

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  • How to tell the database type checking the file

    - by Click Ok
    My friend have a system to manage customers. The program per si is terrible, and my friend lost contact with the developers. The case is, now my friend lost the access to program (something that the developers say "locked to machine" so when moved to another pc, he lost the access to program and data. I get mission of to try to recover the database, migrating to another database, and create a cool program to my friend. Now I need to discover wich database was used by the developers. I know that the program was made using Visual Basic, because the MSVBVM60.DLL is required. There is some program to read the metadata in the .dat files and discover wich database was used?

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  • Segmenting a double array of labels

    - by Ami
    The Problem: I have a large double array populated with various labels. Each element (cell) in the double array contains a set of labels and some elements in the double array may be empty. I need an algorithm to cluster elements in the double array into discrete segments. A segment is defined as a set of pixels that are adjacent within the double array and one label that all those pixels in the segment have in common. (Diagonal adjacency doesn't count and I'm not clustering empty cells). |-------|-------|------| | Jane | Joe | | | Jack | Jane | | |-------|-------|------| | Jane | Jane | | | | Joe | | |-------|-------|------| | | Jack | Jane | | | Joe | | |-------|-------|------| In the above arrangement of labels distributed over nine elements, the largest cluster is the “Jane” cluster occupying the four upper left cells. What I've Considered: I've considered iterating through every label of every cell in the double array and testing to see if the cell-label combination under inspection can be associated with a preexisting segment. If the element under inspection cannot be associated with a preexisting segment it becomes the first member of a new segment. If the label/cell combination can be associated with a preexisting segment it associates. Of course, to make this method reasonable I'd have to implement an elaborate hashing system. I'd have to keep track of all the cell-label combinations that stand adjacent to preexisting segments and are in the path of the incrementing indices that are iterating through the double array. This hash method would avoid having to iterate through every pixel in every preexisting segment to find an adjacency. Why I Don't Like it: As is, the above algorithm doesn't take into consideration the case where an element in the double array can be associated with two unique segments, one in the horizontal direction and one in the vertical direction. To handle these cases properly, I would need to implement a test for this specific case and then implement a method that will both associate the element under inspection with a segment and then concatenate the two adjacent identical segments. On the whole, this method and the intricate hashing system that it would require feels very inelegant. Additionally, I really only care about finding the large segments in the double array and I'm much more concerned with the speed of this algorithm than with the accuracy of the segmentation, so I'm looking for a better way. I assume there is some stochastic method for doing this that I haven't thought of. Any suggestions?

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  • Modifying a model and texture mid-game code

    - by MicroPirate
    Just have a question for anyone out there who knows some sort of game engine pretty well. What I am trying to implement is some sort of script or code that will allow me to make a custom game character and textures mid-game. A few examples would be along the lines of changing facial expressions and body part positions in the game SecondLife. I don't really need a particular language, feel free to use your favorite, I'm just really looking for an example on how to go about this. Also I was wondering if there is anyway to combine textures for optimization; for example if i wanted to add a tattoo to a character midgame, is there any code that could combine his body texture and the tattoo texture into one texture to use (this way I can simply just render one texture per body.) Any tips would be appreciated, sorry if the question is a wee bit to vauge.

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  • what's a good way to synchronize a sql server 2008 database from a 2005 database automatically?

    - by Keith Nicholas
    Ok, the scenario is... two servers, on completely different parts of the internet. The sql 2008 database just needs to get data updates and schema changes. It doesn't need to send anything to the 2005 database. Basically just suck data and schema as efficiently as possible automatically as a scheduled task. The database is quite huge.... but the changes per day are probablly around 20/30 megabytes of data/ I can't run any of the inbuilt replication on the 2005 database. I've had a wee look at the Sync Framework, I think that might do what I want, but seems a bit painful and requires a bit of work to get going. I'm wondering if there is tooling out there to make this easier? or?? not quite sure what my options are.

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  • NumPy: how to quickly normalize many vectors?

    - by EOL
    How can a list of vectors be elegantly normalized, in NumPy? Here is an example that does not work: from numpy import * vectors = array([arange(10), arange(10)]) # All x's, then all y's norms = apply_along_axis(linalg.norm, 0, vectors) # Now, what I was expecting would work: print vectors.T / norms # vectors.T has 10 elements, as does norms, but this does not work The last operation yields "shape mismatch: objects cannot be broadcast to a single shape". How can the normalization of the 2D vectors in vectors be elegantly done, with NumPy? Edit: Why does the above not work while adding a dimension to norms does work (as per my answer below)?

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  • Which method should I use ?

    - by Ivan
    I want to do this exercise but I don't know exactly which method should I use for an exercise like this and what data will I use to test the algorithm. The driving distance between Perth and Adelaide is 1996 miles. On the average, the fuel consumption of a 2.0 litre 4 cylinder car is 8 litres per 100 kilometres. The fuel tank capacity of such a car is 60 litres. Design and implement a JAVA program that prompts for the fuel consumption and fuel tank capacity of the aforementioned car. The program then displays the minimum number of times the car’s fuel tank has to be filled up to drive from Perth to Adelaide. Note that 62 miles is equal to 100 kilometres. What data will you use to test that your algorithm works correctly?

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  • MongoDB Schema Design - Real-time Chat

    - by Nick
    I'm starting a project which I think will be particularly suited to MongoDB due to the speed and scalability it affords. The module I'm currently interested in is to do with real-time chat. If I was to do this in a traditional RDBMS I'd split it out into: Channel (A channel has many users) User (A user has one channel but many messages) Message (A message has a user) The the purpose of this use case, I'd like to assume that there will be typically 5 channels active at one time, each handling at most 5 messages per second. Specific queries that need to be fast: Fetch new messages (based on an bookmark, time stamp maybe, or an incrementing counter?) Post a message to a channel Verify that a user can post in a channel Bearing in mind that the document limit with MongoDB is 4mb, how would you go about designing the schema? What would yours look like? Are there any gotchas I should watch out for?

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  • Compressing three individual jpeg pics containing temporal redundancy?

    - by michael
    I am interfacing and embedded device with a camera module that returns a single jpeg compressed frame each time I trigger it. I would like to take three successive shots (approx 1 frame per 1/4 second) and further compress the images into a single file. The assumption here is that there is a lot of temporal redundancy, therefore lots of room for more compression across the three frames (compared to sending three separate jpeg images). I will be implementing the solution on an embedded device in C without any libraries and no OS. The camera will be taking pics in an area with very little movement (no visitors or screens in the background, maybe a tree with swaying branches), so I think my assumption about redundancy is pretty solid. When the file is finally viewed on a pc/mac, I don't mind having to write something to extract the three frames (so it can be a nonstandard cluge) So I guess the actual question is: What is the best way to compress these three images together given the fact that they are already in JPEG format (it is a possibly to convert back to a raw image, but if i dont have too...)

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  • Extremely slow insert from Delphi to Remote MySQL Database

    - by MarkRobinson
    Having a major hair-pulling issue with extremely slow inserts from Delphi 2010 to a remote MySQL 5.09 server. So far, I have tried: ADO using MySQL ODBC Driver Zeoslib v7 Alpha I have used batching and direct insert with ADO (using table access), and with Zeos I have used SQL insertion with a Query, then used Table direct mode and also cached updates Table mode using applyupdates and commit. Both technologies I have tried with compression on and off. So far I have seen a pretty much the same across the board 7.5 records per second!!! Now, I would from this point assume that the remote server is just slow, but the MySQL Workbench is amazingly fast, and the Migration toolkit managed the initial migration very quickly (to be honest, I don't recall how quickly - which kind of means that it was quick) I'm just about to try the MyDAC components as we already use SDAC (wish there was a multi-buy discount or that we'd chosen UniDAC instead now!) Any ideas?

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  • How is the Tomcat temp directory location defined?

    - by sdoca
    I am running Tomcat bundled with Liferay5.2.3 and use Eclipse 3.5 (Galileo) as my IDE. I set up my Tomcat server in Eclipse as per this blog entry: http://www.jroller.com/holy/entry/developing_portlets_for_liferay_in. If I start Tomcat via the Eclipse server config, Liferay/Tomcat uses my C:\Documents and Settings\user\Local Settings\Temp\ directory. However, if I start Tomcat directly using the startup.bat script, Liferay/Tomcat uses the Tomcat temp directory. I can't figure out if Eclipse, Liferay or Tomcat is deciding which temp directory to use or how to change it. I would prefer to use the Tomcat temp directory. I have this issue with both the Lifera/Tomcat bundles 5.5 and 6.0 (liferay-portal-tomcat-6.0-5.2.3.zip and liferay-portal-tomcat-5.5-5.2.3.zip). Anybody have any clues?

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  • SQL - How can I apply a "semi-unique" constraint?

    - by Erin Drummond
    Hi, I have a (simplified) table consisting of three columns: id INT PRIMARY KEY NOT NULL AUTO_INCREMENT, foreignID INT NOT NULL, name VARCHAR NOT NULL Basically, I would like to add a constraint (at the database level rather than at the application level) where it only possible for one unique 'name' to exist per foreignID. For example, given the data (id, foreignid, name): 1,1,Name1 2,1,Name2 3,1,Name3 4,2,Name1 5,2,Name2 I want the constraint to fail if the user tries to insert another 'Name3' under foreignId 1, but succeed if the user tries to insert 'Name3' under foreignId 2. For this reason I cannot simply make the whole column UNIQUE. I am having difficulty coming up with a SQL expression to achieve this, can anybody help me? Thanks

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  • What are the things I use every day programmed with?

    - by sub
    It isn't so interesting to find out what this text editor here or that IRC client there was programmed with, also it isn't really hard and neither are there really suprising things to come out. Wow so it was programmed in Python, I didn't expect that. What I'm asking is: What are the things that we daily see, use or generally need programmed with? To name a few (really only a few of those out there): My alarm clock It has many features so it would probably be hard programming it with assembler or whatever, so did they probably use a programming language? If yes, which? My electrical tooth brush The (stupid) board computer of my car. (6 years old, has few features but a red LED display showing me how cold/warm it is outside and how much gas I'm using up per hour at the moment) Those (old) plastic mini-mini computers with the LCD(?) displays that only had one game available on them: PacMan, tetris or so. I'm not directly thinking of this but it may be similar: Other, probably more interesting, things I didn't mention

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  • Subversion and project management web based super tool. Like Team Foundation Server but not TFS.

    - by Rob Stevenson-Leggett
    Hi, We're currently looking at an IT upgrade and I'm after recommendations for a tool which can do some or all of the following. SVN management (authz, web viewer, commit log, diff) Create template projects (1 click e.g. create me a microsite with this name in svn and give these people access) Reporting on code churn, time spent on tasks on a per project basis User story management Basically like Team Foundation Server but that integrates with SVN properly (reason for this - we have a wide range of skill sets and not everyone can use a TFS client). Is there a combination of Trac plugins + something that can create trac instances (a la Dreamhost's admin panel) that can acheive this. On a side note, does anyone have any experience of version controlling designery type files - e.g. PSDs, Illustrator files. Any advice at all appreciated. Cheers, Rob

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  • What are your build and release steps? When to increment build numbers?

    - by Ed
    I am having trouble defining and automating my build process despite simple requirements: Every build should have a unique build number. Every tagged release should be reproducible What I have: A C++, Red Hat Enterprise Linux 5.x, Subversion development environment. A build machine ( actually a virtual machine ) A version.h file with #defines for major, minor, and buildnumber. A script for incrementing the version.h buildnumber. A rpmbuild spec file that exports the tagged Subversion source, builds, and makes the rpm installer packages. Questions: Assuming multiple developers per project, when should the build number be incremented and version.h file be checked-in? The build machine? Some sort of Subversion hook? Pre-build or post-build? Thanks in advance for those willing to take the time to share their experience with build processes. -Ed Linux newbie. Former Windows C++/.NET developer.

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  • .NET MVC - Storing database result during single page result?

    - by ropstah
    Fairly simple issue which is solved in PHP by using a static variable. private static $pages; public function Pages() { if($pages == null) { $pages = new PageCollection(); $pages->findAll(); } } Everywhere in my code I use Pages()::someFindFunction() to make sure the results are fetched only once, and I use that same collection. I want the same in my .NET MVC application: use something like: <%=MySite.Pages.findById(1).Title%> In the code below, if I use a private variable, or if I use a public class with shared variables (doesn't matter) they are both persisted during the entire application. I want them to load the same way PHP does, once per request. Now where do I store the .NET equivalent of private static $pages, so that the code below works? //what to do with $pages?? Public Module MySite Public Function Pages() As PageCollection If $pages Is Nothing Then $pages.loadAll() End If Return $pages End Function End Module

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  • org.apache.http.impl.cookie.BasicClientCookie not serializable???

    - by Misha Koshelev
    Dear All: I am quite confused... I am reading here and BasicClientCookie clearly implements Serializable per JavaDoc: http://hc.apache.org/httpcomponents-client/httpclient/apidocs/org/apache/http/impl/cookie/BasicClientCookie.html However, my simple Groovy script: #!/usr/bin/env groovy @Grapes( @Grab(group='org.apache.httpcomponents', module='httpclient', version='4.0.1') ) import org.apache.http.impl.cookie.BasicClientCookie import java.io.File def cookie=new BasicClientCookie("name","value") println cookie instanceof Serializable def f=new File("/tmp/test") f.withObjectOutputStream() { oos-> oos.writeObject(cookie) } outputs: false Caught: java.io.NotSerializableException: org.apache.http.impl.cookie.BasicClientCookie at t$_run_closure1.doCall(t.groovy:12) at t.run(t.groovy:11) I have checked and I have no other versions of HttpClient anywhere in classpath (if I take Grapes statement out it cannot find file). Thank you! Misha Koshelev

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  • Storing UTF-8 XML using Word's CustomXMLPart or any other supported way

    - by wpfwannabe
    I am writing a Word add-in which is supposed to store some own XML data per document using Word object model and its CustomXMLPart. The problem I am now facing is the lack of IStream-like functionality for reading/writing XML to/from a CustomXMLPart. It only provides BSTR interface and I am puzzled how to handle UTF-8 XMLs with BSTRs. To my understanding an UTF-8 XML file should really never have to undergo this sort of Unicode conversion. I am not sure what to expect as a result here. Is there another way of using Word automation interfaces to store arbitrary custom information inside a DOCX file?

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  • organise javascript code based on page

    - by David
    Hi I am relatively new to javascript development. At the moment I have a single javascript file with lots of little misc bits of code that get called in different part of the website. For example I have an event handler for some google maps stuff that is only called on 1 single page, I have some validation stuff for my contact page etc etc. My question, is how best to organise this code - given that each page only requires very little code but its different and specific per page? Oh, I am using jquery if that makes a difference.

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  • Determining the magnitude of a certain frequency on the iPhone

    - by eagle
    I'm wondering what's the easiest/best way to determine the magnitude of a given frequency in a sound. It's my understanding that a FFT function will return the magnitudes of all frequencies in a signal. I'm wondering if there is any shortcut I could use if I'm only concerned about a specific frequency. I'll be using the iPhone mic to record the audio. My guess is that I'll be using the Audio Queue Services for recording since I don't need to record the audio to a file. I'm using SDK 4.0, so I can use any of the functions defined in the Accelerate framework (e.g. FFT functions) if needed. Update: I updated the question to be more clear as per Conrad's suggestion.

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  • XPages Extension Library - onShow event for xe:djxmHeading

    - by Martin Perrie
    I am trying to add an onShow event to a Mobile Page Heading as per p. 326 oF the XPages Extension Library book. My code is as follows :- <xe:djxmHeading id="djxmHeading1" back="All Areas" moveTo="byArea"> <xe:this.label><![CDATA[#{javascript:param.get("Rep")}]]></xe:this.label> <xp:this.onShow> <![CDATA[#{javascript:sessionScope.put("RepName", param.get("Rep"))}]]> </xp:this.onShow> </xe:djxmHeading> which looks similar to the example in the book. But I'm getting the following error: Unknown property this.onShow. It is not defined on tag xe:djxmHeading. Any ideas what I'm doing wrong? Thanks

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  • Hyperlinks to download files without stopping the current page load

    - by Evgeny
    I've got an ASP.NET page that takes a long time to download and returns partial results as it's loading (as per my previous question). On the page I have some links to download files, ie. the response headers contain "Content-Disposition: attachment", so that the browser doesn't navigate away from the page. However, if the user clicks one of these links while the page is still loading it stops loading - normal behaviour, but not what I want in this case. I can get around that by adding target=_"blank" to the links, but this momentarily opens a new window and the closes it again (once the browser realises it's an "attachment"). Is there any way to avoid having those links stop the current page load without this new window trick? JavaScript is OK.

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  • Download attachment issue with IE6-8 - non ssl

    - by Arun P Johny
    I'm facing an issue with file download with IE6-8 in non ssl environment. I've seen a lot of articles about the IE attachment download issue with ssl. As per the articles I tried to set the values of Pragma, Cache-Control headers, but still no luck with it. These are my response headers Cache-Control: private, max-age=5 Date: Tue, 25 May 2010 11:06:02 GMT Pragma: private Content-Length: 40492 Content-Type: application/pdf Content-Disposition: Attachment;Filename="file name.pdf" Server: Apache-Coyote/1.1 I've set the header values after going through some of these sites KB 812935 KB 316431 But these items are related to SSL. I've checked the response body and headers using fiddler, the response body is proper. I'm using window.open(url, "_blank") to download the file, if I change it to window.open(url, "_parent") or change the "Content-Disposition" to 'inline;Filename="file name.pdf"' it works fine. Please help me to solve this problem

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