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  • posmax: like argmax but gives the position(s) of the element x for which f[x] is maximal

    - by dreeves
    Mathematica has a built-in function ArgMax for functions over infinite domains, based on the standard mathematical definition. The analog for finite domains is a handy utility function. Given a function and a list (call it the domain of the function), return the element(s) of the list that maximize the function. Here's an example of finite argmax in action: http://stackoverflow.com/questions/471029/canonicalize-nfl-team-names/472213#472213 And here's my implementation of it (along with argmin for good measure): (* argmax[f, domain] returns the element of domain for which f of that element is maximal -- breaks ties in favor of first occurrence. *) SetAttributes[{argmax, argmin}, HoldFirst]; argmax[f_, dom_List] := Fold[If[f[#1]>=f[#2], #1, #2]&, First[dom], Rest[dom]] argmin[f_, dom_List] := argmax[-f[#]&, dom] First, is that the most efficient way to implement argmax? What if you want the list of all maximal elements instead of just the first one? Second, how about the related function posmax that, instead of returning the maximal element(s), returns the position(s) of the maximal elements?

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  • What logic operator to use, as3?

    - by VideoDnd
    What operator or expression can I use that will fire on every number, including zero? I want a logic operator that will fire with ever number it receives. My animations pause at zero. This skips on zero if (numberThing> 0); This skips on 9 if (numberThing>> 0); This jitters 'fires quickly and goes back on count' if (numberThing== 0); EXPLANATION I'm catching split string values in a logic function, and feeding them to a series of IF, ELSE IF statements. I'm using this with a timer, so I can measure the discrepency. CODE • I GET VALUES FROM TIMER • STRING GOES TO TEXTFIELD 'substr' • NUMBER TRIGGERS TWEENS 'parseInt' • Goes to series of IF and ELSE IF statements

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  • Why better isolation level means better performance in SQL Server

    - by Oleg Zhylin
    When measuring performance on my query I came up with a dependency between isolation level and elapsed time that was surprising to me READUNCOMMITTED - 409024 READCOMMITTED - 368021 REPEATABLEREAD - 358019 SERIALIZABLE - 348019 Left column is table hint, and the right column is elapsed time in microseconds (sys.dm_exec_query_stats.total_elapsed_time). Why better isolation level gives better performance? This is a development machine and no concurrency whatsoever happens. I would expect READUNCOMMITTED to be the fasted due to less locking overhead. Update: I did measure this with DBCC DROPCLEANBUFFERS DBCC FREEPROCCACHE issued and Profiler confirms there're no cache hits happening. Update2: The query in question is an OLAP one and we need to run it as fast as possible. Closing the production server from outside world to get the computation done is not out of question if this gives performance benefits.

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  • Measuring device drivers CPU/IO utilization caused by my program

    - by Lior Kogan
    Sometimes code can utilize device drivers up to the point where the system is unresponsive. Lately I've optimized a WIN32/VC++ code which made the system almost unresponsive. The CPU usage, however, was very low. The reason was 1000's of creations and destruction of GDI objects (pens, brushes, etc.). Once I refactored the code to create all objects only once - the system became responsive again. This leads me to the question: Is there a way to measure CPU/IO usage of device drivers (GPU/disk/etc) for a given program / function / line of code?

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  • how random is Math.random() in java across different jvms or different machines

    - by user881480
    I have a large distributed program across many different physical servers, each program spawns many threads, each thread use Math.random() in its operations to draw a piece from many common resource pools. The goal is to utilize the pools evenly across all operations. Sometimes, it doesn't appear so random by looking at a snapshot on a resource pool to see which pieces it's getting at that instant (it might actually be, but it's hard to measure and find out for sure). Is there something that's better than Math.random() and performs just as good (not much worse at least)?

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  • Best Pratice to Implement Secure Remember Me

    - by Yan Cheng CHEOK
    Sometimes, I came across certain web development framework which doesn't provide authentication feature as in Authenication ASP.NET I was wondering what is the security measure needs to be considered, when implementing "Remember Me" login feature, by hand coding? Here are the things I usually did. 1) Store the user name in cookie. The user name are not encrypted. 2) Store a secret key in cookie. The secret key is generated using one way function based on user name. The server will verify secret key against user name, to ensure this user name is not being changed. 3) Use HttpOnly in cookie. http://www.codinghorror.com/blog/2008/08/protecting-your-cookies-httponly.html Any things else I could miss out, which could possible lead a security hole.

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  • Ngram IDF smoothing

    - by adi92
    I am trying to use IDF scores to find interesting phrases in my pretty huge corpus of documents. I basically need something like Amazon's Statistically Improbable Phrases, i.e. phrases that distinguish a document from all the others The problem that I am running into is that some (3,4)-grams in my data which have super-high idf actually consist of component unigrams and bigrams which have really low idf.. For example, "you've never tried" has a very high idf, while each of the component unigrams have very low idf.. I need to come up with a function that can take in document frequencies of an n-gram and all its component (n-k)-grams and return a more meaningful measure of how much this phrase will distinguish the parent document from the rest. If I were dealing with probabilities, I would try interpolation or backoff models.. I am not sure what assumptions/intuitions those models leverage to perform well, and so how well they would do for IDF scores. Anybody has any better ideas?

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  • What would you recommend for a large-scale Java data grid technology: Terracotta, GigaSpaces, Cohere

    - by cliff.meyers
    I've been reading up on so-called "data grid" solutions for the Java platform including Terracotta, GigaSpaces and Coherence. I was wondering if anyone has real-world experience working any of these tools and could share their experience. I'm also really curious to know what scale of deployment people have worked with: are we talking 2-4 node clusters or have you worked with anything significantly larger than that? I'm attracted to Terracotta because of its "drop in" support for Hibernate and Spring, both of which we use heavily. I also like the idea of how it decorates bytecode based on configuration and doesn't require you to program against a "grid API." I'm not aware of any advantages to tools which use the approach of an explicit API but would love to hear about them if they do in fact exist. :) I've also spent time reading about memcached but am more interested in hearing feedback on these three specific solutions. I would be curious to hear how they measure up against memcached in the event someone has used both.

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  • Combining javascripts into a single file

    - by toomanyairmiles
    Having read up recently on yahoo's web optimisation tips and using YSlow I've implemented a few of their ideas on one of my sites http://www.gwynfryncottages.com you can see the file here http://www.gwynfryncottages.com/js/gw-custom.js. While this technique seems to work perfectly on most occasions, and really does speed up the site, I do notice a significantly higher number of errors where the javascripts don't load or don't load completely while I'm working on the site so three questions:- is combining scripts this way a good idea at all in terms of reliablity? is there any way to measure the number of errors? is there any way to 'pre-load' the javascript or ensure that the number of loading errors is reduced?

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  • What Are Basic Tools For A New Project?

    - by Morgan Cheng
    For a long time, I thought that to start a new project we only need 3 basic tools. 1) A Build System (e.g. Maven & CruiseControl) 2) A Version Control System (e.g. CVS & SVN & GIT) 3) A Bug Tracking System (e.g. Bugzilla) Yesterday, a senior guy told me that we need at least one thing more. That is KPI(Key Performance Index). Without KPI, it is impossible to measure whether the project is progressing well or not. KPI is kind of SOFT tool compared to Maven/SVN/Bugzilla. I believe since I missed SOFT tools, there must be some other kind of tools I missed. So, anybody get some ideas what other basic tools necessary for a new project?

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  • Struts/JSP/J2EE performance and memory profiling and issues

    - by Berlin Brown
    We are using Struts and having performance issues. And making heavy use of jsp includes, tiles, EL expressions. I am sure this is eating up a lot of memory and processing time. What are some approaches to profile the JSP page? What tools could I use? What should I look for when profiling? I have seen the code generated JSP Java Servlet Code and I see the bottlenecks but would rather measure it more accurately. This is under JDK1.5 and IBM Websphere 6.1 (RAD7)

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  • How can I clip strings in Java2D and add ... in the end?

    - by Jonas
    I'm trying to print Invoices in a Java Swing applications. I do that by extending Printable and implement the method public int print(Graphics g, PageFormat pf, int page). I would like to draw strings in columns, and when the string is to long I want to clip it and let it end with "...". How can I measure the string and clip it at the right position? Some of my code: Font headline = new Font("Times New Roman", Font.BOLD, 14); g2d.setFont(headline); FontMetrics metrics = g2d.getFontMetrics(headline); g2d.drawString(myString, 0, 20); I.e How can I limit myString to be max 120px? I could use metrics.stringWidth(myString), but I don't get the position where I have to clip the string. Expected results could be: A longer string that exc... A shorter string. Another long string, but OK

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  • How can I extend a LinkButton to allow HTML text in Flex?

    - by John Isaacks
    I am feeding the label to my LinkButton directly from a string I receive from a Google API that puts html to format the label. I want to extend linkbutton to allow this. I wrote a class myself to allow html text for the label and that aspect of it works but now the background that appears when you hover is way too big. I tried to override measure() to fix this but I didn't have a clue how. Here is the class I wrote: package com.kranichs.components { import mx.controls.LinkButton; public class HTMLLinkButton extends LinkButton { protected var _isHTML:Boolean; public function HTMLLinkButton() { super(); } [Bindable] public function set isHTML(value:Boolean):void { _isHTML = value; } public function get isHTML():Boolean { return _isHTML; } override protected function updateDisplayList(unscaledWidth:Number, unscaledHeight:Number):void { super.updateDisplayList(unscaledWidth, unscaledHeight); if(_isHTML) { textField.htmlText = label; } } } }

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  • algorithm for checking addresses for matches?

    - by user151841
    I'm working on a survey program where people will be given promotional considerations the first time they fill out a survey. In a lot of scenarios, the only way we can stop people from cheating the system and getting a promotion they don't deserve is to check street address strings against each other. I was looking at using levenshtein distance to give me a number to measure similarity, and consider those below a certain threshold a duplicate. However, if someone were looking to game the system, they could easily write "S 5th St" instead of "South Fifth Street", and levenshtein would consider those strings to be very different. So then I was thinking to convert all strings to a 'standard address form' i.e. 'South' becomes 's', 'Fifth' becomes '5th', etc. Then I was thinking this is hopeless, and too much effort to get it working robustly. Is it? I'm working with PHP/MySql, so I have the limitations inherent in that system.

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  • Improve performance of website

    - by Vinodtiru
    Hi, I have designed a new web site. I have hosted it online. I want it to be of the best performance and load pages faster. This website is designed in php 5.0+ using codeigniter. This is using mysql as DB. I have images on it. I am using Nitobi grid for displaying set of records on page. The rest is everything normal page controls. As i am not so very experienced with website performance factors i would like to get suggestions and details on factors that can improve performance of website. Please let me know how i can improve my performance. Also please let me know if there are any ways to measure the performance of website and also any websites or tools to help test the performance. Any kind of help is appreciated. Thanks in advance. Thanks and Regards Vinod T.

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  • Monitor and Terminate Python script based on system resource use

    - by Vincent
    What is the "right" or "best" way to monitor the system resources a python script is using and terminate it if the resource use exceeds some predetermined values. In my case memory usage is of concern. I am not asking how to measure the system resource use although I am open to suggestions. As a simple example, let's assume I have a function that finds prime numbers less than some large number and adds them to a list based on some condition. I don't know ahead of time how many prime numbers will satisfy the condition so I what to be sure to terminate the function if I use up to much system memory (8gb lets say). I know that there are ways to monitor the size of python objects. What I don't know is the proper way to monitor the size of the list and exit is to just include a size test in the prime function loop and exit if it exceeds 8gb or if there is an "external" way to monitor and exit.

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  • Mahout Recommendations on Binary data

    - by Pranay Kumar
    Hi, I'm a newbie to mahout.My aim is to produce recommendations on binary user purchased data.So i applied item-item similarity model in computing top N recommendations for movie lens data assuming 1-3 ratings as a 0 and 4-5 ratings as a 1.Then i tried evaluating my recommendations with the ratings in the test-data but hardly there have been two or three matches from my top 20 recommendations to the top rated items in test data and no match for most users. So are my recommendations totally bad by nature or do i need to go for a different measure for evaluating my recommendations ? Please help me ! Thanks in advance. Pranay, 2nd yr ,UG student.

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  • Scrum metrics for quality

    - by zachary
    What is the best way to measure QA in scrum? We have members who typically test and they are measured against how many bugs they find. If they don't find any bugs then they are considered to be doing a bad job. However, it is my understanding that the developers and quality people are considered one in the same. I would think that they should be judged against the same metrics... not different metrics then the developers who may also be doing testing work... What is the best way to handle metrics for QA and should QA people have separate metrics from developers in scrum? Any documents or links someone can point me to in regards to this?

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  • How to verify a digital signature with openssl

    - by Aaron Carlino
    I'm using a thirdparty credit card processing service (Paybox) that, after a successful transaction, redirects back to the website with a signature in the URL as a security measure to prevent people from manipulating data. It's supposed to prove that the request originated from this service. So my success URL looks something like this: /success.php?signature=[HUGE HASH] I have no idea where to start with verifying this signature. This service does provide a public key, and I assume I need to create a private key, but I don't know much beyond that. I'm pretty good with linux, and I know I'll have to run some openssl commands. I'm writing the verification script in PHP, which also has native openssl() functions. If anyone could please push me in the right direction with some pseudo code, or even functional code, I'd be very grateful. Thanks.

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  • trouble accessing localhost from ie7 running on parallels (win xp) on mac os x

    - by Karl R
    I'm running the app engine devserver on localhost:8080, and want to access it from ie7 running on parallels. I've tried all of the tips here: http://stackoverflow.com/questions/61449/how-do-i-access-the-host-from-vmware-fusion And they seem like they should work, particularly accessing via the gateway ip address. I've also sudo ipfw add allow tcp from 8080 to 8089 for good measure. Still no dice. I can access the external internet from ie7. The connection settings on parallels are set to 'Shared networking'. I'm out of ideas.

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  • Algorithm for calculating definite integrals with bounds at infinity

    - by mbac32768
    Suppose I have an integral that's bounded on one (or both) end by (-)infinity. AFAICT, I can't analytically solve this problem, it takes brute force (e.g. using a Left Riemann Sum). I'm having trouble generalizing the algorithm so that it sets the proper subdivisions; I'll either do far too much work to calculate something trivial, or not do nearly enough and have huge aliasing errors. Answering in any language is cool, but maybe someone with better google-fu can end this quickly. :) Is what I'm looking for as impossible as trying to measure the British coastline?

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  • How to automate the finding of an M value along a route

    - by Heather Taylor
    Kirk Kuykendall had given a script example a few years back in an ESRI forum http://forums.esri.com/Thread.asp?c=93&f=996&t=88246&mc=4 as to how to find the M (measure) value of a point in a shapefile along a route when you clicked on the point. This is very handy, BUT..I have 1500 points that I need M values for. Is there a way to automate this type of thing? I need the M values for the points to create linear events on the route. Note: I am not a programmer, but have people who can help me out.

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  • mod_perl memory leak

    - by marghi
    Hello, I recently discovered that one of our sites has a memory leak in it, it's very strange because it happened all of the sudden. I've used GTop to measure the memory size per process and it tells me that the real value is somewhere around 65 MB (on the server) per request and and additional 5 MB shared. I tried preloading the modules in the startup.pl file a indicated in the performance tuning article for mod_perl. Nothing happened if fact the shared memory decreased down to 3.7 MB, in this situation I thought that my application is leaking memory do before any line of code got executed I measured the memory just to find out that the total value is in fact 64 MB, my questions are: Is there a default preallocation of memory for each process? Is there a configuration issue? Is mod_perl leaking memory ? Thank you very much.

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  • awk / sed script to remove text

    - by radman
    Hi, I am currently needed of way to programmatically remove some text from Makefiles that I am dealing with. Now the problem is that (for whatever reason) the makefiles are being generated with link commands of -l<full_path_to_library>/<library_name> when they should be generated with -l<library_name>. So what I need is a script to find all occurrences of -l/ and then remove up to and including the next /. Example of what I'm dealing with -l/home/user/path/to/boost/lib/boost_filesystem I need it to be -lboost_filesystem As could be imagined this is a stop gap measure until I fix the real problem (on the generation side) but in the meantime it would be a great help to me if this could work and I am not too good with my awk and sed. Thanks for any help.

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  • Why are gettimeofday() intervals occasionally negative?

    - by Andres Jaan Tack
    I have an experimental library whose performance I'm trying to measure. To do this, I've written the following: struct timeval begin; gettimeofday(&begin, NULL); { // Experiment! } struct timeval end; gettimeofday(&end, NULL); // Print the time it took! std::cout << "Time: " << 100000 * (end.tv_sec - begin.tv_sec) + (end.tv_usec - begin.tv_usec) << std::endl; Occasionally, my results include negative timings, some of which are nonsensical. For instance: Time: 226762 Time: 220222 Time: 210883 Time: -688976 What's going on?

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