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• what is order notation f(n)=O(g(n))?

  - by Lopa

  2 questions: question 1: under what circumstances would this[O(f(n))=O(k.f(n))] be the most appropriate form of time-complexity analysis? question 2: working from mathematical definition of O notation, show that O(f(n))=O(k.f(n)), for positive constant k.? My view: For the first one I think it is average case and worst case form of time-complexity. am i right? and what else do i write in that? for the second one I think we need to define the function mathematically, so is the answer something like because the multiplication by a constant just corresponds to a readjustment of value of the arbitrary constant 'k' in definition of O.

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• ZooKeeper and RabbitMQ/Qpid together - overkill or a good combination?

  - by Chris Sears

  Greetings, I'm evaluating some components for a multi-data center distributed system. We're going to be using message queues (via either RabbitMQ or Qpid) so agents can make asynchronous requests to other agents without worrying about addressing, routing, load balancing or retransmission. In many cases, the agents will be interacting with components that were not designed for highly concurrent access, so locking and cross-agent coordination will be needed to avoid race conditions. Also, we'd like the system to automatically respond to agent or data center failures. With the above use cases in mind, ZooKeeper seemed like it might be a good fit. But I'm wondering if trying to use both ZK and message queuing is overkill. It seems like what Zookeeper does could be accomplished by my own cluster manager using AMQP messaging, but that would be hard to get really right. On the other hand, I've seen some examples where ZooKeeper was used to implement message queuing, but I think RabbitMQ/Qpid are a more natural fit for that. Has anyone out there used a combination like this? Thanks in advance, -Chris

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• C# how to correctly dispose of an SmtpClient?

  - by JL

  VS 2010 code analysis reports the following: Warning 4 CA2000 : Microsoft.Reliability : In method 'Mailer.SendMessage()', object 'client' is not disposed along all exception paths. Call System.IDisposable.Dispose on object 'client' before all references to it are out of scope. My code is : public void SendMessage() { SmtpClient client = new SmtpClient(); client.Send(Message); client.Dispose(); DisposeAttachments(); } How should I correctly dispose of client? Update: to answer Jons question, here is the dispose attachments functionality: private void DisposeAttachments() { foreach (Attachment attachment in Message.Attachments) { attachment.Dispose(); } Message.Attachments.Dispose(); Message = null; }

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• Are there macro facility for Java or C#?

  - by h2g2java

  Macros are useful. Therefore, I occasionally bemoan the absence of macros in Java and C#. Macros allow me to force in-line but allow me the code-manageability of non-macro code. Is there any Java- or C#-based project/product somewhere out there that effectively allow macros or specifying in-line expansion. I am thinking of something like @macro public void hello(int x){ ... } or when I call a method, an @inline annotation preceding the call would effect the called-method to be in-lined. or, should I need to know that I should just trust the compiler to make the best the decision for me that at the best of its analysis it might in-line a call. I hope this question will not lead to debating the pro/cons/usefulness of macros.

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• Creating a "less"-like console pager interface for pysqlite3 database

  - by Eric

  I would like to add some interactive capability to a python CLI application I've writen that stores data in a SQLite3 database. Currently, my app reads-in a certain type of file, parses and analyzes, puts the analysis data into the db, and spits the formatted records to stdout (which I generally pipe to a file). There are on-the-order-of a million records in this file. Ideally, I would like to eliminate that text file situation altogether and just loop after that "parse and analyze" part, displaying a screen's worth of records, and allowing the user to page through them and enter some commands that will edit the records. The backend part I know how to do. Can anyone suggest a good starting point for creating that pager frontend either directly in the console (like the pager "less"), through ncurses, or some other system?

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• NLB and Host Header Value

  - by Hafeez

  Background: We are using MOSS 2007 in farm configuration, 2 WFE, 1 Indexer and SQL Server. MS NLB is used for load balancing. Host header value mapped to Virtual IP of Cluster in DNS, is used while creating the web applications in MOSS and all are sharing port 80. Problem: When client tries to access the web application that are configured with host header values. Both of WFEs Hangs for 5 minutes, they stop responding to ping and browser shows 'Page not found'. In the Application Log on the WFE, this error is registered "provider: TCP Provider, error: 0 - The semaphore timeout period has expired". Interestingly, the web application with no host header value and hosted on different ports is working correctly. Any clue to solve this problem will be helpful. Thks. Hafeez

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• How can I loop through variables in SPSS? I want to avoid code duplication.

  - by chucknelson

  Is there a "native" SPSS way to loop through some variable names? All I want to do is take a list of variables (that I define) and run the same procedure for them: pseudo-code - not really a good example, but gets the point across... for i in varlist['a','b','c'] do FREQUENCIES VARIABLES=varlist[i] / ORDER=ANALYSIS. end I've noticed that people seem to just use R or Python SPSS plugins to achieve this basic array functionality, but I don't know how soon I can get those configured (if ever) on my installation of SPSS. SPSS has to have some native way to do this...right?

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• What is the difference between Multiple R-squared and Adjusted R-squared in a single-variate least s

  - by fmark

  Could someone explain to the statistically naive what the difference between Multiple R-squared and Adjusted R-squared is? I am doing a single-variate regression analysis as follows: v.lm <- lm(epm ~ n_days, data=v) print(summary(v.lm)) Results: Call: lm(formula = epm ~ n_days, data = v) Residuals: Min 1Q Median 3Q Max -693.59 -325.79 53.34 302.46 964.95 Coefficients: Estimate Std. Error t value Pr(>|t|) (Intercept) 2550.39 92.15 27.677 <2e-16 *** n_days -13.12 5.39 -2.433 0.0216 * --- Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1 Residual standard error: 410.1 on 28 degrees of freedom Multiple R-squared: 0.1746, Adjusted R-squared: 0.1451 F-statistic: 5.921 on 1 and 28 DF, p-value: 0.0216 Apologies for the newbiness of this question.

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• Tool for parsing smtp logs that finds bounces

  - by Željko Filipin

  Our web application sends e-mails. We have lots of users, and we get lots of bounces. For example, user changes company and his company e-mail is no longer valid. To find bounces, I parse smtp log file with log parser. Some bounces are great, like 550+#[email protected]. There is [email protected] in bounce. But some do not have e-mail in error message, like 550+No+such+recipient. I have created simple ruby script that parses logs (uses log parser) to find which mail caused something like 550+No+such+recipient. I am just surprised that I could not find a tool that does it. I have found tools like zabbix and splunk for log analysis, but they look like overkill for such simple task. Anybody knows a tool that would parse smtp logs, find bounces and e-mails that cause them? Edit: smtp server is microsoft smtp server.

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• Hadoop on windows server

  - by Luca Martinetti

  Hello, I'm thinking about using hadoop to process large text files on my existing windows 2003 servers (about 10 quad core machines with 16gb of RAM) The questions are: Is there any good tutorial on how to configure an hadoop cluster on windows? What are the requirements? java + cygwin + sshd ? Anything else? HDFS, does it play nice on windows? I'd like to use hadoop in streaming mode. Any advice, tool or trick to develop my own mapper / reducers in c#? What do you use for submitting and monitoring the jobs? Thanks

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• Graphical Programming Language

  - by prosseek

  In control engineering or instrumentation, I see Simulink or LabVIEW(G) is pretty popular. In ESL design, I see that Agilent SystemVue is gaining some popularity. If you see the well established compiler theroy, almost 100% is about the textual language. But how about the graphical language? Is there any noticable research or discussion about the graphical programming language? In terms of Theory about Graphical Language - syntactic/semantic analysis and whatever relevant expressiveness (Actually, I asked a question about it at SO - http://stackoverflow.com/questions/2427496/what-do-you-mean-by-the-expressiveness-in-programming-lanuguage) Possibility of the Graphical language ... Or what do you think about the Graphical Programming Language?

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• Out of memory error while using clusterdata in MATLAB

  - by Hossein

  Hi, I am trying to cluster a Matrix (size: 20057x2).: T = clusterdata(X,cutoff); but I get this error: ??? Error using == pdistmex Out of memory. Type HELP MEMORY for your options. Error in == pdist at 211 Y = pdistmex(X',dist,additionalArg); Error in == linkage at 139 Z = linkagemex(Y,method,pdistArg); Error in == clusterdata at 88 Z = linkage(X,linkageargs{1},pdistargs); Error in == kmeansTest at 2 T = clusterdata(X,1); can someone help me. I have 4GB of ram, but think that the problem is from somewhere else..

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• MYSQL KEY-VALUE PAIR Viability

  - by Amit

  Hi, I am new to mysql and I am looking for some answers to the follwoing questions: a) Can mysql community server can be leveraged for a key-value pair type database.?? b) Which mysql engine is best suited for a key-value pair type database ?? c) Is Mysql cluster a must for horizontal scaling of key-value based datastore or can it be acheived using MySQL replication?? d) Are there any docs or whitepapers for best practices when implementiing a kv datastore on mysql?? e) Are there any known big implementations other that friendfeed doing kv pair using MYSQL?? Would really appreciate some advise from all you Mysql gurus out there !! Thanks In Advance, Amit

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• Getting clusters of rows close together in time

  - by Mike

  I have a table basically like so ID | ItemID | Start | End | --------------------------------------------------------------- 1 234 10/20/09 8:34:22 10/20/09 8:35:10 2 274 10/20/09 8:35:30 10/20/09 8:36:27 3 272 10/21/09 12:15:00 10/21/09 12:17:00 4 112 10/21/09 12:20:14 10/21/09 12:21:21 5 15 10/21/09 12:22:39 10/21/09 12:24:15 There are two "clusters" of entries here, 1-2 and 3-5 separated by a gap in time, specifically 30 minutes is what I'm interested in. What I would like is the first and last rows of the cluster of entries. This is fairly easy to achieve by retrieving all the rows and looping through them in order of start time, but I'd like to have it in SQL if possible. I'm using SQL Server 2008, thanks.

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• NDepend: How to not display 'tier' assemblies in dependency graph?

  - by Edward Buatois

  I was able to do this in an earlier version of nDepend by going to tools-options and setting which assemblies would be part of the analysis (and ignore the rest). The latest version of the trial version of nDepend lets me set it, but it seems to ignore the setting and always analyze all assemblies whether I want it to or not. I tried to delete the "tier" assemblies by moving them over to the "application assemblies" list, but when I delete them out of there, they just get added back to the "tier" list, which I can't ignore. I don't want my dependency graph to contain assemblies like "system," "system.xml," and "system.serialization!" I want only MY assemblies in the dependency graph! Or is that a paid-version feature now? Is there a way to do what I'm talking about?

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• Essential skills of a Data Scientist

  - by harshsinghal

  I would like to know more about the relevant skills in the arsenal of a Data Scientist, and with new technologies coming in every day, how one picks and chooses the essentials. A few ideas germane to this discussion: Knowing SQL and the use of a DB such as MySQL, PostgreSQL was great till the advent of NoSql and non-relational databases. MongoDB, CouchDB etc. are becoming popular to work with web-scale data. Knowing a stats tool like R is enough for analysis, but to create applications one may need to add Java, Python, and such others to the list. Data now comes in the form of text, urls, multi-media to name a few, and there are different paradigms associated with their manipulation. What about cluster computing, parallel computing, the cloud, Amazon EC2, Hadoop ? OLS Regression now has Artificial Neural Networks, Random Forests and other relatively exotic machine learning/data mining algos. for company Thoughts?

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• All possible values of int from the smallest to the largest, using Java.

  - by Totophil

  Write a program to print out all possible values of int data type from the smallest to the largest, using Java. Some notable solutions as of 8th of May 2009, 10:44 GMT: 1) Daniel Lew was the first to post correctly working code. 2) Kris has provided the simplest solution for the given problem. 3) Tom Hawtin - tackline, came up arguably with the most elegant solution. 4) mmyers pointed out that printing is likely to become a bottleneck and can be improved through buffering. 5) Jay's brute force approach is notable since, besides defying the core point of programming, the resulting source code takes about 128 GB and will blow compiler limits. As a side note I believe that the answers do demonstrate that it could be a good interview question, as long as the emphasis is not on the ability to remember trivia about the data type overflow and its implications (that can be easily spotted during unit testing), or the way of obtaining MAX and MIN limits (can easily be looked up in the documentation) but rather on the analysis of various ways of dealing with the problem.

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• Determining which JavaScript/CSS browser features are required

  - by Alan Neal

  My website uses a variety of technologies, such as JQuery, new CSS definitions (e.g., moz-selection, -webkit-user-select), etc. The site works perfectly with Google Chrome and Safari, but has some quirkiness in Firefox, IE, and some of the other browsers. I want to write a script to check for necessary browser features but, with several thousand lines of code and CSS definitions, I'm not certain which features I should be looking for. Is there some sort of online analysis (similar to how JSLint operates) that would tell me which features my script and CSS files need? Are there tools (like FireBug) that provide this info?

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• Garbage collection of Strings returned from C# method calls in ascx pages

  - by Icarus

  Hi, For a web application developed on ASP.NET, we are finding that for user control files (ascx) we are returning long strings as a result of method calls. These are embedded in the ascx pages using the special tags <% %> When performing memory dump analysis for the application, we find that many of those strings are not being garbage collected. Also, the ascx pages are compiled to temporary DLLs and they are held in memory. Is this responsible for causing the long strings to remain in memory and not be garbage collected ? Note : The strings are larger than 85K in size.

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• Unable to run OpenMPI across more than two machines

  - by rcollyer

  When attempting to run the first example in the boost::mpi tutorial, I was unable to run across more than two machines. Specifically, this seemed to run fine: mpirun -hostfile hostnames -np 4 boost1 with each hostname in hostnames as <node_name> slots=2 max_slots=2. But, when I increase the number of processes to 5, it just hangs. I have decreased the number of slots/max_slots to 1 with the same result when I exceed 2 machines. On the nodes, this shows up in the job list: <user> Ss orted --daemonize -mca ess env -mca orte_ess_jobid 388497408 \ -mca orte_ess_vpid 2 -mca orte_ess_num_procs 3 -hnp-uri \ 388497408.0;tcp://<node_ip>:48823 Additionally, when I kill it, I get this message: node2- daemon did not report back when launched node3- daemon did not report back when launched The cluster is set up with the mpi and boost libs accessible on an NFS mounted drive. Am I running into a deadlock with NFS? Or, is something else going on?

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• ER Diagram flaws

  - by spacker_lechuck

  I have the following ER Diagram for a bank database - customers may have several accounts, accounts may be held jointly by several customers, and each customer is associated with an account set and accounts are members of one or more account sets. What design rules are violated? What modifications should be made and why? So far, a few flaws I'm not sure about are: 1) Redundant owner-address attribute in AcctSets Entity. 2) This ER does not include accounts with multiple owners with different addresses. My Question is: How would I go about fixing these flaws and/or other flaws that I may be missing from my analysis? Thanks!

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• How do I stop image spam from being uploaded to my (future) site?

  - by Pete Lacey

  I have in mind an idea for a generally accessible site that needs to allow images to be uploaded. But I'm stymied on how to prevent image spam: porn, ads in image form, etc. Assumptions: I'm assuming that the spammers are clever, even human. I'm skeptical of the efficacy of image analysis software. I do not have the resources to approve all uploads manually. I am willing to spend money on the solution -- within reason. This site will be location-aware, if that helps. How does Flickr do it or imgur? Or do they?

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• Estimate serialization size of objects?

  - by Stefan K.

  In my thesis, I woud like to enhance messaging in a cluster. It's important to log runtime information about how big a message is (should I prefer processing local or remote). I could just find frameoworks about estimating the object memory size based on java instrumentation. I've tested classmexer, which didn't come close to the serialization size and sourceforge SizeOf. In a small testcase, SizeOf was around 10% wrong and 10x faster than serialization. (Still transient breaks the estimation completely and since e.g. ArrayList is transient but is serialized as an Array, it's not easy to patch SizeOf. But I could live with that) On the other hand, 10x faster with 10% error doesn't seem very good. Any ideas how I could do better?

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• side effect gotchas in python/numpy? horror stories and narrow escapes wanted

  - by shabbychef

  I am considering moving from Matlab to Python/numpy for data analysis and numerical simulations. I have used Matlab (and SML-NJ) for years, and am very comfortable in the functional environment without side effects (barring I/O), but am a little reluctant about the side effects in Python. Can people share their favorite gotchas regarding side effects, and if possible, how they got around them? As an example, I was a bit surprised when I tried the following code in Python: lofls = [[]] * 4 #an accident waiting to happen! lofls[0].append(7) #not what I was expecting... print lofls #gives [[7], [7], [7], [7]] #instead, I should have done this (I think) lofls = [[] for x in range(4)] lofls[0].append(7) #only appends to the first list print lofls #gives [[7], [], [], []] thanks in advance

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• I'm really offtopic. But I've got a really good reason.

  - by lost

  Is there anyway Encryption on an unidentified file can be broken(file in question: config file and log files from ardamax keylogger). These files date back all the way to 2008. I searched everywhere, nothing on slashdot, nothing on google. Ardamax Keyviewer? Should I just write to Ardamax? I am at a loss of what to do. I feel comprimised. Anyone managed to decrpyt files with Crypto-analysis?

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