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• What is the best Java numerical method package?

  - by Bob Cross

  I am looking for a Java-based numerical method package that provides functionality including: Solving systems of equations using different numerical analysis algorithms. Matrix methods (e.g., inversion). Spline approximations. Probability distributions and statistical methods. In this case, "best" is defined as a package with a mature and usable API, solid performance and numerical accuracy. Edit: derick van brought up a good point in that cost is a factor. I am heavily biased in favor of free packages but others may have a different emphasis.

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• Solving a SQL Server Deadlock situation

  - by mjh41

  I am trying to find a solution that will resolve a recurring deadlock situation in SQL server. I have done some analysis on the deadlock graph generated by the profiler trace and have come up with this information: The first process (spid 58) is running this query: UPDATE cds.dbo.task_core SET nstate = 1 WHERE nmboxid = 89 AND ndrawerid = 1 AND nobjectid IN (SELECT nobjectid FROM ( SELECT nobjectid, count(nobjectid) AS counting FROM cds.dbo.task_core GROUP BY nobjectid) task_groups WHERE task_groups.counting > 1) The second process (spid 86) is running this query: INSERT INTO task_core (…) VALUES (…) spid 58 is waiting for a Shared Page lock on CDS.dbo.task_core (spid 86 holds a conflicting intent exclusive (IX) lock) spid 86 is waiting for an Intent Exclusive (IX) page lock on CDS.dbo.task_core (spid 58 holds a conflicting Update lock)

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• MDX: How To Aggregate Hierarchy Level Members With Same Name

  - by Dave Frautnick

  Greetings, I am new to MDX, and am having trouble understanding how to perform an aggregation on a hierarchy level with members that have the same names. This query is particular to Microsoft Analysis Services 2000 cubes. I have a given hierarchy dimension with levels defined as follows: [Segment].[Flow].[Segment Week] Within the [Segment Week] level, I have the following members: [Week- 1] [Week- 2] [Week- 3] ... [Week- 1] [Week- 2] [Week- 3] The members have the same names, but are aligned with a different [Flow] in the parent level. So, the first occurrence of the [Week- 1] member aligns with [Flow].[A] while the second occurrence of [Week- 1] aligns with [Flow].[B]. What I am trying to do is aggregate all the members within the [Segment Week] level that have the same name. In SQL terms, I want to GROUP BY the member names within the [Segment Week] level. I am unsure how to do this. Thank you. Dave

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• Is AMQP suitable as both an intra and inter-machine software bus?

  - by Bwooce

  I'm trying to get my head around AMQP. It looks great for inter-machine (cluster, LAN, WAN) communication between applications but I'm not sure if it is suitable (in architectural, and current implementation terms) for use as a software bus within one machine. Would it be worth pulling out a current high performance message passing framework to replace it with AMQP, or is this falling into the same trap as RPC by blurring the distinction between local and non-local communication? I'm also wary of the performance impacts of using a WAN technology for intra-machine communications, although this may be more of an implementation concern than architecture. War stories would be appreciated.

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• Reducing time in C# Forms Control.set_Text(string) function

  - by awshepard

  Hoping for a quick answer (which SO seems to be pretty good for)... I just ran a performance analysis with VS2010 on my app, and it turns out that I'm spending about 20% of my time in the Control.set_Text(string) function, as I'm updating labels in quite a few places in my app. The window has a timer object (Forms timer, not Threading timer) that has a timer1_Tick callback, which updates one label every tick (to give a stop-watch sort of effect), and updates about 15 labels once each second. Does anyone have quick suggestions for how to reduce the amount of time spent updating text on a form, other than increasing the update interval? Are there other structures or functions I should be using?

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• SQL Server 2008 BULK INSERT causes more reads than writes. Why?

  - by sh1ng

  I've huge a table (a few billion rows) with a clustered index and two non-clustered indices. A BULK INSERT operation produces 112000 reads and only 383 writes (duration 19948ms). It's very confusing to me. Why do reads exceed writes? How can I reduce it? update query insert bulk DenormalizedPrice4 ([DP_ID] BigInt, [DP_CountryID] Int, [DP_OperatorID] SmallInt, [DP_OperatorPriceID] BigInt, [DP_SpoID] Int, [DP_TourTypeID] Int, [DP_CheckinDate] Date, [DP_CurrencyID] SmallInt, [DP_Cost] Decimal(9,2), [DP_FirstCityID] Int, [DP_FirstHotelID] Int, [DP_FirstBuildingID] Int, [DP_FirstHotelGlobalStarID] Int, [DP_FirstHotelGlobalMealID] Int, [DP_FirstHotelAccommodationTypeID] Int, [DP_FirstHotelRoomCategoryID] Int, [DP_FirstHotelRoomTypeID] Int, [DP_Days] TinyInt, [DP_Nights] TinyInt, [DP_ChildrenCount] TinyInt, [DP_AdultsCount] TinyInt, [DP_TariffID] Int, [DP_DepartureCityID] Int, [DP_DateCreated] SmallDateTime, [DP_DateDenormalized] SmallDateTime, [DP_IsHide] Bit, [DP_FirstHotelAccommodationID] Int) with (CHECK_CONSTRAINTS) No triggers & foreign keys Cluster Index by DP_ID and two non-unique indexes(with fillfactor=90%) And one more thing DB stored on RAID50 with stripe size 256K

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• How to improve workflow for creating a Lua-based Wireshark dissector

  - by piyo

  I've finally created a Dissector for my UDP protocol in Lua for Wireshark, but the work flow is just horrendous. It consists of editing my custom Lua file in my editor, then double-clicking my example capture file to launch Wireshark to see the changes. If there was an error, Wireshark informs me via dialogs or a red line in the Tree analysis sub-pane. I then re-edit my custom Lua file and then close that Wireshark instance, then double-click my example capture file again. It's like compiling a C file and only seeing one compiler error at a time. Is there a better (faster) way of looking at my changes, without having to restart Wireshark all the time? At the time, I was using Wireshark 1.2.9 for Windows with Lua enabled.

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• JJIL Android Java Problem

  - by Danny_E

  Hey Guys, Long time reader never posted until now. Im having some trouble with Android, im implementing a library called JJIL its an open source imaging library. My problem is this i need to run some analysis on an image and to do so i need to have it in jjil.core.image format and once those processes are complete i need to convert the changed image from jjil.core.image to java.awt.image. I cant seem to find a method of doing this does anyone have any ideas or have any experience with this? I would be grateful of any help. Danny

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• EJB3.1 Remote invocation - is it distributed automatically? is it expensive?

  - by Hank

  I'm building a JEE6 application with performance and scalability in the forefront of my mind. Business logic and JPA2-facade is held in stateless session beans (EJB3.1). As of right now, the SLSBs implement only @Remote-interfaces. When a bean needs to access another bean, it does so via RMI. My reasoning behind this is the assumption that, once the application runs on a bunch of clustered application servers, the RMI-part allows the execution to be distributed across the whole cluster automagically. Is that a correct assumption? I'm fine with dealing with the downsides of that (objects lose entityManager session, pass-by-value), at least I think so. But I am wondering if constant remote invocation isn't adding more load then necessary.

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• Screening (multi)collinearity in a regression model

  - by aL3xa

  I hope that this one is not going to be "ask-and-answer" question... here goes: (multi)collinearity refers to extremely high correlations between predictors in the regression model. How to cure them... well, sometimes you don't need to "cure" collinearity, since it doesn't affect regression model itself, but interpretation of an effect of individual predictors. One way to spot collinearity is to put each predictor as a dependent variable, and other predictors as independent variables, determine R2, and if it's larger than .9 (or .95), we can consider predictor redundant. This is one "method"... what about other approaches? Some of them are time consuming, like excluding predictors from model and watching for b-coefficient changes - they should be noticeably different. Of course, we must always bare in mind specific context/goal of analysis... Sometimes, only remedy is to repeat a research, but right now, I'm interested in various ways of screening redundant predictors when (multi)collinearity occurs in a regression model.

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• Speeding up jQuery empty() or replaceWith() Functions When Dealing with Large DOM Elements

  - by Levi Hackwith

  Let me start off by apologizing for not giving a code snippet. The project I'm working on is proprietary and I'm afraid I can't show exactly what I'm working on. However, I'll do my best to be descriptive. Here's a breakdown of what goes on in my application: User clicks a button Server retrieves a list of images in the form of a data-table Each row in the table contains 8 data-cells that in turn each contain one hyperlink Each request by the user can contain up to 50 rows (I can change this number if need be) That means the table contains upwards of 800 individual DOM elements My analysis shows that jQuery("#dataTable").empty() and jQuery("#dataTable).replaceWith(tableCloneObject) take up 97% of my overall processing time and take on average 4 - 6 seconds to complete. I'm looking for a way to speed up either of the above mentioned jQuery functions when dealing with massive DOM elements that need to be removed / replaced. I hope my explanation helps.

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• Better way to make a bash script self-tracing?

  - by Kevin Little

  I have certain critical bash scripts that are invoked by code I don't control, and where I can't see their console output. I want a complete trace of what these scripts did for later analysis. To do this I want to make each script self-tracing. Here is what I am currently doing: #!/bin/bash # if last arg is not '_worker_', relaunch with stdout and stderr # redirected to my log file... if [[ "$BASH_ARGV" != "_worker_" ]]; then $0 "$@" _worker_ >>/some_log_file 2>&1 # add tee if console output wanted exit $? fi # rest of script follows... Is there a better, cleaner way to do this?

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• Orbital equations, and power required to run them

  - by Adam Davis

  Due to a discussion on the SO IRC today, I'm curious about orbital mechanics, and The equations needed to solve orbital problems The computing power required to solve complex problems The question in particular is calculating when the Earth will plow into the Sun (or vice versa, depending on the frame of reference). I suspect that all the gravitational pulls within our solar system may need to be calculated, which makes me wonder what type of computer cluster is required, or can this be done on a single box? I don't have the experience to do a back of the napkin test here, but perhaps you do? Also, much thx to Gortok for the original inspiration (see comments).

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• XNA or C# Pop-up progress bar for the LoadContent() method

  - by Warlax

  Hey people, We wrote a small game using Microsoft's XNA Game Studio 3.1. The LoadContent() takes a long time because, other than loading models, and config files, we're also running some one-time (per run) terrain analysis. We are not C# or XNA programmers... we're Java programmers, and want to be able to give the user some feedback that the system is loading. Preferably, this will be through a simple pop-up with a progress bar that will say something simple like "loading please wait". The progress bar doesn't have to be a 0 to 1 progress bar, it can instead be one of those 'back and forth' progress bars. I was hoping for some quick copy-paste ready code to just do that - as it is not a central piece of our project, nor do we have a need to delve into too much documentation. I appreciate you time, effort, and possible donation. Thanks.

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• Genetic programming in c++, library suggestions?

  - by shuttle87

  I'm looking to add some genetic algorithms to an Operations research project I have been involved in. Currently we have a program that aids in optimizing some scheduling and we want to add in some heuristics in the form of genetic algorithms. Are there any good libraries for generic genetic programming/algorithms in c++? Or would you recommend I just code my own? I should add that while I am not new to c++ I am fairly new to doing this sort of mathematical optimization work in c++ as the group I worked with previously had tended to use a proprietary optimization package. We have a fitness function that is fairly computationally intensive to evaluate and we have a cluster to run this on so parallelized code is highly desirable. So is c++ a good language for this? If not please recommend some other ones as I am willing to learn another language if it makes life easier. thanks!

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• Separation of static and dynamic content in Java EE applications

  - by Dan

  We work with IBM products and we typically use IBM Http Servers (read Apache) as a reverse proxy for our application servers. For performance reasons we serve static content (.gif, .jpg, .css, .html etc.) from our http servers, to ease the burden a bit from the application server. So far, we have to distribute files to http server and configure it manually (writing custom scripts at best.) The problem is the effort needed to keep everything in synch, especially when you need to update the app. Does any Java EE product support this “out of the box”? Is there a way to have application server do this automatically, like in cluster configuration for example, where master node is in charge of distributing the application to other nodes and for keeping everything in synch.

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• How does one modify the thread scheduling behavior when using Threading Building Blocks (TBB)?

  - by J Teller

  Does anyone know how to modify the thread scheduling (specifically affinity) when using TBB? Doing a high level analysis on a simple parallel-for application, it seems like TBB is specifying the underlying threads' affinity in a way that reduces performance. Specifically, the cores I'm running on have hyper-threading enabled, and it looks like TBB is affinitizing threads to the same core even if there is a different core left completely unloaded. FWIW, I realize it's likely that TBB is doing the "right thing" and that changing the threads' affinity will only reduce performance. I'd just like to experiment with it to see if that's really the case.

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• Manual stack backtrace on Windows mobile (SEH)

  - by caahab

  Following situation: I'm developing an windows mobile application using the sdk 6. Target machine is a nautiz x7. To improve the error reporting I want to catch the structured exceptions (SEH) and do a stack backtrace to store some information for analysis. So far I have the information where the exception was thrown (windows core.dll) and I can backtrace the return adresses thru the stack. But what I want to know is, which instruction in my code caused the exception? Does anyone know how to use the available exception and context information to get the appropriate function/instruction address? Unfortunately windows mobile 6 sdk for pocketpc does not support all the helper functions to do stackwalks or mini dumps.

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• Merge overlapping date intervals

  - by leoinfo

  Is there a better way of merging overlapping date intervals? The solution I came up with is so simple that now I wonder if someone else has a better idea of how this could be done. /***** DATA EXAMPLE *****/ DECLARE @T TABLE (d1 DATETIME, d2 DATETIME) INSERT INTO @T (d1, d2) SELECT '2010-01-01','2010-03-31' UNION SELECT '2010-04-01','2010-05-31' UNION SELECT '2010-06-15','2010-06-25' UNION SELECT '2010-06-26','2010-07-10' UNION SELECT '2010-08-01','2010-08-05' UNION SELECT '2010-08-01','2010-08-09' UNION SELECT '2010-08-02','2010-08-07' UNION SELECT '2010-08-08','2010-08-08' UNION SELECT '2010-08-09','2010-08-12' UNION SELECT '2010-07-04','2010-08-16' UNION SELECT '2010-11-01','2010-12-31' UNION SELECT '2010-03-01','2010-06-13' /***** INTERVAL ANALYSIS *****/ WHILE (1=1) BEGIN UPDATE t1 SET t1.d2 = t2.d2 FROM @T AS t1 INNER JOIN @T AS t2 ON DATEADD(day, 1, t1.d2) BETWEEN t2.d1 AND t2.d2 -- AND t1.d2 <= t2.d2 /***** this condition is useless *****/ IF @@ROWCOUNT = 0 BREAK END /***** RESULT *****/ SELECT StartDate = MIN(d1) , EndDate = d2 FROM @T GROUP BY d2 ORDER BY StartDate, EndDate /***** OUTPUT *****/ /***** StartDate EndDate 2010-01-01 2010-06-13 2010-06-15 2010-08-16 2010-11-01 2010-12-31 *****/ EDIT: I realized that the t1.d2 <= t2.d2 condition is not really useful.

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• Illegal instruction gcc assembler.

  - by Bernt

  In assembler: .globl _test _test: pushl %ebp movl %esp, %ebp movl $0, %eax pushl %eax popl %ebp ret Calling from c main() { _test(); } Compile: gcc -m32 -o test test.c test.s This code gives me illegal instruction sometimes and segment fault other times. In gdc i always get illegal instruction, this is just a simple test, i had a larger program that was working and suddenly after no apperant reason stopped working, now i always get this error even if i start from scratch like above. I have narrowed it down to pushl %eax (or any other register....), if i comment out that line the code runs fine. Any ideas? (I'm running the program at my universities linux cluster, so I have not changed any settings..)

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• Screening (multi)collinearity in a reggresion model

  - by aL3xa

  I hope that this one is not going to be "ask-and-answer" question... here goes: (multi)collinearity refers to extremely high correlations between predictors in the regression model. How to cure them... well, sometimes you don't need to "cure" collinearity, since it doesn't affect regression model itself, but interpretation of an effect of individual predictors. One way to spot collinearity is to put each predictor as a dependent variable, and other predictors as independent variables, determine R2, and if it's larger than .9 (or .95), we can consider predictor redundant. This is one "method"... what about other approaches? Some of them are time consuming, like excluding predictors from model and watching for b-coefficient changes - they should be noticeably different. Of course, we must always bare in mind specific context/goal of analysis... Sometimes, only remedy is to repeat a research, but right now, I'm interested in various ways of screening redundant predictors when (multi)collinearity occurs in a regression model.

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• What is the most useful R trick?

  - by Dirk Eddelbuettel

  In order to share some more tips and tricks for R, what is you single-most useful feature or trick? Clever vectorization? Data input/output? Visualization and graphics? Statistical analysis? Special functions? The interactive environment itself? One item per post, and we will see if we get a winner by means of votes. [Edit 25-Aug 2008]: So after one week, it seems that the simple str() won the poll. As I like to recommend that one myself, it is an easy answer to accept.

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• What was that tutorial on pointers?

  - by pecker

  Hello, I once read a tutorial/article on Pointers somewhere. It was not a general tutorial but it explained how to clearly understand the complex & confusing pointers (especially like the ones that are usually asked in interview). It was more like http://www.codeweblog.com/right-left-rule-complex-pointer-analysis/ I'm unable to find it. Could any one post it here. PS: I did tried to google it but couldn't find. I'm asking it here because I thought it was popular.

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• Cassandra performance slow down with counter column

  - by tubcvt

  I have a cluster (4 node ) and a node have 16 core and 24 gb ram: 192.168.23.114 datacenter1 rack1 Up Normal 44.48 GB 25.00% 192.168.23.115 datacenter1 rack1 Up Normal 44.51 GB 25.00% 192.168.23.116 datacenter1 rack1 Up Normal 44.51 GB 25.00% 192.168.23.117 datacenter1 rack1 Up Normal 44.51 GB 25.00% We use about 10 column family (counter column) to make some system statistic report. Problem on here is that When i set replication_factor of this keyspace from 1 to 2 (contain 10 counter column family ), all cpu of node increase from 10% ( when use replication factor=1) to --- 90%. :( :( who can help me work around that :( . why counter column consume too much cpu time :(. thanks all

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• Leak caused by fread

  - by Jack

  I'm profiling code of a game I wrote and I'm wondering how it is possible that the following snippet causes an heap increase of 4kb (I'm profiling with Heapshot Analysis of Xcode) every time it is executed: u8 WorldManager::versionOfMap(FILE *file) { char magic[4]; u8 version; fread(magic, 4, 1, file); <-- this is the line fread(&version,1,1,file); fseek(file, 0, SEEK_SET); return version; } According to the profiler the highlighted line allocates 4.00Kb of memory with a malloc every time the function is called, memory which is never released. This thing seems to happen with other calls to fread around the code, but this was the most eclatant one. Is there anything trivial I'm missing? Is it something internal I shouldn't care about? Just as a note: I'm profiling it on an iPhone and it's compiled as release (-O2).

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