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  • Metamorphic generator

    - by user222094
    I am trying to find references about different designs of metamorphic generators can someone point me to the right direction. I have gone through some papers in ACM but couldn't find what I am looking for.

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  • Python: Determine whether list of lists contains a defined sequence

    - by duhaime
    I have a list of sublists, and I want to see if any of the integer values from the first sublist plus one are contained in the second sublist. For all such values, I want to see if that value plus one is contained in the third sublist, and so on, proceeding in this fashion across all sublists. If there is a way of proceeding in this fashion from the first sublist to the last sublist, I wish to return True; otherwise I wish to return False. In other words, for each value in sublist one, for each "step" in a "walk" across all sublists read left to right, if that value + n (where n = number of steps taken) is contained in the current sublist, the function should return True; otherwise it should return False. (Sorry for the clumsy phrasing--I'm not sure how to clean up my language without using many more words.) Here's what I wrote. a = [ [1,3],[2,4],[3,5],[6],[7] ] def find_list_traversing_walk(l): for i in l[0]: index_position = 0 first_pass = 1 walking_current_path = 1 while walking_current_path == 1: if first_pass == 1: first_pass = 0 walking_value = i if walking_value+1 in l[index_position + 1]: index_position += 1 walking_value += 1 if index_position+1 == len(l): print "There is a walk across the sublists for initial value ", walking_value - index_position return True else: walking_current_path = 0 return False print find_list_traversing_walk(a) My question is: Have I overlooked something simple here, or will this function return True for all true positives and False for all true negatives? Are there easier ways to accomplish the intended task? I would be grateful for any feedback others can offer!

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  • How to determine if two strings are sufficiently close?

    - by A.06
    We say that we can "hop" from the word w1 to the word w2 if they are "sufficiently close". We define w2 to be sufficiently close to w1 if one of the following holds: w2 is obtained from w1 by deleting one letter. w2 is obtained from w1 by replacing one of the letters in w1 by some letter that appears to its right in w1 and which is also to its right in alphabetical order. I have no idea how to check if 2. is fulfilled. To check if 1. is possible this is my function: bool check1(string w1, string w2){ if(w2.length - w1.length != 1){ return false; } for(int i = 0,int j = 0;i < w2.length;i++;j++){ if(w2[i] == w1[j]){//do nothing } else if(i == j){ j++; } else{ return false; } } return true; } Given two words w1 and w2, how do we check if we can 'hop' from w1 to w2?

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  • Should I amortize scripting cost via bytecode analysis or multithreading?

    - by user18983
    I'm working on a game sort of thing where users can write arbitrary code for individual agents, and I'm trying to decide the best way to divide up computation time. The simplest option would be to give each agent a set amount of time and skip their turn if it elapses without an action being decided upon, but I would like people to be able to write their agents decision functions without having to think too much about how long its taking unless they really want to. The two approaches I'm considering are giving each agent a set number of bytecode instructions (taking cost into account) each timestep, and making players deal with the consequences of the game state changing between blocks of computation (as with Battlecode) or giving each agent it's own thread and giving each thread equal time on the processor. I'm about equally knowledgeable on both concurrency and bytecode stuff, which is to say not very, so I'm wondering which approach would be best. I have a clearer idea of how I'd structure things if I used bytecode, but less certainty about how to actually implement the analysis. I'm pretty sure I can work up a concurrency based system without much trouble, but I worry it will be messier with more overhead and will add unnecessary complexity to the project.

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  • Is it OK to learn an algorithm from an open source project, and then implement it in a closed source project?

    - by Chris Barry
    Reference The post that started it all In order to clear up the original question I asked in a provocative manner, I have posed this question. If you learn an algorithm from an open source project, is it OK to use that algorithm in a separate closed sourced project? And if not, does that imply that you cannot use that knowledge ever again? If you can use it, what circumstance could that be? Just to clarify, I am not trying to evade a licence, otherwise I would not have asked the question in the first place. I believe this presents a difficult question and it is interesting to know where the debate can end up.

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  • Is there an appropriate coding style for implementing an algorithm during an interview?

    - by GlenPeterson
    I failed an interview question in C years ago about converting hex to decimal by not exploiting the ASCII table if (inputDigitByte > 9) hex = inputDigitByte - 'a'. The rise of Unicode has made this question pretty silly, but the point was that the interviewer valued raw execution speed above readability and error handling. They tell you to review algorithms textbooks to prepare for these interviews, yet these same textbooks tend to favor the implementation with the fewest lines of code, even if it has to rely on magic numbers (like "infinity") and a slower, more memory-intensive implementation (like a linked list instead of an array) to do that. I don't know what is right. Coding an algorithm within the space of an interview has at least 3 constraints: time to code, elegance/readability, and efficiency of execution. What trade-offs are appropriate for interview code? How much do you follow the textbook definition of an algorithm? Is it better to eliminate recursion, unroll loops, and use arrays for efficiency? Or is it better to use recursion and special values like "infinity" or Integer.MAX_VALUE to reduce the number of lines of code needed to write the algorithm? Interface: Make a very self-contained, bullet-proof interface, or sloppy and fast? On the one extreme, the array to be sorted might be a public static variable. On the other extreme, it might need to be passed to each method, allowing methods to be called individually from different threads for different purposes. Is it appropriate to use a linked-list data structure for items that are traversed in one direction vs. using arrays and doubling the size when the array is full? Implementing a singly-linked list during the interview is often much faster to code and easier remember for recursive algorithms like MergeSort. Thread safety - just document that it's unsafe, or say so verbally? How much should the interviewee be looking for opportunities for parallel processing? Is bit shifting appropriate? x / 2 or x >> 1 Polymorphism, type safety, and generics? Comments? Variable and method names: qs(a, p, q, r) vs: quickSort(theArray, minIdx, partIdx, maxIdx) How much should you use existing APIs? Obviously you can't use a java.util.HashMap to implement a hash-table, but what about using a java.util.List to accumulate your sorted results? Are there any guiding principals that would answer these and other questions, or is the guiding principal to ask the interviewer? Or maybe this should be the basis of a discussion while writing the code? If an interviewer can't or won't answer one of these questions, are there any tips for coaxing the information out of them?

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  • Solved: Chrome v18, self signed certs and &ldquo;signed using a weak signature algorithm&rdquo;

    - by David Christiansen
    So chrome has just updated itself automatically and you are now running v18 – great. Or is it… If like me, you are someone that are running sites using a self-signed SSL Certificate (i.e. when running a site on a developer machine) you may come across the following lovely message; Fear not, this is likely as a result of you following instructions you found on the apache openssl site which results in a self signed cert using the MD5 signature hashing algorithm. The simple fix is to generate a new certificate specifying to use the SHA1 signature hashing algorithm, like so; openssl req -new -x509 -sha1 -nodes -out server.crt -keyout server.key Simples!

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  • Performance comparison of Dictionaries

    - by Hun1Ahpu
    I'm interested in performance values (big-O analysis) of Lookup and Insert operation for .Net Dictionaries: HashTable, SortedList, StringDictionary, ListDictionary, HybridDictionary, NameValueCollection Link to a web page with the answer works for me too.

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  • Non-linear regression models in PostgreSQL using R

    - by Dave Jarvis
    Background I have climate data (temperature, precipitation, snow depth) for all of Canada between 1900 and 2009. I have written a basic website and the simplest page allows users to choose category and city. They then get back a very simple report (without the parameters and calculations section): The primary purpose of the web application is to provide a simple user interface so that the general public can explore the data in meaningful ways. (A list of numbers is not meaningful to the general public, nor is a website that provides too many inputs.) The secondary purpose of the application is to provide climatologists and other scientists with deeper ways to view the data. (Using too many inputs, of course.) Tool Set The database is PostgreSQL with R (mostly) installed. The reports are written using iReport and generated using JasperReports. Poor Model Choice Currently, a linear regression model is applied against annual averages of daily data. The linear regression model is calculated within a PostgreSQL function as follows: SELECT regr_slope( amount, year_taken ), regr_intercept( amount, year_taken ), corr( amount, year_taken ) FROM temp_regression INTO STRICT slope, intercept, correlation; The results are returned to JasperReports using: SELECT year_taken, amount, year_taken * slope + intercept, slope, intercept, correlation, total_measurements INTO result; JasperReports calls into PostgreSQL using the following parameterized analysis function: SELECT year_taken, amount, measurements, regression_line, slope, intercept, correlation, total_measurements, execute_time FROM climate.analysis( $P{CityId}, $P{Elevation1}, $P{Elevation2}, $P{Radius}, $P{CategoryId}, $P{Year1}, $P{Year2} ) ORDER BY year_taken This is not an optimal solution because it gives the false impression that the climate is changing at a slow, but steady rate. Questions Using functions that take two parameters (e.g., year [X] and amount [Y]), such as PostgreSQL's regr_slope: What is a better regression model to apply? What CPAN-R packages provide such models? (Installable, ideally, using apt-get.) How can the R functions be called within a PostgreSQL function? If no such functions exist: What parameters should I try to obtain for functions that will produce the desired fit? How would you recommend showing the best fit curve? Keep in mind that this is a web app for use by the general public. If the only way to analyse the data is from an R shell, then the purpose has been defeated. (I know this is not the case for most R functions I have looked at so far.) Thank you!

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  • Critiquing PHP-code / PerlCritic for PHP?

    - by jeekl
    I'm looking for an equivalent of PerlCritic for PHP. PerlCritc is a static source code analyzer that qritiques code and warns about everything from unused variables, to unsafe ways to handle data to almost anything. Is there such a thing for PHP that could (preferably) be run outside of an IDE, so that source code analysis could be automated?

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  • Analysis Services (SSAS) - Unexpected Internal Error when processing (ProcessUpdate). Workaround/Resolution

    - by James Rogers
    Many implementations require the use of ProcessUpdate to support Type 1 slowly changing dimensions. ProcessUpdate drops all of the affected indexes and aggregations in partitions affected by data that changes in the Dimension on which the ProcessUpdate is being performed. Twice now I have had situations where the processing fails with "Internal error: An unexpected exception occurred." Any subsequent ProcessUpdate processing will also fail with the same error. In talking with Microsoft the issue is corrupt indexes for the Dimension(s) being processed in the partitions of the affected measure group. I cannot guarantee that the following will correct your problem but it did in my case and saved us quite a bit of down time.   Workaround: ProcessIndexes on the entire cube that is being processed and throwing the error. This corrected the problem on both 2008 and 2008 R2.   Pros:  Does not require a complete rebuild of the data (ProcessFull) for either the Dimension or Cube. User access can continue while this ProcessIndexes in underway.   Cons: Can take a long time, especially on large cubes with many partitions, dimensions and/or aggregations. Query Performance is usually severely impacted due to the memory and CPU requirements for Aggregation and Index building   <Batch http://schemas.microsoft.com/analysisservices/2003/engine"http://schemas.microsoft.com/analysisservices/2003/engine">  <Parallel>     <Process xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:ddl2="http://schemas.microsoft.com/analysisservices/2003/engine/2" xmlns:ddl2_2="http://schemas.microsoft.com/analysisservices/2003/engine/2/2" xmlns:ddl100_100="http://schemas.microsoft.com/analysisservices/2008/engine/100/100" xmlns:ddl200="http://schemas.microsoft.com/analysisservices/2010/engine/200" xmlns:ddl200_200="http://schemas.microsoft.com/analysisservices/2010/engine/200/200">       <Object>         <DatabaseID>MyDatabase</DatabaseID>         <CubeID>MyCube</CubeID>       </Object>       <Type>ProcessIndexes</Type>       <WriteBackTableCreation>UseExisting</WriteBackTableCreation>     </Process>  </Parallel> </Batch>   The cube where the corruption exists can be found by having Profiler running while the ProcessUpdate is executing. The first partition that displays the "The Job has ended in failure." message in the TextData column will be part of the cube/measuregroup that has the corruption. You can try to run ProcessIndexes on just that measure group. This may correct the problem and save additional time if you have other large measure groups in the cube that are not affected by the corruption.   Remember to execute your normal ProcessUpdate batch after the successful completion of the ProcessIndexes. The ProcessIndexes does not pick up data changes.   Things that did not work: ProcessClearIndexes - why this doesn't work and ProcessIndexes does is unclear at this point. ProcessFull on the partition in question. In my latest case, this would clear up the problem for that partition. However, the next partition the ProcessUpdate touched that had data in it would generate and error. This leads me to believe the corruption problem will exist in all partitions in the affected measure group that have data in them.   NOTE: I experience this problem in both a SQL 2008 and SQL 2008 R2 Analysis Services environment, on separate built from the same relational database. This leads me to believe that some data condition in the tables used for the Dimension processing caused the corruption since the two environments were on physically separate hardware. I am waiting on Microsoft to analyze the dumps to give us more insight into what actually caused the corruption and will update this post accordingly.

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  • Can you authenticate into SSAS with AD LDS (ADAM) accounts?

    - by Jaxidian
    I'm very new to AD LDS and experienced but not qualified with SSAS, so my apologies for my ignorances with these. We have a couple implementations where we expose SSAS via an HTTPS proxy (msmdpump.dll) and currently we have a temporary domain setup handling this (where our end-users have a second account+creds to manage because of this = non-ideal). I want to move us towards a more permanent solution which I'm thinking of moving all authentication to AD LDS for our web apps, SSAS, and others. However, SSAS is where I'm concerned about this. I know SSAS requires Windows Authentication and to play nicely, and that this ultimately means Active Directory will be involved. Is there a way to get this done with AD LDS instead of having to use a full AD DS implementation? If so, how? (Note: My question over at StackOverflow had a suggestion that I post this question here on ServerFault instead. My apologies if I'm not asking in the right forum.)

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  • What consequences to take from what i read in logfiles?

    - by Helene Bilbo
    Since some weeks i manage my first Webserver, a Seaside application behind an Apache proxy on Linode, and i installed logwatch to send me daily logs. Where can i get information on when i have to act as a consequence of what i read in these logwatch reports? For example i read that all kinds of people try to login on funny nonexisting accounts or all kinds of webcrawlers test for nonexisting cms login pages, some ip adresses get banned and unbanned by fail2ban... I assume that's normal? Is it? But how do i know that i probably have to do something? What do i look for in the logs?

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  • What is the best/easiest way to use scripts to analyze network traffic?

    - by yungin
    I'm looking to analyze packets via scripts. I'd like to use something high level. I'm in a mac/linux environment. I'm currently looking at different python+libpcap libraries. Perhaps lua+wireshark too. Maybe tcpdump+bash (but not sure that has a lot of info i can use). I also heard good things about scapy. Not sure. I'm wondering if you have any recommendations? There's quite a few of them out there. What have you found that works best? I'd definitely want something scriptable not something that I need to compile (like c/c++, etc)

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  • Log application changes made to the system

    - by Maxim Veksler
    Hello, Windows 7, 64bit. I have an application which I don't trust but still need to run. I would like to run the installer of this application and later on the installed executable under some kind of "strace" for windows which will record what this application did to the system. Mainly: What files have been created / edited? What registery changed have been made? To what network hosts did the application tried to communicate? Ideally I would also be able to generate a "UNDO" action to undo all the changes. Please don't suggest full Virtualization solutions such as Virtualbox, VMWare and co. because the application should run in the host system (A "sandbox" approach will OTHO be accepted, IMHO). Do you any such utility I can use? Thank you, Maxim.

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  • How expensive to run PC 24/7 or how to figure out how to determine it?

    - by jasondavis
    I realize this question is difficult to answer as it would be different based on users location, what there PC is doing and what hardware it consist of, along with other factors but I am hoping someone could give me a very rough estimate. I have always ran many PC's in my home 24/7 and I am just now looking at it from a money/cost of electric point of view. 1) I live in Central Florida. Can anyone guesstomate/estimate the avaerage monthly or daily cost of running your average PC? Intel quad core processor, 1 SSD drive for OS and programs and 4-5 1-2 TB hard drives in a RAID setup for data. 750watt PSU. What would your guess be? 2) Also is there an accurate way to figure this out (non-super technical and confusing to a non-math person please) Also I have seen those kill-a-watt devices, do they figure this kind of stuff out for you? 3) Does a larger PSU make your PC consume more power? Thanks for any help, you can most likely tell I am somewhat lost about this!

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  • Cloud computing?

    - by Shawn H
    I'm an analyst and intermediate programmer working for a consulting company. Sometimes we are doing some intensive computing in Excel which can be frustrating because we have slow computers. My company does not have enough money to buy everyone new computers right now. Is there a cloud computing service that allows me to login to a high performance virtual computer from remote desktop? We are not that technical so preferrably the computer is running Windows and I can run Excel and other applications from this computer. Thanks

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  • What are my options with a downloaded Rackspace cloud image?

    - by schnippy
    I've got an unresponsive Rackspace slice that has defied all attempts at accessing. I created an emergency image from this and deleted it, downloading the files that compromise the image to a local source. There are a number of files / assets I would still like to recover from this server if possible but not sure exactly what I can do with the image files, if anything. Here's the files I have, for what its worth: emergency_########_######_cloudserver########.tar.gz.0 (5gb) emergency_########_######_cloudserver########.tar.gz.1 (5gb) emergency_########_######_cloudserver########.tar.gz.2 (5gb) emergency_########_######_cloudserver########.tar.gz.3 (50mb) emergency_########_######_cloudserver########.yml (25kb) Is it possible to mount this image as a drive? Are there other forensic recovery options?

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  • Connection error when trying to browse SSAS cube in BIDS

    - by lance
    SQL Server 2008 db instance is installed on a win 2003 server, networked (but no domain) VM. I can browse a cube from BIDS on the same VM, but when I try to browse the same cube on a windows 7 (home premium) networked machine, I get a connection error. The error suggests checking the datasource settings which I have, and when I click "test connection" on the datasource it is successful. Looking for probably causes and solutions?

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  • How to get more information from the system crash

    - by viraptor
    I'd like to debug an issue I'm having with a linux (debian stable) server, but I'm running out of ideas of how to confirm any diagnosis. Some background: The servers are running DL160 class with hardware raid between two disks. They're running a lot of services, mostly utilising network interface and CPU. There are 8 cpus and 7 "main" most cpu-hungry processes are bound to one core each via cpu affinity. Other random background scripts are not forced anywhere. The filesystem is writing ~1.5k blocks/s the whole time (goes up above 2k/s in peak times). Normal CPU usage for those servers is ~60% on 7 cores and some minimal usage on the last (whatever's running on shells usually). What actually happens is that the "main" services start using 100% CPU at some point, mainly stuck in kernel time. After a couple of seconds, LA goes over 400 and we lose any way to connect to the box (KVM is on it's way, but not there yet). Sometimes we see a kernel reporting hung task (but not always): [118951.272884] INFO: task zsh:15911 blocked for more than 120 seconds. [118951.272955] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [118951.273037] zsh D 0000000000000000 0 15911 1 [118951.273093] ffff8101898c3c48 0000000000000046 0000000000000000 ffffffffa0155e0a [118951.273183] ffff8101a753a080 ffff81021f1c5570 ffff8101a753a308 000000051f0fd740 [118951.273274] 0000000000000246 0000000000000000 00000000ffffffbd 0000000000000001 [118951.273335] Call Trace: [118951.273424] [<ffffffffa0155e0a>] :ext3:__ext3_journal_dirty_metadata+0x1e/0x46 [118951.273510] [<ffffffff804294f6>] schedule_timeout+0x1e/0xad [118951.273563] [<ffffffff8027577c>] __pagevec_free+0x21/0x2e [118951.273613] [<ffffffff80428b0b>] wait_for_common+0xcf/0x13a [118951.273692] [<ffffffff8022c168>] default_wake_function+0x0/0xe .... This would point at raid / disk failure, however sometimes the tasks are hung on kernel's gettsc which would indicate some general weird hardware behaviour. It's also running mysql (almost read-only, 99% cache hit), which seems to spawn a lot more threads during the system problems. During the day it does ~200kq/s (selects) and ~10q/s (writes). The host is never running out of memory or swapping, no oom reports are spotted. We've got many boxes with similar/same hardware and they all seem to behave that way, but I'm not sure which part fails, so it's probably not a good idea to just grab something more powerful and hope the problem goes away. Applications themselves don't really report anything wrong when they're running. I can run anything safely on the same hardware in an isolated environment. What can I do to narrow down the problem? Where else should I look for explanation?

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  • Building a Data Warehouse

    - by Paul
    I've seen tutorials articles and posts on how to build datawarehouses with star and snowflakes schemas, denormalization of OLTP databases fact and dimension tables and so on. Also seen comments like: Star schemas are for datamarts, at best. There is absolutely no way a true enterprise data warehouse could be represented in a star schema, or snowflake either. I want to create a database that will server for reporting services and maybe (if that isn't enough) install analisys services and extract reports and data from cubes. My question was : Is it really necesarry to redesign my current database and follow the star/snowflake schemas with fact and dimension tables ? Thank you

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  • Best tool for Analyzing IIS 7 SMTP Logs

    - by EfficionDave
    We're using IIS 7's SMTP service for sending out emails from our sites. I'm looking for a SMTP Log analyzer to make it easier for me to view the results and identify and problems (Blocks, Unauthorized relay attempts, blacklisting, ...). What is the best tool to use for this?

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