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• how to pass an arbitrary signature to Certifcate

  - by eskoba

  I am trying to sign certificate (X509) using secret sharing. that is shareholders combine their signatures to produce the final signature. which will be in this case the signed certificate. however practically from my understanding only one entity can sign a certificate. therefore I want to know: which entities or data of the x509certificate are actually taken as input to the signing algorithm? ideally I want this data to be signed by the shareholders and then the final combination will be passed to the X509certificate as valid signature. is this possible? how could it done? if not are they other alternatives?

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• is there a such thing as a randomly accessible pseudo-random number generator? (preferably open-sour

  - by lucid

  first off, is there a such thing as a random access random number generator, where you could not only sequentially generate random numbers as we're all used to, assuming rand100() always generates a value from 0-100: for (int i=0;i<5;i++) print rand100() output: 14 75 36 22 67 but also randomly access any random value like: rand100(0) would output 14 as long as you didn't change the seed rand100(3) would always output 22 rand100(4) would always output 67 and so on... I've actually found an open-source generator algorithm that does this, but you cannot change the seed. I know that pseudorandomness is a complex field; I wouldn't know how to alter it to add that functionality. Is there a seedable random access random number generator, preferably open source? or is there a better term for this I can google for more information? if not, part 2 of my question would be, is there any reliably random open source conventional seedable pseudorandom number generator so I could port it to multiple platforms/languages while retaining a consistent sequence of values for each platform for any given seed?

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• Can this be done with the ORM? - Django

  - by RadiantHex

  Hi folks, I have a few item listed in a database, ordered through Reddit's algorithm. This is it: def reddit_ranking(post): t = time.mktime(post.created_on.timetuple()) - 1134000000 x = post.score if x>0: y=1 elif x==0: y=-0 else: y=-1 if x<0: z=1 else: z=x return (log(z) + y * t/45000) I'm wondering if there is any clever way of using Django's ORM, in order to UPDATE the models in bulk. Without doing this: items = Item.objects.filter(created_on__gte=datetime.now()-timedelta(days=7)) for item in items: item.reddit_rank = reddit_rank(item) item.save() I know about the F() object, but I can't figure out if this function can be performed inside the ORM. Any ideas? Help would be very much appreciated!

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• Does the 80/20 rule of time management apply to developers?

  - by Dean

  Jeff's recent article linked to a time management example of the First Fit Decreasing algorithm, which talked about the Pareto principle (or, the 80/20 rule) of time management, that is, that 80% of the work we produce in 20% of our time. Now we've all heard the programmer quote: The first 90% of the code accounts for the first 90% of the development time. The remaining 10% of the code accounts for the other 90% of the development time. But all jokes aside, it is often as if 20% of your code is to do what you want, and the other 80% is to handle exceptions... so does the 80/20 rule really apply to developers? Does anyone have any examples of why it does / does not apply to us?

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• Query size of block device file in Python

  - by ??O?????

  Hello. I have a Python script that reads a file (typically from optical media) marking the unreadable sectors, to allow a re-attempt to read said unreadable sectors on a different optical reader. I discovered that my script does not work with block devices (e.g. /dev/sr0), in order to create a copy of the contained ISO9660/UDF filesystem, because os.stat().st_size is zero. The algorithm currently needs to know the filesize in advance; I can change that, but the issue (of knowing the block device size) remains, and it's not answered here, so I open this question. I am aware of the following two related SO questions: Determine the size of a block device (/proc/partitions, ioctl through ctypes) how to check file size in python? (about non-special files) Therefore, I'm asking: in Python, how can I get the file size of a block device file?

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• SQL Express Edition, SQL Compact Editin and SQLCMD for learning purpose

  - by Mil

  Hi, I want to learn programming in SQL from some SQL tutorial sites of which I heard of here but I need some environment for executing query's. I think I have both SQL CE and SQL EE installed on my computer but I have some doubts about these DBMS and I don't know exactly how to use SQLCMD utility so I hope someone here will have time and will to explain me the following: Since running sqlcmd -S.\sqlexpress at command prompt command gives "1" prompt I assume I have SQL express installed but anyway how can I be sure what I have installed on my machine since I cannot find in installed programs SQL Express Edition name? Can I ship and use database with my C# (VC# Express) application which was created with SQL EE (embedded?)? How can use sqlcmd for learning SQL, that is by issuing commands like create, use, select..., again emphasize is on learning SQL I do not want to run scripts but use interactive command prompt like with MySQL (since I want to use SQL I would pretty much like to avoid graphical tools for DBMS)? Please tell me if you have some other advice regarding as to what should I better use in learning how to program in SQL or should I stick with the above for now. Thanks in advance.

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• Writing a search engine

  - by wvd

  Hello all, The title might be a bit misleading, but I couldn't figure out a better title. I'm writing a simple search engine which will search on several sites for the specific domain. To be concrete: I'm writing a search engine for hardstyle livesets/aftermovies/tracks. To do I will search on the sites who provide livesets, tracks, and such. The problem here is speed, I need to pass the search query to 5-7 sites, get the results and then use my own algorithm to display the results in a sorted order. I could just "multithread" it, but it's easier said then done so I have a few questions. What would be the best solution to this problem? Should I just multithread/process this application, so I'm going to get a bit of speed-up? Are there any other solutions or I am doing something really wrong? Thanks, William van Doorn

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• Counting viable sublist lengths from an array.

  - by Ben B.

  This is for a genetic algorithm fitness function, so it is important I can do this as efficiently as possible, as it will be repeated over and over. Lets say there is a function foo(int[] array) that returns true if the array is a "good" array and false if the array is a "bad" array. What makes it good or bad does not matter here. Given the full array [1,6,8,9,5,11,45,16,9], lets say that subarray [1,6,8] is a "good" array and [9,5,11,45] is a "good" array. Furthermore [5,11,45,16,9] is a "good" array, and also the longest "good" subarray. Notice that while [9,5,11,45] is a "good" array, and [5,11,45,16,9] is a "good" array, [9,5,11,45,16,9] is a "bad" array. We wants the length counts of all "good" arrays, but not subarrays of "good" arrays. Furthermore, as described above, a "good" array might begin in the middle of another "good" array, but the combination of the two might be a "bad" array.

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• matlab fit exp2

  - by HelloWorld

  I'm unsuccessfully looking for documentation of fit function using exp2 (sum of 2 exponents). How to operate the function is clear: [curve, gof] = fit(x, y,'exp2'); But since there are multiple ways to fit a sum of exponents I'm trying to find out what algorithm is used. Particularly what happens when I'm fitting one exponent (the raw data) with a bit of noise, how the exponents are spread. I've simulated several cases, and it seems that it "drops" all the weight on the second set of coefficients, but row data analysis often shows different behavior. Does anyone have suggestions of documentation?

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• Any tips of how to handle hierarchical trees in relational model?

  - by George

  Hello all. I have a tree structure that can be n-levels deep, without restriction. That means that each node can have another n nodes. What is the best way to retrieve a tree like that without issuing thousands of queries to the database? I looked at a few other models, like flat table model, Preorder Tree Traversal Algorithm, and so. Do you guys have any tips or suggestions of how to implement a efficient tree model? My objective in the real end is to have one or two queries that would spit the whole tree for me. With enough processing i can display the tree in dot net, but that would be in client machine, so, not much of a big deal. Thanks for the attention

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• Embed ActionScript (AS) into flash

  - by David ???

  Hey SO, I've never dealt with Flash/ActionScript, so please bear with me. Mostly, I'm a bit confused. I've done many work with Java/C as well as HTML/Javascript. I am working with a designer who provides me with flash files (.swf). From my point of view, it's a simple "mock" to which I need to embed a single object. This object is a TextBox, with which the user interacts. I need to be able to Insert such a TextBox to a Flash file Retrieve text upon key event process it, and return it to the TextBox As I understood from other posts, I'll be working with AS, right? How do I embed such an object to an existing Flash file? Being that the graphical part is over once I have the TextBox, would I need any fancy IDE for that? What IDE is that (I usually work with Eclipse)? One last note: I am working with that designer, so I have access to all her creation process. She does not know code, nor do I think she'll get it. I would much prefer to give her as little headache as possible (e.g. just instruct her how to export the files to me from her Adobe Flash CS5 studio). Many thanks, David

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• Efficiency of while(true) ServerSocket Listen

  - by Submerged

  I am wondering if a typical while(true) ServerSocket listen loop takes an entire core to wait and accept a client connection (Even when implementing runnable and using Thread .start()) I am implementing a type of distributed computing cluster and each computer needs every core it has for computation. A Master node needs to communicate with these computers (invoking static methods that modify the algorithm's functioning). The reason I need to use sockets is due to the cross platform / cross language capabilities. In some cases, PHP will be invoking these java static methods. I used a java profiler (YourKit) and I can see my running ServerSocket listen thread and it never sleeps and it's always running. Is there a better approach to do what I want? Or, will the performance hit be negligible? Please, feel free to offer any suggestion if you can think of a better way (I've tried RMI, but it isn't supported cross-language. Thanks everyone

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• question about frequency of updating access

  - by I__

  i have a table in an access database this access database is used on a regular basis, basically from 9-5 someone else has a copy of this exact table. sometimes records are added, sometimes deleted, and sometimes data within the records is updated. i need to update the access database table with the offsite table every hour or so. what is the best algorithm of updating the data? there are about 5000 records. would it severely lock up the table for a few seconds every hour? i would like to publicly apologize for my rude comment to david fenton

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• C# how to create functions that are interpreted at runtime

  - by Lirik

  I'm making a Genetic Program, but I'm hitting a limitation with C# where I want to present new functions to the algorithm but I can't do it without recompiling the program. In essence I want the user of the program to provide the allowed functions and the GP will automatically use them. It would be great if the user is required to know as little about programming as possible. I want to plug in the new functions without compiling them into the program. In Python this is easy, since it's all interpreted, but I have no clue how to do it with C#. Does anybody know how to achieve this in C#? Are there any libraries, techniques, etc?

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• Java text classification problem

  - by yox

  Hello, I have a set of Books objects, classs Book is defined as following : Class Book{ String title; ArrayList<tags> taglist; } Where title is the title of the book, example : Javascript for dummies. and taglist is a list of tags for our example : Javascript, jquery, "web dev", .. As I said a have a set of books talking about different things : IT, BIOLOGY, HISTORY, ... Each book has a title and a set of tags describing it.. I have to classify automaticaly those books into separated sets by topic, example : IT BOOKS : Java for dummies Javascript for dummies Learn flash in 30 days C++ programming HISTORY BOOKS : World wars America in 1960 Martin luther king's life BIOLOGY BOOKS : .... Do you guys know a classification algorithm/method to apply for that kind of problems ? A solution is to use an external API to define the category of the text, but the problem here is that books are in different languages : french, spanish, english ..

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• C++: call original definition of operator equals

  - by Luis Daniel

  I am overloading the operator equals (==) as show bellow: #include <string> #include <algorithm> bool operator == (std::string str1, std::string str2) { std::transform(str1.begin(), str1.end(), str1.begin(), ::tolower); std::transform(str2.begin(), str2.end(), str2.begin(), ::tolower); return (str1 == str2); } but, the problem appear on line return (str1 == str2), because operator == is called recursively. So, how can I call the original definition for operator equals (not the overloaded) ? Best regards

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• Pure Java open-source libraries for portfolio selection (= constrained, non-linear optimization)?

  - by __roland__

  Does anyone know or has experience with a pure Java library to select portfolios or do some similar kinds of quadratic programming with constraints? There seems to be a lot of tools, as already discussed elsewhere - but what I would like to use is a pure Java implementation. Since I want to call the library from within another open-source software with a BSD-ish license I would prefer LGPL over GPL. Any help is appreciated. If you don't know such libraries, which is the most simple algorithm you would suggest to implement? It has to cope with an inequality constraint (all x_i = 0) and an equality constraint (sum of all x_i = 1).

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• Memcache failover and consistent hashing

  - by Industrial

  Hi everyone, I am trying to work out a good way to handle offline/down memcached servers in my current web application that are built with PHP. I just found this link that shows an approach on how to do what I want, I think: http://cmunezero.com/2008/08/11/consistent-memcache-hashing-and-failover-with-php/ Anyhow, it gets me confused when I start working with it and reading the PHP documention about failover with memcache. Why is offline memcache servers added to the $realInstance server pool together with the online servers? Reading the memcache documentation confuses me even more: http://www.php.net/manual/en/memcache.addserver.php status Controls if the server should be flagged as online. Setting this parameter to FALSE and retry_interval to -1 allows a failed server to be kept in the pool so as not to affect the key distribution algorithm. Requests for this server will then failover or fail immediately depending on the memcache.allow_failover setting. Default to TRUE, meaning the server should be considered online. Thanks,

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• How to create a custom ADO Multi Demensional Catalog with no database

  - by Alan Clark

  Does anyone know of an example of how to dynamically define and build ADO MD (ActiveX Data Objects Multidimensional) catalogs and cube definitions with a set of data other than a database? Background: we have a huge amount of data in our application that we export to a database and then query using the usual SQL joins, groups, sums etc to produce reports. The data in the application is originally in objects and arrays. The problem is the amount of data is so large the export can take 2 hours. So I am trying to figure out a good way of querying the objects in memory, either by a custom OLAP algorithm or library, or ADO MD. But I haven't been able to find an example of using ADO MD without a database behind it. We are using Delphi 2010 so would use ADO ActiveX but I imagine the ADO.NET MD is similar. I realize that if the application data was already stored in a database the problem would solve itself. Also if Delphi had LINQ capability I could query the objects and arrays that way.

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• Simple string encryption in .NET and Javascript

  - by jonathanconway

  I'm developing an ASP.NET MVC application in which I want to encrypt a short string on the server, using C#, and send it to the client-side. Then on the client-side it will be decrypted through Javascript code. Any thoughts on how to implement this? Do you know of a simple encryption algorithm (doesn't have to be bullet-proof secure) that can be easily translated from C# to Javascript or vice-versa? NOTE: I could do this entirely in C# and do the decryption through Ajax, but I'd prefer not to do it this way, as I want to reduce website traffic as much as possible.

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• Performance optimization strategies of last resort?

  - by jerryjvl

  There are plenty of performance questions on this site already, but it occurs to me that almost all are very problem-specific and fairly narrow. And almost all repeat the advice to avoid premature optimization. Let's assume: the code already is working correctly the algorithms chosen are already optimal for the circumstances of the problem the code has been measured, and the offending routines have been isolated all attempts to optimize will also be measured to ensure they do not make matters worse What I am looking for here is strategies and tricks to squeeze out up to the last few percent in a critical algorithm when there is nothing else left to do but whatever it takes. Ideally, try to make answers language agnostic, and indicate any down-sides to the suggested strategies where applicable. I'll add a reply with my own initial suggestions, and look forward to whatever else the SO community can think of.

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• Vectorizing sums of different diagonals in a matrix

  - by reve_etrange

  I want to vectorize the following MATLAB code. I think it must be simple but I'm finding it confusing nevertheless. r = some constant less than m or n [m,n] = size(C); S = zeros(m-r,n-r); for i=1:m-r for j=1:n-r S(i,j) = sum(diag(C(i:i+r-1,j:j+r-1))); end end The code calculates a table of scores, S, for a dynamic programming algorithm, from another score table, C. The diagonal summing is to generate scores for individual pieces of the data used to generate C, for all possible pieces (of size r). Thanks in advance for any answers! Sorry if this one should be obvious...

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• PHP Code to Generate Simple Flowchart

  - by revbackup

  I am making a flowchart out the subjects in the curriculum of our school. a flowchart is generated through its preRequisite.... for example FIRST YEAR FIRST SEMESTER SUBJECTS ---- PREREQUISITE MATH 1 ---- NONE MATH 2 ---- NONE ENGL 1 ---- NONE SOCIO 1 ----- NONE POLSCI 1 ----- NONE FIRSTE YEAR SECOND SEMESTER SUBJECTS ---- PREREQUISITE MATH 3 ----- MATH 1 MATH 4 ----- MATH 2, MATH 1 ENGL 2 ----- ENGL 1 POLSCI 2 ----- POLSCI 1 So, I must print it this way, just using simple PHP but difficult Logic.: MATH1 -----> MATH3 -----> MATH4 MATH 2 ----->MATH 4 ENGL1 -----> ENGL 2 SOCIO 1 POLSCI 1 -----> POLSCI 2 Can anyone give me a good algorithm for this, because this is really difficult. I am planning to echo the results in an HTML table, and it makes it more complicated. Do you have suggestions how to solve this problem properly and display the results also properly???? Thank you in advance!

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• Qt QTextEdit Qt4.2 Valid HTML String

  - by Matthew Hoggan

  I am trying to generate the correct HTML to render to a QTextEdit Using Qt 4.2 on RHEL 5.3. So far my algorithm generates the following html. I am not an expert web developer, but to me this string seems valid. 319:14:27:22: <font color="rgb(255,0,0)" bgcolor="rgb(255,0,0)">Message</font><br> What needs to change to get the colours to render. Currently it just renders as black text on a white background.

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• Objective C loop logic

  - by Graham

  Hi guys, I'm really new to programming in Obj-C, my background is in labview which is a graphical programming language, I've worked with Visual Basic some and HTML/CSS a fair amount as well. I'm trying to figure out the logic to create an array of data for the pattern below. I need the pattern later to extract data from another 2 arrays in a specific order. I can do it by referencing a = 1, b = 2, c = 3 etc and then creating the array with a, b, c but I want to use a loop so that I don't have 8 references above the array. These references will be used to generate another generation of data so unless I can get help figuring out the logic I'll actually end up with 72 references above the array. // This is the first one which gives the pattern 0 0 0 0 (etc) // 1 1 1 1 // 2 2 2 2 NSMutableArray * expSecondRef_one = [NSMutableArray array]; int a1 = 0; while (a1 < 9) { int a2 = 0; while (a2 < 8) { NSNumber * a3 = [NSNumber numberWithInt:a1]; [expSecondRef_one addObject:a3]; a2++; } a1++; } // This is the second one which I'm stumbling over, I am looking for the pattern 1 2 3 4 5 6 7 8 // 0 2 3 4 5 6 7 8 // 0 1 3 4 5 6 7 8 // 0 1 2 4 5 6 7 8 // etc to -> // 0 1 2 3 4 5 6 7 If you run it in a line every 9th number is -1 but I don't know how to do that over a pattern of 8. Thanks in advance! Graham

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