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• ISP Config 3 - squirrel login error & how to add an smtp server for sending mails

  - by A Prasetyo

  Hi, Case #1: I have ISPConfig3 running, sending email through telnet server.mydomain.com 25 are possible. Receiving email also possible. BUT!! problem occurs when I try to login to squirrel... I've been awaken for 2 days now and still couldn't figured out why logging in into squirrel always having an error: ERROR: Connection dropped by IMAP server. here is the /var/log/mail.log: Jun 3 00:23:27 server-01 imapd: Connection, ip=[::ffff:127.0.0.1] Jun 3 00:23:27 server-01 imapd: chdir /var/vmail/mydomain.com/info: Permission denied Jun 3 00:23:27 server-01 imapd: [email protected]: Permission denied I did chmod 777 & still doesn't work, only another message appeared Jun 3 00:24:28 server-01 imapd: Connection, ip=[::ffff:127.0.0.1] Jun 3 00:24:28 server-01 imapd: [email protected]: Account's mailbox directory is not owned by the correct uid or gid Try to do telnet to IMAP port telnet mydomain.com 143 Trying 63.105.102.48... Connected to mydomain.com. Escape character is '^]'. OK [CAPABILITY IMAP4rev1 UIDPLUS CHILDREN NAMESPACE THREAD=ORDEREDSUBJECT THREAD=REFERENCES SORT QUOTA IDLE ACL ACL2=UNION STARTTLS] Courier-IMAP ready. Copyright 1998-2008 Double Precision, Inc. See COPYING for distribution information. login [email protected] mypassword login NO Error in IMAP command received by server. and give no result... -_- I checked mysql.sock, I checked username and password in mysql db, everything is correct.. anyone can help? PLEASE?! Case #2: Does anyone know how to set or to view SMTP settings in ISPConfig 3? thank you..

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• Rails help looping trough has one and belongs to association

  - by Rails beginner

  This is my kategori controller show action: def show @kategori = Kategori.find(params[:id]) @konkurrancer = @kategori.konkurrancer respond_to do |format| format.html # show.html.erb format.xml { render :xml => @kategori } end end This is kategori view show file: <% @konkurrancer.each do |vind| %> <td><%= vind.name %></td> <td>4 ud af 5</td> <td><%= number_to_currency(vind.vaerdi, :unit => "DKK", :separator => ".", :delimiter => ".", :format => "%n %u", :precision => 0) %></td> <td>2 min</td> <td>Nyhedsbrev</td> <td><%= vind.udtraekkes.strftime("%d %B") %></td> </tr> <% end %> My kategori model: class Kategori < ActiveRecord::Base has_one :konkurrancer end My konkurrancer model: class Konkurrancer < ActiveRecord::Base belongs_to :kategori end I want show all of the konkurrancer that have an association to the kategori model With my code I get the following error: NoMethodError in Kategoris#show Showing C:/Rails/konkurranceportalen/app/views/kategoris/show.html.erb where line #12 raised: undefined method `each' for "#":Konkurrancer

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• Which linear programming package should I use for high numbers of constraints and "warm starts"

  - by davidsd

  I have a "continuous" linear programming problem that involves maximizing a linear function over a curved convex space. In typical LP problems, the convex space is a polytope, but in this case the convex space is piecewise curved -- that is, it has faces, edges, and vertices, but the edges aren't straight and the faces aren't flat. Instead of being specified by a finite number of linear inequalities, I have a continuously infinite number. I'm currently dealing with this by approximating the surface by a polytope, which means discretizing the continuously infinite constraints into a very large finite number of constraints. I'm also in the situation where I'd like to know how the answer changes under small perturbations to the underlying problem. Thus, I'd like to be able to supply an initial condition to the solver based on a nearby solution. I believe this capability is called a "warm start." Can someone help me distinguish between the various LP packages out there? I'm not so concerned with user-friendliness as speed (for large numbers of constraints), high-precision arithmetic, and warm starts. Thanks!

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• Nicely representing a floating-point number in python

  - by dln385

  I want to represent a floating-point number as a string rounded to some number of significant digits, and never using the exponential format. Essentially, I want to display any floating-point number and make sure it “looks nice”. There are several parts to this problem: I need to be able to specify the number of significant digits. The number of significant digits needs to be variable, which can't be done with with the string formatting operator. I need it to be rounded the way a person would expect, not something like 1.999999999999 I've figured out one way of doing this, though it looks like a work-round and it's not quite perfect. (The maximum precision is 15 significant digits.) >>> def f(number, sigfig): return ("%.15f" % (round(number, int(-1 * floor(log10(number)) + (sigfig - 1))))).rstrip("0").rstrip(".") >>> print f(0.1, 1) 0.1 >>> print f(0.0000000000368568, 2) 0.000000000037 >>> print f(756867, 3) 757000 Is there a better way to do this? Why doesn't Python have a built-in function for this?

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• Regexp that matches user-agents of end-user browsers but NOT crawlers with >90 % accuracy

  - by knorv

  I'm trying to construct a regexp that will evaluate to true for User-Agent:s of "browsers navigated by humans", but false for bots. Needless to say the matching will not be exact, but if it gets things right in say 90 % of cases that is more than good enough. My approach so far is to target the User-Agent string of the the five major desktop browsers (MSIE, Firefox, Chrome, Safari, Opera). Specifically I want the regexp NOT to match if the user-agent is a bot (Googlebot, msnbot, etc.). Currently I'm using the following regexp which appears to achieve the desired precision: ^(Mozilla.*(Gecko|KHTML|MSIE|Presto|Trident)|Opera).*$ I've observed small number of false negatives which are mostly mobile browsers. The exceptions all match: (BlackBerry|HTC|LG|MOT|Nokia|NOKIAN|PLAYSTATION|PSP|SAMSUNG|SonyEricsson) My question is: Given the desired accuracy level, how would you improve the regexp? Can you think of any major false positives or false negatives to the given regexp? Please note that the question is specifically about regexp-based User-Agent matching. There are a bunch of other approaches to solving this problem, but those are out of the scope of this question.

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• Dealing with Imprecise Drawing in CAD Drawing

  - by Graviton

  I have a CAD application, that allows user to draw lines and polygons and all that. One thorny problem that I face is user drawing can be highly imprecise, for example, a user might want to draw two rectangles that are connected to each other. Hence there should be one line shared by two rectangles. However, it's easy for user to, instead of draw a line, draw two lines that are very close to each other, so close to each other that when look from the screen, you would be mistaken that they are the same line, except that they aren't when you zoom in a little bit. My application would require user to properly draw the lines ( or my preprocessing must be able to do auto correction), or else my internal algorithm would not be able to process the inputs correctly. What is the best strategy to combat this kind of problem? I am thinking about rounding the point coordinates to a certain degree of precision, but although I can't exactly pinpoint the problem of this approach, but I feel that this is not the correct way of doing things, that this will introduce a new set of problem. Any idea?

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• How to read/write high-resolution (24-bit, 8 channel) .wav files in Java?

  - by dB'

  I'm trying to write a Java application that manipulates high resolution .wav files. I'm having trouble importing the audio data, i.e. converting the .wav file into an array of doubles. When I use a standard approach an exception is thrown. AudioFileFormat as = AudioSystem.getAudioFileFormat(new File("orig.wav")); --> javax.sound.sampled.UnsupportedAudioFileException: file is not a supported file type Here's the file format info according to soxi: dB$ soxi orig.wav soxi WARN wav: wave header missing FmtExt chunk Input File : 'orig.wav' Channels : 8 Sample Rate : 96000 Precision : 24-bit Duration : 00:00:03.16 = 303526 samples ~ 237.13 CDDA sectors File Size : 9.71M Bit Rate : 24.6M Sample Encoding: 32-bit Floating Point PCM Can anyone suggest the simplest method for getting this audio into Java? I've tried using a few techniques. As stated above, I've experimented with the Java AudioSystem (on both Mac and Windows). I've also tried using Andrew Greensted's WavFile class, but this also fails (WavFileException: Compression Code 3 not supported). One workaround is to convert the audio to 16 bits using sox (with the -b 16 flag), but this is suboptimal since it increases the noise floor. Incidentally, I've noticed that the file CAN be read by libsndfile. Is my best bet to write a jni wrapper around libsndfile, or can you suggest something quicker? Note that I don't need to play the audio, I just need to analyze it, manipulate it, and then write it out to a new .wav file. * UPDATE * I solved this problem by modifying Andrew Greensted's WavFile class. His original version only read files encoded as integer values ("format code 1"); my files were encoded as floats ("format code 3"), and that's what was causing the problem. I'll post the modified version of Greensted's code when I get a chance. In the meantime, if anyone wants it, send me a message.

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• What are the hibernate annotations used to persist a value typed Map with an enumerated type as a ke

  - by Jason Novak

  I am having trouble getting the right hibernate annotations to use on a value typed Map with an enumerated class as a key. Here is a simplified (and extremely contrived) example. public class Thing { public String id; public Letter startLetter; public Map<Letter,Double> letterCounts = new HashMap<Letter, Double>(); } public enum Letter { A, B, C, D } Here are my current annotations on Thing @Entity public class Thing { @Id public String id; @Enumerated(EnumType.STRING) public Letter startLetter; @CollectionOfElements @JoinTable(name = "Thing_letterFrequencies", joinColumns = @JoinColumn(name = "thingId")) @MapKey(columns = @Column(name = "letter", nullable = false)) @Column(name = "count") public Map<Letter,Double> letterCounts = new HashMap<Letter, Double>(); } Hibernate generates the following DDL to create the tables for my MySql database create table Thing (id varchar(255) not null, startLetter varchar(255), primary key (id)) type=InnoDB; create table Thing_letterFrequencies (thingId varchar(255) not null, count double precision, letter tinyblob not null, primary key (thingId, letter)) type=InnoDB; Notice that hibernate tries to define letter (my map key) as a tinyblob, however it defines startLetter as a varchar(255) even though both are of the enumerated type Letter. When I try to create the tables I see the following error BLOB/TEXT column 'letter' used in key specification without a key length I googled this error and it appears that MySql has issues when you try to make a tinyblob column part of a primary key, which is what hibernate needs to do with the Thing_letterFrequencies table. So I would rather have letter mapped to a varchar(255) the way startLetter is. Unfortunately, I've been fussing with the MapKey annotation for a while now and haven't been able to make this work. I've also tried @MapKeyManyToMany(targetEntity=Product.class) without success. Can anyone tell me what are the correct annotations for my letterCounts map so that hibernate will treat the letterCounts map key the same way it does startLetter?

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• Compiling and using NTL c++ library for Windows

  - by Martin Lauridsen

  Hi there, I have compiled the NTL inifite precision integer arithmetic library for c++, using Microsoft Visual Studio 2008. I did as explained, on this site, using the Visual Studio interface, rather than from the command prompt. Actually I would rather do it from the command prompt, but I was not sure how to. Anyhow, I got the library compiled, and I now want to compile a program using the library, from the command prompt. The program I am trying to compile, has been tested on a linux system, where I compile it with the following c++ -I/appl/htopopt/Linux_x86_64/NTL-5.4.2/include mpqs.cpp main.cpp -o main -L/appl/htopopt/Linux_x86_64/NTL-5.4.2/lib -lntl -L/appl/htopopt/Linux_x86_64/gmp-4.2.1/lib -lgmp -lm Nevermind the gmp stuff, I dont have that installed on Windows. It is purely an optional thing that will make the NTL run faster. Anyhow, this works fine on linux. Now on Windows I write the following cl /EHsc /I D:\Downloads\WinNTL-5_5_2\include mpqs.cpp main.cpp /link /LIBPATH:"D:\Documents\Visual Studio 2008\Projects\ntl\Debug" But this results in the following errors: mpqs.cpp mpqs.cpp(38) : error C2039: 'find_smooth_vals' : is not a member of 'QS' d:\desktop\qs\mpqs.h(12) : see declaration of 'QS' mpqs.cpp(41) : error C2065: 'M' : undeclared identifier mpqs.cpp(41) : error C2065: 'n' : undeclared identifier mpqs.cpp(42) : error C2065: 'sieve_table' : undeclared identifier mpqs.cpp(42) : error C2228: left of '.size' must have class/struct/union type is ''unknown-type'' mpqs.cpp(43) : error C2065: 'sieve_table' : undeclared identifier mpqs.cpp(44) : error C2065: 'qx_table' : undeclared identifier mpqs.cpp(44) : error C3861: 'test_smoothness': identifier not found mpqs.cpp(45) : error C2065: 'smooth_indices' : undeclared identifier mpqs.cpp(45) : error C2228: left of '.push_back' must have class/struct/union type is ''unknown-type'' main.cpp Generating Code... It is as if, my mpqs.h file is not included into the compilation process? Also I dont understand why it complains about .push_back() for a vector type? Help is much appreciated!

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• Insert a datetime value with GetDate() function to a SQL server (2005) table?

  - by David.Chu.ca

  I am working (or fixing bugs) on an application which was developed in VS 2005 C#. The application saves data to a SQL server 2005. One of insert SQL statement tries to insert a time-stamp value to a field with GetDate() TSQL function as date time value. Insert into table1 (field1, ... fieldDt) values ('value1', ... GetDate()); The reason to use GetDate() function is that the SQL server may be at a remove site, and the date time may be in a difference time zone. Therefore, GetDate() will always get a date from the server. As the function can be verified in SQL Management Studio, this is what I get: SELECT GetDate(), LEN(GetDate()); -- 2010-06-10 14:04:48.293 19 One thing I realize is that the length is not up to the milliseconds, i.e., 19 is actually for '2010-06-10 14:04:48'. Anyway, the issue I have right now is that after the insert, the fieldDt actually has a date time value up to minutes, for example, '2010-06-10 14:04:00'. I am not sure why. I don't have permission to update or change the table with a trigger to update the field. My question is that how I can use a INSERT T-SQL to add a new row with a date time value ( SQL server's local date time) with a precision up to milliseconds?

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• What are some good ways to store performance statistics in a database for querying later?

  - by Nathan

  Goal: Store arbitrary performance statistics of stuff that you care about (how many customers are currently logged on, how many widgets are being processed, etc.) in a database so that you can understand what how your servers are doing over time. Assumptions: A database is already available, and you already know how to gather the information you want and are capable of putting it in the database however you like. Some Ideal Attributes of a Solution Causes no noticeable performance hit on the server being monitored Has a very high precision of measurement Does not store useless or redundant information Is easy to query (lends itself to gathering/displaying useful information) Lends itself to being graphed easily Is accurate Is elegant Primary Questions 1) What is a good design/method/scheme for triggering the storing of statistics? 2) What is a good database design for how to actually store the data? Example answers...that are sort of vague and lame... 1) I could, once per [fixed time interval], store a row of data with all the performance measurements I care about in each column of one big flat table indexed by timestamp and/or server. 2) I could have a daemon monitoring performance stuff I care about, and add a row whenever something changes (instead of at fixed time intervals) to a flat table as in #1. 3) I could trigger either as in #2, but I could store information about each aspect of performance that I'm measuring in separate tables, opening up the possibility of adding tons of rows for often-changing items, and few rows for seldom-changing items. Etc. In the end, I will implement something, even if it's some super-braindead approach I make up myself, but I'm betting there are some really smart people out there willing to share their experiences and bright ideas!

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• Putting BigDecimal data into HSQLDB test database using DbUnit

  - by Denise

  Hi everyone, I'm using Hibernate JPA in my backend. I am writing a unit test using JUnit and DBUnit to insert a set of data into an in-memory HSQL database. My dataset contains: <order_line order_line_id="1" quantity="2" discount_price="0.3"/> Which maps to an OrderLine Java object where the discount_price column is defined as: @Column(name = "discount_price", precision = 12, scale = 2) private BigDecimal discountPrice; However, when I run my test case and assert that the discount price returned equals 0.3, the assertion fails and says that the stored value is 0. If I change the discount_price in the dataset to be 0.9, it rounds up to 1. I've checked to make sure HSQLDB isn't doing the rounding and it definitely isn't because I can insert an order line object using Java code with a value like 5.3 and it works fine. To me, it seems like DBUtils is for some reason rounding the number I've defined. Is there a way I can force this to not happen? Can anyone explain why it might be doing this? Thanks!

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• Scala and Java BigDecimal

  - by geejay

  I want to switch from Java to a scripting language for the Math based modules in my app. This is due to the readability, and functional limitations of mathy Java. For e.g, in Java I have this: BigDecimal x = new BigDecimal("1.1"); BigDecimal y = new BigDecimal("1.1"); BigDecimal z = x.multiply(y.exp(new BigDecimal("2")); As you can see, without BigDecimal operator overloading, simple formulas get complicated real quick. With doubles, this looks fine, but I need the precision. I was hoping in Scala I could do this: var x = 1.1; var y = 0.1; print(x + y); And by default I would get decimal-like behaviour, alas Scala doesn't use decimal calculation by default. Then I do this in Scala: var x = BigDecimal(1.1); var y = BigDecimal(0.1); println(x + y); And I still get an imprecise result. Is there something I am not doing right in Scala? Maybe I should use Groovy to maximise readability (it uses decimals by default)?

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• Can shared memory be read and validated without mutexes?

  - by Bribles

  On Linux I'm using shmget and shmat to setup a shared memory segment that one process will write to and one or more processes will read from. The data that is being shared is a few megabytes in size and when updated is completely rewritten; it's never partially updated. I have my shared memory segment laid out as follows: ------------------------- | t0 | actual data | t1 | ------------------------- where t0 and t1 are copies of the time when the writer began its update (with enough precision such that successive updates are guaranteed to have differing times). The writer first writes to t1, then copies in the data, then writes to t0. The reader on the other hand reads t0, then the data, then t1. If the reader gets the same value for t0 and t1 then it considers the data consistent and valid, if not, it tries again. Does this procedure ensure that if the reader thinks the data is valid then it actually is? Do I need to worry about out-of-order execution (OOE)? If so, would the reader using memcpy to get the entire shared memory segment overcome the OOE issues on the reader side? (This assumes that memcpy performs it's copy linearly and ascending through the address space. Is that assumption valid?)

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• Lookup table size reduction

  - by Ryan

  Hello: I have an application in which I have to store a couple of millions of integers, I have to store them in a Look up table, obviously I cannot store such amount of data in memory and in my requirements I am very limited I have to store the data in an embebedded system so I am very limited in the space, so I would like to ask you about recommended methods that I can use for the reduction of the look up table. I cannot use function approximation such as neural networks, the values needs to be in a table. The range of the integers is not known at the moment. When I say integers I mean a 32 bit value. Basically the idea is use some copmpression method to reduce the amount of memory but without losing many precision. This thing needs to run in hardware so the computation overhead cannot be very high. In my algorithm I have to access to one value of the table do some operations with it and after update the value. In the end what I should have is a function which I pass an index to it and then I get a value, and after I have to use another function to write a value in the table. I found one called tile coding http://www.cs.ualberta.ca/~sutton/book/8/node6.html, this one is based on several look up tables, does anyone know any other method?. Thanks.

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• How best to deal with warning c4305 when type could change?

  - by identitycrisisuk

  I'm using both Ogre and NxOgre, which both have a Real typedef that is either float or double depending on a compiler flag. This has resulted in most of our compiler warnings now being: warning C4305: 'argument' : truncation from 'double' to 'Ogre::Real' When initialising variables with 0.1 for example. Normally I would use 0.1f but then if you change the compiler flag to double precision then you would get the reverse warning. I guess it's probably best to pick one and stick with it but I'd like to write these in a way that would work for either configuration if possible. One fix would be to use #pragma warning (disable : 4305) in files where it occurs, I don't know if there are any other more complex problems that can be hidden by not having this warning. I understand I would push and pop these in header files too so that they don't end up spreading across code. Another is to create some macro based on the accuracy compiler flag like: #if OGRE_DOUBLE_PRECISION #define INIT_REAL(x) (x) #else #define INIT_REAL(x) static_cast<float>( x ) #endif which would require changing all the variable initialisation done so far but at least it would be future proof. Any preferences or something I haven't thought of?

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• Creating a function in Postgresql that does not return composite values

  - by celenius

  I'm learning how to write functions in Postgresql. I've defined a function called _tmp_myfunction() which takes in an id and returns a table (I also define a table object type called _tmp_mytable) -- create object type to be returned CREATE TYPE _tmp_mytable AS ( id integer, cost double precision ); -- create function which returns query CREATE OR REPLACE FUNCTION _tmp_myfunction( id integer ) RETURNS SETOF _tmp_mytable AS $$ BEGIN RETURN QUERY SELECT id, cost FROM sales WHERE id = sales.id; END; $$ LANGUAGE plpgsql; This works fine when I use one id and call it using the following approach: SELECT * FROM _tmp_myfunction(402); What I would like to be able to do is to call it, but to use a column of values instead of just one value. However, if I use the following approach I end up with all values of the table in one column, separated by commas: -- call function using all values in a column SELECT _tmp_myfunction(t.id) FROM transactions as t; I understand that I can get the same result if I use SELECT _tmp_myfunction(402); instead of SELECT * FROM _tmp_myfunction(402); but I don't know how to construct my query in such a way that I can separate out the results.

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• Does "epsilon" really guarantees anything in floating-point computations?!

  - by Michal Czardybon

  To make the problem short let's say I want to compute expression: a / (b - c) on float's. To make sure the result is meaningful, I can check if 'b' and 'c' are inequal: float eps = std::numeric_limits<float>::epsilon(); if ((b - c) > EPS || (c - b) > EPS) { return a / (b - c); } but my tests show it is not enough to guarantee either meaningful results nor not failing to provide a result if it is possible. Case 1: a = 1.0f; b = 0.00000003f; c = 0.00000002f; Result: The if condition is NOT met, but the expression would produce a correct result 100000008 (as for the floats' precision). Case 2: a = 1e33f; b = 0.000003; c = 0.000002; Result: The if condition is met, but the expression produces not a meaningful result +1.#INF00. I found it much more reliable to check the result, not the arguments: const float INF = numeric_limits<float>::infinity(); float x = a / (b - c); if (-INF < x && x < INF) { return x; } But what for is the epsilon then and why is everyone saying epsilon is good to use?

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• What can i use to journal writes to file system

  - by Dmitry

  Hello, all I need to track all writes to files in order to have synchronized version of files on different place (server or just other directory, not considerable). Let it: all files located in same directory feel free to create some system files (e.g. SomeFileName.Ext~temp-data) no one have concurrent access to synced directory; nobody spoil ours meta-files or change real-files before we do postponed writes (like a commits) do not to care recovering "local" changes in case of crash; system can just rolled back to state of "server" by simple copy from it significant to have it transparent to use (so programmer must just call ordinary fopen(), read(), write()) It must be guaranteed that copy of files which "server" have is consistent. That is whole files scope existed in some moment of time. They may be sufficiently outdated but it must be fair snapshot of all files at some time. As i understand i should overload writing logic to collect data in order sent changes to "server". For example writing to temporary File~tmp. And so i have to overload reads in order program could read actual data of file. It would be great if you suggest some existing library (java or c++, it is unimportant) or solution (VCS customizing?). Or give hints how should i write it by myself. edit: After some reading i have more precision requirements: I need COW (Copy-on-write) wrapper for fopen(),fwrite(),.. or interceptor (hook) WriteFile() and other FS api system calls. Log-structured file system in userspace would be a alternative too.

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• Problem convert column values from VARCHAR(n) to DECIMAL

  - by Kevin Babcock

  I have a SQL Server 2000 database with a column of type VARCHAR(255). All the data is either NULL, or numeric data with up to two points of precision (e.g. '11.85'). I tried to run the following T-SQL query but received the error 'Error converting data type varchar to numeric' SELECT CAST([MyColumn] AS DECIMAL) FROM [MyTable]; I tried a more specific cast, which also failed. SELECT CAST([MyColumn] AS DECIMAL(6,2)) FROM [MyTable]; I also tried the following to see if any data is non-numeric, and the only values returned were NULL. SELECT ISNUMERIC([MyColumn]), [MyColumn] FROM [MyTable] WHERE ISNUMERIC([MyColumn]) = 0; I tried to convert to other data types, such as FLOAT and MONEY, but only MONEY was successful. So I tried the following: SELECT CAST(CAST([MyColumn] AS MONEY) AS DECIMAL) FROM [MyTable]; ...which worked just fine. Any ideas why the original query failed? Will there be a problem if I first convert to MONEY and then to DECIMAL? Thanks!

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• How do I make this nested for loop, testing sums of cubes, more efficient?

  - by Brian J. Fink

  I'm trying to iterate through all the combinations of pairs of positive long integers in Java and testing the sum of their cubes to discover if it's a Fibonacci number. I'm currently doing this by using the value of the outer loop variable as the inner loop's upper limit, with the effect being that the outer loop runs a little slower each time. Initially it appeared to run very quickly--I was up to 10 digits within minutes. But now after 2 full days of continuous execution, I'm only somewhere in the middle range of 15 digits. At this rate it may end up taking a whole year just to finish running this program. The code for the program is below: import java.lang.*; import java.math.*; public class FindFib { public static void main(String args[]) { long uLimit=9223372036854775807L; //long maximum value BigDecimal PHI=new BigDecimal(1D+Math.sqrt(5D)/2D); //Golden Ratio for(long a=1;a<=uLimit;a++) //Outer Loop, 1 to maximum for(long b=1;b<=a;b++) //Inner Loop, 1 to current outer { //Cube the numbers and add BigDecimal c=BigDecimal.valueOf(a).pow(3).add(BigDecimal.valueOf(b).pow(3)); System.out.print(c+" "); //Output result //Upper and lower limits of interval for Mobius test: [c*PHI-1/c,c*PHI+1/c] BigDecimal d=c.multiply(PHI).subtract(BigDecimal.ONE.divide(c,BigDecimal.ROUND_HALF_UP)), e=c.multiply(PHI).add(BigDecimal.ONE.divide(c,BigDecimal.ROUND_HALF_UP)); //Mobius test: if integer in interval (floor values unequal) Fibonacci number! if (d.toBigInteger().compareTo(e.toBigInteger())!=0) System.out.println(); //Line feed else System.out.print("\r"); //Carriage return instead } //Display final message System.out.println("\rDone. "); } } Now the use of BigDecimal and BigInteger was delibrate; I need them to get the necessary precision. Is there anything other than my variable types that I could change to gain better efficiency?

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• Increasing time resolution of BOOST::progress timer

  - by feelfree

  BOOST::progress_timer is a very useful class to measure the running time of a function. However, the default implementation of progress_timer is not accurate enough and a possible way of increasing time resolution is to reconstruct a new class as the following codes show: #include <boost/progress.hpp> #include <boost/static_assert.hpp> template<int N=2> class new_progress_timer:public boost::timer { public: new_progress_timer(std::ostream &os=std::cout):m_os(os) { BOOST_STATIC_ASSERT(N>=0 &&N<=10); } ~new_progress_timer(void) { try { std::istream::fmtflags old_flags = m_os.setf(std::istream::fixed,std::istream::floatfield); std::streamsize old_prec = m_os.precision(N); m_os<<elapsed()<<"s\n" <<std::endl; m_os.flags(old_flags); m_os.precison(old_prec); } catch(...) { } } private: std::ostream &m_os; }; However, when I compile the codes with VC10, the following error appear: 'precison' : is not a member of 'std::basic_ostream<_Elem,_Traits>' Any ideas? Thanks.

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• How to convert Big Endian and how to flip the highest bit?

  - by Robert Frank

  I am using a TStream to read binary data (thanks to this post: http://stackoverflow.com/questions/2878180/how-to-use-a-tfilestream-to-read-2d-matrices-into-dynamic-array). My next problem is that the data is Big Endian. From my reading, the Swap() method is seemingly deprecated. How would I swap the types below? 16-bit two's complement binary integer 32-bit two's complement binary integer 64-bit two's complement binary integer IEEE single precision floating-point - Are IEEE affected by Big Endian? And, finally, since the data is unsigned, the creators of this dataset have stored the unsigned values as signed integers (excluding the IEEE). They instruct that one need only add an offset (2^15, 2^31, and 2^63) to recover the unsigned data. But, they note that flipping the most significant bit is the fastest way to do that. How does one efficiently flip the most significant bit of a 16, 32, or 64-bit integer? So, if the data on disk (16-bit) is "85 FB" - the desired result after reading the data and swapping and bit flipping would be 1531. Is there a way to accomplish the swapping and bit flipping with generics so it fits into the generic answer at the link above? Yes, kids, THIS is how scientific astronomical data is stored by NASA, ESO, and all professional astronomers. This FITS standard is considered by some to be one of the most successful standards ever created in its proliferation and flexibility!

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• Out-of-memory algorithms for addressing large arrays

  - by reve_etrange

  I am trying to deal with a very large dataset. I have k = ~4200 matrices (varying sizes) which must be compared combinatorially, skipping non-unique and self comparisons. Each of k(k-1)/2 comparisons produces a matrix, which must be indexed against its parents (i.e. can find out where it came from). The convenient way to do this is to (triangularly) fill a k-by-k cell array with the result of each comparison. These are ~100 X ~100 matrices, on average. Using single precision floats, it works out to 400 GB overall. I need to 1) generate the cell array or pieces of it without trying to place the whole thing in memory and 2) access its elements (and their elements) in like fashion. My attempts have been inefficient due to reliance on MATLAB's eval() as well as save and clear occurring in loops. for i=1:k [~,m] = size(data{i}); cur_var = ['H' int2str(i)]; %# if i == 1; save('FileName'); end; %# If using a single MAT file and need to create it. eval([cur_var ' = cell(1,k-i);']); for j=i+1:k [~,n] = size(data{j}); eval([cur_var '{i,j} = zeros(m,n,''single'');']); eval([cur_var '{i,j} = compare(data{i},data{j});']); end save(cur_var,cur_var); %# Add '-append' when using a single MAT file. clear(cur_var); end The other thing I have done is to perform the split when mod((i+j-1)/2,max(factor(k(k-1)/2))) == 0. This divides the result into the largest number of same-size pieces, which seems logical. The indexing is a little more complicated, but not too bad because a linear index could be used. Does anyone know/see a better way?

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• Tips for submitting a library to Boost?

  - by AraK

  Hi everyone, Summer is coming, and a group of friends and I are getting ready for it :) We decided to build a compile-time Arbitrary precision Unsigned Integers. We would like to provide a set of integers algorithms(functions) with the library. We have seen a number of requests for such a library(SoC2010, C++0x Standard Library wishlist). Also, a regular run-time bigint is requested usually with that, but we don't want to go into the hassle of memory management. The idea came to me from a library called TTMath, unfortunately this library works only on specific platforms because Assembly was used extensively in the library. We would like to write a standard library, depending on the C++ standard library and Boost. Also, we would like to use the available C++0x facilities in current compilers like user-defined literals and others. This would technically make the library non-standard for a while, but we think that it is a matter of time the new standards will be official. Your hints on the whole process including design, implementation, documentation, maintainable of the library are more than welcom. We are a group of students and fresh graduates who are looking for something interesting in the summer, but we see that Boost is full of gurus and we don't want to forget something too obvious. We are communicating on-line, so there is no shared white-boards :( Thanks,

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