Search Results

Search found 1806 results on 73 pages for 'numeric precision'.

Page 56/73 | < Previous Page | 52 53 54 55 56 57 58 59 60 61 62 63  | Next Page >

  • 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)?

    Read the article

  • 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?)

    Read the article

  • 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.

    Read the article

  • Difficult to point-and-click target with Apple Magic Trackpad?

    - by Andrew Swift
    My Magic Trackpad is great for most things involving dragging and gestures, but for simple point-and-click use it is starting to get really annoying. For example, my bank has a numeric code that I need to enter from a visual grid on the screen, by clicking on the six numbers in order. To do this is quite difficult with the Magic Trackpad. Idea 1: it is because when you start dragging on the touchpad, there is a brief delay before the mouse starts to move. The delay might be enough to screw up my anticipation of where the cursor is going to go. Idea 2: it may have to do with the cursor acceleration. If I move it a little, the cursor moves a little. If I move it a lot, it goes much faster. I have tried various settings in the preference pane, and although the cursor does move more or less quickly, it doesn't seem any more or less easy to hit a given target. As I am writing this post, I tried a brief experiment -- I chose a spot on the page (the bracket in the superuser logo) and tried to move the cursor there in one quick movement. It's extremely difficult, even though I've been using Macs and touchpads since 1999. There is something about the behavior of the trackpad that is making it impossible for me to learn how to accurately predict where the cursor will end up. Does anyone else have this problem?

    Read the article

  • 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?

    Read the article

  • 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.

    Read the article

  • 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?

    Read the article

  • 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.

    Read the article

  • Spreadsheet application that can handle big data OS X

    - by Peter
    I've been working with Excel for quite a while for some statistical analysis that I do regularly. The size of the data that I'm working with has gotten much larger as of late, however. The layout of the databases in question is quite simple, usually just three rows which includes a UNIX timestamp, and EST value, a proprietary numeric value and finally an average of the rows that have a timestamp +/- 1000 that row's timestamp (little AVERAGEIFS() formula). That formula and the EST conversion are the only formulas in the sheet. I'm beginning to work with files with 500,000+ rows. Running the average formula down the entire row takes forever. The end result is the production of print-worthy graphs. I'm looking for either a UNIX CL utility or separate spreadsheet/database application that can handle this amount of data without melting my CPU or making me wait an hour. Is there anything out there? TL;DR: Simple excel sheet with over half a million rows is getting too slow to work with. OS X alternatives?

    Read the article

  • Difficult to point-and-click target with Apple Magic Trackpad?

    - by Andrew Swift
    My Magic Trackpad is great for most things involving dragging and gestures, but for simple point-and-click use it is starting to get really annoying. For example, my bank has a numeric code that I need to enter from a visual grid on the screen, by clicking on the six numbers in order. To do this is quite difficult with the Magic Trackpad. Idea 1: it is because when you start dragging on the touchpad, there is a brief delay before the mouse starts to move. The delay might be enough to screw up my anticipation of where the cursor is going to go. Idea 2: it may have to do with the cursor acceleration. If I move it a little, the cursor moves a little. If I move it a lot, it goes much faster. I have tried various settings in the preference pane, and although the cursor does move more or less quickly, it doesn't seem any more or less easy to hit a given target. As I am writing this post, I tried a brief experiment -- I chose a spot on the page (the bracket in the superuser logo) and tried to move the cursor there in one quick movement. It's extremely difficult, even though I've been using Macs and touchpads since 1999. There is something about the behavior of the trackpad that is making it impossible for me to learn how to accurately predict where the cursor will end up. Does anyone else have this problem?

    Read the article

  • 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?

    Read the article

  • 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.

    Read the article

  • 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!

    Read the article

  • moving files and directories between two machine, via a third, preserving permissions and usernames

    - by Jarmund
    The situation is as follows: Machine A has a file repository accessible via rsync Machine B needs the above mentioned files with all permissions and ownerships intact (including groups etc) Machine C has access to both A and B, but has a completely different set of users. Normally, i would just rsync everything over, directly between A and B, but due to severely limited bandwidth at the moment, i need something different, as rsync times out after building the list of the 430 files (49Mb uncompressed... can be compressed down to ~7Mb). What i've tried so far: rsync everything over from A to C, tar it, copy the tarball over, and then untar it, however, this messes up the ownership and/or the permissions. To rsync it from A to C, i run this command: rsync --numeric-ids --password-file=/root/rsync_pwd_file -oaPvu rsync://[email protected]/portal_2/ ./portal_2/ ...and from the looks of things, they do end up on C with the correct ownerships/permissions/flags/everything (not 100% sure, though.. are there any more switches i can throw in there? did i miss something?) copying the tarball over is simple enough (slow as a one-legged turtle due to the bandwidth, but it checksums out alright) What i'm unsure of is the flags and switches for creating and extracting the tarball, so could someone please provide the full commands for creating a tarball from /root/portal_2 on machine C (with everything intact) and extracting the tarball into /var/ex/portal_2 on machine B? ? Also, are there any other approaches worth mentioning that could allow me to perform this? I have root access to A and C, whereas i only have rsync access to B. PS: I'm running rsync v2.6.9 on machine B, and unfortunately i do not have the oportunity to upgrade to v3

    Read the article

  • 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?

    Read the article

  • 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,

    Read the article

  • Zend_Db Enum Values [Closed]

    - by scopus
    I find this solution $metadata = $result->getTable()->info('metadata'); echo $metadata['Continent']['DATA_TYPE']; Hi, I want to get enum values in Zend_Db. My Code: $select = $this->select(); $result = $select->fetchAll(); print_r($result->getTable()); Output: Example Object ( [_name] => country [query] => Zend_Db_Table_Select Object ( [_info:protected] => Array ( [schema] => [name] => country [cols] => Array ( [0] => Code [1] => Continent ) [primary] => Array ( [1] => Code ) [metadata] => Array ( [Continent] => Array ( [SCHEMA_NAME] => [TABLE_NAME] => country [COLUMN_NAME] => Continent [COLUMN_POSITION] => 3 [DATA_TYPE] => enum('Asia','Europe','North America','Africa','Oceania','Antarctica','South America') [DEFAULT] => Asia [NULLABLE] => [LENGTH] => [SCALE] => [PRECISION] => [UNSIGNED] => [PRIMARY] => [PRIMARY_POSITION] => [IDENTITY] => ) I see enum values in data_type but i don't get this values. How can get data_type?

    Read the article

  • How to use a TFileStream to read 2D matrices into dynamic array?

    - by Robert Frank
    I need to read a large (2000x2000) matrix of binary data from a file into a dynamic array with Delphi 2010. I don't know the dimensions until run-time. I've never read raw data like this, and don't know IEEE so I'm posting this to see if I'm on track. I plan to use a TFileStream to read one row at a time. I need to be able to read as many of these formats as possible: 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 For 32-bit two's complement, I'm thinking something like the code below. Changing to Int64 and Int16 should be straight forward. How can I read the IEEE? Am I on the right track? Any suggestions on this code, or how to elegantly extend it for all 4 data types above? Since my post-processing will be the same after reading this data, I guess I'll have to copy the matrix into a common format when done. I have no problem just having four procedures (one for each data type) like the one below, but perhaps there's an elegant way to use RTTI or buffers and then move()'s so that the same code works for all 4 datatypes? Thanks! type TRowData = array of Int32; procedure ReadMatrix; var Matrix: array of TRowData; NumberOfRows: Cardinal; NumberOfCols: Cardinal; CurRow: Integer; begin NumberOfRows := 20; // not known until run time NumberOfCols := 100; // not known until run time SetLength(Matrix, NumberOfRows); for CurRow := 0 to NumberOfRows do begin SetLength(Matrix[CurRow], NumberOfCols); FileStream.ReadBuffer(Matrix[CurRow], NumberOfCols * SizeOf(Int32)) ); end; end;

    Read the article

  • What are the hibernate annotations used to persist a Map with an enumerated type as a key?

    - by Jason Novak
    I am having trouble getting the right hibernate annotations to use on a 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?

    Read the article

  • Caching vector addition over changing collections

    - by DRMacIver
    I have the following setup: I have a largish number of uuids (currently about 10k but expected to grow unboundedly - they're user IDs) and a function f : id - sparse vector with 32-bit integer values (no need to worry about precision). The function is reasonably expensive (not outrageously so, but probably on the order of a few 100ms for a given id). The dimension of the sparse vectors should be assumed to be infinite, as new dimensions can appear over time, but in practice is unlikely to ever exceed about 20k (and individual results of f are unlikely to have more than a few hundred non-zero values). I want to support the following operations efficiently: add a new ID to the collection invalidate an existing ID retrieve sum f(id) in O(changes since last retrieval) i.e. I want to cache the sum of the vectors in a way that's reasonable to do incrementally. One option would be to support a remove ID operation and treat invalidation as a remove followed by an add. The problem with this is that it requires us to keep track of all the old values of f, which is expensive in space. I potentially need to use many instances of this sort of cached structure, so I would like to avoid that. The likely usage pattern is that new IDs are added at a fairly continuous rate and are frequently invalidated at first. Ids which have been invalidated recently are much more likely to be invalidated again than ones which have remained valid for a long time, but in principle an old Id can still be invalidated. Ideally I don't want to do this in memory (or at least I want a way that lets me save the result to disk efficiently), so an idea which lets me piggyback off an existing DB implementation of some sort would be especially appreciated.

    Read the article

  • Is there a Java data structure that is effectively an ArrayList with double indicies and built-in in

    - by Bob Cross
    I am looking for a pre-built Java data structure with the following characteristics: It should look something like an ArrayList but should allow indexing via double-precision rather than integers. Note that this means that it's likely that you'll see indicies that don't line up with the original data points (i.e., asking for the value that corresponds to key "1.5"). As a consequence, the value returned will likely be interpolated. For example, if the key is 1.5, the value returned could be the average of the value at key 1.0 and the value at key 2.0. The keys will be sorted but the values are not ensured to be monotonically increasing. In fact, there's no assurance that the first derivative of the values will be continuous (making it a poor fit for certain types of splines). Freely available code only, please. For clarity, I know how to write such a thing. In fact, we already have an implementation of this and some related data structures in legacy code that I want to replace due to some performance and coding issues. What I'm trying to avoid is spending a lot of time rolling my own solution when there might already be such a thing in the JDK, Apache Commons or another standard library. Frankly, that's exactly the approach that got this legacy code into the situation that it's in right now.... Is there such a thing out there in a freely available library?

    Read the article

  • Simulate Golf Game Strategy

    - by Mitchel Sellers
    I am working on what at best could be considered a "primitive" golf game, where after a certain bit of randomness is introduced I need to play out a hole of golf. The hole is static and I am not concerned about the UI aspect as I just have to draw a line on a graphic of the hole after the ball has been hit showing where it traveled. I'm looking for input on thoughts of how to manage the "logic" side of the puzzle, below are some of my thoughts on the matter, input, suggestions, or references are greatly appreciated. Map out the hole into an array with a specific amount of precision, noting the type of surface: out of bounds, fairway, rough, green, sand, water, and most important the hole. Map out "regions" and if the ball is contained inside one of these regions setup parameters for "maximum" angle of departure. (For example the first part of the hole the shot must be between certain angles Using the current placement of the ball, and the region contained in #2, define a routine to randomly select the shooting angle, and power then move the ball, adjust the trajectory and move again. I know this isn't the "most elegant" solution, but in reality, we are looking for a quick and dirty solution, as I just have to do this a few times, set it and forget it afterward. From a languages perspective I'll be using ASP.NET and C# to get this done.

    Read the article

  • How do NTP Servers Manage to Stay so Accurate?

    - by Akemi Iwaya
    Many of us have had the occasional problem with our computers and other devices retaining accurate time settings, but a quick sync with an NTP server makes all well again. But if our own devices can lose accuracy, how do NTP servers manage to stay so accurate? Today’s Question & Answer session comes to us courtesy of SuperUser—a subdivision of Stack Exchange, a community-driven grouping of Q&A web sites. Photo courtesy of LEOL30 (Flickr). The Question SuperUser reader Frank Thornton wants to know how NTP servers are able to remain so accurate: I have noticed that on my servers and other machines, the clocks always drift so that they have to sync up to remain accurate. How do the NTP server clocks keep from drifting and always remain so accurate? How do the NTP servers manage to remain so accurate? The Answer SuperUser contributor Michael Kjorling has the answer for us: NTP servers rely on highly accurate clocks for precision timekeeping. A common time source for central NTP servers are atomic clocks, or GPS receivers (remember that GPS satellites have atomic clocks onboard). These clocks are defined as accurate since they provide a highly exact time reference. There is nothing magical about GPS or atomic clocks that make them tell you exactly what time it is. Because of how atomic clocks work, they are simply very good at, having once been told what time it is, keeping accurate time (since the second is defined in terms of atomic effects). In fact, it is worth noting that GPS time is distinct from the UTC that we are more used to seeing. These atomic clocks are in turn synchronized against International Atomic Time or TAI in order to not only accurately tell the passage of time, but also the time. Once you have an exact time on one system connected to a network like the Internet, it is a matter of protocol engineering enabling transfer of precise times between hosts over an unreliable network. In this regard a Stratum 2 (or farther from the actual time source) NTP server is no different from your desktop system syncing against a set of NTP servers. By the time you have a few accurate times (as obtained from NTP servers or elsewhere) and know the rate of advancement of your local clock (which is easy to determine), you can calculate your local clock’s drift rate relative to the “believed accurate” passage of time. Once locked in, this value can then be used to continuously adjust the local clock to make it report values very close to the accurate passage of time, even if the local real-time clock itself is highly inaccurate. As long as your local clock is not highly erratic, this should allow keeping accurate time for some time even if your upstream time source becomes unavailable for any reason. Some NTP client implementations (probably most ntpd daemon or system service implementations) do this, and others (like ntpd’s companion ntpdate which simply sets the clock once) do not. This is commonly referred to as a drift file because it persistently stores a measure of clock drift, but strictly speaking it does not have to be stored as a specific file on disk. In NTP, Stratum 0 is by definition an accurate time source. Stratum 1 is a system that uses a Stratum 0 time source as its time source (and is thus slightly less accurate than the Stratum 0 time source). Stratum 2 again is slightly less accurate than Stratum 1 because it is syncing its time against the Stratum 1 source and so on. In practice, this loss of accuracy is so small that it is completely negligible in all but the most extreme of cases. Have something to add to the explanation? Sound off in the comments. Want to read more answers from other tech-savvy Stack Exchange users? Check out the full discussion thread here.

    Read the article

  • Adobe Photoshop CS5 vs Photoshop CS5 extended

    - by Edward
    Adobe Photoshop has been an industry standard for most web designers & photographers worldwide. Photoshop CS5 has made photography editing much more refined and the composition process has become much easier than ever before.  To study the advantage of Photoshop CS5 extended over Photoshop CS5 we have written this comparison article, with both a Designer’s & Photographer’s perspective. Hopefully it shall help you in your buying/upgrade decision. Photoshop CS5 Photoshop CS5 has refining feature with powerful photography tools. It made editing process easy as fewer steps are involved to remove noise, add grain, create vignettes, correct lens distortions, sharpen, and create HDR images. It has quick image correction and color and tone control for professional purpose. Intelligent image editing and enhancement , extraordinary advanced compositing has made it a better tool than earlier versions for photographers. It allows users to accelerate workflow with fast performance on 64-bit Windows® and Mac hardware systems and smoother interactions due to more GPU-accelerated features. It also boasts of a state-of-the-art processing with Adobe Photoshop Camera Raw 6 and helps to maximize creative impact. It provides for tremendous precision and freedom. It allows user to easily select intricate image elements, such as hair and create realistic painting effects. It also allows to remove any image element and see the space fill in almost magically. It has easy access to core editing and streamlined work flow and flexible work ambience. It has creative tools and contents. Photoshop CS5 Extended Photoshop CS5 extended is quite innovative and has incorporated 3D elements to 2D artwork directly within digital imaging application, which enables user to do an easy on-ramp to 3D image creation. It also provides for 3D editing. It has intelligent image editing and enhancement. It offers advance composing and has extraordinary painting and drawing toolset. It provides for video and animation designing. It helps to work with specialized images for architecture, manufacturing, engineering, science, and medicine. Where CS5 extended scores over CS5 CS5 extended has many features, which were not included in CS5. These features make it score more over CS5. These features are: Technology for creating 3D extrusion 3D material library and picker Field depth for 3D 3D merging and scene composition improvements 3D workflow improvement Customization of 3D features Image based light source Shadow catcher for shadow creation Enhanced ray tracer Context sensitive widgets, which allows easy control of objects, lights and cameras. Overlays for materials and mesh boundaries Photoshop CS5 extended is far better than CS5 as it incorporates all the features of CS5 and have more advanced features. It allows 3D creation and editing and has other advanced tools to make it better. Redefining the Image-Editing Experience  : A Photographer’s point of View Photoshop CS5 delivers amazing features and creative options so even new users can perform advanced image manipulations and compositions. Breath taking image intelligence behind Content-Aware Fill magically removes any image detail or object, examines the surroundings and seamlessly fills in the space left behind. Lighting, tone and noise of the surrounding area can be matched. New Refine Edge makes nearly-impossible image selections possible. Masking was never easier, the toughest types of edges, such as hair and foliage seem easier to fix. To sum up following are few advantages of CS5 extended over previous versions 64-bit processing Content Aware Fill Refine Edge, “makes nearly-impossible image selections impossible” HDR Pro, including ghost artifact removal and HDR toning, which gives the look of HDR with a single exposure New brush options Improved image management with enhanced Adobe Bridge Lens corrections Improved black-and-white conversions Puppet Warp: Precisely reposition or warp any image element Adobe Camera Raw 6 Upgrade Buy Online Pricing and Availability Adobe Photoshop CS5 and CS5 Extended are available through Adobe Authorized Resellers & the Adobe Store. Estimated street price for Adobe Photoshop CS5 is US$699 and US$999 for Photoshop CS5 Extended. Upgrade pricing and volume licensing are also available. Related posts:10 Free Alternatives for Adobe Photoshop Software Web based Alternatives to Photoshop 15 Useful Adobe Illustrator Tutorials For Designers

    Read the article

  • Code is not the best way to draw

    - by Bertrand Le Roy
    It should be quite obvious: drawing requires constant visual feedback. Why is it then that we still draw with code in so many situations? Of course it’s because the low-level APIs always come first, and design tools are built after and on top of those. Existing design tools also don’t typically include complex UI elements such as buttons. When we launched our Touch Display module for Netduino Go!, we naturally built APIs that made it easy to draw on the screen from code, but very soon, we felt the limitations and tedium of drawing in code. In particular, any modification requires a modification of the code, followed by compilation and deployment. When trying to set-up buttons at pixel precision, the process is not optimal. On the other hand, code is irreplaceable as a way to automate repetitive tasks. While tools like Illustrator have ways to repeat graphical elements, they do so in a way that is a little alien and counter-intuitive to my developer mind. From these reflections, I knew that I wanted a design tool that would be structurally code-centric but that would still enable immediate feedback and mouse adjustments. While thinking about the best way to achieve this goal, I saw this fantastic video by Bret Victor: The key to the magic in all these demos is permanent execution of the code being edited. Whenever a parameter is being modified, everything is re-executed immediately so that the impact of the modification is instantaneously visible. If you do this all the time, the code and the result of its execution fuse in the mind of the user into dual representations of a single object. All mental barriers disappear. It’s like magic. The tool I built, Nutshell, is just another implementation of this principle. It manipulates a list of graphical operations on the screen. Each operation has a nice editor, and translates into a bit of code. Any modification to the parameters of the operation will modify the bit of generated code and trigger a re-execution of the whole program. This happens so fast that it feels like the drawing reacts instantaneously to all changes. The order of the operations is also the order in which the code gets executed. So if you want to bring objects to the front, move them down in the list, and up if you want to move them to the back: But where it gets really fun is when you start applying code constructs such as loops to the design tool. The elements that you put inside of a loop can use the loop counter in expressions, enabling crazy scenarios while retaining the real-time edition features. When you’re done building, you can just deploy the code to the device and see it run in its native environment: This works thanks to two code generators. The first code generator is building JavaScript that is executed in the browser to build the canvas view in the web page hosting the tool. The second code generator is building the C# code that will run on the Netduino Go! microcontroller and that will drive the display module. The possibilities are fascinating, even if you don’t care about driving small touch screens from microcontrollers: it is now possible, within a reasonable budget, to build specialized design tools for very vertical applications. Direct feedback is a powerful ally in many domains. Code generation driven by visual designers has become more approachable than ever thanks to extraordinary JavaScript libraries and to the powerful development platform that modern browsers provide. I encourage you to tinker with Nutshell and let it open your eyes to new possibilities that you may not have considered before. It’s open source. And of course, my company, Nwazet, can help you develop your own custom browser-based direct feedback design tools. This is real visual programming…

    Read the article

< Previous Page | 52 53 54 55 56 57 58 59 60 61 62 63  | Next Page >