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Search found 680 results on 28 pages for 'precision'.

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• How do I draw an ellipse with arbitrary orientation pixel by pixel?

  - by amc

  Hi, I have to draw an ellipse of arbitrary size and orientation pixel by pixel. It seems pretty easy to draw an ellipse whose major and minor axes align with the x and y axes, but rotating the ellipse by an arbitrary angle seems trickier. Initially I though it might work to draw the unrotated ellipse and apply a rotation matrix to each point, but it seems as though that could cause errors do to rounding, and I need rather high precision. Is my suspicion about this method correct? How could I accomplish this task more precisely? I'm programming in C++ (although that shouldn't really matter since this is a more algorithm-oriented question).

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• Rails - Format number as currency format in the Getter

  - by daemonsy

  I am making a simple retail commerce solution, where there are prices in a few different models. These prices contribute to a total price. Imagine paying $0.30 more for selecting a topping for your yogurt. When I set the price field to t.decimal :price, precision:8, scale:2 The database stores 6.50 as 6.5. I know in the standard rails way, you call number_to_currency(price) to get the formatted value in the Views. I need to programmatically call the price field as well formatted string, i.e. $6.50 a few places that are not directly part of the View. Also, my needs are simple (no currency conversion etc), I prefer to have the price formatted universally in the model without repeated calling number_to_currency in views. Is there a good way I can modify my getter for price such that it always returns two decimal place with a dollar sign, i.e. $6.50 when it's called? Thanks in advance.

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• SQL CLR and nullable datetime parameter

  - by toluca70

  I'm trying to write a SQLCLR function that takes a DateTime2 as input and returns another DateTime2. Based on this post I altered the parameter to be the C# type DateTime giving me the level of precision I require. However because the input can be null I would like it to be DateTime?; the return type as well. using System; using Microsoft.SqlServer.Server; namespace SqlServer.Functions { public class UserDefinedFunctions { [SqlFunction(DataAccess = DataAccessKind.None)] public static DateTime? GetLocalTimeFromGMT(DateTime? dateTime) { if (dateTime.HasValue) return DateTime.SpecifyKind(dateTime.Value, DateTimeKind.Utc).ToLocalTime(); else return (DateTime?)null; } } } The problem is I get the following error when I try to deploy: Error 1 Cannot find the type 'Nullable`1', because it does not exist or you do not have permission. SqlServer.Functions I'm using Sql Server 2008 and Visual Studio 2008.

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• GPU Computing - # of GPUs supported

  - by TehTypoKing

  I currently have a desktop with 6 GPUs ( 3x HD 5970s ) in non-crossfire mode. Unfortunately, it seems that Windows 7 64bit only supports up to 4 GPUs. I have not been able to find a reliable source to deny or confirm this. If windows 7 has this limitation, is there a Linux flavor that supports more than 4 GPUs? In-case you are wondering, this is not for gaming but high-speed single precision computing. With this current setup ( if I can find 6gpu support ) I am looking to reach 13.8 Teraflops. Also, my motherboard does support 3 16x pci-xpress gen2 slots... and I have a 1500w powersupply plugged into a 20amp outlet. Windows is able to detect all 6 cores.. although, 2 of which displays the warning "Drivers failed to load". To recap: - Can windows support 6 GPUs? - If not, does Linux? Thank you.

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• Fastest implementation of the frac function in C#

  - by user349937

  I would like to implement a frac function in C# (just like the one in hsl here http://msdn.microsoft.com/en-us/library/bb509603%28VS.85%29.aspx) but since it is for a very processor intensive application i would like the best version possible. I was using something like public float Frac(float value) { return value - (float)Math.Truncate(value); } but I'm having precision problems, for example for 2.6f it's returning in the unit test Expected: 0.600000024f But was: 0.599999905f I know that I can convert to decimal the value and then at the end convert to float to obtain the correct result something like this: public float Frac(float value) { return (float)((decimal)value - Decimal.Truncate((decimal)value)); } But I wonder if there is a better way without resorting to decimals...

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• Integers in JavaScript

  - by muntoo

  I'm a beginner to Javascript so forgive me if I sound dumb because I learned some Javascript from W3Fools (which are really difficult tutorials - they don't explain anything I want to know, but everything I probably can guess from my experience with C++). I may be switching over to MDN, but if you can recommend any other tutorials, that be great. Anyways, so here's my question: I just read a few lines of this, and apparently: Numbers in JavaScript are "double-precision 64-bit format IEEE 754 values", according to the spec. This has some interesting consequences. There's no such thing as an integer in JavaScript, so you have to be a little careful with your arithmetic if you're used to math in C or Java. I've already seen that there are few of the data types (for variables) I'm used to from C++. But I didn't expect all numbers to automatically be floats. Isn't there any way to use integers, not float? Will a future version of JavaScript support ints?

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• precise geolocalization via IP

  - by meo

  I tied the iPad the other day, and was amazed about the precision of the geolocalization by ip. Actually there is this action against hunger in the world that shows you very precisely where the persons are located that have took part to this petition: http://www.1billionhungry.org/meodai/impact/ I would like to integrate that in one of my projects. I took a look at the source but i could not figure out how they did it. Can someone help me out? is there a web service for that? Is the google map api doing this or are they using an other service? PS: Its not just the country/region of your IP/ISP IP that the service gives back, its a pretty precise positioning.

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• Why are there so many floats in the Android API?

  - by Brian

  The default floating point type in Java is the double. If you hard code a constant like 2.5 into your program, Java makes it a double automatically. When you do an operation on floats or ints that could potentially benefit from more precision, the type is 'promoted' to a double. But in the Android API, everything seems to be a float from sound volumes to rectangle coordinates. There's a structure called RectF used in most drawing; the F is for float. It's really a pain for programmers who are casting promoted doubles back to (float) pretty often. Don't we all agree that Java code is messy and verbose enough as it is? Usually math coprocessors and accelerators prefer double in Java because it corresponds to one of the internal types. Is there something about Android's Dalvik VM that prefers floats for some reason? Or are all the floats just a result of perversion in API design?

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• For simple C cmd programs: how to add "program executed in 12,345 seconds" ?

  - by WoodsieLord

  I'm a windows user, and I'm learning C. I use Codeblocks and visual c++ 2008 express at home to write simple C command line programs (I'm a beginner) and I find really useful when codeblocks adds a few lines at the end with the time it takes (example: "Process returned 0 (0x0) execution time : 6.848 s"). I want to add this functionality to the .exe so I can 'benchmark' or 'test' the program on a few computers. I tried using time(NULL) but it only works with 1 second precision. I also found very interesting answers here (I'm actually looking for the same thing): http://stackoverflow.com/questions/2173323/calculating-time-by-the-c-code The solution proposed by Mark Wilkins, works fine on visual c++ 2008 express on my windows 64 bit PC, but the .exe does not work anywhere else. Am I doing something wrong? I would like a method to count elapsed wall time for my programs, that must have 32bit compatibility. Thanks in advance!

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• Java Formatter specify starting position for text

  - by purecharger

  I'm trying to position a string at a certain starting position on a line, regardless of where the previous text ended. For instance: Mandatory arguments to long options are mandatory for short options too. -a, --all do not ignore entries starting with . -A, --almost-all do not list implied . and .. The explanation of the options begin at position 30 regardless of the text preceding. How do you accomplish this with java.util.Formatter? I have tested with both the width (%30s) and precision (%.30) arguments, and neither provide the desired result.

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• Floating point comparison in STL, BOOST

  - by Paul

  Is there in the STL or in Boost a set of generic simple comparison functions? The one I found are always requiring template parameters, and/or instantiation of a struct template. I'm looking for something with a syntax like : if ( is_greater(x,y) ) { ... } Which could be implemented as : template <typename T> bool is_greater(const T& x, const T& y) { return x > y + Precision<T>::eps; }

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• Cuda program results are always zero in HW, correct in EMU??

  - by Orion Nebula

  Hi all! I am having a weird problem .. I have written a CUDA code which executes correctly in emulation and all results show up.. however, when executed on hardware "G210" .. the results in the result memory are always 0 I am passing two vectors to the kernel, one with random variables the other is initialized to zero, the code copies the first vector to shared memory, does some swapping and other operations and then writes back the results on the second vector (the one with the initial 0's) I am using double precision, the -arch sm13 flag is used, all memory allocation also use sizeof(double) .. I have checked if the kernel is invoked, it does .. so no problems here .. the cudaMemCpy has no problems .. what could be the problem .. :( why would it work in emulation but not on HW I am quite confused .. any ideas?

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• Better ways to print out column names when using cx_Oracle

  - by philipjkim

  Found an example using cx_Oracle, this example shows all the information of Cursor.description. import cx_Oracle from pprint import pprint connection = cx_Oracle.Connection("%s/%s@%s" % (dbuser, dbpasswd, oracle_sid)) cursor = cx_Oracle.Cursor(connection) sql = "SELECT * FROM your_table" cursor.execute(sql) data = cursor.fetchall() print "(name, type_code, display_size, internal_size, precision, scale, null_ok)" pprint(cursor.description) pprint(data) cursor.close() connection.close() What I wanted to see was the list of Cursor.description[0](name), so I changed the code: import cx_Oracle import pprint connection = cx_Oracle.Connection("%s/%s@%s" % (dbuser, dbpasswd, oracle_sid)) cursor = cx_Oracle.Cursor(connection) sql = "SELECT * FROM your_table" cursor.execute(sql) data = cursor.fetchall() col_names = [] for i in range(0, len(cursor.description)): col_names.append(cursor.description[i][0]) pp = pprint.PrettyPrinter(width=1024) pp.pprint(col_names) pp.pprint(data) cursor.close() connection.close() I think there will be better ways to print out the names of columns. Please get me alternatives to the Python beginner. :-)

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• Why does C++ mandate that complex only be instantiated for float, double, or long double?

  - by templatetypedef

  According to the C++ ISO spec, §26.2/2: The effect of instantiating the template complex for any type other than float, double or long double is unspecified. Why would the standard authors explicitly add this restriction? This makes it unspecified, for example, what happens if you make complex<int> or a complex<MyCustomFixedPointType> and seems like an artificial restriction. Is there a reason for this limitation? Is there a workaround if you want to instantiate complex with your own custom type? I'm primarily asking this question because of this earlier question, in which the OP was confused as to why abs was giving bizarre outputs for complex<int>. That said, this still doesn't quite make sense given that we also might want to make complex numbers out of fixed-points types, higher-precision real numbers, etc. Thanks!

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• BigInteger.ToString() returns more than 50 decimal digits.

  - by brickner

  I'm using .NET 4 System.Numerics.BigInteger Structure and I'm getting results different from the documentation. In the documentation of BigInteger.ToString() Method It says: The ToString() method supports 50 decimal digits of precision. That is, if the BigInteger value has more than 50 digits, only the 50 most significant digits are preserved in the output string; all other digits are replaced with zeros. I have some code that takes a 60 decimal digits BigInteger and converts it to a string. The 60 significant decimal digits string didn't lose any significant digits: const string vString = "123456789012345678901234567890123456789012345678901234567890"; Assert.AreEqual(60, vString.Length); BigInteger v = BigInteger.Parse(vString); Assert.AreEqual(60, v.ToString().Length); Assert.AreEqual('9', v.ToString()[58]); Assert.AreEqual('1', v.ToString()[0]); Assert.AreEqual(vString, v.ToString()); All the asserts pass. What exactly does the quoted part of the documentation mean?

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• How to split movie and play parts to look as a whole?

  - by luksow

  I'm writing software which is demonstraiting video on demand service. One of the feature is something similiar to IIS Smooth Streaming - I want to adjust quality to the bandwith of the client. My idea is, to split single movie into many, let's say - 2 seconds parts, in different qualities and then send it to the client and play them. The point is that for example first part can be in very high quality, and second in really poor (if the bandwith seems to be poor). The question is - do you know any software that allows me to cut movies precisly? For example ffmpeg splits movies in a way that join is visible and really annoying (seconds are the measure of precision). I use qt + phonon as a player if it matters. Or maybe you know any better way to provide such feature, without splitting movie into parts?

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• F# powerpack and distribution

  - by rwallace

  I need arbitrary precision rational numbers, which I'm given to understand are available in the F# powerpack. My question is about the mechanics of distribution; my program needs to be able to compile and run both on Windows/.Net and Linux/Mono at least, since I have potential users on both platforms. As I understand it, the best procedure is: Download the powerpack .zip, not the installer. Copy the DLL into my program directory. Copy the accompanying license file into my program directory, to make sure everything is above board. Declare references and go ahead and use the functions I need. Ship the above files along with my source and binary, and since the DLL uses byte code, it will work fine on any platform. Is this the correct procedure? Am I missing anything?

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• Mean of Sampleset and powered Sampleset

  - by Milla Well

  I am working on an ICA implementation wich is based on the assumption, that all source signals are independent. So I checked on the basic concepts of Dependence vs. Correlation and tried to show this example on sample data from numpy import * from numpy.random import * k = 1000 s = 10000 mn = 0 mnPow = 0 for i in arange(1,k): a = randn(s) a = a-mean(a) mn = mn + mean(a) mnPow = mnPow + mean(a**3) print "Mean X: ", mn/k print "Mean X^3: ", mnPow/k But I couldn't produce the last step of this example E(X^3) = 0: >> Mean X: -1.11174580826e-18 >> Mean X^3: -0.00125229267144 First value I would consider to be zero, but second value is too large, isn't it? Since I subtract the mean of a, I expected the mean of a^3 to be zero as well. Does the problem lie in the random number generator, the precision of the numerical values in my misunderstanding of the concepts of mean and expected value?

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• Kernel module for /proc

  - by sb2367

  How to write a kernel module that creates a directory in /proc named mymod and a file in it name is mymodfile. This file should accept a number ranged from 1 to 3 when written into it and return the following messages when read based on the number already written into it: • 1: Current system time (in microseconds precision) • 2: System uptime • 3: Number of processes currently in the system “The Output” root@Paradise# echo 1 > /proc/mymod/mymodfile root@Paradise# cat /proc/mymod/mymodfile 08:30:24 342us root@Paradise# echo 2 > /proc/mymod/mymodfile root@Paradise# cat /proc/mymod/mymodfile up 1 day, 8 min root@Paradise# echo 3 > /proc/mymod/mymodfile root@Paradise# cat /proc/mymod/mymodfile process count: 48 please give me some hint how to write a kernel modules and how to compile and install it .

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• Division inaccurate in Javascript?

  - by Nate

  If I perform the following operation in Javascript: 0.06120*400 The result is 24.48. However, if I do this: 24.48/400 The result is: 0.061200000000000004 JSFiddle: http://jsfiddle.net/zcDH7/ So it appears that Javascript rounds things differently when doing division and multiplication? Using my calculator, the operation 24.48/400 results in the correct answer of 0.0612. How should I deal with Javascript's inaccurate division? I can't simply round the number off, because I will be dealing with numbers of varying precision. Thanks for your advice.

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• Why is this postgresql query so slow?

  - by user315975

  I'm no database expert, but I have enough knowledge to get myself into trouble, as is the case here. This query SELECT DISTINCT p.* FROM points p, areas a, contacts c WHERE ( p.latitude > 43.6511659465 AND p.latitude < 43.6711659465 AND p.longitude > -79.4677941889 AND p.longitude < -79.4477941889) AND p.resource_type = 'Contact' AND c.user_id = 6 is extremely slow. The points table has fewer than 2000 records, but it takes about 8 seconds to execute. There are indexes on the latitude and longitude columns. Removing the clause concering the resource_type and user_id make no difference. The latitude and longitude fields are both formatted as number(15,10) -- I need the precision for some calculations. There are many, many other queries in this project where points are compared, but no execution time problems. What's going on?

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• how to tesselate bezier triangles?

  - by Cheery

  My concern are quadratic bezier triangles which I'm trying to tesselate for rendering them. I've managed to implement this by subdividing the triangle recursively like described in a wikipedia page. Though I'd like to get more precision to subdivision. The problem is that I'll either get too few subdivisions or too many because the amount of surfaces doubles on every iteration of that algorithm. In particular I would need an adaptive tesselation algorithm that allows me to define the amount of segments at the edges. I'm not sure whether I can get that though so I'd also like to hear about uniform tesselation techniques. Hardest trouble I have trouble with calculating normals for a point in bezier surface, which I'm not sure whether I need, but been trying to solve out.

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• How to very efficiently assign lat/long to city boundary described by shape ?

  - by watcherFR

  I have a huge shapefile of 36.000 non-overlapping polygones (city boundaries). I want to easily determine the polygone into which a given lat/long falls. What would the best way given that it must be extremely computationaly efficient ? I was thinking of creating a lookup table (tilex,tiley,polygone_id) where tilex and tiley are tile identifiers at zoom levels 21 or 22. Yes, the lack of precision of using tile numbers and a planar projection is acceptable in my application. I would rather not use postgres's GIS extension and am fine with a program that will run for 2 days to generate all the INSERT statements.

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• Convert long number as string in the serialization

  - by Bruno

  I have a custom made class that use a long as ID. However, when I call my action using ajax, my ID is truncated and it loses the last 2 numbers because javascript loses precision when dealing with large numbers. My solution would be to give a string to my javascript, but the ID have to stay as a long on the server side. Is there a way to serialize the property as a string? I'm looking for some kind of attribute. Controller public class CustomersController : ApiController { public IEnumerable<CustomerEntity> Get() { yield return new CustomerEntity() { ID = 1306270928525862486, Name = "Test" }; } } Model public class CustomerEntity { public long ID { get; set; } public string Name { get; set; } } JSON Result [{"Name":"Test","ID":1306270928525862400}]

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• GSL interpolation error, values must be x values must be monotonically increasing

  - by pyCthon

  Hi my problem is that my data set is monotonically increasing but towards the end the of the data it looks like it does below ,where some of the x[i-1] = x[i] as shown below. This causes an error to be raised in GSL because it thinks that the values are not monotonically increasing. Is there a solution, fix or work around for this problem? the values are already double precision ,this particular data set starts at 9.86553e-06 and ends at .999999 would the only solution be to offset every value in a for loop? 0.999981 0.999981 0.999981 0.999982 0.999982 0.999983 0.999983 0.999983 0.999984 0.999984 0.999985 0.999985 0.999985

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