Search Results

Search found 15637 results on 626 pages for 'memory efficient'.

Page 301/626 | < Previous Page | 297 298 299 300 301 302 303 304 305 306 307 308  | Next Page >

• What's the standard algorithm for syncing two lists of objects?

  - by Oliver Giesen

  I'm pretty sure this must be in some kind of text book (or more likely in all of them) but I seem to be using the wrong keywords to search for it... :( A common task I'm facing while programming is that I am dealing with lists of objects from different sources which I need to keep in sync somehow. Typically there's some sort of "master list" e.g. returned by some external API and then a list of objects I create myself each of which corresponds to an object in the master list. Sometimes the nature of the external API will not allow me to do a live sync: For instance the external list might not implement notifications about items being added or removed or it might notify me but not give me a reference to the actual item that was added or removed. Furthermore, refreshing the external list might return a completely new set of instances even though they still represent the same information so simply storing references to the external objects might also not always be feasible. Another characteristic of the problem is that both lists cannot be sorted in any meaningful way. You should also assume that initializing new objects in the "slave list" is expensive, i.e. simply clearing and rebuilding it from scratch is not an option. So how would I typically tackle this? What's the name of the algorithm I should google for? In the past I have implemented this in various ways (see below for an example) but it always felt like there should be a cleaner and more efficient way. Here's an example approach: Iterate over the master list Look up each item in the "slave list" Add items that do not yet exist Somehow keep track of items that already exist in both lists (e.g. by tagging them or keeping yet another list) When done iterate once more over the slave list Remove all objects that have not been tagged (see 4.) Update Thanks for all your responses so far! I will need some time to look at the links. Maybe one more thing worthy of note: In many of the situations where I needed this the implementation of the "master list" is completely hidden from me. In the most extreme cases the only access I might have to the master list might be a COM-interface that exposes nothing but GetFirst-, GetNext-style methods. I'm mentioning this because of the suggestions to either sort the list or to subclass it both of which is unfortunately not practical in these cases unless I copy the elements into a list of my own and I don't think that would be very efficient. I also might not have made it clear enough that the elements in the two lists are of different types, i.e. not assignment-compatible: Especially, the elements in the master list might be available as interface references only.

  Read the article

• SQL query that returns columns form table A plus a bit column that specifies with the PK of table A

  - by dannie.f

  How can I write an efficient SQL query that returns columns form table A plus a bit column that specifies whether the PK of table A exists in table B? I am using MS SQLServer 2005. Thanks.

  Read the article

• Why use Java's AsynchronousFileChannel?

  - by Joey Bell

  I can understand why network apps would use multiplexing (to not create too many threads), and why programs would use async calls for pipelining (more efficient). But I don't understand the purpose of AsynchronousFileChannel. Any ideas?

  Read the article

• whats wrong in this LINQ synatx?

  - by Saurabh Kumar

  Hi, I am trying to convert a SQL query to LINQ. Somehow my count(distinct(x)) logic does not seem to be working correctly. The original SQL is quite efficient(or so i think), but the generated SQL is not even returning the correct result. I am trying to fix this LINQ to do what the original SQL is doing, AND in an efficient way as the original query is doing. Help here would be really apreciated as I am stuck here :( SQL which is working and I need to make a comparable LINQ of: SELECT [t1].[PersonID] AS [personid] FROM [dbo].[Code] AS [t0] INNER JOIN [dbo].[phonenumbers] AS [t1] ON [t1].[PhoneCode] = [t0].[Code] INNER JOIN [dbo].[person] ON [t1].[PersonID]= [dbo].[Person].PersonID WHERE ([t0].[codetype] = 'phone') AND ( ([t0].[CodeDescription] = 'Home') AND ([t1].[PhoneNum] = '111') OR ([t0].[CodeDescription] = 'Work') AND ([t1].[PhoneNum] = '222') ) GROUP BY [t1].[PersonID] HAVING COUNT(DISTINCT([t1].[PhoneNum]))=2 The LINQ which I made is approximately as below: var ids = context.Code.Where(predicate); var rs = from r in ids group r by new { r.phonenumbers.person.PersonID} into g let matchcount=g.Select(p => p.phonenumbers.PhoneNum).Distinct().Count() where matchcount ==2 select new { personid = g.Key }; Unfortunately, the above LINQ is NOT generating the correct result, and is actually internally getting generated to the SQL shown below. By the way, this generated query is also reading ALL the rows(about 19592040) around 2 times due to the COUNTS :( Wich is a big performance issue too. Please help/point me to the right direction. Declare @p0 VarChar(10)='phone' Declare @p1 VarChar(10)='Home' Declare @p2 VarChar(10)='111' Declare @p3 VarChar(10)='Work' Declare @p4 VarChar(10)='222' Declare @p5 VarChar(10)='2' SELECT [t9].[PersonID], ( SELECT COUNT(*) FROM ( SELECT DISTINCT [t13].[PhoneNum] FROM [dbo].[Code] AS [t10] INNER JOIN [dbo].[phonenumbers] AS [t11] ON [t11].[PhoneType] = [t10].[Code] INNER JOIN [dbo].[Person] AS [t12] ON [t12].[PersonID] = [t11].[PersonID] INNER JOIN [dbo].[phonenumbers] AS [t13] ON [t13].[PhoneType] = [t10].[Code] WHERE ([t9].[PersonID] = [t12].[PersonID]) AND ([t10].[codetype] = @p0) AND ((([t10].[codetype] = @p1) AND ([t11].[PhoneNum] = @p2)) OR (([t10].[codetype] = @p3) AND ([t11].[PhoneNum] = @p4))) ) AS [t14] ) AS [cnt] FROM ( SELECT [t3].[PersonID], ( SELECT COUNT(*) FROM ( SELECT DISTINCT [t7].[PhoneNum] FROM [dbo].[Code] AS [t4] INNER JOIN [dbo].[phonenumbers] AS [t5] ON [t5].[PhoneType] = [t4].[Code] INNER JOIN [dbo].[Person] AS [t6] ON [t6].[PersonID] = [t5].[PersonID] INNER JOIN [dbo].[phonenumbers] AS [t7] ON [t7].[PhoneType] = [t4].[Code] WHERE ([t3].[PersonID] = [t6].[PersonID]) AND ([t4].[codetype] = @p0) AND ((([t4].[codetype] = @p1) AND ([t5].[PhoneNum] = @p2)) OR (([t4].[codetype] = @p3) AND ([t5].[PhoneNum] = @p4))) ) AS [t8] ) AS [value] FROM ( SELECT [t2].[PersonID] FROM [dbo].[Code] AS [t0] INNER JOIN [dbo].[phonenumbers] AS [t1] ON [t1].[PhoneType] = [t0].[Code] INNER JOIN [dbo].[Person] AS [t2] ON [t2].[PersonID] = [t1].[PersonID] WHERE ([t0].[codetype] = @p0) AND ((([t0].[codetype] = @p1) AND ([t1].[PhoneNum] = @p2)) OR (([t0].[codetype] = @p3) AND ([t1].[PhoneNum] = @p4))) GROUP BY [t2].[PersonID] ) AS [t3] ) AS [t9] WHERE [t9].[value] = @p5 Thanks!

  Read the article

• Is frozenset adequate for caching of symmetric input data in a python dict?

  - by Debilski

  The title more or less says it all: I have a function which takes symmetric input in two arguments, e.g. something like def f(a1, a2): return heavy_stuff(abs(a1 - a2)) Now, I want to introduce some caching method. Would it be correct / pythonic / reasonably efficient to do something like this: cache = {} def g(a1, a2): return cache.setdefault(frozenset((tuple(a1), tuple(a2))), f(a1, a2)) Or would there be some better way?

  Read the article

• vba: read only first 1000 characters of file into string

  - by every_answer_gets_a_point

  i need to open a txt file and read it into a string in VBA, but i would like to only get the first 1000 characters. the file itself is 20mb and i only need the first 1000 characters. is there a way to make this efficient?

  Read the article

• Determine Whether Two Date Ranges Overlap

  - by Ian Nelson

  Given two date ranges, what is the simplest or most efficient way to determine whether the two date ranges overlap? As an example, suppose we have ranges denoted by DateTime variables StartDate1 to EndDate1 and StartDate2 to EndDate2.

  Read the article

• Options for Cocoa-based text editor

  - by user308444

  Hello. I am working on a cocoa-based text editor. Should I base it on NSTextView or is there a more efficient option? Keep in mind that I plan to support tabs so there can be many editors open at the same time.

  Read the article

• Fast double -> short conversion with clamping using SSE?

  - by gct

  Is there a fast way to cast double values to shorts (16 bits signed), currently I'm doing something like this: double dval = <sum junk> int16_t sval; if (val > int16_max) { sval = int16_max; } else if (val < int16_min) { sval = int16_min; } else sval = (int16_t)val; I suspect there's a fast way to do this using SSE that will be significantly more efficient.

  Read the article

• PHP: Convert shorthand Hex Colors to Regular

  - by Chad Whitaker

  I'm trying to make a function that will take short hand hex color to the long hex color. For example if someone submits "f60" it will convert to "ff6600". I understand I need to repeat each number as itself, but what is the most efficient way to do this? Thank you.

  Read the article

• Help with regex - extracting text.

  - by Yeti

  I have 3 separate strings: $d = 'Created on November 25, 2009'; $v = 'Viewed 17,603 times'; $h = '389 hits'; Which needs to be converted to: $d1 = {unix timestamp of November 25, 2009}; $v1 = "17603"; (commas stripped if it exists) $h1 = "389"; What is the most efficient way to do this (possibly with regex)? Any code snippet would be great.

  Read the article

• Insert statement with where clause.

  - by debraj

  I had a table with unique Date_t1 date type field, but in Table description field is not mentioned as unique, now while inserting new row i need to validate if date exist or not, If already exist i should not allow to make changes on that row, neither a new row needs to be created, Any idea how to resolve this problem in efficient way,

  Read the article

• Mesh simplification

  - by Amrita

  I wish to develop a softare for 3D object compression (by polygon reduction) in flex using papervision 3D. Could you please suggest me an efficient algorithm for the same?

  Read the article

• Java - Collections.sort() performance

  - by msr

  Hello, Im using Collections.sort() to sort a LinkedList whose elements implements Comparable interface, so they are sorted in a natural order. In the javadoc documentation its said this method uses mergesort algorithm wich has n*log(n) performance. My question is if there is a more efficient algorithm to sort my LinkedList? The size of that list could be very high and sort will be also very frequent. Thanks!

  Read the article

• What is mangling tinyurls?

  - by djn

  Hello all. I've noticed that some form processors make a mess out of posted TinyURLs (converting the thing to a broken 'tinyurl": "http:\/?\/?tinyurl.com\/?whatever", "ok": tr') while leaving alone other plain URLs. I've seen it happen in WordPress, and I've seen it here on SO (eg.: http://stackoverflow.com/questions/2508690/whats-the-most-efficient-way-to-setup-a-multi-lingual-website - second comment to first answer). Has anybody looked into what component or function is doing this? Is there a way to prevent it?

  Read the article

• mean and variance of image in single pass

  - by ajith

  hi everyone,am trying to calculate mean and variance using 3X3 window over image(hXw) in opencv...here is my code...is there any accuracy issues with this??or is there any other efficient method to do it in one pass.? int pi,a,b; for(i=1;i

  Read the article

• What's the best way to sort results of a given query by fixed column values ?

  - by eugene y

  Example: SELECT id, name FROM user WHERE id IN (1,2,3,4,5) ORDER BY FIELD(id, 2, 3, 4, 1, 5) I've seen some examples using FIND_IN_SET() or FIELD() functions. Which one is better? Are there any more efficient approaches? Order is supposed to change rarely.

  Read the article

• How to remove duplicates from a StringCollection in c#?

  - by Taz

  How to remove duplicates from a StringCollection in c#? I was looking for a more efficient approach. StringCollection is returned from an API.

  Read the article

• Best way to code this, string to map conversion in Groovy

  - by Daxon

  I have a string like def data = "session=234567893egshdjchasd&userId=12345673456&timeOut=1800000" I want to convert it to a map ["session", 234567893egshdjchasd] ["userId", 12345673456] ["timeout", 1800000] This is the current way I am doing it, def map = [:] data.splitEachLine("&"){ it.each{ x -> def object = x.split("=") map.put(object[0], object[1]) } } It works, but is there a more efficient way?

  Read the article

• Scale a .jpg file in WPF

  - by James Cadd

  I'd like to open a .jpg file in WPF, scale it down to around 50%, then save it back to the file system. What's a good/efficient way to go about doing that?

  Read the article

• Java efficent strategy to access a DB

  - by user279481

  A simple question: what is the more efficient way to access a db in Java/JDBC? I'm a web developper and I'd like to write some reusable and scalable code. What can you suggest?

  Read the article

• ESS workflow for R project/package development

  - by ahala

  Can anyone share his experience on workflow for R peject development under ESS? I tried several times to learn emacs but I have not get it yet. I can understand ESS as an editor, but is there a project view in ESS? what's the efficient ways to set up/view R project directory, coding, and testing? Thanks for any advices.

  Read the article

• Duplicating an array of strings.

  - by Jon

  arr = ["red","green","yellow"] arr2 = arr.clone arr2[0].replace("blue") puts arr.inspect puts arr2.inspect produces: ["blue", "green", "yellow"] ["blue", "green", "yellow"] Is there anyway to do a deep copy of an array of strings, other than using Marshal as i understand that is a hack. I could do: arr2 = [] arr.each do |e| arr2 << e.clone end but it doesn't seem very elegant, or efficient. Thanks

  Read the article

• Fastest way to reverse an array?

  - by mystify

  I have an table view, and the data source returns elements in the wrong order. So I have to reverse the elements in that array which returns the data for each row. How would I do that the most efficient way?

  Read the article

• How to find attribute value

  - by Pramodh

  Hi, I need to find an inner text of an element inside an XmlDocument and return it's Xpath. for example, searching for "ThisText" inside : <xml> <xml2 val="ThisText"></xml2> </xml> should return the Xpath of xml2 what's the most efficient way of doing this in c#?

  Read the article

< Previous Page | 297 298 299 300 301 302 303 304 305 306 307 308  | Next Page >