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  • What is the Fastest Way to Check for a Keyword in a List of Keywords in Delphi?

    - by lkessler
    I have a small list of keywords. What I'd really like to do is akin to: case MyKeyword of 'CHIL': (code for CHIL); 'HUSB': (code for HUSB); 'WIFE': (code for WIFE); 'SEX': (code for SEX); else (code for everything else); end; Unfortunately the CASE statement can't be used like that for strings. I could use the straight IF THEN ELSE IF construct, e.g.: if MyKeyword = 'CHIL' then (code for CHIL) else if MyKeyword = 'HUSB' then (code for HUSB) else if MyKeyword = 'WIFE' then (code for WIFE) else if MyKeyword = 'SEX' then (code for SEX) else (code for everything else); but I've heard this is relatively inefficient. What I had been doing instead is: P := pos(' ' + MyKeyword + ' ', ' CHIL HUSB WIFE SEX '); case P of 1: (code for CHIL); 6: (code for HUSB); 11: (code for WIFE); 17: (code for SEX); else (code for everything else); end; This, of course is not the best programming style, but it works fine for me and up to now didn't make a difference. So what is the best way to rewrite this in Delphi so that it is both simple, understandable but also fast? (For reference, I am using Delphi 2009 with Unicode strings.) Followup: Toby recommended I simply use the If Then Else construct. Looking back at my examples that used a CASE statement, I can see how that is a viable answer. Unfortunately, my inclusion of the CASE inadvertently hid my real question. I actually don't care which keyword it is. That is just a bonus if the particular method can identify it like the POS method can. What I need is to know whether or not the keyword is in the set of keywords. So really I want to know if there is anything better than: if pos(' ' + MyKeyword + ' ', ' CHIL HUSB WIFE SEX ') > 0 then The If Then Else equivalent does not seem better in this case being: if (MyKeyword = 'CHIL') or (MyKeyword = 'HUSB') or (MyKeyword = 'WIFE') or (MyKeyword = 'SEX') then In Barry's comment to Kornel's question, he mentions the TDictionary Generic. I've not yet picked up on the new Generic collections and it looks like I should delve into them. My question here would be whether they are built for efficiency and how would using TDictionary compare in looks and in speed to the above two lines? In later profiling, I have found that the concatenation of strings as in: (' ' + MyKeyword + ' ') is VERY expensive time-wise and should be avoided whenever possible. Almost any other solution is better than doing this.

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  • Fastest way to put contents of Set<String> to a single String with words separated by a whitespace?

    - by Lars Andren
    I have a few Set<String>s and want to transform each of these into a single String where each element of the original Set is separated by a whitespace " ". A naive first approach is doing it like this Set<String> set_1; Set<String> set_2; StringBuilder builder = new StringBuilder(); for (String str : set_1) { builder.append(str).append(" "); } this.string_1 = builder.toString(); builder = new StringBuilder(); for (String str : set_2) { builder.append(str).append(" "); } this.string_2 = builder.toString(); Can anyone think of a faster, prettier or more efficient way to do this?

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  • Fastest way to modify a decimal-keyed table in MySQL?

    - by javanix
    I am dealing with a MySQL table here that is keyed in a somewhat unfortunate way. Instead of using an auto increment table as a key, it uses a column of decimals to preserve order (presumably so its not too difficult to insert new rows while preserving a primary key and order). Before I go through and redo this table to something more sane, I need to figure out how to rekey it without breaking everything. What I would like to do is something that takes a list of doubles (the current keys) and outputs a list of integers (which can be cast down to doubles for rekeying). For example, input {1.00, 2.00, 2.50, 2.60, 3.00} would give output {1, 2, 3, 4, 5). Since this is a database, I also need to be able to update the rows nicely: UPDATE table SET `key`='3.00' WHERE `key`='2.50'; Can anyone think of a speedy algorithm to do this? My current thought is to read all of the doubles into a vector, take the size of the vector, and output a new vector with values from 1 => doubleVector.size. This seems pretty slow, since you wouldn't want to read every value into the vector if, for instance, only the last n/100 elements needed to be modified. I think there is probably something I can do in place, since only values after the first non-integer double need to be modified, but I can't for the life of me figure anything out that would let me update in place as well. For instance, setting 2.60 to 3.00 the first time you see 2.50 in the original key list would result in an error, since the key value 3.00 is already used for the table.

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  • Fastest way to convert a list of doubles to a unique list of integers?

    - by javanix
    I am dealing with a MySQL table here that is keyed in a somewhat unfortunate way. Instead of using an auto increment table as a key, it uses a column of decimals to preserve order (presumably so its not too difficult to insert new rows while preserving a primary key and order). Before I go through and redo this table to something more sane, I need to figure out how to rekey it without breaking everything. What I would like to do is something that takes a list of doubles (the current keys) and outputs a list of integers (which can be cast down to doubles for rekeying). For example, input {1.00, 2.00, 2.50, 2.60, 3.00} would give output {1, 2, 3, 4, 5). Since this is a database, I also need to be able to update the rows nicely: UPDATE table SET `key`='3.00' WHERE `key`='2.50'; Can anyone think of a speedy algorithm to do this? My current thought is to read all of the doubles into a vector, take the size of the vector, and output a new vector with values from 1 => doubleVector.size. This seems pretty slow, since you wouldn't want to read every value into the vector if, for instance, only the last n/100 elements needed to be modified. I think there is probably something I can do in place, since only values after the first non-integer double need to be modified, but I can't for the life of me figure anything out that would let me update in place as well. For instance, setting 2.60 to 3.00 the first time you see 2.50 in the original key list would result in an error, since the key value 3.00 is already used for the table.

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  • Fastest way to represent a collection of bits in PHP?

    - by Piskvor
    What is a good way to represent a collection of bits? I have a set of various on/off toggles (thousands of them) and need to store and retrieve their state. The naïve implementation would be an array of booleans, but I'm wondering if there's a better way (better in terms of access speed and/or memory requirements). I've found this BitArray implementation, but it's limited to 32 bits, which is not enough for this case.

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  • Fastest way to zero out a 2d array in C?

    - by Eddy
    I want to repeatedly zero a large 2d array in C. This is what I do at the moment: for(j = 0; j < n; j++) { for(i = 0; i < n; i++) { array[i][j] = 0; } } I've tried using memset: memset(array, 0, sizeof(array)) But this only works for 1D arrays. When I printf the contents of the 2D array, the first row is zeroes, but then I got a load of random large numbers and it crashes.

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  • What is the fastest way to Initialize a multi-dimensional array to non-default values in .NET?

    - by AMissico
    How do I initialize a multi-dimensional array of a primitive type as fast as possible? I am stuck with using multi-dimensional arrays. My problem is performance. The following routine initializes a 100x100 array in approx. 500 ticks. Removing the int.MaxValue initialization results in approx. 180 ticks just for the looping. Approximately 100 ticks to create the array without looping and without initializing to int.MaxValue. Routines similiar to this are called a few hundred-thousand to several million times during a "run". The array size will not change during a run and arrays are created one-at-a-time, used, then discarded, and a new array created. A "run" which may last from one minute (using 10x10 arrays) to forty-five minutes (100x100). The application creates arrays of int, bool, and struct. There can be multiple "runs" executing at same time, but are not because performance degrades terribly. I am using 100x100 as a base-line. I am open to suggestions on how to optimize this non-default initialization of an array. One idea I had is to use a smaller primitive type when available. For instance, using byte instead of int, saves 100 ticks. I would be happy with this, but I am hoping that I don't have to change the primitive data type. public int[,] CreateArray(Size size) { int[,] array = new int[size.Width, size.Height]; for (int x = 0; x < size.Width; x++) { for (int y = 0; y < size.Height; y++) { array[x, y] = int.MaxValue; } } return array; } Down to 450 ticks with the following: public int[,] CreateArray1(Size size) { int iX = size.Width; int iY = size.Height; int[,] array = new int[iX, iY]; for (int x = 0; x < iX; x++) { for (int y = 0; y < iY; y++) { array[x, y] = int.MaxValue; } } return array; } Down to approximately 165 ticks after a one-time initialization of 2800 ticks. (See my answer below.) If I can get stackalloc to work with multi-dimensional arrays, I should be able to get the same performance without having to intialize the private static array. private static bool _arrayInitialized5; private static int[,] _array5; public static int[,] CreateArray5(Size size) { if (!_arrayInitialized5) { int iX = size.Width; int iY = size.Height; _array5 = new int[iX, iY]; for (int x = 0; x < iX; x++) { for (int y = 0; y < iY; y++) { _array5[x, y] = int.MaxValue; } } _arrayInitialized5 = true; } return (int[,])_array5.Clone(); } Down to approximately 165 ticks without using the "clone technique" above. (See my answer below.) I am sure I can get the ticks lower, if I can just figure out the return of CreateArray9. public unsafe static int[,] CreateArray8(Size size) { int iX = size.Width; int iY = size.Height; int[,] array = new int[iX, iY]; fixed (int* pfixed = array) { int count = array.Length; for (int* p = pfixed; count-- > 0; p++) *p = int.MaxValue; } return array; }

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  • What is the fastest way to display an image in QT on X11 without OpenGL?

    - by msh
    I need to display a raw image in a QT widget. I'm running X11 on a framebuffer, so OpenGL is not available. Both the image and the framebuffer are in the same format - RGB565, but I can change it to any other format if needed. I don't need blending or scaling. I just need to display pixels as is. I'm using QPainter::drawImage, but it converts QImage to QPixmap and this conversion seems to be very slow. Also it is backed by Xrender and I think there is unnecessary overhead required to support blending in Xrender which I don't really need Is there any better way? If it is not available in QT, I can use Xlib or any other library or protocol. I can modify the driver, X server or anything else.

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  • Copying 6000 tables and data from sqlserver to oracle ==> fastest method?

    - by nazer555
    i need to copy the tables and data (about 5 yrs data, 6200 tables) stored in sqlserver, i am using datastage and odbc connection to connect and datstage automatically creates the table with data, but its taking 2-3 hours per table as tables are very large(0.5 gig, 300+columns and about 400k rows). How can i achieve this the fastes as at this rate i am able to only copy 5 tables per day but within 30 days i need move over these 6000 tables.

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  • What is the fastest way to do division in C for 8bit MCUs?

    - by Jordan S
    I am working on the firmware for a device that uses an 8bit mcu (8051 architecture). I am using SDCC (Small Device C Compiler). I have a function that I use to set the speed of a stepper motor that my circuit is driving. The speed is set by loading a desired value into the reload register for a timer. I have a variable, MotorSpeed that is in the range of 0 to 1200 which represents pulses per second to the motor. My function to convert MotorSpeed to the correct 16bit reload value is shown below. I know that float point operations are pretty slow and I am wondering if there is a faster way of doing this... void SetSpeed() { float t = MotorSpeed; unsigned int j = 0; t = 1/t ; t = t / 0.000001; j = MaxInt - t; TMR3RL = j; // Set reload register for desired freq return; }

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  • Which has been the most reliable, fastest Windows C++ profiler that you have used?

    - by carleeto
    I need to profile a real time C++ app on Windows. Most of the available profilers are either terribly expensive, total overkill, or both. I don't need any .NET stuff. Since it is a real time app, I need the profiler to be as fast as possible. It would be excellent if it integrated in some way with Visual Studio 2005/2008, but that's not necessary. If this description reminds you of a profiler that you have used, I would really like to know about it. I am hoping to draw from people's use of C++ profilers on Windows to pinpoint one that will do the job. Thanks.

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  • What is the fastest way for reading huge files in Delphi?

    - by dummzeuch
    My program needs to read chunks from a huge binary file with random access. I have got a list of offsets and lengths which may have several thousand entries. The user selects an entry and the program seeks to the offset and reads length bytes. The program internally uses a TMemoryStream to store and process the chunks read from the file. Reading the data is done via a TFileStream like this: FileStream.Position := Offset; MemoryStream.CopyFrom(FileStream, Size); This works fine but unfortunately it becomes increasingly slower as the files get larger. The file size starts at a few megabytes but frequently reaches several tens of gigabytes. The chunks read are around 100 kbytes in size. The file's content is only read by my program. It is the only program accessing the file at the time. Also the files are stored locally so this is not a network issue. I am using Delphi 2007 on a Windows XP box. What can I do to speed up this file access?

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  • SharePoint WSS 3.0 - Fastest approach to build data-bound forms?

    - by Rusty Scupper
    Pardon the vague question, but I've just inherited a project to build a couple dozen forms pulling data from a SQL 2005 database. The forms are mostly standard database lookups with just a couple updates so the data layer is very simple -- I'm the DBA -- but we just recently started using SharePoint WSS 3.0 for a departmental web site and I would prefer to integrate these forms into WSS rather than build a separate standalone ASP.NET app. I'm hoping there is some RAD framework out there that integrates with WSS for data bound forms. I've been searching online, but haven't found anything very promising and the data viewer web part in SharePoint Designer looks complicated to integrate with an external SQL database. TIA, Rusty

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  • What's the fastest way to strip and replace a document of high unicode characters using Python?

    - by Rhubarb
    I am looking to replace from a large document all high unicode characters, such as accented Es, left and right quotes, etc., with "normal" counterparts in the low range, such as a regular 'E', and straight quotes. I need to perform this on a very large document rather often. I see an example of this in what I think might be perl here: http://www.designmeme.com/mtplugins/lowdown.txt Is there a fast way of doing this in Python without using s.replace(...).replace(...).replace(...)...? I've tried this on just a few characters to replace and the document stripping became really slow.

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  • What's the fastest way to scrape a lot of pages in php?

    - by Yegor
    I have a data aggregator that relies on scraping several sites, and indexing their information in a way that is searchable to the user. I need to be able to scrape a vast number of pages, daily, and I have ran into problems using simple curl requests, that are fairly slow when executed in rapid sequence for a long time (the scraper runs 24/7 basically). Running a multi curl request in a simple while loop is fairly slow. I speeded it up by doing individual curl requests in a background process, which works faster, but sooner or later the slower requests start piling up, which ends up crashing the server. Are there more efficient ways of scraping data? perhaps command line curl?

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  • What is the fastest way to find duplicates in multiple BIG txt files?

    - by user2950750
    I am really in deep water here and I need a lifeline. I have 10 txt files. Each file has up to 100.000.000 lines of data. Each line is simply a number representing something else. Numbers go up to 9 digits. I need to (somehow) scan these 10 files and find the numbers that appear in all 10 files. And here comes the tricky part. I have to do it in less than 2 seconds. I am not a developer, so I need an explanation for dummies. I have done enough research to learn that hash tables and map reduce might be something that I can make use of. But can it really be used to make it this fast, or do I need more advanced solutions? I have also been thinking about cutting up the files into smaller files. To that 1 file with 100.000.000 lines is transformed into 100 files with 1.000.000 lines. But I do not know what is best: 10 files with 100 million lines or 1000 files with 1 million lines? When I try to open the 100 million line file, it takes forever. So I think, maybe, it is just too big to be used. But I don't know if you can write code that will scan it without opening. Speed is the most important factor in this, and I need to know if it can be done as fast as I need it, or if I have to store my data in another way, for example, in a database like mysql or something. Thank you in advance to anybody that can give some good feedback.

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  • What's the fastest way to approximate the period of data using Octave?

    - by John
    I have a set of data that is periodic (but not sinusoidal). I have a set of time values in one vector and a set of amplitudes in a second vector. I'd like to quickly approximate the period of the function. Any suggestions? Specifically, here's my current code. I'd like to approximate the period of the vector x(:,2) against the vector t. Ultimately, I'd like to do this for lots of initial conditions and calculate the period of each and plot the result. function xdot = f (x,t) xdot(1) =x(2); xdot(2) =-sin(x(1)); endfunction x0=[1;1.75]; #eventually, I'd like to try lots of values for x0(2) t = linspace (0, 50, 200); x = lsode ("f", x0, t) plot(x(:,1),x(:,2)); Thank you! John

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  • Fastest way of creating XML from parent-child table in c#?

    - by rudnev
    Assume we have some DataTable or IEnumerable with ChildID, ParentID and Title. We need to serialize it to XML like <Entity title=""> <Entity title=""></Entity> <Entity title=""></Entity> </Entity> As i found out, standard DataTable.GetXML() returns something different. I thought about initializing class tree like Entity e = new Entity(ID, Title, ParentEntityID) and then serializing it. Table is about 3000 elems. Is there faster way?

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  • What is the fastest way to filter a list of strings when making an Intellisense/Autocomplete list?

    - by user559548
    Hello everyone, I'm writing an Intellisense/Autocomplete like the one you find in Visual Studio. It's all fine up until when the list contains probably 2000+ items. I'm using a simple LINQ statement for doing the filtering: var filterCollection = from s in listCollection where s.FilterValue.IndexOf(currentWord, StringComparison.OrdinalIgnoreCase) >= 0 orderby s.FilterValue select s; I then assign this collection to a WPF Listbox's ItemSource, and that's the end of it, works fine. Noting that, the Listbox is also virtualised as well, so there will only be at most 7-8 visual elements in memory and in the visual tree. However the caveat right now is that, when the user types extremely fast in the richtextbox, and on every key up I execute the filtering + binding, there's this semi-race condition, or out of sync filtering, like the first key stroke's filtering could still be doing it's filtering or binding work, while the fourth key stroke is also doing the same. I know I could put in a delay before applying the filter, but I'm trying to achieve a seamless filtering much like the one in Visual Studio. I'm not sure where my problem exactly lies, so I'm also attributing it to IndexOf's string operation, or perhaps my list of string's could be optimised in some kind of index, that could speed up searching. Any suggestions of code samples are much welcomed. Thanks.

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