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  • Optimizing WordWrap Algorithm

    - by Milo
    I have a word-wrap algorithm that basically generates lines of text that fit the width of the text. Unfortunately, it gets slow when I add too much text. I was wondering if I oversaw any major optimizations that could be made. Also, if anyone has a design that would still allow strings of lines or string pointers of lines that is better I'd be open to rewriting the algorithm. Thanks void AguiTextBox::makeLinesFromWordWrap() { textRows.clear(); textRows.push_back(""); std::string curStr; std::string curWord; int curWordWidth = 0; int curLetterWidth = 0; int curLineWidth = 0; bool isVscroll = isVScrollNeeded(); int voffset = 0; if(isVscroll) { voffset = pChildVScroll->getWidth(); } int AdjWidthMinusVoffset = getAdjustedWidth() - voffset; int len = getTextLength(); int bytesSkipped = 0; int letterLength = 0; size_t ind = 0; for(int i = 0; i < len; ++i) { //get the unicode character letterLength = _unicodeFunctions.bringToNextUnichar(ind,getText()); curStr = getText().substr(bytesSkipped,letterLength); bytesSkipped += letterLength; curLetterWidth = getFont().getTextWidth(curStr); //push a new line if(curStr[0] == '\n') { textRows.back() += curWord; curWord = ""; curLetterWidth = 0; curWordWidth = 0; curLineWidth = 0; textRows.push_back(""); continue; } //ensure word is not longer than the width if(curWordWidth + curLetterWidth >= AdjWidthMinusVoffset && curWord.length() >= 1) { textRows.back() += curWord; textRows.push_back(""); curWord = ""; curWordWidth = 0; curLineWidth = 0; } //add letter to word curWord += curStr; curWordWidth += curLetterWidth; //if we need a Vscroll bar start over if(!isVscroll && isVScrollNeeded()) { isVscroll = true; voffset = pChildVScroll->getWidth(); AdjWidthMinusVoffset = getAdjustedWidth() - voffset; i = -1; curWord = ""; curStr = ""; textRows.clear(); textRows.push_back(""); ind = 0; curWordWidth = 0; curLetterWidth = 0; curLineWidth = 0; bytesSkipped = 0; continue; } if(curLineWidth + curWordWidth >= AdjWidthMinusVoffset && textRows.back().length() >= 1) { textRows.push_back(""); curLineWidth = 0; } if(curStr[0] == ' ' || curStr[0] == '-') { textRows.back() += curWord; curLineWidth += curWordWidth; curWord = ""; curWordWidth = 0; } } if(curWord != "") { textRows.back() += curWord; } updateWidestLine(); }

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  • Optimizing spacing of mesh containing a given set of points

    - by Feynman
    I tried to summarize the this as best as possible in the title. I am writing an initial value problem solver in the most general way possible. I start with an arbitrary number of initial values at arbitrary locations (inside a boundary.) The first part of my program creates a mesh/grid (I am not sure which is the correct nuance), with N points total, that contains all the initial values. My goal is to optimize the mesh such that the spacing is as uniform as possible. My solver seems to work half decently (it needs some more obscure debugging that is not relevant here.) I am starting with one dimension. I intend to generalize the algorithm to an arbitrary number of dimensions once I get it working consistently. I am writing my code in fortran, but feel free to reply with pseudocode or the language of your choice. Allow me to elaborate with an example: Say I am working on a closed interval [1,10] xmin=1 xmax=10 Say I have 3 initial points: xmin, 5 and xmax num_ivc=3 known(num_ivc)=[xmin,5,xmax] //my arrays start at 1. Assume "known" starts sorted I store my mesh/grid points in an array called coord. Say I want 10 points total in my mesh/grid. N=10 coord(10) Remember, all this is arbitrary--except the variable names of course. The algorithm should set coord to {1,2,3,4,5,6,7,8,9,10} Now for a less trivial example: num_ivc=3 known(num_ivc)=[xmin,5.5,xmax or just num_ivc=1 known(num_ivc)=[5.5] Now, would you have 5 evenly spaced points on the interval [1, 5.5] and 5 evenly spaced points on the interval (5.5, 10]? But there is more space between 1 and 5.5 than between 5.5 and 10. So would you have 6 points on [1, 5.5] followed by 4 on (5.5 to 10]. The key is to minimize the difference in spacing. I have been working on this for 2 days straight and I can assure you it is a lot trickier than it sounds. I have written code that only works if N is large only works if N is small only works if it the known points are close together only works if it the known points are far apart only works if at least one of the known points is near a boundary only works if none of the known points are near a boundary So as you can see, I have coded the gamut of almost-solutions. I cannot figure out a way to get it to perform equally well in all possible scenarios (that is, create the optimum spacing.)

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  • Passing variables to functions

    - by Faken
    A quick question: When i pass a variable to a function, dose the program make a copy of that variable to use in the function? If it dose and I knew that the function would only read the variable and never write to it, is it possible to pass a variable to the function without creating a copy of that variable or should I just leave that up to the compiler optimizations to do that automatically for me?

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  • Position of least significant bit that is set

    - by peterchen
    I am looking for an efficient way to determine the position of the least significant bit that is set in an integer, e.g. for 0x0FF0 it would be 4. A trivial implementation is this: unsigned GetLowestBitPos(unsigned value) { assert(value != 0); // handled separately unsigned pos = 0; while (!(value & 1)) { value >>= 1; ++pos; } return pos; } Any ideas how to squeeze some cycles out of it? (Note: this question is for people that enjoy such things, not for people to tell me xyzoptimization is evil.) [edit] Thanks everyone for the ideas! I've learnt a few other things, too. Cool!

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  • Import Namespace System.Query

    - by GateKiller
    I am trying to load Linq on my .Net 3.5 enabled web server by adding the following to my .aspx page: <%@ Import Namespace="System.Query" %> However, this fails and tells me it cannot find the namespace. The type or namespace name 'Query' does not exist in the namespace 'System' I have also tried with no luck: System.Data.Linq System.Linq System.Xml.Linq I believe that .Net 3.5 is working because var hello = "Hello World" seems to work. Can anyone help please? Cheers, Stephen PS: I just want to clarify that I don't use Visual Studio, I simple have a Text Editor and write my code directly into .aspx files.

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  • Function-Local Static Const variable Initialization semantics.

    - by Hassan Syed
    The questions are in bold, for those that cannot be bothered reading a question in depth. This is a followup to this question. It is to do with the initialization semantics of static variables in functions. Static variables should be initialized once, and their internal state might be altered later - as I (currently) do in the linked question. However, the code in question does not require the feature to change the state of the variable later. Let me clarrify my position, since I don't require the string object's internal state to change. The code is for a trait class for meta programming, and as such would would benifit from a const char * const ptr -- thus Ideally a local cost static const variable is needed. My educated guess is that in this case the string in question will be optimally placed in memory by the link-loader, and that the code is more secure and maps to the intended semantics. This leads to the semantics of such a variable "The C++ Programming language Third Edition -- Stroustrup" does not have anything (that I could find) to say about this matter. All that is said is that the variable is initialized once when the flow of control of the thread first reaches the code. This leads me to ponder if the following code would be sensible, and if not what are the intended semantics ?. #include <iostream> const char * const GetString(const char * x_in) { static const char * const x = x_in; return x; } int main() { const char * const temp = GetString("yahoo"); std::cout << temp << std::endl; const char * const temp2 = GetString("yahoo2"); std::cout << temp2 << std::endl; } The following compiles on GCC and prints "yahoo" twice. Which is what I want -- However it might not be standards compliant (which is why I post this question). It might be more elegant to have two functions, "SetString" and "String" where the latter forwards to the first. If it is standards compliant does someone know of a templates implementation in boost (or elsewhere) ?

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  • HSQLDB Constraint Violation & SQL Query Log for an HSQLDB in-memory setup

    - by shipmaster
    We have a setup where we are using an embedded HSQLDB for backing Hibernate/JPA unit tests in java, and we are using the in-memory database mode since we simply want the database thrown away after the test run. My problem is that one of the tests is failing due to a constraint violation and HSQLDB lists the column as SYS_CT_286, and the query that appears in the log is the prepared statement where I cant see what the actual parameter values are (they are replaced by '?'). My questions are: 1- Is there a way in which I can see the actual SQL being executed? (like the mysql query log for example?). 2- What exactly is SYS_CT_286? it is not one of my columns, is it a generated column? is there something obvious that may be wrong with it? Thanks.

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  • FxCop giving a warning on private constructor CA1823 and CA1053

    - by Luis Sánchez
    I have a class that looks like the following: Public Class Utilities Public Shared Function blah(userCode As String) As String 'doing some stuff End Function End Class I'm running FxCop 10 on it and it says: "Because type 'Utilities' contains only 'static' ( 'Shared' in Visual Basic) members, add a default private constructor to prevent the compiler from adding a default public constructor." Ok, you're right Mr. FxCop, I'll add a private constructor: Private Utilities() Now I'm having: "It appears that field 'Utilities.Utilities' is never used or is only ever assigned to. Use this field or remove it." Any ideas of what should I do to get rid of both warnings?

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  • PHP Initialising strings as boolean first

    - by Anriëtte Myburgh
    I'm in the habit of initialising variables in PHP to false and then applying whatever (string, boolean, float) value to it later. Which would you reckon is better? $name = false; if (condition == true) { $name = $something_else; } if ($name) { …do something… } vs. $name =''; if (condition == true) { $name = $something_else; } if (!empty($name)) { …do something… } Which would you reckon can possibly give better performance? Which method would you use?

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  • Optimize code performance when odd/even threads are doing different things in CUDA

    - by Orion Nebula
    Hi all! I have two large vectors, I am trying to do some sort of element multiplication, where an even-numbered element in the first vector is multiplied by the next odd-numbered element in the second vector .... and where the odd-numbered element in the first vector is multiplied by the preceding even-numbered element in the second vector Ex. vector 1 is V1(1) V1(2) V1(3) V1(4) vector 2 is V2(1) V2(2) V2(3) V2(4) V1(1) * V2(2) V1(3) * V2(4) V1(2) * V2(1) V1(4) * V2(3) I have written a Cuda code to do this: (Pds has the elements of the first vector in shared memory, Nds the second Vector) //instead of using %2 .. i check for the first bit to decide if number is odd/even -- faster if ((tx & 0x0001) == 0x0000) Nds[tx+1] = Pds[tx] * Nds[tx+1]; else Nds[tx-1] = Pds[tx] * Nds[tx-1]; __syncthreads(); Is there anyway to further accelerate this code or avoid divergence ? Thanks

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  • Optimizing a Soundex Query for finding similar names

    - by xkingpin
    My application will offer a list of suggestions for English names that "sound like" a given typed name. The query will need to be optimized and return results as quick as possible. Which option would be most optimal for returning results quickly. (Or your own suggestion if you have one) A. Generate the Soundex Hash and store it in the "Names" table then do something like the following: (This saves generating the soundex hash for at least every row in my db per query right?) select name from names where NameSoundex = Soundex('Ann') B. Use the Difference function (This must generate the soundex for every name in the table?) select name from names where Difference(name, 'Ann') = 3 C. Simple comparison select name from names where Soundex(name) = Soundex('Ann') Option A seems like to me it would be the fastest to return results because it only generates the Soundex for one string then compares to an indexed column "NameSoundex" Option B should give more results than option A because the name does not have to be an exact match of the soundex, but could be slower Assuming my table could contain millions of rows, what would yield the best results?

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  • MySQL efficiency as it relates to the database/table size

    - by mlissner
    I'm building a system using django, Sphinx and MySQL that's very quickly becoming quite large. The database currently has about 2000 rows, and I've written a program that's going to populate it with another 40,000 rows in a couple days. Since the database is live right now, and since I've never had a database with this much information in it, I'm worried about some things: Is adding all these rows going to seriously degrade the efficiency of my django app? Will I need to go back through it and optimize all my database calls so they're doing things more cleverly? Or will this make the database slow all around to the extent that I can't do anything about it at all? If you scoff at my 40k rows, then, my next question is, at what point SHOULD I be concerned? I will likely be adding another couple hundred thousand soon, so I worry, and I fret. How is sphinx going to feel about all this? Is it going to freak out when it realizes it has to index all this data? Or will it be fine? Is this normal for it? If it is, at what point should I be concerned that it's too much data for Sphinx? Thanks for any thoughts.

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  • How to write a SQL query for numerous conditions with lots of fields in ASP.NET

    - by Yongwei Xing
    Hi all I have a ASP.NET site. There is a table in the SQL Server with more than 30 fields. I need make a page on which there are many filters to query data from database based on the filters you select or input. One filter for one fields in the database. The filter would be dropdown list, textbox,checkbox or listbox. If you do not choose one filter, it means select all for this field. So there are lots of combination for these fields. Is there any simple way to write such page and query for this requirement? Best Regards,

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  • DBnull in Linq query causing problems

    - by nat
    hi there i am doing a query thus: int numberInInterval = (from dsStatistics.J2RespondentRow item in jStats.J2Respondent where item.EndTime > dtIntervalLower && item.EndTime <= dtIntervalUpper select item).count(); there appear to be some dbnulls in the endtime column.. any way i can avoid these? tried adding && where item.endtime != null.. and even != dbnull.value do i have to do a second (first) query to grab all that arent null then run the above one? im sure its super simple fix, but im still missing it.. as per thanks nat

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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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  • Get multiple records with one query

    - by Lewy
    User table: name lastname Bob Presley Jamie Cox Lucy Bush Find users q = Query.new("Bob Presley, Cox, Lucy") q.find_users => {0=>{:name=>"Bob", :lastname=>"Presley"}, 1=>{:lastname=>"Cox"}, 2=>{:name=>"Lucy"}} Question: I've got hash with few names and lastnames. I need to build Activerecord query to fetch all users from that hash. I can do object = [] hash = q.find_users hash.each do |data| #check if data[:lastname] and data[:name] exist # object << User.where(:name => ..., :lastname => ...) end But I think it is higly inefficient. How should I do this ?

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  • SQL Server 2005 - query with case statement

    - by user329266
    Trying to put a single query together to be used eventually in a SQL Server 2005 report. I need to: Pull in all distinct records for values in the "eventid" column for a time frame - this seems to work. For each eventid referenced above, I need to search for all instances of the same eventid to see if there is another record with TaskName like 'review1%'. Again, this seems to work. This is where things get complicated: For each record where TaskName is like review1, I need to see if another record exists with the same eventid and where TaskName='End'. Utimately, I need a count of how many records have TaskName like 'review1%', and then how many have TaskName like 'review1%' AND TaskName='End'. I would think this could be accomplished by setting a new value for each record, and for the eventid, if a record exists with TaskName='End', set to 1, and if not, set to 0. The query below seems to accomplish item #1 above: SELECT eventid, TimeStamp, TaskName, filepath FROM (SELECT eventid, TimeStamp, filepath, TaskName, ROW_NUMBER() OVER(PARTITION BY eventid ORDER BY TimeStamp DESC) AS seq FROM eventrecords where ((TimeStamp >= '2010-4-1 00:00:00.000') and (TimeStamp <= '2010-4-21 00:00:00.000'))) AS T WHERE seq = 1 order by eventid And the query below seems to accomplish #2: SELECT eventid, TimeStamp, TaskName, filepath FROM (SELECT eventid, TimeStamp, filepath, TaskName, ROW_NUMBER() OVER(PARTITION BY eventid ORDER BY TimeStamp DESC) AS seq FROM eventrecords where ((TimeStamp >= '2010-4-1 00:00:00.000') and (TimeStamp <= '2010-4-21 00:00:00.000')) and TaskName like 'Review1%') AS T WHERE seq = 1 order by eventid This will bring back the eventid's that also have a TaskName='End': SELECT eventid, TimeStamp, TaskName, filepath FROM (SELECT eventid, TimeStamp, filepath, TaskName, ROW_NUMBER() OVER(PARTITION BY eventid ORDER BY TimeStamp DESC) AS seq FROM eventrecords where ((TimeStamp >= '2010-4-1 00:00:00.000') and (TimeStamp <= '2010-4-21 00:00:00.000')) and TaskName like 'Review1%') AS T WHERE seq = 1 and eventid in (Select eventid from eventrecords where TaskName = 'End') order by eventid So I've tried the following to TRY to accomplish #3: SELECT eventid, TimeStamp, TaskName, filepath FROM (SELECT eventid, TimeStamp, filepath, TaskName, ROW_NUMBER() OVER(PARTITION BY eventid ORDER BY TimeStamp DESC) AS seq FROM eventrecords where ((TimeStamp >= '2010-4-1 00:00:00.000') and (TimeStamp <= '2010-4-21 00:00:00.000')) and TaskName like 'Review1%') AS T WHERE seq = 1 and case when (eventid in (Select eventid from eventrecords where TaskName = 'End') then 1 else 0) as bit end order by eventid When I try to run this, I get: "Incorrect syntax near the keyword 'then'." Not sure what I'm doing wrong. Haven't seen any examples anywhere quite like this. I should mention that eventrecords has a primary key, but it doesn't seem to help anything when I include it, and I am not permitted to change the table. (ugh) I've received one suggestion to use a cursor and temporary table, but am not sure how badley that would bog down performance when the report is running. Thanks in advance.

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  • complex mysql query problem

    - by Scarface
    Hey guys I have a query that selects data and organizes but not in the correct order. What I want to do is select all the comments for a user in that week and sort it by each topic, then sort the cluster by the latest timestamp of each comment in their respective cluster. My current query selects the right data, but in seemingly random order. Does anyone have any ideas? select * from ( SELECT topic.topic_title, topic.topic_id FROM comments JOIN topic ON topic.topic_id=comments.topic_id WHERE comments.user='$user' AND comments.timestamp>$week order by comments.timestamp desc) derived_table group by topic_id

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  • How can I further optimize this color difference function?

    - by aLfa
    I have made this function to calculate color differences in the CIE Lab colorspace, but it lacks speed. Since I'm not a Java expert, I wonder if any Java guru around has some tips that can improve the speed here. The code is based on the matlab function mentioned in the comment block. /** * Compute the CIEDE2000 color-difference between the sample color with * CIELab coordinates 'sample' and a standard color with CIELab coordinates * 'std' * * Based on the article: * "The CIEDE2000 Color-Difference Formula: Implementation Notes, * Supplementary Test Data, and Mathematical Observations,", G. Sharma, * W. Wu, E. N. Dalal, submitted to Color Research and Application, * January 2004. * available at http://www.ece.rochester.edu/~gsharma/ciede2000/ */ public static double deltaE2000(double[] lab1, double[] lab2) { double L1 = lab1[0]; double a1 = lab1[1]; double b1 = lab1[2]; double L2 = lab2[0]; double a2 = lab2[1]; double b2 = lab2[2]; // Cab = sqrt(a^2 + b^2) double Cab1 = Math.sqrt(a1 * a1 + b1 * b1); double Cab2 = Math.sqrt(a2 * a2 + b2 * b2); // CabAvg = (Cab1 + Cab2) / 2 double CabAvg = (Cab1 + Cab2) / 2; // G = 1 + (1 - sqrt((CabAvg^7) / (CabAvg^7 + 25^7))) / 2 double CabAvg7 = Math.pow(CabAvg, 7); double G = 1 + (1 - Math.sqrt(CabAvg7 / (CabAvg7 + 6103515625.0))) / 2; // ap = G * a double ap1 = G * a1; double ap2 = G * a2; // Cp = sqrt(ap^2 + b^2) double Cp1 = Math.sqrt(ap1 * ap1 + b1 * b1); double Cp2 = Math.sqrt(ap2 * ap2 + b2 * b2); // CpProd = (Cp1 * Cp2) double CpProd = Cp1 * Cp2; // hp1 = atan2(b1, ap1) double hp1 = Math.atan2(b1, ap1); // ensure hue is between 0 and 2pi if (hp1 < 0) { // hp1 = hp1 + 2pi hp1 += 6.283185307179586476925286766559; } // hp2 = atan2(b2, ap2) double hp2 = Math.atan2(b2, ap2); // ensure hue is between 0 and 2pi if (hp2 < 0) { // hp2 = hp2 + 2pi hp2 += 6.283185307179586476925286766559; } // dL = L2 - L1 double dL = L2 - L1; // dC = Cp2 - Cp1 double dC = Cp2 - Cp1; // computation of hue difference double dhp = 0.0; // set hue difference to zero if the product of chromas is zero if (CpProd != 0) { // dhp = hp2 - hp1 dhp = hp2 - hp1; if (dhp > Math.PI) { // dhp = dhp - 2pi dhp -= 6.283185307179586476925286766559; } else if (dhp < -Math.PI) { // dhp = dhp + 2pi dhp += 6.283185307179586476925286766559; } } // dH = 2 * sqrt(CpProd) * sin(dhp / 2) double dH = 2 * Math.sqrt(CpProd) * Math.sin(dhp / 2); // weighting functions // Lp = (L1 + L2) / 2 - 50 double Lp = (L1 + L2) / 2 - 50; // Cp = (Cp1 + Cp2) / 2 double Cp = (Cp1 + Cp2) / 2; // average hue computation // hp = (hp1 + hp2) / 2 double hp = (hp1 + hp2) / 2; // identify positions for which abs hue diff exceeds 180 degrees if (Math.abs(hp1 - hp2) > Math.PI) { // hp = hp - pi hp -= Math.PI; } // ensure hue is between 0 and 2pi if (hp < 0) { // hp = hp + 2pi hp += 6.283185307179586476925286766559; } // LpSqr = Lp^2 double LpSqr = Lp * Lp; // Sl = 1 + 0.015 * LpSqr / sqrt(20 + LpSqr) double Sl = 1 + 0.015 * LpSqr / Math.sqrt(20 + LpSqr); // Sc = 1 + 0.045 * Cp double Sc = 1 + 0.045 * Cp; // T = 1 - 0.17 * cos(hp - pi / 6) + // + 0.24 * cos(2 * hp) + // + 0.32 * cos(3 * hp + pi / 30) - // - 0.20 * cos(4 * hp - 63 * pi / 180) double hphp = hp + hp; double T = 1 - 0.17 * Math.cos(hp - 0.52359877559829887307710723054658) + 0.24 * Math.cos(hphp) + 0.32 * Math.cos(hphp + hp + 0.10471975511965977461542144610932) - 0.20 * Math.cos(hphp + hphp - 1.0995574287564276334619251841478); // Sh = 1 + 0.015 * Cp * T double Sh = 1 + 0.015 * Cp * T; // deltaThetaRad = (pi / 3) * e^-(36 / (5 * pi) * hp - 11)^2 double powerBase = hp - 4.799655442984406; double deltaThetaRad = 1.0471975511965977461542144610932 * Math.exp(-5.25249016001879 * powerBase * powerBase); // Rc = 2 * sqrt((Cp^7) / (Cp^7 + 25^7)) double Cp7 = Math.pow(Cp, 7); double Rc = 2 * Math.sqrt(Cp7 / (Cp7 + 6103515625.0)); // RT = -sin(delthetarad) * Rc double RT = -Math.sin(deltaThetaRad) * Rc; // de00 = sqrt((dL / Sl)^2 + (dC / Sc)^2 + (dH / Sh)^2 + RT * (dC / Sc) * (dH / Sh)) double dLSl = dL / Sl; double dCSc = dC / Sc; double dHSh = dH / Sh; return Math.sqrt(dLSl * dLSl + dCSc * dCSc + dHSh * dHSh + RT * dCSc * dHSh); }

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  • explicit copy constructor or implicit parameter by value

    - by R Samuel Klatchko
    I recently read (and unfortunately forgot where), that the best way to write operator= is like this: foo &operator=(foo other) { swap(*this, other); return *this; } instead of this: foo &operator=(const foo &other) { foo copy(other); swap(*this, copy); return *this; } The idea is that if operator= is called with an rvalue, the first version can optimize away construction of a copy. So when called with a rvalue, the first version is faster and when called with an lvalue the two are equivalent. I'm curious as to what other people think about this? Would people avoid the first version because of lack of explicitness? Am I correct that the first version can be better and can never be worse?

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  • How do you control what your C compiler Optimizes?

    - by Jordan S
    I am writing the firmware for an embedded device in C using the Silicon Labs IDE and the SDCC compiler. The device architecture is based on the 8051 family. The function in question is shown below. The function is used to set the ports on my MCU to drive a stepper motor. It gets called in by an interrupt handler. The big switch statement just sets the ports to the proper value for the next motor step. The bottom part of the function looks at an input from a hall effect sensor and a number of steps moved in order to detect if the motor has stalled. The problem is, for some reason the second IF statement that looks like this if (StallDetector > (GapSize + 20)) { HandleStallEvent(); } always seems to get optimized out. If I try to put a breakpoint at the HandleStallEvent() call the IDE gives me a message saying "No Address Correlation to this line number". I am not really good enough at reading assembly to tell what it is doing but I have pasted a snippet from the asm output below. Any help would be much appreciated. void OperateStepper(void) { //static bit LastHomeMagState = HomeSensor; static bit LastPosMagState = PosSensor; if(PulseMotor) { if(MoveDirection == 1) // Go clockwise { switch(STEPPER_POSITION) { case 'A': STEPPER_POSITION = 'B'; P1 = 0xFD; break; case 'B': STEPPER_POSITION = 'C'; P1 = 0xFF; break; case 'C': STEPPER_POSITION = 'D'; P1 = 0xFE; break; case 'D': STEPPER_POSITION = 'A'; P1 = 0xFC; break; default: STEPPER_POSITION = 'A'; P1 = 0xFC; } //end switch } else // Go CounterClockwise { switch(STEPPER_POSITION) { case 'A': STEPPER_POSITION = 'D'; P1 = 0xFE; break; case 'B': STEPPER_POSITION = 'A'; P1 = 0xFC; break; case 'C': STEPPER_POSITION = 'B'; P1 = 0xFD; break; case 'D': STEPPER_POSITION = 'C'; P1 = 0xFF; break; default: STEPPER_POSITION = 'A'; P1 = 0xFE; } //end switch } //end else MotorSteps++; StallDetector++; if(PosSensor != LastPosMagState) { StallDetector = 0; LastPosMagState = PosSensor; } else { if (PosSensor == ON) { if (StallDetector > (MagnetSize + 20)) { HandleStallEvent(); } } else if (PosSensor == OFF) { if (StallDetector > (GapSize + 20)) { HandleStallEvent(); } } } } //end if PulseMotor } ... and the asm output for the the bottom part of this function... ; C:\SiLabs\Optec Programs\HSFW_HID_SDCC_2\MotionControl.c:653: if(PosSensor != LastPosMagState) mov c,_P1_4 jb _OperateStepper_LastPosMagState_1_1,00158$ cpl c 00158$: jc 00126$ C$MotionControl.c$655$3$7 ==. ; C:\SiLabs\Optec Programs\HSFW_HID_SDCC_2\MotionControl.c:655: StallDetector = 0; clr a mov _StallDetector,a mov (_StallDetector + 1),a C$MotionControl.c$657$3$7 ==. ; C:\SiLabs\Optec Programs\HSFW_HID_SDCC_2\MotionControl.c:657: LastPosMagState = PosSensor; mov c,_P1_4 mov _OperateStepper_LastPosMagState_1_1,c ret 00126$: C$MotionControl.c$661$2$8 ==. ; C:\SiLabs\Optec Programs\HSFW_HID_SDCC_2\MotionControl.c:661: if (PosSensor == ON) jb _P1_4,00123$ C$MotionControl.c$663$4$9 ==. ; C:\SiLabs\Optec Programs\HSFW_HID_SDCC_2\MotionControl.c:663: if (StallDetector > (MagnetSize + 20)) mov a,_MagnetSize mov r2,a rlc a subb a,acc mov r3,a mov a,#0x14 add a,r2 mov r2,a clr a addc a,r3 mov r3,a clr c mov a,r2 subb a,_StallDetector mov a,r3 subb a,(_StallDetector + 1) jnc 00130$ C$MotionControl.c$665$5$10 ==. ; C:\SiLabs\Optec Programs\HSFW_HID_SDCC_2\MotionControl.c:665: HandleStallEvent(); ljmp _HandleStallEvent 00123$: C$MotionControl.c$668$2$8 ==. ; C:\SiLabs\Optec Programs\HSFW_HID_SDCC_2\MotionControl.c:668: else if (PosSensor == OFF) jnb _P1_4,00130$ C$MotionControl.c$670$4$11 ==. ; C:\SiLabs\Optec Programs\HSFW_HID_SDCC_2\MotionControl.c:670: if (StallDetector > (GapSize + 20)) mov a,#0x14 add a,_GapSize mov r2,a clr a addc a,(_GapSize + 1) mov r3,a clr c mov a,r2 subb a,_StallDetector mov a,r3 subb a,(_StallDetector + 1) jnc 00130$ C$MotionControl.c$672$5$12 ==. ; C:\SiLabs\Optec Programs\HSFW_HID_SDCC_2\MotionControl.c:672: HandleStallEvent(); C$MotionControl.c$678$2$1 ==. XG$OperateStepper$0$0 ==. ljmp _HandleStallEvent 00130$: ret It looks to me like the compiler is NOT optimizing out this second if statement from the looks of the asm but if that is the case why does the IDE not allow me so set a breakpoint there? Maybe it's just a dumb IDE!

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  • HQL query for entity with max value

    - by Rob
    I have a Hibernate entity that looks like this (accessors ommitted for brevity): @Entity @Table(name="FeatureList_Version") @SecondaryTable(name="FeatureList", pkJoinColumns=@PrimaryKeyJoinColumn(name="FeatureList_Key")) public class FeatureList implements Serializable { @Id @Column(name="FeatureList_Version_Key") private String key; @Column(name="Name",table="FeatureList") private String name; @Column(name="VERSION") private Integer version; } I want to craft an HQL query that retrieves the most up to date version of a FeatureList. The following query sort of works: Select f.name, max(f.version) from FeatureList f group by f.name The trouble is that won't populate the key field, which I need to contain the key of the record with the highest version number for the given FeatureList. If I add f.key in the select it won't work because it's not in the group by or an aggregate and if I put it in the group by the whole thing stops working and it just gives me every version as a separate entity. So, can anybody help?

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  • Complicated idea - how to create car racing for my RPG game's players

    - by Donator
    So, I want to create car racing for my RPG game's players. Player can create race and choose how many participants can participate in race. After race is being created, other people can join it. When the maximum participants are collected, race begins. My idea, when the last participant joins, then instantly choose the winner (who's car is the best, that person wins), but how can I do it? If I choose to pick the winner after the last participant joins, then I have to put many queries in one page (select data from table, then delete the race, then select players' cars' statistics and pick the winner and then again, using mysql, send message to everyone). But this idea is really not optimal and it will lag cruelly for that last person. Maybe you have any ideas how I can avoid lag and make it more optimal. Thank you very much.

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  • Combine static files or load in parallel

    - by Niall Collins
    I am at present introducing code to my site to combine css and javascript files. Is there a way without having to include an external library to load javascript asynchronously or in parallel? I have read on some blogs that combining of files can be counter productive as the load of the http request can be large and its better to load multiple files in parallel. Opinions on this? I am caching my javascript/css. And would have thought it was better to combine rather than have multiple http requests.

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