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  • computing hash values, integral types versus struct/class

    - by aaa
    hello I would like to know if there is a difference in speed between computing hash value (for example std::map key) of primitive integral type, such as int64_t and pod type, for example struct { int16_t v[4]; };. I know this is going to implementation specific, so my question ultimately pertains to gnu standard library. Thanks

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  • Howto project a planar polygon on a plane in 3d-space

    - by sum1stolemyname
    I want to project my Polygon along a vector to a plane in 3d Space. I would preferably use a single transformation matrix to do this, but I don't know how to build a matrix of this kind. Given the plane's parameters (ax+by+cz+d), the world coordinates of my Polygon. As stated in the the headline, all vertices of my polygon lie in another plane. the direction vector along which to project my Polygon (currently the polygon's plane's normal vector) goal -a 4x4 transformation matrix which performs the required projection, or some insight on how to construct one myself

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  • Blank space after file extension -> weird FileInfo behaviour

    - by Axarydax
    Somehow a file has appeared in one of my directories, and it has space at the end of its extension - its name is "test.txt ". The weird thing is that Directory.GetFiles() returns me the path of this file, but I'm unable to retrieve file information with FileInfo class. The error manifests here: DirectoryInfo di = new DirectoryInfo("c:\\somedir"); FileInfo fi = di.GetFileSystemInfos("test*")[0] as FileInfo; //correctly fi.FullName is "c:\somedir\test.txt " //but fi.Exists==false (!) Is FileInfo class broken? Can I somehow retrieve information about this file? I really don't know how did that file appear on my file system, and I am unable to recreate some more of them. All of my attempts to create a new file with this type of extension have failed, but now my program is crashing when encoutering it. I can easily handle the exception when finding the file, but boy am I curious about this!

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  • Regex: Matching a space-joined list of words, excluding last whitespace

    - by Jesper
    How would I match a space separated list of words followed by whitespace and some optional numbers? I have this: >>> import re >>> m = re.match('(?P<words>(\w+\s+)+)(?P<num>\d+)?\r\n', 'Foo Bar 12345\r\n') >>> m.groupdict() {'num': '12345', 'words': 'Foo Bar '} I'd like the words group to not include the last whitespace(s) but I can't figure this one out. I could do a .strip() on the result but that's not as much fun :) Some strings to test and wanted result: 'Foo & Bar 555\r\n' => {'num': '555', 'words': 'Foo & Bar'} 'Hello World\r\n' => {'num': None, 'words': 'Hello World'} 'Spam 99\r\n' => {'num': 99, 'words': 'Spam'} 'Number 1 666\r\n' => {'num': 666, 'words': 'Number 1'}

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  • Polymorphic Numerics on .Net and In C#

    - by Bent Rasmussen
    It's a real shame that in .Net there is no polymorphism for numbers, i.e. no INumeric interface that unifies the different kinds of numerical types such as bool, byte, uint, int, etc. In the extreme one would like a complete package of abstract algebra types. Joe Duffy has an article about the issue: http://www.bluebytesoftware.com/blog/CommentView,guid,14b37ade-3110-4596-9d6e-bacdcd75baa8.aspx How would you express this in C#, in order to retrofit it, without having influence over .Net or C#? I have one idea that involves first defining one or more abstract types (interfaces such as INumeric - or more abstract than that) and then defining structs that implement these and wrap types such as int while providing operations that return the new type (e.g. Integer32 : INumeric; where addition would be defined as public Integer32 Add(Integer32 other) { return Return(Value + other.Value); } I am somewhat afraid of the execution speed of this code but at least it is abstract. No operator overloading goodness... Any other ideas? .Net doesn't look like a viable long-term platform if it cannot have this kind of abstraction I think - and be efficient about it. Abstraction is reuse.

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  • learning to type - tips for programmers?

    - by OrbMan
    After hunting and pecking for about 35 years, I have decided to learn to type. I am learning QWERTY and have learned about 2/3 of the letters so far. While learning, I have noticed how asymmeterical the keyboard is, which really bothers me. (I will probably switch to a symmetrical keyboard eventually, but for now am trying to do everything as standard and "correct" as possible.) Although I am not there yet in my lessons, it seems that many of the keys I am going to use as a C# web developer are supposed to be typed by the pinky of my right hand. Are there any typing patterns you have developed that are more ergonomic (or faster) when typing large volumes of code rife with braces, colons, semi-colons and quotes? Or, should I just accept the fact that every other key is going to be hit with my right pinky? It is not that speed is such a huge concern, as much as that it seems so inefficient to rely on one finger so much... As an example, some of the conventions I use as a hunt and pecker, like typing open and close braces right away with my index and middle finger, and then hitting the left arrow key to fill in the inner content, don't seem to work as well with just a pinky. What are some typing patterns using a standard QWERTY keyboard that work really well for you as a programmer?

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  • Please for efficient query

    - by user278618
    I want to have efficient query to get some rows from my table. Here is I think the best presentation of my table. -Somedate is not duplicated - it is date of modifiedon -a,b,c are parent ids, let say countryCode -1,2,3,4 are subparent, let say citycode -guids are id of rows -true, false are values of rows - one can name this column - freshAir a 1 GUID somedate true a 1 GUID somedate true a 2 GUID somedate false a 2 GUID somedate false b 3 GUID somedate false b 3 GUID somedate false b 3 GUID somedate false b 4 GUID somedate false c 5 GUID somedate true c 6 GUID somedate true c 6 GUID somedate false c 6 GUID somedate false c 7 GUID somedate false I want the most recent rows MAX(modifiedon) grouped by countrycode and citycode and in this groups I need elements which have another values (true, false). And in result I want: a 1 GUID somedate true a 2 GUID somedate false c 5 GUID somedate true c 6 GUID somedate false c 7 GUID somedate false Look that in result I don't want to have records with "b", because all rows have the same value (false). Best regards

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  • Struct in C, are they efficient?

    - by pygabriel
    I'm reading some C code like that: double function( int lena,double xa,double ya, double za, double *acoefs, ..., int lenb,double xb,double yb, double zb, double *bcoefs, ..., same for c, same for d ) This function is called in the code mor than 100.000 times so it's performance-critical. I'm trying to extend this code but I want to know if it's efficient or not (and how much this influences the speed) to encapsulate all the parameters in a struct like this struct PGTO { int len; double x,y,z ; double *acoefs } and then access the parameters in the function.

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  • How can I efficiently group a large list of URLs by their host name in Perl?

    - by jesper
    I have text file that contains over one million URLs. I have to process this file in order to assign URLs to groups, based on host address: { 'http://www.ex1.com' = ['http://www.ex1.com/...', 'http://www.ex1.com/...', ...], 'http://www.ex2.com' = ['http://www.ex2.com/...', 'http://www.ex2.com/...', ...] } My current basic solution takes about 600 MB of RAM to do this (size of file is about 300 MB). Could you provide some more efficient ways? My current solution simply reads line by line, extracts host address by regex and puts the url into a hash. EDIT Here is my implementation (I've cut off irrelevant things): while($line = <STDIN>) { chomp($line); $line =~ /(http:\/\/.+?)(\/|$)/i; $host = "$1"; push @{$urls{$host}}, $line; } store \%urls, 'out.hash';

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  • Python: How efficient is subtring extraction?

    - by Cameron
    I've got the entire contents of a text file (at least a few KB) in string myStr. Will the following code create a copy of the string (less the first character) in memory? myStr = myStr[1:] I'm hoping it just refers to a different location in the same internal buffer. If not, is there a more efficient way to do this? Thanks!

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  • ASP.NET NamingContainer naming convention

    - by EOLeary
    The Background Hello! I'm working on a project in which the client has required a lot of things to happen on a single page, and this has resulted in a rather large blob of HTML being rendered out to the client browser. The main issue is with input tags (where runat="server" attribute is set), these tend to cause a drastic increase in markup size due to validation, updatepanel triggers, viewstate, and the control markup itself. I've done what I can to reduce the amount of triggers I'm using, I'm compressing the viewstate (to something like 8% of the original viewstate size), I've gotten rid of a lot of ASP.NET Validators and rolled my own, and and I've been using ClientIdMode to reduce the length of the ID attributes of many asp.net elements. All of these combined significantly reduces the amount of HTML being sent to the client, (for example going from 2 megabytes for a request down to 500-600 kb - these are HUGE pages, mind you). The Issue One area which I've been having trouble reducing is simply the auto-generated 'name' attribute of input elements. <input name="ctl00$ctl00$ctl00$_main$_main$_bodyMatterPhase$_phaseTree$ctl00$_taskTree$ctl00$_taskDetails$_detailList$ctrl0$_row$_descriptionText" type="text" value="Investigation Week 1" maxlength="100" id="_taskTree_0__taskDetails_0__detailList_0__row_0__descriptionText_0" style="width:170px;"> As you can see above, the name attribute is 139 out of 297 characters, that's almost 50% of the tag markup taken up by that HUGE name. Does anyone have any ideas on how to stick a hook in somewhere in ASP.NET where I can somehow translate these or generate them differently; say instead of ctl00$ctl00$ctl00$_main$_main$_bodyMatterPhase$_phaseTree$ctl00$_taskTree$ctl00$_taskDetails$_detailList$ctrl0$_row$_descriptionText, it could be a GUID like 0x0AEED4B6445A11E08F873606E0D72085, which is 105 characters shorter. Any help would be greatly appreciated!

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  • MySQL slow query

    - by andrhamm
    SELECT items.item_id, items.category_id, items.title, items.description, items.quality, items.type, items.status, items.price, items.posted, items.modified, zip_code.state_prefix, zip_code.city, books.isbn13, books.isbn10, books.authors, books.publisher FROM ( ( items LEFT JOIN bookitems ON items.item_id = bookitems.item_id ) LEFT JOIN books ON books.isbn13 = bookitems.isbn13 ) LEFT JOIN zip_code ON zip_code.zip_code = items.item_zip WHERE items.rid = $rid` I am running this query to get the list of a user's items and their location. The zip_code table has over 40k records and this might be the issue. It currently takes up to 15 seconds to return a list of about 20 items! What can I do to make this query more efficient?

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  • Most efficient way to combine two objects in C#

    - by Dested
    I have two objects that can be represented as an int, float, bool, or string. I need to perform an addition on these two objects with the results being the same thing c# would produce as a result. For instance 1+"Foo" would equal the string "1Foo", 2+2.5 would equal the float 5.5, and 3+3 would equal the int 6 . Currently I am using the code below but it seems like incredible overkill. Can anyone simplify or point me to some way to do this efficiently? private object Combine(object o, object o1) { float left = 0; float right = 0; bool isInt = false; string l = null; string r = null; if (o is int) { left = (int)o; isInt = true; } else if (o is float) { left = (float)o; } else if (o is bool) { l = o.ToString(); } else { l = (string)o; } if (o1 is int) { right = (int)o1; } else if (o is float) { right = (float)o1; isInt = false; } else if (o1 is bool) { r = o1.ToString(); isInt = false; } else { r = (string)o1; isInt = false; } object rr; if (l == null) { if (r == null) { rr = left + right; } else { rr = left + r; } } else { if (r == null) { rr = l + right; } else { rr = l + r; } } if (isInt) { return Convert.ToInt32(rr); } return rr; }

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  • How to prevent Windows XP from stealing my input Ctrl-Space which is meant for Emacs

    - by Dean
    I am learning and using Emacs. What I found annoying is that Ctrl-Space input will be stolen by Windows XP to switch the language bar instead of setting the mark in Emacs. The "language bar" is the native input languages selection such as Chinese keyboard other than English keyboard. Is there a way to temporarily prevent XP from stealing it? I have disabled the language bar from "Regional and language options" from Control Panel but the problem still exists. It doesn't happen on my Windows 2000 desktop at office but it happens on my work Windows XP laptop. Thank you very much.

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  • How do you balance business process changes against the challenges of changing software?

    - by Achilles
    In my admittedly young career I've found myself writing code to support quirky business rules and processes. Inevitably these changes were always in some massively difficult code base and caused many issues. My question has a couple of parts: While software is a tool for businesses to make their lives easier, at what point do we as developers suggest a change in business process rather than in the software as the "magic bullet" to solve a particular problem. How do we as developers evangelize a certain level of reverence for the software as well as the difficulty involved in making changes simply to support the quirks of the business? I understand that these changes in business processes promote our industry, but in an analogy my father would understand: Which is easier, to melt down a hammer to forge a screwdriver to drive screws or to simply use nails since your hammer is already awesome...?

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  • Objective C -- property lists or text files?

    - by William Jockusch
    I need to import a list of about 40,000 words into my Iphone app. The list will be the same every time the app starts. It seems that property lists and text files are reasonable options. Any reason to prefer one over the other? For reasons I don't understand, finder says the property list on my mac is 1MB, while the text file is only 328K. The property list is an NSMutableArray of NSMutableArrays of NSStrings. The text file is a plain txt file. But amount of time the app takes to start up is also important. If I read in a text file, my app would have to do some simple processing on it each time it starts. Thanks.

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  • How to effectively copy an array in java ?

    - by Tony
    The toArray method in ArrayList , Bloch uses both System.arraycopy and Arrays.copyOf to copy an array . public <T> T[] toArray(T[] a) { if (a.length < size) // Make a new array of a's runtime type, but my contents: return (T[]) Arrays.copyOf(elementData, size, a.getClass()); System.arraycopy(elementData, 0, a, 0, size); if (a.length > size) a[size] = null; return a; } How to compare these two copy method , when to use which ? Thanks.

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  • How do you energize yourself when working alone on a project?

    - by Stephane
    I am working in an environment with a very small team (3 developers only) and each of us have been assigned a different project, without counting support tasks. I know this is a bad business practice and that we should all work on a single project at a time, and then move on to the next one (Already explained to the management on how much it sucks). So don't answer me that we should work all together on one project at a time. Energizing the work when in a team is mostly pair programming we did that when less project were thrown at us and that was great. What I would like to know is how you energize your work when working alone on a project. Do you follow any particular practice?

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  • Is there a more efficient way to run enum values through a switch-case statement in C# than this?

    - by C Patton
    I was wondering if there was a more efficient (efficient as in simpler/cleaner code) way of making a case statement like the one below... I have a dictionary. Its key type is an Enum and its value type is a bool. If the boolean is true, I want to change the color of a label on a form. The variable names were changed for the example. Dictionary<String, CustomType> testDict = new Dictionary<String, CustomType>(); //populate testDict here... Dictionary<MyEnum, bool> enumInfo = testDict[someString].GetEnumInfo(); //GetEnumInfo is a function that iterates through a Dictionary<String, CustomType> //and returns a Dictionary<MyEnum, bool> foreach (KeyValuePair<MyEnum, bool> kvp in enumInfo) { switch (kvp.Key) { case MyEnum.Enum1: if (someDictionary[kvp.Key] == true) { Label1.ForeColor = Color.LimeGreen; } else { Label1.ForeColor = Color.Red; } break; case MyEnum.Enum2: if (someDictionary[kvp.Key] == true) { Label2.ForeColor = Color.LimeGreen; } else { Label2.ForeColor = Color.Red; } break; } } So far, MyEnum has 8 different values.. which means I have 8 different case statements.. I know there must be an easier way to do this, I just can't conceptualize it in my head. If anyone could help, I'd greatly appreciate it. I love C# and I learn new things every day.. I absorb it like a sponge :) -CP

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  • C# String.Replace with a start/index (Added my (slow) implementation)

    - by Chris T
    I'd like an efficient method that would work something like this EDIT: Sorry I didn't put what I'd tried before. I updated the example now. // Method signature, Only replaces first instance or how many are specified in max public int MyReplace(ref string source,string org, string replace, int start, int max) { int ret = 0; int len = replace.Length; int olen = org.Length; for(int i = 0; i < max; i++) { // Find the next instance of the search string int x = source.IndexOf(org, ret + olen); if(x > ret) ret = x; else break; // Insert the replacement source = source.Insert(x, replace); // And remove the original source = source.Remove(x + len, olen); // removes original string } return ret; } string source = "The cat can fly but only if he is the cat in the hat"; int i = MyReplace(ref source,"cat", "giraffe", 8, 1); // Results in the string "The cat can fly but only if he is the giraffe in the hat" // i contains the index of the first letter of "giraffe" in the new string The only reason I'm asking is because my implementation I'd imagine getting slow with 1,000s of replaces.

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  • What's wrong with my logic here?

    - by stu
    In java they say don't concatenate Strings, instead you should make a stringbuffer and keep adding to that and then when you're all done, use toString() to get a String object out of it. Here's what I don't get. They say do this for performance reasons, because concatenating strings makes lots of temporary objects. But if the goal was performance, then you'd use a language like C/C++ or assembly. The argument for using java is that it is a lot cheaper to buy a faster processor than it is to pay a senior programmer to write fast efficient code. So on the one hand, you're supposed let the hardware take care of the inefficiencies, but on the other hand, you're supposed to use stringbuffers to make java more efficient. While I see that you can do both, use java and stringbuffers, my question is where is the flaw in the logic that you either use a faster chip or you spent extra time writing more efficient software.

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  • Generics and Performance question.

    - by Tarmon
    Hey Everyone, I was wondering if anyone could look over a class I wrote, I am receiving generic warnings in Eclipse and I am just wondering if it could be cleaned up at all. All of the warnings I received are surrounded in ** in my code below. The class takes a list of strings in the form of (hh:mm AM/PM) and converts them into HourMinute objects in order to find the first time in the list that comes after the current time. I am also curious about if there are more efficient ways to do this. This works fine but the student in me just wants to find out how I could do this better. public class FindTime { private String[] hourMinuteStringArray; public FindTime(String[] hourMinuteStringArray){ this.hourMinuteStringArray = hourMinuteStringArray; } public int findTime(){ HourMinuteList hourMinuteList = convertHMStringArrayToHMArray(hourMinuteStringArray); Calendar calendar = new GregorianCalendar(); int hour = calendar.get(Calendar.HOUR_OF_DAY); int minute = calendar.get(Calendar.MINUTE); HourMinute now = new HourMinute(hour,minute); int nearestTimeIndex = findNearestTimeIndex(hourMinuteList, now); return nearestTimeIndex; } private int findNearestTimeIndex(HourMinuteList hourMinuteList, HourMinute now){ HourMinute current; int position = 0; Iterator<HourMinute> iterator = **hourMinuteList.iterator()**; while(iterator.hasNext()){ current = (HourMinute) iterator.next(); if(now.compareTo(current) == -1){ return position; } position++; } return position; } private static HourMinuteList convertHMStringArrayToHMArray(String[] times){ FindTime s = new FindTime(new String[1]); HourMinuteList list = s.new HourMinuteList(); String[] splitTime = new String[3]; for(String time : times ){ String[] tempFirst = time.split(":"); String[] tempSecond = tempFirst[1].split(" "); splitTime[0] = tempFirst[0]; splitTime[1] = tempSecond[0]; splitTime[2] = tempSecond[1]; int hour = Integer.parseInt(splitTime[0]); int minute = Integer.parseInt(splitTime[1]); HourMinute hm; if(splitTime[2] == "AM"){ hm = s.new HourMinute(hour,minute); } else if((splitTime[2].equals("PM")) && (hour < 12)){ hm = s.new HourMinute(hour + 12,minute); } else{ hm = s.new HourMinute(hour,minute); } **list.add(hm);** } return list; } class **HourMinuteList** extends **ArrayList** implements RandomAccess{ } class HourMinute implements **Comparable** { int hour; int minute; public HourMinute(int hour, int minute) { setHour(hour); setMinute(minute); } int getMinute() { return this.minute; } String getMinuteString(){ if(this.minute < 10){ return "0" + this.minute; }else{ return "" + this.minute; } } int getHour() { return this.hour; } void setHour(int hour) { this.hour = hour; } void setMinute(int minute) { this.minute = minute; } @Override public int compareTo(Object aThat) { if (aThat instanceof HourMinute) { HourMinute that = (HourMinute) aThat; if (this.getHour() == that.getHour()) { if (this.getMinute() > that.getMinute()) { return 1; } else if (this.getMinute() < that.getMinute()) { return -1; } else { return 0; } } else if (this.getHour() > that.getHour()) { return 1; } else if (this.getHour() < that.getHour()) { return -1; } else { return 0; } } return 0; } } If you have any questions let me know. Thanks, Rob

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  • How do I make the following interaction with mySQL more efficient?

    - by Travis
    I've got an array that contains combinations of unique MySql IDs: For example: [ [1,10,11], [2,10], [3,10,12], [3,12,13,20], [4,12] ] In total there are a couple hundred different combinations of IDs. Some of these combinations are "valid" and some are not. For example, [1,10,11] may be a valid combination, whereas [3,10,12] may be invalid. Combinations are valid or invalid depending on how the data is arranged in the database. Currently I am using a SELECT statement to determine whether or not a specific combination of IDs is valid. It looks something like this: SELECT id1 FROM table WHERE id2 IN ($combination) GROUP BY id1 HAVING COUNT(distinct id2) = $number ...where $combination is one possible combination of IDs (eg 1,10,11) and $number is the number of IDs in that combination (in this case, 3). An invalid combination will return 0 rows. A valid combination will return 1 or more rows. However, to solve the entire set of possible combinations means looping a couple hundred SELECT statements, which I would rather not be doing. I am wondering: Are there any tricks for making this more efficient? Is it possible to submit the entire dataset to mySQL in one go, and have mySQL iterate through it? Any suggestions would be much appreciated. Thanks in advance!

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