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• How toget a list of "fastest miles" from a set of GPS Points

  - by santiagobasulto

  I'm trying to solve a weird problem. Maybe you guys know of some algorithm that takes care of this. I have data for a cargo freight truck and want to extract some data. Suppose I've got a list of sorted points that I get from the GPS. That's the route for that truck: [ { "lng": "-111.5373066", "lat": "40.7231711", "time": "1970-01-01T00:00:04Z", "elev": "1942.1789265256325" }, { "lng": "-111.5372056", "lat": "40.7228762", "time": "1970-01-01T00:00:07Z", "elev": "1942.109892409177" } ] Now, what I want to get is a list of the "fastest miles". I'll do an example: Given the points: A, B, C, D, E, F the distance from point A to point B is 1 mile, and the cargo took 10:32 minutes. From point B to point D i've got other mile, and the cargo took 10 minutes, etc. So, i need a list sorted by time. Similar to: B -> D: 10 A -> B: 10:32 D -> F: 11:02 Do you know any efficient algorithm that let me calculate that? Thank you all. PS: I'm using Python. EDIT: I've got the distance. I know how to calculate it and there are plenty of posts to do that. What I need is an algorithm to tokenize by mile and get speed from that. Having a distance function is not helpful enough: results = {} for point in points: aux_points = points.takeWhile(point>n) #This doesn't exist, just trying to be simple for aux_point in aux_points: d = distance(point, aux_point) if d == 1_MILE: time_elapsed = time(point, aux_point) results[time_elapsed] = (point, aux_point) I'm still doing some pretty inefficient calculations.

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• Perl Regex - Condensing groups of find/replace

  - by brydgesk

  I'm using Perl to perform some file cleansing, and am running into some performance issues. One of the major parts of my code involves standardizing name fields. I have several sections that look like this: sub substitute_titles { my ($inStr) = @_; ${$inStr} =~ s/ PHD./ PHD /; ${$inStr} =~ s/ P H D / PHD /; ${$inStr} =~ s/ PROF./ PROF /; ${$inStr} =~ s/ P R O F / PROF /; ${$inStr} =~ s/ DR./ DR /; ${$inStr} =~ s/ D.R./ DR /; ${$inStr} =~ s/ HON./ HON /; ${$inStr} =~ s/ H O N / HON /; ${$inStr} =~ s/ MR./ MR /; ${$inStr} =~ s/ MRS./ MRS /; ${$inStr} =~ s/ M R S / MRS /; ${$inStr} =~ s/ MS./ MS /; ${$inStr} =~ s/ MISS./ MISS /; } I'm passing by reference to try and get at least a little speed, but I fear that running so many (literally hundreds) of specific string replaces on tens of thousands (likely hundreds of thousands eventually) of records is going to hurt the performance. Is there a better way to implement this kind of logic than what I'm doing currently? Thanks Edit: Quick note, not all the replace functions are just removing periods and spaces. There are string deletions, soundex groups, etc.

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• Save memory in Python. How to iterate over the lines and save them efficiently with a 2million line

  - by skyl

  I have a tab-separated data file with a little over 2 million lines and 19 columns. You can find it, in US.zip: http://download.geonames.org/export/dump/. I started to run the following but with for l in f.readlines(). I understand that just iterating over the file is supposed to be more efficient so I'm posting that below. Still, with this small optimization, I'm using 10% of my memory on the process and have only done about 3% of the records. It looks like, at this pace, it will run out of memory like it did before. Also, the function I have is very slow. Is there anything obvious I can do to speed it up? Would it help to del the objects with each pass of the for loop? def run(): from geonames.models import POI f = file('data/US.txt') for l in f: li = l.split('\t') try: p = POI() p.geonameid = li[0] p.name = li[1] p.asciiname = li[2] p.alternatenames = li[3] p.point = "POINT(%s %s)" % (li[5], li[4]) p.feature_class = li[6] p.feature_code = li[7] p.country_code = li[8] p.ccs2 = li[9] p.admin1_code = li[10] p.admin2_code = li[11] p.admin3_code = li[12] p.admin4_code = li[13] p.population = li[14] p.elevation = li[15] p.gtopo30 = li[16] p.timezone = li[17] p.modification_date = li[18] p.save() except IndexError: pass if __name__ == "__main__": run()

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• linux new/delete, malloc/free large memory blocks

  - by brian_mk

  Hi folks, We have a linux system (kubuntu 7.10) that runs a number of CORBA Server processes. The server software uses glibc libraries for memory allocation. The linux PC has 4G physical memory. Swap is disabled for speed reasons. Upon receiving a request to process data, one of the server processes allocates a large data buffer (using the standard C++ operator 'new'). The buffer size varies depening upon a number of parameters but is typically around 1.2G Bytes. It can be up to about 1.9G Bytes. When the request has completed, the buffer is released using 'delete'. This works fine for several consecutive requests that allocate buffers of the same size or if the request allocates a smaller size than the previous. The memory appears to be free'd ok - otherwise buffer allocation attempts would eventually fail after just a couple of requests. In any case, we can see the buffer memory being allocated and freed for each request using tools such as KSysGuard etc. The problem arises when a request requires a buffer larger than the previous. In this case, operator 'new' throws an exception. It's as if the memory that has been free'd from the first allocation cannot be re-allocated even though there is sufficient free physical memory available. If I kill and restart the server process after the first operation, then the second request for a larger buffer size succeeds. i.e. killing the process appears to fully release the freed memory back to the system. Can anyone offer an explanation as to what might be going on here? Could it be some kind of fragmentation or mapping table size issue? I am thinking of replacing new/delete with malloc/free and use mallopt to tune the way the memory is being released to the system. BTW - I'm not sure if it's relevant to our problem, but the server uses Pthreads that get created and destroyed on each processing request. Cheers, Brian.

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• making check boxes clickable once in javascript?

  - by OVERTONE

  Sorry but im an absolute noob with javascript. Ive made a form for a simple quiz but cant figure out how to make radio's only click once. I can select two or three buttons as my answer. i want to change this. <form name = "Beginners Quiz"> <p>Film speed refers to:</p> <p><input type="radio" name="Answer 1" id="Answer1" value = "a" onclick = "recordAnswer(1,this.value"/>How long it takes to develop film. <br/> <p><input type="radio" name="Answer 2" id="Answer2" value = "b" onclick = "recordAnswer(1,this.value"/>How fast film moves through film-transport system. <br/> <p><input type="radio" name="Answer 3" id="Answer3" value = "c" onclick = "recordAnswer(1,this.value"/> How sensitive the film is to light. <br/> <p><input type="radio" name="Answer 4" id="Answer4" value = "d" onclick = "recordAnswer(1,this.value"/> None of these makes sense. <br/> ive been rooting around w3shcools tutorials to no avail. can someone shed some light?

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• Do fluent interfaces significantly impact runtime performance of a .NET application?

  - by stakx

  I'm currently occupying myself with implementing a fluent interface for an existing technology, which would allow code similar to the following snippet: using (var directory = Open.Directory(@"path\to\some\directory")) { using (var file = Open.File("foobar.html").In(directory)) { // ... } } In order to implement such constructs, classes are needed that accumulate arguments and pass them on to other objects. For example, to implement the Open.File(...).In(...) construct, you would need two classes: // handles 'Open.XXX': public static class OpenPhrase { // handles 'Open.File(XXX)': public static OpenFilePhrase File(string filename) { return new OpenFilePhrase(filename); } // handles 'Open.Directory(XXX)': public static DirectoryObject Directory(string path) { // ... } } // handles 'Open.File(XXX).XXX': public class OpenFilePhrase { internal OpenFilePhrase(string filename) { _filename = filename } // handles 'Open.File(XXX).In(XXX): public FileObject In(DirectoryObject directory) { // ... } private readonly string _filename; } That is, the more constituent parts statements such as the initial examples have, the more objects need to be created for passing on arguments to subsequent objects in the chain until the actual statement can finally execute. Question: I am interested in some opinions: Does a fluent interface which is implemented using the above technique significantly impact the runtime performance of an application that uses it? With runtime performance, I refer to both speed and memory usage aspects. Bear in mind that a potentially large number of temporary, argument-saving objects would have to be created for only very brief timespans, which I assume may put a certain pressure on the garbage collector. If you think there is significant performance impact, do you know of a better way to implement fluent interfaces?

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• Generate and merge data with python multiprocessing

  - by Bobby

  I have a list of starting data. I want to apply a function to the starting data that creates a few pieces of new data for each element in the starting data. Some pieces of the new data are the same and I want to remove them. The sequential version is essentially: def create_new_data_for(datum): """make a list of new data from some old datum""" return [datum.modified_copy(k) for k in datum.k_list] data = [some list of data] #some data to start with #generate a list of new data from the old data, we'll reduce it next newdata = [] for d in data: newdata.extend(create_new_data_for(d)) #now reduce the data under ".matches(other)" reduced = [] for d in newdata: for seen in reduced: if d.matches(seen): break #so we haven't seen anything like d yet seen.append(d) #now reduced is finished and is what we want! I want to speed this up with multiprocessing. I was thinking that I could use a multiprocessing.Queue for the generation. Each process would just put the stuff it creates on, and when the processes are reducing the data, they can just get the data from the Queue. But I'm not sure how to have the different process loop over reduced and modify it without any race conditions or other issues. What is the best way to do this safely? or is there a different way to accomplish this goal better?

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• Performance degrades for more than 2 threads on Xeon X5355

  - by zoolii

  Hi All, I am writing an application using boost threads and using boost barriers to synchronize the threads. I have two machines to test the application. Machine 1 is a core2 duo (T8300) cpu machine (windows XP professional - 4GB RAM) where I am getting following performance figures : Number of threads :1 , TPS :21 Number of threads :2 , TPS :35 (66 % improvement) further increase in number of threads decreases the TPS but that is understandable as the machine has only two cores. Machine 2 is a 2 quad core ( Xeon X5355) cpu machine (windows 2003 server with 4GB RAM) and has 8 effective cores. Number of threads :1 , TPS :21 Number of threads :2 , TPS :27 (28 % improvement) Number of threads :4 , TPS :25 Number of threads :8 , TPS :24 As you can see, performance is degrading after 2 threads (though it has 8 cores). If the program has some bottle neck , then for 2 thread also it should have degraded. Any idea? , Explanations ? , Does the OS has some role in performance ? - It seems like the Core2duo (2.4GHz) scales better than Xeon X5355 (2.66GHz) though it has better clock speed. Thank you -Zoolii

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• delete row from result set in web sql with javascript

  - by Kaijin

  I understand that the result set from web sql isn't quite an array, more of an object? I'm cycling through a result set and to speed things up I'd like to remove a row once it's been found. I've tried "delete" and "splice", the former does nothing and the latter throws an error. Here's a piece of what I'm trying to do, notice the delete on line 18: function selectFromReverse(reverseRay,suggRay){ var reverseString = reverseRay.toString(); db.transaction(function (tx) { tx.executeSql('SELECT votecount, comboid FROM counterCombos WHERE comboid IN ('+reverseString+') AND votecount>0', [], function(tx, results){ processSelectFromReverse(results,suggRay); }); }, function(){onError}); } function processSelectFromReverse(results,suggRay){ var i = suggRay.length; while(i--){ var j = results.rows.length; while(j--){ console.log('searching'); var found = 0; if(suggRay[i].reverse == results.rows.item(j).comboid){ delete results.rows.item(j); console.log('found'); found++; break; } } if(found == 0){ console.log('lost'); } } }

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• Using Partitions for a large MySQL table

  - by user293594

  An update on my attempts to implement a 505,000,000-row table on MySQL on my MacBook Pro: Following the advice given, I have partitioned my table, tr: i UNSIGNED INT NOT NULL, j UNSIGNED INT NOT NULL, A FLOAT(12,8) NOT NULL, nu BIGINT NOT NULL, KEY (nu), key (A) with a range on nu. nu ought to be a real number, but because I only have 6-d.p. accuracy and the maximum value of nu is 30000. I multiplied it by 10^8 made it a BIGINT - I gather one can't use FLOAT or DOUBLE values to PARTITION a MySQL table. Anyway, I have 15 partitions (p0: nu<25,000,000,000, p1: nu<50,000,000,000, etc.). I was thinking that this should speed up a typical to SELECT: SELECT * FROM tr WHERE nu>95000000000 AND nu<100000000000 AND A.>1. to something of the order of the same query on a table consisting of only the data in the relevant partition (<30 secs). But it's taking 30mins+ to return rows for queries within a partition and double that if the query is for rows spanning two (contiguous) partitions. I realise I could just have 15 different tables, and query them separately, but is there a way to do this 'automatically' with partitions? Has anyone got any suggestions?

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• Combining cache methods - memcache/disk based

  - by Industrial

  Hi! Here's the deal. We would have taken the complete static html road to solve performance issues, but since the site will be partially dynamic, this won't work out for us. What we have thought of instead is using memcache + eAccelerator to speed up PHP and take care of caching for the most used data. Here's our two approaches that we have thought of right now: Using memcache on all<< major queries and leaving it alone to do what it does best. Usinc memcache for most commonly retrieved data, and combining with a standard harddrive-stored cache for further usage. The major advantage of only using memcache is of course the performance, but as users increases, the memory usage gets heavy. Combining the two sounds like a more natural approach to us, even though the theoretical compromize in performance. Memcached appears to have some replication features available as well, which may come handy when it's time to increase the nodes. What approach should we use? - Is it stupid to compromize and combine the two methods? Should we insted be focusing on utilizing memcache and instead focusing on upgrading the memory as the load increases with the number of users? Thanks a lot!

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• RSA_sign and RSACryptoProvider.VerifySignature

  - by Miky D

  I'm trying to get up to speed on how to get some code that uses OpenSSL for cryptography, to play nice with another program that I'm writing in C#, using the Microsoft cryptography providers available in .NET. More to the point, I'm trying to have the C# program verify an RSA message signature generated by the OpenSSL code. The code that generates the signature looks something like this: // Code in C, using the OpenSSL RSA implementation char msgToSign[] = "Hello World"; // the message to be signed char signature[RSA_size(rsa)]; // buffer that will hold signature int slen = 0; // will contain signature size // rsa is an OpenSSL RSA context, that's loaded with the public/private key pair memset(signature, 0, sizeof(signature)); RSA_sign(NID_sha1 , (unsigned char*)msgToSign , strlen(msgToSign) , signature , &slen , rsa); // now signature contains the message signature // and can be verified using the RSA_verify counterpart // .. I would like to verify the signature in C# In C#, I would do the following: import the other side's public key into an RSACryptoServiceProvider object receive the message and it's signature try to verify the signature I've got the first two parts working (I've verified that the public key is loading properly because I managed to send an RSA encrypted text from the C# code to the OpenSSL code in C and successfully have it decrypted) In order to verify the signature in C#, I've tried using the: VerifySignature method of the RSACryptoServiceProvider but that didn't work. And digging around the internet I was only able to find some vague information pointing out that .NET uses a different method for generating the signature than OpenSSL does. So, does anybody know how to accomplish this?

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• ColdFusion 8 Slow Performance

  - by JoeBob

  We have started a new CF8 app and it is running dog slow. A test where we go around ColdFusion (queries within a database utility) show normal speed (80ms). CF8 returns the same query in something like 60 to 80 seconds! I have been looking online and seeing lots of posts about CF8 and performance problems, but don't get any overall sense of a solution; just lots of people trying things and saying that they didn't have the problem with CF7. We are also seeing instability on the server, and some errors relating to garbage collection and the memory heap. We have a number of other applications running on CF8 and they perform adequately...our programmer is not an expert or a guru, he just plugs away. We have isolated this down to a single query that takes forever to return, so it is not a complicated test. Are there any known CF8 problems or obvious tweaks that we should consider trying? If we have to start over and learn a new environment, I will never make deadline. JoeBob

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• Zend_Form using subforms getValues() problem

  - by wiseguydigital

  Hi all, I am building a form in Zend Framework 1.9 using subforms as well as Zend_JQuery being enabled on those forms. The form itself is fine and all the error checking etc is working as normal. But the issue I am having is that when I'm trying to retrieve the values in my controller, I'm receiving just the form entry for the last subform e.g. My master form class (abbreviated for speed): Master_Form extends Zend_Form { public function init() { ZendX_JQuery::enableForm($this); $this->setAction('actioninhere') ... ->setAttrib('id', 'mainForm') $sub_one = new Form_One(); $sub_one->setDecorators(... in here I add the jQuery as per the docs); $this->addSubForm($sub_one, 'form-one'); $sub_two = new Form_Two(); $sub_two->setDecorators(... in here I add the jQuery as per the docs); $this->addSubForm($sub_two, 'form-two'); } } So that all works as it should in the display and when I submit without filling in the required values, the correct errors are returned. However, in my controller I have this: class My_Controller extends Zend_Controller_Action { public function createAction() { $request = $this->getRequest(); $form = new Master_Form(); if ($request->isPost()) { if ($form->isValid($request->getPost()) { // This is where I am having the problems print_r($form->getValues()); } } } } When I submit this and it gets past isValid(), the $form-getValues() is only returning the elements from the second subform, not the entire form.

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• MSBuild file for deployment process

  - by Lee Englestone

  I could do with some pointers, code examples or references that may help me do the following in an msbuild file to help speed up the deployment process.. This scenario involves getting a developers 'local' version onto a 'development' server.. Increment a developers local Web Applications Assembly version number Publish a developers local Web Application files somewhere .rar the publsihed files or folder into the format v[IncrementedAssemblyNumber].rar Copy the .rar to somewhere Backup (.rar) the existing live website folder (located elsewhere) in the format Pre_v[IncrementedAssemblyNumber].rar Move the backed up .rar to a /Backup folder. Overwrite the development web files with the published local web files Should be simple for all those MSBUILD Gurus out there. Like I said, answers or 'Good and applicable' links would be much appreciated. Also i'm thinking of getting one of the MSbuild books. From what I can tell there are 2, possibly 3 contenders. I am not using TFS. Can anyone recommend a book for beginning MSBUILD? Ideally from people that have read more than one book on the subject. Cheers, -- Lee

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• Scheme: what are the benefits of letrec?

  - by Ixmatus

  While reading "The Seasoned Schemer" I've begun to learn about letrec. I understand what it does (can be duplicated with a Y-Combinator) but the book is using it in lieu of recurring on the already defined function operating on arguments that remain static. An example of an old function using the defined function recurring on itself (nothing special): (define (substitute new old lat) (cond ((null? l) '()) ((eq? (car l) old) (cons new (substitute new old (cdr l)))) (else (cons (car l) (substitute new old (cdr l)))))) Now for an example of that same function but using letrec: (define (substitute new old lat) (letrec ((replace (lambda (l) (cond ((null? l) '()) ((eq? (car l) old) (cons new (replace (cdr l)))) (else (cons (car l) (replace (cdr l)))))))) (replace lat))) Aside from being slightly longer and more difficult to read I don't know why they are rewriting functions in the book to use letrec. Is there a speed enhancement when recurring over a static variable this way because you don't keep passing it?? Is this standard practice for functions with arguments that remain static but one argument that is reduced (such as recurring down the elements of a list)? Some input from more experienced Schemers/LISPers would help!

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• Hiring my first employee

  - by Ady

  A few years ago I moved to a new job having been programming for 2 years using C#, however this new company was mainly using VB6. I made the case for .NET and won, but one of the consessions I had to make was to use VB.NET and not C# (understandable as most of the other developers were already using VB). Three years later it was time to move on, but when applying for jobs I couldn't get past the recruitment agents. I realised that when they were looking at the basic requirements (5 years experience) that they could not add 2 and 3 together to make 5. They were looking for 5 years in VB or C# not across both. Frustrated I decided to combine my skills with a designer friend and start my own company. After two years of hard graft we are now looking for our first employee (a programmer), and this question has hit me again, but now I see the employers perspective. Why take the risk of someone getting up to speed when you have thousands of applicants to choose from. So my question is this, if I define the requirements to be too narrow, I could miss the really great candidates. But if they are too broad it's going to take ages to go through them all. This will be our first 'employee' so the choice needs to be good, I can't afford to make a mistake and employ someone naff. Another option would be to choose a bright university graduate, and train them up (less of a risk because we can pay them less). What have others done in this situation, and what would you recommend I do?

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• GWT: Populating a page from datastore using RPC is too slow

  - by Ilya Boyandin

  Is there a way to speed up the population of a page with GWT's UI elements which are generated from data loaded from the datastore? Can I avoid making the unnecessary RPC call when the page is loaded? More details about the problem I am experiencing: There is a page on which I generate a table with names and buttons for a list of entities loaded from the datastore. There is an EntryPoint for the page and in its onModuleLoad() I do something like this: final FlexTable table = new FlexTable(); rpcAsyncService.getAllCandidates(new AsyncCallback<List<Candidate>>() { public void onSuccess(List<Candidate> candidates) { int row = 0; for (Candidate person : candidates) { table.setText(row, 0, person.getName()); table.setWidget(row, 1, new ToggleButton("Yes")); table.setWidget(row, 2, new ToggleButton("No")); row++; } } ... }); This works, but takes more than 30 seconds to load the page with buttons for 300 candidates. This is unacceptable. The app is running on Google App Engine and using the app engine's datastore.

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• oracle query with inconsistent results

  - by Spencer Stejskal

  Im having a very strange problem, i have a complicated view that returns incorrect data when i query on a particular column. heres an example: select empname, has_garnishment from timecard_v2 where empname = 'Testerson, Testy'; this returns the single result 'Testerson, Testy', 'N' however, if i use the query: select empname, has_garnishment from timecard_v2 where empname = 'Testerson, Testy' and has_garnishment = 'Y'; this returns the single result 'Testerson, Testy', 'Y' The second query should return a subset of the first query, but it returns a different answer. I have dissected the view and determined that this section of the view definition is where the problem arises(Note, I removed all of the select clause except the parts of interests for clarity, in the full query all joined tables are required): SELECT e.fullname empname , NVL2(ded.has_garn, 'Y', 'N') has_garnishment FROM timecard tc , orderdetail od , orderassign oa , employee e , employee3 e3 , customer10 c10 , order_misc om, (SELECT COUNT(*) has_garn, v_ssn FROM deductions WHERE yymmdd_stop = 0 OR (LENGTH(yymmdd_stop) = 7 AND to_date(SUBSTR(yymmdd_stop, 2), 'YYMMDD') sysdate) GROUP BY v_ssn ) ded WHERE oa.lrn(+) = tc.lrn_order AND om.lrn(+) = od.lrn AND od.orderno = oa.orderno AND e.ssn = tc.ssn AND c10.custno = tc.custno AND e.lrn = e3.lrn AND e.ssn = ded.v_ssn(+) One thing of note about the definition of the 'ded' subquery. The v_ssn field is a virtual field on the deductions table. I am not a DBA im a software developer but we recently lost our DBA and the new one is still getting up to speed so im trying to debug this issue. That being said, please explain things a little more thoroughly then you would for a fellow oracle expert. thanks

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• What do you use to play sound in iPhone games?

  - by zoul

  Hello! I have a performance-intensive iPhone game I would like to add sounds to. There seem to be about three main choices: (1) AVAudioPlayer, (2) Audio Queues and (3) OpenAL. I’d hate to write pages of low-level code just to play a sample, so that I would like to use AVAudioPlayer. The problem is that it seems to kill the performace – I’ve done a simple measuring using CFAbsoluteTimeGetCurrent and the play message seems to take somewhere from 9 to 30 ms to finish. That’s quite miserable, considering that 25 ms == 40 fps. Of course there is the prepareToPlay method that should speed things up. That’s why I wrote a simple class that keeps several AVAudioPlayers at its disposal, prepares them beforehand and then plays the sample using the prepared player. No cigar, still it takes the ~20 ms I mentioned above. Such performance is unusable for games, so what do you use to play sounds with a decent performance on iPhone? Am I doing something wrong with the AVAudioPlayer? Do you play sounds with Audio Queues? (I’ve written something akin to AVAudioPlayer before 2.2 came out and I would love to spare that experience.) Do you use OpenAL? If yes, is there a simple way to play sounds with OpenAL, or do you have to write pages of code? Update: Yes, playing sounds with OpenAL is fairly simple.

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• General Address Parser for Freeform Text

  - by Daemonic

  We have a program that displays map data (think Google Maps, but with much more interactivity and custom layers for our clients). We allow navigation via a set of combo boxes that prefill certain fields with a bunch of data (ie: Country: Canada, the Province field is filled in. Select Ontario, and a list of Counties/Regions is filled in. Select a county/region, and a city is filled in, etc...). While this guarantees accurate addresses, it's a pain for the users if they don't know where a street address or a city are located (ie, which county/region is kitchener in?). So we are looking at trying to do an address parser with a freeform text field. The user could enter something like this (similar to Google Maps, Bing Maps, etc...): 22 Main St, Kitchener, On And we could compartmentalize it into sections and do lookups on the data and get to the point they are looking for (or suggest alternatives). The problem with this is that how do we properly compartmentalize information? How do we break up the sections and find possible matches? I'm guessing we wouldn't be guaranteed that the user would enter data in a format we always expected (obviously). A follow up to this would be how to present the data if we don't find an exact match (or find multiple exact matches... two cities with the same street name in different counties, for example). We have a ton of data available in the mapping data (mapinfo tab format mostly). So we can do quick scans of street names, cities, states, etc. But I'm not sure about the best way to go about approaching this problem. Sure, using Google Maps would be nice, bue most of our clients are in closed in networks where outside access is not usually allowed and most aren't willing to rely on google maps (since it doesn't contain as much information as they need, such as custom map layers). They could, obviously, go to google and get the proper location then move to our software, but this would time consuming and speed of the process can be quite important.

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• Switching to WPF, the best use of time at Visual Studio Launch 2010

  - by Stewbob

  Yes, this is a programming-related question, if a little indirectly (that's why I marked it Community Wiki right away). For better or worse, I am switching from Winforms to WPF in April. I am also going to be in attendance at the Visual Studio Launch in Las Vegas. I have a real need to get up to speed quickly in WPF, so my question is: What sessions are going to be the best use of my time? I've got some picked out already, but I'm looking for some more advice on how to wade through all the marketing fluff and get some real educational value out of these few days. I have not been to one of these events before, so I don't really know how much is marketing hype, and how much is solid content. A couple of the workshops look interesting (VPR02 and VPS02), but I don't know enough about the actual content of these to justify the extra expense right now. Any thoughts there would be appreciated. And yes, I do have WPF learning planned other than just these few days in Vegas, but since I'm going to be there anyway, I want to learn as much as I can in the time available.

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• Poor DB4O performance - What am I doing wrong?

  - by Jon

  I read Rob Conery's post about Object databases and thought I'd give it a go. I have a class lets say Book with 15 properties mostly string, some int, one Datetime and 2 decimals. I used Rob's code to open the database file etc to test on a Winforms project not a Web project. So I did the following: for(int i = 0; i < 1000000; i++) { var Book = new Book(); //Assign variables s.Save(Book); } s.CommitChanges(); This took at least a couple of minutes. I then tried to retrieve all data to test speed: var spp = s.All<Passports>(); This one line was quick, however, then doing: sppp.Count() as well as a seperate test doing a foreach loop and incrementing a counter took a couple of minutes. This seems quite slow to me. Am I doing something wrong or am I expecting too much?

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• I need a fast runtime expression parser

  - by Chris Lively

  I need to locate a fast, lightweight expression parser. Ideally I want to pass it a list of name/value pairs (e.g. variables) and a string containing the expression to evaluate. All I need back from it is a true/false value. The types of expressions should be along the lines of: varA == "xyz" and varB==123 Basically, just a simple logic engine whose expression is provided at runtime. UPDATE At minimum it needs to support ==, !=, , =, <, <= Regarding speed, I expect roughly 5 expressions to be executed per request. We'll see somewhere in the vicinity of 100/requests a second. Our current pages tend to execute in under 50ms. Usually there will only be 2 or 3 variables involved in any expression. However, I'll need to load approximately 30 into the parser prior to execution. UPDATE 2012/11/5 Update about performance. We implemented nCalc nearly 2 years ago. Since then we've expanded it's use such that we average 40+ expressions covering 300+ variables on post backs. There are now thousands of post backs occurring per second with absolutely zero performance degradation. We've also extended it to include a handful of additional functions, again with no performance loss. In short, nCalc met all of our needs and exceeded our expectations.

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• How do I use IPTC/EXIF metadata to categorise photos?

  - by kbro

  Many photo viewing and editing applications allow you to examine and change EXIF and IPTC data in JPEG and other image files. For example, I can see things like shutter speed, aperture and orientation in the picture files that come off my Canon A430. There are many, many name/value pairs in all this metadata. But... What do I do if I want to store some data that doesn't have a build-in field name. Let's say I'm photographing an athletics competition and I want to tag every photo with the competitor's bib number. Can I create a "bib_number" field and assign it a values of "0001", "5478", "8124" etc, and then search for all photos with bib_number="5478"? I've spent a few hours searching and the best I can come up with is to put this custom information in the "keywords" field but this isn't quite what I'm after. With this socution I'd have to craft a query like "keywords contains bib_number_5478" whereas what I want it "bib_number is 5478". So do the EXIF and/or IPTC standards allow addtional user-defined field names? Thanks Kev

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