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  • Not crawling the same content twice

    - by sirrocco
    I'm building a small application that will crawl sites where the content is growing (like on stackoverflow) the difference is that the content once created is rarely modified. Now , in the first pass I crawl all the pages in the site. But next, the paged content of that site - I don't want to re-crawl all of it , just the latest additions. So if the site has 500 pages, on the second pass if the site has 501 pages then I would only crawl the first and second pages. Would this be a good way to handle the situation ? In the end, the crawled content will end up in lucene - creating a custom search engine. So, I would like to avoid crawling multiple times the same content. Any better ideas ? EDIT : Let's say the site has a page : Results that will be accessed like so : Results?page=1 , Results?page=2 ...etc I guess that keeping a track of how many pages there were at the last crawl and just crawl the difference would be enough. ( maybe using a hash of each result on the page - if I start running into the same hashes - I should stop)

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  • How to speed-up a simple method? (possibily without changing interfaces or data structures)

    - by baol
    Hello. I have some data structures: all_unordered_mordered_m is a big vector containing all the strings I need (all different) ordered_m is a small vector containing the indexes of a subset of the strings (all different) in the former vector position_m maps the indexes of objects from the first vector to their position in the second one. The string_after(index, reverse) method returns the string referenced by ordered_m after all_unordered_m[index]. ordered_m is considered circular, and is explored in natural or reverse order depending on the second parameter. The code is something like the following: struct ordered_subset { // [...] std::vector<std::string>& all_unordered_m; // size = n >> 1 std::vector<size_t> ordered_m; // size << n std::map<size_t, size_t> position_m; // positions of strings in ordered_m const std::string& string_after(size_t index, bool reverse) const { size_t pos = position_m.find(index)->second; if(reverse) pos = (pos == 0 ? orderd_m.size() - 1 : pos - 1); else pos = (pos == ordered.size() - 1 ? 0 : pos + 1); return all_unordered_m[ordered_m[pos]]; } }; Given that: I do need all of the data-structures for other purposes; I cannot change them because I need to access the strings: by their id in the all_unordered_m; by their index inside the various ordered_m; I need to know the position of a string (identified by it's position in the first vector) inside ordered_m vector; I cannot change the string_after interface without changing most of the program. How can I speed up the string_after method that is called billions of times and is eating up about 10% of the execution time?

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  • Overriding CSS properties for iframe width

    - by user2898989
    I'm trying to put an iframe into a webpage, but no matter what I try to put in either the iframe properties or the custom CSS section of the website builder (or how many times I try to add !important to anything from width to right-margin), I can't get the iframe to extend rightward further than the page's preset width. Here's an example of the page and iframe that I'm working with: http://fmlcapitalinvestment.com/Search_Properties.html I need that script/iframe to be wide enough to show the search area. It seems pointless to copy and paste code and attributes I've tried setting, because nothing I do seems to have any effect, but just for showing how much I have no idea what I'm doing, here's my iframe code: <iframe id="idxFrame" style="padding:0; margin:0; padding-top: 0px; overflow-x:auto; width:1000px!important; border:0px solid transparent; background-color:transparent; max-width:none!important; right-margin:-200px!important" frameborder="0" scrolling="on" src="http://www.themls.com/IDXNET/Default.aspx?wid=8MSsp7Pf9eI55yjkDuB%2blX5awn7LnnVXh5PNYhq2ImAEQL" width="1200px" height="900px"></iframe> The "Website Builder" that I'm forced to use to make these kinds of pages is infuriating, but it does have a "Custom CSS" area where I can input additional CSS information. Is there something I could generically use to set iframes to their own widths?

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  • MonoTouch's Soft Debugger don't connect to App on iPhone - why?

    - by smokinharp
    Hi everyone, I'm quite new on MonoTouch, so please forgive me my question in doubt... ;-) I need help with the soft-debugger, because it's not connecting to the App on the device. While with iPhone Simulator everything is working as expected, the following happens when I start debugging against my device: The is uploaded and installed to the device. MonoDevelop comes up with a window saying the following: "Waiting for debugger to connect on 127.0.0.1:10000..." Please start the application on the device" When starting the app on the device, the device vibrates indicating that the debugger is not connected.... In the settings of my App on the iPhone I have set the IP-Adress to my Mac's IP. My iPhone is connected via WIFI to my network. I can ping my Mac from my iPhone and vice versa. In several screenshots where the debugger was obviously working I saw that the debugger came up with the Mac's IP address and not the 127.0.0.1.... Do I have to configure my IP-address somewhere in MonoDevelop? BTW: I'm using the latest version of MonoDevelop - it's 2.4.1 I have tried anything.... re-installing MonoDevelop, cleaning up the project several times, setting up a new project.... nothing... Please, please help....

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  • C# Dictionary Loop Enhancment

    - by Toto
    Hi, I have a dictionary with around 1 milions items. I am constantly looping throw the dictionnary : public void DoAllJobs() { foreach (KeyValuePair<uint, BusinessObject> p in _dictionnary) { if(p.Value.MustDoJob) p.Value.DoJob(); } } The execution is a bit long, around 600 ms, I would like to deacrese it. Here is the contraints : MustDoJob values mostly stay the same beetween two calls to DoAllJobs() 60-70% of the MustDoJob values == false From time to times MustDoJob change for 200 000 pairs. Some p.Value.DoJob() can not be computed at the same time (COM object call) Here, I do not need the key part of the _dictionnary objet but I really do need it somewhere else I wanted to do the following : Parallelizes but I am not sure is going to be effective due to 4. Sorts the dictionnary since 1. and 2. (and stop want I find the first MustDoJob == false) but I am wondering what 3. would result in I did not implement any of the previous ideas since it could be a lot of job and I would like to investigate others options before. So...any ideas ?

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  • Ordering by number of rows?

    - by Rob
    Alright, so I have a table outputting data from a MySQL table in a while loop. Well one of the columns it outputs isn't stored statically in the table, instead it's the sum of how many times it appears in a different MySQL table. Sorry I'm not sure this is easy to understand. Here's my code: $query="SELECT * FROM list WHERE added='$addedby' ORDER BY time DESC"; $result=mysql_query($query); while($row=mysql_fetch_array($result, MYSQL_ASSOC)){ $loghwid = $row['hwid']; $sql="SELECT * FROM logs WHERE hwid='$loghwid' AND time < now() + interval 1 hour"; $query = mysql_query($sql) OR DIE(mysql_error()); $boots = mysql_num_rows($query); //Display the table } The above is the code displaying the table. As you can see it's grabbing data from two different MySQL tables. However I want to be able to ORDER BY $boots DESC. But as its a counting of a completely different table, I have no idea of how to go about doing that. I would appreciate any help, thank you.

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  • Pass command line arguments to JUnit test case being run programmatically

    - by __nv__
    I am attempting to run a JUnit Test from a Java Class with: JUnitCore core = new JUnitCore(); core.addListener(new RunListener()); core.run(classToRun); Problem is my JUnit test requires a database connection that is currently hardcoded in the JUnit test itself. What I am looking for is a way to run the JUnit test programmatically(above) but pass a database connection to it that I create in my Java Class that runs the test, and not hardcoded within the JUnit class. Basically something like JUnitCore core = new JUnitCore(); core.addListener(new RunListener()); core.addParameters(java.sql.Connection); core.run(classToRun); Then within the classToRun: @Test Public void Test1(Connection dbConnection){ Statement st = dbConnection.createStatement(); ResultSet rs = st.executeQuery("select total from dual"); rs.next(); String myTotal = rs.getString("TOTAL"); //btw my tests are selenium testcases:) selenium.isTextPresent(myTotal); } I know about The @Parameters, but it doesn't seem applicable here as it is more for running the same test case multiple times with differing values. I want all of my test cases to share a database connection that I pass in through a configuration file to my java client that then runs those test cases (also passed in through the configuration file). Is this possible? P.S. I understand this seems like an odd way of doing things.

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  • How can we find second maximum from array efficiently?

    - by Xinus
    Is it possible to find the second maximum number from an array of integers by traversing the array only once? As an example, I have a array of five integers from which I want to find second maximum number. Here is an attempt I gave in the interview: #define MIN -1 int main() { int max=MIN,second_max=MIN; int arr[6]={0,1,2,3,4,5}; for(int i=0;i<5;i++){ cout<<"::"<<arr[i]; } for(int i=0;i<5;i++){ if(arr[i]>max){ second_max=max; max=arr[i]; } } cout<<endl<<"Second Max:"<<second_max; int i; cin>>i; return 0; } The interviewer, however, came up with the test case int arr[6]={5,4,3,2,1,0};, which prevents it from going to the if condition the second time. I said to the interviewer that the only way would be to parse the array two times (two for loops). Does anybody have a better solution?

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  • Corrupt output with an HttpModule

    - by clementi
    I have an HttpModule that looks at the query string for a parameter called "cmd" and executes one of a small set of predefined commands that display server stats in XML. For example, http://server01?cmd=globalstats. Now, on rare occasions, like once out of hundreds of times, I will get corrupt output like this: <!-- the stats start displaying fine... --> <stats> <ServerName>SERVER01</ServerName> <StackName>Search</StackName> <TotalRequests>945</TotalRequests> <!-- ...until something has gone awry and now we're getting the markup of the home page! --> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> ...the rest of the home page markup... (Remove the comments in the example above.) I'm not all that familiar with HttpModules and the IIS pipeline, but could this be a threading problem? Or, what else?

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  • Creating a Variable From Two Others

    - by John
    Hello, In the HTML table below, I would like to add a third column that equals $row["countSubmissions"] times 10 plus $row["countComments"]. How could I do this? Thanks in advance, John $sqlStr = "SELECT l.loginid, l.username, COALESCE(s.total, 0) AS countSubmissions, COALESCE(c.total, 0) AS countComments FROM login l LEFT JOIN ( SELECT loginid, COUNT(1) AS total FROM submission GROUP BY loginid ) s ON l.loginid = s.loginid LEFT JOIN ( SELECT loginid, COUNT(1) AS total FROM comment GROUP BY loginid ) c ON l.loginid = c.loginid GROUP BY l.loginid ORDER BY countSubmissions DESC LIMIT 10"; $result = mysql_query($sqlStr); $arr = array(); echo "<table class=\"samplesrec1edit\">"; while ($row = mysql_fetch_array($result)) { echo '<tr>'; echo '<td class="sitename1edit1"><a href="http://www...com/.../members/index.php?profile='.$row["username"].'">'.stripslashes($row["username"]).'</a></td>'; echo '<td class="sitename1edit2">'.stripslashes($row["countSubmissions"]).'</td>'; echo '<td class="sitename1edit2">'.stripslashes($row["countComments"]).'</td>'; echo '</tr>'; } echo "</table>";

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  • loop prematurely quitting

    - by Nick Gibson
    This loop works fine but prematurely quits at times. I set a piece of code in it so that I can view the random number. It only closes prematurely when the random number is equal to the highest numbered question the user inputs (Example...a user wants 10 questions, if the random number is 10 the program quits.) I have no idea why since i have it set to if(random number <= the number of questions) for ( int loop = 1; loop < loopCount; loop++ ) { aa = r.nextInt ( 10 + 1 ); abc = ( int ) aa; String[] userAnswer = new String[x]; JOptionPane.showMessageDialog ( null, abc ); if ( abc <= x ) { for ( overValue = 1; overValue < forLoop; overValue++ ); { userAnswer[j] = JOptionPane.showInputDialog ( null, "Question " + quesNum + "\n" + questions[abc] + "\n\nA: " + a[abc] + "\nB: " + b[abc] + "\nC: " + c[abc] + "\nD: " + d[abc] ); if ( userAnswer[j].equals ( answers[j] ) ) { JOptionPane.showMessageDialog ( null, "Correct. \nThe Correct Answer is " + answers[abc] ); } else { JOptionPane.showMessageDialog ( null, "Wrong. \n The Correct Answer is " + answers[abc] ); }//else }//for }//if }//for

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  • Why doesn't Win Forms application update label immediately?

    - by rosscj2533
    I am doing some experimenting with threads, and made a 'control' method to compare against where all the processing happens in the UI thread. It should run a method, which will update a label at the end. This method runs four times, but the labels are not updated until all 4 have completed. I expected one label to get updated about every 2 seconds. Here's the code: private void button1_Click(object sender, EventArgs e) { Stopwatch watch = new Stopwatch(); watch.Start(); UIThreadMethod(lblOne); UIThreadMethod(lblTwo); UIThreadMethod(lblThree); UIThreadMethod(lblFour); watch.Stop(); lblTotal.Text = "Total Time (ms): " + watch.ElapsedMilliseconds.ToString(); } private void UIThreadMethod(Label label) { Stopwatch watch = new Stopwatch(); watch.Start(); for (int i = 0; i < 10; i++) { Thread.Sleep(200); } watch.Stop(); // this doesn't set text right away label.Text = "Done, Time taken (ms): " + watch.ElapsedMilliseconds; } Maybe I'm just missing something basic, but I'm stuck. Any ideas? Thanks.

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  • iPhone producing strange results on 'if' statement

    - by Rob
    I have a UIPicker where the user inputs a specified time (i.e. 13:00, 13:01, 13:02, etc.) - which determines their score. Once they hit the button an alert comes up with the score that is determined through this 'if-else' statement. Everything seems to work great MOST of the time - but I am getting some erratic behavior. This is the code: //Gets my value from the UIPicker and then converts it into a format that can be used in the 'if' statement. NSInteger runRow = [runTimePicker selectedRowInComponent:2]; NSString *runSelected = [runTimePickerData objectAtIndex:runRow]; NSString *runSelectedFixed = [runSelected stringByReplacingOccurrencesOfString:@":" withString:@"."]; //The actual 'if' statment. if ([runSelectedFixed floatValue] <= 13.00) { runScore = 100; } else if ([runSelectedFixed floatValue] <= 13.06) { runScore = 99; } else if ([runSelectedFixed floatValue] <= 13.12) { runScore = 97; } else if ([runSelectedFixed floatValue] <= 13.18) { runScore = 96; } else if ([runSelectedFixed floatValue] <= 13.24) { runScore = 94; } else if ([runSelectedFixed floatValue] <= 13.30) { runScore = 93; } else if ([runSelectedFixed floatValue] <= 13.36) { runScore = 92; } else if ([runSelectedFixed floatValue] <= 13.42) { runScore = 90; } else if ([runSelectedFixed floatValue] <= 13.48) { runScore = 89; } else if ([runSelectedFixed floatValue] <= 13.54) { runScore = 88; } Now, when I test the program, I will get the expected result when I choose '13:00' which is '100'. I also get the expected result of '99' when I choose all of the times between '13:01 and 13:05'. BUT, when I choose '13:06' it gives me a score of '97'. I also get a score of '97' on '13:07 through 13:12' - which is the desired result. Why would I get a '97' right on '13:12' but not get a '99' right on '13:06'???? Could this be a memory leak or something???

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  • Graph search problem with route restrictions

    - by Darcara
    I want to calculate the most profitable route and I think this is a type of traveling salesman problem. I have a set of nodes that I can visit and a function to calculate cost for traveling between nodes and points for reaching the nodes. The goal is to reach a fixed known score while minimizing the cost. This cost and rewards are not fixed and depend on the nodes visited before. The starting node is fixed. There are some restrictions on how nodes can be visited. Some simplified examples include: Node B can only be visited after A After node C has been visited, D or E can be visited. Visiting at least one is required, visiting both is permissible. Z can only be visited after at least 5 other nodes have been visited Once 50 nodes have been visited, the nodes A-M will no longer reward points Certain nodes can (and probably must) be visited multiple times Currently I can think of only two ways to solve this: a) Genetic Algorithms, with the fitness function calculating the cost/benefit of the generated route b) Dijkstra search through the graph, since the starting node is fixed, although the large number of nodes will probably make that not feasible memory wise. Are there any other ways to determine the best route through the graph? It doesn't need to be perfect, an approximated path is perfectly fine, as long as it's error acceptable. Would TSP-solvers be an option here?

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  • MySQL datetime fields and daylight savings time -- how do I reference the "extra" hour?

    - by Aaron
    I'm using the America/New York timezone. In the Fall we "fall back" an hour -- effectively "gaining" one hour at 2am. At the transition point the following happens: it's 01:59:00 -04:00 then 1 minute later it becomes: 01:00:00 -05:00 So if you simply say "1:30am" it's ambiguous as to whether or not you're referring to the first time 1:30 rolls around or the second. I'm trying to save scheduling data to a MySQL database and can't determine how to save the times properly. Here's the problem: "2009-11-01 00:30:00" is stored internally as 2009-11-01 00:30:00 -04:00 "2009-11-01 01:30:00" is stored internally as 2009-11-01 01:30:00 -05:00 This is fine and fairly expected. But how do I save anything to 01:30:00 -04:00? The documentation does not show any support for specifying the offset and, accordingly, when I've tried specifying the offset it's been duly ignored. The only solutions I've thought of involve setting the server to a timezone that doesn't use daylight savings time and doing the necessary transformations in my scripts (I'm using PHP for this). But that doesn't seem like it should be necessary. Many thanks for any suggestions.

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  • How can I dynamically define the named route in a :partial in rails?

    - by Angela
    I have the following partial. It can be called from three different times in a view as follows: <%= render :partial => "contact_event", :collection => @contacts, :locals => {:event => email} %> Second time: <%= render :partial => "contact_event", :collection => @contacts, :locals => {:event => call} %> Third time: <%= render :partial => "contact_event", :collection => @contacts, :locals => {:event => letter} %> In each instance, call, email, letter refer to a specific instance of a Model Call, Email, or Letter. Here is the content of the partial "contact_event": <%= link_to_remote "Skip #{event} Remote", :url => skip_contact_email_url(contact_event, event), :update => "update-area-#{contact_event.id}-#{event.id}" %> <span id='update-area-<%="#{contact_event.id}-#{event.id}"%>'> </span> </p> My challenge: skip_contact_email_url only works when the event refers to an email. How can I dynamically define skip_contact_email_url to be skip_contact_letter_url if the local variable is letter? Even better, how can I have a single named route that would do the appropriate action?

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  • How can I dynamically call the named route in a :partial in rails?

    - by Angela
    I have the following partial. It can be called from three different times in a view as follows: <%= render :partial => "contact_event", :collection => @contacts, :locals => {:event => email} %> Second time: <%= render :partial => "contact_event", :collection => @contacts, :locals => {:event => call} %> Third time: <%= render :partial => "contact_event", :collection => @contacts, :locals => {:event => letter} %> In each instance, call, email, letter refer to a specific instance of a Model Call, Email, or Letter. Here is what I tried to do and conceptually what I'd like to do: assign the route based on the class name that has been passed to the :event from the :partial. What I did was create what the actual url should be. The 'text' of it is correct, but doesn't seem to recognize it as a named route. <% url = "skip_contact_#{event.class.name.tableize.singularize}_url" % <%= link_to_remote "Skip #{url} Remote", :url = skip_contact_email_url(contact_event, event), :update = "update-area-#{contact_event.id}-#{event.id}" % ' My challenge: skip_contact_email_url only works when the event refers to an email. How can I dynamically define skip_contact_email_url to be skip_contact_letter_url if the local variable is letter? Even better, how can I have a single named route that would do the appropriate action?

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  • For each loop not reading in the last item

    - by Gandalf StormCrow
    I'm trying to read in a multi line string then split it then print it .. here is the string : 1T1b5T!1T2b1T1b2T!1T1b1T2b2T!1T3b1T1b1T!3T3b1T!1T3b1T1b1T!5T1*1T 11X21b1X 4X1b1X When I split the string with ! I get this without the last line string : 1T1b5T 1T1b5T1T2b1T1b2T 1T2b1T1b2T1T1b1T2b2T 1T1b1T2b2T1T3b1T1b1T 1T3b1T1b1T3T3b1T 3T3b1T1T3b1T1b1T 1T3b1T1b1T5T1*1T 5T1*1T11X21b1X 11X21b1X Here is my code : import java.io.BufferedInputStream; import java.util.Scanner; public class Main { public static void main(String args[]) { Scanner stdin = new Scanner(new BufferedInputStream(System.in)); while (stdin.hasNext()) { for (String line : stdin.next().split("!")) { System.out.println(line); for (int i = 0; i < line.length(); i++) { System.out.print(line.charAt(i)); } } } } } Where did I make the mistake, why is not reading in the last line? After I read in all lines properly I should go trough each line if I encounter number I should print the next char the n times the number I just read, but that is long way ahead first I need help with this. Thank you

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  • Create an Oracle function that returns a table

    - by Craig
    I'm trying to create a function in package that returns a table. I hope to call the function once in the package, but be able to re-use its data mulitple times. While I know I create temp tables in Oracle, I was hoping to keep things DRY. So far, this is what I have: Header: CREATE OR REPLACE PACKAGE TEST AS TYPE MEASURE_RECORD IS RECORD ( L4_ID VARCHAR2(50), L6_ID VARCHAR2(50), L8_ID VARCHAR2(50), YEAR NUMBER, PERIOD NUMBER, VALUE NUMBER ); TYPE MEASURE_TABLE IS TABLE OF MEASURE_RECORD; FUNCTION GET_UPS( TIMESPAN_IN IN VARCHAR2 DEFAULT 'MONTLHY', STARTING_DATE_IN DATE, ENDING_DATE_IN DATE ) RETURN MEASURE_TABLE; END TEST; Body: CREATE OR REPLACE PACKAGE BODY TEST AS FUNCTION GET_UPS ( TIMESPAN_IN IN VARCHAR2 DEFAULT 'MONTLHY', STARTING_DATE_IN DATE, ENDING_DATE_IN DATE ) RETURN MEASURE_TABLE IS T MEASURE_TABLE; BEGIN SELECT ... INTO T FROM ... ; RETURN T; END GET_UPS; END TEST; The header compiles, the body does not. One error message is 'not enough values', which probably means that I should be selecting into the MEASURE_RECORD, rather than the MEASURE_TABLE. What am I missing?

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  • Multiple/Sub quries with codeigniter

    - by user1011713
    I just started with Codeigniter and this is driving me nuts. I have a query that determines whether a user has bought any programs. I then have to use that program's type category to run and determine how many times he or she has recorded a query in another table. Sorry for the confusion but the code hopefully makes sense. I'm having problem returning the two arrays from my Model to my Controller to onto the view obviously. function specificPrograms() { $specific_sql = $this->db->query("SELECT program,created FROM `assessment` WHERE uid = $this->uid"); if($specific_sql->num_rows() > 0) { foreach ($specific_sql->result() as $specific) { $data[] = $specific; $this->type = $specific->program; } return $data; } $sub_sql = $this->db->query("SELECT id FROM othertable WHERE user_id_fk = $this->uid and type = '$this->type'"); if($sub_sql->num_rows() > 0) { foreach ($sub_sql->result() as $otherp) { $data[] = $otherp; } return $data; } } Then in my Controller I have, $data['specific'] = $this->user_model->specificPrograms(); $data['otherp'] = $this->user_model->specificPrograms(); Thanks for any help.

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  • interface abstract in php real world scenario

    - by jason
    The goal is to learn whether to use abstract or interface or both... I'm designing a program which allows a user to de-duplicate all images but in the process rather then I just build classes I'd like to build a set of libraries that will allow me to re-use the code for other possible future purposes. In doing so I would like to learn interface vs abstract and was hoping someone could give me input into using either. Here is what the current program will do: recursive scan directory for all files determine file type is image type compare md5 checksum against all other files found and only keep the ones which are not duplicates Store total duplicates found at the end and display size taken up Copy files that are not duplicates into folder by date example Year, Month folder with filename is file creation date. While I could just create a bunch of classes I'd like to start learning more on interfaces and abstraction in php. So if I take the scan directory class as the first example I have several methods... ScanForFiles($path) FindMD5Checksum() FindAllImageTypes() getFileList() The scanForFiles could be public to allow anyone to access it and it stores in an object the entire directory list of files found and many details about them. example extension, size, filename, path, etc... The FindMD5Checksum runs against the fileList object created from scanForFiles and adds the md5 if needed. The FindAllImageTypes runs against the fileList object as well and adds if they are image types. The findmd5checksum and findallimagetypes are optionally run methods because the user might not intend to run these all the time or at all. The getFileList returns the fileList object itself. While I have a working copy I've revamped it a few times trying to figure out whether I need to go with an interface or abstract or both. I'd like to know how an expert OO developer would design it and why?

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  • Overhead of calling tiny functions from a tight inner loop? [C++]

    - by John
    Say you see a loop like this one: for(int i=0; i<thing.getParent().getObjectModel().getElements(SOME_TYPE).count(); ++i) { thing.getData().insert( thing.GetData().Count(), thing.getParent().getObjectModel().getElements(SOME_TYPE)[i].getName() ); } if this was Java I'd probably not think twice. But in performance-critical sections of C++, it makes me want to tinker with it... however I don't know if the compiler is smart enough to make it futile. This is a made up example but all it's doing is inserting strings into a container. Please don't assume any of these are STL types, think in general terms about the following: Is having a messy condition in the for loop going to get evaluated each time, or only once? If those get methods are simply returning references to member variables on the objects, will they be inlined away? Would you expect custom [] operators to get optimized at all? In other words is it worth the time (in performance only, not readability) to convert it to something like: ElementContainer &source = thing.getParent().getObjectModel().getElements(SOME_TYPE); int num = source.count(); Store &destination = thing.getData(); for(int i=0;i<num;++i) { destination.insert(thing.GetData().Count(), source[i].getName(); } Remember, this is a tight loop, called millions of times a second. What I wonder is if all this will shave a couple of cycles per loop or something more substantial? Yes I know the quote about "premature optimisation". And I know that profiling is important. But this is a more general question about modern compilers, Visual Studio in particular.

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  • Batch Inserts And Prepared Query Error

    - by ircmaxell
    Ok, so I need to populate a MS Access database table with results from a MySQL query. That's not hard at all. I've got the program written to where it copies a template .mdb file to a temp name and opens it via odbc. No problem so far. I've noticed that Access does not support batch inserting (VALUES (foo, bar), (second, query), (third query)). So that means I need to execute one query per row (there are potentially hundreds of thousands of rows). Initial performance tests show a rate of around 900 inserts/sec into Access. With our largest data sets, that could mean execution times of minutes (Which isn't the end of the world, but obviously the faster the better). So, I tried testing a prepared statement. But I keep getting an error (Warning: odbc_execute() [function.odbc-execute]: SQL error: [Microsoft][ODBC Microsoft Access Driver]COUNT field incorrect , SQL state 07001 in SQLExecute in D:\....php on line 30). Here's the code I'm using (Line 30 is odbc_execute): $sql = 'INSERT INTO table ([field0], [field1], [field2], [field3], [field4], [field5]) VALUES (?, ?, ?, ?, ?, ?)'; $stmt = odbc_prepare($conn, $sql); for ($i = 200001; $i < 300001; $i++) { $a = array($i, "Field1 $", "Field2 $i", "Field3 $i", "Field4 $i", $i); odbc_execute($stmt, $a); } So my question is two fold. First, is there any idea on why I'm getting that error (I've checked, and the number in the array matches the field list which matches the number of parameter ? markers)? And second, should I even bother with this or just use the straight INSERT statements? Like I said, time isn't critical, but if it's possible, I'd like to get that time as low as possible (Then again, I may be limited by disk throughput, since 900 operations/sec is high already)... Thanks

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  • In sync query calls, one query causing other query to run slower. Why?

    - by Irchi
    Sorry for the long question, but I think this is an interesting situation and I couldn't find any explanations for it: I was involved in optimization of an application that performed a large number of sequential SELECT and INSERT statements on a single dedicated SQL Server database. The process needs to INSERT a large number of records into a table, but for each of them there should be some value mappings, which performed using SELECT statements on another table in the same database. For a specific execution, it took 90 minutes to run. I used a profiler (JProfiler - the application is Java-based) to determine how much time does each part of the application take. It yields that 60% of the time was spent on INSERT method calls, and almost 20% on SELECT calls (the rest distributed in other parts). After some trials, I came to this situation: I commented out the INSERT query that took 60% of the time. I was expecting for the total run time to be around 35 minutes, as I have removed 60% of the 90 minutes. But the whole process took the same 90 minutes (doing only SELECTs and nothing else), but each SELECT took longer this time! Everything was running sync, there were no async calls. And there was only one single thread of execution. SELECT and INSERT queries are very simple, and don't have anything special, and they are on different tables, but on the same DB. I tested with both the DB on the application machine, and on a remote network machine. I can't think of any explanation for this, as the Profiler (Application profiler, not SQL Profiler) reported the changes in the method call times, and by removing INSERT statements SELECT statements took longer to run. Can anyone give me some kind of explanation of what could have happened? (there can't be cache / query optimization stuff, because the queries were run in sync, and in a single thread, and it was far from affecting the cache this much) I should note that the bottleneck of the speed was in SQL server, using most of the CPU time.

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  • Are there concurrency problems when using -performSelector:withObject:afterDelay: ?

    - by mystify
    For example, I often use this: [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:someDelay]; Now, lets say I call this 10 times to perform at the exact same delay, like: [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; - (void)doSomethingAfterDelay:(id)someObject { /* access an array, read stuff, write stuff, do different things that would suffer in multithreaded environments .... all operations are nonatomic! */ } I have observed pretty strange behavior when doing things like this. For my understanding, this method schedules a timer to fire on the current thread, so in this case the main thread. But since it doesn't create new threads, it actually should not be possible to run into concurrency problems, right?

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