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  • Is there a design pattern to cut down on code duplication when subclassing Activities in Android?

    - by Daniel Lew
    I've got a common task that I do with some Activities - downloading data then displaying it. I've got the downloading part down pat; it is, of course, a little tricky due to the possibility of the user changing the orientation or cancelling the Activity before the download is complete, but the code is there. There is enough code handling these cases such that I don't want to have to copy/paste it to each Activity I have, so I thought to create an abstract subclass Activity itself such that it handles a single background download which then launches a method which fills the page with data. This all works. The issue is that, due to single inheritance, I am forced to recreate the exact same class for any other type of Activity - for example, I use Activity, ListActivity and MapActivity. To use the same technique for all three requires three duplicate classes, except each extends a different Activity. Is there a design pattern that can cut down on the code duplication? As it stands, I have saved much duplication already, but it pains me to see the exact same code in three classes just so that they each subclass a different type of Activity.

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  • Using custom Qt subclasses in Python

    - by kwatford
    First off: I'm new to both Qt and SWIG. Currently reading documentation for both of these, but this is a time consuming task, so I'm looking for some spoilers. It's good to know up-front whether something just won't work. I'm attempting to formulate a modular architecture for some in-house software. The core components are in C++ and exposed via SWIG to Python for experimentation and rapid prototyping of new components. Qt seems like it has some classes I could use to avoid re-inventing the wheel too much here, but I'm concerned about how some of the bits will fit together. Specifically, if I create some C++ classes, I'll need to expose them via SWIG. Some of these classes likely subclass Qt classes or otherwise have Qt stuff exposed in their public interfaces. This seems like it could raise some complications. There are already two interfaces for Qt in Python, PyQt and PySide. Will probably use PySide for licensing reasons. About how painful should I expect it to be to get a SWIG-wrapped custom subclass of a Qt class to play nice with either of these? What complications should I know about upfront?

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  • What is the correct approach to using GWT with persistent objects?

    - by dankilman
    Hi, I am currently working on a simple web application through Google App engine using GWT. It should be noted that this is my first attempt at such a task. I have run into to following problem/dilema: I have a simple Class (getters/setters and nothing more. For the sake of clarity I will refer to this Class as DataHolder) and I want to make it persistent. To do so I have used JDO which required me to add some annotations and more specifically add a Key field to be used as the primary key. The problem is that using the Key class requires me to import com.google.appengine.api.datastore.Key which is ok on the server side, but then I can't use DataHolder on the client side, because GWT doesn't allow it (as far as I know). So I have created a sister Class ClientDataHolder which is almost identical, though it doesn't have all the JDO annotations nor the Key field. Now this actually works but It feels like I'm doing something wrong. Using this approach would require maintaining to separate classes for each entity I wish to have. So my question is: Is there a better way of doing this? Thank you.

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  • SQL developer here -- Nesting with select * finicky in Oracle 10g?

    - by John Sullivan
    I am writing a simple diagnostic query I will execute in my Oracle 10g scratchpad. I am trying to do this as part of a step to build the query. In the SQL Scratchpad for Oracle 10g Enterprise Manager Console, this statement runs fine. SELECT * FROM v$session sess, v$sql sql WHERE sql.sql_id(+) = sess.sql_id and sql.sql_text <> ' ' If I try to wrap that up in Select * from () tb2 I get an error, "ORA-00918: Column Ambiguously Defined". I didn't think that could ever happen with this kind of statement so I am a bit confused. select * from (SELECT * FROM v$session sess, v$sql sql WHERE sql.sql_id(+) = sess.sql_id and sql.sql_text <> ' ') tb2 You should always be able to select * from the result set of another select * statement using this structure as far as I'm aware... right? Is Oracle/10g/the scratchpad trying to force me to accept a certain syntactic structure to prevent excessive nesting? Is this a bug in scratchpad or something about how oracle works?

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  • Jquery tooltip absolute position above a link which is inside paragraph text?

    - by BerggreenDK
    I am trying to retrieve the position of an HTML element inside a paragraph. Eg. a span or anchor. I would also like the width of the element. So that when I hover the object, I can activate/build/show a sort of toolbar/tooltip above the element dynamically. I need it to be dynamically added to exisiting content, so somekinda "search-replace" jQuery thingy that scans the elements within eg. a DIV and then does this for all that matches this "feature". Main problem/question is: How do I retrieve the "current absolute" position of the element I am hovering with the mouse. I dont want the toolbar/tooltip to be following the mouse, but instead it must "snap" to the element its hovering. so I was thinking: "place BOX -20px from current element. Match width.... Possible? is there a jQuery plugin for this already - or? Sample code: <div class="helper"> <h1>headline</h1> <p>Here is some sample text. But <a href="somewhere.htm" class="help help45">this is with an explanation you can hover</a>. <a href="somewhereelse.htm">And this isnt.</a> <ul> <li>We could also do it <a href="somewhere.htm" class="help help32">inside a bullet list</a></li> </ul> </div> The .help is the class triggering the "help" and the .help45 or .help32 is the helpsection needed to be shown (but thats another task later, as I am hoping to retreive the "id" from the "help45" so a serverlookup for id=45 can load the text needed to be shown. Nb. if the page scrolls etc. the helptip still needs to follow the item on the page until closed/hidden.

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  • Update table using SSIS

    - by thursdaysgeek
    I am trying to update a field in a table with data from another table, based on a common key. If it were in straight SQL, it would be something like: Update EHSIT set e.IDMSObjID = s.IDMSObjID from EHSIT e, EHSIDMS s where e.SITENUM = s.SITE_CODE However, the two tables are not in the same database, so I'm trying to use SSIS to do the update. Oh, and the sitenum/site_code are varchar in one and nvarchar in the other, so I'll have to do a data conversion so they'll match. How do I do it? I have a data flow object, with the source as EHSIDMS and the destination as EHSIT. I have a data conversion to convert the unicode to non-unicode. But how do I update based on the match? I've tried with the destination, using a SQL Command as the Data Access mode, but it doesn't appear to have the source table. If I just map the field to be updated, how does it limit it based on fields matching? I'm about to export my source table to Excel or something, and then try inputting from there, although it seems that all that would get me would be to remove the data conversion step. Shouldn't there be an update data task or something? Is it one of those Data Flow transformation tasks, and I'm just not figuring out which it is?

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  • XPath and XML: Multiple namespaces

    - by emragins
    So I have a document that looks like <a xmlns="uri1" xmlns:pre2="uri2"> <b xmlns:pre3="uri3"> <pre3:c> <stuff></stuff> <goes></goes> <here></here> </pre3:c> <pre3:d xmlns="uri4"> <under></under> <the></the> <tree></tree> </pre3:d> </b> </a> I want an xpath expression that will get me <under>. This has a namespaceURI of uri4. Right now my expression looks like: //ns:a/ns:b/pre3:d/pre4:under I have the namespace manager add 'ns' for the default namespace (uri1 in this case) and I have it defined with pre2, pre3, and pre4 for uri2, uri3, and uri4 respectively. I get the error "Expression must evaluate to a node-set." I know that the node exists. I know that everything up until the pre4:under in my xpath works fine as I use it in the rest of the document with no issues. It's the additional pre4:under that causes the error, and I'm not sure why. Any ideas? Thanks.

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  • Complex sorting on MySQL database

    - by ChrisR
    I'm facing the following situation. We've got an CMS with an entity with translations. These translations are stored in a different table with a one-to-many relationship. For example newsarticles and newsarticle_translations. The amount of available languages is dynamically determined by the same CMS. When entering a new newsarticle the editor is required to enter at least one translation, which one of the available languages he chooses is up to him. In the newsarticle overview in our CMS we would like to show a column with the (translated) article title, but since none of the languages are mandatory (one of them is mandatory but i don't know which one) i don't really know how to construct my mysql query to select a title for each newsarticle, regardless of the entered language. And to make it all a little harder, our manager asked for the possibilty to also be able to sort on title, so fetching the translations in a separate query is ruled out as far as i know. Anyone has an idea on how to solve this in the most efficient way? Here are my table schema's it it might help > desc news; +-----------------+----------------+------+-----+-------------------+----------------+ | Field | Type | Null | Key | Default | Extra | +-----------------+----------------+------+-----+-------------------+----------------+ | id | int(10) | NO | PRI | NULL | auto_increment | | category_id | int(1) | YES | | NULL | | | created | timestamp | NO | | CURRENT_TIMESTAMP | | | user_id | int(10) | YES | | NULL | | +-----------------+----------------+------+-----+-------------------+----------------+ > desc news_translations; +-----------------+------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-----------------+------------------+------+-----+---------+----------------+ | id | int(10) unsigned | NO | PRI | NULL | auto_increment | | enabled | tinyint(1) | NO | | 0 | | | news_id | int(1) unsigned | NO | | NULL | | | title | varchar(255) | NO | | | | | summary | text | YES | | NULL | | | body | text | NO | | NULL | | | language | varchar(2) | NO | | NULL | | +-----------------+------------------+------+-----+---------+----------------+ PS: i've though about subqueries and coalesce() solutions but those seem rather dirty tricks, wondering if something better is know that i'm not thinking of?

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  • Was Visual Studio 2008 or 2010 written to use multi cores?

    - by Erx_VB.NExT.Coder
    basically i want to know if the visual studio IDE and/or compiler in 2010 was written to make use of a multi core environment (i understand we can target multi core environments in 08 and 10, but that is not my question). i am trying to decide on if i should get a higher clock dual core or a lower clock quad core, as i want to try and figure out which processor will give me the absolute best possible experience with Visual Studio 2010 (ide and background compiler). if they are running the most important section (background compiler and other ide tasks) in one core, then the core will get cut off quicker if running a quad core, esp if background compiler is the heaviest task, i would imagine this would b e difficult to seperate in more then one process, so even if it uses multi cores you might still be better off with going for a higher clock cpu if the majority of the processing is still bound to occur in one core (ie the most significant part of the VS environment). i am a vb programmer, they've made great performance improvements in beta 2, congrats, but i would love to be able to use VS seamlessly... anyone have any ideas? thanks, erx

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  • Data structure to build and lookup set of integer ranges

    - by actual
    I have a set of uint32 integers, there may be millions of items in the set. 50-70% of them are consecutive, but in input stream they appear in unpredictable order. I need to: Compress this set into ranges to achieve space efficient representation. Already implemented this using trivial algorithm, since ranges computed only once speed is not important here. After this transformation number of resulting ranges is typically within 5 000-10 000, many of them are single-item, of course. Test membership of some integer, information about specific range in the set is not required. This one must be very fast -- O(1). Was thinking about minimal perfect hash functions, but they do not play well with ranges. Bitsets are very space inefficient. Other structures, like binary trees, has complexity of O(log n), worst thing with them that implementation make many conditional jumps and processor can not predict them well giving poor performance. Is there any data structure or algorithm specialized in integer ranges to solve this task?

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  • Using java to create a logistic model - arrays and properties

    - by Oliver Burdekin
    I'm currently trying to create a java model that will solve a problem we have. On a voluntary expedition each week we have some people leaving and some new people arriving. Accommodation is in tents. The tents sleep different numbers of people and certain rules apply. Males and females cannot be mixed and volunteers can be one of four types - school children/ research assistants/ scientific staff/ school teachers So types of volunteer and sexes cannot be mixed. Each week the manager spends hours trying to work this out so I've offered to make this model to keep my coding skills up. At present I'm working with arrays. Each tent is a 2D array [4][x] where x is the number of people it sleeps (each person sleeping there has 4 attributes). Each person is a 1D array with 4 attributes [4]. The idea is to check where people can go, cause the minimum movement for people staying on and solve this logistic problem. Does anyone have any better suggestions as to how to solve this? At present I'm finding it necessary to write a lot of code setting up and querying arrays. Any help is appreciated.

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  • Pascals Triangle by recursion

    - by Olpers
    Note : My Class Teacher gave me this question as an assignment... I am not asked to do it but please tell me how to do it with recursion Binomial coefficients can be calculated using Pascal's triangle: 1 n = 0 1 1 1 2 1 1 3 3 1 1 4 6 4 1 n = 4 Each new level of the triangle has 1's on the ends; the interior numbers are the sums of the two numbers above them. Task: Write a program that includes a recursive function to produce a list of binomial coefficients for the power n using the Pascal's triangle technique. For example, Input = 2 Output = 1 2 1 Input = 4 Output = 1 4 6 4 1 done this So Far but tell me how to do this with recursion... #include<stdio.h> int main() { int length,i,j,k; //Accepting length from user printf("Enter the length of pascal's triangle : "); scanf("%d",&length); //Printing the pascal's triangle for(i=1;i<=length;i++) { for(j=1;j<=length-i;j++) printf(" "); for(k=1;k<i;k++) printf("%d",k); for(k=i;k>=1;k--) printf("%d",k); printf("\n"); } return 0; }

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  • lapply slower than for-loop when used for a BiomaRt query. Is that expected?

    - by ptocquin
    I would like to query a database using BiomaRt package. I have loci and want to retrieve some related information, let say description. I first try to use lapply but was surprise by the time needed for the task to be performed. I thus tried a more basic for-loop and get a faster result. Is that expected or is something wrong with my code or with my understanding of apply ? I read other posts dealing with *apply vs for-loop performance (Here, for example) and I was aware that improved performance should not be expected but I don't understand why performance here is actually lower. Here is a reproducible example. 1) Loading the library and selecting the database : library("biomaRt") athaliana <- useMart("plants_mart_14") athaliana <- useDataset("athaliana_eg_gene",mart=athaliana) 2) Querying the database : loci <- c("at1g01300", "at1g01800", "at1g01900", "at1g02335", "at1g02790", "at1g03220", "at1g03230", "at1g04040", "at1g04110", "at1g05240" ) I create a function for the use in lapply : foo <- function(loci) { getBM("description","tair_locus",loci,athaliana) } When I use this function on the first element : > system.time(foo(cwp_loci[1])) utilisateur système écoulé 0.020 0.004 1.599 When I use lapply to retrieve the data for all values : > system.time(lapply(loci, foo)) utilisateur système écoulé 0.220 0.000 16.376 I then created a new function, adding a for-loop : foo2 <- function(loci) { for (i in loci) { getBM("description","tair_locus",loci[i],athaliana) } } Here is the result : > system.time(foo2(loci)) utilisateur système écoulé 0.204 0.004 10.919 Of course, this will be applied to a big list of loci, so the best performing option is needed. I thank you for assistance. EDIT Following recommendation of @MartinMorgan Simply passing the vector loci to getBM greatly improves the query efficiency. Simpler is better. > system.time(lapply(loci, foo)) utilisateur système écoulé 0.236 0.024 110.512 > system.time(foo2(loci)) utilisateur système écoulé 0.208 0.040 116.099 > system.time(foo(loci)) utilisateur système écoulé 0.028 0.000 6.193

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  • Is it safe to use a boolean flag to stop a thread from running in C#

    - by Lirik
    My main concern is with the boolean flag... is it safe to use it without any synchronization? I've read in several places that it's atomic. class MyTask { private ManualResetEvent startSignal; private CountDownLatch latch; private bool running; MyTask(CountDownLatch latch) { running = false; this.latch = latch; startSignal = new ManualResetEvent(false); } // A method which runs in a thread public void Run() { startSignal.WaitOne(); while(running) { startSignal.WaitOne(); //... some code } latch.Signal(); } public void Stop() { running = false; startSignal.Set(); } public void Start() { running = true; startSignal.Set(); } public void Pause() { startSignal.Reset(); } public void Resume() { startSignal.Set(); } } Is this a safe way to design a task? Any suggestions, improvements, comments? Note: I wrote my custom CountDownLatch class in case you're wondering where I'm getting it from.

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  • Time taken for memcpy decreases after certain point

    - by tss
    I ve a code which increases the size of the memory(identified by a pointer) exponentially. Instead of realloc, I use malloc followed by memcpy.. Something like this.. int size=5,newsize; int *c = malloc(size*sizeof(int)); int *temp; while(1) { newsize=2*size; //begin time temp=malloc(newsize*sizeof(int)); memcpy(temp,c,size*sizeof(int)); //end time //print time in mili seconds c=temp; size=newsize; } Thus the number of bytes getting copied is increasing exponentially. The time required for this task also increases almost linearly with the increase in size. However after certain point, the time taken abruptly reduces to a very small value and then remains constant. I recorded time for similar code, copyin data(Of my own type) 5 -> 10 - 2 ms 10 -> 20 - 2 ms . . 2560 -> 5120 - 5 ms . . 20480 -> 40960 - 30 ms 40960 -> 91920 - 58 ms 367680 -> 735360 - 2 ms 735360 -> 1470720 - 2 ms 1470720 -> 2941440 - 2 ms What is the reason for this drop in time ? Does a more optimal memcpy method get called when the size is large ?

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  • mysql data read returning 0 rows from class

    - by Neo
    I am implementing a database manager class within my app, mainly because there are 3 databases to connect to one being a local one. However the return function isn't working, I know the query brings back rows but when it is returned by the class it has 0. What am I missing? public MySqlDataReader localfetchrows(string query, List<MySqlParameter> dbparams = null) { using (var conn = connectLocal()) { Console.WriteLine("Connecting local : " + conn.ServerVersion); MySqlCommand sql = conn.CreateCommand(); sql.CommandText = query; if (dbparams != null) { if (dbparams.Count > 0) { sql.Parameters.AddRange(dbparams.ToArray()); } } MySqlDataReader reader = sql.ExecuteReader(); Console.WriteLine("Reading data : " + reader.HasRows + reader.FieldCount); return reader; /* using (MySqlCommand sql = conn.CreateCommand()) { sql.CommandText = query; if (dbparams != null) { if (dbparams.Count > 0) { sql.Parameters.AddRange(dbparams.ToArray()); } } MySqlDataReader reader = sql.ExecuteReader(); Console.WriteLine("Reading data : " + reader.HasRows + reader.FieldCount); sql.Parameters.Clear(); return reader; }*/ } } And the code to get the results query = @"SELECT jobtypeid, title FROM jobtypes WHERE active = 'Y' ORDER BY title ASC"; //parentfrm.jobtypes = db.localfetchrows(query); var rows = db.localfetchrows(query); Console.WriteLine("Reading data : " + rows.HasRows + rows.FieldCount); while (rows.Read()){ } These scripts return the following : Connecting local : 5.5.16 Reading data : True2 Reading data : False0

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  • How can I dynamically set the default namespace declaration of an XSLT transformation's output XML?

    - by Paralife
    I can do it, but not for the default namespace, using the <xsl:namespace>. If I try to do it for the default namespace: <xsl:namespace name="" select"myUri"/> it never works. It demands that I explicitly define the namespace of the element to be able to use the above null prefix declaration. The reason I want this is because I have a task to transform an input XML file to another output xml. The output XML has many elements and i dont want to have to explicitly set the namespace for every element. Thats why I want to set the default and never bother again. But the default must be computed from some data in the source XML. It does not change during the whole transformation, but it is dependent on input XML data. Any solution? EDIT 1: To sup up: I want to create a namespace dynamically and set it to be the default namespace of the output xml document. The uri of the namespace is derived from some data in the input XML. If I use <xsl:namespace> in my root output element, I cannot create a default namespace for it, only a prefixed one. And even with the prefixed one, it does not propagate to children.

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  • Execute JavaScript from within a C# assembly

    - by ScottKoon
    I'd like to execute JavaScript code from within a C# assembly and have the results of the JavaScript code returned to the calling C# code. It's easier to define things that I'm not trying to do: I'm not trying to call a JavaScript function on a web page from my code behind. I'm not trying to load a WebBrowser control. I don't want to have the JavaScript perform an AJAX call to a server. What I want to do is write unit tests in JavaScript and have then unit tests output JSON, even plain text would be fine. Then I want to have a generic C# class/executible that can load the file containing the JS, run the JS unit tests, scrap/load the results, and return a pass/fail with details during a post-build task. I think it's possible using the old ActiveX ScriptControl, but it seems like there ought to be a .NET way to do this without using SilverLight, the DLR, or anything else that hasn't shipped yet. Anyone have any ideas? update: From Brad Abrams blog namespace Microsoft.JScript.Vsa { [Obsolete("There is no replacement for this feature. Please see the ICodeCompiler documentation for additional help. http://go.microsoft.com/fwlink/?linkid=14202")] Clarification: We have unit tests for our JavaScript functions that are written in JavaScript using the JSUnit framework. Right now during our build process, we have to manually load a web page and click a button to ensure that all of the JavaScript unit tests pass. I'd like to be able to execute the tests during the post-build process when our automated C# unit tests are run and report the success/failure alongside of out C# unit tests and use them as an indicator as to whether or not the build is broken.

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  • Attempt to use a while loop for the 'next' arg of a for loop generates #arg error

    - by JerryK
    Am attempting to teach myself to program using Tcl. The task i've set myself to motivate my learning of Tcl is to solve the 8 queens problem. My approach to creating a program is to successively 'prototype' a solution. I have asked an earlier question related to the correctly laying out the nested for loops and received a helpful answer. To my dismay I find that the next development of my code creates the same interpreter error : "wrong # args" I have been careful to have an open brace at the end of the line preceding the while loop command. I've also tried to put the arguments of the whileloop in braces. This generates a different error. I have sincerely tried to understand the Tcl syntax man page - not too successfully - suggested by the answerer of my earlier question. Here is the code set allowd 1 set notallowd 0 for {set r1p 1} {$r1p <= 8} {incr r1p } { puts "1st row q placed at $r1p" ;# re-initialize r2 'free for q placemnt' array after every change of r1 q pos: for {set i 1 } {$i <= 8} {incr i} { set r2($i) $allowd } for { set r2($r1p) $notallowd ; set r2([expr $r1p-1]) $notallowd ; set r2([expr $r1p+1]) $notallowd ; set r2p 1} {$r2p <= 8} { ;# 'next' arg of r2 forloop will be a whileloop : while r2($r2p)== $notallowd incr r2p } { puts "2nd row q placed at $r2p" ;# end of 'commnd' arg of r2 forloop } } Where am I going wrong? EDIT : to provide clear reply @slebetman As stated in my text, I did brace the arguments of the whileloop (indeed that was how i first wrote the code) below is exactly the layout of the r2 forloop tried: for { set r2($r1p) $notallowd ; set r2([expr $r1p-1]) $notallowd ; set r2([expr $r1p+1]) $notallowd ; set r2p 1} {$r2p <= 8} { ;# 'next' arg of r2 forloop will be a whileloop : while { r2($r2p)== $notallowd } { incr r2p } } { puts "2nd row q placed at $r2p" ;# end of 'commnd' arg of r2 forloop } but this generates the fatal interpreter error : "unknown math function 'r2' while compiling while { r2($r2p .... "

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  • Rapid Opening and Closing System.IO.StreamWriter in C#

    - by ccomet
    Suppose you have a file that you are programmatically logging information into with regards to a process. Kinda like your typical debug Console.WriteLine, but due to the nature of the code you're testing, you don't have a console to write onto so you have to write it somewhere like a file. My current program uses System.IO.StreamWriter for this task. My question is about the approach to using the StreamWriter. Is it better to open just one StreamWriter instance, do all of the writes, and close it when the entire process is done? Or is it a better idea to open a new StreamWriter instance to write a line into the file, then immediately close it, and do this for every time something needs to be written in? In the latter approach, this would probably be facilitated by a method that would do just that for a given message, rather than bloating the main process code with excessive amounts of lines. But having a method to aid in that implementation doesn't necessarily make it the better choice. Are there significant advantages to picking one approach or the other? Or are they functionally equivalent, leaving the choice on the shoulders of the programmer?

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  • VB.NET Update Access Database with DataTable

    - by sinDizzy
    I've been perusing some hep forums and some help books but cant seem to get my head wrapped around this. My task is to read data from two text files and then load that data into an existing MS Access 2007 database. So here is what i'm trying to do: Read data from first text file and for every line of data add data to a DataTable using CarID as my unique field. Read data from second text file and look for existing CarID in DataTable if exists update that row. If it doesnt exist add a new row. once im done push the contents of the DataTable to the database. What i have so far: Dim sSQL As String = "SELECT * FROM tblCars" Dim da As New OleDb.OleDbDataAdapter(sSQL, conn) Dim ds As New DataSet da.Fill(ds, "CarData") Dim cb As New OleDb.OleDbCommandBuilder(da) 'loop read a line of text and parse it out. gets dd, dc, and carId 'create a new empty row Dim dsNewRow As DataRow = ds.Tables("CarData").NewRow() 'update the new row with fresh data dsNewRow.Item("DriveDate") = dd dsNewRow.Item("DCode") = dc dsNewRow.Item("CarNum") = carID 'about 15 more fields 'add the filled row to the DataSet table ds.Tables("CarData").Rows.Add(dsNewRow) 'end loop 'update the database with the new rows da.Update(ds, "CarData") Questions: In constructing my table i use "SELECT * FROM tblCars" but what if that table has millions of records already. Is that not a waste of resources? Should i be trying something different if i want to update with new records? Once Im done with the first text file i then go to my next text file. Whats the best approach here: To First look for an existing record based on CarNum or to create a second table and then merge the two at the end? Finally when the DataTable is done being populated and im pushing it to the database i want to make sure that if records already exist with three primary fields (DriveDate, DCode, and CarNum) that they get updated with new fields and if it doesn't exist then those records get appended. Is that possible with my process? tia AGP

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  • Memory mapping of files and system cache behavior in WinXP

    - by Canopus
    Our application is memory intensive and deals with reading a large number of disk files. The total load can be more than 3 GB. There is a custom memory manager that uses memory mapped files to achieve reading of such a huge data. The files are mapped into the process memory space only when needed and with this the process memory is well under control. But what is observed is, with memory mapping, the system cache keeps on increasing until it occupies the available physical memory. This leads to the slowing down of the entire system. My question is how to prevent system cache from hogging the physical memory? I attempted to remove the file buffering (by using FILE_FLAG_NO_BUFFERING ), but with this, the read operations take considerable amount of time and slows down the application performance. How to achieve the scalability without sacrificing much on performance. What are the common techniques used in such cases? I dont have a good understanding of the WinXP OS caching behavior. Any good links explaining the same would also be helpful.

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  • crash when using stl vector at instead of operator[]

    - by Jamie Cook
    I have a method as follows (from a class than implements TBB task interface - not currently multithreading though) My problem is that two ways of accessing a vector are causing quite different behaviour - one works and the other causes the entire program to bomb out quite spectacularly (this is a plugin and normally a crash will be caught by the host - but this one takes out the host program as well! As I said quite spectacular) void PtBranchAndBoundIterationOriginRunner::runOrigin(int origin, int time) const // NOTE: const method { BOOST_FOREACH(int accessMode, m_props->GetAccessModes()) { // get a const reference to appropriate vector from member variable // map<int, vector<double>> m_rowTotalsByAccessMode; const vector<double>& rowTotalsForAccessMode = m_rowTotalsByAccessMode.find(accessMode)->second; if (origin != 129) continue; // Additional debug constrain: I know that the vector only has one non-zero element at index 129 m_job->Write("size: " + ToString(rowTotalsForAccessMode.size())); try { // check for early return... i.e. nothing to do for this origin if (!rowTotalsForAccessMode[origin]) continue; // <- this works if (!rowTotalsForAccessMode.at(origin)) continue; // <- this crashes } catch (...) { m_job->Write("Caught an exception"); // but its not an exception } // do some other stuff } } I hate not putting in well defined questions but at the moment my best phrasing is : "WTF?" I'm compiling this with Intel C++ 11.0.074 [IA-32] using Microsoft (R) Visual Studio Version 9.0.21022.8 and my implementation of vector has const_reference operator[](size_type _Pos) const { // subscript nonmutable sequence #if _HAS_ITERATOR_DEBUGGING if (size() <= _Pos) { _DEBUG_ERROR("vector subscript out of range"); _SCL_SECURE_OUT_OF_RANGE; } #endif /* _HAS_ITERATOR_DEBUGGING */ _SCL_SECURE_VALIDATE_RANGE(_Pos < size()); return (*(_Myfirst + _Pos)); } (Iterator debugging is off - I'm pretty sure) and const_reference at(size_type _Pos) const { // subscript nonmutable sequence with checking if (size() <= _Pos) _Xran(); return (*(begin() + _Pos)); } So the only difference I can see is that at calls begin instead of simply using _Myfirst - but how could that possibly be causing such a huge difference in behaviour?

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  • Functioning Socket read no longer works when called in AsyncTask

    - by bibismcbryde
    I'm making an app that sends a string to a server over a socket and then reads the output after the server has processed that data. It worked perfectly when it was my foreground task, but I have since used AsyncTask to show a process dialog while the socket communication runs in the background, and things start breaking after I read the output from the server and then try to close the socket. private class Progressor extends AsyncTask<String, Void, Void> { ProgressDialog dialog; protected void onPreExecute() { dialog = ProgressDialog.show(ClearTalkInputActivity.this, "Loading..", "Analyzing Text", true, false); } protected Void doInBackground(String... strings) { String language = strings[0].toLowerCase(); String the_text = strings[1]; Socket socket = null; DataOutputStream dos = null; DataInputStream dis = null; try { socket = new Socket(my_ip, port); dos = new DataOutputStream(socket.getOutputStream()); dis = new DataInputStream(socket.getInputStream()); dos.writeUTF(language+"****"+the_text); String in = ""; while (in.indexOf("</content>") < 0) { in += dis.readUTF(); } socket.close(); save_str(OUTPUT_KEY, in); } catch (UnknownHostException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } finally { if (socket != null) { try { socket.close(); } catch (IOException e) { e.printStackTrace(); } } } if (dos != null) { try { dos.close(); } catch (IOException e) { e.printStackTrace(); } } if (dis != null) { try { dis.close(); } catch (IOException e) { e.printStackTrace(); } } return null; } protected void onPostExecute() { if (dialog.isShowing()) dialog.dismiss(); startActivity(new Intent (output_intent)); } }

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  • How to cancel a deeply nested process

    - by Mystere Man
    I have a class that is a "manager" sort of class. One of it's functions is to signal that the long running process of the class should shut down. It does this by setting a boolean called "IsStopping" in class. public class Foo { bool isStoping void DoWork() { while (!isStopping) { // do work... } } } Now, DoWork() was a gigantic function, and I decided to refactor it out and as part of the process broke some of it into other classes. The problem is, Some of these classes also have long running functions that need to check if isStopping is true. public class Foo { bool isStoping void DoWork() { while (!isStopping) { MoreWork mw = new MoreWork() mw.DoMoreWork() // possibly long running // do work... } } } What are my options here? I have considered passing isStopping by reference, which I don't really like because it requires there to be an outside object. I would prefer to make the additional classes as stand alone and dependancy free as possible. I have also considered making isStopping a property, and then then having it call an event that the inner classes could be subscribed to, but this seems overly complex. Another option was to create a "Process Cancelation Token" class, similar to what .net 4 Tasks use, then that token be passed to those classes. How have you handled this situation? EDIT: Also consider that MoreWork might have a EvenMoreWork object that it instantiates and calls a potentially long running method on... and so on. I guess what i'm looking for is a way to be able to signal an arbitrary number of objects down a call tree to tell them to stop what they're doing and clean up and return.

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