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• Static Data Structures on Embedded Devices (Android in particular)

  - by Mark

  I've started working on some Android applications and have a question regarding how people normally deal with situations where you have a static data set and have an application where that data is needed in memory as one of the standard java collections or as an array. In my current specific issue i have a spreadsheet with some pre-calculated data. It consists of ~100 rows and 3 columns. 1 Column is a string, 1 column is a float, 1 column is an integer. I need access to this data as an array in java. It seems like i could: 1) Encode in XML - This would be cpu intensive to decode in my experience. 2) build into SQLite database - seems like a lot of overhead for static access to data i only need array style access to in ram. 3) Build into binary blob and read in. (never done this in java, i miss void *) 4) Build a python script to take the CSV version of my data and spit out a java function that adds the values to my desired structure with hard coded values. 5) Store a string array via androids resource mechanism and compute the other 2 columns on application load. In my case the computation would require a lot of calls to Math.log, Math.pow and Math.floor which i'd rather not have to do for load time and battery usage reasons. I mostly work in low power embedded applications in C and as such #4 is what i'm used to doing in these situations. It just seems like it should be far easier to gain access to static data structures in java/android. Perhaps I'm just being too battery usage conscious and in my single case i imagine the answer is that it doesn't matter much, but if every application took that stance it could begin to matter. What approaches do people usually take in this situation? Anything I missed?

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• iPhone - dequeueReusableCellWithIdentifier usage

  - by Jukurrpa

  Hi, I'm working on a iPhone app which has a pretty large UITableView with data taken from the web, so I'm trying to optimize its creation and usage. I found out that dequeueReusableCellWithIdentifier is pretty useful, but after seeing many source codes using this, I'm wondering if the usage I make of this function is the good one. Here is what people usually do: UITableViewCell* cell = [tableView dequeueReusableCellWithIdentifier:@"Cell"]; if (cell == nil) { cell = [[UITableViewCell alloc] initWithFrame:CGRectZero reuseIdentifier:@"Cell"]; // Add elements to the cell return cell; And here is the way I did it: NSString identifier = [NSString stringWithFormat:@"Cell @d", indexPath.row]: // The cell row UITableViewCell* cell = [tableView dequeueReusableCellWithIdentifier:identifier]; if (cell != nil) return cell; cell = [[UITableViewCell alloc] initWithFrame:CGRectZero reuseIdentifier:identifier]; // Add elements to the cell return cell; The difference is that people use the same identifier for every cell, so dequeuing one only avoids to alloc a new one. For me, the point of queuing was to give each cell a unique identifier, so when the app asks for a cell it already displayed, neither allocation nor element adding have to be done. In fine I don't know which is best, the "common" method ceils the table's memory usage to the exact number of cells it display, whislt the method I use seems to favor speed as it keeps all calculated cells, but can cause large memory consumption (unless there's an inner limit to the queue). Am I wrong to use it this way? Or is it just up to the developper, depending on his needs?

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• Does replace into have a where clause?

  - by Lajos Arpad

  I'm writing an application and I'm using MySQL as DBMS, we are downloading property offers and there were some performance issues. The old architecture looked like this: A property is updated. If the number of affected rows is not 1, then the update is not considered successful, elseway the update query solves our problem. If the update was not successful, and the number of affected rows is more than 1, we have duplicates and we delete all of them. After we deleted duplicates if needed if the update was not successful, an insert happens. This architecture was working well, but there were some speed issues, because properties are deleted if they were not updated for 15 days. Theoretically the main problem is deleting properties, because some properties are alive for months and the indexes are very far from each other (we are talking about 500, 000+ properties). Our host told me to use replace into instead of deleting properties and all deprecated properties should be considered as DEAD. I've done this, but problems started to occur because of syntax error and I couldn't find anywhere an example of replace into with a where clause (I'd like to replace a DEAD property with the new property instead of deleting the old property and insert a new to assure optimization). My query looked like this: replace into table_name(column1, ..., columnn) values(value1, ..., valuen) where ID = idValue Of course, I've calculated idValue and handled everything but I had a syntax error. I would like to know if I'm wrong and there is a where clause for replace into. I've found an alternative solution, which is even better than replace into (using simply an update query) because deletes are happening behind the curtains if I use replace into, but I would like to know if I'm wrong when I say that replace into doesn't have a where clause. For more reference, see this link: http://dev.mysql.com/doc/refman/5.0/en/replace.html Thank you for your answers in advance, Lajos Árpád

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• Cleanest RESTful design for purely "action" calls?

  - by Josh Handel

  Hello all, I am sticking my toe in the RESTful waters and I just can't find a "satisfactory" solution to how to handle truely "action" oriented calls on a RESTful service? My quandry can be broken down into two parts. 1) Transactional calls: I understand the idea of having an ActionTransactor that you get a resource too with a post, update the parameters and then commit with a PUT (as described all over the place and in the Orilly RESTful Web services book).. But I struggle with the idea of keeping URLs with states present for ever.. If we really honestly don't need to keep a transaction for ever can we kill the resource URI? do URIs need to be perminate or can they be transiant URIs that expire 2) Non transactional calls: these might be calls to perform some workflow that spans multiple resources but having a resource just doesn't make since.. An example might be to re-generating some calculated ans cached value like a large aggreget or re-indexing blog or some such "purely" action. Anyways, I'm curious about the communities thoughts on this... Thus far, I've read that Overloading Post is the cleanest way to handle part 2.. But there is an equal amount of argument against that approach as well. And (to me) its not self documenting which I though was one of the key design goals of RESTful APIs.

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• Lost Update Anomaly in Sql Server Update Command

  - by Javed

  Hi, I am very much confused. I have a transaction in ReadCommitted Isolation level. Among other things I am also updating a counter value in it, something similar to below: Update tblCount set counter = counter + 1 My application is a desktop application and this transaction happens to occur quite frequently and concurrently. We recently noticed an error that sometimes the counter value doesn't get updated or is missed. We also insert one record on each counter update so we are sure that records have been inserted but somehow counter fails to update. This happens once in 2000 simulaneous transactions. I seriously doubt it is a lost update anomaly I am facing but if you look at the command above, it's just update the counter from its own value: if I have started a transaction and the transaction has reached this statement, it should have locked the row. This should not cause lost update, but it's happening somehow. Is the thing that this update command works in two parts? Like first it reads the counter value (during which it doesn't get the exclusive lock) and then writes the new calculated value (when it does get an exclusive lock)? Please help, I have got really confused.

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• stock management of assemblys and its sub parts

  - by The Disintegrator

  I have to track the stock of individual parts and kits (assembly) and can't find a satisfactory way of doing this. Sample bogus and hyper simplified database: Table prod: prodID 1 prodName Flux capacitor prodCost 900 prodPrice 1350 (900*1.5) prodStock 3 - prodID 2 prodName Mr Fusion prodCost 300 prodPrice 600 (300*2) prodStock 2 - prodID 3 prodName Time travel kit prodCost 1650 (1350+300) prodPrice 2145 (1650*1.3) prodStock 2 Table rels relID 1 relSrc 1 (Flux capacitor) relType 4 (is a subpart of) relDst 3 (Time travel kit) - relID 2 relSrc 2 (Mr Fusion) relType 4 (is a subpart of) relDst 3 (Time travel kit) prodPrice: it's calculated based on the cost but not in a linear way. In this example for costs of 500 or less, the markup is a 200%. For costs of 500-1000 the markup is 150%. For costs of 1000+ the markup is 130% That's why the time travel kit is much cheaper than the individual parts prodStock: here is my problem. I can sell kits or the individual parts, So the stock of the kits is virtual. The problem when I buy: Some providers sell me the Time Travel kit as a whole (with one barcode) and some sells me the individual parts (with a different barcode) So when I load the stock I don't know how to impute it. The problem when I sell: If I only sell kits, calculate the stock would be easy: "I have 3 Flux capacitors and 2 Mr Fusions, so I have 2 Time travel kits and a Flux Capacitor" But I can sell Kits or individual parts. I have to track the stock of the individual parts and the possible kits at the same time (and I have to compensate for the sell price) Probably this is really simple, but I can't see a simple solution. Resuming: I have to find a way of tracking the stock and the database/program is the one who has to do it (I cant ask the clerk to correct the stock) I'm using php+MySql. But this is more a logical problem than a programing one

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• Best fit curve for trend line

  - by Dave Jarvis

  Problem Constraints Size of the data set, but not the data itself, is known. Data set grows by one data point at a time. Trend line is graphed one data point at a time (using a spline/Bezier curve). Graphs The collage below shows data sets with reasonably accurate trend lines: The graphs are: Upper-left. By hour, with ~24 data points. Upper-right. By day for one year, with ~365 data points. Lower-left. By week for one year, with ~52 data points. Lower-right. By month for one year, with ~12 data points. User Inputs The user can select: the type of time series (hourly, daily, monthly, quarterly, annual); and the start and end dates for the time series. For example, the user could select a daily report for 30 days in June. Trend Weight To calculate the window size (i.e., the number of data points to average when calculating the trend line), the following expression is used: data points / trend weight Where data points is derived from user inputs and trend weight is 6.4. Even though a trend weight of 6.4 produces good fits, it is rather arbitrary, and might not be appropriate for different user inputs. Question How should trend weight be calculated given the constraints of this problem?

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• Quadratic Bezier Curve: Calculate Tangent

  - by stefan.at.wpf

  I have a quadratic bezier curve and I want to calculate the slope of the tangent in a given point. For example, let it be the middlepoint of the quadratic bezier curve, therefore t=0.5 (please see the link below for a picture of this). I've calculated the first derivative of the formula for the quadratic bezier curve; however I get 400 as value for the slope, though it should be 0. Maybe I'm using the first derivative in a wrong way? I know I could also calculate the tangents using trigonometric functions; however I'd like to do it using the first derivative, shouldn't this be possible? Thanks for any hint! For clarification / please note: I'm interested in a general way to get the slope in a arbitrary given point on a quadratic bezier curve, not only to get the tangent in the start- and end point. A picture of my problem including the text above: http://cid-0432ee4cfe9c26a0.skydrive.live.com/self.aspx/%c3%96ffentlich/Quadratic%20Bezier%20Curve.pdf Thank you very much for any hint!

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• How to simply a foreach iteration using reflection

  - by Priya

  Consider that I have to get the overall performance of X. X has Y elements and Y in turn has Z elements which inturn has some N elements. To get the performance of X I do this: List<double> XQ = new List<double>(); foreach (Elem Y in X.Y){ List<double> YQ = new List<double>(); foreach (Elem Z in Y.Z){ List<double> ZQ = new List<double>(); foreach (Elem N in Z.N){ ZQ.Add(GetPerformance(N)); } YQ.Add(AVG(ZQ)); } XQ.Add(AVG(YQ)); } AVG of XQ list gives the performance of X. The performance can be calculated for either X or Y or for Z. X, Y and Z share the same base class. So depending on the item given the foreach loop has to be executed. Currently I have a switch case to determine each item (X or Y or Z) and the foreach loop is repeated in the code pertaining to the item (eg. If Y foreach starts from Y.Z). Is is possible to convert this whole code generic using reflection instead of having to repeat it in each switch case? Thanks

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• Problem with copying local data onto HDFS on a Hadoop cluster using Amazon EC2/ S3.

  - by Deepak Konidena

  Hi, I have setup a Hadoop cluster containing 5 nodes on Amazon EC2. Now, when i login into the Master node and submit the following command bin/hadoop jar <program>.jar <arg1> <arg2> <path/to/input/file/on/S3> It throws the following errors (not at the same time.) The first error is thrown when i don't replace the slashes with '%2F' and the second is thrown when i replace them with '%2F': 1) Java.lang.IllegalArgumentException: Invalid hostname in URI S3://<ID>:<SECRETKEY>@<BUCKET>/<path-to-inputfile> 2) org.apache.hadoop.fs.S3.S3Exception: org.jets3t.service.S3ServiceException: S3 PUT failed for '/' XML Error Message: The request signature we calculated does not match the signature you provided. check your key and signing method. Note: 1)when i submitted jps to see what tasks were running on the Master, it just showed 1116 NameNode 1699 Jps 1180 JobTracker leaving DataNode and TaskTracker. 2)My Secret key contains two '/' (forward slashes). And i replace them with '%2F' in the S3 URI. PS: The program runs fine on EC2 when run on a single node. Its only when i launch a cluster, i run into issues related to copying data to/from S3 from/to HDFS. And, what does distcp do? Do i need to distribute the data even after i copy the data from S3 to HDFS?(I thought, HDFS took care of that internally) IF you could direct me to a link that explains running Map/reduce programs on a hadoop cluster using Amazon EC2/S3. That would be great. Regards, Deepak.

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• Stock management of assemblies and its sub parts

  - by The Disintegrator

  I have to track the stock of individual parts and kits (assemblies) and can't find a satisfactory way of doing this. Sample bogus and hyper simplified database: Table prod: prodID 1 prodName Flux capacitor prodCost 900 prodPrice 1350 (900*1.5) prodStock 3 - prodID 2 prodName Mr Fusion prodCost 300 prodPrice 600 (300*2) prodStock 2 - prodID 3 prodName Time travel kit prodCost 1650 (1350+300) prodPrice 2145 (1650*1.3) prodStock 2 Table rels relID 1 relSrc 1 (Flux capacitor) relType 4 (is a subpart of) relDst 3 (Time travel kit) - relID 2 relSrc 2 (Mr Fusion) relType 4 (is a subpart of) relDst 3 (Time travel kit) prodPrice: it's calculated based on the cost but not in a linear way. In this example for costs of 500 or less, the markup is a 200%. For costs of 500-1000 the markup is 150%. For costs of 1000+ the markup is 130% That's why the time travel kit is much cheaper than the individual parts prodStock: here is my problem. I can sell kits or the individual parts, So the stock of the kits is virtual. The problem when I buy: Some providers sell me the Time Travel kit as a whole (with one barcode) and some sells me the individual parts (with a different barcode) So when I load the stock I don't know how to impute it. The problem when I sell: If I only sell kits, calculate the stock would be easy: "I have 3 Flux capacitors and 2 Mr Fusions, so I have 2 Time travel kits and a Flux Capacitor" But I can sell Kits or individual parts. So, I have to track the stock of the individual parts and the possible kits at the same time (and I have to compensate for the sell price) Probably this is really simple, but I can't see a simple solution. Resuming: I have to find a way of tracking the stock and the database/program is the one who has to do it (I cant ask the clerk to correct the stock) I'm using php+MySql. But this is more a logical problem than a programing one

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• Haskell Linear Algebra Matrix Library for Arbitrary Element Types

  - by Johannes Weiß

  I'm looking for a Haskell linear algebra library that has the following features: Matrix multiplication Matrix addition Matrix transposition Rank calculation Matrix inversion is a plus and has the following properties: arbitrary element (scalar) types (in particular element types that are not Storable instances). My elements are an instance of Num, additionally the multiplicative inverse can be calculated. The elements mathematically form a finite field (??2256). That should be enough to implement the features mentioned above. arbitrary matrix sizes (I'll probably need something like 100x100, but the matrix sizes will depend on the user's input so it should not be limited by anything else but the memory or the computational power available) as fast as possible, but I'm aware that a library for arbitrary elements will probably not perform like a C/Fortran library that does the work (interfaced via FFI) because of the indirection of arbitrary (non Int, Double or similar) types. At least one pointer gets dereferenced when an element is touched (written in Haskell, this is not a real requirement for me, but since my elements are no Storable instances the library has to be written in Haskell) I already tried very hard and evaluated everything that looked promising (most of the libraries on Hackage directly state that they wont work for me). In particular I wrote test code using: hmatrix, assumes Storable elements Vec, but the documentation states: Low Dimension : Although the dimensionality is limited only by what GHC will handle, the library is meant for 2,3 and 4 dimensions. For general linear algebra, check out the excellent hmatrix library and blas bindings I looked into the code and the documentation of many more libraries but nothing seems to suit my needs :-(. Update Since there seems to be nothing, I started a project on GitHub which aims to develop such a library. The current state is very minimalistic, not optimized for speed at all and only the most basic functions have tests and therefore should work. But should you be interested in using or helping out developing it: Contact me (you'll find my mail address on my web site) or send pull requests.

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• how can I add a custom non-DataTable column to my DataView, in a winforms ADO.net application?

  - by Greg

  Hi, How could I (/is it possible) to add a custom column to my DataView, and in this column display the result of a specific calculation. That is, I currently have a dataGridView which has a binding to a DataView, based on the DataTable from my database. I'd like to add an additional column to the dataGridView to display a number which is calculated by looking at this current row plus it's children row. In other words the info for the column isn't just derivable from the row data itself. Specific questions might be: a) where to add the column itself? to the DataView I assume? b) which method / event to trigger the re-calculation of the value of this custom column from ( / how do I control this) Thanks PS. I've also noted if I use the following code/approach I get a infinite loop... // Custom Items DataColumn dc = new DataColumn("OverallSize", typeof(long)); DT_Webfiles.Columns.Add(dc); DT_Webfiles.RowChanged += new DataRowChangeEventHandler(DT_Row_Changed); private static void DT_Row_Changed(object sender, DataRowChangeEventArgs e) { e.Row["OverallSize"] = e.Row["OverallSize"] ?? 0; e.Row["OverallSize"] = (long)e.Row["OverallSize"] + 1; } What other approach could avoid this looping. i.e. currently I'm saying update the value of the custom column when the row changes, however after then changing the row it triggers antoher 'row has changed' event...

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• Stock management of assemblies and its sub parts (relations)

  - by The Disintegrator

  I have to track the stock of individual parts and kits (assemblies) and can't find a satisfactory way of doing this. Sample bogus and hyper simplified database: Table prod: prodID 1 prodName Flux capacitor prodCost 900 prodPrice 1350 (900*1.5) prodStock 3 - prodID 2 prodName Mr Fusion prodCost 300 prodPrice 600 (300*2) prodStock 2 - prodID 3 prodName Time travel kit prodCost 1650 (1350+300) prodPrice 2145 (1650*1.3) prodStock 2 Table rels relID 1 relSrc 1 (Flux capacitor) relType 4 (is a subpart of) relDst 3 (Time travel kit) - relID 2 relSrc 2 (Mr Fusion) relType 4 (is a subpart of) relDst 3 (Time travel kit) prodPrice: it's calculated based on the cost but not in a linear way. In this example for costs of 500 or less, the markup is a 200%. For costs of 500-1000 the markup is 150%. For costs of 1000+ the markup is 130% That's why the time travel kit is much cheaper than the individual parts prodStock: here is my problem. I can sell kits or the individual parts, So the stock of the kits is virtual. The problem when I buy: Some providers sell me the Time Travel kit as a whole (with one barcode) and some sells me the individual parts (with a different barcode) So when I load the stock I don't know how to impute it. The problem when I sell: If I only sell kits, calculate the stock would be easy: "I have 3 Flux capacitors and 2 Mr Fusions, so I have 2 Time travel kits and a Flux Capacitor" But I can sell Kits or individual parts. So, I have to track the stock of the individual parts and the possible kits at the same time (and I have to compensate for the sell price) Probably this is really simple, but I can't see a simple solution. Resuming: I have to find a way of tracking the stock and the database/program is the one who has to do it (I cant ask the clerk to correct the stock) I'm using php+MySql. But this is more a logical problem than a programing one

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• Updating UIView subclass contents

  - by Brett

  Hi; I am trying to update a UIView subclass to draw individual pixels (rectangles) after calculating if they are in the mandelbrot set. I am using the following code but am getting a blank screen: //drawingView.h ... -(void)drawRect:(CGRect)rect{ CGContextRef context = UIGraphicsGetCurrentContext(); CGContextSetRGBFillColor(context, r, g, b, 1); CGContextSetRGBStrokeColor(context, r, g, b, 1); CGRect arect = CGRectMake(x,y,1,1); CGContextFillRect(context, arect); } ... //viewController.m ... - (void)viewDidLoad { [drawingView setX:10]; [drawingView setY:10]; [drawingView setR:0.0]; [drawingView setG:0.0]; [drawingView setB:0.0]; [super viewDidLoad]; [drawingView setNeedsDisplay]; } Once I figure out how to display one pixel, I'd like to know how to go about updating the view by adding another pixel (once calculated). Once all the variables change, how do I keep the current view as is but add another pixel? Thanks, Brett

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• Delphi 2009 dbExpress and Interbase: Unicode migration steps and risks?

  - by mjustin

  Currently, our database uses Win1252 as the only character encoding. We will have to support Unicode in the database tables soon, which means we have to perform this migration for four databases and around 80 Delphi applications which run in-house in a 24/7 environment. Are there recommendations for database migrations to UTF-8 (or UNICODE_FSS) for Delphi applications? Some questions listed below. Many thanks in advance for your answers! are there tools which help with the migration of the existing databases (sizes between 250 MB and 2 GB, no Blob fields), by dumping the data, recreating the database with UNICODE_FSS or UTF-8, and loading the data back? are there known problems with Delphi 2009, dbExpress and Interbase 7.5 related to Unicode character sets? would you recommend to upgrade the databases to Interbase 2009 first? (This upgrade is planned but does not have a high priority) can we simply migrate the database and Delphi will handle the Unicode character sets automatically, or will we have to change all character field types in every Datamodule (dfm and source code) too? which strategy would you recommend to work on the migration in parallel with the normal development and maintenance of the existing application? The application runs in-house so development and database administration is done internally. Update: one problem I found now is that there are two different persistent field types for Unicode and non Unicode character fields. For the existing database, dbExpress creates TStringField objects. For the Unicode database fields, dbExpress creates (or expects!) TWideStringField objects. This looks like a lot of work lies ahead. While we could try to avoid persistent fields (and add calculated fields at run time), Of course we would prefer a solution which does not require so many changes in existing units and DFM files.

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• PHP Performance Metrics

  - by bigstylee

  I am currently developing a PHP MVC Framework for a personal project. While I am developing the framework I am interested to see any notable performance by implementing different techniques for optimization. I have implemented a crude BenchMark class that logs mircotime. The problem is I have no frame of reference for execution times. I am very near the beginnig of this project with a database connection and a few queries but no output (bar some debugging text and BenchMark log). I have a current execution time of 0.01917 seconds. I was expecting this to be lower but as I said before I have no frame of reference. I appreciate there are many variables to take into account when juding performance but I am hoping to find some sort of metric to a) techniques to measure performance for example requests per second and b) compare results for example; how a "moderately" sized PHP application on a "standard" webserver will perform. I appreciate "moderately" and "standard" are very subjective words so perhaps a table of known execution times for a particular application (eg StackOverFlow's executing time). What are other techniques of measuring performance are there other than execution time? When looking at MVC Framework Performance Comparisom it talks about Requests Per Second (RPS). How is this calculated? I am guessing with my current execution time of 0.01917 seconds can handle 52 RPS (= 1 / 0.01917 ). This seems to be significantly lower than that quoted on the graph especially when you consider my current limited funcitonality.

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• RIA: how to get functionality, not a data

  - by Budda

  On the server side I have the following class: public class Customer { [Key] public int Id { get; set; } public string FirstName { get; set; } public string SecondName { get; set; } public string FullName { get { return string.Concat(FirstName, " ", SecondName); } } } The problem is that each field is calculated and transferred to the client, for example 'FullName' property: [DataMember()] [Editable(false)] [ReadOnly(true)] public string FullName { get { return this._fullName; } set { if ((this._fullName != value)) { this.ValidateProperty("FullName", value); this.OnFullNameChanging(value); this._fullName = value; this.RaisePropertyChanged("FullName"); this.OnFullNameChanged(); } } } Instead of data transferring (that is traffic consuming, in some cases it introduces significant overhead). I would like to have a calculation on the client side. Is this possible without manual duplication of the property implementation? Thank you.

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• Memcache key generation strategy

  - by Maxim Veksler

  Given function f1 which receives n String arguments, would be considered better random key generation strategy for memcache for the scenario described below ? Our Memcache client does internal md5sum hashing on the keys it gets public class MemcacheClient { public Object get(String key) { String md5 = Md5sum.md5(key) // Talk to memcached to get the Serialization... return memcached(md5); } } First option public static String f1(String s1, String s2, String s3, String s4) { String key = s1 + s2 + s3 + s4; return get(key); } Second option /** * Calculate hash from Strings * * @param objects vararg list of String's * * @return calculated md5sum hash */ public static String stringHash(Object... strings) { if(strings == null) throw new NullPointerException("D'oh! Can't calculate hash for null"); MD5 md5sum = new MD5(); // if(prevHash != null) // md5sum.Update(prevHash); for(int i = 0; i < strings.length; i++) { if(strings[i] != null) { md5sum.Update("_" + strings[i] + "_"); // Convert to String... } else { // If object is null, allow minimum entropy by hashing it's position md5sum.Update("_" + i + "_"); } } return md5sum.asHex(); } public static String f1(String s1, String s2, String s3, String s4) { String key = stringHash(s1, s2, s3, s4); return get(key); } Note that the possible problem with the second option is that we are doing second md5sum (in the memcache client) on an already md5sum'ed digest result. Thanks for reading, Maxim.

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• Calculate shortest path through a grocery store

  - by Bart

  Hi, I'm trying to find a way to find the shortest path through a grocery store, visiting a list of locations (shopping list). The path should start at a specified startposition and can end at multiple endpositions (there are multiple checkout counters). Also, I have some predefined constraints on the path, such as "item x on the shopping list needs to be the last, second last, or third last item on the path". There is a function that will return true or false for a given path. Finally, this needs to be calculated with limited cpu power (on a smartphone) and within a second or so. If this isn't possible, then an approximation to the optimal path is also ok. Is this possible? So far I think I need to start by calculating the distance between every item on the list using something like A* or Dijkstra's. After that, should I treat it like the travelling salesman problem? Because in my problem there is a specified startnode, specified endnodes, and some constraints, which are not in the travelling salesman problem. Any help would be appreciated :)

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• Problem in print layout near page end

  - by Miraaj

  Hi all, I am facing some problem in print layout, below is the description of steps I followed and problem which I am facing: I have taken a custom view over which there are NSTextViews, NSTableViews arranged one below other. I am trying to calculate exact height of NSTextViews and NSTableViews depending upon content in them. Depending upon calculated height I am arranging them in super-custom view. Then I am printing the view, using this code : [self arrangeBriefLayoutDynamically]; // step 2nd and 3rd // setting fixed parameters for printing NSPrintInfo * printInfo = [NSPrintInfo sharedPrintInfo]; [printInfo setVerticallyCentered:NO]; [printInfo setRightMargin:12.0]; [printInfo setTopMargin:37.0]; [printInfo setLeftMargin:12.0]; [printInfo setHorizontallyCentered:YES]; [printInfo setHorizontalPagination:NSFitPagination]; [printInfo setVerticalPagination:NSAutoPagination]; [printInfo setPaperName:@"na-letter"]; [printInfo setOrientation:NSPortraitOrientation]; PMSetScale([printInfo PMPageFormat], 100.0); [NSPrintInfo setSharedPrintInfo:printInfo]; [briefCompleteView print:nil]; Problem is : when size of a table view or text view exceeds, such that it crosses the page boundary then SOMETIMES text near boundary appears improper i.e.. part of its height lies on first page and rest of it lies on second page. Click to check problem ! Can anyone suggest me some way to resolve it ? Thanks, Miraaj

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• Using java2d user space measurements with TextLayout and LineBreakMeasurer

  - by Andrew Wheeler

  I have a java2d image defined in user space (mm) to print an identity card. The transformation to pixels is by using an AffineTransform for the required DPI (Screen or print). I want to wrap text across several lines but the the TextLayout does not respect user space co-ordinates. private void drawParagraph(Graphics2D g2d, Rectangle2D area, String text) { LineBreakMeasurer lineMeasurer; AttributedString string = new AttributedString(text); AttributedCharacterIterator paragraph = string.getIterator(); int paragraphStart = paragraph.getBeginIndex(); int paragraphEnd = paragraph.getEndIndex(); FontRenderContext frc = g2d.getFontRenderContext(); lineMeasurer = new LineBreakMeasurer(paragraph, frc); float breakWidth = (float)area.getWidth(); float drawPosY = (float)area.getY(); float drawPosX = (float)area.getX(); lineMeasurer.setPosition(paragraphStart); while (lineMeasurer.getPosition() < paragraphEnd) { TextLayout layout = lineMeasurer.nextLayout(breakWidth); drawPosY += layout.getAscent(); layout.draw(g2d, drawPosX, drawPosY); drawPosY += layout.getDescent() + layout.getLeading(); } } The above code determines font metrics using user space sizing of the Font and thus turn out rather large. The font size is calculated as best vertical fit for the number of lines in an area with the calculation as below. E.g. attr.put(TextAttribute.SIZE, (geTextArea().getHeight() / noOfLines - LINE_SPACING) ); When using g2d.drawString("Some text to display", x, y); the font size appears correct. Does anyone have a better way of doing text layout in user space co-ords?

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• Exponential regression : p-value and F significance

  - by Saravanan K

  I am new to statistics. I have a set of independent data and dependent data (X,Y), where I would like to do an exponential regression to obtain its p-value and significant F (already obtained R2 and also the coefficients through mathematical calculation). What is the natural evolution from the (X,Y) data to mathematically calculate those variables. Spent a week on the internet to study this but unable to find the right answer. Often an exponential data, y=be^(mx) will be converted first to a linear data, ln y = mx + ln b . Then a linear regression will done on the converted data, obtaining its p-value etc. Assume we use a statistical tool such as Excel's Analysis ToolPak: Data Analysis : Regression, it will produce a result such as below, I believe the p-value and Significant F value is representing the converted linear data and not the original exponential data. Questions: What is the approach/steps used by Excel to get the p-value and Significant F value for the converted linear data as shown in the statistic output in the image above? It is not clear in their help page or website. Can the p-value and Significant F could be mathematically calculated for exponential regression without using a statistical tool? Can you assist to point me to the right link if this has been answered before.

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• Positioning problem in VIsta when Aero Theme is enabled

  - by Adeel Rehman

  Hi, I have a Windows form which has tab pages. On a Tab Page, I have a Combo Box. When I click the combobox a drop down opens up just below the combo box to give the impression of a drop down. The drop down is a windows form and this is how I set its position Popup.Location = control.PointToScreen(parentcontrol.PointToClient(new System.Drawing.Point(0, control.Height))); Popup = drop down that opens below the combo box (Windows Form) control = my combo box (Combo Box) parentcontrol = the windows form on which the control is present (Parent Form) Problem:- The X coordinate is not plotted correctly on the screen with Aero theme enabled. This works perfectly fine on XP (with some variance in y due to tablelayout panel i assume). But when i use the same code on Vista with Aero theme enabled the x-cordinate wanders away about 20-30 pixels. If I Turn Aero theme off on Vista, it works fine. I have found the X and Y coordiantes calculated in both cases are the same. But the way Vista draws these coordinates on the screen (when aero theme is enabled) is different. Is there any solution to this problem? Thanks, Adeel Rehman.

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• Get Last Friday of Month in Java

  - by Nick Klauer

  I am working on a project where the requirement is to have a date calculated as being the last Friday of a given month. I think I have a solution that only uses standard Java, but I was wondering if anyone knew of anything more concise or efficient. Below is what I tested with for this year: for (int month = 0; month < 13; month++) { GregorianCalendar d = new GregorianCalendar(); d.set(d.MONTH, month); System.out.println("Last Week of Month in " + d.getDisplayName(d.MONTH, Calendar.LONG, Locale.ENGLISH) + ": " + d.getLeastMaximum(d.WEEK_OF_MONTH)); d.set(d.DAY_OF_WEEK, d.FRIDAY); d.set(d.WEEK_OF_MONTH, d.getActualMaximum(d.WEEK_OF_MONTH)); while (d.get(d.MONTH) > month || d.get(d.MONTH) < month) { d.add(d.WEEK_OF_MONTH, -1); } Date dt = d.getTime(); System.out.println("Last Friday of Last Week in " + d.getDisplayName(d.MONTH, Calendar.LONG, Locale.ENGLISH) + ": " + dt.toString()); }

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