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• Validation in n-tier asp.net mvc applications

  - by sTodorov

  Dear Stack Overflow gurus, I am looking for some practical/theoretical information regarding best practices for validation in asp.net mvc n-tier applications. I am working on a .Net application divided into the following layers: UI - Mvc3 BLL layer - all business rules. Decoupled from data access and UI layers through interfaces DAL layer - Data access with the repository pattern, EF4 and pocos Now, I am looking for a nice, clean and transparent way to specify my validation rules. Here are some thoughts on the matter so far: UI validation should only be responsible for user input and its validity. BLL validation should be handling the validity of the data regarding the application business rules. My main concern is how to bind the BLL and UI validation in the most efficient way. One think I am would like to avoid is having the UI check in a collection of validation and adding manually errors to the ModelState. Furthermore, I do not want to pass the ModelState to the BLL to be populated in there. I will appreciate any thoughts on the matter. P.S. Should this question be marked as a discussion ?

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• An implementation of Sharir's or Aurenhammer's deterministic algorithm for calculating the intersect

  - by RGrey

  The problem of finding the intersection/union of 'N' discs/circles on a flat plane was first proposed by M. I. Shamos in his 1978 thesis: Shamos, M. I. “Computational Geometry” Ph.D. thesis, Yale Univ., New Haven, CT 1978. Since then, in 1985, Micha Sharir presented an O(n log2n) time and O(n) space deterministic algorithm for the disc intersection/union problem (based on modified Voronoi diagrams): Sharir, M. Intersection and closest-pair problems for a set of planar discs. SIAM .J Comput. 14 (1985), pp. 448-468. In 1988, Franz Aurenhammer presented a more efficient O(n log n) time and O(n) space algorithm for circle intersection/union using power diagrams (generalizations of Voronoi diagrams): Aurenhammer, F. Improved algorithms for discs and balls using power diagrams. Journal of Algorithms 9 (1985), pp. 151-161. Earlier in 1983, Paul G. Spirakis also presented an O(n^2) time deterministic algorithm, and an O(n) probabilistic algorithm: Spirakis, P.G. Very Fast Algorithms for the Area of the Union of Many Circles. Rep. 98, Dept. Comput. Sci., Courant Institute, New York University, 1983. I've been searching for any implementations of the algorithms above, focusing on computational geometry packages, and I haven't found anything yet. As neither appear trivial to put into practice, it would be really neat if someone could point me in the right direction!

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• Rails 3: Parsing XML

  - by gjb

  I have a simple XML document in the following format: <?xml version="1.0" encoding="utf-8"?> <object> <strField>Foo</strField> <intField>1</intField> <dateField>2010-11-03</dateField> <boolField>true</boolField> <nilField></nilField> </object> I would like to parse this into a Hash to be passed to Model.create: {:object => { :strField => 'Foo', :intField => 1, :dateField => Date.today, :boolField => true, :nilField => nil }} Sadly there are no "type" attributes in the XML, so using Hash.from_xml just parses each field as a string. What I am looking for is some sort of field type auto detection. I have also looked at Nokogiri, but that can't output as a Hash. What is the simplest and most efficient way to achieve this? Many thanks.

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• Finding Common Phrases in SQL Server TEXT Column

  - by regex

  Short Desc: I'm curious to see if I can use SQL Analysis services or some other SQL Server service to mine some data for me that will show commonalities between SQL TEXT fields in a dataset. Long Desc I am looking at a subset of data that consists of about 10,000 rows of TEXT blobs which are used as a notes column in a issue tracking (ticketing) software. I would like to use something out of the box (without having to build something) that might be able to parse through all of the rows and find commonly used byte sequences in the "Notes" column. In other words, I want to find commonly used phrases (two to three word phrases, so 9 - 20 character sections of the TEXT blob). This will help me better determine if associate's notes contain similar phrases (troubleshooting techniques) that we could standardize in our troubleshooting process flow. Closing Note I'd really rather not build an application to do this as my method will probably not be the most efficient way to do it. Hopefully all this makes sense. Please let me know in the comments if anything needs clarification.

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• [C#] Improving method to read signed 8-bit integers from hexadecimal.

  - by JYelton

  Scenario: I have a string of hexadecimal characters which encode 8-bit signed integers. Each two characters represent a byte which employ the leftmost (MSB) bit as the sign (rather than two's complement). I am converting these to signed ints within a loop and wondered if there's a better way to do it. There are too many conversions and I am sure there's a more efficient method that I am missing. Current Code: string strData = "FFC000407F"; // example input data, encodes: -127, -64, 0, 64, 127 int v; for (int x = 0; x < strData.Length/2; x++) { v = HexToInt(strData.Substring(x * 2, 2)); Console.WriteLine(v); // do stuff with v } private int HexToInt(string _hexData) { string strBinary = Convert.ToString(Convert.ToInt32(_hexData, 16), 2).PadLeft(_hexData.Length * 4, '0'); int i = Convert.ToInt32(strBinary.Substring(1, 7), 2); i = (strBinary.Substring(0, 1) == "0" ? i : -i); return i; } Question: Is there a more streamlined and direct approach to reading two hex characters and converting them to an int when they represent a signed int (-127 to 127) using the leftmost bit as the sign?

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• Which technology is best suited to store and query a huge readonly graph?

  - by asmaier

  I have a huge directed graph: It consists of 1.6 million nodes and 30 million edges. I want the users to be able to find all the shortest connections (including incoming and outgoing edges) between two nodes of the graph (via a web interface). At the moment I have stored the graph in a PostgreSQL database. But that solution is not very efficient and elegant, I basically need to store all the edges of the graph twice (see my question PostgreSQL: How to optimize my database for storing and querying a huge graph). It was suggested to me to use a GraphDB like neo4j or AllegroGraph. However the free version of AllegroGraph is limited to 50 million nodes and also has a very high-level API (RDF), which seems too powerful and complex for my problem. Neo4j on the other hand has only a very low level API (and the python interface is not mature yet). Both of them seem to be more suited for problems, where nodes and edges are frequently added or removed to a graph. For a simple search on a graph, these GraphDBs seem to be too complex. One idea I had would be to "misuse" a search engine like Lucene for the job, since I'm basically only searching connections in a graph. Another idea would be, to have a server process, storing the whole graph (500MB to 1GB) in memory. The clients could then query the server process and could transverse the graph very quickly, since the graph is stored in memory. Is there an easy possibility to write such a server (preferably in Python) using some existing framework? Which technology would you use to store and query such a huge readonly graph?

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• How to check for mutual existence of Fields in same table in Two columns

  - by ranabra

  I tried using "Exist" and "IN". Not only did I not succeed, it didn't seem as an efficient solution. Here is a simplified example: TblMyTable WorkerUserName  -  WorkerDegree  -  ManagerUserName  -  ManagerDegree I need a query where there is a mutual connection / existence. What I mean is only where the worker, ex. "John" has a manager named "Mary", and where Mary the manager has a worker named "John". John the worker can have several managers and Mary the manager can have several workers. So the result will be (the order doesn't matter) ideally in one line: John - BSc  --  Mary - M.A. or Mary - M.A.  --  John - BSc The punchline is it's only one table. it is not really managers and workers, this is just a simplification of the situation. In the real situation both are equal, in a Table of names of users working with other users. Database is SQL 2005. Many thanx in advance  

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• Using stdint.h and ANSI printf?

  - by nn

  Hi, I'm writing a bignum library, and I want to use efficient data types to represent the digits. Particularly integer for the digit, and long (if strictly double the size of the integer) for intermediate representations when adding and multiplying. I will be using some C99 functionality, but trying to conform to ANSI C. Currently I have the following in my bignum library: #include <stdint.h> #if defined(__LP64__) || defined(__amd64) || defined(__x86_64) || defined(__amd64__) || defined(__amd64__) || defined(_LP64) typedef uint64_t u_w; typedef uint32_t u_hw; #define BIGNUM_DIGITS 2048 #define U_HW_BITS 16 #define U_W_BITS 32 #define U_HW_MAX UINT32_MAX #define U_HW_MIN UINT32_MIN #define U_W_MAX UINT64_MAX #define U_W_MIN UINT64_MIN #else typedef uint32_t u_w; typedef uint16_t u_hw; #define BIGNUM_DIGITS 4096 #define U_HW_BITS 16 #define U_W_BITS 32 #define U_HW_MAX UINT16_MAX #define U_HW_MIN UINT16_MIN #define U_W_MAX UINT32_MAX #define U_W_MIN UINT32_MIN #endif typedef struct bn { int sign; int n_digits; // #digits should exclude carry (digits = limbs) int carry; u_hw tab[BIGNUM_DIGITS]; } bn; As I haven't written a procedure to write the bignum in decimal, I have to analyze the intermediate array and printf the values of each digit. However I don't know which conversion specifier to use with printf. Preferably I would like to write to the terminal the digit encoded in hexadecimal. The underlying issue is, that I want two data types, one that is twice as long as the other, and further use them with printf using standard conversion specifiers. It would be ideal if int is 32bits and long is 64bits but I don't know how to guarantee this using a preprocessor, and when it comes time to use functions such as printf that solely rely on the standard types I no longer know what to use.

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• SQL Where Clause Against View

  - by Adam Carr

  I have a view (actually, it's a table valued function, but the observed behavior is the same in both) that inner joins and left outer joins several other tables. When I query this view with a where clause similar to SELECT * FROM [v_MyView] WHERE [Name] like '%Doe, John%' ... the query is very slow, but if I do the following... SELECT * FROM [v_MyView] WHERE [ID] in ( SELECT [ID] FROM [v_MyView] WHERE [Name] like '%Doe, John%' ) it is MUCH faster. The first query is taking at least 2 minutes to return, if not longer where the second query will return in less than 5 seconds. Any suggestions on how I can improve this? If I run the whole command as one SQL statement (without the use of a view) it is very fast as well. I believe this result is because of how a view should behave as a table in that if a view has OUTER JOINS, GROUP BYS or TOP ##, if the where clause was interpreted prior to vs after the execution of the view, the results could differ. My question is why wouldn't SQL optimize my first query to something as efficient as my second query?

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• Codemetric optimized httpwebrequest in C#

  - by Omegavirus

  Hello, the problem is the httpwebrequest method in my c# program. visual studio gives it a metric of 60, thats pretty lame.. so how can i program it more efficient? (: my actual code: public string httpRequest(string url) { HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url); request.Method = "GET"; request.Proxy = WebRequest.DefaultWebProxy; request.MediaType = "HTTP/1.1"; request.ContentType = "text/xml"; request.UserAgent = "Mozilla/5.0 (Windows; U; Windows NT 6.1; de; rv:1.9.2.12) Gecko/20101026 Firefox/3.6.12"; HttpWebResponse response = (HttpWebResponse)request.GetResponse(); StreamReader streamr = new StreamReader(response.GetResponseStream(), Encoding.UTF8); String sresp = streamr.ReadToEnd(); streamr.Close(); return sresp; } thanks for helping. ;)

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• Delete all rows that do not have the value: Criteria 1 or Criteria 2 or Criteria 3 in Column D --> Using VBA Macro for excel

  - by JDS

  I am new to Macro's/VBA and cannot seem to figure out how to do this action for multiple criteria. I am trying to Delete all rows that do not have the value: Identify Fail or Identify Success in Column D. I write the following code and it works for one criteria "Identify Fail": '***********************************************' Sub DeleteRows() 'Action 1 --> Delete all Rows without Identify Fail in column D' Application.ScreenUpdating = False For i = Range("D" & Rows.Count).End(xlUp).Row To 1 Step -1 If Range("D" & i).Value <> "Identify Fail" Then Rows(i).Delete shift:=xlUp Next i Application.ScreenUpdating = True End Sub '***********************************************' Once I try to add 'OR' with another criteria it does not work: '***********************************************' Sub DeleteRows() 'Action 1 --> Delete all Rows without Identify Fail in column D' Application.ScreenUpdating = False For i = Range("D" & Rows.Count).End(xlUp).Row To 1 Step -1 If Range("D" & i).Value <> "Identify Fail" Or "Identify Success" Then Rows(i).Deleteshift:=xlUp Next i Application.ScreenUpdating = True End Sub '***********************************************' Any suggestions would be appreciated as I have been scouring this website and have not found an efficient code that will do the trick.

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• Optimising RSS parsing on App Engine to avoid high CPU warnings

  - by Danny Tuppeny

  I'm pulling some RSS feeds into a datastore in App Engine to serve up to an iPhone app. I use cron to schedule updating the RSS every x minutes. Each task only parses one RSS feed (which has 15-20 items). I frequently get warnings about high CPU usage in the App Engine dashboard, so I'm looking for ways to optimise my code. Currently, I use minidom (since it's already there on App Engine), but I suspect it's not very efficient! Here's the code: dom = minidom.parseString(urlfetch.fetch(url).content) if dom: items = [] for node in dom.getElementsByTagName('item'): item = RssItem( key_name = self.getText(node.getElementsByTagName('guid')[0].childNodes), title = self.getText(node.getElementsByTagName('title')[0].childNodes), description = self.getText(node.getElementsByTagName('description')[0].childNodes), modified = datetime.now(), link = self.getText(node.getElementsByTagName('link')[0].childNodes), categories = [self.getText(category.childNodes) for category in node.getElementsByTagName('category')] ); items.append(item); db.put(items); def getText(self, nodelist): rc = '' for node in nodelist: if node.nodeType == node.TEXT_NODE: rc = rc + node.data return rc There isn't much going on, but the scripts often take 2-6 seconds CPU time, which seems a bit excessive for looping through 20ish items and reading a few attributes. What can I do to make this faster? Is there anything particularly bad in the above code, or should I change to another way of parsing? Are there are any libraries (that work on App Engine) that would be better, or would I be better parsing the RSS myself?

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• Where to find algorithms for standard math functions?

  - by dsimcha

  I'm looking to submit a patch to the D programming language standard library that will allow much of std.math to be evaluated at compile time using the compile-time function evaluation facilities of the language. Compile-time function evaluation has several limitations, the most important ones being: You can't use assembly language. You can't call C code or code for which the source is otherwise unavailable. Several std.math functions violate these and compile-time versions need to be written. Where can I get information on good algorithms for computing things such as logarithms, exponents, powers, and trig functions? I prefer just high level descriptions of algorithms to actual code, for two reasons: To avoid legal ambiguity and the need to make my code look "different enough" from the source to make sure I own the copyright. I want simple, portable algorithms. I don't care about micro-optimization as long as they're at least asymptotically efficient. Edit: D's compile time function evaluation model allows floating point results computed at compile time to differ from those computed at runtime anyhow, so I don't care if my compile-time algorithms don't give exactly the same result as the runtime version as long as they aren't less accurate to a practically significant extent.

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• Improving method to read signed 8-bit integers from hexadecimal.

  - by JYelton

  Scenario: I have a string of hexadecimal characters which encode 8-bit signed integers. Each two characters represent a byte which employ the leftmost (MSB) bit as the sign (rather than two's complement). I am converting these to signed ints within a loop and wondered if there's a better way to do it. There are too many conversions and I am sure there's a more efficient method that I am missing. Current Code: string strData = "FFC000407F"; // example input data, encodes: -127, -64, 0, 64, 127 int v; for (int x = 0; x < strData.Length/2; x++) { v = HexToInt(strData.Substring(x * 2, 2)); Console.WriteLine(v); // do stuff with v } private int HexToInt(string _hexData) { string strBinary = Convert.ToString(Convert.ToInt32(_hexData, 16), 2).PadLeft(_hexData.Length * 4, '0'); int i = Convert.ToInt32(strBinary.Substring(1, 7), 2); i = (strBinary.Substring(0, 1) == "0" ? i : -i); return i; } Question: Is there a more streamlined and direct approach to reading two hex characters and converting them to an int when they represent a signed int (-127 to 127) using the leftmost bit as the sign?

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• Comparing two collections for equality

  - by Crossbrowser

  I would like to compare two collections (in C#), but I'm not sure of the best way to implement this efficiently. I've read the other thread about Enumerable.SequenceEqual, but it's not exactly what I'm looking for. In my case, two collections would be equal if they both contain the same items (no matter the order). Example: collection1 = {1, 2, 3, 4}; collection2 = {2, 4, 1, 3}; collection1 == collection2; // true What I usually do is to loop through each item of one collection and see if it exists in the other collection, then loop through each item of the other collection and see if it exists in the first collection. (I start by comparing the lengths). if (collection1.Count != collection2.Count) return false; // the collections are not equal foreach (Item item in collection1) { if (!collection2.Contains(item)) return false; // the collections are not equal } foreach (Item item in collection2) { if (!collection1.Contains(item)) return false; // the collections are not equal } return true; // the collections are equal However, this is not entirely correct, and it's probably not the most efficient way to do compare two collections for equality. An example I can think of that would be wrong is: collection1 = {1, 2, 3, 3, 4} collection2 = {1, 2, 2, 3, 4} Which would be equal with my implementation. Should I just count the number of times each item is found and make sure the counts are equal in both collections? The examples are in some sort of C# (let's call it pseudo-C#), but give your answer in whatever language you wish, it does not matter. Note: I used integers in the examples for simplicity, but I want to be able to use reference-type objects too (they do not behave correctly as keys because only the reference of the object is compared, not the content).

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• Online voice chat: Why client-server model vs. peer-to-peer model?

  - by sstallings

  I am adding online voice chat to a Silverlight app. I've been reviewing current apps, services and SDKs found thru online searches and forums. I'm finding that the majority of these implement a client-server (C/S) model and I'm trying to understand why that model versus a peer-to-peer (PTP) model. To me PTP would be preferable because going direct between peers would be more efficient (fewer IP hops and no processing along the way by a server computer) and no need for a server and its costs and dependencies. I found some products offer the ability to switch from PTP to C/S if the PTP proves insufficient. As I thought more about it, I could see that C/S could be better if there are more than two peers involved in a conversation, then the server (supposedly with more bandwidth) could do a better job of relaying each peers outgoing traffic to the multiple other peers. In C/S many-to-many voice chatting, each peer's upstream broadband (which is where the bottleneck inherently is) would only have to carry each item of voice traffic once, then the server would use its superior bandwidth to relay the message to the multiple other peers. But, in a situation with one-on-one voice chatting it seems that PTP would be best. A server would not reduce each of the two peer's bandwidth requirements and would only add unnecessary overhead, dependency and cost. In one-on-one voice chatting: Am I mistaken on anything above? Would peer-to-peer be best? Would a server provide anything of value that could not be provided by a client-only program? Is there anything else that I should be taking into consideration? And lastly, can you recommend any Silverlight PTP or C/S voice chat products? Thanks in advance for any info.

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• Create a unique ID by fuzzy matching of names (via agrep using R)

  - by tbrambor

  Using R, I am trying match on people's names in a dataset structured by year and city. Due to some spelling mistakes, exact matching is not possible, so I am trying to use agrep() to fuzzy match names. A sample chunk of the dataset is structured as follows: df <- data.frame(matrix( c("1200013","1200013","1200013","1200013","1200013","1200013","1200013","1200013", "1996","1996","1996","1996","2000","2000","2004","2004","AGUSTINHO FORTUNATO FILHO","ANTONIO PEREIRA NETO","FERNANDO JOSE DA COSTA","PAULO CEZAR FERREIRA DE ARAUJO","PAULO CESAR FERREIRA DE ARAUJO","SEBASTIAO BOCALOM RODRIGUES","JOAO DE ALMEIDA","PAULO CESAR FERREIRA DE ARAUJO"), ncol=3,dimnames=list(seq(1:8),c("citycode","year","candidate")) )) The neat version: citycode year candidate 1 1200013 1996 AGUSTINHO FORTUNATO FILHO 2 1200013 1996 ANTONIO PEREIRA NETO 3 1200013 1996 FERNANDO JOSE DA COSTA 4 1200013 1996 PAULO CEZAR FERREIRA DE ARAUJO 5 1200013 2000 PAULO CESAR FERREIRA DE ARAUJO 6 1200013 2000 SEBASTIAO BOCALOM RODRIGUES 7 1200013 2004 JOAO DE ALMEIDA 8 1200013 2004 PAULO CESAR FERREIRA DE ARAUJO I'd like to check in each city separately, whether there are candidates appearing in several years. E.g. in the example, PAULO CEZAR FERREIRA DE ARAUJO PAULO CESAR FERREIRA DE ARAUJO appears twice (with a spelling mistake). Each candidate across the entire data set should be assigned a unique numeric candidate ID. The dataset is fairly large (5500 cities, approx. 100K entries) so a somewhat efficient coding would be helpful. Any suggestions as to how to implement this?

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• Can someone help me refactor this C# linq business logic for efficiency?

  - by Russell

  I feel like this is not a very efficient way of using linq. I was hoping somebody on here would have a suggestion for a refactor. I realize this code is not very pretty, as I was in a complete rush. public class Workflow { public void AssignForms() { using (var cntx = new ProjectBusiness.Providers.ProjectDataContext()) { var emplist = (from e in cntx.vw_EmployeeTaskLists where e.OwnerEmployeeID == null select e).ToList(); foreach (var emp in emplist) { // if employee has a form assigned: break; if (emp.GRADE > 15 || (emp.Pay_Plan.ToLower().Contains("al") || emp.Pay_Plan.ToLower().Contains("ex"))) { //Assign278(); } else if ((emp.Series.Contains("0905") || emp.Series.Contains("0511") || emp.Series.Contains("0110") || emp.Series.Contains("1801")) || (emp.GRADE >= 12 && emp.GRADE <= 15)) { var emptask = new ProjectBusiness.Providers.EmployeeTask(); emptask.TimespanID = cntx.Timespans.SingleOrDefault(t => t.BeginDate.Year == DateTime.Today.Year & t.EndDate.Year == DateTime.Today.Year).TimespanID; var FormID = (from f in cntx.Forms where f.FormName.Contains("450") select f.FormID).FirstOrDefault(); var TaskStatusID = (from s in cntx.TaskStatus where s.StatusDescription.ToLower() == "not started" select s.TaskStatusID).FirstOrDefault(); Assign450((int)emp.EmployeeID, FormID, TaskStatusID, emptask); cntx.EmployeeTasks.InsertOnSubmit(emptask); } else { //Assign185(); } } cntx.SubmitChanges(); } } private void Assign450(int EmployeeID, int FormID, int TaskStatusID, ProjectBusiness.Providers.EmployeeTask emptask) { emptask.FormID = FormID; emptask.OwnerEmployeeID = EmployeeID; emptask.AssignedToEmployeeID = EmployeeID; emptask.TaskStatusID = TaskStatusID; emptask.DueDate = DateTime.Today; } }

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• Why do people hate SQL cursors so much?

  - by Steven A. Lowe

  I can understand wanting to avoid having to use a cursor due to the overhead and inconvenience, but it looks like there's some serious cursor-phobia-mania going on where people are going to great lengths to avoid having to use one for example, one question asked how to do something obviously trivial with a cursor and the accepted answer proposed using a common table expression (CTE) recursive query with a recursive custom function, even though this limits the number of rows that could be processed to 32 (due to recursive call limit in sql server). This strikes me as a terrible solution for system longevity, not to mention a tremendous effort just to avoid using a simple cursor. what is the reason for this level of insane hatred? has some 'noted authority' issued a fatwa against cursors? does some unspeakable evil lurk in the heart of cursors that corrupts the morals of the children or something? wiki question, more interested in the answer than the rep thanks in advance! Related Info: http://stackoverflow.com/questions/37029/sql-server-fast-forward-cursors EDIT: let me be more precise: I understand that cursors should not be used instead of normal relational operations, that is a no-brainer. What I don't understand is people going waaaaay out of their way to avoid cursors like they have cooties or something, even when a cursor is a simpler and/or more efficient solution. It's the irrational hatred that baffles me, not the obvious technical efficiencies.

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• How to append new elements to Xml from a stream

  - by Wololo

  I have a method which returns some xml in a memory stream private MemoryStream GetXml() { XmlWriterSettings settings = new XmlWriterSettings(); settings.Indent = true; using (MemoryStream memoryStream = new MemoryStream()) { using (XmlWriter writer = XmlWriter.Create(memoryStream, settings)) { writer.WriteStartDocument(); writer.WriteStartElement("root"); writer.WriteStartElement("element"); writer.WriteString("content"); writer.WriteEndElement(); writer.WriteEndElement(); writer.WriteEndDocument(); writer.Flush(); } return memoryStream; } } In this example the format of the xml will be: <?xml version="1.0" encoding="utf-8"?> <root> <element>content</element> </root> How can i insert a new element under the root e.g <?xml version="1.0" encoding="utf-8"?> <root> <element>content</element> ----->New element here <------ </root> EDIT: Also please suggest the most efficient method as returning a memorystream may not be the best solution. The final xml will be passed to a custom HttpHandler so what are the best options for writing the output? context.Response.Write vs context.Response.OutputStream

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• Determining whether geographic point is within X meters of a state border (using shapefile for borde

  - by DanM

  So I'm writing a Java app, and I've got an ESRI Shapefile which contains the borders of all the U.S. states. What I need is to be able to determine whether any given lat/lon point is within a specified distance from ANY state border line - i.e., I will not be specifying a particular border line, just need to see whether the point is close to any of them. The solution does NOT have to be very precise at all; e.g. I don't need to be dealing with measuring perpendicular to the border, or whatever. Just checking to see if going X meters north, south, east or west would result in crossing a border would be more than sufficient. The solution DOES have to be computationally efficient, as I'll be performing a huge number of these calculations. I'm planning to use the GeoTools library (though if there's a simpler option, I'm all for it) with the Shapefile plugin. What I don't really understand is: Once I've got the shapefile loaded into memory, how do I check to see whether I'm near a border? Thanks! -Dan

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• Doing large updates against indexed view

  - by user217136

  We have an indexed view that runs across three large tables. Two of these tables (A & B) are constantly getting updated with user transactions and the other table (C) contains data product info that is needs to be updated once a week. This product table contains over 6 million records. We need this view across these three tables for our core business process and unfortunately we cannot change this aspect. We even had a sql server MVP come in to help test under load to make sure we have the most efficient configuration. There is one column in the product table that gets utilized in the view and has to be updated each week. The problem we are now encountering is that as volume is increasing on our transactions against tables A & B, the update to Table C is causing deadlocks. I have tried several different methods to no avail: 1) I was hoping that we could change the view so that table C could be a dirty read "WITH (NOLOCK)" but apparently that functionality is not available with indexes views. 2) I thought about updating a new column in Table C and then just renaming it when the process is done but you cannot do that due to the dependency in the view. 3) I also entertained the idea of writing this value to a temporary product table, and then running an ALTER statement against the view to have it point to my new table. however when i did that the indexes on my view were dropped and it took quite a bit of time to recreate them. 4) we tried to do the weekly update in small chunks (as small as 100 records at a time) but we still run into dead locks. questions: a) we are using sql server 2005. Does sql server 2008 have a new functionality with their indexed views that would help us? Is there now a way to do dirty reads w/ an indexed view? b) a better approach to altering an existing view to point to a new table? thanks!

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• Implementing parts of rfc4226 (HOTP) in mysql

  - by Moose Morals

  Like the title says, I'm trying to implement the programmatic parts of RFC4226 "HOTP: An HMAC-Based One-Time Password Algorithm" in SQL. I think I've got a version that works (in that for a small test sample, it produces the same result as the Java version in the code), but it contains a nested pair of hex(unhex()) calls, which I feel can be done better. I am constrained by a) needing to do this algorithm, and b) needing to do it in mysql, otherwise I'm happy to look at other ways of doing this. What I've got so far: -- From the inside out... -- Concatinate the users secret, and the number of time its been used -- find the SHA1 hash of that string -- Turn a 40 byte hex encoding into a 20 byte binary string -- keep the first 4 bytes -- turn those back into a hex represnetation -- convert that into an integer -- Throw away the most-significant bit (solves signed/unsigned problems) -- Truncate to 6 digits -- store into otp -- from the otpsecrets table select (conv(hex(substr(unhex(sha1(concat(secret, uses))), 1, 4)), 16, 10) & 0x7fffffff) % 1000000 into otp from otpsecrets; Is there a better (more efficient) way of doing this?

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• Updating a Minimum spanning tree when a new edge is inserted

  - by Lynette

  Hello, I've been presented the following problem in University: Let G = (V, E) be an (undirected) graph with costs ce = 0 on the edges e € E. Assume you are given a minimum-cost spanning tree T in G. Now assume that a new edge is added to G, connecting two nodes v, tv € V with cost c. a) Give an efficient algorithm to test if T remains the minimum-cost spanning tree with the new edge added to G (but not to the tree T). Make your algorithm run in time O(|E|). Can you do it in O(|V|) time? Please note any assumptions you make about what data structure is used to represent the tree T and the graph G. b)Suppose T is no longer the minimum-cost spanning tree. Give a linear-time algorithm (time O(|E|)) to update the tree T to the new minimum-cost spanning tree. This is the solution I found: Let e1=(a,b) the new edge added Find in T the shortest path from a to b (BFS) if e1 is the most expensive edge in the cycle then T remains the MST else T is not the MST It seems to work but i can easily make this run in O(|V|) time, while the problem asks O(|E|) time. Am i missing something? By the way we are authorized to ask for help from anyone so I'm not cheating :D Thanks in advance

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• Modify Executing Jar file

  - by pinkynobrain

  Hello Stack Overflow friends. I have a simple problem which i fear doesnt have a simple solution and i need advice as to how to proceed. I am developing a java application packaged as and executable JAR but it requires to modify some of its JAR file contents during execution. At this stage i hit a problem because some OS lock the file preventing writes to it. It is essential that the user sees an updated version of the jar file by the time the application exits allthough i can be pretty flexible as to how to achieve this. A clean and efficient solution is obviously prefereable but portability is the only hard requirement. The following are three approaches i can see to solving the problem, feel free to comment on them or suggest others. Tell Java to unlock the JAR file for writing(this doesnt seem possible but it would be the easyest solution) Copy the executable class files to a tempory file on application startup, use a class loader to load these files and unload the ones from the initial JAR file.(Not had much experience with the classloaders but hopefully the JVM would then be smart enough to realize that the original JAR is nolonger in use and so unlock it) Put a Second executable JAR File inside the First, on startup extract the inner jar to e temporaryfile, invoke a new java process and pass it the location of the Outer JAR, first process exits, second process modifys the Outer jar unincumbered.(This will work but im not sure there is a platform independant way of one java app invoking another) I know this is a weird question but any help would be appreciated.

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