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• Xcache - No different after using it

  - by Charles Yeung

  Hi I have installed Xcache in my site(using xampp), I have tested more then 10 times on several page and the result is same as default(no any cache installed), is it something wrong with the configure? Updated [xcache-common] ;; install as zend extension (recommended), normally "$extension_dir/xcache.so" zend_extension = /usr/local/lib/php/extensions/non-debug-non-zts-xxx/xcache.so zend_extension_ts = /usr/local/lib/php/extensions/non-debug-zts-xxx/xcache.so ;; For windows users, replace xcache.so with php_xcache.dll zend_extension_ts = C:\xampp\php\ext\php_xcache.dll ;; or install as extension, make sure your extension_dir setting is correct ; extension = xcache.so ;; or win32: ; extension = php_xcache.dll [xcache.admin] xcache.admin.enable_auth = On xcache.admin.user = "mOo" ; xcache.admin.pass = md5($your_password) xcache.admin.pass = "" [xcache] ; ini only settings, all the values here is default unless explained ; select low level shm/allocator scheme implemenation xcache.shm_scheme = "mmap" ; to disable: xcache.size=0 ; to enable : xcache.size=64M etc (any size > 0) and your system mmap allows xcache.size = 60M ; set to cpu count (cat /proc/cpuinfo |grep -c processor) xcache.count = 1 ; just a hash hints, you can always store count(items) > slots xcache.slots = 8K ; ttl of the cache item, 0=forever xcache.ttl = 0 ; interval of gc scanning expired items, 0=no scan, other values is in seconds xcache.gc_interval = 0 ; same as aboves but for variable cache xcache.var_size = 4M xcache.var_count = 1 xcache.var_slots = 8K ; default ttl xcache.var_ttl = 0 xcache.var_maxttl = 0 xcache.var_gc_interval = 300 xcache.test = Off ; N/A for /dev/zero xcache.readonly_protection = Off ; for *nix, xcache.mmap_path is a file path, not directory. ; Use something like "/tmp/xcache" if you want to turn on ReadonlyProtection ; 2 group of php won't share the same /tmp/xcache ; for win32, xcache.mmap_path=anonymous map name, not file path xcache.mmap_path = "/dev/zero" ; leave it blank(disabled) or "/tmp/phpcore/" ; make sure it's writable by php (without checking open_basedir) xcache.coredump_directory = "" ; per request settings xcache.cacher = On xcache.stat = On xcache.optimizer = Off [xcache.coverager] ; per request settings ; enable coverage data collecting for xcache.coveragedump_directory and xcache_coverager_start/stop/get/clean() functions (will hurt executing performance) xcache.coverager = Off ; ini only settings ; make sure it's readable (care open_basedir) by coverage viewer script ; requires xcache.coverager=On xcache.coveragedump_directory = "" Thanks you

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• Scala actors: receive vs react

  - by jqno

  Let me first say that I have quite a lot of Java experience, but have only recently become interested in functional languages. Recently I've started looking at Scala, which seems like a very nice language. However, I've been reading about Scala's Actor framework in Programming in Scala, and there's one thing I don't understand. In chapter 30.4 it says that using react instead of receive makes it possible to re-use threads, which is good for performance, since threads are expensive in the JVM. Does this mean that, as long as I remember to call react instead of receive, I can start as many Actors as I like? Before discovering Scala, I've been playing with Erlang, and the author of Programming Erlang boasts about spawning over 200,000 processes without breaking a sweat. I'd hate to do that with Java threads. What kind of limits am I looking at in Scala as compared to Erlang (and Java)? Also, how does this thread re-use work in Scala? Let's assume, for simplicity, that I have only one thread. Will all the actors that I start run sequentially in this thread, or will some sort of task-switching take place? For example, if I start two actors that ping-pong messages to each other, will I risk deadlock if they're started in the same thread? According to Programming in Scala, writing actors to use react is more difficult than with receive. This sounds plausible, since react doesn't return. However, the book goes on to show how you can put a react inside a loop using Actor.loop. As a result, you get loop { react { ... } } which, to me, seems pretty similar to while (true) { receive { ... } } which is used earlier in the book. Still, the book says that "in practice, programs will need at least a few receive's". So what am I missing here? What can receive do that react cannot, besides return? And why do I care? Finally, coming to the core of what I don't understand: the book keeps mentioning how using react makes it possible to discard the call stack to re-use the thread. How does that work? Why is it necessary to discard the call stack? And why can the call stack be discarded when a function terminates by throwing an exception (react), but not when it terminates by returning (receive)? I have the impression that Programming in Scala has been glossing over some of the key issues here, which is a shame, because otherwise it's a truly excellent book.

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• How to split HTML code with javascript or JQuery

  - by Dean

  Hi I'm making a website using JSP and servlets and I have to now break up a list of radio buttons to insert a textarea and a button. I have got the button and textarea to hide and show when you click on the radio button it shows the text area and button. But this only appears at the top and when there are hundreds on the page this will become awkward so i need a way for it to appear underneath. Here is what my HTML looks like when complied: <form action="addSpotlight" method="POST"> <table> <tr><td><input type="radio" value="29" name="publicationIDs" ></td><td>A System For Dynamic Server Allocation in Application Server Clusters, IEEE International Symposium on Parallel and Distributed Processsing with Applications, 2008</td> </tr> <tr><td><input type="radio" value="30" name="publicationIDs" ></td><td>Analysing BitTorrent's Seeding Strategies, 7th IEEE/IFIP International Conference on Embedded and Ubiquitous Computing (EUC-09), 2009</td> </tr> <tr><td><input type="radio" value="31" name="publicationIDs" ></td><td>The Effect of Server Reallocation Time in Dynamic Resource Allocation, UK Performance Engineering Workshop 2009, 2009</td> </tr> <tr><td><input type="radio" value="32" name="publicationIDs" ></td><td>idk, hello, 1992</td> </tr> <tr><td><input type="radio" value="33" name="publicationIDs" ></td><td>sad, safg, 1992</td> </tr> <div class="abstractWriteup"><textarea name="abstract"></textarea> <input type="submit" value="Add Spotlight"></div> </table> </form> Now here is what my JSP looks like: <form action="addSpotlight" method="POST"> <table> <%int i = 0; while(i<ids.size()){%> <tr><td><input type="radio" value="<%=ids.get(i)%>" name="publicationIDs" ></td><td><%=info.get(i)%></td> </tr> <%i++; }%> <div class="abstractWriteup"><textarea name="abstract"></textarea> <input type="submit" value="Add Spotlight"></div> </table> </form> Thanks in Advance Dean

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• What are the benefits of using ORM over XML Serialization/Deserialization?

  - by Tequila Jinx

  I've been reading about NHibernate and Microsoft's Entity Framework to perform Object Relational Mapping against my data access layer. I'm interested in the benefits of having an established framework to perform ORM, but I'm curious as to the performance costs of using it against standard XML Serialization and Deserialization. Right now, I develop stored procedures in Oracle and SQL Server that use XML Types for either input or output parameters and return or shred XML depending on need. I use a custom database command object that uses generics to deserialize the XML results into a specified serializable class. By using a combination of generics, xml (de)serialization and Microsoft's DAAB, I've got a process that's fairly simple to develop against regardless of the data source. Moreover, since I exclusively use Stored Procedures to perform database operations, I'm mostly protected from changes in the data structure. Here's an over-simplified example of what I've been doing. static void main() { testXmlClass test = new test(1); test.Name = "Foo"; test.Save(); } // Example Serializable Class ------------------------------------------------ [XmlRootAttribute("test")] class testXmlClass() { [XmlElement(Name="id")] public int ID {set; get;} [XmlElement(Name="name")] public string Name {set; get;} //create an instance of the class loaded with data. public testXmlClass(int id) { GenericDBProvider db = new GenericDBProvider(); this = db.ExecuteSerializable("myGetByIDProcedure"); } //save the class to the database... public Save() { GenericDBProvider db = new GenericDBProvider(); db.AddInParameter("myInputParameter", DbType.XML, this); db.ExecuteSerializableNonQuery("mySaveProcedure"); } } // Database Handler ---------------------------------------------------------- class GenericDBProvider { public T ExecuteSerializable<T>(string commandText) where T : class { XmlSerializer xml = new XmlSerializer(typeof(T)); // connection and command code is assumed for the purposes of this example. // the final results basically just come down to... return xml.Deserialize(commandResults) as T; } public void ExecuteSerializableNonQuery(string commandText) { // once again, connection and command code is assumed... // basically, just execute the command along with the specified // parameters which have been serialized. } public void AddInParameter(string name, DbType type, object value) { StringWriter w = new StringWriter(); XmlSerializer x = new XmlSerializer(value.GetType()); //handle serialization for serializable classes. if (type == DbType.Xml && (value.GetType() != typeof(System.String))) { x.Serialize(w, value); w.Close(); // store serialized object in a DbParameterCollection accessible // to my other methods. } else { //handle all other parameter types } } } I'm starting a new project which will rely heavily on database operations. I'm very curious to know whether my current practices will be sustainable in a high-traffic situation and whether or not I should consider switching to NHibernate or Microsoft's Entity Framework to perform what essentially seems to boil down to the same thing I'm currently doing. I appreciate any advice you may have.

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• Any way to speed up this hierarchical query?

  - by RenderIn

  I've got a serious performance problem with a hierarchical query that I can't seem to fix. I am modeling several organization charts in my database, each representing a virtual organization within our company. For example, we have several temporary committees that are created from time to time and there may be a Committee Organizer role at the top of this virtual hierarchy, with several people assigned to the Committee Member role beneath the organizer. Some of our virtual organizations have many levels and several branches at each level. I have a single table in which I represent all the role assignments. i.e. a ROLE_ID column and a PARENT_ROLE_ID column which is a foreign key to the ROLE_ID column. For each assignment we also store as a column the location in the company where this person has the assignment. For example, the Committee Organizer would have a company-level/ CEO assignment, while the committee members would have department-level assignments such as ACCOUNTING, MARKETING, etc. So to model the organizer/member relationship for two individuals we would have: ROLE_ID = 4 PARENT_ROLE_ID = NULL EMPLOYEE_NUMBER = 213423 COMPANY_LOCATION = CEO ROLE_ID = 5 PARENT_ROLE_ID = 4 EMPLOYEE_NUMBER = 838221 COMPANY_LOCATION = ACCOUNTING Here's where things get tricky. I have an application that every person in the organization can log in to. When they log in they should be able to view all the virtual organizations in our company. e.g. the committee members should be able to see the committee organizer and vice-versa. However, only the committee organizer should be able to edit the committee members. The difficulty is in determining whether an individual (who can have multiple role assignments) has edit access for each other assignment. While this seems simple in the example, consider a virtual organization in which we have President at the top, 5 departments directly beneath him, 2 subdepartments below each department. We only want people in the Accounting department to be able to edit individuals in the subdepartments belonging to the Accounting department. They should not have edit access to anybody in the Marketing department or its subdepartments. To determine edit access when a user views a virtual organization in our company I run a query that executes two inline views: A) Hierarchically query for all assignments in this virtual organization and using SYS_CONNECT_BY_PATH to store the entire path to each user/role/company_location and B) Hierarchically retrieve all the assignments the individual logged in has and using the SYS_CONNECT_BY_PATH to store the entire path to each of these assignments. The result of the query is all the records from A) plus a boolean determined by joining with B) which flags whether the logged in user has edit access for each record. Indexes don't seem to be helping... it simply appears that there is too much processing going on to separate all the records and then determine edit access. One issue is that I can't store the SYS_CONNECT_BY_PATH and index it... determining whether an individual record has edit access consists of comparing if: test_record_sys_path LIKE individual_record_sys_path || '%' Is a materialized view the answer?

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• Error in facebook.dll facebooksdk

  - by Surendar Radhakrishnan

  I got the web application working with facebooksdk and when i deployed it...it is running fine for sometime and it is throwing the error like this... Server Error in '/' Application. Could not load file or assembly 'Facebook, Version=4.1.1.0, Culture=neutral, PublicKeyToken=58cb4f2111d1e6de' or one of its dependencies. Access is denied. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.IO.FileLoadException: Could not load file or assembly 'Facebook, Version=4.1.1.0, Culture=neutral, PublicKeyToken=58cb4f2111d1e6de' or one of its dependencies. Access is denied. Source Error: An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below. Assembly Load Trace: The following information can be helpful to determine why the assembly 'Facebook, Version=4.1.1.0, Culture=neutral, PublicKeyToken=58cb4f2111d1e6de' could not be loaded. WRN: Assembly binding logging is turned OFF. To enable assembly bind failure logging, set the registry value [HKLM\Software\Microsoft\Fusion!EnableLog] (DWORD) to 1. Note: There is some performance penalty associated with assembly bind failure logging. To turn this feature off, remove the registry value [HKLM\Software\Microsoft\Fusion!EnableLog]. Stack Trace: [FileLoadException: Could not load file or assembly 'Facebook, Version=4.1.1.0, Culture=neutral, PublicKeyToken=58cb4f2111d1e6de' or one of its dependencies. Access is denied.] Secured_Login.FacebookVerification() +0 System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) +25 System.Web.UI.Control.LoadRecursive() +71 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +3048 Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.0.30319.1 i got this method in pageload protected void Page_Load(object sender, EventArgs e) { FacebookVerification(); } protected void FacebookVerification() { try { FacebookApp fbApp = new FacebookApp(); if (fbApp.Session != null) { dynamic myinfo = fbApp.Get("me"); String firstname = myinfo.first_name; String lastname = myinfo.last_name; lblFBStatus.Text = "you signed in as " + firstname + " " + lastname ; } else { lblFBStatus.Text = "Please sign in with facebook"; } } catch (Exception) { throw; } }

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• XML: When to use attributes instead of child nodes?

  - by Rosarch

  For tree leaves in XML, when is it better to use attributes, and when is it better to use descendant nodes? For example, in the following XML document: <?xml version="1.0" encoding="utf-8" ?> <savedGame> <links> <link rootTagName="zombies" packageName="zombie" /> <link rootTagName="ghosts" packageName="ghost" /> <link rootTagName="players" packageName="player" /> <link rootTagName="trees" packageName="tree" /> </links> <locations> <zombies> <zombie> <positionX>41</positionX> <positionY>100</positionY> </zombie> <zombie> <positionX>55</positionX> <positionY>56</positionY> </zombie> </zombies> <ghosts> <ghost> <positionX>11</positionX> <positionY>90</positionY> </ghost> </ghosts> </locations> </savedGame> The <link> tag has attributes, but it could also be written as: <link> <rootTagName>trees</rootTagName> <packageName>tree</packageName> </link> Similarly, the location tags could be written as: <zombie positionX="55" positionY="56" /> instead of: <zombie> <positionX>55</positionX> <positionY>56</positionY> </zombie> What reasons are there to prefer one over the other? Is it just a stylistic issue? Any performance considerations?

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• The question about the basics of LINQ to SQL

  - by Alex

  I just started learning LINQ to SQL, and so far I'm impressed with the easy of use and good performance. I used to think that when doing LINQ queries like from Customer in DB.Customers where Customer.Age > 30 select Customer LINQ gets all customers from the database ("SELECT * FROM Customers"), moves them to the Customers array and then makes a search in that Array using .NET methods. This is very inefficient, what if there are hundreds of thousands of customers in the database? Making such big SELECT queries would kill the web application. Now after experiencing how actually fast LINQ to SQL is, I start to suspect that when doing that query I just wrote, LINQ somehow converts it to a SQL Query string SELECT * FROM Customers WHERE Age > 30 And only when necessary it will run the query. So my question is: am I right? And when is the query actually run? The reason why I'm asking is not only because I want to understand how it works in order to build good optimized applications, but because I came across the following problem. I have 2 tables, one of them is Books, the other has information on how many books were sold on certain days. My goal is to select books that had at least 50 sales/day in past 10 days. It's done with this simple query: from Book in DB.Books where (from Sale in DB.Sales where Sale.SalesAmount >= 50 && Sale.DateOfSale >= DateTime.Now.AddDays(-10) select Sale.BookID).Contains(Book.ID) select Book The point is, I have to use the checking part in several queries and I decided to create an array with IDs of all popular books: var popularBooksIDs = from Sale in DB.Sales where Sale.SalesAmount >= 50 && Sale.DateOfSale >= DateTime.Now.AddDays(-10) select Sale.BookID; BUT when I try to do the query now: from Book in DB.Books where popularBooksIDs.Contains(Book.ID) select Book It doesn't work! That's why I think that we can't use thins kinds of shortcuts in LINQ to SQL queries, like we can't use them in real SQL. We have to create straightforward queries, am I right?

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• How to convert a 32bpp image to an indexed format?

  - by Ed Swangren

  So here are the details (I am using C# BTW): I receive a 32bpp image (JPEG compressed) from a server. At some point, I would like to use the Palette property of a bitmap to color over-saturated pixels (brightness 240) red. To do so, I need to get the image into an indexed format. I have tried converting the image to a GIF, but I get quality loss. I have tried creating a new bitmap in an index format by these methods: // causes a "Parameter not valid" error Bitmap indexed = new Bitmap(orig.Width, orig.Height, PixelFormat.Indexed) // no error, but the resulting image is black due to information loss I assume Bitmap indexed = new Bitmap(orig.Width, orig.Height, PixelFormat.Format8bppIndexed) I am at a loss now. The data in this image is changed constantly by the user, so I don't want to manually set pixels that have a brightness 240 if I can avoid it. If I can set the palette once when the image is created, my work is done. If I am going about this the wrong way to begin with please let me know. EDIT: Thanks guys, here is some more detail on what I am attempting to accomplish. We are scanning a tissue slide at high resolution (pathology application). I write the interface to the actual scanner. We use a line-scan camera. To test the line rate of the camera, the user scans a very small portion and looks at the image. The image is displayed next to a track bar. When the user moves the track bar (adjusting line rate), I change the overall intensity of the image in an attempt to model what it would look like at the new line rate. I do this using an ImageAttributes and ColorMatrix object currently. When the user adjusts the track bar, I adjust the matrix. This does not give me per pixel information, but the performance is very nice. I could use LockBits and some unsafe code here, but I would rather not rewrite it if possible. When the new image is created, I would like for all pixels with a brightness value of 240 to be colored red. I was thinking that defining a palette for the bitmap up front would be a clean way of doing this.

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• SQL Server 2005 - query with case statement

  - by user329266

  Trying to put a single query together to be used eventually in a SQL Server 2005 report. I need to: Pull in all distinct records for values in the "eventid" column for a time frame - this seems to work. For each eventid referenced above, I need to search for all instances of the same eventid to see if there is another record with TaskName like 'review1%'. Again, this seems to work. This is where things get complicated: For each record where TaskName is like review1, I need to see if another record exists with the same eventid and where TaskName='End'. Utimately, I need a count of how many records have TaskName like 'review1%', and then how many have TaskName like 'review1%' AND TaskName='End'. I would think this could be accomplished by setting a new value for each record, and for the eventid, if a record exists with TaskName='End', set to 1, and if not, set to 0. The query below seems to accomplish item #1 above: SELECT eventid, TimeStamp, TaskName, filepath FROM (SELECT eventid, TimeStamp, filepath, TaskName, ROW_NUMBER() OVER(PARTITION BY eventid ORDER BY TimeStamp DESC) AS seq FROM eventrecords where ((TimeStamp >= '2010-4-1 00:00:00.000') and (TimeStamp <= '2010-4-21 00:00:00.000'))) AS T WHERE seq = 1 order by eventid And the query below seems to accomplish #2: SELECT eventid, TimeStamp, TaskName, filepath FROM (SELECT eventid, TimeStamp, filepath, TaskName, ROW_NUMBER() OVER(PARTITION BY eventid ORDER BY TimeStamp DESC) AS seq FROM eventrecords where ((TimeStamp >= '2010-4-1 00:00:00.000') and (TimeStamp <= '2010-4-21 00:00:00.000')) and TaskName like 'Review1%') AS T WHERE seq = 1 order by eventid This will bring back the eventid's that also have a TaskName='End': SELECT eventid, TimeStamp, TaskName, filepath FROM (SELECT eventid, TimeStamp, filepath, TaskName, ROW_NUMBER() OVER(PARTITION BY eventid ORDER BY TimeStamp DESC) AS seq FROM eventrecords where ((TimeStamp >= '2010-4-1 00:00:00.000') and (TimeStamp <= '2010-4-21 00:00:00.000')) and TaskName like 'Review1%') AS T WHERE seq = 1 and eventid in (Select eventid from eventrecords where TaskName = 'End') order by eventid So I've tried the following to TRY to accomplish #3: SELECT eventid, TimeStamp, TaskName, filepath FROM (SELECT eventid, TimeStamp, filepath, TaskName, ROW_NUMBER() OVER(PARTITION BY eventid ORDER BY TimeStamp DESC) AS seq FROM eventrecords where ((TimeStamp >= '2010-4-1 00:00:00.000') and (TimeStamp <= '2010-4-21 00:00:00.000')) and TaskName like 'Review1%') AS T WHERE seq = 1 and case when (eventid in (Select eventid from eventrecords where TaskName = 'End') then 1 else 0) as bit end order by eventid When I try to run this, I get: "Incorrect syntax near the keyword 'then'." Not sure what I'm doing wrong. Haven't seen any examples anywhere quite like this. I should mention that eventrecords has a primary key, but it doesn't seem to help anything when I include it, and I am not permitted to change the table. (ugh) I've received one suggestion to use a cursor and temporary table, but am not sure how badley that would bog down performance when the report is running. Thanks in advance.

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• SQL Select - adding field to Select is changing the results

  - by nycdan

  I'm stumped by this SQL problem that I suspect will be easy pickings for someone out there. I have a table that contains rows representing several daily lists of ranked items. The relevent fields are as follows: ID, ListID, ItemID, ItemName, ItemRank, Date. I have a query that returns the items that were on a list yesterday but not today (Items Off List) as follows: Select ItemID, ListID, ItemName, convert(varchar(10),MAX(date),101) as date, COUNT(ItemName) as days_on_list From Table Group By ItemID, ListID, ItemName Having Max(date) = DATEADD("d",-1,convert(varchar(10),getdate(),101)) and ListID = 1 Order By ListID, ItemName, COUNT(ItemName) Basically I'm looking for records where the max date is yesterday. It works fine and shows the number of days each item was previously on the list (although not necessarily consecutively, but that's fine for now). The problem is when I try to add ranking to see what yesterday's rank was. I tried the following: Select ItemID, ListID, ItemName, ranking, convert(varchar(10),MAX(date),101) as date, COUNT(ItemName) as days_on_list From Table Group By ItemID, ListID, ItemName, ranking Having Max(date) = DATEADD("d",-1,convert(varchar(10),getdate(),101)) and ListID = 1 Order By ListID, ItemName, ranking, COUNT(ItemName) This returns a great deal more records than the previous query so something isn't right with it. I want the same number of records, but with the ranking included. I can get the rank by doing a self-join with a subquery and getting records where the ItemID occurs yesterday but not today - but then I don't know how to get the Count any more. Appreciation in advance for any help with this. ======== SOLVED ============== Select ItemID, ListID, ItemName, ranking, convert(varchar(10),MAX(date),101) as date, COUNT(ItemName) as days_on_list from Table T Where date = DATEADD("d",-1,convert(varchar(10),getdate(),101)) and ListID = 1 and T.ItemID Not In (select T.ItemID from Table T join Table T2 on T.ItemID = T2.ItemID and T.ListID = T2.ListID where T.date = DATEADD("d",-1,convert(varchar(10),getdate(),101)) and T2.date = convert (varchar(10),getdate(),101) and T.ListID = 1) Group by ItemID, ListID, ItemName, ranking Basically, what I did was create a subquery that finds all items that appear in both days, and finds items that appeared yesterday but are not in the set of items that appeared both days. Then I was able to do the aggregate function and grouping correctly. I would NOT be surprised if this is more convoluted than necessary but I understand it and can modify it as needed and performance doesn't seem to be an issue. Thanks everyone for the assist.

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• Issue with RegConnectRegistry connecting to 64 bit machines

  - by RA

  I'm seeing a weird thing when connecting to the performance registry on 64 bit editions of Windows. The whole program stalls and callstacks becomes unreadable. After a long timeout, the connection attempts aborts and everything goes back to normal. The only solution is to make sure that only one thread at the time queries the remote registry, unless the remote machine is a 32 bit Windows XP, 2003, 2000 , then you can use as many threads as you like. Have anyone a technical explanation why this might be happening ? I've spent 2-3 days searching the web without coming up with anything. Here is a test program, run it first with one thread (connecting to a 64 bit Windows), then remove the comment in tmain and run it with 4 threads. Running it with one thread works as expected, running with 4, returns ERROR_BUSY (dwRet == 170) after stalling for a while. Remember to set a remote machine correctly in RegConnectRegistry before running the program. #define TOTALBYTES 8192 #define BYTEINCREMENT 4096 void PerfmonThread(void *pData) { DWORD BufferSize = TOTALBYTES; DWORD cbData; DWORD dwRet; PPERF_DATA_BLOCK PerfData = (PPERF_DATA_BLOCK) malloc( BufferSize ); cbData = BufferSize; printf("\nRetrieving the data..."); HKEY hKey; DWORD dwAccessRet = RegConnectRegistry(L"REMOTE_MACHINE",HKEY_PERFORMANCE_DATA,&hKey); dwRet = RegQueryValueEx( hKey,L"global",NULL,NULL,(LPBYTE) PerfData, &cbData ); while( dwRet == ERROR_MORE_DATA ) { // Get a buffer that is big enough. BufferSize += BYTEINCREMENT; PerfData = (PPERF_DATA_BLOCK) realloc( PerfData, BufferSize ); cbData = BufferSize; printf("."); dwRet = RegQueryValueEx( hKey,L"global",NULL,NULL,(LPBYTE) PerfData,&cbData ); } if( dwRet == ERROR_SUCCESS ) printf("\n\nFinal buffer size is %d\n", BufferSize); else printf("\nRegQueryValueEx failed (%d)\n", dwRet); RegCloseKey(hKey); } int _tmain(int argc, _TCHAR* argv[]) { _beginthread(PerfmonThread,0,NULL); /* _beginthread(PerfmonThread,0,NULL); _beginthread(PerfmonThread,0,NULL); _beginthread(PerfmonThread,0,NULL); */ while(1) { Sleep(2000); } }

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• stored as array understanding mongoid

  - by Gagan

  Hello frens, This is not a problem, but I just want to know stored as array of Mongoid better. I have following code in my model. class Company include Mongoid::Document include Mongoid::Timestamps references_many :people, :stored_as => :array, :inverse_of => :companies end class Person include Mongoid::Document include Sunspot::Mongoid references_many :companies, :stored_as => :array, :inverse_of => :people end Now in Company object we get person_ids as a result of stored_as array and company_ids in Person object. Now initially I inserted lots of person in company and the ids in person_ids fields is huge. Now I deleted most of person from company down to 8 people. Now I don't get why person_ids fields of Company object storing all the deleted ids of person. My console snapshot is follwing ruby-1.9.2-head Company.first.person_ids = [BSON::ObjectId('4d12d2907adf350695000025'), BSON::ObjectId('4d12d2907adf35069500002c'), BSON::ObjectId('4d12d2907adf350695000035'), BSON::ObjectId('4d12d2907adf35069500003f'), BSON::ObjectId('4d12d2907adf350695000048'), BSON::ObjectId('4d12d2907adf350695000052'), BSON::ObjectId('4d12d2907adf350695000059'), BSON::ObjectId('4d12d2907adf350695000062'), BSON::ObjectId('4d12d4017adf35069500008d'), BSON::ObjectId('4d12d4017adf350695000094'), BSON::ObjectId('4d12d4017adf35069500009d'), BSON::ObjectId('4d12d4017adf3506950000a7'), BSON::ObjectId('4d12d4017adf3506950000b0'), BSON::ObjectId('4d12d4017adf3506950000ba'), BSON::ObjectId('4d12d4017adf3506950000c1'), BSON::ObjectId('4d12d4017adf3506950000ca'), BSON::ObjectId('4d12d48a7adf3506950000f5'), BSON::ObjectId('4d12d48a7adf3506950000fc'), BSON::ObjectId('4d12d48a7adf350695000108'), BSON::ObjectId('4d12d48b7adf350695000115'), BSON::ObjectId('4d12d48b7adf350695000121'), BSON::ObjectId('4d12d48b7adf35069500012e'), BSON::ObjectId('4d12d48b7adf350695000135'), BSON::ObjectId('4d12d48b7adf350695000141'), BSON::ObjectId('4d12d53e7adf35069500016f'), BSON::ObjectId('4d12d53e7adf350695000176'), BSON::ObjectId('4d12d53e7adf350695000182'), BSON::ObjectId('4d12d53e7adf35069500018f'), BSON::ObjectId('4d12d53e7adf35069500019b'), BSON::ObjectId('4d12d53f7adf3506950001a8'), BSON::ObjectId('4d12d53f7adf3506950001af'), BSON::ObjectId('4d12d53f7adf3506950001bb'), BSON::ObjectId('4d12d8587adf3506950001e9'), BSON::ObjectId('4d12d8587adf3506950001f0'), BSON::ObjectId('4d12d8587adf3506950001ff'), BSON::ObjectId('4d12d8597adf35069500020f'), BSON::ObjectId('4d12d8597adf35069500021e'), BSON::ObjectId('4d12d8597adf35069500022e'), BSON::ObjectId('4d12d8597adf350695000235'), BSON::ObjectId('4d12d85a7adf350695000244'), BSON::ObjectId('4d12d9587adf35069500025b'), BSON::ObjectId('4d12db8b7adf35069500026a'), BSON::ObjectId('4d12de6f7adf3509c9000024'), BSON::ObjectId('4d12de6f7adf3509c900002b'), BSON::ObjectId('4d12de6f7adf3509c900003a'), BSON::ObjectId('4d12de707adf3509c900004a'), BSON::ObjectId('4d12de707adf3509c9000059'), BSON::ObjectId('4d12de707adf3509c9000069'), BSON::ObjectId('4d12de707adf3509c9000070'), BSON::ObjectId('4d12de717adf3509c900007f'), BSON::ObjectId('4d12e7f27adf350bd2000009'), BSON::ObjectId('4d12e81f7adf350bd2000015'), BSON::ObjectId('4d12e87f7adf350bd2000024'), BSON::ObjectId('4d12e8b87adf350bd200004c'), BSON::ObjectId('4d12e8b97adf350bd2000053'), BSON::ObjectId('4d12e8b97adf350bd200005c'), BSON::ObjectId('4d12e8b97adf350bd2000066'), BSON::ObjectId('4d12e8b97adf350bd200006f'), BSON::ObjectId('4d12e8b97adf350bd2000079'), BSON::ObjectId('4d12e8ba7adf350bd2000080'), BSON::ObjectId('4d12e8ba7adf350bd2000089'), BSON::ObjectId('4d12ee6b7adf350bd2000198'), BSON::ObjectId('4d12ee6b7adf350bd200019f'), BSON::ObjectId('4d12ee6c7adf350bd20001a5'), BSON::ObjectId('4d12ee6c7adf350bd20001ac'), BSON::ObjectId('4d12ee6c7adf350bd20001b2'), BSON::ObjectId('4d12ee6c7adf350bd20001b9'), BSON::ObjectId('4d12ee6c7adf350bd20001c0'), BSON::ObjectId('4d12ee6c7adf350bd20001c6'), BSON::ObjectId('4d141ca57adf35033e00006e'), BSON::ObjectId('4d141ca57adf35033e000075'), BSON::ObjectId('4d1420aa7adf350705000003'), BSON::ObjectId('4d1420aa7adf35070500000a'), BSON::ObjectId('4d1420f47adf350705000011'), BSON::ObjectId('4d1420f57adf350705000015'), BSON::ObjectId('4d1420f57adf350705000018'), BSON::ObjectId('4d1420f57adf35070500001c'), BSON::ObjectId('4d1420f57adf350705000023'), BSON::ObjectId('4d1420f57adf350705000026'), BSON::ObjectId('4d14215f7adf35070500004b'), BSON::ObjectId('4d14215f7adf350705000052'), BSON::ObjectId('4d14215f7adf350705000055'), BSON::ObjectId('4d14215f7adf350705000059'), BSON::ObjectId('4d14215f7adf35070500005c'), BSON::ObjectId('4d14215f7adf350705000060'), BSON::ObjectId('4d14215f7adf350705000067'), BSON::ObjectId('4d14215f7adf35070500006a')] Company.first.people.collect(&:id) = [BSON::ObjectId('4d14215f7adf35070500004b'), BSON::ObjectId('4d14215f7adf350705000052'), BSON::ObjectId('4d14215f7adf350705000055'), BSON::ObjectId('4d14215f7adf350705000059'), BSON::ObjectId('4d14215f7adf35070500005c'), BSON::ObjectId('4d14215f7adf350705000060'), BSON::ObjectId('4d14215f7adf350705000067'), BSON::ObjectId('4d14215f7adf35070500006a')] Isn't the Company.first.person_ids array be only storing the ids shown by Company.first.people.collect(&:id) It would be helpful if some one tell me when to best use stored_as = :array method. Do stored_as = :array increase querying performance? Thanks

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• Can parser combination be made efficient?

  - by Jon Harrop

  Around 6 years ago, I benchmarked my own parser combinators in OCaml and found that they were ~5× slower than the parser generators on offer at the time. I recently revisited this subject and benchmarked Haskell's Parsec vs a simple hand-rolled precedence climbing parser written in F# and was surprised to find the F# to be 25× faster than the Haskell. Here's the Haskell code I used to read a large mathematical expression from file, parse and evaluate it: import Control.Applicative import Text.Parsec hiding ((<|>)) expr = chainl1 term ((+) <$ char '+' <|> (-) <$ char '-') term = chainl1 fact ((*) <$ char '*' <|> div <$ char '/') fact = read <$> many1 digit <|> char '(' *> expr <* char ')' eval :: String -> Int eval = either (error . show) id . parse expr "" . filter (/= ' ') main :: IO () main = do file <- readFile "expr" putStr $ show $ eval file putStr "\n" and here's my self-contained precedence climbing parser in F#: let rec (|Expr|) (P(f, xs)) = Expr(loop (' ', f, xs)) and shift oop f op (P(g, xs)) = let h, xs = loop (op, g, xs) loop (oop, f h, xs) and loop = function | ' ' as oop, f, ('+' | '-' as op)::P(g, xs) | (' ' | '+' | '-' as oop), f, ('*' | '/' as op)::P(g, xs) | oop, f, ('^' as op)::P(g, xs) -> let h, xs = loop (op, g, xs) let op = match op with | '+' -> (+) | '-' -> (-) | '*' -> (*) | '/' -> (/) | '^' -> pown loop (oop, op f h, xs) | _, f, xs -> f, xs and (|P|) = function | '-'::P(f, xs) -> let f, xs = loop ('~', f, xs) P(-f, xs) | '('::Expr(f, ')'::xs) -> P(f, xs) | c::xs when '0' <= c && c <= '9' -> P(int(string c), xs) My impression is that even state-of-the-art parser combinators waste a lot of time back tracking. Is that correct? If so, is it possible to write parser combinators that generate state machines to obtain competitive performance or is it necessary to use code generation?

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• whats wrong in this LINQ synatx?

  - by Saurabh Kumar

  Hi, I am trying to convert a SQL query to LINQ. Somehow my count(distinct(x)) logic does not seem to be working correctly. The original SQL is quite efficient(or so i think), but the generated SQL is not even returning the correct result. I am trying to fix this LINQ to do what the original SQL is doing, AND in an efficient way as the original query is doing. Help here would be really apreciated as I am stuck here :( SQL which is working and I need to make a comparable LINQ of: SELECT [t1].[PersonID] AS [personid] FROM [dbo].[Code] AS [t0] INNER JOIN [dbo].[phonenumbers] AS [t1] ON [t1].[PhoneCode] = [t0].[Code] INNER JOIN [dbo].[person] ON [t1].[PersonID]= [dbo].[Person].PersonID WHERE ([t0].[codetype] = 'phone') AND ( ([t0].[CodeDescription] = 'Home') AND ([t1].[PhoneNum] = '111') OR ([t0].[CodeDescription] = 'Work') AND ([t1].[PhoneNum] = '222') ) GROUP BY [t1].[PersonID] HAVING COUNT(DISTINCT([t1].[PhoneNum]))=2 The LINQ which I made is approximately as below: var ids = context.Code.Where(predicate); var rs = from r in ids group r by new { r.phonenumbers.person.PersonID} into g let matchcount=g.Select(p => p.phonenumbers.PhoneNum).Distinct().Count() where matchcount ==2 select new { personid = g.Key }; Unfortunately, the above LINQ is NOT generating the correct result, and is actually internally getting generated to the SQL shown below. By the way, this generated query is also reading ALL the rows(about 19592040) around 2 times due to the COUNTS :( Wich is a big performance issue too. Please help/point me to the right direction. Declare @p0 VarChar(10)='phone' Declare @p1 VarChar(10)='Home' Declare @p2 VarChar(10)='111' Declare @p3 VarChar(10)='Work' Declare @p4 VarChar(10)='222' Declare @p5 VarChar(10)='2' SELECT [t9].[PersonID], ( SELECT COUNT(*) FROM ( SELECT DISTINCT [t13].[PhoneNum] FROM [dbo].[Code] AS [t10] INNER JOIN [dbo].[phonenumbers] AS [t11] ON [t11].[PhoneType] = [t10].[Code] INNER JOIN [dbo].[Person] AS [t12] ON [t12].[PersonID] = [t11].[PersonID] INNER JOIN [dbo].[phonenumbers] AS [t13] ON [t13].[PhoneType] = [t10].[Code] WHERE ([t9].[PersonID] = [t12].[PersonID]) AND ([t10].[codetype] = @p0) AND ((([t10].[codetype] = @p1) AND ([t11].[PhoneNum] = @p2)) OR (([t10].[codetype] = @p3) AND ([t11].[PhoneNum] = @p4))) ) AS [t14] ) AS [cnt] FROM ( SELECT [t3].[PersonID], ( SELECT COUNT(*) FROM ( SELECT DISTINCT [t7].[PhoneNum] FROM [dbo].[Code] AS [t4] INNER JOIN [dbo].[phonenumbers] AS [t5] ON [t5].[PhoneType] = [t4].[Code] INNER JOIN [dbo].[Person] AS [t6] ON [t6].[PersonID] = [t5].[PersonID] INNER JOIN [dbo].[phonenumbers] AS [t7] ON [t7].[PhoneType] = [t4].[Code] WHERE ([t3].[PersonID] = [t6].[PersonID]) AND ([t4].[codetype] = @p0) AND ((([t4].[codetype] = @p1) AND ([t5].[PhoneNum] = @p2)) OR (([t4].[codetype] = @p3) AND ([t5].[PhoneNum] = @p4))) ) AS [t8] ) AS [value] FROM ( SELECT [t2].[PersonID] FROM [dbo].[Code] AS [t0] INNER JOIN [dbo].[phonenumbers] AS [t1] ON [t1].[PhoneType] = [t0].[Code] INNER JOIN [dbo].[Person] AS [t2] ON [t2].[PersonID] = [t1].[PersonID] WHERE ([t0].[codetype] = @p0) AND ((([t0].[codetype] = @p1) AND ([t1].[PhoneNum] = @p2)) OR (([t0].[codetype] = @p3) AND ([t1].[PhoneNum] = @p4))) GROUP BY [t2].[PersonID] ) AS [t3] ) AS [t9] WHERE [t9].[value] = @p5 Thanks!

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• Direct show video renderers suck?

  - by Daniel

  So I've been looking into the world of media playback for windows and I've started making a C# Media Player using DirectShow. I started off using the VRM-7 windowed video renderer and it was brilliant except it had a couple of small problems (multi monitors, fullscreen). But after some research I found that it's deprecated and I should be using VRM9. So I changed it to use VRM9 windowless then found out that was an old post rofl _< so finally I'm using Vista/Win7 (or XP .net 3) Enhanced Video Renderer (EVR) which is apparently the most up to date Microsoft video renderer and has all the flashy performance/quality things added to it. (tbh I haven't noticed any difference but maybe I need a blue-ray or HQ video to notice it). With using EVR everything is working fine except resizing the video. Its really laggy/choppy/teary and problem something to do with its frame queueing mechanism. To demonstrate my problem open up windows media player classic. View - Options - Playback - output Chose the "EVR" DirectShow Video renderer Now restart wmp class and play a video, while it's playing click and drag a corner to resize it. You'll notice its horribly laggy. This is the exact same problem i am having. But if you chose "EVR Custom Pres. *" or EVR Sync *" resizing works beautifully! So i tried googling around for anything about EVR resizing issues and how to fix it but i couldn't believe how little i could find. I'm guessing "Custom Pres." stands for "Custom Presenter" which sounds like they made their own. Also you'll notice on the right hand size when you swap between EVR and the other EVR's the Resizer drop down on the right greys out. So basically I wan't to know how I can fix this retarded resizing problem and is there any decent documentation out there? There is a fair bit for VMR7/9 but not much for EVR. I downloaded the DirectX SDK which apparently has samples but it was a waste of 500mb of bandwidth as it had nothing relevant. Perhaps there is some way to force it not queueing up frames if that is the problem? If you want code say the word and I'll paste some in. But it's really quite simple and nothing much happens, i'm convinced it's a problem with the EVR renderer. EDIT: Oh and one other thing, what does VLC use? If you go into vlc options and change the renderer to anything but default, they all suck. So is it using VMR7? Or its own?

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• DirectShow EVR resizing window problem

  - by Daniel

  So I've been looking into the world of media playback for windows and I've started making a C# Media Player using DirectShow. I started off using the VRM-7 windowed video renderer and it was brilliant except it had a couple of small problems (multi monitors, fullscreen). But after some research I found that it's deprecated and I should be using VRM9. So I changed it to use VRM9 windowless then found out that was an old post rofl _< so finally I'm using Vista/Win7 (or XP .net 3) Enhanced Video Renderer (EVR) which is apparently the most up to date Microsoft video renderer and has all the flashy performance/quality things added to it. (tbh I haven't noticed any difference but maybe I need a blue-ray or HQ video to notice it). With using EVR everything is working fine except resizing the video. Its really laggy/choppy/teary and probably something to do with its frame queueing mechanism. To demonstrate my problem open up windows media player classic. View - Options - Playback - output Chose the "EVR" DirectShow Video renderer Now restart wmp class and play a video, while it's playing click and drag a corner to resize it. You'll notice its horribly laggy. This is the exact same problem i am having. But if you chose "EVR Custom Pres. *" or EVR Sync *" resizing works beautifully! So i tried googling around for anything about EVR resizing issues and how to fix it but i couldn't believe how little i could find. I'm guessing "Custom Pres." stands for "Custom Presenter" which sounds like they made their own. Also you'll notice on the right hand size when you swap between EVR and the other EVR's the Resizer drop down on the right greys out. So basically I wan't to know how I can fix this retarded resizing problem and is there any decent documentation out there? There is a fair bit for VMR7/9 but not much for EVR. I downloaded the DirectX SDK which apparently has samples but it was a waste of 500mb of bandwidth as it had nothing relevant. Perhaps there is some way to force it not queueing up frames if that is the problem? If you want code say the word and I'll paste some in. But it's really quite simple and nothing much happens, i'm convinced it's a problem with the EVR renderer. EDIT: Oh and one other thing, what does VLC use? If you go into vlc options and change the renderer to anything but default, they all suck. So is it using VMR7? Or its own?

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• Do Websites need Local Databases Anymore?

  - by viatropos

  If there's a better place to ask this, please let me know. Every time I build a new website/blog/shopping-cart/etc., I keep trying to do the following: Extract out common functionality into reusable code (Rubygems and jQuery plugins mostly) If possible, convert that gem into a small service so I never have to deal with a database for the objects involved (by service, I mean something lean and mean, usually built with the Sinatra Web Framework with a few core models). My assumption is, if I can remove dependencies on local databases, that will make it easier and more scalable in the long run (scalable in terms of reusability and manageability, not necessarily database/performance). I'm not sure if that's a good or bad assumption yet. What do you think? I've made this assumption because of the following reason: Most serious database/model functionality has been built on the internet somewhere. Just to name a few: Social Network API: Facebook Messaging API: Twitter Mailing API: Google Event API: Eventbrite Shopping API: Shopify Comment API: Disqus Form API: Wufoo Image API: Picasa Video API: Youtube ... Each of those things are fairly complicated to build from scratch and to make as optimized, simple, and easy to use as those companies have made them. So if I build an app that shows pictures (picasa) on an Event page (eventbrite), and you can see who joined the event (facebook events), and send them emails (google apps api), and have them fill out monthly surveys (wufoo), and watch a video when they're done (youtube), all integrated into a custom, easy to use website, and I can do that without ever creating a local database, is that a good thing? I ask because there's two things missing from the puzzle that keep forcing me to create that local database: Post API RESTful/Pretty Url API While there's plenty of Blogging systems and APIs for them, there is no one place where you can just write content and have it part of some massive thing. For every app, I have to use code for creating pretty/restful urls, and that saves posts. But it seems like that should be a service! Question is, is that what the website is? ...That place to integrate the worlds services for my specific cause... and, sigh, to store posts that only my site has access to. Will everyone always need "their own blog"? Why not just have a profile and write lots of content on an established platform like StackOverflow or Facebook? ... That way I can write apps entirely without a database and know that I'm doing it right. Note: Of course at some point you'd need a database, if you were doing something unique or new. But for the case where you're just rewiring information or creating things like videos, events, and products, is it really necessary anymore??

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• How can I limit the cache used by copying so there is still memory available for other cache?

  - by Peter

  Basic situation: I am copying some NTFS disks in openSuSE. Each one is 2TB. When I do this, the system runs slow. My guesses: I believe it is likely due to caching. Linux decides to discard useful cache (eg. kde4 bloat, virtual machine disks, LibreOffice binaries, Thunderbird binaries, etc.) and instead fill all available memory (24 GB total) with stuff from the copying disks, which will be read only once, then written and never used again. So then any time I use these apps (or kde4), the disk needs to be read again, and reading the bloat off the disk again makes things freeze/hiccup. Due to the cache being gone and the fact that these bloated applications need lots of cache, this makes the system horribly slow. Since it is USB,the disk and disk controller are not the bottleneck, so using ionice does not make it faster. I believe it is the cache rather than just the motherboard going too slow, because if I stop everything copying, it still runs choppy for a while until it recaches everything. And if I restart the copying, it takes a minute before it is choppy again. But also, I can limit it to around 40 MB/s, and it runs faster again (not because it has the right things cached, but because the motherboard busses have lots of extra bandwidth for the system disks). I can fully accept a performance loss from my motherboard's IO capability being completely consumed (which is 100% used, meaning 0% wasted power which makes me happy), but I can't accept that this caching mechanism performs so terribly in this specific use case. # free total used free shared buffers cached Mem: 24731556 24531876 199680 0 8834056 12998916 -/+ buffers/cache: 2698904 22032652 Swap: 4194300 24764 4169536 I also tried the same thing on Ubuntu, which causes a total system hang instead. ;) And to clarify, I am not asking how to leave memory free for the "system", but for "cache". I know that cache memory is automatically given back to the system when needed, but my problem is that it is not reserved for caching of specific things. Question: Is there some way to tell these copy operations to limit memory usage so some important things remain cached, and therefore any slowdowns are a result of normal disk usage and not rereading the same commonly used files? For example, is there a setting of max memory per process/user/file system allowed to be used as cache/buffers?

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• Silverlight? WPF? or Windows Form?

  - by Amit

  After Silverlight 4.0 has been released with new WPF, I am kind of confused with these technologies: Silverlight? WPF? Windows Form? The main motive that we want to achieve for BIG business project is following: Performance Security And platform independent** If I consider all above three points then only Silverlight is the option as I don’t want people buying emulator on MacOS for WPF or Windows Form. Now how good the Silverlight is for Business applications, I was completely against when Silverlight 2.0 was in the market but now it is Silverlight 4.0 and they have provided many new features (but still basics) that is required in any challenging business applications. Comparing Silverlight and WPF -* Silverlight and WPF are very new technology and if I'd to compare from these two then I'd prefer WPF because it can be considered stable and mature. But it is not same as Windows Form. -* If I go with Silverlight then I am sure about keep updating to the latest version of Silverlight. I remembered when we were developing software for version 2.0 then we'd to create our own framework with dynamic loading DLL, and then Navigation concept. But everything was got changed once Silverlight 3.0 came. I don't want this to be happening with this new product. -* If we go with WPF then we don't get the platform independence. Now, why not we just focus on making WPF and then move to Silverlght. As someone (Tim?) from Microsoft has said that the idea is to make Silverlight as close as WPF. But if that is the case then why XAML structure is different; I will not be convinced with by saying that .Net framework for SL is too small.. well the difference is coming from the namespace ? I was searching on this subject and found "Microsoft WPF-Silverlight Comparison Whitepaper v1.1.pdf". This guide is very good that gives you ins-outs about how can we build common apps that runs on both. But again, it is comparing Silverlight 2 and not 4. I am sure many architect/ developers/ project managers must be facing similar kind of questions in their premises and wants to initiate this discussion, if it has not been :). We've still got 2 weeks to make this decision, so I'm expecting everyone to participate, gurus?

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• Can my loop be optimized any more? (C++)

  - by Sagekilla

  Below is one of my inner loops that's run several thousand times, with input sizes of 20 - 1000 or more. Is there anything I can do to help squeeze any more performance out of this? I'm not looking to move this code to something like using tree codes (Barnes-Hut), but towards optimizing the actual calculations happening inside, since the same calculations occur in the Barnes-Hut algorithm. Any help is appreciated! typedef double real; struct Particle { Vector pos, vel, acc, jerk; Vector oldPos, oldVel, oldAcc, oldJerk; real mass; }; class Vector { private: real vec[3]; public: // Operators defined here }; real Gravity::interact(Particle *p, size_t numParticles) { PROFILE_FUNC(); real tau_q = 1e300; for (size_t i = 0; i < numParticles; i++) { p[i].jerk = 0; p[i].acc = 0; } for (size_t i = 0; i < numParticles; i++) { for (size_t j = i+1; j < numParticles; j++) { Vector r = p[j].pos - p[i].pos; Vector v = p[j].vel - p[i].vel; real r2 = lengthsq(r); real v2 = lengthsq(v); // Calculate inverse of |r|^3 real r3i = Constants::G * pow(r2, -1.5); // da = r / |r|^3 // dj = (v / |r|^3 - 3 * (r . v) * r / |r|^5 Vector da = r * r3i; Vector dj = (v - r * (3 * dot(r, v) / r2)) * r3i; // Calculate new acceleration and jerk p[i].acc += da * p[j].mass; p[i].jerk += dj * p[j].mass; p[j].acc -= da * p[i].mass; p[j].jerk -= dj * p[i].mass; // Collision estimation // Metric 1) tau = |r|^2 / |a(j) - a(i)| // Metric 2) tau = |r|^4 / |v|^4 real mij = p[i].mass + p[j].mass; real tau_est_q1 = r2 / (lengthsq(da) * mij * mij); real tau_est_q2 = (r2*r2) / (v2*v2); if (tau_est_q1 < tau_q) tau_q = tau_est_q1; if (tau_est_q2 < tau_q) tau_q = tau_est_q2; } } return sqrt(sqrt(tau_q)); }

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• Excel string manipulation to check data consistency

  - by chefsmart

  Background information: - There are nearly 7000 individuals and there is data about their performances in one, two or three tests. Every individual has taken the 1st test (let's call it Test M). Some of those who have taken Test M have also taken Test I, and some of those who have taken Test I have also taken Test B. For the first two tests (M and I), students can score grades I, II, or III. Depending on the grades they are awarded points -- 3 for grade I, 2 for II, 1 for III. The last Test B is just a pass or a fail result with no grades. Those passing this test get 1 point, with no points for failure. (Well actually, grades are awarded, but all grades are given a common 1 point). An amateur has entered data to represent these students and their grades in an Excel file. Problem is, this person has done the worst thing possible - he has developed his own notation and entered all test information in a single cell --- and made my life hell. The file originally had two text columns, one for individual's id, and the second for test info, if one could call it that. It's horrible, I know, and I am suffering. In the image, if you see "M-II-2 I-III-1" it means the person got grade II in Test M for 2 points and grade III in Test I for 1 point. Some have taken only one test, some two, and some three. When the file came to me for processing and analyzing the performance of students, I sent it back with instructions to insert 3 additional columns with only the grades for the three tests. The file now looks as follows. Columns C and D represent grades I, II, and III using 1,2 and 3 respectively. Column C is for Test M, column D for Test I. Column E says BA (B Achieved!) if the individual has passed Test B. Now that you have the above information, let's get to the problem. I don't trust this and want to check whether data in column B matches with data in columns C,D and E. That is, I want to examine the string in column B and find out whether the figures in columns C,D and E are correct. All help is really appreciated. P.S. - I had exported this to MySQL via ODBC and that is why you are seeing those NULLs. I tried doing this in MySQL too, and really will accept a MySQL or an Excel solution, I don't have a preference. Edit : - See file with sample data

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• Would a Centralized Blogging Service Work?

  - by viatropos

  If there's a better place to ask this, please let me know. Every time I build a new website/blog/shopping-cart/etc., I keep trying to do the following: Extract out common functionality into reusable code (Rubygems and jQuery plugins mostly) If possible, convert that gem into a small service so I never have to deal with a database for the objects involved (by service, I mean something lean and mean, usually built with the Sinatra Web Framework with a few core models. My assumption is, if I can remove dependencies on local databases, that will make it easier and more scalable in the long run (scalable in terms of reusability and manageability, not necessarily database/performance). I'm not sure if that's a good or bad assumption yet. What do you think? I've made this assumption because of the following reason: Most serious database/model functionality has been built on the internet somewhere. Just to name a few: Social Network API: Facebook Messaging API: Twitter Mailing API: Google Event API: Eventbrite Shopping API: Shopify Comment API: Disqus Form API: Wufoo Image API: Picasa Video API: Youtube ... Each of those things are fairly complicated to build from scratch and to make as optimized, simple, and easy to use as those companies have. So if I build an app that shows pictures (picasa) on an Event page (eventbrite), and you can see who joined the event (facebook events), and send them emails (google apps api), and have them fill out monthly surveys (wufoo), and watch a video when they're done (youtube), all integrated into a custom, easy to use website, and I can do that without ever creating a local database, is that a good thing? I ask because there's two things missing from the puzzle that keep forcing me to create that local database: Post API RESTful/Pretty Url API While there's plenty of Blogging systems and APIs for them, there is no one place where you can just write content and have it part of some massive thing. For every app, I have to use code for creating pretty/restful urls, and that saves posts. But it seems like that should be a service! Question is, is that the main point of a website? Will everyone always need "their own blog"? Why not just have a profile and write lots of content on an established platform like StackOverflow or Facebook?

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• Execution Plan Optimization when where clause is removed then added back

  - by nmushov

  I have a stored procedure that uses a table valued function which executes in 9 seconds. If I alter the table valued function and remove the where clause, the stored procedure executes in 3 seconds. If I add the where clause back, the query still executes in 3 seconds. I took a look at the execution plans and it appears that after I remove the where clause, the execution plan includes parallelism and the scan count for 2 of my tables drops for 50000 and 65000 down to 5 and 3. After I add the where clause back, the optimized execution plan still runs unless I run DBCC FREEPROCCACHE. Questions 1. Why would SQL Server start using the optimized execution plan for both queries only when I first remove the where clause? Is there a way to force SQL Server to use this execution plan? Also, this is a paramaterized all-in-one query that uses the (Parameter is null or Parameter) in the where clause, which I believe is bad for performance. RETURNS TABLE AS RETURN ( SELECT TOP (@PageNumber * @PageSize) CASE WHEN @SortOrder = 'Expensive' THEN ROW_NUMBER() OVER (ORDER BY SellingPrice DESC) WHEN @SortOrder = 'Inexpensive' THEN ROW_NUMBER() OVER (ORDER BY SellingPrice ASC) WHEN @SortOrder = 'LowMiles' THEN ROW_NUMBER() OVER (ORDER BY Mileage ASC) WHEN @SortOrder = 'HighMiles' THEN ROW_NUMBER() OVER (ORDER BY Mileage DESC) WHEN @SortOrder = 'Closest' THEN ROW_NUMBER() OVER (ORDER BY P1.Distance ASC) WHEN @SortOrder = 'Newest' THEN ROW_NUMBER() OVER (ORDER BY [Year] DESC) WHEN @SortOrder = 'Oldest' THEN ROW_NUMBER() OVER (ORDER BY [Year] ASC) ELSE ROW_NUMBER() OVER (ORDER BY InventoryID ASC) END as rn, P1.InventoryID, P1.SellingPrice, P1.Distance, P1.Mileage, Count(*) OVER () RESULT_COUNT, dimCarStatus.[year] FROM (SELECT InventoryID, SellingPrice, Zip.Distance, Mileage, ColorKey, CarStatusKey, CarKey FROM facInventory JOIN @ZipCodes Zip ON Zip.DealerKey = facInventory.DealerKey) as P1 JOIN dimColor ON dimColor.ColorKey = P1.ColorKey JOIN dimCarStatus ON dimCarStatus.CarStatusKey = P1.CarStatusKey JOIN dimCar ON dimCar.CarKey = P1.CarKey WHERE (@ExteriorColor is NULL OR dimColor.ExteriorColor like @ExteriorColor) AND (@InteriorColor is NULL OR dimColor.InteriorColor like @InteriorColor) AND (@Condition is NULL OR dimCarStatus.Condition like @Condition) AND (@Year is NULL OR dimCarStatus.[Year] like @Year) AND (@Certified is NULL OR dimCarStatus.Certified like @Certified) AND (@Make is NULL OR dimCar.Make like @Make) AND (@ModelCategory is NULL OR dimCar.ModelCategory like @ModelCategory) AND (@Model is NULL OR dimCar.Model like @Model) AND (@Trim is NULL OR dimCar.Trim like @Trim) AND (@BodyType is NULL OR dimCar.BodyType like @BodyType) AND (@VehicleTypeCode is NULL OR dimCar.VehicleTypeCode like @VehicleTypeCode) AND (@MinPrice is NULL OR P1.SellingPrice >= @MinPrice) AND (@MaxPrice is NULL OR P1.SellingPrice < @MaxPrice) AND (@Mileage is NULL OR P1.Mileage < @Mileage) ORDER BY CASE WHEN @SortOrder = 'Expensive' THEN -SellingPrice WHEN @SortOrder = 'Inexpensive' THEN SellingPrice WHEN @SortOrder = 'LowMiles' THEN Mileage WHEN @SortOrder = 'HighMiles' THEN -Mileage WHEN @SortOrder = 'Closest' THEN P1.Distance WHEN @SortOrder = 'Newest' THEN -[YEAR] WHEN @SortOrder = 'Oldest' THEN [YEAR] ELSE InventoryID END )

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• JPanel components paint-time problem

  - by Tom Brito

  I'm having a problem that when my frame is shown (after a login dialog) the buttons are not on correct position, then in some miliseconds they go to the right position (the center of the panel with border layout). When I make a SSCCE, it works correct, but when I run my whole code I have this fast-miliseconds delay to the buttons to go to the correct place. Unfortunately, I can't post the whole code, but the method that shows the frame is: public void login(JComponent userView) { centerPanel.removeAll(); centerPanel.add(userView); centerPanel.revalidate(); centerPanel.repaint(); frame.setVisible(true); } What would cause this delay to the panel layout? (I'm running everything in the EDT) -- update In my machine, this SSCCE shows the layout problem in 2 of 10 times I run it: import java.awt.BorderLayout; import javax.swing.JButton; import javax.swing.JFrame; import javax.swing.JPanel; import javax.swing.SwingUtilities; public class TEST { public static void main(String[] args) throws Exception { SwingUtilities.invokeAndWait(new Runnable() { @Override public void run() { System.out.println("Debug test..."); JPanel btnPnl = new JPanel(); btnPnl.add(new JButton("TEST")); JFrame f = new JFrame("TEST"); f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); f.getContentPane().setLayout(new BorderLayout()); f.getContentPane().add(btnPnl); f.pack(); f.setSize(800, 600); f.setVisible(true); System.out.println("End debug test!"); } }); } } The button first appers in the up-left, and then it goes to the center. Please, note that I'm understand, not just correct. Is it a java bug? --update OK, so the SSCCE don't show the problem with you that tried till now. Maybe it's my computer performance problem. But this don't answer the question, I still think Java Swing is creating new threads for make the layout behind the scenes.

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