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• Add Source file link to the default ASP.NET Server Error page?

  - by Max Schilling

  Has anyone ever thought to attempt to modify the default ASP.NET Server error page to provide a link BACK to the error source in Visual Studio? Consider the following standard error page in ASP.NET: Server Error in '/myproject' Application. Invalid object name 'usp_DoSomething'. 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.Data.SqlClient.SqlException: Invalid object name 'usp_DoSomething'. Source Error: Line 4323: cmd.CommandText = "usp_DoSomething"; Line 4324: Line 4325: using (var dr = cmd.ExecuteReader()) Line 4326: { Line 4327: if (dr != null) Source File: c:\development\myproject\myproject.components\providers\sql\sqldataprovider.cs Line: 4325 When an error like this is generated, the HTML has the source back to the file the error occurs in and the line number. Has anyone ever written or thought of writing some mechanism to turn the text into a link back to the error in Visual Studio? I've never seen anything that does it, but it just seems like it would be a helluva nice feature and I think about it in the back of my mind every time an error occurs when I have to manually go find it in the source. It would just be nice to be able to click a link to take me straight there. Anyone written any, or know of any solutions for this. I use Chrome or Firefox as my browsers of choice, but I'd even consider using IE again if someone found a plugin that did this. Thanks, Max

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• How to identify multiple identical pairs in two vectors

  - by Sacha Epskamp

  In my graph-package (as in graph theory, nodes connected by edges) I have a vector indicating for each edge the node of origin from, a vector indicating for each edge the node of destination to and a vector indicating the curve of each edge curve. By default I want edges to have a curve of 0 if there is only one edge between two nodes and curve of 0.2 if there are two edges between two nodes. The code that I use now is a for-loop, and it is kinda slow: curve <- rep(0,5) from<-c(1,2,3,3,2) to<-c(2,3,4,2,1) for (i in 1:length(from)) { if (any(from==to[i] & to==from[i])) { curve[i]=0.2 } } So basically I look for each edge (one index in from and one in to) if there is any other pair in from and to that use the same nodes (numbers). What I am looking for are two things: A way to identify if there is any pair of nodes that have two edges between them (so I can omit the loop if not) A way to speed up this loop # EDIT: To make this abit clearer, another example: from <- c(4L, 6L, 7L, 8L, 1L, 9L, 5L, 1L, 2L, 1L, 10L, 2L, 6L, 7L, 10L, 4L, 9L) to <- c(1L, 1L, 1L, 2L, 3L, 3L, 4L, 5L, 6L, 7L, 7L, 8L, 8L, 8L, 8L, 10L, 10L) cbind(from,to) from to [1,] 4 1 [2,] 6 1 [3,] 7 1 [4,] 8 2 [5,] 1 3 [6,] 9 3 [7,] 5 4 [8,] 1 5 [9,] 2 6 [10,] 1 7 [11,] 10 7 [12,] 2 8 [13,] 6 8 [14,] 7 8 [15,] 10 8 [16,] 4 10 [17,] 9 10 In these two vectors, pair 3 is identical to pair 10 (both 1 and 7 in different orders) and pairs 4 and 12 are identical (both 2 and 8). So I would want curve to become: [1,] 0.0 [2,] 0.0 [3,] 0.2 [4,] 0.2 [5,] 0.0 [6,] 0.0 [7,] 0.0 [8,] 0.0 [9,] 0.0 [10,] 0.2 [11,] 0.0 [12,] 0.2 [13,] 0.0 [14,] 0.0 [15,] 0.0 [16,] 0.0 [17,] 0.0 (as I vector, I transposed twice to get row numbers).

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• SELECT SQL Variable - should i avoid using this syntax and always use SET?

  - by Sholom

  Hi All, This may look like a duplicate to here, but it's not. I am trying to get a best practice, not a technical answer (which i already (think) i know). New to SQL Server and trying to form good habits. I found a great explanation of the functional differences between SET @var = and SELECT @var = here: http://vyaskn.tripod.com/differences_between_set_and_select.htm To summarize what each has that the other hasn't (see source for examples): SET: ANSI and portable, recommended by Microsoft. SET @var = (SELECT column_name FROM table_name) fails when the select returns more then one value, eliminating the possibility of unpredictable results. SET @var = (SELECT column_name FROM table_name) will set @var to NULL if that's what SELECT column_name FROM table_name returned, thus never leaving @var at it's prior value. SELECT: Multiple variables can be set in one statement Can return multiple system variables set by the prior DML statement SELECT @var = column_name FROM table_name would set @var to (according to my testing) the last value returned by the select. This could be a feature or a bug. Behavior can be changed with SELECT @j = (SELECT column_name FROM table_name) syntax. Speed. Setting multiple variables with a single SELECT statement as opposed to multiple SET/SELECT statements is much quicker. He has a sample test to prove his point. If you could design a test to prove the otherwise, bring it on! So, what do i do? (Almost) always use SET @var =, using SELECT @var = is messy coding and not standard. OR Use SELECT @var = freely, it could accomplish more for me, unless the code is likely to be ported to another environment. Thanks

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• Organizing development teams

  - by Patrick

  A long time ago, when my company was much smaller, dividing the development work over teams was quite easy: the 'application' team developed the applications-specific logic, often requiring a deep insight of specific industry problems) the 'generic' team developed the parts that were common/generic for all applications (user interface related stuff, database access, low-level Windows stuff, ...) Over the years the boundaries between the teams have become fuzzy: the 'application' teams often write application-specific functionality with a 'generic' part, so instead of asking the 'generic' team to write that part for them, they write it themselves to speed up the developments; then donate it to the 'generic' team the 'generic' team's focus seems to be more 'maintenance oriented'. All of the 'very generic' code has already been written, so no new developments are needed in it, but instead they continuously have to support all the functionality donated by the application teams. All this seems to indicate that it's not a good idea anymore to have this split in teams. Maybe the 'generic' team should evolve into a 'software quality' team (defining and guarding the rules for writing good quality software), or into a 'software deployment' team (defining how software should be deployed, installed, ...). How do you split up the work in different teams if you have different applications? everybody can write generic code and donates it to a central 'generic' team? everybody can write generic code, but nobody 'manages' this generic code (everybody is the owner) generic code is written by a 'generic' team only and the applications have to wait until the 'generic' team delivers the generic part (via a library, via a DLL) there is no overlap in code between the different applications some other way? Notice that thee advantage of having the mix (allowing everybody to write everywhere in the code) is that: code is written in a more flexible way it's easier to debug the code since you can easily step into the 'generic' code in the debugger But the big (and maybe only) disadvantage is that this generic code may become nobody's responsibility if there is no clear team that manages it anymore. What is your vision?

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• Javascript Graph Layout Engine

  - by GJK

  I'm looking for a Javascript library/engine that can do graph layouts. (And when I say layouts, I mean logically position vertices nicely.) The graphs I'm working with are all m-ary trees. M is usually no more than 5 or 6, but it can be greater in some cases. I do have something that I use now, Graphviz's node program, and it works perfectly. The problem is, when running a web app, I have to send a request to the server every time I want a layout. Preferably, I would like something written in Javascript that can be quickly run on the client side. All it needs to do is provide layout information (relative positioning and whatnot). I don't need it to draw to a canvas or use SVG or anything, all I'm interested in is the layout. Library use like jQuery or RaphaelJS is fine by me. I'll work with it. I'm just looking for something to speed things along a little. Also, I'd consider writing my own if I could find a nice description of an algorithm to do the layouts. But I really don't want to spend too much time. I have something that works now, so getting it on the client side is just a bonus, not a necessity.

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• Is programming overrated?

  - by aengine

  [Subjective and intended to be a community wiki] I am sorry for such an offensive question: But here are my arguments Most of the progress in "computing" has came from non-programming sources. i.e. People invented faster microprocessors and better routers and novel memory devices. I dont think on average people are writting more efficient programs than those written 10 years ago. And the newer and popular languages are infact slower than C. though speed is one of the lesser criterias. Most of the progress came from novel paradigms. Web, Internet, Cloud computing and Social networking are novel paradigms and did not involve progress in programming as such. Heck even facebook was written in PHP and not some extreme language. Though it did face scalability issues (same with twitter) but i believe money and better programmers (who came in much later) took care of that. Thus ideating capability trumped programming capability/ Even things like Map-Reduce, Column oriented database and Probablistic algorithms (E.g. bloom filters) came from hardcore Algorithms research, rather than some programming convention. Thus my final point is why programming skill is so overstressed? To point a recent example about how only 10% of programmers can "write code" (binary search) without debugging. Isnt it a bit hypocritical, considering your real successs lies in coming up with better algorithm or a novel feature rather than getting right first time???

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• fastest way to check to see if a certain index in a linq statement is null

  - by tehdoommarine

  Basic Details I have a linq statement that grabs some records from a database and puts them in a System.Linq.Enumerable: var someRecords = someRepoAttachedToDatabase.Where(p=>true); Suppose this grabs tons (25k+) of records, and i need to perform operations on all of them. to speed things up, I have to decided to use paging and perform the operations needed in blocks of 100 instead of all of the records at the same time. The Question The line in question is the line where I count the number of records in the subset to see if we are on the last page; if the number of records in subset is less than the size of paging - then that means there are no more records left. What I would like to know is what is the fastest way to do this? Code in Question int pageSize = 100; bool moreData = true; int currentPage = 1; while (moreData) { var subsetOfRecords = someRecords.Skip((currentPage - 1) * pageSize).Take(pageSize); //this is also a System.Linq.Enumerable if (subsetOfRecords.Count() < pageSize){ moreData = false;} //line in question //do stuff to records in subset currentPage++; } Things I Have Considered subsetOfRecords.Count() < pageSize subsetOfRecords.ElementAt(pageSize - 1) == null (causes out of bounds exception - can catch exception and set moreData to false there) Converting subsetOfRecords to an array (converting someRecords to an array will not work due to the way subsetOfRecords is declared - but I am open to changing it) I'm sure there are plenty of other ideas that I have missed.

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• Error with threads during automatic testing on TeamCity 5

  - by yeyeyerman

  Hello, I'm having some problems executing the tests of the application I'm developing. All the tests execute normally with ReSharper and in NCover. However, the execution of one of these tests in TeamCity is generating an error. This test initializes two objects, the object under test and a simulator of a real object. Both objects will communicate throug a serial link in a representation of the real scenario. ObjectSimulator r_simulator = new ObjectSimulator(...); ObjectDriver r_driver = new ObjectDriver(...); Assert.IsTrue(r_driver.Connect() == ErrorCode.Success); The simulator just do the following in the constructor public class ObjectSimulator { ... public ObjectSimulator() { // serial port configuration m_port = new SerialPort(); m_port.DataReceived += DataReceivedEvent; } ... } The main object has two threads. The main thread of the application and a timer to refresh a watchdog timer in the real object. public ErrorCode Connect() { ... StartSynchroTimer(); Thread.Sleep(4); // to check if the timer is working properly ... } The problem is comming from the Thread.Sleep() call, as when I remove it everything works. It seems like the ObjectSimulator also sleeps and doesn't receive the DataReceived event. How can I resolve this issue?

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• How to detect .NET WPF memory leak or GC long run?

  - by Néstor Sánchez A.

  I have the next very strange situation and problem: .NET 4.0 application for diagram editing (WPF). Runs ok in my PC: 8GM RAM, 3.0GHz, i7 quad-core. While creating objects (mostly diagram nodes and connectors, plus all the undo/redo information) the TaskManager show, as expected, some memory usage "jumps" (up and down). These mem-usage "jumps" also remains executing AFTER user interaction ended. Maybe this is the GC cleaning/regorganizing memory? To see what is going on, I've used the Ants mem profiler, but somewhat it prevents those "jumps" to happen after user interaction. PROBLEM: It Freezes/Hangs after seconds or minutes of usage in some slow/weak laptos/netbooks of my beta testers (under 2GHz of speed and under 2GB of RAM). I was thinking of a memory leak, but... EDIT: Also, there is the case that the memory usage grows and grows until collapse (only in slow machines). In a Windows XP Mode machine (VM in Win 7) with only 512MB of RAM Assigned it works fine without mem-usage "jumps" after user interaction (no GC cleaning?!). So, I really have a big trouble because I cannot reproduce the error, only see these strange behaviour (mem jumps), and the tool supposed to show me what is happening is hiding the problem (like the "observer's paradox"). Any ideas on what's happening and how to solve it?

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• Trouble with go tour crawler exercise

  - by David Mason

  I'm going through the go tour and I feel like I have a pretty good understanding of the language except for concurrency. On slide 71 there is an exercise that asks the reader to parallelize a web crawler (and to make it not cover repeats but I haven't gotten there yet.) Here is what I have so far: func Crawl(url string, depth int, fetcher Fetcher, ch chan string) { if depth <= 0 { return } body, urls, err := fetcher.Fetch(url) if err != nil { ch <- fmt.Sprintln(err) return } ch <- fmt.Sprintf("found: %s %q\n", url, body) for _, u := range urls { go Crawl(u, depth-1, fetcher, ch) } } func main() { ch := make(chan string, 100) go Crawl("http://golang.org/", 4, fetcher, ch) for i := range ch { fmt.Println(i) } } The issue I have is where to put the close(ch) call. If I put a defer close(ch) somewhere in the Crawl method, then I end up writing to a closed channel in one of the spawned goroutines, since the method will finish execution before the spawned goroutines do. If I omit the call to close(ch), as is shown in my example code, the program deadlocks after all the goroutines finish executing but the main thread is still waiting on the channel in the for loop since the channel was never closed.

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• How to execute python script on the BaseHTTPSERVER created by python?

  - by user1731699

  I have simply created a python server with : python -m SimpleHTTPServer I had a .htaccess (I don't know if it is usefull with python server) with: AddHandler cgi-script .py Options +ExecCGI Now I am writing a simple python script : #!/usr/bin/python import cgitb cgitb.enable() print 'Content-type: text/html' print ''' <html> <head> <title>My website</title> </head> <body> <p>Here I am</p> </body> </html> ''' I make test.py (name of my script) an executed file with: chmod +x test.py I am launching in firefox with this addres: (http : //) 0.0.0.0:8000/test.py Problem, the script is not executed... I see the code in the web page... And server error is: localhost - - [25/Oct/2012 10:47:12] "GET / HTTP/1.1" 200 - localhost - - [25/Oct/2012 10:47:13] code 404, message File not found localhost - - [25/Oct/2012 10:47:13] "GET /favicon.ico HTTP/1.1" 404 - How can I manage the execution of python code simply? Is it possible to write in a python server to execute the python script like with something like that: import BaseHTTPServer import CGIHTTPServer httpd = BaseHTTPServer.HTTPServer(\ ('localhost', 8123), \ CGIHTTPServer.CGIHTTPRequestHandler) ###  here some code to say, hey please execute python script on the webserver... ;-) httpd.serve_forever() Or something else...

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• Help regarding multi-threading in MFC,please help me firends!

  - by kiddo

  Hello all,in my application there is a small part of function,in which it will read files to get some information,the number of filecount would be utleast 50,So I thought of implementing threading.Say if the user is giving 50 files,I wanted to separate it as 5 *10, 5 thread should be created,so that each thread can handle 10 files which can speed up the process.And also from the below code you can see that some variables are common.I read some articles about threading and I am aware that only one thread should access a variable/contorl at a me(CCriticalStiuation can be used for that).For me as a beginner,I am finding hard to imlplement what I have learned about threading.Somebody please give me some idea with code shown below..thanks in advance file read function:// void CMyClass::GetWorkFilesInfo(CStringArray& dataFilesArray,CString* dataFilesB, int* check,DWORD noOfFiles,LPWSTR path) { CString cFilePath; int cIndex =0; int exceptionInd = 0; wchar_t** filesForWork = new wchar_t*[noOfFiles]; int tempCheck; int localIndex =0; for(int index = 0;index < noOfFiles; index++) { tempCheck = *(check + index); if(tempCheck == NOCHECKBOX) { *(filesForWork+cIndex) = new TCHAR[MAX_PATH]; wcscpy(*(filesForWork+cIndex),*(dataFilesB +index)); cIndex++; } else//CHECKED or UNCHECKED { dataFilesArray.Add(*(dataFilesB+index)); *(check + localIndex) = *(check + index); localIndex++; } } WorkFiles(&cFilePath,dataFilesArray,filesForWork, path, cIndex); dataFilesArray.Add(cFilePath); *(check + localIndex) = CHECKED; }

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• Why does reusing arrays increase performance so significantly in c#?

  - by Willem

  In my code, I perform a large number of tasks, each requiring a large array of memory to temporarily store data. I have about 500 tasks. At the beginning of each task, I allocate memory for an array : double[] tempDoubleArray = new double[M]; M is a large number depending on the precise task, typically around 2000000. Now, I do some complex calculations to fill the array, and in the end I use the array to determine the result of this task. After that, the tempDoubleArray goes out of scope. Profiling reveals that the calls to construct the arrays are time consuming. So, I decide to try and reuse the array, by making it static and reusing it. It requires some additional juggling to figure out the minimum size of the array, requiring an extra pass through all tasks, but it works. Now, the program is much faster (from 80 sec to 22 sec for execution of all tasks). double[] tempDoubleArray = staticDoubleArray; However, I'm a bit in the dark of why precisely this works so well. Id say that in the original code, when the tempDoubleArray goes out of scope, it can be collected, so allocating a new array should not be that hard right? I ask this because understanding why it works might help me figuring out other ways to achieve the same effect, and because I would like to know in what cases allocation gives performance issues.

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• segmentation fault while using format string to scan input

  - by Aman Deep Gautam

  consider the code and its result: while ((row = mysql_fetch_row (table_info)) != NULL) { answer='\0'; printf ( "%s: ", row[0] ); scanf ( "%c", &answer ); getchar(); if ( answer == 'y') { printf ( "*****\n" ); table_name[index] = malloc ( strlen(row[0]) + 1 ); printf ( "*****\n" ); memcpy ( &table_name[index], &row[0], strlen(row[0]) + 1 ); } printf ( "finally inserted: %s \n", table_name[index]); } The result on execution: 1_time_access: y ***** ***** finally inserted: 1_time_access 2_time_access: y ***** ***** finally inserted: 2_time_access 39_time_access: y ***** ***** finally inserted: 39_time_access Explanation of result: row[0] has value 1_time_access, 2_time_access, 39_time_access. Now Consider a better way of doing it which is using a format string to escape the \n. I run the following code but it gives segentation fault, I cannot understand why. Code: while ((row = mysql_fetch_row (table_info)) != NULL) { answer='\0'; printf ( "%s: ", row[0] ); scanf ( "%[^\n]%*c", &answer ); if ( answer == 'y') { printf ( "*****\n" ); fflush(stdout); table_name[index] = malloc ( strlen(row[0]) + 1 ); printf ( "*****\n" ); fflush(stdout); memcpy ( &table_name[index], &row[0], strlen(row[0]) + 1 ); } printf ( "finally inserted: %s \n", table_name[index]); fflush(stdout); } Result: 1_time_access: y ***** ./set-env.sh: line 17: 15263 Segmentation fault (core dumped) ./exec dataset_one (do not worry about set-env.sh, it is the script running th program.) I canot understand why this is happening.

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• Determining Best Table Structure for MySQL Performance

  - by Joe Majewski

  I'm working on a browser-based RPG for one of my websites, and right now I'm trying to determine the best way to organize my SQL tables for performance and maintenance. Here's my question: Does the number of columns in an SQL table affect the speed in which it can be queried? I am not a newbie when it comes to PHP or MySQL. I used to develop things with the common goal of getting them to work, but I've recently advanced to the stage where a functional program is not good enough unless it's fast and reliable. Anyways, right now I have a members table that has around 15 columns. It contains information such as the player's username, password, email, logins, page views, etcetera. It doesn't contain any information on the player's progress in the game, however. If I added columns for things such as army size, gold, turns, and whatnot, then it could easily rise to around 40 or 50 total columns. Oh, and my database structure IS normalized. Will a table with 50 columns that gets constantly queried be a bad idea? Should I split it into two tables; one for the user's general information and one for the user's game statistics? I know I could check the query time myself, but I haven't actually created the tables yet and I think I'd be better off with some professional advice on this important decision for my game. Thank you for your time! :)

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• Is it possible to cache all the data in a SQL Server CE database using LinqToSql?

  - by DanM

  I'm using LinqToSql to query a small, simple SQL Server CE database. I've noticed that any operations involving sub-properties are disappointingly slow. For example, if I have a Customer table that is referenced by an Order table, LinqToSql will automatically create an EntitySet<Order> property. This is a nice convenience, allowing me to do things like Customer.Order.Where(o => o.ProductName = "Stopwatch"), but for some reason, SQL Server CE hangs up pretty bad when I try to do stuff like this. One of my queries, which isn't really that complicated takes 3-4 seconds to complete. I can get the speed up to acceptable, even fast, if I just grab the two tables individually and convert them to List<Customer> and List<Order>, then join then manually with my own query, but this is throwing out a lot of what makes LinqToSql so appealing. So, I'm wondering if I can somehow get the whole database into RAM and just query that way, then occasionally save it. Is this possible? How? If not, is there anything else I can do to boost the performance besides resorting to doing all the joins manually? Note: My database in its initial state is about 250K and I don't expect it to grow to more than 1-2Mb. So, loading the data into RAM certainly wouldn't be a problem from a memory point of view. Update Here are the table definitions for the example I used in my question: create table Order ( Id int identity(1, 1) primary key, ProductName ntext null ) create table Customer ( Id int identity(1, 1) primary key, OrderId int null references Order (Id) )

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• How can I compare the performance of log() and fp division in C++?

  - by Ventzi Zhechev

  Hi, I’m using a log-based class in C++ to store very small floating-point values (as the values otherwise go beyond the scope of double). As I’m performing a large number of multiplications, this has the added benefit of converting the multiplications to sums. However, at a certain point in my algorithm, I need to divide a standard double value by an integer value and than do a *= to a log-based value. I have overloaded the *= operator for my log-based class and the right-hand side value is first converted to a log-based value by running log() and than added to the left-hand side value. Thus the operations actually performed are floating-point division, log() and floating-point summation. My question whether it would be faster to first convert the denominator to a log-based value, which would replace the floating-point division with floating-point subtraction, yielding the following chain of operations: twice log(), floating-point subtraction, floating-point summation. In the end, this boils down to whether floating-point division is faster or slower than log(). I suspect that a common answer would be that this is compiler and architecture dependent, so I’ll say that I use gcc 4.2 from Apple on darwin 10.3.0. Still, I hope to get an answer with a general remark on the speed of these two operators and/or an idea on how to measure the difference myself, as there might be more going on here, e.g. executing the constructors that do the type conversion etc. Cheers!

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• C++: Declare static variable in function argument list

  - by MDC

  Is there any way at all in C++ to declare a static variable while passing it to a function? I'm looking to use a macro to expand to the expression passed to the function. The expression needs to declare and initialize a static variable on that particular line (based on the filename and line number using FILE and LINE). int foo(int b) { int c = b + 2; return c; } int main() { int a = 3; a = foo(static int h = 2); //<---- see this! cout << a; return 0; } The problem I'm trying to solve is getting the filename and line number with the FILE and LINE macros provided by the preprocessor, but then creating a lookup table with integer keys leading to the FILE, LINE pairs. For example, the key 89 may map to file foo.cpp, line 20. To get this to work, I'm trying to use local static variables, so that they are initialized only once per line execution. The static variable will be initialized by calling a function that calculates the integer key and adds an entry to the lookup table if it is not there. Right now the program uses a message class to send exception information. I'm writing a macro to wrap this class into a new class: WRAPPER_MACRO(old_class_object) will expand to NewClass(old_class_object, key_value). If I add the static variable declaration as a second line right before this, it should work. The problem is that in most places in the code, the old class object is passed as an argument to a function. So the problem becomes declaring and initializing the static variable somehow with the macro, while keeping the existing function calls.

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• If I cast an IQueryable as an IEnumerable then call a Linq extension method, which implementation gets called?

  - by James Morcom

  Considering the following code: IQueryable<T> queryable; // something to instantiate queryable var enumerable = (IEnumerable<T>) queryable; var filtered = enumerable.Where(i => i > 3); In the final line, which extension method gets called? Is it IEnumerable<T>.Where(...)? Or will IQueryable<T>.Where(...) be called because the actual implementation is still obviously a queryable? Presumably the ideal would be for the IQueryable version to be called, in the same way that normal polymorphism will always use the more specific override. In Visual Studio though when I right-click on the Where method and "Go to Definition" I'm taken to the IEnumerable version, which kind of makes sense from a visual point-of-view. My main concern is that if somewhere in my app I use Linq to NHibernate to get a Queryable, but I pass it around using an interface that uses the more general IEnumerable signature, I'll lose the wonders of deferred database execution!

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• C++ and its type system: How to deal with data with multiple types?

  - by sub

  "Introduction" I'm relatively new to C++. I went through all the basic stuff and managed to build 2-3 simple interpreters for my programming languages. The first thing that gave and still gives me a headache: Implementing the type system of my language in C++ Think of that: Ruby, Python, PHP and Co. have a lot of built-in types which obviously are implemented in C. So what I first tried was to make it possible to give a value in my language three possible types: Int, String and Nil. I came up with this: enum ValueType { Int, String, Nil }; class Value { public: ValueType type; int intVal; string stringVal; }; Yeah, wow, I know. It was extremely slow to pass this class around as the string allocator had to be called all the time. Next time I've tried something similar to this: enum ValueType { Int, String, Nil }; extern string stringTable[255]; class Value { public: ValueType type; int index; }; I would store all strings in stringTable and write their position to index. If the type of Value was Int, I just stored the integer in index, it wouldn't make sense at all using an int index to access another int, or? Anyways, the above gave me a headache too. After some time, accessing the string from the table here, referencing it there and copying it over there grew over my head - I lost control. I had to put the interpreter draft down. Now: Okay, so C and C++ are statically typed. How do the main implementations of the languages mentioned above handle the different types in their programs (fixnums, bignums, nums, strings, arrays, resources,...)? What should I do to get maximum speed with many different available types? How do the solutions compare to my simplified versions above?

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• rc.local on ubuntu on ec2 will not work

  - by Tampa

  Below are the contents of my rc.local file. When I run sudo /etc/rc.local it works fine. When I boot up and instance. I expect monit to be installed but it is not. I am at a total loss. I usually use rc.local but this is rather confunsing. #!/bin/sh -e # # rc.local # # This script is executed at the end of each multiuser runlevel. # Make sure that the script will "exit 0" on success or any other # value on error. # # In order to enable or disable this script just change the execution # bits. # # By default this script does nothing. apt-get -y install monit /etc/init.d/monit stop cd /home/ubuntu/workspace/rtbopsConfig/ git fetch git checkout origin/master rtb_ec2_boot/ec2_boot.py git checkout origin/master config/ cp /home/ubuntu/workspace/rtbopsConfig/config/monit/redis/monitrc /etc/monit/ /usr/bin/python /home/ubuntu/workspace/rtbopsConfig/rtb_ec2_boot/ec2_boot.py >> /home/ubuntu/workspace/ec2_boot.txt 2>&1 /etc/init.d/monit start chkconfig monit on exit 0

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• Java JRE vs GCJ

  - by Martijn Courteaux

  Hi, I have this results from a speed test I wrote in Java: Java real 0m20.626s user 0m20.257s sys 0m0.244s GCJ real 3m10.567s user 3m5.168s sys 0m0.676s So, what is the but of GCJ then? With this results I'm sure I'm not going to compile it with GCJ! I tested this on Linux, are the results in Windows maybe better than that? This was the code from the application: public static void main(String[] args) { String str = ""; System.out.println("Start!!!"); for (long i = 0; i < 5000000L; i++) { Math.sqrt((double) i); Math.pow((double) i, 2.56); long j = i * 745L; String string = new String(String.valueOf(i)); string = string.concat(" kaka pipi"); // "Kaka pipi" is a kind of childly call in Dutch. string = new String(string.toUpperCase()); if (i % 300 == 0) { str = ""; } else { str += Long.toHexString(i); } } System.out.println("Stop!!!"); }

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• Looking for a good C++/.net book

  - by Michael Minerva

  I have recently started to feel that I need to greatly improve my C++ skills especially in the realm of .net. I graduated from a good four year university with a degree in computer science about 9 months ago and I have since been doing full time contract work for a small software company in my local area. Most of my work has been done using Java/lisp/cocoa/XML and before that most of my programming in my senior year was in java/C#. I did a decent amount of C++ in my Sophomore year and in my free time before that but I feel that my general knowledge of C++/.net is very lacking for the opportunities that are now coming my way. Can anyone recommend a good book that could help me get up too speed? I feel I do not need a very basic introduction to C++ but something that covers the fundamentals of .net would be good for me. So basically what I need is a book or books that would be good for a .net novice and a C++ developer who is just beyond novice. Also, a book that would help bein an interview by giving me a conversional understanding of C++ would be great. Thanks a lot!.

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• How do I know when to increase or decrease angle to get a specific angle?

  - by Thomas

  Hi. I am programming a game and I have come to a very hard spot. Basically I have a circle and I have 2 angles on this circle. Angle 1 (A) is a point I want angle 2 (B) to go to. During my game every frame I need to check weither or not to increase or decrease my angle value by a certain amount (speed) to eventually reach the first angle. My question is how do I do this? I tried doing this but I don't seem to be doing it right. bool increase = false; float B = [self radiansToDegrees:tankAngle]; float A = [self radiansToDegrees:tankDestinationAngle]; float newAngle = B; if(B < A) { float C = B - (360 - A); float D = A - B; if(C < D) increase = false; else increase = true; } else if(B A) { float C = B - A; float D = A - (360 - B); if(C < D) increase = false; else increase = true; } if(increase) { newAngle += 1.0; } else { newAngle -= 1.0; } if(newAngle 360.0) { newAngle = 0 + (newAngle - 360.0); } else if(newAngle < 0.0) { newAngle = 360 + newAngle; } if(newAngle == 0) newAngle = 360; newAngle = [self degreesToRadians:newAngle]; [self setTanksProperPositionRotation:newAngle]; The basic effect I am trying to achieve is when the user makes a new point, which would be angle 1, angle 2 would move towards angle 1 choosing the fastest direction. I think I have spent around 4 hours trying to figure this out.

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• I need to make a multithreading program (python)

  - by Andreawu98

  import multiprocessing import time from itertools import product out_file = open("test.txt", 'w') P = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p','q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',] N = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] M = ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'] c = int(input("Insert the number of digits you want: ")) n = int(input("If you need number press 1: ")) m = int(input("If you need upper letters press 1: ")) i = [] if n == 1: P = P + N if m == 1: P = P + M then = time.time() def worker(): for i in product(P, repeat=c): #check every possibilities k = '' for z in range(0, c): # k = k + str(i[z]) # print each possibility in a txt without parentesis or comma out_file.write( k + '\n') # out_file.close() now = time.time() diff = str(now - then) # To see how long does it take print(diff) worker() time.sleep(10) # just to check console The code check every single possibility and print it out in a test.txt file. It works but I really can't understand how can I speed it up. I saw it use 1 core out of my quad core CPU so I thought Multi-threading might work even though I don't know how. Please help me. Sorry for my English, I am from Italy.

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