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• User control attributes at design-time

  - by ciscoheat

  I'm testing a simple User Control in Visual Studio 2008: A Panel named Wrapper with some controls inside. Can Visual Studio handle this at design time? public partial class TestControl : System.Web.UI.UserControl { [Description("Css class of the div around the control.")] [CssClassProperty] public string CssClass { get { return Wrapper.CssClass; } set { Wrapper.CssClass = value; } } } When setting the CssClass property, it doesn't update the css of the Panel at design time. Am I hoping for too much?

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• Time Complexities of recursive algorithms

  - by Peter

  Whenever I see a recursive solution, or I write recursive code for a problem, it is really difficult for me to figure out the time complexity, in most of the cases I just say its exponential? How is it exponential actually? How people say it is 2^n, when it is n!, when it is n^n or n^k. I have some questions in mind, let say find all permutations of a string (O(n!)) find all sequences which sum up to k in an array (exponential, how exactly do I calculate). Find all subsets of size k whose sum is 0 (will k come somewhere in complexity , it should come right?). Can any1 help me how to calculate the exact complexity of such questions, I am able to wrote code for them , but its hard understanding the exact time complexity.

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• MySQL Split Time Ranges into Smaller Chunks

  - by Neren

  Hello all, I've recently been tasked with finishing a PHP/MySQL web app when the developer quit last week. I'm no MySQL expert, so I apologize if this is an intensely simple question. I've searched SO for the better part of two days trying to find a relatively easy solution to my problem, which is as follows. Problem in a Nutshell: I have a MySQL table full of start and end datetime (GMT -5) & UNIX Timestamp values covering durations of irregular length and need to break/split/divide them into more-regular time chunks (5 minutes). I'm not after a count of row entries per time chunk/bucket/period, if that makes any sense. Data Example: started, ended, started_UNIX, ended_UNIX 2010-10-25 15:12:33, 2010-10-25 15:47:09, 1288033953, 1288036029 What I'm hoping to get: 2010-10-25 15:12:33, 2010-10-25 15:15:00, 1288033953, 1288037700 2010-10-25 15:15:00, 2010-10-25 15:20:00, 1288037700, 1288038000 2010-10-25 15:20:00, 2010-10-25 15:25:00, 1288038000, 1288038300 2010-10-25 15:25:00, 2010-10-25 15:30:00, 1288038300, 1288038600 2010-10-25 15:30:00, 2010-10-25 15:35:00, 1288038600, 1288038900 2010-10-25 15:35:00, 2010-10-25 15:40:00, 1288038900, 1288039200 2010-10-25 15:40:00, 2010-10-25 15:45:00, 1288039200, 1288039500 2010-10-25 15:45:00, 2010-10-25 15:47:09, 1288039500, 1288039629 If you're interested, here's the quick & dirty on the app and why I need the data: App overview: The application receives very simple POST requests generated by a basic sensor device when its input pins go to ground, which submits an INSERT query to the database where MySQL records a timestamp (as started). When the input pins return from a grounded state, the device submits a different POST request, which causes the PHP app to submit an UPDATE query, where a modification time timestamp is inserted (as ended). My employer recently changed the periodic reporting unit of measure from Seconds "On" Per Day to Seconds "On" Per 5 Minute Interval. I had formulated what I thought would be a workable solution, but when I looked at it on paper, it looked like Rube Goldberg's nightmare constructed in MySQL, so that was out. Any suggestions as to how to break these spans into 5 minute blocks? Keeping it all in MySQL would be my preference, though I'll take any suggestions. Thank you for any suggestions you may have. Again, I apologize if this is a no-brainer. If I ask any additional questions of the SO collective consciousness in the future, I'll try to word them a bit better. Any help will be happily welcomed. Thanks, Neren

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• Rails: How do I get created_at to show the time in my current time zone?

  - by Schneems

  Seems that when i create an object, the time is not correct. You can see by the script/console output below. Has anyone encountered anything like this, or have any debugging tips? >> Ticket.create(...) => #<Ticket id: 7, from_email: "[email protected]", ticket_collaterals: nil, to_email: "[email protected]", body: "hello", subject: "testing", status: nil, whymail_id: nil, created_at: "2009-12-31 04:23:20", updated_at: "2009-12-31 04:23:20", forms_id: nil, body_hash: nil> >> Ticket.last.created_at.to_s(:long) => "December 31, 2009 04:23" >> Time.now.to_s(:long) => "December 30, 2009 22:24"

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• c++ thread running time

  - by chnet

  I want to know whether I can calculate the running time for each thread. I implement a multithread program in C++ using pthread. As we know, each thread will compete the CPU. Can I use clock() function to calculate the actual number of CPU clocks each thread consumes? my program looks like: Class Thread () { Start(); Run(); Computing(); }; Start() is to start multiple threads. Then each thread will run Computing function to do something. My question is how I can calculate the running time of each thread for Computing function

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• Python daylight savings time

  - by Uszy Wieloryba

  How to chek if daylight savings time is in effect?

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• Using system time directly to get random numbers

  - by Richard Mar.

  I had to return a random element from an array so I came up with this placeholder: return codes[(int) (System.currentTimeMillis() % codes.length - 1)]; Now than I think of it, I'm tempted to use it in real code. The Random() seeder uses system time as seed in most languages anyway, so why not use that time directly? As a bonus, I'm free from the worry of non-random lower bits of many RNGs. It this hack coming back to bite me? (The language is Java if that's relevant.)

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• long waiting time in linking

  - by ccanan

  Hi, here is the situation. I am using visual studio 2005. the solution contains lots of projects, 34 projects in all, and the start up projects depends on others. then in linking part, it'll wait a long time before the real linking starts. I am pretty sure it's because of too many projects depended, as when I use a solution with 10 of the 34 projects(keep other projects as headers&libs), it'll start instantly. so any one has any idea that I can reduce the waiting time? thx.

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• Get current time and date

  - by Ockonal

  Hello, is there a crossplatform way to get current date and time in c++? Thanks.

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• Response time increasing (worsening) over time with consistent load

  - by NJ

  Ok. I know I don't have a lot of information. That is, essentially, the reason for my question. I am building a game using Flash/Flex and Rails on the back-end. Communication between the two is via WebORB. Here is what is happening. When I start the client an operation calls the server every 60 seconds (not much, right?) which results in two database SELECTS and an UPDATE and a resulting response to the client. This repeats every 60 seconds. I deployed a test version on heroku and NewRelic's RPM told me that response time degraded over time. One client with one task every 60 seconds. Over several hours the response time drifted from 150ms to over 900ms in response time. I have been able to reproduce this in my development environment (my Macbook Pro) so it isn't a problem on Heroku's side. I am not doing anything sophisticated (by design) in the server app. An action gets called, gets some data from the database, performs an AR update and then returns a response. No caching, etc. Any thoughts? Anyone? I'd really appreciate it.

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• Terrible ping time with TP-Link wireless router

  - by rabbid

  I am literally a foot away from this useless TL-WR340G/TL-WR340GD router and check out this ping time: 64 bytes from 192.168.1.8: icmp_seq=291 ttl=64 time=9477.516 ms 64 bytes from 192.168.1.8: icmp_seq=292 ttl=64 time=8954.423 ms 64 bytes from 192.168.1.8: icmp_seq=293 ttl=64 time=8262.836 ms 64 bytes from 192.168.1.8: icmp_seq=294 ttl=64 time=7937.853 ms 64 bytes from 192.168.1.8: icmp_seq=295 ttl=64 time=7517.768 ms 64 bytes from 192.168.1.8: icmp_seq=296 ttl=64 time=7106.063 ms 64 bytes from 192.168.1.8: icmp_seq=297 ttl=64 time=6492.109 ms 64 bytes from 192.168.1.8: icmp_seq=298 ttl=64 time=5835.305 ms 64 bytes from 192.168.1.8: icmp_seq=299 ttl=64 time=5314.897 ms 64 bytes from 192.168.1.8: icmp_seq=300 ttl=64 time=4902.705 ms 64 bytes from 192.168.1.8: icmp_seq=301 ttl=64 time=4716.959 ms 64 bytes from 192.168.1.8: icmp_seq=302 ttl=64 time=5224.450 ms 64 bytes from 192.168.1.8: icmp_seq=303 ttl=64 time=5024.079 ms 64 bytes from 192.168.1.8: icmp_seq=304 ttl=64 time=5044.100 ms 64 bytes from 192.168.1.8: icmp_seq=305 ttl=64 time=4477.990 ms 64 bytes from 192.168.1.8: icmp_seq=306 ttl=64 time=3582.432 ms 64 bytes from 192.168.1.8: icmp_seq=307 ttl=64 time=2911.896 ms At this time mine is the only computer using the router. This happens from time to time. I'd restart the router, and then it'll have a 1-2 ms ping for a while, and then back to terrible ping. Is it just a poor quality router? Suggestions? Thank you

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• Is there any way to properly display negative time spans in Excel?

  - by Pepor

  Is there any way to make Excel show a negative time span? If I subtract two time values (say, when subtracting the actual amount of time spent on something from the amount of time planned for it) and the result is negative, Excel just fills the result cell with hashes to notify me that the result cannot be displayed as a time value. Even OpenOffice.org Calc and Google Spreadsheets can display negative time values. Is there a way to work around that issue by using conditional formatting? I really don't want to create some workaround by calculating the hours and minutes myself or anything like that.

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• Calculate travel time on road map with semaphores

  - by Ivansek

  I have a road map with intersections. At intersections there are semaphores. For each semaphore I generate a red light time and green light time which are represented with syntax [R:T1, G:T2], for example: 119 185 250 A ------- B: [R:6, G:4] ------ C: [R:5, G:5] ------ D I want to calculate a car travel time from A - D. Now I do this with this pseudo code: function get_travel_time(semaphores_configuration) { time = 0; for( i=1; i<path.length;i++) { prev_node = path[i-1]; next_node = path[i]); cost = cost_between(prev_node, next_node) time += (cost/movement_speed) // movement_speed = 50px per second light_times = get_light_times(path[i], semaphore_configurations) lights_cycle = get_lights_cycle(light_times) // Eg: [R,R,R,G,G,G,G], where [R:3, G:4] lights_sum = light_times.green_time+light_times.red_light; // Lights cycle time light = lights_cycle[cost%lights_sum]; if( light == "R" ) { time += light_times.red_light; } } return time; } So for distance 119 between A and B travel time is, 119/50 = 2.38s ( exactly mesaured time is between 2.5s and 2.6s), then we add time if we came at a red light when at B. If we came at a red light is calculated with lines: lights_cycle = get_lights_cycle(light_times) // Eg: [R,R,R,G,G,G,G], where [R:3, G:4] lights_sum = light_times.green_time+light_times.red_light light = lights_cycle[cost%lights_sum]; if( light == "R" ) { time += light_times.red_light; } This pseudo code doesn't calculate exactly the same times as they are mesaured, but the calculations are very close to them. Any idea how I would calculate this?

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• Need efficient way to keep enemy from getting hit multiple times by same source

  - by TenFour04

  My game's a simple 2D one, but this probably applies to many types of scenarios. Suppose my player has a sword, or a gun that shoots a projectile that can pass through and hit multiple enemies. While the sword is swinging, there is a duration where I am checking for the sword making contact with any enemy on every frame. But once an enemy is hit by that sword, I don't want him to continue getting hit over and over as the sword follows through. (I do want the sword to continue checking whether it is hitting other enemies.) I've thought of a couple different approaches (below), but they don't seem like good ones to me. I'm looking for a way that doesn't force cross-referencing (I don't want the enemy to have to send a message back to the sword/projectile). And I'd like to avoid generating/resetting multiple array lists with every attack. Each time the sword swings it generates a unique id (maybe by just incrementing a global static long). Every enemy keeps a list of id's of swipes or projectiles that have already hit them, so the enemy knows not to get hurt by something multiple times. Downside is that every enemy may have a big list to compare to. So projectiles and sword swipes would have to broadcast their end-of-life to all enemies and cause a search and remove on every enemy's array list. Seems kind of slow. Each sword swipe or projectile keeps its own list of enemies that it has already hit so it knows not to apply damage. Downsides: Have to generate a new list (probably pull from a pool and clear one) every time a sword is swung or a projectile shot. Also, this breaks down modularity, because now the sword has to send a message to the enemy, and the enemy has to send a message back to the sword. Seems to me that two-way streets like this are a great way to create very difficult-to-find bugs.

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• I need to calculate the date / time difference between one date time column

  - by Stringz

  Details. I have the notes table having the following columns. ID - INT(3) Date - DateTime Note - VARCHAR(100) Tile - Varchar(100) UserName - Varchar(100) Now this table will be having NOTES along with the Titles entered by UserName on the specified date / time. I need to calculate the DateTimeDifference between the TWO ROWS in the SAME COLUMN For example the above table has this peice of information in the table. 64, '2010-03-26 18:16:13', 'Action History', 'sending to Level 2.', 'Salman Khwaja' 65, '2010-03-26 18:19:48', 'Assigned By', 'This is note one for the assignment of RF.', 'Salman Khwaja' 66, '2010-03-27 19:19:48', 'Assigned By', 'This is note one for the assignment of CRF.', 'Salman Khwaja' Now I need to have the following resultset in query reports using MYSQL. TASK - TIME Taken ACTION History - 2010-03-26 18:16:13 Assigned By - 00:03:35 Assigned By - 25:00:00 More smarter approach would be TASK - TIME Taken ACTION History - 2010-03-26 18:16:13 Assigned By - 3 minutes 35 seconds Assigned By - 1 day, 1 hour. I would appreciate if one could give me the PLAIN QUERY along with PHP code to embed it too.

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• Custom date time picker for Windows Forms that is locked to GMT time

  - by m3ntat

  Using Visual Studio 2008, c#, .net 2.0. I have a Windows Forms client application that contains a scheduling UI section, currently this is housed only in the London office with the standard datetime picker control, the selected time is saved in a UK database (GMT) and a London based server aapplication processes the schedules. There is a requirement to roll the client out to various global locations, Hong Kong, New York etc and allow them to setup schedules that run according to GMT time on the London server. I'll have a label on screen saying "note schedules are GMT" what I need is a good way to present a datetime picker that always shows and is in sync with the database server's GMT time regardless of where the client app is running globally. Suggestions on how to acheive this? thanks.

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• Temperature anomaly calculation of time series data

  - by neel

  I have a time series like following: Data <- structure(list(Year = c(1991L, 1991L, 1991L, 1991L, 1991L, 1991L, 1991L, 1991L, 1991L, 1991L, 1991L, 1991L, 1991L, 1992L, 1992L, 1992L, 1992L, 1992L, 1992L, 1992L, 1992L, 1992L, 1992L, 1992L, 1992L, 1992L, 1992L, 1992L, 1992L, 1992L, 1992L, 1992L, 1992L, 1992L, 1992L, 1992L, 1992L, 1992L, 1992L, 1992L, 1992L, 1992L, 1992L, 1992L, 1992L, 1992L, 1992L, 1992L, 1992L), Month = c(8L, 9L, 9L, 9L, 10L, 10L, 10L, 11L, 11L, 11L, 12L, 12L, 12L, 1L, 1L, 1L, 2L, 2L, 2L, 3L, 3L, 3L, 4L, 4L, 4L, 5L, 5L, 5L, 6L, 6L, 6L, 7L, 7L, 7L, 8L, 8L, 8L, 9L, 9L, 9L, 10L, 10L, 10L, 11L, 11L, 11L, 12L, 12L, 12L), Day = c(30L, 10L, 20L, 30L, 10L, 20L, 30L, 10L, 20L, 30L, 10L, 20L, 30L, 10L, 20L, 30L, 10L, 20L, 28L, 10L, 20L, 30L, 10L, 20L, 30L, 10L, 20L, 30L, 10L, 20L, 30L, 10L, 20L, 30L, 10L, 20L, 30L, 10L, 20L, 30L, 10L, 20L, 30L, 10L, 20L, 30L, 10L, 20L, 30L), Hour = c(0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L), temperature = c(72.5, 64, 62.5, 64, 64, 53, 52, 52, 45.5, 49, 50, 50, 59, 63.5, 69.5, 61, 61, NaN, NaN, 39.5, 37, 45.5, 45, 39, 43.5, 52, 53, 56, 64, 66, 66.5, 73.5, 81, 85, 89.5, 87.5, 88.5, 83, 84.5, 74, 60.5, 59, 53, 60.5, 62.5, 64.5, 63, 62, 65.5)), .Names = c("Year", "Month", "Day", "Hour", "temperature"), class = "data.frame", row.names = c(NA, -49L)) and I have to calculate standardized anomaly. The steps to calculate the anomalies are following: Monthly premature departures from the long-term (1991-2007) average are obtained. Then standardized by dividing by the standard deviation of monthly temperature. The standardized monthly anomalies are then weighted by multiplying by the fraction of the average temperature for the given month. These weighted anomalies are then summed over 3 month time period. Can you please help me?

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• java time check API

  - by ring bearer

  I am sure this was done 1000 times in 1000 different places. The question is I want to know if there is a better/standard/faster way to check if current "time" is between two time values given in hh:mm:ss format. For example, my big business logic should not run between 18:00:00 and 18:30:00. So here is what I had in mind: public static boolean isCurrentTimeBetween(String starthhmmss, String endhhmmss) throws ParseException{ DateFormat hhmmssFormat = new SimpleDateFormat("yyyyMMddhh:mm:ss"); Date now = new Date(); String yyyMMdd = hhmmssFormat.format(now).substring(0, 8); return(hhmmssFormat.parse(yyyMMdd+starthhmmss).before(now) && hhmmssFormat.parse(yyyMMdd+endhhmmss).after(now)); } Example test case: String doNotRunBetween="18:00:00,18:30:00";//read from props file String[] hhmmss = downTime.split(","); if(isCurrentTimeBetween(hhmmss[0], hhmmss[1])){ System.out.println("NOT OK TO RUN"); }else{ System.out.println("OK TO RUN"); } What I am looking for is code that is better in performance in looks in correctness What I am not looking for third-party libraries Exception handling debate variable naming conventions method modifier issues

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• average case running time of linear search algorithm

  - by Brahadeesh

  Hi all. I am trying to derive the average case running time for deterministic linear search algorithm. The algorithm searches an element x in an unsorted array A in the order A[1], A[2], A[3]...A[n]. It stops when it finds the element x or proceeds until it reaches the end of the array. I searched on wikipedia and the answer given was (n+1)/(k+1) where k is the number of times x is present in the array. I approached in another way and am getting a different answer. Can anyone please give me the correct proof and also let me know whats wrong with my method? E(T)= 1*P(1) + 2*P(2) + 3*P(3) ....+ n*P(n) where P(i) is the probability that the algorithm runs for 'i' time (i.e. compares 'i' elements). P(i)= (n-i)C(k-1) * (n-k)! / n! Here, (n-i)C(k-1) is (n-i) Choose (k-1). As the algorithm has reached the ith step, the rest of k-1 x's must be in the last n-i elements. Hence (n-i)C(k-i). (n-k)! is the total number of ways of arranging the rest non x numbers, and n! is the total number of ways of arranging the n elements in the array. I am not getting (n+1)/(k+1) on simplifying.

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• Time complexity of a certain program

  - by HokageSama

  In a discussion with my friend i am not able to predict correct and tight time complexity of a program. Program is as below. /* This Function reads input array "input" and update array "output" in such a way that B[i] = index value of nearest greater value from A[i], A[i+1] ... A[n], for all i belongs to [1, n] Time Complexity: ?? **/ void createNearestRightSidedLargestArr(int* input, int size, int* output){ if(!input || size < 1) return; //last element of output will always be zero, since no element is present on its right. output[size-1] = -1; int curr = size - 2; int trav; while(curr >= 0){ if(input[curr] < input[curr + 1]){ output[curr] = curr + 1; curr--; continue; } trav = curr + 1; while( input[ output [trav] ] < input[curr] && output [trav] != -1) trav = output[trav]; output[curr--] = output[trav]; } } I said time complexity is O(n^2) but my friend insists that this is not correct. What is the actual time complexity?

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• How to display locale sensitive time format without seconds in python

  - by Tim Kersten

  I can output a locale sensitive time format using strftime('%X'), but this always includes seconds. How might I display this time format without seconds? >>> import locale >>> import datetime >>> locale.setlocale(locale.LC_ALL, 'en_IE.utf-8') 'en_IE.utf-8' >>> print datetime.datetime.now().strftime('%X') 12:22:43 >>> locale.setlocale(locale.LC_ALL, 'zh_TW.utf-8') 'zh_TW.utf-8' >>> print datetime.datetime.now().strftime('%X') 12?22?58? The only way I can think of doing this is attempting to parse the output of locale.nl_langinfo(locale.T_FMT) and strip out the seconds bit, but that brings it's own trickery. >>> print locale.nl_langinfo(locale.T_FMT) %H?%M?%S? >>> locale.setlocale(locale.LC_ALL, 'en_IE.utf-8') 'en_IE.utf-8' >>> print locale.nl_langinfo(locale.T_FMT) %T

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• Fetching real time data from excel

  - by Umesh Sharma

  I am seriouly looking for your valuable help first time here. If possible, plese help me. I am developing a VB.NET app in which i read "real time data" from a excel sheet using "Microsoft.Office.Interop.Excel" i.e. excel automation. All cells in excel sheet are fetching stock data from some LOCAL DDE Server like "=XYZ|Bid!GOLD", "=XYZ|Bid!SILVER", "=XYZ|Ask!SILVER" and so on... Some cells also having fixed values like "Symbol", "Bid Rate", "32.90" etc. Values of DDE mapped cells (i.e. =XYZ|xxxx!yyy) are continuously changing. THE PROBLEM is here..."FIXED values" from excel cells are coming quite ok to my app but all DDE mapped cells values are coming "-2146826246" (When datasource local dde server ON) or "-2146826265" (OFF). Although, if i use C#.NET, it's all ok but not with Vb.NET. I want to display range of excel (A1 to J50) into VB.NET ListView which are changing in every 200ms (5 times in every 1 second) ================ Important ====================================================== Is it possible to BIND "listview items/columns values" with "excel cells" or some local memory variables ?? Currently, i am reading excel "cell by cell" and trying to put values in .NET listview but CPU USES are very high as well as it's toooo slow process. If yes, then how please ? I am a VFP developer but new to .NET It's very easy in VFP then why not in .NET ?? Please guide me, if someone has the solution...

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• linux bash script: set date/time variable to auto-update (for inclusion in file names)

  - by user1859492

  Essentially, I have a standard format for file naming conventions. It breaks down to this: target_dateUTC_timeUTC_tool So, for instance, if I run tcpdump on a target of 'foo', then the file would be foo_dateUTC_timeUTC_tcpdump. Simple enough, but a pain for everyone to constantly (and consistently) enter... so I've tried to create a bash script which sets system variables like so: FILENAME=$TARGET\_$UTCTIME\_$TOOL Then, I can just call the variable at runtime, like so: tcpdump -w $FILENAME.lpc All of this works like a champ. I've got a menu-driven .sh which gives the user the options of viewing the current variables as well as setting them... file generation is a breeze. Unfortunately, by setting the date/time variable, it is locked to the value at the time of creation (naturally). I set the variable like so: UTCTIME=$(/bin/date --utc +"%Y%m%d_%H%M%Z") What I really need is either a way to create a variable which updates at runtime, or (more likely) another way to skin this cat. While scouring for solutions, I came across a similar issues... like this. But, to be honest, I'm stumped on how to marry the two approaches and create a simple, distributable solution. I can post the entire .sh if anyone cares to review (about 120 lines)

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• Efficient inline templates and C++

  - by Darryl Gove

  I've talked before about calling inline templates from C++, I've also talked about calling inline templates efficiently. This time I want to talk about efficiently calling inline templates from C++. The obvious starting point is that I need to declare the inline templates as being extern "C": extern "C" { int mytemplate(int); } This enables us to call it, but the call may not be very efficient because the compiler will treat it as a function call, and may produce suboptimal code based on that premise. So we need to add the no_side_effect pragma: extern "C" { int mytemplate(int); #pragma no_side_effect(mytemplate) } However, this may still not produce optimal code. We've discussed how the no_side_effect pragma cannot be combined with exceptions, well we know that the code cannot produce exceptions, but the compiler doesn't know that. If we tell the compiler that information it may be able to produce even better code. We can do this by adding the "throw()" keyword to the template declaration: extern "C" { int mytemplate(int) throw(); #pragma no_side_effect(mytemplate) } The following is an example of how these changes might improve performance. We can take our previous example code and migrate it to C++, adding the use of a try...catch construct: #include <iostream extern "C" { int lzd(int); #pragma no_side_effect(lzd) } int a; int c=0; class myclass { int routine(); }; int myclass::routine() { try { for(a=0; a<1000; a++) { c=lzd(c); } } catch(...) { std::cout << "Something happened" << std::endl; } return 0; } Compiling this produces a slightly suboptimal code sequence in the hot loop: $ CC -O -xtarget=T4 -S t.cpp t.il ... /* 0x0014 23 */ lzd %o0,%o0 /* 0x0018 21 */ add %l6,1,%l6 /* 0x001c */ cmp %l6,1000 /* 0x0020 */ bl,pt %icc,.L77000033 /* 0x0024 23 */ st %o0,[%l7] There's a store in the delay slot of the branch, so we're repeatedly storing data back to memory. If we change the function declaration to include "throw()", we get better code: $ CC -O -xtarget=T4 -S t.cpp t.il ... /* 0x0014 21 */ add %i1,1,%i1 /* 0x0018 23 */ lzd %o0,%o0 /* 0x001c 21 */ cmp %i1,999 /* 0x0020 */ ble,pt %icc,.L77000019 /* 0x0024 */ nop The store has gone, but the code is still suboptimal - there's a nop in the delay slot rather than useful work. However, it's good enough for this example. The point I'm making is that the compiler produces the better code with both the "throw()" and the no side effect pragma.

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• efficient collision detection - tile based html5/javascript game

  - by Tom Burman

  Im building a basic rpg game and onto collisions/pickups etc now. Its tile based and im using html5 and javascript. i use a 2d array to create my tilemap. Im currently using a switch statement for whatever key has been pressed to move the player, inside the switch statement. I have if statements to stop the player going off the edge of the map and viewport and also if they player is about to land on a tile with tileID 3 then the player stops. Here is the statement: canvas.addEventListener('keydown', function(e) { console.log(e); var key = null; switch (e.which) { case 37: // Left if (playerX > 0) { playerX--; } if(board[playerX][playerY] == 3){ playerX++; } break; case 38: // Up if (playerY > 0) playerY--; if(board[playerX][playerY] == 3){ playerY++; } break; case 39: // Right if (playerX < worldWidth) { playerX++; } if(board[playerX][playerY] == 3){ playerX--; } break; case 40: // Down if (playerY < worldHeight) playerY++; if(board[playerX][playerY] == 3){ playerY--; } break; } viewX = playerX - Math.floor(0.5 * viewWidth); if (viewX < 0) viewX = 0; if (viewX+viewWidth > worldWidth) viewX = worldWidth - viewWidth; viewY = playerY - Math.floor(0.5 * viewHeight); if (viewY < 0) viewY = 0; if (viewY+viewHeight > worldHeight) viewY = worldHeight - viewHeight; }, false); My question is, is there a more efficient way of handling collisions, then loads of if statements for each key? The reason i ask is because i plan on having many items that the player will need to be able to pickup or not walk through like walls cliffs etc. Thanks for your time and help Tom

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