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  • Pixel Perfect Collision Detection in HTML5 Canvas

    - by Armin Ronacher
    Hi, I want to check a collision between two Sprites in HTML5 canvas. So for the sake of the discussion, let's assume that both sprites are IMG objects and a collision means that the alpha channel is not 0. Now both of these sprites can have a rotation around the object's center but no other transformation in case this makes this any easier. Now the obvious solution I came up with would be this: calculate the transformation matrix for both figure out a rough estimation of the area where the code should test (like offset of both + calculated extra space for the rotation) for all the pixels in the intersecting rectangle, transform the coordinate and test the image at the calculated position (rounded to nearest neighbor) for the alpha channel. Then abort on first hit. The problem I see with that is that a) there are no matrix classes in JavaScript which means I have to do that in JavaScript which could be quite slow, I have to test for collisions every frame which makes this pretty expensive. Furthermore I have to replicate something I already have to do on drawing (or what canvas does for me, setting up the matrices). I wonder if I'm missing anything here and if there is an easier solution for collision detection.

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  • dateByAddingComponents problem and getting difference of dates with NSDateComponents problem!

    - by Rob
    I am having problems with adding values to dates and also getting differences between dates. The dates and components calculated are incorrect. So for adding, if I add 1.5 months, I only get 1 month, however if I add any whole number ie (1 or 2 or 3 and etc) it calculates correctly. Float32 addAmount = 1.5; NSDateComponents *components = [[[NSDateComponents alloc] init] autorelease]; [components setMonth:addAmount]; NSCalendar *gregorian = [[[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar] autorelease]; [gregorian setTimeZone:[NSTimeZone timeZoneWithName:@"UTC"]]; NSDate *newDate2 = [gregorian dateByAddingComponents:components toDate:Date1 options:0]; Now for difference, if I have a date that has been added with exactly one year (almost same code as above), it adds correctly, but when the difference is calculated, I get 0 years, 11 months and 30 days. NSDate *startDate = Date1; NSDate *endDate = Date2; NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar]; [gregorian setTimeZone:[NSTimeZone timeZoneWithName:@"UTC"]]; NSUInteger unitFlags = NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit; NSDateComponents *components = [gregorian components:unitFlags fromDate:startDate toDate:endDate options:0]; NSInteger years = [components year]; NSInteger months = [components month]; NSInteger days = [components day]; What am I doing wrong? Also I have added the kCFCalendarComponentsWrap constanct in the options for both adding and difference functions but with no difference. Thanks

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  • Python, dictionaries, and chi-square contingency table

    - by rohanbk
    I have a file which contains several lines in the following format (word, time that the word occurred in, and frequency of documents containing the given word within the given instance in time): #inputfile <word, time, frequency> apple, 1, 3 banana, 1, 2 apple, 2, 1 banana, 2, 4 orange, 3, 1 I have Python class below that I used to create 2-D dictionaries to store the above file using as the key, and frequency as the value: class Ddict(dict): ''' 2D dictionary class ''' def __init__(self, default=None): self.default = default def __getitem__(self, key): if not self.has_key(key): self[key] = self.default() return dict.__getitem__(self, key) wordtime=Ddict(dict) # Store each inputfile entry with a <word,time> key timeword=Ddict(dict) # Store each inputfile entry with a <time,word> key # Loop over every line of the inputfile for line in open('inputfile'): word,time,count=line.split(',') # If <word,time> already a key, increment count try: wordtime[word][time]+=count # Otherwise, create the key except KeyError: wordtime[word][time]=count # If <time,word> already a key, increment count try: timeword[time][word]+=count # Otherwise, create the key except KeyError: timeword[time][word]=count The question that I have pertains to calculating certain things while iterating over the entries in this 2D dictionary. For each word 'w' at each time 't', calculate: The number of documents with word 'w' within time 't'. (a) The number of documents without word 'w' within time 't'. (b) The number of documents with word 'w' outside time 't'. (c) The number of documents without word 'w' outside time 't'. (d) Each of the items above represents one of the cells of a chi-square contingency table for each word and time. Can all of these be calculated within a single loop or do they need to be done one at a time? Ideally, I would like the output to be what's below, where a,b,c,d are all the items calculated above: print "%s, %s, %s, %s" %(a,b,c,d)

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  • Call by Reference Function in C

    - by Chad
    Hello everyone, I would just like a push in the right direction here with my homework assignment. Here is the question: (1) Write a C function called input which returns void, this function prompts the user for input of two integers followed by a double precision value. This function reads these values from the keyboard and finds the product of the two integers entered. The function uses call by reference to communicate the values of the three values read and the product calculated back to the main program. The main program then prints the three values read and the product calculated. Provide test results for the input: 3 5 23.5. Do not use arrays or global variables in your program. And here is my code: #include <stdio.h> #include <stdlib.h> void input(int *day, int *month, double *k, double *pro); int main(void){ int i,j; double k, pro; input(&i, &j, &k, &pro); printf("%f\n", pro); return 0; } void input(int *i, int *j, double *k, double *pro){ int x,y; double z; double product; scanf("%d", &x); scanf("%d", &y); scanf("%f", &z); *pro += (x * y * z); } I can't figure out how to reference the variables with pointers really, it is just not working out for me. Any help would be great!

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  • How do i refactor this code by using Action<t> or Func<t> delegates

    - by user330612
    I have a sample program, which needs to execute 3 methods in a particular order. And after executing each method, should do error handling. Now i did this in a normal fashion, w/o using delegates like this. class Program { public static void Main() { MyTest(); } private static bool MyTest() { bool result = true; int m = 2; int temp = 0; try { temp = Function1(m); } catch (Exception e) { Console.WriteLine("Caught exception for function1" + e.Message); result = false; } try { Function2(temp); } catch (Exception e) { Console.WriteLine("Caught exception for function2" + e.Message); result = false; } try { Function3(temp); } catch (Exception e) { Console.WriteLine("Caught exception for function3" + e.Message); result = false; } return result; } public static int Function1(int x) { Console.WriteLine("Sum is calculated"); return x + x; } public static int Function2(int x) { Console.WriteLine("Difference is calculated "); return (x - x); } public static int Function3(int x) { return x * x; } } As you can see, this code looks ugly w/ so many try catch loops, which are all doing the same thing...so i decided that i can use delegates to refactor this code so that Try Catch can be all shoved into one method so that it looks neat. I was looking at some examples online and couldnt figure our if i shud use Action or Func delegates for this. Both look similar but im unable to get a clear idea how to implement this. Any help is gr8ly appreciated. I'm using .NET 4.0, so im allowed to use anonymous methods n lambda expressions also for this Thanks

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  • Efficient way of calculating average difference of array elements from array average value

    - by Saysmaster
    Is there a way to calculate the average distance of array elements from array average value, by only "visiting" each array element once? (I search for an algorithm) Example: Array : [ 1 , 5 , 4 , 9 , 6 ] Average : ( 1 + 5 + 4 + 9 + 6 ) / 5 = 5 Distance Array : [|1-5|, |5-5|, |4-5|, |9-5|, |6-5|] = [4 , 0 , 1 , 4 , 1 ] Average Distance : ( 4 + 0 + 1 + 4 + 1 ) / 5 = 2 The simple algorithm needs 2 passes. 1st pass) Reads and accumulates values, then divides the result by array length to calculate average value of array elements. 2nd pass) Reads values, accumulates each one's distance from the previously calculated average value, and then divides the result by array length to find the average distance of the elements from the average value of the array. The two passes are identical. It is the classic algorithm of calculating the average of a set of values. The first one takes as input the elements of the array, the second one the distances of each element from the array's average value. Calculating the average can be modified to not accumulate the values, but caclulating the average "on the fly" as we sequentialy read the elements from the array. The formula is: Compute Running Average of Array's elements ------------------------------------------- RA[i] = E[i] {for i == 1} RA[i] = RA[i-1] - RA[i-1]/i + A[i]/i { for i > 1 } Where A[x] is the array's element at position x, RA[x] is the average of the array's elements between position 1 and x (running average). My question is: Is there a similar algorithm, to calculate "on the fly" (as we read the array's elements), the average distance of the elements from the array's mean value? The problem is that, as we read the array's elements, the final average value of the array is not known. Only the running average is known. So calculating differences from the running average will not yield the correct result. I suppose, if such algorithm exists, it probably should have the "ability" to compensate, in a way, on each new element read for the error calculated as far.

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  • Passing IDisposable objects through constructor chains

    - by Matt Enright
    I've got a small hierarchy of objects that in general gets constructed from data in a Stream, but for some particular subclasses, can be synthesized from a simpler argument list. In chaining the constructors from the subclasses, I'm running into an issue with ensuring the disposal of the synthesized stream that the base class constructor needs. Its not escaped me that the use of IDisposable objects this way is possibly just dirty pool (plz advise?) for reasons I've not considered, but, this issue aside, it seems fairly straightforward (and good encapsulation). Codes: abstract class Node { protected Node (Stream raw) { // calculate/generate some base class properties } } class FilesystemNode : Node { public FilesystemNode (FileStream fs) : base (fs) { // all good here; disposing of fs not our responsibility } } class CompositeNode : Node { public CompositeNode (IEnumerable some_stuff) : base (GenerateRaw (some_stuff)) { // rogue stream from GenerateRaw now loose in the wild! } static Stream GenerateRaw (IEnumerable some_stuff) { var content = new MemoryStream (); // molest elements of some_stuff into proper format, write to stream content.Seek (0, SeekOrigin.Begin); return content; } } I realize that not disposing of a MemoryStream is not exactly a world-stopping case of bad CLR citizenship, but it still gives me the heebie-jeebies (not to mention that I may not always be using a MemoryStream for other subtypes). It's not in scope, so I can't explicitly Dispose () it later in the constructor, and adding a using statement in GenerateRaw () is self-defeating since I need the stream returned. Is there a better way to do this? Preemptive strikes: yes, the properties calculated in the Node constructor should be part of the base class, and should not be calculated by (or accessible in) the subclasses I won't require that a stream be passed into CompositeNode (its format should be irrelevant to the caller) The previous iteration had the value calculation in the base class as a separate protected method, which I then just called at the end of each subtype constructor, moved the body of GenerateRaw () into a using statement in the body of the CompositeNode constructor. But the repetition of requiring that call for each constructor and not being able to guarantee that it be run for every subtype ever (a Node is not a Node, semantically, without these properties initialized) gave me heebie-jeebies far worse than the (potential) resource leak here does.

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  • Ordering by formula fields in NHibernate

    - by Darin Dimitrov
    Suppose that I have the following mapping with a formula property: <class name="Planet" table="planets"> <id name="Id" column="id"> <generator class="native" /> </id> <!-- somefunc() is a native SQL function --> <property name="Distance" formula="somefunc()" /> </class> I would like to get all planets and order them by the Distance calculated property: var planets = session .CreateCriteria<Planet>() .AddOrder(Order.Asc("Distance")) .List<Planet>(); This is translated to the following query: SELECT Id as id0, somefunc() as formula0 FROM planets ORDER BY somefunc() Desired query: SELECT Id as id0, somefunc() as formula0 FROM planets ORDER BY formula0 If I set a projection with an alias it works fine: var planets = session .CreateCriteria<Planet>() .SetProjection(Projections.Alias(Projections.Property("Distance"), "dist")) .AddOrder(Order.Asc("dist")) .List<Planet>(); SQL: SELECT somefunc() as formula0 FROM planets ORDER BY formula0 but it populates only the Distance property in the result and I really like to avoid projecting manually over all the other properties of my object (there could be many other properties). Is this achievable with NHibernate? As a bonus I would like to pass parameters to the native somefunc() SQL function. Anything producing the desired SQL is acceptable (replacing the formula field with subselects, etc...), the important thing is to have the calculated Distance property in the resulting object and order by this distance inside SQL.

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  • java.math.BigInteger pow(exponent) question

    - by Jan Kraus
    Hi, I did some tests on pow(exponent) method. Unfortunately, my math skills are not strong enough to handle the following problem. I'm using this code: BigInteger.valueOf(2).pow(var); Results: var | time in ms 2000000 | 11450 2500000 | 12471 3000000 | 22379 3500000 | 32147 4000000 | 46270 4500000 | 31459 5000000 | 49922 See? 2,500,000 exponent is calculated almost as fast as 2,000,000. 4,500,000 is calculated much faster then 4,000,000. Why is that? To give you some help, here's the original implementation of BigInteger.pow(exponent): public BigInteger pow(int exponent) { if (exponent < 0) throw new ArithmeticException("Negative exponent"); if (signum==0) return (exponent==0 ? ONE : this); // Perform exponentiation using repeated squaring trick int newSign = (signum<0 && (exponent&1)==1 ? -1 : 1); int[] baseToPow2 = this.mag; int[] result = {1}; while (exponent != 0) { if ((exponent & 1)==1) { result = multiplyToLen(result, result.length, baseToPow2, baseToPow2.length, null); result = trustedStripLeadingZeroInts(result); } if ((exponent >>>= 1) != 0) { baseToPow2 = squareToLen(baseToPow2, baseToPow2.length, null); baseToPow2 = trustedStripLeadingZeroInts(baseToPow2); } } return new BigInteger(result, newSign); }

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  • What is a fast way to set debugging code at a given line in a function?

    - by Josh O'Brien
    Preamble: R's trace() is a powerful debugging tool, allowing users to "insert debugging code at chosen places in any function". Unfortunately, using it from the command-line can be fairly laborious. As an artificial example, let's say I want to insert debugging code that will report the between-tick interval calculated by pretty.default(). I'd like to insert the code immediately after the value of delta is calculated, about four lines up from the bottom of the function definition. (Type pretty.default to see where I mean.) To indicate that line, I need to find which step in the code it corresponds to. The answer turns out to be step list(c(12, 3, 3)), which I zero in on by running through the following steps: as.list(body(pretty.default)) as.list(as.list(body(pretty.default))[[12]]) as.list(as.list(as.list(body(pretty.default))[[12]])[[3]]) as.list(as.list(as.list(body(pretty.default))[[12]])[[3]])[[3]] I can then insert debugging code like this: trace(what = 'pretty.default', tracer = quote(cat("\nThe value of delta is: ", delta, "\n\n")), at = list(c(12,3,3))) ## Try it a <- pretty(c(1, 7843)) b <- pretty(c(2, 23)) ## Clean up untrace('pretty.default') Questions: So here are my questions: Is there a way to print out a function (or a parsed version of it) with the lines nicely labeled by the steps to which they belong? Alternatively, is there another easier way, from the command line, to quickly set debugging code for a specific line within a function? Addendum: I used the pretty.default() example because it is reasonably tame, but with real/interesting functions, repeatedly using as.list() quickly gets tiresome and distracting. Here's an example: as.list(as.list(as.list(as.list(as.list(as.list(as.list(as.list(as.list(body(# model.frame.default))[[26]])[[3]])[[2]])[[4]])[[3]])[[4]])[[4]])[[4]])[[3]]

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  • vba: what does ReDim Preserve do and simple array question

    - by every_answer_gets_a_point
    i am looking at someone else's vba excel code. they are doing ReDim Preserve dataMatrix(7, i) in both loops. what does this do? also, it seems like the second loop just overwrites the data in the first, loop, is that correct? Dim dataMatrix() As String Worksheets.Item("ETS").Select Do While Trim(Cells(r, 1)) <> "" Debug.Print "The line: ", Trim(Cells(r, 1)), r r = r + 1 dataMatrix(1, i) = Trim(Cells(r, 1)) ''file name dataMatrix(2, i) = Trim(Cells(r, 2)) ''sample type dataMatrix(3, i) = Trim(Cells(r, 3)) ''sample name dataMatrix(4, i) = "ETS" '' dataMatrix(5, i) = Trim(Cells(r, 5)) ''Response dataMatrix(6, i) = Trim(Cells(r, 6)) ''ISTD Response dataMatrix(7, i) = Trim(Cells(r, 10)) ''Calculated Conc i = i + 1 ReDim Preserve dataMatrix(7, i) Loop r = 5 Worksheets.Item("ETG").Select Do While Trim(Cells(r, 1)) <> "" Debug.Print "The line: ", Trim(Cells(r, 1)), r r = r + 1 dataMatrix(1, i) = Trim(Cells(r, 1)) ''file name dataMatrix(2, i) = Trim(Cells(r, 2)) ''sample type dataMatrix(3, i) = Trim(Cells(r, 3)) ''sample name dataMatrix(4, i) = "ETG" dataMatrix(5, i) = Trim(Cells(r, 5)) ''Response dataMatrix(6, i) = Trim(Cells(r, 6)) ''ISTD Response dataMatrix(7, i) = Trim(Cells(r, 10)) ''Calculated Conc i = i + 1 ReDim Preserve dataMatrix(7, i) Loop

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  • How to write these two queries for a simple data warehouse, using ANSI SQL?

    - by morpheous
    I am writing a simple data warehouse that will allow me to query the table to observe periodic (say weekly) changes in data, as well as changes in the change of the data (e.g. week to week change in the weekly sale amount). For the purposes of simplicity, I will present very simplified (almost trivialized) versions of the tables I am using here. The sales data table is a view and has the following structure: CREATE TABLE sales_data ( sales_time date NOT NULL, sales_amt double NOT NULL ) For the purpose of this question. I have left out other fields you would expect to see - like product_id, sales_person_id etc, etc, as they have no direct relevance to this question. AFAICT, the only fields that will be used in the query are the sales_time and the sales_amt fields (unless I am mistaken). I also have a date dimension table with the following structure: CREATE TABLE date_dimension ( id integer NOT NULL, datestamp date NOT NULL, day_part integer NOT NULL, week_part integer NOT NULL, month_part integer NOT NULL, qtr_part integer NOT NULL, year_part integer NOT NULL, ); which partition dates into reporting ranges. I need to write queries that will allow me to do the following: Return the change in week on week sales_amt for a specified period. For example the change between sales today and sales N days ago - where N is a positive integer (N == 7 in this case). Return the change in change of sales_amt for a specified period. For in (1). we calculated the week on week change. Now we want to know how that change is differs from the (week on week) change calculated last week. I am stuck however at this point, as SQL is my weakest skill. I would be grateful if an SQL master can explain how I can write these queries in a DB agnostic way (i.e. using ANSI SQL).

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  • Is there a set based solution for this problem?

    - by NYSystemsAnalyst
    We have a table set up as follows: |ID|EmployeeID|Date |Category |Hours| |1 |1 |1/1/2010 |Vacation Earned|2.0 | |2 |2 |2/12/2010|Vacation Earned|3.0 | |3 |1 |2/4/2010 |Vacation Used |1.0 | |4 |2 |5/18/2010|Vacation Earned|2.0 | |5 |2 |7/23/2010|Vacation Used |4.0 | The business rules are: Vacation balance is calculated by vacation earned minus vacation used. Vacation used is always applied against the oldest vacation earned amount first. We need to return the rows for Vacation Earned that have not been offset by vacation used. If vacation used has only offset part of a vacation earned record, we need to return that record showing the difference. For example, using the above table, the result set would look like: |ID|EmployeeID|Date |Category |Hours| |1 |1 |1/1/2010 |Vacation Earned|1.0 | |4 |2 |5/18/2010|Vacation Earned|1.0 | Note that record 2 was eliminated because it was completely offset by used time, but records 1 and 4 were only partially used, so they were calculated and returned as such. The only way we have thought of to do this is to get all of the vacation earned records in a temporary table. Then, get the total vacation used and loop through the temporary table, deleting the oldest record and subtracting that value from the total vacation used until the total vacation used is zero. We could clean it up for when the remaining vacation used is only part of the oldest vacation earned record. This would leave us with just the outstanding vacation earned records. This works, but it is very inefficient and performs poorly. Also, the performance will just degrade over time as more and more records are added. Are there any suggestions for a better solution, preferable set based? If not, we'll just have to go with this.

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  • What is the proper way to wait a script loaded completely before another

    - by FatDogMark
    I am making a website that is divided by several sections <div id='section-1' class='section'>web content</div> <div id='section-2' class='section'>web content</div> I have like ten sections on my webpage ,each sections height is set to the user window height when document is ready by javascript $('.section').height($(window).height()); Some effects like slideshows on my webpage require the calculated height of the section in order to work properly. Therefore I always use something like this at document ready as a solution. setTimeout(startslideshow,1000); setTimeout(startanimations,1000); ...etc To make sure the section height is the user window height before the slideshow's code start because the sections cannot change to user window height instantly once the webpage loaded will generate serious problems in my slideshow code,like wrong calculated positions. Therefore there will be a situation that's after the page loaded, there will be about a second everything is messed up,before everything can works properly, how could I avoid that being seen by the user? I tried to $(document).hide(),or $('html,body').hide(), then fade in after a second,but I get other weird problems, especially on ipad,my fixed position top navigation bar will always become 'not fixed' while user is scrolling. As I am a self-learner, I afraid my method is not typical. I want to know what is the common ways of real web programmers usually do when they have to divide his webpage into different sections and set its height to window height , then make sure the other effects that's depends on the section height works properly and avoid to wait the height change for a second?

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  • Sorting in Pivot Table on how data is summarized, not just the value

    - by user26453
    Often I am creating pivot tables that summarize some count by some category. Let's say I am counting Yes/No responses by some category. I usually add the count field and display it as a "% of row", and then create a pivot chart. However, if I want to sort one of the columns, say "Yes", Excel sorts by the underlying count, not the calculated percentage. Any way around this?

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  • \G like vertical output in MySQL Workbench for show engine innodb status

    - by KCD
    show engine innodb status; is unusable in MySQL Workbench, as shown here: =====================================120329 12:39:32 INNODB MONITOR OUTPUT=====================================Per second averages calculated from the last 17 seconds-----------------BACKGROUND THREAD-----------------srv_master_thread loops: 192438... However show engine innodb status \G is great on the mysql command line client. Is there any \G equivalent on MySQL workbench or better way to get this information?

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  • Calculate using an Averaged coumn in a pivot

    - by Emily Y
    Hi, I have a pivot which includes goals and year results. Because goal is the same on each meausure, I have to average the goal in the pivot in order to show the correct amount. I then want to calculate v% between the goal and the year result. Because the goal is averaged, v% cannot be calculated correctly. Does anyone know of a way to do calcuation like this in a pivot? Thanks a lot, Emily

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  • My pivot chart has the wrong Y axis values but correct data point values

    - by Mark Harnett
    I created a pivot chart based on some raw data for the x axis (dates) and 4 calculated fields for the Y values. The values on resulting lines are correct (see the data label at the end of the line) but the Y axis is off by about 100, but not off by any consistent amount. I have played with auto axis on and off, turn log scale on and off. All to no avail. Does anybody have any thoughts? Image link

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  • Merging Flash animations

    - by Radu
    If I have a Flash project in which there are multiple movie clips animating, each with its own timeline and other embedded movie clips, again, each with its own timeline, how can I merge everything so that I end up with a single timeline and a single layer? If Flash doesn't support this, maybe there's something else out there that can do this? I'm thinking that such a tool would need to calculate the intermediary tween values and somehow create keyframes with those values, then break everything apart and only animate the correct parts from the calculated keyframe values...

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  • How to monitor IO svctm with every 5 mins frequency using nagios?

    - by sabya
    I want to collect samples of iostat's svctm, await every 5 mins from all of my servers and store them in nagios. I want to get the values for what is happening in every 5 minutes (not since boot time, iostat's first output gives values since boot time). How can I do it in nagios? EDIT The tps should NOT be calculated #of transactions happened since reboot divided by uptime. What I want is # of transferred happened in last X mins divided X*60.

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  • how to set php SERVER_PORT var to 80, behind varnish?

    - by Daniel
    how to force php to read SERVER_PORT as 80, when apache listens on 8080 and varnish listens on 80 ?? if my apache vhost is set to 8080, SERVER_PORT will always be 8080, this is troubling me a little since in many parts of the application some links are calculated with SERVER_NAME and SERVER_PORT together, .. so what I need is that php "believes" that SERVER_PORT is 80, so all links will pass trough varnish regards Daniel

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