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  • strategy to allocate/free lots of small objects

    - by aaa
    hello I am toying with certain caching algorithm, which is challenging somewhat. Basically, it needs to allocate lots of small objects (double arrays, < 256 elements), with objects accessible through mapped value, map[key] = array. time to initialized array may be quite large, generally more than 10 thousand cpu cycles. By lots I mean around gigabyte in total. objects may need to be popped/pushed as needed, generally in random places, one object at a time. lifetime of an object is generally long, minutes or more, however, object may be subject to allocation/deallocation several times during duration of program. What would be good strategy to avoid memory fragmentation, while still maintaining reasonable allocate deallocate speed? I am using C++, so I can use new and malloc. Thanks. I know there a similar questions on website, http://stackoverflow.com/questions/2156745/efficiently-allocating-many-short-lived-small-objects, are somewhat different, thread safety is not immediate issue for me.

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  • Optimal ASP.Net cache duration for a large site?

    - by HeroicLife
    I've read lots of material on how to do ASP.Net caching but little on the optimal duration that pages should be cached for. Let's say that I have a popular site with 50,000 pages. The content does not change frequently, so I could cache pages for up to an hour if I wanted. The server has 16 GB of RAM, but database connections are limited. How long should pages be cached for? My thinking is that if I set the cache duration too high (let's say 60 minutes), I will fill up memory with a fraction of the total content, which will continually be shuffled in and out of memory. Furthermore, let's say that 10% of the pages are responsible for 90% of traffic. If the popular pages are hit every second, and the unpopular ones every hour, then a 60 second cache would only keep the load-intensive content cached without sacrificing freshness. Should numerous but rarely-accessed content be cached at all?

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  • What is the difference between "a is b" and "id(a) == id(b)" in Python?

    - by bp
    The id() inbuilt function gives... an integer (or long integer) which is guaranteed to be unique and constant for this object during its lifetime. The is operator, instead, gives... object identity So why is it possible to have two objects that have the same id but return False to an is check? Here is an example: >>> class Test(): ... def test(): ... pass >>> a = Test() >>> b = Test() >>> id(a.test) == id(b.test) True >>> a.test is b.test False A more troubling example: (continuing the above) >>> b = a >>> b is a True >>> b.test is a.test False >>> a.test is a.test False

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  • Data Structure Brushup (Java)

    - by Daddy Warbox
    This should be easy for many of you, but for me it's just another bit of rust needing to be chipped away as I get back into basic Java coding. Using bloody associative arrays for so long in other languages have turned me nice and spoiled. :P My problem is simple: I'm storing a set of objects, each containing a string and a number, in a list. I would like each object inserted into this list to be sorted alphabetically by its string. I would also like to be able to retrieve objects from the list by their string as well. I would like to do this as formally and/or efficiently as possible. Is there something already available in the Java standard libraries for this?

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  • @ symbol for strings in jQuery

    - by anilca
    if (confirm('<%=Ns1.Ns2.MyClass.GetResourceText("DeleteConfirmationMessage")%>')) { /* something to do...*/ } I have a jQuery expression as above. But the return value of GetResourceText method is a very long string. So my page renders the function like below: if (confirm(' Are you sure lablabla? If you delete this lablabla... lablabla... ')) { Because of this my jQuery functions do not work. Is there a symbol for jQuery like @ that we use in C#?

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  • Solve Physics exercise by brute force approach..

    - by Nils
    Being unable to reproduce a given result. (either because it's wrong or because I was doing something wrong) I was asking myself if it would be easy to just write a small program which takes all the constants and given number and permutes it with a possible operators (* / - + exp(..)) etc) until the result is found. Permutations of n distinct objects with repetition allowed is n^r. At least as long as r is small I think you should be able to do this. I wonder if anybody did something similar here..

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  • Is it possible to have a composite index with a list property and a sort order?

    - by npdoty
    And if not, why not? The following index always fails for me, even though I had thought I could have a sort order with a list property as long as the index didn't sort or match against any other properties. - kind: Foo properties: - name: location_geocells - name: time direction: desc If such a composite index is allowed, are there any reasons that this might be failing for me? Do the existence of other indices on the same model increase the likelihood of this failure? Does the combination of a sort order with a list property require more than N entries, where N is the number of values in the list property? (If so, how many does it require?)

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  • read after lseek always return 0

    - by Wins
    I'm having an issue reading byte in file after performing lseek long cur_position = lseek(fd, length * -1, SEEK_CUR ); // Rewind file reading by length bytes. printf("cur_position: %i\n", cur_position); int num_byte = read(fd, &byte, 1); printf("num_byte = %i\n", num_byte); With the initial variable length set to 34, the above code would produce cur_position 5 (so there are definitely at least 34 bytes after the lseek function returns), but the variable num_byte returned from function read always returns 0 even though there are still more bytes to read. Does anyone know the reason num_byte always return 0 or do I make mistake in the above code? Just for information, the above code was run on the following machine $ uname -srvpio Linux 3.2.0-24-generic #39-Ubuntu SMP Mon May 21 16:52:17 UTC 2012 x86_64 x86_64 GNU/Linux

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  • "Teach" a computer how to do addition?

    - by ffar
    The problem is to learn computer to do addition. Computer have as input a knowladge of a numbers: he "knows" that after 1 goes 2, after 2 goes 3 and so on... Having that data computer can easyly get next number. Next, computer have knowlandge as input that x+0=x and x+(y+1)=(x+1)+y. This axioms let computer to do addition. For example, to add 5 and 3, computer makes following: 5+3 = 5+(2+1) = (5+1)+2 = 6+2 = 6+(1+1) = (6+1)+1 = 7+1 = 8. But this is too long to add numbers in such way. The problem is to develop program which can improve this way of addition using the rules of mathemetics and logic. The goal addition must executed in O(log(N)) time, not O(N) time, N is magnitude of added numbers. Have this program any science value? Is any program can do such things?

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  • elegant way to extract values from array

    - by smoove666
    Something that bugs me for a long time: I want to convert this Array: // $article['Tags'] array(3) { [0] => array(2) { ["id"] => string(4) "1" ["tag"] => string(5) "tag1" }, [1] => array(2) { ["id"] => string(4) "2" ["tag"] => string(5) "tag2" }, [2] => array(2) { ["id"] => string(4) "3" ["tag"] => string(5) "tag3" }, } To this form: // $extractedTags[] array(3) { [0] => string(4) "tag1", [1] => string(4) "tag2", [2] => string(4) "tag3", } currently i am using this code: $extractedTags = array(); foreach ($article['Tags'] as $tags) { $extractedTags[] = $tags['tag']; } Is there any more elegant way of doing this, maybe a php built-in function?

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  • perforce implementation of clearcase like "views"

    - by Pradyot
    I have read through the documentation on perforce and the "branching strategy" advice as well. One thing thats left me baffled, is how a simple concern is does not seem to adequtely adressed. When I am working on a project that touches many parts of our code base , I cannot checkin my code at the end of the day without checking into the trunk. So do I need to branch in this situation? I want to be able to have the ability to have a history of my changes in a long and hard project, so I can go back when I I make a wrong turn.. The problem with branching I see is that I will be creating copies of almost the entire codebase .. Am I missing an obvious solution here? thanks

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  • How to make a staging table in ms sql 2005?

    - by chobo2
    Hi I heard about doing staging tables and I am wondering how you actually do it. I want to do a sqlbulk copy into a staging table. Then then update the real table. I heard in mssql 2008 that you can use something called merge but I am using ms sql 2005 so I heard I have to use a update inner join? I am not sure how that would look like(I am guessing best way would be to write it in SP). Also the staging table needs to be able to handle concurrent updates. I was thinking of putting another column in the staged as GUID so that way I know which records belong to which group and when it is time to delete the records from the staged table I can just use that. So can anyone show me any examples or tutorials on how to do it? Also how fast is this way? Say if your updating 50,000 records how long would that take(a guesstimate is fine)

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  • Programmatically determine the relative "popularities" of a list of items (books, songs, movies, etc

    - by Horace Loeb
    Given a list of (say) songs, what's the best way to determine their relative "popularity"? My first thought is to use Google Trends. This list of songs: Subterranean Homesick Blues Empire State of Mind California Gurls produces the following Google Trends report: (to find out what's popular now, I restricted the report to the last 30 days) Empire State of Mind is marginally more popular than California Gurls, and Subterranean Homesick Blues is far less popular than either. So this works pretty well, but what happens when your list is 100 or 1000 songs long? Google Trends only allows you to compare 5 terms at once, so absent a huge round-robin, what's the right approach? Another option is to just do a Google Search for each song and see which has the most results, but this doesn't really measure the same thing

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  • dabbledb + iPhone

    - by user193545
    I have been using DabbbleDB online database for storing/retrieving values for one of my iPhone applications. I am using their JSON response for retrieving the records. The problem that I am facing is that if there are a large number of records in the database, it takes a long time to get the response from the server and then to parse the JSON response. Instead I would like to to get a set of records at a time and run a loop to fetch all the records in background. I do not know whether we can query for a set of records at a time from online databases like DabbleDB. Anybody having an idea, please help.

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  • C# background worker while loop

    - by Mike
    What i'm trying to create is a background worker that executes a few processes every 30seconds. But I want this while loop to execute for as long as the program is launched. here is what I am using: private void watcherprocess1() { backgroundWorker1.RunWorkerAsync(); } private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e) { while( Thread.Sleep(30000); specficView2(); makeFormlist2(); populateListview2(); } My main issue is ai can think of a good while loop to keep this running

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  • Redundant naming in C/C++ typedefs/structs

    - by bloomy
    #include <stdio.h> #include <string.h> const int NAMELEN=30; const int MAXCLASSSIZE=10; typedef struct StudentRec { char lastname[NAMELEN]; char firstname[NAMELEN]; long int ID; int finalmark; }Student; I'm new to coding..and I have a question about why there is Student; after the bracket.. is it a format that we have to follow.

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  • Delete from empty table taking forver

    - by Will
    Hello, I have an empty table that previously had a large amount of rows. The table has about 10 columns and indexes on many of them, as well as indexes on multiple columns. DELETE FROM item WHERE 1=1 This takes approximately 40 seconds to complete SELECT * FROM item this takes 4 seconds. The execution plan of SELECT * FROM ITEM shows the following; SQL> select * from midas_item; no rows selected Elapsed: 00:00:04.29 Execution Plan ---------------------------------------------------------- 0 SELECT STATEMENT Optimizer=CHOOSE (Cost=19 Card=123 Bytes=73 80) 1 0 TABLE ACCESS (FULL) OF 'MIDAS_ITEM' (Cost=19 Card=123 Byte s=7380) Statistics ---------------------------------------------------------- 0 recursive calls 0 db block gets 5263 consistent gets 5252 physical reads 0 redo size 1030 bytes sent via SQL*Net to client 372 bytes received via SQL*Net from client 1 SQL*Net roundtrips to/from client 0 sorts (memory) 0 sorts (disk) 0 rows processed any idea why these would be taking so long and how to fix it would be greatly appreciated!!

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  • How to use `wx.ProgressDialog` with my own method?

    - by user1401950
    How can I use the wx.ProgressDialog to time my method called imgSearch? The imgSearch method finds image files on the user's pc. How can I make the wx.ProgressDialog run while imgSearch is still running and display how long the imgSearch is taking? Here's my code: def onFind (self,event)# triggered by a button click max = 80 dlg = wx.ProgressDialog("Progress dialog example","An informative message",parent=self, style = wx.PD_CAN_ABORT| wx.PD_APP_MODAL| wx.PD_ELAPSED_TIME| wx.PD_REMAINING_TIME) keepGoing = True count = 0 imageExtentions = ['*.jpg', '*.jpeg', '*.png', '*.tif', '*.tiff'] selectedDir = 'C:\\' imgSearch.findImages(imageExtentions, selectedDir)# my method while keepGoing and count < max: count += 1 wx.MilliSleep(250) if count >= max / 2: (keepGoing, skip) = dlg.Update(count, "Half-time!") else: (keepGoing, skip) = dlg.Update(count) dlg.Destroy()

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  • How to calculate deceleration rate of a flipping coin (in c)?

    - by Horace Ho
    A flipping coin on table will slow down and drop to the table surface, facing up or down. How can I calculate the flip-per-second declaration rate over time? For example, assuming the coin is at 10 flipping per second when it starts how long will it take to stop? For each second (9, 8, 7, 6 ... 3, 2, 1, stop), how is the flipping rate changed? Friction can be approximated as some real world objects (say, a metallic coin on a wooden table). Thanks!

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  • Slow loop in R, any suggestion to speed it up?

    - by cfceric
    I have a data frame "m" as shown below: I am trying to find each account's most active month (with most number of V1). for example for account "2", it will be "month 6", for account 3 it will be "month 1", .... I wrote the below loop, it works fine but just takes a long time even I only used 8000 rows, the whole data set has 250,000 rows, so the code below is not usable. Does any one can suggest a better way to achieve this? Thanks a lot.

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  • Can I play any Buffer only once at a given time?

    - by mystify
    From the OpenAL documentation: The basic OpenAL objects are a Listener, a Source, and a Buffer. There can be a large number of Buffers, which contain audio data. Each buffer can be attached to one or more Sources My problem is, that I have one sound file which I need to play multiple times per second, at the same time. The sound is 2 seconds long. So it will overlap. Would I need multiple filled buffers for this (= multiple times that sound in memory)? If I would attach one Buffer to multiple Sources, would I be able to play the sound 10 times, overlapping itself, with just one copy in memory? Or would I still have to deal with 10 copies of that sound in memory?

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  • extended permissions

    - by melimoreno
    Hi i'm doing a fb app that update the status box(what's in your mind), i'm using set_status from facebooker .. first i have this error: set_status needs extended permission so i google it and find this: before_filter :ensure_has_status_update .. so i put it in my controller and that solves the problem, but when i try to update the status, all ways redirect me to a fb page that says: You have already granted permissions to this application. so i go to the controller comment before_filter :ensure_has_status_update and then go to my app again and it works.. so i want to do this if (has_status_update == false) ask for permision else update the status i google it for a long time but i can't find an answer..

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  • PHP: How to get <br/> working in a simplexml_load_file() var.

    - by daviddarx
    Hi everybody! I am loading an xml in php via simplexml_load_file(). I load the file with that: $xml = simplexml_load_file('flash/datas/datas.xml'); And the access my content like that: $descText = $xml->aboutModule->chocolaterie->desc The text from desc is well registred in my $descText, but all the <br/> of the text disappear... So my long text is on a single line, not so good :-/ Do you know how to solve that? Is there a special traitement to do one the $xml var? Or someting else? Thank you in advance for your help!

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  • What is this VB6 method doing?

    - by Craig
    We are converting a VB6 application to C# (4.0). and have come across a method in VB6 that we're battling to understand. Public Sub SaveToField(fldAttach As ADODB.Field) Dim bData() As Byte Dim nSize As Long nSize = Len(m_sEmail) bData = LngToByteArray(nSize) fldAttach.AppendChunk bData If nSize > 0 Then bData = StringToByteArray(m_sEmail) fldAttach.AppendChunk bData End If nSize = Len(m_sName) bData = LngToByteArray(nSize) fldAttach.AppendChunk bData If nSize > 0 Then bData = StringToByteArray(m_sName) fldAttach.AppendChunk bData End If bData = LngToByteArray(m_nContactID) fldAttach.AppendChunk bData End Sub It seems like it's doing some binary file copy type thing, but I'm not quite understanding. Could someone explain so that we can rewrite it?

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  • Parallel.For(): Update variable outside of loop

    - by TSS
    I'm just looking in to the new .NET 4.0 features. With that, I'm attempting a simple calculation using Parallel.For and a normal for(x;x;x) loop. However, I'm getting different results about 50% of the time. long sum = 0; Parallel.For(1, 10000, y => { sum += y; } ); Console.WriteLine(sum.ToString()); sum = 0; for (int y = 1; y < 10000; y++) { sum += y; } Console.WriteLine(sum.ToString()); My guess is that the threads are trying to update "sum" at the same time. Is there an obvious way around it?

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