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  • Fast modulo 3 or division algorithm?

    - by aaa
    Hello is there a fast algorithm, similar to power of 2, which can be used with 3, i.e. n%3. Perhaps something that uses the fact that if sum of digits is divisible by three, then the number is also divisible. This leads to a next question. What is the fast way to add digits in a number? I.e. 37 - 3 +7 - 10 I am looking for something that does not have conditionals as those tend to inhibit vectorization thanks

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  • Spatial Index for Rectangles With Fast Insert

    - by TheCloudlessSky
    Hello, I'm looking for a data structure that provides indexing for Rectangles. I need the insert algorithm to be as fast as possible since the rectangles will be moving around the screen (think of dragging a rectangle with your mouse to a new position). I've looked into R-Trees, R+Trees, kD-Trees, Quad-Trees and B-Trees but from my understanding insert's are usually slow. I'd prefer to have inserts at sub-linear time complexity so maybe someone can prove me wrong about either of the listed data structures. I should be able to query the data structure for what rectangles are at point(x, y) or what rectangles intersect rectangle(x, y, width, height). EDIT: The reason I want insert so fast is because if you think of a rectangle being moved around the screen, they're going to have to be removed and then re-inserted. Thanks!

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  • iPhone: fast hash function for storing web images (url) as files (hashed filenames)

    - by Stefan Klumpp
    What is a fast hash function available for the iPhone to hash web urls (images)? I'd like to store the cached web image as a file with a hash as the filename, because I suppose the raw web url could contain strange characters that could cause problems on the file system. The hash function doesn't need to be cryptographic, but it definitely needs to be fast. Example: Input: http://www.calumetphoto.com/files/iccprofiles/icc-test-image.jpg Output: 3573ed9c4d3a5b093355b2d8a1468509 This was done by using MD5(), but since I don't know much about that topic I don't know if it is overkill (- slow).

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  • Hierarchical Data in MySQL is fast to retrieve?

    - by ajsie
    i've got a list of all countries - states - cities (- subcities/villages etc) in a XML file and to retrieve for example a state's all cities it's really quick with XML (using xml parser). i wonder, if i put all this information in mysql, is retrieving a state's all cities as fast as with XML? cause XML is designed to store hierarchical data while relational databases like mysql are not. the list contains like 500 000 entities. so i wonder if its as fast as XML using either of: Adjacency list model Nested Set model And which one should i use? Cause (theoretically) there could be unlimited levels under a state. And which is fastest for this huge dataset? Thanks!

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  • Fast dot product for a very special case

    - by psihodelia
    Given a vector X of size L, where every scalar element of X is from a binary set {0,1}, it is to find a dot product z=dot(X,Y) if vector Y of size L consists of the integer-valued elements. I suggest, there must exist a very fast way to do it. Let's say we have L=4; X[L]={1, 0, 0, 1}; Y[L]={-4, 2, 1, 0} and we have to find z=X[0]*Y[0] + X[1]*Y[1] + X[2]*Y[2] + X[3]*Y[3] (which in this case will give us -4). It is obvious that X can be represented using binary digits, e.g. an integer type int32 for L=32. Then, all what we have to do is to find a dot product of this integer with an array of 32 integers. Do you have any idea or suggestions how to do it very fast?

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  • Java: how to take a screenshot fast

    - by user350789
    I am implementing a simple eye tracker, which requires fast screenshoting of what is happening on the screen simultaneously with capturing the video from webcam. The thing is that the way of doing it with Robot, mentioned here: http://stackoverflow.com/questions/2475303/java-library-for-capturing-active-window-screenshot is extremely slow. By the way, retrieving the video from a webcam works much faster and returns the byte array, which is very fast to be processed. Does anybody know a faster solution? C++ libraries, which can be linked to Java for doing this may help as well. Thank you!

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  • Add subview (rows) fast to UIScrollView while scrolling

    - by tikhop
    I have UIScrollView with a lot of rows (~100) and I implemented dequeueReusableRow method for fast allocating and adding my subviews (rows). Everything work fine, but if I scroll very fast with decelerate some view don't added to scrollView on time only later. - (UIView *)dequeueReusableRow { UIView *view = [reusableRows anyObject]; if(view) { [[view retain] autorelease]; [reusableRows removeObject:view]; }else{ view = [[UIView alloc] init.... } return view; } - (void)addVisibleRows { UIView *row = [self dequeueReusableRow]; row.frame = .... [scrollView addSubview:row] } - (void)scrollViewDidScroll:(UIScrollView *)scrollView { [self addVisibleRows]; [self removeInvisibleRows]; } Please, don't propose me use UITableView because structure of accordion looks like: section - section -- section --- row - section section - row

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  • aspx page with gridview runs very fast in IE but 20% of the speed on Firefox

    - by frank2009
    Hi there I have a simple aspx page with some search options which queries an SQLEXpress database, and it is displayed in a gridview. For some reason, it runs lightning fast in IE but very slow in Firefox. It has very little code, a gridview a couple of images and a couple of textboxes and a search button. It was done with Expression Web so no additional code added. In production (not local) the speed is very noticiable when doing a search... IE displays the results almost instantly...Firefox might take 3-5 seconds. And everything else runs super fast as well in IE (update, delete etc). Is there a reason for this ? Thanks

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  • Oracle: error while trying to use formulas

    - by Yazeed
    I created an element with an input value of type "Day" , when i write a formula i get this error. Any idea what's wrong? APP-FF-33232: EATC_EXTRA_DAYS_ENTRY_EFFECTIVE_DATE_ENTRY_VALUE has null or not found allowed, but no default set specified. Cause: If a Database Item has null allowed, or not found allowed, then the item must also specify a default set to be used to provide default values in the event of these occurring. The item named has one of these conditions allowed, but the default set column in the FF_DATABASE_ITEMS table is null. Action: Please refer to your local support representative. -

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  • Microsft Jet oledb connection to excel loses formulae

    - by Saubhagya
    I have a dataset and I write it's values to an excel file using Microsoft Jet 4.0 Oledb provider. I want to put hyperlinks into the excel, for this I write "=HYPERLINK("http://www.abc.org/x.pdf")" in DS and then write it to excel. But when the excel is opened it prefixes a ' (quote/apostrophe) before the formula and there it comes as a text, not link. Can you help me removing that quote so that my excel file has hyperlinks instead of that as text? I need to use Microsoft Jet 4.0 provider (not excel component) as the client machine may or may not have MS-Excel installed on his machine.

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  • Minimum & Maximum Values in Crystal Reports 2008 Column

    - by GregD
    Say I have this column returned in a command for Crystal: deposit_no 123 130 125 124 126 127 128 129 and I need to have this in the report title: Includes deposits between 123 - 130 I've tried a running formula for minimum and maximum and they aren't returning the correct values no matter how I manipulate them. I've tried evaluate for every record, on change of the deposit_no field, etc. I have no grouping on this report. Edited to add: While I preferred to handle this on the CR side of things, I changed my command to include what mson wrote below. So technically, mson had the correct answer.

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  • How to add a field from a 2nd form?

    - by PowerUser
    Hi all. I'm modifying an existing Lotus view to include a field from another form. I first appended a new column and set it to the desired field. However, after I refreshed, the new column was blank even though I know it has data. I then updated the View Selection formula from: SELECT Form = "A" & StatusIndex < "06" to: SELECT (Form = "A"| Form = "B") & StatusIndex < "06" Still no luck. The view is refreshing successfully, but the new field is still blank. What else is there to add this new column to this view? This is my first time experimenting with Lotus, so if I seem to be missing some major concept, I probably am.

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  • excel vba: return values only if they are not present in current column

    - by every_answer_gets_a_point
    i have a column to which i am adding data from another column i would like to check whether that column has the data that i wish to add. can you help me wiht a formula that will tell me whether a certain value exists in the current column? please keep in mind it is a bit more complex than it sounds. currently i have this in the cell: =IF(OR(A3="ETG_C",A3="ETGC"),C3,"na") i would like to have something like this =IF(FIND(IF(OR(A2="ETG_C",A2="ETGC"),C2,"na"),K:K,1)," ",IF(OR(A2="ETG_C",A2="ETGC"),C2,"na")) another words, if the top value exists already, then add a blank space

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  • How can I calculate the sum of all positive integers less than n? [closed]

    - by Adrian Godong
    I have the following function: f(n) = f(n - 1) + (n - 1) f(0) = 0 n >= 0 I have n declared on column A, and need the result of f(n) on column B. I'm trying to find the Excel formula equivalent for this function. Sample Result: A | B --+-- 0 | 0 or: A | B --+-- 1 | 0 or: A | B --+-- 4 | 6 but never: A | B --+-- 0 | 0 1 | 0 2 | 1 ... The biggest problem is, I can't simulate the value of f(n - 1). So referencing the previous row like the above example is invalid. I'm almost sure the answer is trivial, I just can't find it.

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  • Excel - Counting unique values that meet multiple criteria

    - by wotaskd
    I'm trying to use a function to count the number of unique cells in a spreadsheet that, at the same time, meet multiple criteria. Given the following example: A B C QUANT STORE# PRODUCT 1 75012 banana 5 orange 6 56089 orange 3 89247 orange 7 45321 orange 2 apple 4 45321 apple In the example above, I need to know how many unique stores with a valid STORE# have received oranges OR apples. In the case above, the result should be 3 (stores 56089, 89247 and 45321). This is how I started to try solving the problem: =SUM(IF(FREQUENCY(B2:B9,B2:B9)>0,1)) The above formula will yield the number of unique stores with a valid store#, but not just the ones that have received oranges or bananas. How can I add that extra criteria?

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  • How to loop in excel without VBA or macros?

    - by Jeff
    Is there a better way for me to write this formula? Did some googling on "excel loops," but no luck. I don't have VBA or macros installed (it's not an option to install them, unfortunately). =IF('testsheet'!$C$1 <= 99,'testsheet'!$A$1,"") & IF('testsheet'!$C$2 <= 99, 'testsheet'!$A$2,"") & IF('testsheet'!$C$3 <= 99, 'testsheet'!$A$3,"") & ... and so on through !$C$40, !$A$40 ... As it is, I'll have to repeat the above code 40 times in each cell and I have over 200 cells which need the code. sniff I'm pretty good with PHP/SQL, but just learning Excel.

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  • Prevent Excel from evaluating unneeded expressions in OR()

    - by Wesley
    IF(OR(ISNA(MATCH(8,B10:B17,0)),MATCH(8,B10:B17,0)>8),"",...BLAH...) I understand how to fix this problem by rearranging my formula. I have it the way it is to show this point. You can see the OR() statement checks to see if the first MATCH() returns NA. When it does, OR() should automatically return TRUE and not evaluate the second MATCH() because conditions have been met for the OR() to return true no matter what other arguments there are. You'll notice that the first and second MATCH() functions do the same thing. What's happening is the entire function is returning NA because the second MATCH() is executing even though it doesn't have to, the OR() has been satisfied with one TRUE, therefore the function should return "". Is this a bug or is this intentional?

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  • OS X multiple use of same machine via VNC

    - by Hassan Syed
    I'm wondering if I can connect to my wife's mac via VNC while she is logged in herself. I wouldn't be surprised if this isn't possible, although the machinery should be there with "fast-user-switching" support. So, if I create a profile for myself and I log in (and enable the VNC server/sharing for my profile), and then my wife switches to her own account which she uses on the physical console. Will I be able to use the mac ?

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  • Optimal storage of data structure for fast lookup and persistence

    - by Mikael Svenson
    Scenario I have the following methods: public void AddItemSecurity(int itemId, int[] userIds) public int[] GetValidItemIds(int userId) Initially I'm thinking storage on the form: itemId -> userId, userId, userId and userId -> itemId, itemId, itemId AddItemSecurity is based on how I get data from a third party API, GetValidItemIds is how I want to use it at runtime. There are potentially 2000 users and 10 million items. Item id's are on the form: 2007123456, 2010001234 (10 digits where first four represent the year). AddItemSecurity does not have to perform super fast, but GetValidIds needs to be subsecond. Also, if there is an update on an existing itemId I need to remove that itemId for users no longer in the list. I'm trying to think about how I should store this in an optimal fashion. Preferably on disk (with caching), but I want the code maintainable and clean. If the item id's had started at 0, I thought about creating a byte array the length of MaxItemId / 8 for each user, and set a true/false bit if the item was present or not. That would limit the array length to little over 1mb per user and give fast lookups as well as an easy way to update the list per user. By persisting this as Memory Mapped Files with the .Net 4 framework I think I would get decent caching as well (if the machine has enough RAM) without implementing caching logic myself. Parsing the id, stripping out the year, and store an array per year could be a solution. The ItemId - UserId[] list can be serialized directly to disk and read/write with a normal FileStream in order to persist the list and diff it when there are changes. Each time a new user is added all the lists have to updated as well, but this can be done nightly. Question Should I continue to try out this approach, or are there other paths which should be explored as well? I'm thinking SQL server will not perform fast enough, and it would give an overhead (at least if it's hosted on a different server), but my assumptions might be wrong. Any thought or insights on the matter is appreciated. And I want to try to solve it without adding too much hardware :) [Update 2010-03-31] I have now tested with SQL server 2008 under the following conditions. Table with two columns (userid,itemid) both are Int Clustered index on the two columns Added ~800.000 items for 180 users - Total of 144 million rows Allocated 4gb ram for SQL server Dual Core 2.66ghz laptop SSD disk Use a SqlDataReader to read all itemid's into a List Loop over all users If I run one thread it averages on 0.2 seconds. When I add a second thread it goes up to 0.4 seconds, which is still ok. From there on the results are decreasing. Adding a third thread brings alot of the queries up to 2 seonds. A forth thread, up to 4 seconds, a fifth spikes some of the queries up to 50 seconds. The CPU is roofing while this is going on, even on one thread. My test app takes some due to the speedy loop, and sql the rest. Which leads me to the conclusion that it won't scale very well. At least not on my tested hardware. Are there ways to optimize the database, say storing an array of int's per user instead of one record per item. But this makes it harder to remove items.

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  • WinSat command line closes too fast

    - by Rob Cowell
    I'm trying to do some analysis under Windows 7 as to why I can't get a Windows Experience Index (WEI) rating due to disk issues. To this end, I'm trying to run winsat from the command line with :- winsat disk -seq -read -drive c and winsat disk -ran -write -n 2 but the command window is closing too quickly to be able to read the results. I've tried opening a seperate cmd window to run it in but it still insists on launching its own window to run in, closing straight away. Any idea how I can see the output?

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  • Slow Browsing/Direct Download, but Fast Bittorrent Download

    - by Dr Haisook
    I'm using Windows XP SP2. I have a 1 MB connection via a SpeedTouch 585, and my internet speed registers at 0.3 MB, with a maximum download of 30kbps. Not to mention a terrible ping at 500-1500. On the other hand, I get full speed in uTorrent - a bittorrent program - reaching up to 100 kbps; the way it should be. I haven't made any changes to anything. And it has been functioning well until the last month. I waited in hope that it could be an ISP issue and that it would be resolved, but their support crew did not help me with this problem either. I've tried disabling all firewalls, and all wireless connections, using different browsers, and disabling QoS. But it did not work. Me thinks it's an ISP issue, but if so, how am I getting full speed in uTorrent? Could somebody help me out with this? Thanks.

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  • spawn-fcgi/ fast CGi php crashes without traces in logs, on Gentoo

    - by user39046
    Hello, I recently moved from apache to a Nginx/fastcgi solution, I had it running on a Fedora system and had no problems, but, since i moved all to Gentoo , the Spawn-fCGI / fastcgi php daemon dies, and i can't find out any errors reports on /var/log/messages , so i don't know why this happens. I've seen that fastcgi is somehow different from the fedora distro, on gentoo as it has different conf files and init.d startup scripts, Can someone help me make it more stable? The number of requests that i had isn't any different from the ones I had on fedora, so i use the default conf that comes with the distro..and in about some hours it simply dies... Thank you very much

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  • Lightning strike causes fast download?

    - by blaine
    Ok, REALLY strange question. My friend says he was downloading a 14 GB file at about 1 mb/s when suddenly there was a lightning strike outside and momentarily the download speed jumped to 10,000,000 GB/s. The file finnished downloading. He even has the screenshot to prove it. I also trust him and don't believe that he would be lying. So my question is: how is this even possible?? Is there just the possibility that the file was about to finish downloading anyway and the lightning strike coincided with a freak download speed calculation error?

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