comparison

问题 I'm looking for an algorithm (ideally a C/C++ implementation) that calculates perceived similarity between two images, taking into account psychovisual factors (e.g. that difference in chroma is not as bad as difference in brightness). I have original image and multiple variations of it (256-color quantisations in my case) and I'd like algorithm to find which image a human would judge as the best one. The best I've found so far is SSIM, but it doesn't "understand" dithering (error diffusion)

问题 Is there an operand/function/command in MySQL similar to the EXCEPT operand in SQL Server? EXCEPT returns any distinct values from the left query that are not also found on the right query. This statement should give me the distinct values. SELECT * FROM table1 EXCEPT SELECT * FROM table2; How can this be achieved in MySQL? 回答1: The best you could do is use a NOT EXISTS . Something like: SELECT DISTINCT * FROM table1 WHERE NOT EXISTS(SELECT NULL FROM table2 WHERE table1.x = table2.x) 来源：

问题 When looking at Ext JS, I don't get the feeling that it's meant for the same things as jQuery and Mootools. Whilst jQuery and Mootools help with the general workings of a site, Ext JS seems to be focussed on tables and storing data, plus manipulating it. So, is this observation correct, or is Ext Js fit for the same work as jQuery and Mootools? 回答1: Comparing ExtJs and JQuery is like comparing apples and oranges. You can compare Ext Core to JQuery, and ExtJs to JQuery UI. Ext Core and ExtJs

问题 Can we compute a sort of distance between regular expressions ? The idea is to mesure in which way two regular expression are similar. 回答1: There are a few of metrics you could use: The length of a valid match. Some regexs have a fixed size, some an upper limit and some a lower limit. Compare how similar their lengths or possible lengths are. The characters that match. Any regex will have a set of characters a match can contain (maybe all characters). Compare the set of included characters.

问题 In one bit of code I'm working on, I need to pull a value from the database and check if it is 0 . Originally, I had written this as: if ($myVal == 0) { ... But when I looked at it again today, I realised a bug there: var_dump("foo" == 0); // bool(true) // and while we're here... var_dump(intval("foo")); // int(0) Since this value is coming from the database, that usually means it will be a string, so I suppose I could do this: if ($myVal === "0") but it seems counter-intuitive since I

问题 python decimal comparison >>> from decimal import Decimal >>> Decimal('1.0') > 2.0 True I was expecting it to convert 2.0 correctly, but after reading thru PEP 327 I understand there were some reason for not implictly converting float to Decimal, but shouldn't in that case it should raise TypeError as it does in this case >>> Decimal('1.0') + 2.0 Traceback (most recent call last): File "<string>", line 1, in <string> TypeError: unsupported operand type(s) for +: 'Decimal' and 'float' so does

问题 I have only created regular windows applications (C# mostly). What differentiates a windows service from a regular windows application? What makes them different? What can a service do that an application can't? What are the differences seen from a developers point of view? How do you create one? Is it just to create a regular application (Console application maybe, since there are no gui?) and run or install it in a special way, or is it more that has to be done? 回答1: There are a couple of

问题 In R, if you test a condition on a vector instead of a scalar, it will return a vector containing the result of the comparison for each value in the vector. For example... > v <- c(1,2,3,4,5) > v > 2 [1] FALSE FALSE TRUE TRUE TRUE In this way, I can determine the number of elements in a vector that are above or below a certain number, like so. > sum(v > 2) [1] 3 > sum(v < 2) [1] 1 Does anyone know how I can determine the number of values in a given range? For example, how would I determine

问题 I have millions of fixed-size (100) int arrays. Each array is sorted and has unique elements. For each array, I want to find all arrays which have 70% common elements. Right now I am getting around 1 million comparisons (using Arrays.binarySearch()) per second, which is too slow for us. Can anyone recommend a better searching algorithm? 回答1: Something like this should do the job (provided that the arrays are sorted and contain unique elements): public static boolean atLeastNMatchingElements

问题 I have a twig template where I would like to test if an item begins with a certain value {% if item.ContentTypeId == '0x0120' %} <td><a href='?parentId={{ item.Id }}'>{{ item.BaseName }}</a><br /></td> {% else %} <td><a href='?{{ item.UrlPrefix }}'>{{ item.LinkFilename }}</a></td> {% endif %} The 0x0120 can look like that or be more complex like this 0x0120D52000D430D2B0D8DD6F4BBB16123680E4F78700654036413B65C740B168E780DA0FB4BX. The only thing I want to do is to ensure that it starts with the