operations

问题 I am doing geoquery among 300 user entities with a result range 10. I've maked a query for 120 times. For each query I got 10 user entity objects. After this my app engine read operations reached 52% (26000 operations). My user entity has 12 single value properties and 3 multi-value properties(List type). User entity have 2 indexes for single value properties and 2 indexes on list type properties. Can any one please help me to understand how google's appengine counts the datastore read

问题 I am learning threading.My intension is to pass some values to a method for calculation,if the result will not be returned within 20 ms,i will report "Operation timeout".Based on my understading i have implemented the code as follows: public delegate long CalcHandler(int a, int b, int c); public static void ReportTimeout() { CalcHandler doCalculation = Calculate; IAsyncResult asyncResult = doCalculation.BeginInvoke(10,20,30, null, null); if (!asyncResult.AsyncWaitHandle.WaitOne(20, false)) {

问题 Using Python, I have two large (equally long) files in which the numbers are divided by spaces: 0.11158E-13 0.11195E-13 0.11233E-13 ... # file1 0.11010E-13 0.11070E-13 0.11117E-13 ... # file2 There are differences in the values and I would like to get the relative differences and writing them in the same format into a third file. I can do it for the first value but have problem when it comes to ITERATING the process (so that all values are computed). This is the code (I am new to the python

问题 I looked for good methods to do popcount (count of set bits). I found this one, here http://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetKernighan unsigned int v; // count the number of bits set in v unsigned int c; // c accumulates the total bits set in v for(c = 0; v; c++) { v &= v - 1; // clear the least significant bit set } Trying on a few examples, its true that it works. What property of binary operations / representation makes it work? Could you hint at some further

问题 This question already has answers here : R fill vector efficiently (4 answers) Closed 2 years ago . I have a vector of zeros, say of length 10. So v = rep(0,10) I want to populate some values of the vector, on the basis of a set of indexes in v1 and another vector v2 that actually has the values in sequence. So another vector v1 has the indexes say v1 = c(1,2,3,7,8,9) and v2 = c(0.1,0.3,0.4,0.5,0.1,0.9) In the end I want v = c(0.1,0.3,0.4,0,0,0,0.5,0.1,0.9,0) So the indexes in v1 got mapped

问题 I'm trying to perform computations involving matrix operations and complex math - sometimes together, in C. I'm very familiar with Matlab and I know these types of computations could be performed simply and efficiently. For example, two matrices of the same size, A and B, each having elements of complex values can be summed easily through the expression A+B. Are there any packages or techniques that can be recommended to employ programming these types of expressions in C or Objective C? I am

问题 I am trying to delete both a matrix in mathematica. An inelegant way of doing it is as I do below, i.e specifying it in a new matrix as S = Table[ Ss[[If[i < t, i, i + 1]]][[If[j < t, j, j + 1]]], {i, q}, {j, q}]; where the goal is to eliminate row and column t. Indeed delete a line is easy Delete[Ss,t]. For the column column I suppose I could do Transpose[Delete[Transpose[Ss,t]]] My primary concern is to do it in a way that executes the fastest way possible. More generally, is there a

问题 I am looking at solution for the set bit count problem (given a binary number, how to efficiently count how many bits are set). Here, http://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetNaive, I have found some methods. What about the lookup table method? I dont understand what properties of binary representation / number make it work. static const unsigned char BitsSetTable256[256] = { # define B2(n) n, n+1, n+1, n+2 # define B4(n) B2(n), B2(n+1), B2(n+1), B2(n+2) # define B6(n)

问题 This question already has answers here : Multiplying Combinations of a list of lists in R (4 answers) Closed 3 years ago . What I'm trying to do: Multiply an object in a list by another object in a different list? I need to multiply a vector of 1000 values in List A times a vector of 1000 values in List B. For instance: Vector in List_A: 1 2 3 Vector in List_B: 4 5 6 Output vector I want, List_A*B: 4 10 18 I found something called multiply.list() in the {lgcp} package but apparently not all

问题 I have created a simple calculator that calculates two inputs (ex. 2 + 2 = 4). What I want to do now is to make the app to calculate multiple operations like (ex. 2 + 2 * 4 - 1 = 15). Can someone help me with my code? Here is my code. public class MainActivity extends Activity { public String str =""; Character op = 'q'; int i,num,numtemp; EditText showResult; String displayStr = ""; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView