optimization

问题 A while back I used a PNG optimisation service called (I think) "smush it". You fed it a weblink and it returned a zip of all the PNG images with their filesizes nicely, well, smushed... I want to implement a similar optimisation feature as part of my website's image upload process; does anyone know of a pre-existing library (PHP or Python preferably) that I can tap into for this? A brief Google has pointed me towards several command line style tools, but I'd rather not go down that route if

问题 A while back I used a PNG optimisation service called (I think) "smush it". You fed it a weblink and it returned a zip of all the PNG images with their filesizes nicely, well, smushed... I want to implement a similar optimisation feature as part of my website's image upload process; does anyone know of a pre-existing library (PHP or Python preferably) that I can tap into for this? A brief Google has pointed me towards several command line style tools, but I'd rather not go down that route if

问题 What is the fastest way (in terms of cpu cycles on common modern architecture), to produce a mask with len bits set to 1 starting at position pos : template <class UIntType> constexpr T make_mask(std::size_t pos, std::size_t len) { // Body of the function } // Call of the function auto mask = make_mask<uint32_t>(4, 10); // mask = 00000000 00000000 00111111 11110000 // (in binary with MSB on the left and LSB on the right) Plus, is there any compiler intrinsics or BMI function that can help?

问题 I was browsing Google Code when I chanced upon this project called JSpeed - optimization for Javascript. I noticed one of the optimization was to change i++ to ++i in for loop statements. Before Optimization for (i=0;i<1;i++) {} for (var i = 0, j = 0; i < 1000000; i++, j++) { if (i == 4) { var tmp = i / 2; } if ((i % 2) == 0) { var tmp = i / 2; i++; } } var arr = new Array(1000000); for (i = 0; i < arr.length; i++) {} After optimization for(var i=0;i<1;++i){} for(var i=0,j=0;i<1000000;++i,++j

问题 I was browsing Google Code when I chanced upon this project called JSpeed - optimization for Javascript. I noticed one of the optimization was to change i++ to ++i in for loop statements. Before Optimization for (i=0;i<1;i++) {} for (var i = 0, j = 0; i < 1000000; i++, j++) { if (i == 4) { var tmp = i / 2; } if ((i % 2) == 0) { var tmp = i / 2; i++; } } var arr = new Array(1000000); for (i = 0; i < arr.length; i++) {} After optimization for(var i=0;i<1;++i){} for(var i=0,j=0;i<1000000;++i,++j

问题 I have a large number of independent tasks I would like to run, and I would like to distribute them on a parallel system such that each processor does the same amount of work, and maximizes my efficiency. I would like to know if there is a general approach to finding a solution to this problem, or possibly just a good solution to my exact problem. I have T=150 tasks I would like to run, and the time each task will take is t=T. That is, task1 takes 1 one unit of time, task2 takes 2 units of

问题 Yesterday I asked a question about least square optimization in R and it turned out that lm function is the thing that I was looking for. On the other hand, now I have an other least square optimization question and I am wondering if lm could also solve this problem, or if not, how it can be handled in R. I have fixed matrices B (of dimension n x m) and V (of dimension n x n), I am looking for an m -long vector u such that sum( ( V - ( B %*% diag(u) %*% t(B)) )^2 ) is minimized. 回答1: 1) lm

问题 I have a query joining lots of fields. For some strange reason the index for one table is not being used at all( I use the index key clearly), instead it is doing a FULL table scan. I would like to force the index. We used to do optimizer hints in sybase. Is there a similar hint available in oracle? For example, in sybase to join tables a, b, c and use myindex in table a, I would do : SELECT a.* FROM a(INDEX myindex), b, c WHERE a.field1 = b.field1 AND b.field1 = c.field1 Question is how do I

问题 I have a query joining lots of fields. For some strange reason the index for one table is not being used at all( I use the index key clearly), instead it is doing a FULL table scan. I would like to force the index. We used to do optimizer hints in sybase. Is there a similar hint available in oracle? For example, in sybase to join tables a, b, c and use myindex in table a, I would do : SELECT a.* FROM a(INDEX myindex), b, c WHERE a.field1 = b.field1 AND b.field1 = c.field1 Question is how do I

问题 The data below is being used to perform comparative analysis. I wrote the code using apply() and while() , and even though it works as expected, I haven't been successful in optimizing it further. Current run time is more than couple of hours in larger data set. Following is small example data set: data_1 A B C D 2 1 3 2.5 data_2 P Q R S 3 2 4 5.5 Data A B C D 1.0 0.5 1.3 1.5 1.5 1.2 5.5 3.5 1.1 0.5 1.3 1.5 1.5 1.2 5.5 3.5 1.5 1.2 5.5 3.5 1.1 0.5 1.3 1.5 1.5 1.2 5.5 3.5 1.0 0.5 1.3 1.5 Code #