optimization

问题 I have a sheet in Excel which contains a lot of numbers to varying decimal places. I'm trying to create a table in MySQL to store this data as efficiently as possible, but I need to know the highest number of decimal places in each column. Is there a function which I can use to work this out? My dataset looks something like this: Item | Val 1 | Val 2 | Val 3 =====|=======|=======|======= 1 | x.xxx | x.xx | xx.xx ... | x.xx | x.x | xx.xxx n | xx.x | x.xx | xx.xx For example, in the Val 1

问题 I have a sheet in Excel which contains a lot of numbers to varying decimal places. I'm trying to create a table in MySQL to store this data as efficiently as possible, but I need to know the highest number of decimal places in each column. Is there a function which I can use to work this out? My dataset looks something like this: Item | Val 1 | Val 2 | Val 3 =====|=======|=======|======= 1 | x.xxx | x.xx | xx.xx ... | x.xx | x.x | xx.xxx n | xx.x | x.xx | xx.xx For example, in the Val 1

问题 The bounty expires in 4 days . Answers to this question are eligible for a +100 reputation bounty. Khawar Islam is looking for an answer from a reputable source . The identities list contains an big array of approximately 57000 images . Now, I am creating a negative list with the help of itertools.product() . This store the whole list in memory which is very costly and my system hanged after 4 minutes. How can i optimize the below code and avoid saving in memory?` for i in range(0, len

问题 I'm profiling an application using Intel VTune, and there is one particular hotspot where I'm copying a __m128i member variable in the copy constructor of a C++ class. VTune gives this breakdown: Instruction CPU Time: Total CPU Time: Self Block 1: vmovdqa64x (%rax), %xmm0 4.1% 0.760s add $0x10, %rax 46.6% 8.594s Block 2: vmovapsx %xmm0, -10x(%rdx) 6.5% 1.204s (If it matters, compiler is gcc 7.4.0) I admit I'm an assembly noob, but it's very surprising that one particular add instruction is

问题 I'm wondering if there is a generalisation of solver.AllDifferent(x) in google or-tools that allows for the specification of how many different elements I allow. So if len(x) = 4, then AllDifferent(x) means that len(set(x)) = 4. But what if I just want to enforce "at least 2 different", so: len(set(x)) >=2 ? Is there a constraint that generalises AllDifferent to be able to set the cardinality of the solution variable ? 来源： https://stackoverflow.com/questions/48021694/make-k-different

问题 I am using a Kalman filter to estimate various Dynamic and Arbitrage free Nelson-Siegel models for yield curves. I give some starting values to optim and the algorithm converges just fine. However, when I want to calculate standard errors using the Hessian supplied by the optim algorithm, I get NaN's due to nonpositive values on the diagonal of the Variance covariance matrix. I think it is because I have a highly nonlinear function with many local optima, however it keeps happening for all

问题 I would like to know what precisely is happening since php script runs the query to the moment when database returns data and php script starts to fetch them. In theory, I have a Postgre database with huge table, talking about 10/20 million records with 20+ columns and I have a php script which is requesting all that rows from database to be placed in, lets say, some file. My knowledge is: php script runs the pg_query command with sql query through postgres php driver/extension query is

问题 I would like to know what precisely is happening since php script runs the query to the moment when database returns data and php script starts to fetch them. In theory, I have a Postgre database with huge table, talking about 10/20 million records with 20+ columns and I have a php script which is requesting all that rows from database to be placed in, lets say, some file. My knowledge is: php script runs the pg_query command with sql query through postgres php driver/extension query is

问题 im working on a pdf generator app in flutter, but when i want to add an image to the pdf, it takes too long also i wanted to know how it is possible to add multiple images. Im using 3 libraries, image picker - pdf - printing here is my code: Future getImage() async { var image = await ImagePicker.pickImage(source: ImageSource.gallery); final tempDir = await getTemporaryDirectory(); final path = tempDir.path; int rand = new Math.Random().nextInt(10000000); imge.Image imagee = imge.decodeImage

问题 I'm optimizing a Python program that performs some sort of calculation. It uses NumPy quite extensively. The code is sprinkled with logger.debug calls (logger is the standard Python log object). When I run cProfile I see that Numpy's function that converts an array to string takes 50% of the execution time. This is surprising, since there is no handler that outputs messages as the DEBUG level, only INFO and above. Why is the logger converting its arguments to string even though nobody is