inverse | 易学教程

inverse=true in JPA annotations

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In my application I use JPA 2.0 with Hibernate as the persistence provider. I have a one-to-many relationship between two entities (using a @JoinColumn and not @JoinTable ). I wanted to know how could I specify inverse=true (as specified in hbm.xml ) in JPA annotations to reverse the relationship owner. Thank you. I found an answer to this. The mappedBy attribute of @OneToMany annotation behaves the same as inverse = true in the xml file. The attribute mappedBy indicates that the entity in this side is the inverse of the relationship, and the owner resides in the other entity. Other entity

Matrix inversion without Numpy

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问题 I want to invert a matrix without using numpy.linalg.inv . The reason is that I am using Numba to speed up the code, but numpy.linalg.inv is not supported, so I am wondering if I can invert a matrix with 'classic' Python code. With numpy.linalg.inv an example code would look like that: import numpy as np M = np.array([[1,0,0],[0,1,0],[0,0,1]]) Minv = np.linalg.inv(M) 回答1: Here is a more elegant and scalable solution, imo. It'll work for any nxn matrix and you may find use for the other

Solving for the inverse of a function in R

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问题 Is there any way for R to solve for the inverse of a given single variable function? The motivation is for me to later tell R to use a vector of values as inputs of the inverse function so that it can spit out the inverse function values. For instance, I have the function y(x) = x^2 , the inverse is y = sqrt(x) . Is there a way R can solve for the inverse function? I looked up uniroot() , but I am not solving for the zero of a function. Any suggestions would be helpful. Thanks! 回答1: What kind

Inverse fourier transformation in OpenCV

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问题 I am new in OpenCV and image processing algorithms. I need to do inverse discrete fourier transformation in OpenCV in C++, but I don't know how. I searched over internet and I didn't find answer. I am doing fourier transformation in my program with this code from this page: http://opencv.itseez.com/doc/tutorials/core/discrete_fourier_transform/discrete_fourier_transform.html. I have tried to do inverse to that code, but I don't know where I am doing wrong. My code is here (I think that whole

notepad++ Inverse Regex replace (all but string)

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问题 I essentially wish to match every line that DOES NOT contain this string "Hello" Example: sdfsdoifdoskf fdgokfdghodfkg hello fdojgohdfgjkdfg gfobjobhkdfokgdfg dofjkdsf hello dfgkdfogdfg xcvmxhckvmxck fogkdfhokg hello I attempted this Regex pattern : ^((?!hello).)*$ No matches found. Basically i want to remove every line that does not contain the string "hello" using notepad++ 回答1: ^((?!hello).)*$ works in Notepad++ 6. I wonder if it's better than this: ^(?!.*hello).*$ 回答2: the new Version (I

Compile-time map and inverse map values

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问题 Can someone recommend a more elegant way to achieve these compile-time constants? template <int> struct Map; template <> struct Map<0> {static const int value = 4;}; template <> struct Map<1> {static const int value = 8;}; template <> struct Map<2> {static const int value = 15;}; template <int> struct MapInverse; template <> struct MapInverse<4> {static const int value = 0;}; template <> struct MapInverse<8> {static const int value = 1;}; template <> struct MapInverse<15> {static const int

inverse=true in JPA annotations

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问题 In my application I use JPA 2.0 with Hibernate as the persistence provider. I have a one-to-many relationship between two entities (using a @JoinColumn and not @JoinTable ). I wanted to know how could I specify inverse=true (as specified in hbm.xml ) in JPA annotations to reverse the relationship owner. Thank you. 回答1: I found an answer to this. The mappedBy attribute of @OneToMany annotation behaves the same as inverse = true in the xml file. 回答2: The attribute mappedBy indicates that the

When to use inverse=false on NHibernate / Hibernate OneToMany relationships?

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问题 I have been trying to get to grips with Hibernate\'s inverse attribute, and it seems to be just one of those things that is conceptually difficult. The gist that I get is that when you have a parent entity (e.g. Parent) that has a collection of Child objects using a one-to-many mapping, setting inverse=true on the mapping tells Hibernate that \'the other side (the Child) has responsibility to update itself to maintain the foreign key reference in its table\'. Doing this appears to have 2

What is the difference between cascade & inverse in hibernate, what are they used for?

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问题 How to use cascade and inverse in hibernate? What is the procedure/tag to define them? Are they related to each other and how are they useful? 回答1: In case of many-to-many relation through intermediary table; "Cascade" says whether a record will be created/updated in the child table. Whereas "Inverse" says whether a record will be created/updated in the intermediary table e.g. Assume below scenario 1 student can have multiple phones. So Student class has property for Set of phones. Also 1