问题描述
我正在和Eigen一起使用矩阵和log/exp进行一些计算，但是我发现表达式有点笨拙(可能还会更慢?).有没有更好的方法来编写这样的计算?
I am playing around with Eigen doing some calculations with matrices and logs/exp, but I found the expressions I got a bit clumsy (and also possibly slower?). Is there a better way to write calculations like this ?
MatrixXd m = MatrixXd::Random(3,3);
m = m * (m.array().log()).matrix();
也就是说，不必转换为数组，然后返回矩阵?
That is, not having to convert to arrays, then back to a matrix ?
推荐答案
如果您要混合使用数组和矩阵运算，就不能真正避免使用它们，除非某些函数具有 cwise 函数，直接在矩阵上工作(例如， cwiseSqrt()， cwiseAbs()).
If you are mixing array and matrix operations you can't really avoid them, except for some functions which have a cwise function which works directly on matrices (e.g., cwiseSqrt(), cwiseAbs()).
但是，当使用优化(在任何合理的编译器上)编译时， .array()和 .matrix()都不会对运行时产生影响.如果您认为这样更具可读性，则可以使用 unaryExpr() .
However, neither .array() nor .matrix() will have an impact on runtime when compiled with optimization (on any reasonable compiler).If you consider that more readable, you can work with unaryExpr().
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