Bugzilla – Bug 157

add *, /, *=, /= to VectorwiseOp

Last modified: 2011-11-18 20:06:36 UTC

They make sense at least for Array. What I want to do is divide each row of rho by its sum: MatrixXf rho(n, m), r(n, m); r = rho.array().colwise() / rho.rowwise().sum().array(); and I don't see how to do it without a loop. Thanks.

You can do that with .replicate(): r = rho.array().colwise() / rho.rowwise().sum().array().replicate(n,1); I think this should work as well: r = rho.array().colwise() / rho.rowwise().sum().array().colwise().replicate(n); But yes, me too I miss that feature a lot as it enables code to be a lot more concise.

*** Bug 374 has been marked as a duplicate of this bug. ***

Summary: From the tutorial, http://eigen.tuxfamily.org/dox/TutorialReductionsVisitorsBroadcasting.html mat.colwise() += v; //works mat.colwise() -= v; //works mat.colwise() *= v; //not implemented mat.colwise() /= v; //not implemented Moreover, mat2 = mat.colwise() + v; //works mat2 = mat.colwise() - v; //works mat2 = mat.colwise() * v; //not implemented mat2 = mat.colwise() / v; //not implemented mat2 = v + mat.colwise(); //not implemented mat2 = v - mat.colwise(); //not implemented mat2 = v * mat.colwise(); //not implemented mat2 = v / mat.colwise(); //not implemented

In addition, Eigen::ArrayXf v(2); v = 3/v; //not implemented

Created attachment 229 [details] Fixed VectorwiseOp.h Here is the fixed VectorwiseOp.h. but need to implement operations for rhs VectorwiseOp. But I think that should be somewhere else, not this file.

*** Bug 151 has been marked as a duplicate of this bug. ***

Created attachment 230 [details] [review] this patch implements some of the operators. this patch implements some of the operators. Eigen::MatrixXf mat(2,4); Eigen::ArrayXf v(2); mat.colwise() += v; //works mat.colwise() -= v; //works mat.colwise() *= v; //not implemented -> now implemented mat.colwise() /= v; //not implemented -> now implemented mat2 = mat.colwise() + v; //works mat2 = mat.colwise() - v; //works mat2 = mat.colwise() * v; //not implemented -> now implemented mat2 = mat.colwise() / v; //not implemented -> now implemented mat2 = v + mat.colwise(); //not implemented mat2 = v - mat.colwise(); //not implemented mat2 = v * mat.colwise(); //not implemented mat2 = v / mat.colwise(); //not implemented v = 3 / v; //not implemented -> now implemented

Comment on attachment 230 [details] [review] this patch implements some of the operators. Review of attachment 230 [details] [review]: ----------------------------------------------------------------- First, such / operators should be available only in array mode. Otherwise they make no sense to me. The correct way of doing this with linear algebra objects is, e.g.: C = A * v.diagonal().inverse(); Second, the documentation should mention that these functions are actually equivalent to matrix * diagonal matrix products: C = A * v.diagonal(); <=> rowwise vector multiply C = A * v.diagonal().inverse(); <=> rowwise vector divison

Comment on attachment 230 [details] [review] this patch implements some of the operators. Review of attachment 230 [details] [review]: ----------------------------------------------------------------- 1. I also think that / operator should be only available for array mode. (but can you teach me how it can be done in a correct way? I'm still learning the library structure and it's not so easy) 2. C = A / v //newly implemented operator C = A * v.diagonal().inverse(); //equivalent? seems your example will work for a scalar A and "ArrayXf v;" but how about for "ArrayXXf v;" ?

The relevant part of the class hierarchy is: - DenseBase is the common base class for all dense matrix and array expressions - MatrixBase inherits DenseBase, is the common base class for Matrix expressions - ArrayBase inherits DenseBase, is the common base class for Array expressions

(In reply to comment #9) For your point 2, the equivalents I shown are for the matrix world only where v is a vector, and it is not equivalent to C = A/v but C = A.rowwise() / v where v also has to be a vector.

This whole area is really a mess. I propose that we: 1) take Kibeom's patch adding multiplicative vectorwise ops 2) add lots of static assertions making it very explicit when all these ops are supposed to work: 2a) additive ops already require that the lhs and rhs are of the same kind (matrix vs vector) 2b) multiplicative ops (as in Kibeom's patch) also pretty much have to be restricted to arrays (enabling them for matrices would require a complex dance with .array()/.matrix() which would be fine for *= and /= but would force * and / to return very deeply nested expressions. 3) add unit tests. there just aren't enough unit tests here. currently, additive ops are only tested in array.cpp on arrays as far as I can see.

oh and: 4) this stuff: for(Index j=0; j<subVectors(); ++j) subVector(j).array() *= other.derived().array(); is not the right way, is it? In operator + we return a sum with the extendedTo() expression. I suppose that there is no reason for a custom for loop here.

(I mean, this problem preexists, it's what += and -= do. I'm criticizing existing code, not Kibeom's patch)

Pushed Kibeom's patch: 13f72ac8283d Pushed another patch implementing my proposal in comment 12 and comment 13, as well as adding a new unit test, vectorwiseop.cpp: d48a7c25e052

I suggest to define rowwise() and colwise() like this. "something.rowwise() [operator] other" as "something.row(k) [operator] other for all k" because this is a better way to define the function cleanly and consistently. so for example, 1. "array.rowwise() * v" should equal to "array.row(k) * v for all k" 2. "mat.rowwise() * v" should equal to "mat.row(k) * v for all k" (notice that this is just mat * v) so for the implementation, VectorwiseOp will hands over all the actual operations to an underlying object, array or matrix.

The problem is that for a matrix, "mat.row(k) * v" gives a 1x1 result, containing the real dot product of mat.row(k) with v. But many people would expect rowwise to behave like it does for arrays. So I'm afraid that this would only add confusion. Moreover, for a matrix, "mat.row(k) * v for all k" is already available: that's just the matrix-vector product, mat*v.

actually, I think either approach is fine. (although I prefer "mat.row(k) * v for all k" = mat*v slightly more) But whatever, I think having a simple generalized statement of what rowwise() actually does is good. How about this? "something.rowwise() [operator] other" is conceptually identical to "something.array().row(k) [operator] other for all k" and then we can pass all the VectorwiseOp's operator implementations to "array.row() [operator] other".