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yixuan
Discussion on future development of Spectra
This thread is used to discuss the future development of Spectra. I would be glad to hear your voice about how this library would look like in the next few major versions.
Let me first outline what I have in mind so far:
- The first thing I want to do is to remove the
SelectionRuletemplate parameter from all eigen solvers, as suggested by @wo80 in #61. I don't see obvious disadvantage of this change, except that it breaks the current API, which I will discuss below. On the other hand, the benefit is clear: it makes wrappers of Spectra (including my own RSpectra R package) much cleaner, and allows you to use multiple selection rules in one program without compiling the whole solver many times. - I tend to adopt newer C++ standards, e.g. C++11, in future development of Spectra. Honestly speaking I don't have much programming experience on the new standards, but recently I started to learn and expect that some features of C++11 can improve the quality of the code.
- At least some basic support for complex-valued matrices should be added to Spectra. This was requested many times in GitHub Issues.
- Other iterative eigen solvers may be added to Spectra also, for example Jacobi-Davidson, as suggested in #87. How to unify the API is something we need to figure out. @JensWehner
About backward compatibility: I believe this is a headache for virtually every open source library, but I tend to be "aggressive" on this aspect. Personally I treat Spectra mostly as a research project, and I want to quickly drop poor designs and outdated features. In fact I have already broken the API several times (changelog).
My plan is to maintain the current API at version 0.9.x, and develop all new features in 1.y.z+. One thing I'm not familiar with is the consequence to community-maintained packages such as Conda. Any thoughts on this? @guacke @jschueller
Other thoughts/suggestions? Please feel free to leave your comments below.
About compatibility, I agree that it's best to drop bad apis, as spectra is header only it wont break binaries, also C++11 should be supported by all deployed compilers by now.
However I suggest to have version macros ie, `#define SPECTRA_VERSION 000900, see boost for example.
- I agree about C++11. All compilers support C++14 now, so 11 is a sure bet.
- The Davidson API we should have a discussion. Do you mind having a chat? I can send you a microsoft teams invite.
- I think one area spectra can still improve is better Testing/CI. We will probably add sth. there for the davidson stuff, if you would not mind. For example we can check if the code that is submitted is properly formatted.
I agree about the C++ 11 thing, because it is the beginning of modern C++.
About breaking old API, what about mark some of them as deprecated and remove them step by step? (However, [[deprecated]] is since C++14.)
@jschueller Thanks. I'll take a look.
@JensWehner Sure. We can discuss the details offline via email or other means. I may not be available to reply promptly as I have other duties this week.
@zhaiyusci Yeah, but the issue is that all API will be broken, if I do the first point mentioned above.
Hi all, here are some updates.
I've created a 1.y.z branch as a preview of the planned changes in the next major version. A brief changelog can be found here, with the changes in example code, although the API documentation has not been updated.
@jschueller Sure. It has been added: https://github.com/yixuan/spectra/commit/a97bf2034dc7e3b84862ae6a3aadf577e54724dc.
About conda compatibility, packages on conda will likely need patching to continue to build, unless we decide to pin the version on conda-forge if spectra moves on too fast. Hopefully it wont affect too many packages, only openturns I think :)
I just tested the 1y branch, and I could adapt to the new api in openturns without any trouble and pass the tests. I like the strongly typed enums, like CompInfo, but I'd like some function to convert it to string, (currently I use a static_cast to convert it to int and print that) Good job for the 1y branch, when do you plan to release it ?
Ah, personally I'd like to further polish it a little bit and add some new features before the actual release. After all it is marked as "1.0.0" and I wish to stabilize the API. And that's why I created this thread and wanted to hear your comments.
@jschueller I think it is close. I'm going to merge this branch and do some cleanups. There will be another big API change though: I want to remove the Scalar template parameter in eigen solvers, and let the matrix operator define a public typedef instead (built-in classes will do so). This should make the code a bit cleaner. An example would be as follows:
#include <Eigen/Core>
#include <Spectra/SymEigsSolver.h>
#include <iostream>
using namespace Spectra;
// M = diag(1, 2, ..., 10)
class MyDiagonalTen
{
public:
using Scalar = double; // This is now required for user-defined classes
int rows() { return 10; }
int cols() { return 10; }
// y_out = M * x_in
void perform_op(const double *x_in, double *y_out) const
{
for(int i = 0; i < rows(); i++)
{
y_out[i] = x_in[i] * (i + 1);
}
}
};
int main()
{
MyDiagonalTen op;
SymEigsSolver<MyDiagonalTen> eigs(op, 3, 6);
eigs.init();
eigs.compute(SortRule::LargestAlge);
if(eigs.info() == CompInfo::Successful)
{
Eigen::VectorXd evalues = eigs.eigenvalues();
std::cout << "Eigenvalues found:\n" << evalues << std::endl;
}
return 0;
}
Hi All, I have drafted a migration guide to document the user-level changes from 0.9.0 to 1.0.0. Hope this makes the transition a little easier.
I'm going to marge the 1.y.z branch to master soon.
Is there a way to implement a selection rule (or what it goes for it) to find an eigenvalue, the nearest to what I'm looking for, and x eigenvalues above or below it?
As an aside, I found the solver interfaces (such as SymEigsSolver) to be a little too restrictive for my use case. For example, there are use-cases where one may want to know the ritz values of the solver; maybe a Vector ritz_values(){...} would be useful to tack on.
