Tian

I plan to add the default value to `na.action`, `subset` in `valid_model_control()`. However, i'll need to call `valid_model_control()` in `sgd.formula`. So `valid_model_control()` will be called twice. I think the redundancy...

I haven't formally profiled the code. But I once ran the code with validity checks commented out. There's no significant improvement in performance.

The `optim()` and `lapply()` in the built in r core package evaluates the user defined functions in R by calling the function in R. For now, we can also call...

Ye and I just looked at the wiki. Thanks for the new method. we have a few questions about the method. 1. You mentioned " α_n and D_n need to...

1) and 2) will be implemented as assertions in DEBUG mode c++ code. 4) is implemented as: if MSE(SGD) > 1e-2, then fail the test. 5) will be added as...

Current implementation returns `convergence=True` without any checking