validObject Error in huge.mb for small sample data

[zdk123]

I'm trying to understand this error - which seems to occur when re-constructing a sparse matrix on small-sample data and perhaps with small values of lambda.

Reproduce the error:

library(huge)
set.seed(10010)
dat <- huge.generator(n=5, d=250)

# these fail
est1 <- huge(dat$data, method='mb', scr=FALSE, nlambda=100, lambda.min.ratio = 5e-5)
est2 <- huge(dat$data, method='mb', scr=FALSE, nlambda=10, lambda.min.ratio = 1e-4)

Error in validObject(.Object) : 
  invalid class “dgCMatrix” object: all row indices must be between 0 and nrow-1

Interestingly, small tweaks to the lambda path seem to run OK.

est3 <- huge(dat$data, method='mb', scr=FALSE, nlambda=100, lambda.min.ratio = 2e-4)
est4 <- huge(dat$data, method='mb', scr=FALSE, nlambda=10, lambda.min.ratio = 2e-4)

and if we pass in the correlation matrix directly, previously failed are OK

est1.cor <- huge(cor(dat$data), method='mb', scr=FALSE, nlambda=100, lambda.min.ratio = 5e-5)
est2.cor <- huge(cor(dat$data), method='mb', scr=FALSE, nlambda=10, lambda.min.ratio = 1e-4)
est3.cor <- huge(cor(dat$data), method='mb', scr=FALSE, nlambda=100, lambda.min.ratio = 2e-4)
est4.cor <- huge(cor(dat$data), method='mb', scr=FALSE, nlambda=10, lambda.min.ratio = 2e-4)

It seems that the only difference when passing the correlation matrix seems to be the maxdf is d rather than n.

The error seems to be coming from this block:
https://github.com/HMJiangGatech/huge/blob/master/R/huge.mb.R#L107-L120
It seems perhaps the for loop is trying to index values that aren't there - perhaps because maxdf isn't large enough (in which case I don't understand the purpose of the parameter).