Sparse Filtering in R

[vodkhang]

Hi,

I tried to implement the sparse filtering in R but got this warning message, do you know what it is?
Warning messages:
1: In optimx.run(par, optcfg$ufn, optcfg$ugr, optcfg$uhess, lower, :
Hessian is reported non-symmetric with asymmetry ratio 0.551328252008331
2: Hessian forced symmetric