I’m working on the classification problem having close to 6L observations and 60 variables. Variables also having missing values, I have removed the variables with a large number of missing values and trying to impute the missing values for rest of the variables.

I’ve tried the MICE and missForest package from R but it’s taking more time to compute the missing values. How to proceed with missing values imputation, any other approach or algorithm? Do I have to use parallel computation?