Parallel / Multicore Processing in R for an Intege

Question

Are there any packages specifically to let R run faster via parallel computing? I have made a very large IP that needs to run for a while, so I was wondering if there was a specific package in R that could help me run my IP. Currently, I have a function that returns the solution of an IP and the primary line that R gets stuck on (for a very...very long time) is when I use lp (....all.int = TRUE). My CPU is around 12.5% (8 cores) on my Windows computer, and I want it to near 100

Edit: I tried using the doParallel package,

library('doParallel')
cl <- makeCluster(8)
registerDoParallel(cl)

But my CPU usage is still not at 100%. What else do i need to do? Is there a specific package that makes optimization problems run faster? Most parallel packages help with simulation, and foreach seems to only work for iterative structures/ apply functions. I just want R to use all my CPU usage