Translated the hh-lambda loop

[wleoncio]

Summary

Lots of changes related to work towards #17.

Most relevant commits

• Extracted hh <= nlamba loop as R function hh_nlambda_loop() (Slow admm_MADMMplasso() under ADMMplasso() #17)
• Translated hh_nlambda_loop() to C++ as hh_nlambda_loop_cpp() (Slow admm_MADMMplasso() under ADMMplasso() #17)
• Translated count_nonzero_a() to C++ (Slow admm_MADMMplasso() under ADMMplasso() #17)
• print(cost_time) only triggers if my_print == TRUE

There are a couple of issues detected during this work, but they'll be left to another issue since they are already present on main (meaning they were not introduced here). Namely:

MADMMplasso/tests/testthat/test-MADMMplasso.R

Lines 83 to 102 in 2b4d267

	set.seed(9356219)
	fit_C <- MADMMplasso(
	X, Z, y,
	alpha = alpha, my_lambda = matrix(rep(0.2, dim(y)[2]), 1),
	lambda_min = 0.001, max_it = 5000, e.abs = e.abs, e.rel = e.rel, maxgrid = nlambda,
	nlambda = nlambda, rho = 5, tree = TT, my_print = FALSE, alph = 1, parallel = FALSE,
	pal = TRUE, gg = gg1, tol = tol, cl = 6
	) # FIXME: fails if (parallel = FALSE && pal = FALSE) or (parallel = TRUE)
	set.seed(9356219)
	fit_R <- suppressWarnings(
	suppressMessages(
	MADMMplasso(
	X, Z, y,
	alpha = alpha, my_lambda = matrix(rep(0.2, dim(y)[2]), 1),
	lambda_min = 0.001, max_it = 5000, e.abs = e.abs, e.rel = e.rel, maxgrid = nlambda,
	nlambda = nlambda, rho = 5, tree = TT, my_print = FALSE, alph = 1, parallel = FALSE,
	pal = TRUE, gg = gg1, tol = tol, cl = 6, legacy = TRUE
	)
	)
	) # FIXME: fails if (parallel = TRUE)