Table 3.

The run time is given for N_phot = 1.28 · 10⁶ Monte Carlo trials, which is our principal operating point in the paper. for the sample with t=6.10 mm and λ = 805 nm. The number of processors used is N_proc. The notation “Fwd” means that only the forward problem is solved (i.e., the ARS is found for one set of parameters) “Inv” refers to the inverse problem (i.e., solving for a set of parameters). The number of iterations is quoted as the number necessary to reach convergence. The number of times the 1.28 · 10⁶ Monte Carlo trials were performed in the final iteration is reported as N_eval. In the case of PSO, this number of evaluations is performed at every iteration. In the present methods, the number of Monte Carlo trials increases from 2 · 10⁴ to the final value by doubling at each iteration. The times refer to runs on a Dell Optiplex 9010 AIO computer with an Intel i5-3570S quad-core processor running at 3.10 GHz. The present explicit grid method is estimated because it was implemented in a scripting language on a different computer.

		Nproc		Niter	Neval	time (s)
MCML [40]	C	1	Fwd	1	1	47
Present single point estimate	C++	1	Fwd	1	1	33
Present single point estimate	C++/OMP	4	Fwd	1	1	13
Present importance sampling	C++/OMP	4	Fwd	1	1	39
Particle Swarm Optimization	C++/OMP	4	Inv	17	27	4748
Present explicit grid	Est.	4	Inv	7	255	5300
Present importance sampling	C++/OMP	4	Inv	7	1	75