If the number of parameters is small, less than four2.4, it is conceivable to calculate 
for each combination of parameters. Theoretically, this method offers the best exploration of the parameter space compared to all other techniques. However, considering the number of forward problems to solve, this method is very limited. For example, if the prior range of each parameter is discretized with 50 samples, if the time to calculate one forward problem is one second, and if the dimension of the parameter space is five, the total time required for the inversion is 10 years.