Speed-up factors attained by using the reduced-morphology models on a standard PC. The first column indicates the objective functions to which the simulation contributes (see Table 2), and the lower-case letter indicates the amplitude (‘a’ for smallest current, ‘c’ for largest) if more than one stimulus amplitudes were given. The second and third columns show the factors (mean ± SD, Nsamp = 5) by which the simulation times were shortened by the use of models with reduced morphology using 20 or 5 spatial segments per compartment, respectively, when variable time step method was used. The fourth column shows the corresponding factor (for reduced-morphology model with 5 spatial segments per compartment) when fixed time step method was used. In the reconstructed morphology (cell #2 of [26]), the default numbers of segments were used; these varied between 1 and 15 and summed up to 715. The numbers of differential equations solved were 5833 in the full model and 215 or 860 in the reduced-morphology model with 5 or 20 segments per compartment, respectively, giving theoretical speed-up-factor estimates 27.13 and 6.78. The data are grouped according to the steps to which the objective functions belong. All simulations were run with the NEURON software using a single central processing unit (CPU).
