We have six parameters
(A, B, C, D, E, F)
representing the partition of mesh and cpus in M3D calculations.
A gives the total number of planes in toroidal φ direction;
B gives the number of CPUs in toroidal φ direction (B ≤ A).
C gives the number of grids in minor radial r direction;
D gives the number of CPUs in radial r direction.
E gives the number of partitions in poloidal θ direction (E ≥ 3);
F gives the number of CPUs in poloidal θ direction.
The total size of 3D mesh is given by parameters A, C, and E
using formulae A[1+C(C-1)E ⁄ 2]; and
the total number of cpu is given by paramters B, D, and F
using formulae BF (when D=1) or B(F+1) (when D=2).
Each point in the following plots has individual values assigned to these parameters.
In the case of strong scaling, parameters A, C, and E are fixed all the time,
while parameters B, D, and F changes,
resulting in an increase of total cpus and the amount of work on each processor is reduced.
In the case of weak scaling, parameters A, C, and E increases as
the parameters B, D, and F increases,
resulting in a roughly fixed amount of work on each processor all the time.