|Message: Re: how many voxels can geant4 includes?||Not Logged In (login)|
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For such use-cases, I suggest to use parametrized volume of uniform cell size, i.e. only material for each cell is parametrized in terms of copy number. In this case, the maximum number of cells is limitted by the 32-bit integer, i.e. 2^31 ~ 2*10^9, for their unique copy numbers. While, once you adopt three-dimentional parametrization, i.e. slicing the world volume along x, y and z axes sequentially, you will have a set of three copy numbers. In this case, you can have almost infinit number of cells. Real limitation should be the size of a vector mapping a copy number to corresponding material. For each cell, you need one pointer (size is equal to one integer) to G4Material object. Let's assume you will simulate 1 cubic meter of volume with 2*2*2 mm^3 cells. Then, you need a one-dimentional arey of 10^8 pointers, i.e. 400 MBytes of memory, for this mapping table. On the other hand, even for such huge simulation volume, each primary particle and its daughters won't see the whole body, but just a small potion. Thus, once you adopt a bit of tricks, for example loading only a portion of the pointer vector to memory, you can reduce the size of your executable significantly.
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