I accidentally replied off-list, oops ...
--- Begin Message ---Magnus Hagdorn writes: > Hello world, > Do you have estimates for the memory requirements for the stiffness > matrix and load vector? What size problems can be reasonably run? The stiffness matrix will always require way more storage, so let's concentrate on that. It depends on the number of variables Nv in your system and the connectivity of the mesh. If we consider e.g. a structured 3D mesh of 8-node hexahedra, each node has 27 neighbors (including itself). Each sparse matrix row will in general contain 27*Nv nonzero entries. Supposing that your structured grid contains Nx*Ny*Nz nodes, the total number of nonzeros will be Nx*Ny*Nz*27*Nv. Assuming each nonzero requires 8 bytes of storage (double precision) and maybe another 8 bytes or so of sparsity information, the total storage requirement is approximately Nx*Ny*Nz*27*Nv*16 bytes. Concrete example: 20^3 nodes, 3 variables per node = 20*20*20*27*3*16 = 10368000 bytes = about 10 MB If you are using tetrahedra, I believe the number of nonzeros per row jumps dramatically due to the connectivity, so you have to take this into account. The DofMap and Mesh have recently been parallelized by other developers, so I think I will let them comment a bit more on that aspect of storage. -J
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