Reduced memory footprint of spectral discretizations via block-diagonal sparse operators#565
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How large are these matrices in general? |
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The matrix size is number of degrees of freedom squared. For instance, in 3D RBC, you have $(5 \times N^3)^2$ for 5 solution components and $N^3$ grid points, which is very large. But a block diagonal matrix (diagonal in the components) has only $5\timesN^3^2$ entries, so a fifth. Now, since the matrices are sparse, I don’t understand why you need less memory when using different scipy functions for generating the same sparse block diagonal matrix. But that is the case in my tests.On 5. Jul 2025, at 11:26, Robert Speck ***@***.***> wrote:pancetta left a comment (Parallel-in-Time/pySDC#565)
How large are these matrices in general?
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Allocation of memory in Python is not straightforward (and not efficient if done manually). Relying on libraries like scipy is strongly recommended over lists (or so). |
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#!!!!!! WARNING: RUFF FAILED !!!!!!: #F811 Redefinition of unused `RBC2DG4R4ResARa1e5` from line 524 # --> pySDC/projects/RayleighBenard/RBC3D_configs.py:529:7 # | Parallel-in-Time#529 | class RBC2DG4R4ResARa1e5(RBC2DResA): # | ^^^^^^^^^^^^^^^^^^ `RBC2DG4R4ResARa1e5` redefined here Parallel-in-Time#530 | Tend = 100 Parallel-in-Time#531 | res = 64 # | # ::: pySDC/projects/RayleighBenard/RBC3D_configs.py:524:7 # | Parallel-in-Time#524 | class RBC2DG4R4ResARa1e5(RBC2DResA): # | ------------------ previous definition of `RBC2DG4R4ResARa1e5` here Parallel-in-Time#525 | Tend = 100 Parallel-in-Time#526 | res = 64 # | #help: Remove definition: `RBC2DG4R4ResARa1e5` # #F811 Redefinition of unused `RBC2DG4R4SDC23A10Ra1e6` from line 565 # --> pySDC/projects/RayleighBenard/RBC3D_configs.py:578:7 # | Parallel-in-Time#578 | class RBC2DG4R4SDC23A10Ra1e6(RBC2DM2K3A): # | ^^^^^^^^^^^^^^^^^^^^^^ `RBC2DG4R4SDC23A10Ra1e6` redefined here Parallel-in-Time#579 | Tend = 50 Parallel-in-Time#580 | res = 128 # | # ::: pySDC/projects/RayleighBenard/RBC3D_configs.py:565:7 # | Parallel-in-Time#565 | class RBC2DG4R4SDC23A10Ra1e6(RBC2DM2K3A): # | ---------------------- previous definition of `RBC2DG4R4SDC23A10Ra1e6` here Parallel-in-Time#566 | Tend = 100 Parallel-in-Time#567 | res = 64 # | #help: Remove definition: `RBC2DG4R4SDC23A10Ra1e6` # #Found 2 errors.:
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The spectral discretizations require a few block-diagonal matrices among all degrees of freedom. Constructing them as such actually reduces the memory requirements quite a bit compared to constructing general block matrices with only the diagonal blocks.
This is independent of the larger refactor, which is why I did a separate PR.
I added a test that the resulting operators are the same and that indeed memory is reduced.