(FEM) Reorder nodes or use sparse matrix storing techniquesEfficient assembly of finite element matrix in MATLABPreconditioner for finding the smallest eigenpairs of a large, but structured, matrixIs there a bound on the number of edges, facets, and elements in a 3D simplicial mesh in terms of the number of mesh nodes?Raviart-Thomas elements global definition and compact supportMeshing options to generate number of the sides of and element (tetgen-triangle)Applying the result of Cuthill-McKee in SciPyBoundary condtions on nonlinear FEM time integrationSparse matrix inverse with reduced bandwidthLeveraging scipy for matrix free finite elementsbit-packing and compression of data structures in scientific computing

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(FEM) Reorder nodes or use sparse matrix storing techniques


Efficient assembly of finite element matrix in MATLABPreconditioner for finding the smallest eigenpairs of a large, but structured, matrixIs there a bound on the number of edges, facets, and elements in a 3D simplicial mesh in terms of the number of mesh nodes?Raviart-Thomas elements global definition and compact supportMeshing options to generate number of the sides of and element (tetgen-triangle)Applying the result of Cuthill-McKee in SciPyBoundary condtions on nonlinear FEM time integrationSparse matrix inverse with reduced bandwidthLeveraging scipy for matrix free finite elementsbit-packing and compression of data structures in scientific computing













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$begingroup$


Is it necessary to reorder nodes (using Reverse Cuthill-Mckee algorithm, for example) if I am already using a CSR or CSC storing technique? Because, since CSR/CSC only stores non-zero elements I guess reorder wouldn't be much advantageous.










share|cite|improve this question











$endgroup$
















    1












    $begingroup$


    Is it necessary to reorder nodes (using Reverse Cuthill-Mckee algorithm, for example) if I am already using a CSR or CSC storing technique? Because, since CSR/CSC only stores non-zero elements I guess reorder wouldn't be much advantageous.










    share|cite|improve this question











    $endgroup$














      1












      1








      1


      1



      $begingroup$


      Is it necessary to reorder nodes (using Reverse Cuthill-Mckee algorithm, for example) if I am already using a CSR or CSC storing technique? Because, since CSR/CSC only stores non-zero elements I guess reorder wouldn't be much advantageous.










      share|cite|improve this question











      $endgroup$




      Is it necessary to reorder nodes (using Reverse Cuthill-Mckee algorithm, for example) if I am already using a CSR or CSC storing technique? Because, since CSR/CSC only stores non-zero elements I guess reorder wouldn't be much advantageous.







      finite-element sparse






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      share|cite|improve this question








      edited Apr 30 at 15:38









      Anton Menshov

      4,13721665




      4,13721665










      asked Apr 30 at 12:57









      Gustavo CostaGustavo Costa

      82




      82




















          1 Answer
          1






          active

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          4












          $begingroup$

          You should use a reordering. Although it's true that storing a sparse matrix requires the same amount of memory whether or not you reorder it using RCM, reordering it should lead to faster calculations (eg matrix-vector products) due to different/better utilization of cache.



          Something to keep in mind is that the "best" reordering depends upon what you intend to do with the matrix. Bandwidth reduction reorderings (like RCM) help with matvec's, but if you're reordering a matrix for parallel distribution you should look into methods that minimize edge-cut/communication-volume (like METIS, others), and if you're looking into sparse direct methods you should consider unstructured nested-dissection (METIS/SCOTCH) or fill-minimization (minimum degree or appproximate MD).






          share|cite|improve this answer









          $endgroup$












          • $begingroup$
            Do you have any references, or even just a crude estimate based on your personal experience, on what kind of speedup one could expect when reordering a sparse MVP? I'm personally interested in sparse matrices arising from 3D FEM systems of size in the 100s of MBs to GBs.
            $endgroup$
            – LedHead
            Apr 30 at 17:15










          • $begingroup$
            Unfortunately I do not. On very large systems the reordering effect might be pretty subtle, since you can only squeeze the bandwidth so much on a matrix with 3D connectivity. I think a new question might be in order. For what it's worth, it's not too hard of an experiment to run for yourself in eg matlab or some other linear algebra platform. On the other hand, for direct solvers the effects of reordering are enormous, their asymptotic complexity (big-O) hinges on doing it properly.
            $endgroup$
            – rchilton1980
            May 1 at 0:59











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          active

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          active

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          4












          $begingroup$

          You should use a reordering. Although it's true that storing a sparse matrix requires the same amount of memory whether or not you reorder it using RCM, reordering it should lead to faster calculations (eg matrix-vector products) due to different/better utilization of cache.



          Something to keep in mind is that the "best" reordering depends upon what you intend to do with the matrix. Bandwidth reduction reorderings (like RCM) help with matvec's, but if you're reordering a matrix for parallel distribution you should look into methods that minimize edge-cut/communication-volume (like METIS, others), and if you're looking into sparse direct methods you should consider unstructured nested-dissection (METIS/SCOTCH) or fill-minimization (minimum degree or appproximate MD).






          share|cite|improve this answer









          $endgroup$












          • $begingroup$
            Do you have any references, or even just a crude estimate based on your personal experience, on what kind of speedup one could expect when reordering a sparse MVP? I'm personally interested in sparse matrices arising from 3D FEM systems of size in the 100s of MBs to GBs.
            $endgroup$
            – LedHead
            Apr 30 at 17:15










          • $begingroup$
            Unfortunately I do not. On very large systems the reordering effect might be pretty subtle, since you can only squeeze the bandwidth so much on a matrix with 3D connectivity. I think a new question might be in order. For what it's worth, it's not too hard of an experiment to run for yourself in eg matlab or some other linear algebra platform. On the other hand, for direct solvers the effects of reordering are enormous, their asymptotic complexity (big-O) hinges on doing it properly.
            $endgroup$
            – rchilton1980
            May 1 at 0:59















          4












          $begingroup$

          You should use a reordering. Although it's true that storing a sparse matrix requires the same amount of memory whether or not you reorder it using RCM, reordering it should lead to faster calculations (eg matrix-vector products) due to different/better utilization of cache.



          Something to keep in mind is that the "best" reordering depends upon what you intend to do with the matrix. Bandwidth reduction reorderings (like RCM) help with matvec's, but if you're reordering a matrix for parallel distribution you should look into methods that minimize edge-cut/communication-volume (like METIS, others), and if you're looking into sparse direct methods you should consider unstructured nested-dissection (METIS/SCOTCH) or fill-minimization (minimum degree or appproximate MD).






          share|cite|improve this answer









          $endgroup$












          • $begingroup$
            Do you have any references, or even just a crude estimate based on your personal experience, on what kind of speedup one could expect when reordering a sparse MVP? I'm personally interested in sparse matrices arising from 3D FEM systems of size in the 100s of MBs to GBs.
            $endgroup$
            – LedHead
            Apr 30 at 17:15










          • $begingroup$
            Unfortunately I do not. On very large systems the reordering effect might be pretty subtle, since you can only squeeze the bandwidth so much on a matrix with 3D connectivity. I think a new question might be in order. For what it's worth, it's not too hard of an experiment to run for yourself in eg matlab or some other linear algebra platform. On the other hand, for direct solvers the effects of reordering are enormous, their asymptotic complexity (big-O) hinges on doing it properly.
            $endgroup$
            – rchilton1980
            May 1 at 0:59













          4












          4








          4





          $begingroup$

          You should use a reordering. Although it's true that storing a sparse matrix requires the same amount of memory whether or not you reorder it using RCM, reordering it should lead to faster calculations (eg matrix-vector products) due to different/better utilization of cache.



          Something to keep in mind is that the "best" reordering depends upon what you intend to do with the matrix. Bandwidth reduction reorderings (like RCM) help with matvec's, but if you're reordering a matrix for parallel distribution you should look into methods that minimize edge-cut/communication-volume (like METIS, others), and if you're looking into sparse direct methods you should consider unstructured nested-dissection (METIS/SCOTCH) or fill-minimization (minimum degree or appproximate MD).






          share|cite|improve this answer









          $endgroup$



          You should use a reordering. Although it's true that storing a sparse matrix requires the same amount of memory whether or not you reorder it using RCM, reordering it should lead to faster calculations (eg matrix-vector products) due to different/better utilization of cache.



          Something to keep in mind is that the "best" reordering depends upon what you intend to do with the matrix. Bandwidth reduction reorderings (like RCM) help with matvec's, but if you're reordering a matrix for parallel distribution you should look into methods that minimize edge-cut/communication-volume (like METIS, others), and if you're looking into sparse direct methods you should consider unstructured nested-dissection (METIS/SCOTCH) or fill-minimization (minimum degree or appproximate MD).







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered Apr 30 at 13:12









          rchilton1980rchilton1980

          2,412713




          2,412713











          • $begingroup$
            Do you have any references, or even just a crude estimate based on your personal experience, on what kind of speedup one could expect when reordering a sparse MVP? I'm personally interested in sparse matrices arising from 3D FEM systems of size in the 100s of MBs to GBs.
            $endgroup$
            – LedHead
            Apr 30 at 17:15










          • $begingroup$
            Unfortunately I do not. On very large systems the reordering effect might be pretty subtle, since you can only squeeze the bandwidth so much on a matrix with 3D connectivity. I think a new question might be in order. For what it's worth, it's not too hard of an experiment to run for yourself in eg matlab or some other linear algebra platform. On the other hand, for direct solvers the effects of reordering are enormous, their asymptotic complexity (big-O) hinges on doing it properly.
            $endgroup$
            – rchilton1980
            May 1 at 0:59
















          • $begingroup$
            Do you have any references, or even just a crude estimate based on your personal experience, on what kind of speedup one could expect when reordering a sparse MVP? I'm personally interested in sparse matrices arising from 3D FEM systems of size in the 100s of MBs to GBs.
            $endgroup$
            – LedHead
            Apr 30 at 17:15










          • $begingroup$
            Unfortunately I do not. On very large systems the reordering effect might be pretty subtle, since you can only squeeze the bandwidth so much on a matrix with 3D connectivity. I think a new question might be in order. For what it's worth, it's not too hard of an experiment to run for yourself in eg matlab or some other linear algebra platform. On the other hand, for direct solvers the effects of reordering are enormous, their asymptotic complexity (big-O) hinges on doing it properly.
            $endgroup$
            – rchilton1980
            May 1 at 0:59















          $begingroup$
          Do you have any references, or even just a crude estimate based on your personal experience, on what kind of speedup one could expect when reordering a sparse MVP? I'm personally interested in sparse matrices arising from 3D FEM systems of size in the 100s of MBs to GBs.
          $endgroup$
          – LedHead
          Apr 30 at 17:15




          $begingroup$
          Do you have any references, or even just a crude estimate based on your personal experience, on what kind of speedup one could expect when reordering a sparse MVP? I'm personally interested in sparse matrices arising from 3D FEM systems of size in the 100s of MBs to GBs.
          $endgroup$
          – LedHead
          Apr 30 at 17:15












          $begingroup$
          Unfortunately I do not. On very large systems the reordering effect might be pretty subtle, since you can only squeeze the bandwidth so much on a matrix with 3D connectivity. I think a new question might be in order. For what it's worth, it's not too hard of an experiment to run for yourself in eg matlab or some other linear algebra platform. On the other hand, for direct solvers the effects of reordering are enormous, their asymptotic complexity (big-O) hinges on doing it properly.
          $endgroup$
          – rchilton1980
          May 1 at 0:59




          $begingroup$
          Unfortunately I do not. On very large systems the reordering effect might be pretty subtle, since you can only squeeze the bandwidth so much on a matrix with 3D connectivity. I think a new question might be in order. For what it's worth, it's not too hard of an experiment to run for yourself in eg matlab or some other linear algebra platform. On the other hand, for direct solvers the effects of reordering are enormous, their asymptotic complexity (big-O) hinges on doing it properly.
          $endgroup$
          – rchilton1980
          May 1 at 0:59

















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