13 research outputs found
Sparse Approximate Multifrontal Factorization with Butterfly Compression for High Frequency Wave Equations
We present a fast and approximate multifrontal solver for large-scale sparse
linear systems arising from finite-difference, finite-volume or finite-element
discretization of high-frequency wave equations. The proposed solver leverages
the butterfly algorithm and its hierarchical matrix extension for compressing
and factorizing large frontal matrices via graph-distance guided entry
evaluation or randomized matrix-vector multiplication-based schemes. Complexity
analysis and numerical experiments demonstrate
computation and memory complexity when applied to an sparse system arising from 3D high-frequency Helmholtz and Maxwell problems
A Parallel Hierarchical Blocked Adaptive Cross Approximation Algorithm
This paper presents a hierarchical low-rank decomposition algorithm assuming
any matrix element can be computed in time. The proposed algorithm
computes rank-revealing decompositions of sub-matrices with a blocked adaptive
cross approximation (BACA) algorithm, followed by a hierarchical merge
operation via truncated singular value decompositions (H-BACA). The proposed
algorithm significantly improves the convergence of the baseline ACA algorithm
and achieves reduced computational complexity compared to the full
decompositions such as rank-revealing QR decompositions. Numerical results
demonstrate the efficiency, accuracy and parallel efficiency of the proposed
algorithm
Open Problems in (Hyper)Graph Decomposition
Large networks are useful in a wide range of applications. Sometimes problem
instances are composed of billions of entities. Decomposing and analyzing these
structures helps us gain new insights about our surroundings. Even if the final
application concerns a different problem (such as traversal, finding paths,
trees, and flows), decomposing large graphs is often an important subproblem
for complexity reduction or parallelization. This report is a summary of
discussions that happened at Dagstuhl seminar 23331 on "Recent Trends in Graph
Decomposition" and presents currently open problems and future directions in
the area of (hyper)graph decomposition
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A Supernodal Approach to Incomplete LU Factorization with Partial Pivoting
We present a new supernode-based incomplete LU factorization method to construct a preconditioner for solving sparse linear systems with iterative methods. The new algorithm is primarily based on the ILUTP approach by Saad, and we incorporate a number of techniques to improve the robustness and performance of the traditional ILUTP method. These include the new dropping strategies that accommodate the use of supernodal structures in the factored matrix. We present numerical experiments to demonstrate that our new method is competitive with the other ILU approaches and is well suited for today's high performance architectures
Detecting resonance of radio-frequency cavities using fast direct integral equation solvers and augmented Bayesian optimization
This paper presents a computationally efficient framework for identifying
resonance modes of 3D radio-frequency (RF) cavities with damping waveguide
ports. The proposed framework relies on surface integral equation (IE)
formulations to convert the task of resonance detection to the task of finding
resonance frequencies at which the lowest few eigenvalues of the system matrix
is close to zero. For the linear eigenvalue problem \rev{with a fixed
frequency}, we propose leveraging fast direct solvers to efficiently invert the
system matrix; for the frequency search problem, we develop a hybrid
optimization algorithm that combines Bayesian optimization with down-hill
simplex optimization. The proposed IE-based resonance detection framework
(IERD) has been applied to detection of high-order resonance modes (HOMs) of
realistic accelerator RF cavities to demonstrate its efficiency and accuracy
Open Problems in (Hyper)Graph Decomposition
Large networks are useful in a wide range of applications. Sometimes problem instances are composed of billions of entities. Decomposing and analyzing these structures helps us gain new insights about our surroundings. Even if the final application concerns a different problem (such as traversal, finding paths, trees, and flows), decomposing large graphs is often an important subproblem for complexity reduction or parallelization. This report is a summary of discussions that happened at Dagstuhl seminar 23331 on "Recent Trends in Graph Decomposition" and presents currently open problems and future directions in the area of (hyper)graph decomposition