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Scott MacLachlan


smaclachlan [at] mun.ca

Department of Mathematics and Statistics
Memorial University of Newfoundland
St. John's, NL
A1C 5S7
Canada
709-864-8095



Prior to July 2014, I was in the Department of Mathematics at Tufts University, in Medford, MA, USA. I remain involved in several collaborative projects there.

       Research        Publications        Teaching


Research Overview

My research interests are in computational applied mathematics and scientific computation. In particular, I work on developing efficient numerical methods for the solution of partial differential and integro-differential equations, using the tools of multiscale numerical analysis.

Things I do:

  • Associate Editor, SIAM Journal on Matrix Analysis and Applications
  • Editorial board, Numerical Linear Algebra with Applications
  • Associate Editor, SIAM Journal on Scientific Computing
  • Program Committee, International Workshop on Multiscale Modeling and Simulation
  • Program Committee Co-Chair, Copper Mountain Conference on Multigrid Methods

    Software:
  • XBraid, a non-intrusive approach for Parallel time integration with multigrid
  • Shear deformation, incompressible non-linear elasticity with Lagrange-multiplier formulation, for Mathematical and computational models of incompressible materials subject to shear
  • Adaptive AMG research code, available upon (email) request



  • Publications
    Journal Articles:
  • Generalizing Lloyd's algorithm for graph clustering, T. Zaman, N. Nytko, A. Taghibakhshi, S. MacLachlan, L. Olson, and M. West, submitted, 2023

  • Optimized sparse matrix operations for reverse mode automatic differentiation, N. Nytko, A. Taghibakhshi, T. Zaman, S. MacLachlan, L. Olson, and M. West, submitted, 2023

  • MG-GNN: Multi-grid graph neural networks for learning multilevel domain decomposition methods, A. Taghibakhshi, N. Nytko, T. Zaman, S. MacLachlan, L. Olson, and M. West, submitted, 2023

  • Generalizing reduction-based algebraic multigrid, T. Zaman, N. Nytko, A. Taghibakhshi, S. MacLachlan, L. Olson, and M. West, submitted, 2022

  • Finite-element discretization of the smectic density equation, P.E. Farrell, A. Hamdan, S.P. MacLachlan, submitted, 2022

  • Preconditioned Krylov solvers for structure-preserving discretisations, J. Jackaman and S. MacLachlan, in revision, 2023

  • Multigrid reduction-in-time convergence for advection problems: A Fourier analysis perspective, H. De Sterck, S. Friedhoff, O.A. Krzysik, S.P. MacLachlan, in revision, 2023

  • Coarse-Grid Selection Using Simulated Annealing, T.U. Zaman, S.P. MacLachlan, L.N. Olson, and M. West, to appear, Journal of Computational and Applied Mathematics, 2023

  • Monolithic multigrid for a reduced-quadrature discretization of poroelasticity, J.H. Adler, Y. He, X. Hu, S. MacLachlan, and P. Ohm, to appear, SIAM J. Sci. Comp., 2023

  • Monolithic multigrid for implicit Runge-Kutta discretizations of incompressible fluid flow, R. Abu-Labdeh, S. MacLachlan, and P.E. Farrell, Journal of Computational Physics, 478:111961, 2023.

  • Multigrid reduction in time for non-linear hyperbolic equations, F. Danieli and S. MacLachlan, Electronic Transactions on Numerical Analysis 58:43-65, 2023.

  • Learning Interface Conditions in Domain Decomposition Solvers, A. Taghibakhshi, N. Nytko, T. Zaman, S. MacLachlan, L. Olson, and M. West, Advances in Neural Information Processing Systems 35 (NeurIPS 2022), 35:72222-7235, 2022

  • A new mixed finite-element method for H2 elliptic problems, P.E. Farrell, A. Hamdan, and S. MacLachlan, Computers and Mathematics with Applications, 128:300-319, 2022.

  • A Boundary-Layer Preconditioner for Singularly Perturbed Convection Diffusion, S.P. MacLachlan, N. Madden, and T.A. Nhan, SIAM Journal on Matrix Analysis and Applications, 43(2):561-583, 2022

  • Low-order preconditioning of the Stokes equations, A. Voronin, Y. He, S. MacLachlan, L. Olson, and R. Tuminaro, Numerical Linear Algebra with Applications 29(3):e2426, 2022.

  • Optimization-Based Algebraic Multigrid Coarsening Using Reinforcement Learning, A. Taghibakhshi, S. MacLachlan, L. Olson, and M. West, Advances in Neural Information Processing Systems 34 (NeurIPS 2021), 34:12129-12140, 2021

  • Selective decay for the rotating shallow-water equations with a structure-preserving discretization, R. Brecht, W. Bauer, A. Bihlo, F. Gay-Balmaz, and S. MacLachlan, Physics of Fluids 33, 116604 (2021)

  • Optimizing MGRIT and Parareal coarse-grid operators for linear advection, H. De Sterck, R.D. Falgout, S. Friedhoff, O.A. Krzysik, S.P. MacLachlan, Numerical Linear Algebra with Applications, 28(4):e2367, 2021.

  • Monolithic multigrid for magnetohydrodynamics, J.H. Adler, T. Benson, E.C. Cyr, P.E. Farrell, S. MacLachlan, and R. Tuminaro, SIAM J. Sci. Comp., 43(5):S70-S91, 2021.

  • Structural Landscapes in Geometrically Frustrated Smectics, J. Xia, S. MacLachlan, T.J. Atherton, and P.E. Farrell, Phys. Rev. Lett. 126, 177801 (2021).

  • Numerical modeling of a memory-based diffusivity equation and determination of its fractional order value, T.U. Zaman, S. MacLachlan, and M.E. Hossain, Computational Geosciences, 25:655-669, 2021.

  • A local Fourier analysis of additive Vanka relaxation for the Stokes equations, P.E. Farrell, Y. He, and S. MacLachlan, Numerical Linear Algebra with Applications, 28(3):e2306, 2021.

  • Tuning Multigrid Methods with Robust Optimization, J. Brown, Y. He, S. MacLachlan, M. Menickelly, S.M. Wild, SIAM J. Sci. Comp., 43(1):A109-A138, 2021.

  • Block preconditioning techniques for geophysical electromagnetics, H. bin Zubair Syed, C. Farquharson, and S. MacLachlan, SIAM J. Sci. Comp., 42(3):B696-B721, 2020.

  • Goal-oriented hr-adaptivity for finite-element models with jumping coefficients, H. Jahandari, S. MacLachlan, R. Haynes, and N. Madden, Computational Geosciences, 24:1257-1283, 2020.

  • Two-level Fourier analysis of multigrid for higher-order finite-element discretizations of the Laplacian, Y. He and S. MacLachlan, Numerical Linear Algebra with Applications, 27(3): e2285, 2020.

  • First-order system least squares finite-elements for singularly perturbed reaction-diffusion equations, James H. Adler, Scott MacLachlan, and Niall Madden, Large-Scale Scientific Computing 2019, Springer, Lecture Notes in Computer Science vol. 11958, pp. 3-14, 2020.

  • Convergence analysis for parallel-in-time solution of hyperbolic systems, H. De Sterck, S. Friedhoff, A. J. M. Howse, and S. P. MacLachlan, Numerical Linear Algebra with Applications, 27(1):e2271, 2020.

  • Multistage cooling and freezing of a saline spherical water droplet, A. Dehghani-Sanij, S. MacLachlan, G. Naterer, Y. Muzychka, R. Haynes, and V. Enjilela, International Journal of Thermal Sciences, 147:106095, 2020.

  • Local Fourier analysis of BDDC-like algorithms, J. Brown, Y. He, and S. MacLachlan, SIAM J. Sci. Comput., 41(1):S346-S369, 2019.

  • Local Fourier analysis for mixed finite-element methods for the Stokes equations, Y. He and S. MacLachlan, Journal of Computational and Applied Mathematics, 357:161-183, 2019.

  • Variational integrator for the rotating shallow-water equations on the sphere, R. Brecht, W. Bauer, A. Bihlo, F. Gay-Balmaz, and S. MacLachlan, Quarterly Journal of the Royal Meteorological Society, 145(720):1070-1088, 2019.

  • Vector-potential finite-element formulations for two-dimensional resistive magnetohydrodynamics, J.H. Adler, Y. He, X. Hu, and S.P. MacLachlan, Computers and Mathematics with Applications, 77(2):476-493, 2019

  • Parallel-in-time multigrid with adaptive spatial coarsening for the linear advection and inviscid Burgers equations, H. De Sterck, R. Falgout, A. Howse, S. MacLachlan, and J. Schroder, SIAM J. Sci. Comput., 41(1):A538-565, 2019.

  • Well-balanced mesh-based and meshless schemes for the shallow-water equations, A. Bihlo and S. MacLachlan, BIT Numerical Mathematics, 58(3):579-598, 2018.

  • Boundary layer preconditioners for finite-element discretizations of singularly perturbed reaction-diffusion problems, T.A. Nhan, S. MacLachlan, and N. Madden, Numerical Algorithms, 79:281-310, 2018.

  • Local Fourier analysis of block-structured multigrid relaxation schemes for the Stokes equations, Y. He and S. MacLachlan, Numerical Linear Algebra with Applications, 25(3):e2147, 2018.

  • A well-balanced meshless tsunami propagation and inundation model, R. Brecht, A. Bihlo, S. MacLachlan, and J. Behrens, Advances in Water Resources, 115:273-285, 2018.

  • Computing equilibrium states of cholesteric liquid crystals in elliptical channels with deflation algorithms, D.B. Emerson, P.E. Farrell, J.H. Adler, S.P. MacLachlan, and T.J. Atherton, Liquid Crystals, 45(3):341-350, 2018.

  • Discrete energy laws for the first-order system least-squares finite-element approach, J. H. Adler, I. Lashuk, S. P. MacLachlan, and L. T. Zikatanov, Large-Scale Scientific Computing 2017, Springer, Lecture Notes in Computer Science, vol. 10665, pp. 3-20, 2018

  • Composite-grid multigrid for diffusion on the sphere, J.H. Adler, I. Lashuk, and S.P. MacLachlan, Numerical Linear Algebra with Applications, 25(1):e2115, 2018

  • Multigrid methods with space-time concurrency, R. Falgout, S. Friedhoff, Tz. Kolev, S. MacLachlan, J. Schroder, and S. Vandewalle, Comput. Vis. Sci., 18(4-5):123-143, 2017.

  • A Gauged Finite-element Potential Formulation for Accurate Inductive and Galvanic Modelling of Three-dimensional Electromagnetic Problems, S.M. Ansari, C.G. Farquharson, and S.P. MacLachlan, Geophysical Journal International, 210(1):105-129, 2017

  • Preconditioning a mass-conserving discontinuous Galerkin discretization of the Stokes Equations, J. Adler, T. Benson, and S. MacLachlan, Numer. Linear Alg. Appl., 24(3):e2047, 2017

  • Effect of thermocapillary stress on slip length for a channel textured with parallel ridges, M. Hodes, T. Kirk, G. Karamanis, and S. MacLachlan, Journal of Fluid Mechanics, 814:301-324, 2017.

  • A deflation technique for detecting multiple liquid crystal equilibrium states, J.H. Adler, D.B. Emerson, P.E. Farrell, and S.P. MacLachlan, SIAM J. Sci. Comp., 39(1):B29-B52, 2017.

  • Effect of meniscus curvature on apparent thermal slip, L. Steigerwalt Lam, M. Hodes, G. Karmanis, T. Kirk, and S. MacLachlan, Journal of Heat Transfer, 138(12):122004, 2016.

  • A first-order system Petrov-Galerkin discretisation for a reaction-diffusion problem on a fitted mesh, J. Adler, S. MacLachlan, and N. Madden, IMA J. Numer. Anal., 36(3):1281-1309, 2016

  • Constrained optimization for liquid crystal equilibria, J. H. Adler, D. B. Emerson, S. P. MacLachlan, and T. A. Manteuffel, SIAM J. Sci. Comp., 38(1):B50-B76, 2016

  • Monolithic multigrid methods for two-dimensional resistive magnetohydrodynamics, J. H. Adler, T. R. Benson, E. C. Cyr, S. P. MacLachlan, and R. S. Tuminaro, SIAM J. Sci. Comp., 38(1):B1-B24, 2016

  • Energy minimization for liquid crystal equilibrium with electric and flexoelectric effects, J. H. Adler, T. J. Atherton, T. R. Benson, D. B. Emerson, and S. P. MacLachlan, SIAM J. Sci. Comp., 37(5):S157-S176, 2015.

  • An energy-minimization finite-element approach for the Frank-Oseen model of nematic liquid crystals, J. H. Adler, T. J. Atherton, D. B. Emerson, and S. P. MacLachlan, SIAM J. Numer. Anal., 53(5):2225-2254, 2015.

  • A generalized predictive analysis tool for multigrid methods, S. Friedhoff and S. MacLachlan, Numer. Linear Alg. Appl., 22:618-647, 2015.

  • Effect of evaporation and condensation at menisci on apparent thermal slip, M. Hodes, L. Steigerwalt Lam, A. Cowley, S. MacLachlan, and R. Enright, Journal of Heat Transfer, 137(7):071502, 2015

  • Implied volatility and the risk-free rate of return in options markets, M. Bianconi, S. MacLachlan, and M. Sammon, North American Journal of Economics and Finance, 31:1-26, 2015.

  • Parallel time integration with multigrid, R.D. Falgout, S. Friedhoff, Tz.V. Kolev, S.P. MacLachlan, and J.B. Schroder, SIAM J. Sci. Comput., 36:C625-C661, 2014.

  • Mathematical and computational models of incompressible materials subject to shear, J.H. Adler, L. Dorfmann, D. Han, S. MacLachlan, and C. Paetsch, IMA Journal of Applied Mathematics, 79(5):889-914, 2014.

  • Theoretical bounds for algebraic multigrid performance: review and analysis, S. MacLachlan and L. Olson, Numer. Linear Alg. Appl., 21(2):194-220, 2014.

  • Local Fourier analysis of space-time relaxation and multigrid schemes, S. Friedhoff, S. MacLachlan and C. Börgers, SIAM J. Sci. Comput., 35:S250-276, 2013.

  • Robust solution of singularly perturbed problems using multigrid methods, S. MacLachlan and N. Madden, SIAM J. Sci. Comput., 35:A2225-A2254, 2013.

  • Comparison of the deflated preconditioned conjugate gradient method and algebraic multigrid for composite materials, T.B. Jönsthövel, M.B. van Gijzen, S. MacLachlan, C. Vuik, and A. Scarpas, Computational Mechanics, 50:321-333, 2012.

  • Modification and compensation strategies for threshold-based incomplete factorizations, S. MacLachlan, D. Osei-Kuffuor, and Y. Saad, SIAM J. Sci. Comput., 34:A48-A75, 2012.

  • Robust and Adaptive Multigrid Methods: comparing structured and algebraic approaches, S.P. MacLachlan, J.D. Moulton, and T.P. Chartier, Numerical Linear Algebra with Applications, 19:389-413, 2012.

  • Iterative parameter choice and algebraic multigrid for anisotropic diffusion denoising, D. Chen, S. MacLachlan, and M. Kilmer, SIAM J. Sci. Comp., 33:2972-2994, 2011.

  • Local Fourier analysis for multigrid with overlapping smoothers applied to systems of PDEs, S.P. MacLachlan and C.W. Oosterlee, Numerical Linear Algebra with Applications, 18:751-774, 2011.

  • A fast method for the solution of the Helmholtz equation, E. Haber and S. MacLachlan, J. Comp. Phys., 230(12):4403-4418, 2011.

  • On iterative methods for the incompressible Stokes problem, M. ur Rehman, T. Geenen, C. Vuik, G. Segal, and S.P. MacLachlan, International Journal for Numerical Methods in Fluids, 65(10):1180-1200, 2011.

  • A geometric multigrid method based on L-shaped coarsening for PDEs on stretched grids, H. bin Zubair, S.P. MacLachlan, and C.W. Oosterlee, Numerical Linear Algebra with Applications, 17:871-894, 2010.

  • Adaptive reduction-based multigrid for nearly singular and highly disordered physical systems, J. Brannick, A. Frommer, K. Kahl, S. MacLachlan, and L. Zikatanov, Electronic Transactions on Numerical Analysis, 37:276-295, 2010.

  • A Comparison of Two-Level Preconditioners based on Multigrid and Deflation, J.M. Tang, S.P. MacLachlan, R. Nabben, and C. Vuik, SIAM J. Matrix Anal. Appl., 31:1715-1739, 2010.

  • An angular multigrid method for monoenergetic particle beams in Flatland, C. Börgers and S. MacLachlan, J. Comp. Phys., 229:2914-2931, 2010.

  • Scalable robust solvers for unstructured FE modeling applications; solving the Stokes equation for models with large, localized viscosity contrasts, T. Geenen, M. ur Rehman, S.P. MacLachlan, G. Segal, C. Vuik, A.P. van den Berg, and W. Spakman, Geochemistry, Geophysics, Geosystems, 10(9), 2009.

  • A multigrid-based shifted-Laplacian preconditioner for a fourth-order Helmholtz discretization, N. Umetani, S.P. MacLachlan, and C.W. Oosterlee, Numerical Linear Algebra with Applications, 16:603-626, 2009.

  • Fast and robust solvers for pressure correction in bubbly flow problems, S.P. MacLachlan, J.M. Tang, and C. Vuik, J. Comp. Phys., 227:9742-9761, 2008.

  • Algebraic multigrid solvers for complex-valued matrices, S.P. MacLachlan and C.W. Oosterlee, SIAM J. Sci. Comp., 30:1548-1571, 2008.

  • Greedy coarsening strategies for non-symmetric problems, S. MacLachlan and Y. Saad, SIAM J. Sci. Comp., 29:2115-2143, 2007.

  • A greedy strategy for coarse-grid selection, S. MacLachlan and Y. Saad, SIAM J. Sci. Comp., 29:1825-1853, 2007.

  • Adaptive reduction-based AMG, S. MacLachlan, T. Manteuffel, and S. McCormick, Numerical Linear Algebra with Applications, 13:599-620, 2006.

  • An energy-based AMG coarsening strategy , J. Brannick, M. Brezina, S. MacLachlan, T. Manteuffel, S. McCormick, and J. Ruge, Numerical Linear Algebra with Applications, 13:133-148 2006.

  • Multilevel upscaling through variational coarsening, S.P. MacLachlan and J.D. Moulton, Water Resources Research, 42, 2006.

  • Adaptive algebraic multigrid, M. Brezina, R. Falgout, S. MacLachlan, T. Manteuffel, S. McCormick, and J. Ruge, SIAM J. Sci. Comp., 27:1261-1286, 2006.

  • Adaptive smoothed aggregation (aSA) multigrid, M. Brezina, R. Falgout, S. MacLachlan, T. Manteuffel, S. McCormick, and J. Ruge, SIAM Review, 47:317-346, 2005.

  • Adaptive smoothed aggregation (aSA), M. Brezina, R. Falgout, S. MacLachlan, T. Manteuffel, S. McCormick, and J. Ruge, SIAM J. Sci. Comp., 25:1896-1920, 2004.

    Refereed Proceedings:
  • Adaptive smoothed aggregation in Lattice QCD, J. Brannick, M. Brezina, D. Keyes, O. Livne, I. Livshits, S. MacLachlan, T. Manteuffel, S. McCormick, J. Ruge, and L. Zikatanov, pages 505-512 in Domain Decomposition Methods in Science and Engineering XVI, Lecture Notes in Computational Science and Engineering, Springer, 2007.

    PhD Thesis:
  • Improving robustness in multiscale methods, S. MacLachlan, PhD Thesis, July 2004.

    Other:
  • Isoperimetric relations between Dirichlet and Neumann eigenvalues, G. Cox, S. MacLachlan, and L. Steeves, 2020.

  • The role of energy minimization in algebraic multigrid interpolation, J. Brannick, S. MacLachlan, J. Schroder, and B. Southworth, 2019.

  • Constrained optimization for liquid crystal equilibria: extended results, J. H. Adler, D. B. Emerson, S. P. MacLachlan, and T. A. Manteuffel, technical report, 2014; also available at arXiv.org.

  • An energy-minimization finite-element approach for the Frank-Oseen model of nematic liquid crystals: continuum and discrete analysis, J. H. Adler, T. J. Atherton, D. B. Emerson, and S. P. MacLachlan, technical report, 2014; also available at arXiv.org.

  • Robust solution of singularly perturbed problems using multigrid methods; analysis and numerical results in one and two dimensions, S. MacLachlan and N. Madden, technical report, 2012.

  • Scalable robust solvers for unstructured FE geodynamic modeling applications; solving the Stokes equation for models with large localized viscosity contrasts in 3D spherical domains, T. Geenen, M. ur Rehman, S. P. MacLachlan, G. Segal, C. Vuik, A. P. van den Berg, and W. Spakman, V European Conference on Computational Fluid Dynamics ECCOMAS CFD 2010, 2010.

  • Local post-processing for locally conservative fluxes in the Galerkin method for groundwater flows, E.T. Coon, S.P. MacLachlan, and J.D. Moulton, Los Alamos National Laboratory Technical Report LA-UR 09-08292, 2009.

  • Contaminant transport in municipal water systems, S. Ali et al., Proceedings of the 3rd PIMS Industrial Problem Solving Workshop, Victoria, BC, June 1999.



  • Teaching Overview
    All teaching from Spring 2008 - Spring 2014 was at Tufts University. From Fall 2014 onwards, all teaching is at Memorial University of Newfoundland.

    Winter 2020:
  • Math 6204, Iterative Methods in Numerical Linear Algebra

    Fall 2019:
  • Math 2260, Ordinary Differential Equations I
  • Math 6210, Numerical Solution of Differential Equations

    Winter 2018:
  • Math 6204, Iterative Methods in Numerical Linear Algebra

    Fall 2017:
  • Math 6210, Numerical Solution of Differential Equations

    Fall 2016:
  • Math 2050, Linear Algebra I
  • Math 6210, Numerical Solution of Differential Equations

    Winter 2016:
  • Math 6204, Iterative Methods in Numerical Linear Algebra

    Fall 2015:
  • Math 2050, Linear Algebra I

    Winter 2015:
  • Math 2260, Ordinary Differential Equations I
  • Math 6201, Numerical Methods for Time Dependent Differential Equations

    Fall 2014:
  • Math 2260, Ordinary Differential Equations I

    Spring 2014:
  • Math 51, Differential Equations

    Fall 2013:
  • Math 87, Mathematical Modeling and Computing

    Spring 2013:
  • Math 250-01, Numerical Methods for PDEs
  • Math 250-04, Seminar in Computational and Applied Mathematics

    Fall 2012:
  • Math 250-03, Linear Partial Differential Equations
  • Math 87, Mathematical Modeling and Computing

    Spring 2012:
  • Math 250-02, Classic Papers in Applied Mathematics
  • Math 13, Calculus III

    Fall 2011:
  • Math 50-02, Mathematical Modeling and Computing
  • Math 13, Calculus III

    Spring 2010:
  • Math 250-03, Numerical Methods for PDEs
  • Math 13, Calculus III

    Fall 2009:
  • Math 135, Real Analysis I
  • Math 13, Calculus III

    Spring 2009:
  • Math 136, Real Analysis II
  • Math 38, Differential Equations

    Fall 2008:
  • Math 135, Real Analysis I
  • Math 38, Differential Equations

    Spring 2008:
  • Math 38, Differential Equations

    Past Courses:
  • WI4145, Computational Science and Engineering, TU-Delft
  • APPM 7400, Topics in Applied Mathematics: Multigrid Methods, CU-Boulder
  • Lead Teaching Assistant, Department of Applied Mathematics, CU-Boulder
  • GEEN 1350, Calculus I Workgroup, CU-Boulder
  • APPM 2350, Calculus III, CU-Boulder
  • Math 100, Calculus I, UBC

    Other:
  • SIAM student chapter lecture on the post-doctoral job search, April 14, 2008, slides (.pdf)
  • Tufts Mathematical Contest in Modeling team
  • 2009 BGCE Student Prize Committee


  • The design of this page was stolen (with permission) from Chad Westphal.