Computational Earth Scientist
Hydrogeochemical Dynamics Team
Earth and Aquatic Sciences Group
Environmental Sciences Division
Oak Ridge National Laboratory
I am currently a computational Earth scientist in the Hydrogeochemical Dynamics Team of the Earth and Aquatic Sciences Group within the Environmental Sciences Division at Oak Ridge National Laboratory. I came to ORNL in 2004 after completing my Ph.D. in computer science (with a specialization in computational science) under the direction of Andreas Stathopoulos at the College of William and Mary in beautiful Williamsburg, Virginia. My graduate studies were supported by a Department of Energy Computational Science Graduate Fellowship administered by the fine folks at Krell Institute, and for this I shall be forever grateful. I was fortunate enough to complete my fellowship practicum at Los Alamos National Laboratory under the masterful tutelage of Peter Lichtner of the Hydrology, Geochemistry and Geology group. Prior to my graduate studies, I studied geology and physics (in addition to Volunteers Football, of course) in the hospitable environs of the University of Tennessee, Knoxville, as a Chancellor's Scholar.
My broad interest is in developing and applying numerical methods and software to enable the solution of very computationally challenging problems that arise in the natural sciences. Over the past several years, my work in the natural sciences has increasingly focused on Earth and the environment, with particular foci in hydrologic modeling and in data-mining of large environmental data sets (mostly derived from remote sensing). My interests as a computer scientist are aligned with my interest in the natural sciences and mostly fall into two categories. The first is numerical methods and software for the solution of partial differential equations, and particularly in iterative methods for solving the sparse algebraic systems that arise from their discretization. The second is parallel implementation issues and the interplay between numerical algorithms and computer architecture. Algorithms designed with one kind of architecture in mind may perform very poorly on another. For instance, codes that are very efficient on superscalar processors might perform extremely poorly on vector processor machines. My interest is in developing scalable, parallel numerical applications that not only possess good numerical properties, but are also tailored to effectively utilize their target resources.
Glenn E. Hammond, Peter C. Lichtner, and Richard Tran Mills, 2013. "Evaluating the Performance of Parallel Subsurface Simulators: An Illustrative Example with PFLOTRAN". Submitted to Water Resources Research.
Lois Curfman McInnes, Barry Smith, Hong Zhang, and Richard Tran Mills, 2012. "Hierarchical and Nested Krylov Methods for Extreme-Scale Computing". Preprint ANL/MCS-P2097-0612, June 2012. Submitted to Parallel Computing.
Richard Tran Mills, Jitendra Kumar, Forrest M. Hoffman, William W. Hargrove, Joseph P. Spruce, Steven P. Norman. "Identification and Visualization of Dominant Patterns and Anomalies in Remotely Sensed Vegetation Phenology Using a Parallel Tool for Principal Components Analysis". To appear in Proceedings of the 2013 International Conference on Computational Science.
Forrest M. Hoffman, Jitendra Kumar, Richard Tran Mills, and William W. Hargrove, 2013. "Representativeness-Based Sampling Network Design for the Arctic". To appear in Landscape Ecology.
Chu-Lin Cheng, Edmund Perfect, and Richard Tran Mills, 2013. "Forward Prediction of Height-Averaged Capillary Pressure-Saturation Parameters Using the BC_vG Upscaler". Vadose Zone Journal, DOI: 10.2136/vzj2012.0174
Richard Tran Mills, Forrest M. Hoffman, Jitendra Kumar, and William W. Hargrove, 2011. "Cluster Analysis-based Approaches for Geospatiotemporal Data Mining of Massive Data Sets for Identification of Forest Threats". In Mitsuhisa Sato, Satoshi Matsuoka, Peter M. Sloot, G. Dick van Albada, and Jack Dongarra, editors, Proceedings of the International Conference on Computational Science (ICCS 2011), volume 4 of Procedia Comput. Sci., pages 1612–1621, Elsevier, Amsterdam. ISSN 1877-0509. DOI:10.1016/j.procs.2011.04.174
Forrest M. Hoffman, J. Walter Larson, Richard Tran Mills, Bjørn-Gustaf J. Brooks, Auroop R. Ganguly, William W. Hargrove, Jian Huang, Jitendra Kumar, and Ranga R. Vatsavai, 2011. "Data Mining in Earth System Science (DMESS 2011)". In Mitsuhisa Sato, Satoshi Matsuoka, Peter M. Sloot, G. Dick van Albada, and Jack Dongarra, editors, Proceedings of the International Conference on Computational Science (ICCS 2011), volume 4 of Procedia Comput. Sci., pages 1450–1455, Elsevier, Amsterdam. ISSN 1877-0509. DOI:10.1016/j.procs.2011.04.157
Jitendra Kumar, Richard Tran Mills, Forrest M. Hoffman, and William W. Hargrove, 2011. "Parallel k-Means Clustering for Quantitative Ecoregion Delineation Using Large Data Sets". In Mitsuhisa Sato, Satoshi Matsuoka, Peter M. Sloot, G. Dick van Albada, and Jack Dongarra, editors, Proceedings of the International Conference on Computational Science (ICCS 2011), volume 4 of Procedia Comput. Sci., pages 1602–1611, Elsevier, Amsterdam. ISSN 1877-0509. DOI:10.1016/j.procs.2011.04.173.
Forrest M. Hoffman, Richard T. Mills, Jitendra Kumar, Srinivasa S. Vulli, and William W. Hargrove, 2010. "Geospatiotemporal Data Mining in an Early Warning System for Forest Threats in the United States". Proceedings of the 2010 IEEE International Geoscience and Remote Sensing Symposium (IGARSS 2010), July 25, 2010, Honolulu, Hawaii, USA. Invited paper.
Richard T. Mills, Vamsi Sripathi, G. (Kumar) Mahinthakumar, Glenn E. Hammond, Peter C. Lichtner, Barry F. Smith, 2010. "Engineering PFLOTRAN for Scalable Performance on Cray XT and IBM BlueGene Architectures". Proceedings of SciDAC 2010, July 11-15, 2010, Chattanooga, TN, USA. Invited paper.
Chuan Lu, Peter C. Lichtner, Glenn E. Hammond, and Richard T. Mills, 2010. "Evaluating variable switching and flash methods in modeling carbon sequestration in deep geologic formations using PFLOTRAN". Proceedings of SciDAC 2010, July 11-15, 2010, Chattanooga, TN, USA. Invited paper.
R. T. Mills, G. E. Hammond, P. C. Lichtner, V. Sripathi, G. Mahinthakumar, and B. F. Smith, 2009. "Modeling subsurface reactive flows using leadership-class computing". Journal of Physics: Conference Series, v. 180 (Proceedings of SciDAC 2009), p. 012062. DOI: 10.1088/1742-6596/180/1/012062. Invited paper.
G.E. Hammond, P.C. Lichtner, R.T. Mills, and C. Lu, 2008. "Towards petascale computing in geosciences: Application to the Hanford 300 Area". Journal of Physics: Conference Series, v. 125 (Proceedings of SciDAC 2008), p. 012051. DOI: 10.1088/1742-6596/125/1/012051. Invited paper.
Forrest M. Hoffman, William W. Hargrove, Richard T. Mills, Salil Mahajan, David J. Erickson, and Robert J. Oglesby, 2008. "Multivariate Spatio-Temporal Clustering (MSTC) as a Data Mining Tool for Environmental Applications". Proceedings of the iEMSs Fourth Biennial Meeting: International Congress on Environmental Modelling and Software (iEMSs 2008), ISBN 978-84-7653-074-0, International Environmental Modelling and Software Society, Barcelona, Catalonia, Spain, July 2008.
D. J. Erickson III, R. T. Mills, J. Gregg, T. J. Blasing, F. M. Hoffman, R. J. Andres, M. Devries, Z. Zhu, S. R. Kawa, 2008. "An estimate of monthly global emissions of anthropogenic CO2: Impact on the seasonal cycle of atmospheric CO2". Journal of Geophysical Research - Biogeosciences, v. 113, G01023. DOI 10.1029/2007JG000435.
S. R. Alam, R. F. Barrett, M. R. Fahey, J. A. Kuehn, O. E. B. Messer, R. T. Mills, P. C. Roth, J. S. Vetter, P. H. Worley, 2008. "An evaluation of the Oak Ridge National Laboratory Cray XT3". International Journal of High Performance Computing Applications, February 2008, v. 22, no. 1, pp. 52-80.
R. T. Mills, C. Lu, P. C. Lichtner, and G. E. Hammond, 2007. "Simulating subsurface flow and transport on ultrascale computers using PFLOTRAN". Journal of Physics: Conference Series, v. 78 (Proceedings of SciDAC 2007). DOI 10.1088/1742-6596/78/1/012051. Invited paper.
R. T. Mills, C. Yue, A. Stathopoulos, and D. S. Nikolopoulos, 2007. "Runtime and programming support for memory adaptation in scientific applications via local disk and remote memory". Journal of Grid Computing, v. 5, no. 2, pp. 213-234. DOI 10.1007/s10723-007-9075-7.
P. K. V. V. Nukala, S. Simunovic, and R. T. Mills, 2006. "Statistical physics of fracture: scientific discovery through high-performance computing". Journal of Physics: Conference Series, v. 46, pp. 278-291 (Proceedings of SciDAC 2006). DOI 10.1088/1742-6596/46/1/039. Invited paper.
C. Yue, R. T. Mills, A. Stathopoulos, and D. S. Nikolopoulos, 2006. "Runtime support for memory adaptation in scientific workloads via local disk and remote memory". Proceedings of the 15th IEEE International Symposium on High Performance Distributed Computing. Paris, France, June 2006. Finalist for best paper award.
E. F. D'Azevedo, M. R. Fahey, and R. T. Mills, 2005. "Vectorized sparse matrix multiply for compressed row storage format". Lecture Notes in Computer Science, 3514:99-106, 2005.
R. T. Mills, A. Stathopoulos, and D. S. Nikolopoulos, 2004. "Adapting to memory pressure from within scientific applications on multiprogrammed clusters of workstations". Proceedings of the 18th IEEE International Parallel and Distributed Processing Symposium (IPDPS 2004).
J. R. McCombs, R. T. Mills, and A. Stathopoulos, 2003. "Dynamic load balancing of an iterative eigensolver on networks of heterogeneous clusters". Proceedings of the 17th International Parallel and Distributed Processing Symposium (IPDPS 2003).
H. H. Mills and R. T. Mills, 2001. "Evolution of undercut slopes on abandoned incised meanders in the Eastern Highland Rim of Tennessee, USA". Geomorphology 38, 317-336. DOI 10.1016/S0169-555X(00)00104-5.
R. T. Mills, A. Stathopoulos and E. Smirni, 2001. "Algorithmic modifications to the Jacobi-Davidson parallel eigensolver to dynamically balance external CPU and memory load". Proceedings of the International Conference on Supercomputing (ICS 2001), Sorrento, Italy, June 18-22, (2001), 454--463.
R. T. Mills, F. M. Hoffman, P. H. Worley, K. S. Perumalla, A. A. Mirin, G. E. Hammond, and B. F. Smith, 2009. "Coping at the User-Level with Resource Limitations in the Cray Message Passing Toolkit MPI at Scale: How Not to Spend Your Summer Vacation". Proceedings of the 2009 Cray User Group Meeting, May 4-7, 2009, Atlanta, GA.
R. T. Mills, V. Sripathi, G. Mahinthakumar, G. E. Hammond, P. C. Lichtner, and B. F. Smith, 2009. "Experiences and Challenges Scaling PFLOTRAN, a PETSc-based Code for Subsurface Reactive Flow Simulations, Towards the Petascale on Cray XT Systems". Proceedings of the 2009 Cray User Group Meeting, May 4-7, 2009, Atlanta, GA.
S. D. Ahern, S. R. Alam, M. R. Fahey, R. J. Hartman-Baker, R. F. Barrett, R. A. Kendall, D. B. Kothe, O. E. B. Messer, R. T. Mills, R. Sankaran, A. N. Tharrington, J. B. White III. "Scientific Application Requirements for Leadership Computing at the Exascale". Proceedings of the 2008 Cray User Group Meeting, May 5-8, 2008, Helsinki, Finland. Also available as ORNL/TM-2007/238.
S. R. Alam, R. F. Barrett, M. R. Fahey, O. E. B. Messer, R. T. Mills, P. C. Roth, J. S. Vetter, and P. H. Worley, 2006. "Evaluation of the Cray XT3 at ORNL: a status report". Proceedings of the Cray User Group 2006 Technical Meeting, Lugano, Switzerland, May 8-11, 2006.
S. Akella, M. C. Smith, R. T. Mills, S. R. Alam, R. F. Barrett, and J. S. Vetter, 2005. "Sparse matrix-vector multiplication kernel on a reconfigurable computer". Refereed extended abstract in The 9th Annual Workshop on High Performance Embedded Computing (HPEC), MIT Lincoln Laboratory, Boston, Massachusetts, September 20-22, 2005.
R. T. Mills, E. F. D'Azevedo, and M. R. Fahey, 2005. "Progress towards optimizing the PETSc numerical toolkit on the Cray X1". Proceedings of the Cray User Group 2005 Technical Meeting, Albuquerque, NM, May 16-19, 2005. (Presentation slides also available.)
R. T. Mills, 2004. "Dynamic adaptation to CPU and memory load in scientific applications". Ph.D. dissertation, Department of Computer Science, College of William and Mary, Williamsburg, VA.
P. C. Lichtner, G. E. Hammond, C. Lu, R. T. Mills, J. D. Moulton, B. Philip, B. F. Smith, A. J. Valocchi, S. Yabusaki, 2008. "Towards petascale computing in geosciences: Application to the Hanford 300 Area". SciDAC 2008, Seattle, WA, July 13-17.
P. C. Lichtner, C. Lu, G. E. Hammond, B. Philip, J. D. Moulton, R. T. Mills, B. F. Smith, A. J. Valocchi, K. Nakshatrala, S. Yabusaki, 2008. "The Next-Generation Massively Parallel Reactive Flow and Transport Code PFLOTRAN: Application to CO2 Storage in Saline Aquifers". Joint BES-BER-ASCR-FE Research Symposium on Basic Research Relevant to CO2 Sequestration, Gaithersburg, MD, March 2008.
F. M. Hoffman, S. Mahajan, W. W. Hargrove, R. T. Mills, and A. Del Genio, 2008. "A cluster analysis approach to comparing atmospheric radiation measurement (ARM) data with global climate model (GCM) results". 18th Atmospheric Radiation Measurement (ARM) Science Team Meeting, Norfolk, VA, March 2008. Winner of People's Choice award for best poster.
F. M. Hoffman, W. W. Hargrove, R. T. Mills, A. D. Del Genio, J. V. Pittman, 2007. "From measurements to models: cross-comparison of measured and simulated behavioral states of the atmosphere". 17th Atmospheric Radiation Measurement (ARM) Science Team Meeting, Monterey, CA, March 2007.
P. C. Lichtner, C. Lu, B. Philip, J. D. Moulton, G. E. Hammond, S. Yabusaki, R. T. Mills, B. F. Smith, A. J. Valocchi, 2007. "Modeling multiscale-multiphase-multicomponent subsurface reactive flows using advanced computing". DOE SciDAC-2 Organization Workshop, Atlanta, GA, February 5-6, 2007.
C. Lu, P. C. Lichtner, I. N. Tsimpanogiannis, and R. T. Mills, 2005. "Parametric study of CO2 sequestration in geologic media using the massively parallel computer code PFLOTRAN". AGU Fall Meeting, San Francisco, CA, 2005.
R. T. Mills, P. C. Lichtner, and C. Lu, 2005. "PFLOTRAN: A massively parallel simulator for groundwater flow and transport". SC|05 (SuperComputing 2005), Seattle, WA, 2005.
R. T. Mills, 2006. "An introduction to the Cray X1E". 2006 National Center for Computational Sciences Users Meeting, February 14, 2006.
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