Julio López, Ph.D.

Parallel Data Laboratory
Computer Science Department
Carnegie Mellon University
5000 Forbes Avenue
Pittsburgh, PA 15213-3890 USA

Professional Interests

Parallel and distributed systems and applications, computational database systems, scalable I/O, indexing techniques for large multi-dimensional spatial datasets, data compression and visualization. In particular, I am interested in the interaction between applications and high-end storage systems, such as those found in scientific and enterprise computing.


Carnegie Mellon University, Pittsburgh, Pennsylvania, USA.
Ph.D. Electrical and Computer Engineering. May 2007.
Thesis: "Methods for Querying Compressed Wavefields". I developed techniques to compress, index and query large wavefield datasets in their compressed representation (i.e., compressed domain). This approach turns an I/O intensive problem into a massively parallel computational workload.

Carnegie Mellon University, Pittsburgh, PA, USA.
M.S. Electrical and Computer Engineering, May 2000.
Thesis: "Dv -- A framework for remote visualization". Developed a library to create visual representations, such as images or 3D models, of datasets stored at remote sites.

Universidad EAFIT, Medellín, Colombia.
Ingeniero de Sistemas (~ B.S. in Computer Science). June 1996.
Graduated at the top of my class. Throughout my studies, every semester I had the highest GPA in my class.
Graduation Project: "Mercury -- A Protocol for Communications in Distributed Virtual Environments". My graduation project served as the communication layer of a larger project intending to implement a prototype Distributed Virtual Reality system.

Professional Experience

Carnegie Mellon University. Pittsburgh, PA, USA. Oct 2007 -- present. Systems Scientist Faculty, Computer Science Department, Parallel Data Laboratory.

Hewlett-Packard Laboratories, Palo Alto, CA USA. June 2000 - September 2000.
Intern Researcher: Designed and implemented a mechanism to aggregate the bandwidth of the the long-range links of multiple personal devices.

Center for Educational Computing Initiatives at Massachusetts Institute of Technology , Boston, MA USA. August 1997 - July 1998.
Visiting Engineer: Developed a library to annotate, classify, and store multimedia objects.
Designed and implemented a caching architecture for low bandwidth networks.

Universidad EAFIT, Proyecto Conexiones, Medellín, Colombia. January 1997 - July 1997. Software Engineer.

Universidad EAFIT, Medellín, Colombia. June 1995 - January 1997.
Computer security coordinator and system administrator of several Solaris / HP-UX / Linux / MS Windows machines and Cisco routers. Configured, deployed and managed numerous network services for these environments (e.g., TCP/IP, DHCP, Web, DBMS, mail IMAP/SMTP, remote access, etc).

Corporación Nacional de Ahorro y Vivienda CONAVI, now part of Groupo Bancolombia. , Medellín, Colombia. January 1995 - June 1995.
EDP Auditing: Performance Evaluation and Security of the corporate network.


Robson Cordeiro, Caetano Traina Jr., Agma Traina, Julio López, U. Kang, Christos Faloutsos. Clustering Very Large Multi-dimensional Datasets with MapReduce. In Proceedings of the ACM SIGKDD Conference on Knowledge Discovery and Datamining (KDD), San Diego CA, August, 2011. (bib, pdf)

Kai Ren, Julio López and Garth Gibson. Otus: Resource Attribution in Data-Intensive Clusters. MapReduce: The Second International Workshop on MapReduce and its Applications. San Jose, CA, June 2011. (bib, pdf)

Julio López, Colin Degraf, Tiziana DiMatteo, Bin Fu, Eugene Fink and Garth Gibson, Recipes for Baking Black Forest Databases: Building and Querying Black Hole Merger Trees from Cosmological Simulations. In Proceedings of the 23rd International Conference Scientific and Statistical Database Management (SSDBM 2011), Portland OR, July 2011 (Extended version available as a TR). (bib, pdf)

Ricardo Taborda, Julio López, Haydar Karaoglu, John Urbanic, Jacobo Bielak. Speeding Up Finite Element Wave Propagation for Large-Scale Earthquake Simulations. Technical Report CMU-PDL-10-109, Parallel Data Laboratory, Carnegie Mellon University, October 2010. (bib, pdf)

Bin Fu, Kai Ren, Julio López, Eugene Fink, and Garth Gibson. DiscFinder: A data-intensive scalable cluster finder for astrophysics (extended version). Technical Report CMU-PDL-10-104, Parallel Data Laboratory, Carnegie Mellon University, October 2010. (bib, pdf)

Bin Fu, Kai Ren, Julio López, Eugene Fink, and Garth Gibson. DiscFinder: A data-intensive scalable cluster finder for astrophysics. In Proceedings of the ACM International Symposium on High Performance Distributed Computing (HPDC), Chicago, IL. June, 2010. (Extended version available as a technical report CMU-PDL-10-104). (bib, pdf)

Julio López, Leonardo Ramirez-Guzman, Jacobo Bielak, and David O'Hallaron. BEMC: A Searchable, Compressed Representation for Large Seismic Wavefields. In proceedings of the 22nd International Conference Scientific and Statistical Database Management (SSDBM 2010), Heidelberg, Germany, June 2010. (abstract, bib, pdf)

Michael A. Kozuch, Michael P. Ryan, Richard Gass, Steven W. Schlosser, David O'Hallaron, James Cipar, Elie Krevat, Michael Stroucken, Julio López, Gregory R. Ganger. Tashi: Location-aware Cluster Management. In proceeding of the First Workshop on Automated Control for Datacenters and Clouds (ACDC'09), Barcelona, Spain, June 2009. (bib, pdf)

Swapnil Patil, Garth Gibson, Gregory R. Ganger, Julio López, Milo Polte, Wittawat Tantisiroj, Lin Xiao. In Search of an API for Scalable File Systems: Under the table or above it?. In Proceedings of the First USENIX Workshop on Cloud Computing (HotCloud 2009), June 2009. (bib, pdf)

Steven Schlosser, Michael Ryan, Ricardo Taborda, Julio López, David O'Hallaron and Jacobo Bielak. Materialized community ground models for large-scale earthquake simulation. In Proceedings of the Supercomputing Conference (SC'08), Austin, TX, November 2008. (bib, pdf)

Grant Mackey, Saba Sehrish, John Bent, Julio López, Salman Habib, Jun Wang. Introducing Map-Reduce to High End Computing. In Proceedings of the 3rd Petascale Data Storage Workshop, Austin, TX, November 2008. (bib, pdf)

Julio López. Methods for Querying Compressed Wavefields. Ph.D. Thesis. Electrical and Computer Engineering Department, Carnegie Mellon University. Pittsburgh, PA. May 2007. (abstract, bib)

Michael Mesnier, Matthew Wachs, Julio López, Raja Sambasivan, James Hendricks and Greggory Ganger. //TRACE -- Parallel Trace Replay with Approximate Causal Events. In proceedings of the 5th Conference on File And Storage Technologies (FAST'07), San Jose, CA, February 13-16 2007. (abstract, bib, pdf)

Leonardo Ramirez-Guzman, Ricardo Taborda, Jacobo Bielak, Omar GhattasE.J. Kim, Julio López, David O'Hallaron, and Tiankai Tu. Scaling up TeraShake: A 1-Hz Case Study. In EOS Trans. American Geophysical Union (AGU). Volume 87(52), San Francisco, CA, December 2006

Hongfeng Yu, Tiankai Tu, Jacobo Bielak, Omar Ghattas, Julio López, Kwan-Liu Ma, David O.Hallaron, Leonardo Ramirez-Guzman, Nathan Stone, Ricardo Taborda-Rios, and John Urbanic. Remote Runtime Steering of Integrated Terascale Simulation and Visualization. In Proceedings of the Supercomputing Conference (SC06), Tampa, Fl, November 2006. Winner of the HPC Analytics Challenge at SC06.

Ricardo Taborda, Leonardo Ramirez-Guzman, Tiankai Tu, Julio López, Jacobo Bielak and David O'Hallaron. Terashake simulations using Hercules: analysis and comparison., In Proceedings of the SCEC Annual Meeting, Palm Springs, CA , September 2006

Stratos Papadomanolakis, Anastassia Ailamaki, Julio López, Tiankai Tu, David R. O'Hallaron, Gerd Heber. Efficient query processing on unstructured tetrahedral meshes. In proceedings of the international conference on Management of Data (SIGMOD 2006), Chicago, IL. June 2006, pp 551-562. (abstract, bib, pdf)

Eno Thereska, Brandon Salmon, John Strunk, Matthew Wachs, Michael Abd-El-Malek, Julio López, Gregory R. Ganger. Stardust: Tracking activity in a distributed storage system. In proceedings of the joint international conference on Measurement and Modeling of Computer Systems (SIGMETRICS'06), Saint-Malo, France. June 26th-30th 2006. (abstract, bib, pdf)

Julio López, David O'Hallaron and Tiankai Tu. Big Wins with a Small Application-Aware Cache. In proceedings of the Supercomputing Conference (SC04), Pittsburgh, PA, November 2004. (abstract, bib, ps, pdf)

Minster, J., Olsen, K B., Moore, R., Day, S., Maechling, P. and Jordan, T. and Faerman, M. and Cui, Y. and Ely, G. and Hu, Y. and Shkoller, B. and Marcinkovich, C. and Bielak, J. and Okaya, D. and Archuleta, R. and Wilkins-Diehr, N. and Cutchin, S. and Chourasia, A. andKremenek, G. and Jagatheesan, A. and Brieger, L. and Majundar, A. and Chukkapalli, G. and Xin, Q. and Banister, B. and Thorp, D. and Kovatch, P. and Diegel, L. and Sherwin and Thiebaux, M. and López J., The SCEC TeraShake Earthquake Simulation, In EOS Trans. American Geophysical Union (AGU), Volume 47, 2004. (abstract, bib)

Tiankai Tu and David R. O'Hallaron and Julio López, Etree: a database-oriented method for generating large octree meshes, Journal of Engineering with Computers, Volume 20, Number 2, 2004, pages 117--128. (bib, pdf)

Volkan Akcelik, Jacobo Bielak, George Biros, Ioannis Epanomeritakis, Antonio Fernandez, Omar Ghattas, Eui Joong Kim, Julio López, David O'Hallaron, Tiankai Tu, and John Urbanic. High Resolution Forward and Inverse Earthquake Modeling on Terasacale Computers, In Proceedings of the Supercomputing Conference (SC03), Phoenix, AZ, 2003. (bib, pdf).

Tiankai Tu, David R. O'Hallaron, and Julio López. The Etree Library: A System for Manipulating Large Octrees on Disk. Technical Report CMU-CS-03-174, School of Computer Science, Carnegie Mellon University, July, 2003. (bib, pdf)

Tiankai Tu, David O'Hallaron and Julio López, Etree -- a database-oriented method for generating large octree meshes. In proceedings of the 11th International Meshing Roundtable (IMR-11), Ithaca, NY, Sept. 2002, pp. 127-138. (bib, ps, pdf)

Julio López and David O'Hallaron, Evaluation of a resource selection mechanism for complex network services, In proceedings of the 10th symposium on High Performance Distributed Computing (HPDC-10), August 2001. San Francisco, CA, USA. (abstract, bib, ps, pdf)

Puneet Sharma, Sung-Ju Lee, Jack Brassil and Julio López, Dynamic Link Striping: Breaking the WAN Bandwidth Barrier in Piconets, In proceedings of the 11th IEEE workshop on Local and Metropolitan Area Networks (LANMAN'2001), March 2001, Boulder, CO, USA. (abstract, bib)

Julio López and David O'Hallaron, Support for interactive heavyweight services, Technical Report CMU-CS-01-104, School of Computer Science, Carnegie Mellon University, February, 2001. (abstract, bib, ps, pdf)

Julio López and David O'Hallaron, Run-time support for adaptive heavyweight services, In Proceedings of the 5th Workshop on Languages, Compilers and Run-time systems (LCR 2000), May 2000, Vol 1915 of Springer Verlag Lecture Notes in Computer Science, Rochester, NY. pp. 221-234. (abstract, bib, ps, pdf)

Julio López and Edward Hogan, Jiffy: A Lightweight Jini File System, In Proceedings of 2nd CMU Student Symposium on Computer Systems (SOCS-2), Oct 1999, Pittsburgh, PA. (bib, pdf)

Julio López, Martin Aeschlimann, Peter Dinda, Bruce Lowekamp, Loukas Kallivokas, and David O'Hallaron, Preliminary Report on the Design of a Framework for Distributed Visualization, Proceedings of the International Conference on Parallel and Distributed Processing Techniques and Applications (PDPTA'99), June 1999, Las Vegas, NV. pp. 1833-1839. (abstract, bib, ps, pdf)

Rabih Zbib, Saadeddine Mneimneh, Julio López, V. Judson Harward, and Richard Rabbat, The TRIERARCH Trigger Architecture, In Proceedings of the Third Annual Federated Laboratory Symposium on Advanced Telecommunications / Information Distribution Research Program, February 1999, College Park, MD. pp. 267-271. (bib)

Judson Harward, Julio López, Saadeddine Mneimneh, Richard Rabbat, Rabih Zbib, An improved Hierarchical Caching Architecture for Low Bandwidth Networks . In ARL Federated Laboratory Symposium. 1998, College Park, Maryland, USA. (bib)


Carnegie Mellon University, Pittsburgh, PA

Universidad EAFIT, Medellín, Colombia.

Honors and Achievements

Along with the members of the Quake project, Winner 2003 Gordon Bell Award for Special Achievement. . The milestone calculations for the award included:

My undergrad university grants every semester a scholarship to the student with the best GPA for that semester. I won 2 of those Scholarships in 1991 and 1992.

First place in the Mathematics Contest for High School Students organized by Universidad EAFIT in 1990.

Finalist in the 4th National Mathematics Contest in 1989.

Third place in the 2nd and 3rd State-wide Mathematics Contest in 1985 and 1987.

Professional affiliations


Proficient English.
Native Spanish.