Engineering topics

Warren, M. S.

Publications and source records attributed to Warren, M. S..

3 records

DOE OSTI2018

Consequences of Giant Impacts on Early Uranus for Rotation, Internal Structure, Debris, and Atmospheric Erosion

Here, we perform a suite of smoothed particle hydrodynamics simulations to investigate in detail the results of a giant impact on the young Uranus. We study the internal structure, rotation rate, and atmospheric retention of the post-impact planet, as well as the composition of material ejected into orbit. Most of the material from the impactor's rocky core falls in to the core of the target. However, for higher angular momentum impacts, significant amounts become embedded anisotropically as lumps in the ice layer. Furthermore, most of the impactor's ice and energy is deposited in a hot, high-entropy shell at a radius of ~3 R ⊕ . This could explain Uranus' observed lack of heat flow from the interior and be relevant for understanding its asymmetric magnetic field. We verify the results from the single previous study of lower resolution simulations that an impactor with a mass of at least 2 M ⊕ can produce sufficiently rapid rotation in the post-impact Uranus for a range of angular momenta. At least 90% of the atmosphere remains bound to the final planet after the collision, but over half can be ejected beyond the Roche radius by a 2 or 3 M ⊕ impactor. This atmospheric erosion peaks for intermediate impactor angular momenta (~3 × 10 36 kg m 2 s –1 ). Rock is more efficiently placed into orbit and made available for satellite formation by 2 M ⊕ impactors than 3 M ⊕ ones, because it requires tidal disruption that is suppressed by the more massive impactors.

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS1997

Pentium Pro inside: A treecode at 430 Gigaflops on ASCI Red - 1

As an entry for the 1997 Gordon Bell performance prize, we present results from two methods of solving the gravitational N-body problem on the Intel Teraflops system at Sandia National Laboratory (ASCI Red). The first method, an O(N2) algorithm, obtained 635 Gigaflops for a 1 million particle problem on 6800 Pentium Pro processors. The second solution method, a tree-code which scales as O(N log N), sustained 170 Gigaflops over a continuous 9.4 hour period on 4096 processors, integrating the motion of 322 million mutually interacting particles in a cosmology simulation, while saving over 100 Gigabytes of raw data. Additionally, the tree-code sustained 430 Gigaflops on 6800 processors for the first 5 time-steps of that simulation. This tree-code solution is approximately 105 times more efficient than the O(N2) algorithm for this problem. As an entry for the 1997 Gordon Bell price/performance prize, we present two calculations from the disciplines of astrophysics and fluid dynamics. The simulations were performed on two 16 Pentium Pro processor Beowulf-class computers (Loki and Hyglac) constructed entirely from commodity personal computer technology, at a cost of roughly $50k each in September, 1996. The price of an equivalent system in August 1997 is less than $30. At Los Alamos, Loki performed a gravitational tree-code N-body simulation of galaxy formation using 9.75 million particles, which sustained an average of 879 Mflops over a ten day period, and produced roughly 10 Gbytes of raw data.

Warren, M. S.↗

NASA NTRS1997

Parallel supercomputing with commodity components

We have implemented a parallel computer architecture based entirely upon commodity personal computer components. Using 16 Intel Pentium Pro microprocessors and switched fast ethernet as a communication fabric, we have obtained sustained performance on scientific applications in excess of one Gigaflop. During one production astrophysics treecode simulation, we performed 1.2 x 10(sup 15) floating point operations (1.2 Petaflops) over a three week period, with one phase of that simulation running continuously for two weeks without interruption. We report on a variety of disk, memory and network benchmarks. We also present results from the NAS parallel benchmark suite, which indicate that this architecture is competitive with current commercial architectures. In addition, we describe some software written to support efficient message passing, as well as a Linux device driver interface to the Pentium hardware performance monitoring registers.

Performance↗