Saturday , June 19 2021

The diffusion of the astrophysics code works in the rapid modeling of stellar collisions



Credit: Sagiv Shiber, LSU

“Octo-Tiger,” an advanced astrophysics code, simulates the evolution of autonomous gravitational and rotary systems of arbitrary geometry by optimizing the adaptive network and a new method of blade balance to achieve ultra-fast speeds.

This new code for modeling star collisions is faster than the code used for numerical simulations. The research arose from a unique collaboration between experimental computer scientists and astrophysicists from the LSU Department of Physics and Astronomy, LSU Center for Computing and Technology, Indiana Kokomo University and Macquarie University, Australia, and culminated in more than a year. of tests. simulations, supported by several NSF grants, including one specifically designed to break down the barrier between computer science and astrophysics.

“Thanks to our collaborative efforts, we now have a reliable algorithmic framework for simulating stellar mergers,” said Patrick Motel, a professor of physics at Indiana Kokomo University. “By significantly reducing the computation time to complete the simulation, we can start asking new questions that could not be addressed when the single fusion simulation was too expensive and time consuming. We could explore more spatial parameters, examine simulations with very high spatial accuracy or for longer periods after binding, we can extend the simulations to more complete physical models by integrating radiative transport, for example. ”

This film shows an Octo-Tiger simulation of two people white dwarf The stars are orbiting each other. We observe the two stars as they begin to fuse. Color indicates the density of a gas in orbit or in the middle of the plane, with a brown gas indicating denser and blue less dense. The arrows indicate the speed of the gas. The red arrows correspond to speeds of up to 1,000 km / h and the blue arrows correspond to speeds of up to 1 km / s. The time in seconds is shown at the top left. The binary system initially completes an orbit every two minutes and the total simulation time is less than two hours, which are the last hours of life of this binary before merging. Credit: Sagiv Shiber, LSU

Recently published in the Royal Astronomical Society’s monthly notifications, “Octo-Tiger: New 3D Hydrodynamic Code for Stellar Fergers Using HPX Parallelization” investigates code performance and accuracy with a benchmark test. Authors Mr. Dominic C. Marcelo is a postdoctoral researcher. Sajiv Scheiber, postdoctoral researcher, professor of Dr. Johann Frank; Geoffrey C. Clayton, professor; Dr. .. Dr. .. Patrick Dell, researcher; And Dr. Hartmut Kaiser, a researcher at Louisiana State University, along with collaborators of Dr. Ursula de Marco, a professor at Macquarie University, and Dr. Patrick M. Motell, a professor at Indiana University Cocomo, compares his results with analytical solutions, then, when I know it, and other network-based codes, like the famous FLASH. In addition, they calculated the interaction of two white dwarfs from the first mass transfer to incorporation and compared the results with previous simulations of similar systems.

“A test of Australia’s fastest supercomputer, Gadi (ranked 25th in the top 500 in the world), showed that the Octo-Tiger, which has more than 80,000 cores, has good performance for large models of built-in stars, ”Marco said. “With Octo-Tiger, not only can we drastically reduce waiting times, but our models can answer the many questions that interest us.”

Octo-Tiger is currently optimized to simulate well-resolved stellar fusion, which can be approximated by barotropic structures such as white dwarfs or main-sequence stars. The gravitational solver maintains the angular momentum of the accuracy of the instrument, thanks to the correction algorithm. This code uses HPX parallelism, which allows it to overlap between companies and communications and result in excellent scale properties to solve large problems in shorter time intervals.

“This paper demonstrates how a task-based asynchronous execution system can be used as a viable alternative to a messaging interface to support a major astrophysics problem,” Diehl said.

The research identifies current and planned areas of development that address various physical phenomena associated with transient observations.

“While our special interest in research focuses on stellar fusions and their consequences, there are several problems in computational astrophysics that Octo-Tiger can address through its central infrastructure of autogravitational fluids,” he said. dir Motl.

The following animation was prepared by Shiber, who said, “Octo-Tiger shows extraordinary performance in both Health From solutions and scaling to tens of thousands of cores. These results illustrate Octo-Tiger as an ideal code to model mass transfer in binary systems and to simulate stellar fusions. “

Reference: “Octo-Tiger: A New 3D Hydrodynamic Code for Star Fusions Using HPX Parallelism” Dominic C. Marcello, Sajif Scheiber, Marco Ursula, Johann Frank, Geoffrey C. Clayton, Patrick M Motel, Patrick Dell and Hartmut Kaiser, April 10, 2021, Monthly notifications from the Royal Astronomical Society.
DOI: 10.1093 / mnras / stab937




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