UPC-CHECK: A scalable tool for detecting run-time errors in Unified Parallel C

Unied Parallel C (UPC) is a language used to write parallel programs for shared and distributed memory parallel computers. UPC-CHECK is a scalable tool developed to automatically detect argument errors in UPC functions and deadlocks in UPC programs at run-time and issue high quality error messages to help programmers quickly x those errors. The tool is easy to use and involves merely replacing the compiler command with upc-check. The tool uses a novel distributed algorithm for detecting argument and deadlock errors in collective operations. The run-time complexity of the algorithm has been proven to be O(1). The algorithm has been extended to detect deadlocks created involving locks with a run-time complexity of O(T), where T is the number of threads waiting to acquire a lock. Error messages issued by UPC-CHECK were evaluated using the UPC RTED test suite for argument errors in UPC functions and deadlocks. Results of these tests show that the error messages issued by UPC-CHECK for these tests are excellent. The scalability of all the algorithms used was demonstrated using performance-evaluation test programs and the UPC NAS Parallel Benchmarks

Precipitate growth features in the duplex size Gamma Prime distribution in the superalloy IN738LC

IN738LC is a modern, nickel base superalloy utilized at high temperatures in aggressive environments. Durability of this superalloy is dependent on the retention of strengthening by Gamma Prime precipitates. The precipitate growth features in the duplex size (fine and coarse) precipitate distribution was studied by heating the alloy for various times in vacuum at selected temperatures in the range 800 °C to 1100 °C. Increasing the holding times from 1 hour to 100 hours shows joining of the fine particles to form bigger particles, leading to distinct raft patterns. Two different Gamma Prime precipitate growth processes had been observed: merging of smaller precipitates to produce larger ones (in duplex precipitate-size microstructures) that is, both the fine and the coarse precipitate particles grow with time, apparently by the particle movement in the matrix and coalescence – by the particle agglomeration mechanism (PAM), and growth through solute absorption from the matrix (Ostwald Ripening). At 1100 °C the fine particles grew to the size of the coarse particles in about 100 hours and a single coarse size of about 840 nm was obtained. The activation energies for the growth of both the fine and coarse particles decrease with increase in temperature and size of the particles indicating that the coarser particles require less activation energy for the growth than the finer particles. This is attributed to the greater attractive force with which the coarser particles would attract the finer particles, in the overlapping diffusion zone thus requiring less activation energy for the growth. The activation energy for the precipitate growth in the duplex size range also was found to decrease progressively with increasing particle size at a given high temperature