Comparative Performance Analysis of Coarse Solvers for Algebraic Multigrid on Multicore and Manycore Architectures

We study the performance of a two-level algebraic-multigrid algorithm, with a focus on the impact of the coarse-grid solver on performance. We consider two algorithms for solving the coarse-space systems: the preconditioned conjugate gradient method and a new robust HSS-embedded low-rank sparse-factorization algorithm. Our test data comes from the SPE Comparative Solution Project for oil-reservoir simulations. We contrast the performance of our code on one 12-core socket of a Cray XC30 machine with performance on a 60-core Intel Xeon Phi coprocessor. To obtain top performance, we optimized the code to take full advantage of fine-grained parallelism and made it thread-friendly for high thread count. We also developed a bounds-and-bottlenecks performance model of the solver which we used to guide us through the optimization effort, and also carried out performance tuning in the solver’s large parameter space. As a result, significant speedups were obtained on both machines

GENDER DIMENSION OF THE BULGARIA'S NEW MIGRATION: POLICY IMPLICATIONS

The article presents the main findings of the basic paper contributors at the workshop under the above title. The aim was to increase gender awareness and open channels of discussion on the new migration from Bulgaria by gender. The authors have delivered papers on gender dimension issues of the emigration process in Bulgaria since 1989 onwards and have discussed them with representatives of the official (executive) institutions and relevant NGOs. Data from the National Statistical Institute, in particular the last Population Census (2001) and a sample survey in 2003 are used to shed light on patterns of people's mobility in gender perspective in the last 15 years and in the years to come - by age, reason for migration, education, ethnic group, geographical destination of the Bulgarian migrants, etc. Gender aspects of external migration statistics, labour market performance and policy and social consequences are considered. In conclusion implications are given in two aspects: concerning improvement of migration statistics by gender and concerning building an adequate national policy towards the ongoing migration processes, in particular in view of the soon integration of Bulgaria into the EU.