Preconditioned iterative sparse linear solvers are memory-efficient for large scientific simulations, but the dependences between iterations introduced by preconditioners limit parallelization. This issue is exacerbated on GPUs, which feature many parallel cores. We propose a sparsified preconditioned conjugate gradient (SPCG) solver that increases parallelism by reducing dependences through sparsification, while preserving convergence behavior. We evaluate the proposed SPCG using both ILU(0) and ILU(K) preconditioners on a wide range of symmetric positive definite (SPD) matrices. The proposed SPCG improves the performance of the iterative phase of SPCG by a geometric mean speedup of 1.23 × and 1.65 × over the non-sparsified PCG using ILU(0) and ILU(K), respectively on an NVIDIA A100 GPU. SPCG also yields geometric mean end-to-end speedups of 1.68 × and 3.73 × over the non-sparsified versions with ILU(0) and ILU(K), respectively, on the same platform.

An important sparse tensor computation is sparse-tensor-dense-matrix multiplication (SpTM), which is used in tensor decomposition and applications. SpTM is a multi-dimensional analog to sparse-matrix-dense-matrix multiplication (SpMM). In this article, we employ a hierarchical tensor data layout that can unfold a multidimensional tensor to derive a 2D matrix, making it possible to compute SpTM using SpMM kernel implementations for GPUs. We compare two SpMM implementations to the state-of-the-art PASTA sparse tensor contraction implementation using: (1) SpMM with hierarchical tensor data layout; and, (2) unfolding followed by an invocation of cuSPARSE’s SpMM. Results show that SpMM can outperform PASTA 70.9% of the time, but none of the three approaches is best overall. Therefore, we use a decision tree classifier to identify the best performing sparse tensor contraction kernel based on precomputed properties of the sparse tensor.

We optimize Sparse Matrix Vector multiplication (SpMV) using a mixed precision strategy (MpSpMV) for Nvidia V100 GPUs. The approach has three benefits: (1) It reduces computation time, (2) it reduces the size of the input matrix and therefore reduces data movement, and (3) it provides an opportunity for increased parallelism. MpSpMV’s decision to lower to single precision is data driven , based on individual nonzero values of the sparse matrix. On all real-valued matrices from the Sparse Matrix Collection, we obtain a maximum speedup of 2.61× and average speedup of 1.06× over double precision, while maintaining higher accuracy compared to single precision.