  The sparse representation of graphs has shown great potential for
accelerating the computation of graph applications (e.g., Social Networks,
Knowledge Graphs) on traditional computing architectures (CPU, GPU, or TPU).
But the exploration of large-scale sparse graph computing on
processing-in-memory (PIM) platforms (typically with memristive crossbars) is
still in its infancy. To implement the computation or storage of large-scale or
batch graphs on memristive crossbars, a natural assumption is that a
large-scale crossbar is demanded, but with low utilization. Some recent works
question this assumption, to avoid the waste of storage and computational
resource, the fixed-size or progressively scheduled ''block partition'' schemes
are proposed. However, these methods are coarse-grained or static, and are not
effectively sparsity-aware. This work proposes the dynamic sparsity-aware
mapping scheme generating method that models the problem with a sequential
decision-making model, and optimizes it by reinforcement learning (RL)
algorithm (REINFORCE). Our generating model (LSTM, combined with the
dynamic-fill scheme) generates remarkable mapping performance on a small-scale
graph/matrix data (complete mapping costs 43% area of the original matrix) and
two large-scale matrix data (costing 22.5% area on qh882 and 17.1% area on
qh1484). Our method may be extended to sparse graph computing on other PIM
architectures, not limited to the memristive device-based platforms.
