1. A system for transforming sparse elements into a dense matrix, the system comprising: multiple sparse element access units arranged along respective dimensions of a two-dimensional sparse-dense transform unit, wherein each sparse element access unit includes: a respective data fetch unit comprising a respective plurality of processors, the data fetch unit configured to: receive, from an external source, one or more control signals that provide an indication that the sparse element access unit in which the data fetch unit is located is assigned to access a subset of particular sparse elements that are stored in one or more data shards; and fetch, based on the indication, one or more sparse elements of the subset of the particular sparse elements; and a respective concatenation unit configured to: generate an output dense matrix based on a transformation that is applied to at least the one or more sparse elements.