the <a href="functions-reduce.html#functions-partial-sum">partial sum function</a>.</li>
<li><em><code>x</code></em>: array of <code>T</code>, one for each term of the reduction, <code>T</code> can be any type,</li>
<li><em><code>grainsize</code></em>: For <code>reduce_sum</code>, <code>grainsize</code> is the recommended size of the partial sum (<code>grainsize = 1</code> means pick totally automatically). For <code>reduce_sum_static</code>, <code>grainsize</code> determines the maximum size of the partial