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7 Chunking is controlled by a *partitioner* and a *grainsize.*\  To gain
16    argument form of the constructor is
18    ``grainsize`` is 1. It is in units of loop iterations per chunk.
25 The following code is the last example from parallel_for, modified to
48 There is also an intermediate level of control where you specify the
50 ``affinity_partitioner``. An ``auto_partitioner`` is the default
62 Because of the impact of grainsize on parallel loops, it is worth
92 A rule of thumb is that ``grainsize`` iterations of ``operator()``
99    is specified in units of loop iterations. If you have no idea of how
101    ``grainsize``\ =100,000. The rationale is that each iteration
113 A drawback of setting a grainsize too high is that it can reduce
114 parallelism. For example, if the grainsize is 1000 and the loop has 2000
119 parallel performance if there is other parallelism available higher up
129 computation over a million indices. There is little work per iteration.
142 The scale is logarithmic. The downward slope on the left side indicates
143 that with a grainsize of one, most of the overhead is parallel
154    A general rule of thumb for parallelizing loop nests is to
155    parallelize the outermost one possible. The reason is that each
156    iteration of an outer loop is likely to provide a bigger grain of