  Among the (uncontended) common wisdom in High-Performance Computing (HPC) is
the applications' need for large amount of double-precision support in
hardware. Hardware manufacturers, the TOP500 list, and (rarely revisited)
legacy software have without doubt followed and contributed to this view.
  In this paper, we challenge that wisdom, and we do so by exhaustively
comparing a large number of HPC proxy application on two processors: Intel's
Knights Landing (KNL) and Knights Mill (KNM). Although similar, the KNM and KNL
architecturally deviate at one important point: the silicon area devoted to
double-precision arithmetic's. This fortunate discrepancy allows us to
empirically quantify the performance impact in reducing the amount of hardware
double-precision arithmetic.
  Our analysis shows that this common wisdom might not always be right. We find
that the investigated HPC proxy applications do allow for a (significant)
reduction in double-precision with little-to-no performance implications. With
the advent of a failing of Moore's law, our results partially reinforce the
view taken by modern industry (e.g. upcoming Fujitsu ARM64FX) to integrate
hybrid-precision hardware units.
