  We used a one-zone chemical evolution model to address the question of how
many masses and metallicities are required in grids of massive stellar models
in order to ensure reliable galactic chemical evolution predictions. We used a
set of yields that includes seven masses between 13 and 30 Msun, 15
metallicities between 0 and 0.03 in mass fraction, and two different remnant
mass prescriptions. We ran several simulations where we sampled subsets of
stellar models to explore the impact of different grid resolutions. Stellar
yields from low- and intermediate-mass stars and from Type Ia supernovae have
been included in our simulations, but with a fixed grid resolution. We compared
our results with the stellar abundances observed in the Milky Way for O, Na,
Mg, Si, Ca, Ti, and Mn. Our results suggest that the range of metallicity
considered is more important than the number of metallicities within that
range, which only affects our numerical predictions by about 0.1 dex. We found
that our predictions at [Fe/H] < -2 are very sensitive to the metallicity range
and the mass sampling used for the lowest metallicity included in the set of
yields. Variations between results can be as high as 0.8 dex, for any remnant
mass prescription. At higher [Fe/H], we found that the required number of
masses depends on the element of interest and on the remnant mass prescription.
With a monotonic remnant mass prescription where every model explodes as a
core-collapse supernova, the mass resolution induces variations of 0.2 dex on
average. But with a remnant mass prescription that includes islands of
non-explodability, the mass resolution can cause variations of about 0.2 to 0.7
dex depending on the choice of metallicity range. With such a prescription,
explosive or non-explosive models can be missed if not enough masses are
selected, resulting in over- or under-estimations of the mass ejected by
massive stars.

Astrophysics of Galaxies