A description of share

This directory collects code shared between various models in a CIME-coupled
system.

Motivation for this code sharing includes:

- facilitating consistent physics between all models.  For example, uniform
  solar-zenith-angle/orbital calculations and uniform physical constants.
- avoiding the need for redundant implementations of commonly needed
  functionality.  For example netCDF file reading, basic mapping (re-gridding)
  functionality, and common character string manipulations.

While a runtime library is made from this code, some of this shared code is accessed
by including the appropriate source code directory path during compile time.

Current subsets of shared code include:

util - very generic, general-purpose Fortran code that is likely to be useful to all
      CIME components.  CIME components may be explicitly required to use some
      parts of this code, for example the physical constants module.

RandNum - various software random number generators

esmf_wrf_timemgr - Fortran implementation of ESMF Time Manager (5.2.0rp1)

timing - custom version of the GPTL.

streams - code for managing "streams" of data files.

test - unit tests for some of the share code


This code was originaly part of CIME in CIME/src/share. Brought in to E3SM
from CIME hash b95a28b417b9b27 from May 4, 2021