FIG. 2.

Structure of the distributed driver: see the final paragraph in Sec. IV for details. In brief, a user request (a) for a multi-molecule, multi-model-chemistry, or non-analytic derivative passes into planning functions (b) defined in procedure tiles (z) that generate a pool of QCSCHEMA for single-molecule, single-model-chemistry, analytic derivative inputs. These can run in several modes (c), depending on desired parallelism and recoverability. Completed QCSCHEMA passes through assembly functions (d) defined in procedure tiles (z) and denoted “ASM” that reconstitute (e) into the requested energy (“E”), gradient (“G”), or Hessian (“H”).