opm-adjoint

Adjoint-based gradients for the OPM flow simulator, developed as a downstream module against unmodified opm-simulators master (the opm-flowgeomechanics extension pattern): the recording hooks live in a derived AdjointFlowProblem (virtual beginEpisode/endTimeStep), the well-state normalization in a derived AdjointWellModel, and the backward replay driver only uses public simulator APIs.

Single binary flow_adjoint:

# forward run with per-substep recording
flow_adjoint CASE.DATA --adjoint-save=true --adjoint-save-system=true \
    --enable-storage-cache=false --threads-per-process=1
# backward replay + verification against the stored systems
flow_adjoint CASE.DATA --adjoint-mode=replay \
    --enable-storage-cache=false --threads-per-process=1

Design and testing documentation: adjoint_plan.md and adjoint_testing.md in the parent working tree (to be moved here).