Function compile_program_to_spatial_agreeing 

pub fn compile_program_to_spatial_agreeing(
    source: &str,
    target: &SpatialTarget,
    dense: &BTreeSet<String>,
) -> Result<ProgramLowering, SpatialReject>

compile_program_to_spatial for one program of a DEPLOYMENT: dense names the tables the deployment’s other programs lay out as matrices (dense_tables_of), so a table one program writes and another reads is laid out alike in both — the agreement dense_tables makes inside a program, made across the programs that share it.