Module nl_writer 

Minimal AMPL .sol-format writer.

Format reference: David M. Gay, “Hooking Your Solver to AMPL” (https://ampl.com/REFS/hooking2.pdf) §5 (“Returning Results to AMPL”), cross-checked against the AMPL solver-library reference implementation write_sol_ASL in https://github.com/ampl/asl (solvers/writesol.c). We emit the ASCII variant — the same one AMPL’s commands file produces by default when reading back from solvers.

Format

<message line 1>
<message line 2>
...                         (free text, ended by a blank line then "Options")

Options
<nopts>                     (int — number of integer option-words to follow)
<opt0>                      (... nopts lines)
...
<n_dual>                    (number of dual values written below)
<m>                         (constraint count)
<n_primal>                  (number of primal values written below)
<n>                         (variable count)
<lambda[0]>                 (... n_dual lines, dual values)
...
<x[0]>                      (... n_primal lines, primal values)
...
objno <objno> <status>      (optional — selects which objective and the solver-return code)
suffix <kind> <nvalues> <namelen> <tablen> <tabline>  (optional — one block per exported suffix)
<name>                      (the suffix name, on its own line)
<idx> <value>
...

The four-integer count block is the canonical AMPL form: each dimension count is paired with a “values written” partner so the reader knows how many dual and primal lines to consume before reaching objno. We always write every dual and primal, so n_dual == m and n_primal == n. (Earlier pounce builds emitted only the two bare counts <m>\n<n>\n; AMPL’s own reader and Pyomo’s .sol reader both reject that short form.)

Scope

Smallest writer that lets crate::nl_reader::NlSuffixes flow from a pounce solve back through AMPL’s reader. Specifically the pounce_sens binary (pounce#17) writes:

• The nominal primal and dual blocks (so AMPL sees x* and λ* on the regular _var.X / _con.dual slots).
• One or more sensitivity suffixes (sens_sol_state_<N>) carrying the perturbed primal as a real-var suffix, matching upstream MetadataMeasurement::SetSolution (ref/Ipopt/contrib/sIPOPT/src/SensMetadataMeasurement.cpp:128-150).

Structs

SolSuffix

A single suffix block to write back into the .sol file. Mirrors the S-segment shape of crate::nl_reader::NlSuffixes entries.

SolutionFile

Solution payload bundled for a .sol write.

Enums

SolSuffixTarget

SolSuffixValues

Functions

format_sol

Format payload into AMPL .sol ASCII text.

write_sol_file

Convenience: write payload to path (truncating any existing file). Returns the bytes written on success.