Expand description
§oximo-io
Model I/O for oximo: MPS, LP, and NLP writers.
Converts an oximo oximo_core::Model to standard text formats for exchanging models with external solvers and tools.
§Usage
Enabled by default via the io feature on the umbrella oximo crate:
[dependencies]
oximo = "0.1" # io is on by defaultTo opt out:
[dependencies]
oximo = { version = "0.1", default-features = false, features = ["highs"] }To use this crate directly:
[dependencies]
oximo-io = "0.1"
oximo-core = "0.1"§Quick example
ⓘ
use oximo::prelude::*;
use oximo::io::{to_mps_string, to_lp_string};
let m = Model::new("knapsack");
let x = m.var("x").lb(0.0).build();
let y = m.var("y").lb(0.0).ub(4.0).build();
m.constraint("c1", (x + 2.0 * y).le(14.0));
m.constraint("c2", (3.0 * x - y).ge(0.0));
m.maximize(3.0 * x + 4.0 * y);
let mps = to_mps_string(&m)?;
let lp = to_lp_string(&m)?;
println!("{mps}");§Formats
§MPS
Fixed-format MPS (fixed-column, 10-char field width). Widely supported by commercial and open-source solvers.
| Feature | Behavior |
|---|---|
| Objective row | Named OBJ, maximization models are negated with a * sense: maximize comment so re-importers can recover the original sense |
| Integer variables | Wrapped in INTORG/INTEND markers |
| Bounds | FR (free), MI+UP (lower=-inf), LO/UP as needed. Default lb=0 omitted |
| Constant terms | Objective constant written to RHS OBJ, constraint constants folded into RHS |
ⓘ
use oximo_io::{write_mps, to_mps_string};
use std::fs::File;
use std::io::BufWriter;
// To string
let s = to_mps_string(&model)?;
// To file
let mut f = BufWriter::new(File::create("model.mps")?);
write_mps(&model, &mut f)?;§LP (CPLEX LP format)
Human-readable CPLEX LP format. Sections emitted: header comment, Minimize/Maximize, Subject To, Bounds (non-default only), General, Binaries, End.
| Feature | Behavior |
|---|---|
| Objective sense | Minimize / Maximize keyword, no negation needed |
| Integer variables | General section (integer/semi-integer), Binaries section |
| Bounds | Free variables declared with free; default lb=0, ub=+inf omitted |
| Objective constant | Written as a comment if non-zero |
ⓘ
use oximo_io::{write_lp, to_lp_string};
use std::fs::File;
use std::io::BufWriter;
// To string
let s = to_lp_string(&model)?;
// To file
let mut f = BufWriter::new(File::create("model.lp")?);
write_lp(&model, &mut f)?;§NL
The standard format for sharing nonlinear and mixed-integer models. Unlike MPS/LP, it carries full nonlinear expressions, emitted as prefix (Polish) opcode trees.
| Feature | Behavior |
|---|---|
| Nonlinear bodies | Linear part goes to J/G; nonlinear residual to C/O opcode trees |
| Supported operators | + - * /, negation, pow, abs, sin, cos, exp, log (natural) |
| Output encoding | ASCII (default) or binary, via WriteOptions::format |
| Precision / comments | precision and comments knobs tune the ASCII output |
| Variable ordering | Standard ASL order: nonlinear-first (by appearance), then linear |
| Name sidecars | write_nl_files also writes .row / .col name files |
| Optional segments | F/S/V/d/r segments supplied via WriteOptions |
ⓘ
use oximo::prelude::*;
use oximo::io::{to_nl_string, write_nl_with, write_nl_files, WriteOptions};
use std::fs::File;
use std::io::BufWriter;
use std::path::Path;
// Rosenbrock: min (1 - x)^2 + 100 (y - x^2)^2
let m = Model::new("rosen");
let x = m.var("x").bounds(-5.0, 5.0).build();
let y = m.var("y").bounds(-5.0, 5.0).build();
m.minimize((1.0 - x).powi(2) + 100.0 * (y - x.powi(2)).powi(2));
// To string (ASCII only)
let nl = to_nl_string(&m)?;
// To <stub>.nl plus sibling .row / .col name files
let opts = WriteOptions { aux_files: true, ..Default::default() };
write_nl_files(&m, Path::new("rosen"), &opts)?;
// Binary output needs to be written to a byte sink
let mut f = BufWriter::new(File::create("rosen.nl")?);
write_nl_with(&m, &mut f, &WriteOptions::binary())?;Not yet supported: range constraints, Hollerith (string) constants, and Param nodes.
§Errors
All functions return Result<_, IoError>:
| Variant | Cause |
|---|---|
IoError::NoObjective | Model has no objective set |
IoError::Nonlinear | Nonlinear node in an MPS/LP model (NL supports nonlinear bodies) |
IoError::UnsupportedNode(n) | Node not representable in the target format, e.g. Param in NL |
IoError::InvalidNumber | Non-finite (NaN/Inf) constant while nonfinite_strings is off |
IoError::BinaryToString | to_nl_string used with binary output; use write_nl_with to a byte sink |
IoError::Io(e) | Underlying std::io::Error from the writer |
§License
MIT OR Apache-2.0
Re-exports§
pub use error::IoError;pub use lp::to_lp_string;pub use lp::write_lp;pub use mps::to_mps_string;pub use mps::write_mps;pub use nl::Complementarity;pub use nl::DefinedVar;pub use nl::ImportedFunction;pub use nl::NlFormat;pub use nl::SuffixData;pub use nl::SuffixFlavour;pub use nl::SuffixKind;pub use nl::WriteOptions;pub use nl::to_nl_string;pub use nl::to_nl_string_with;pub use nl::write_nl;pub use nl::write_nl_files;pub use nl::write_nl_with;