PIXIE

PIXIE es un solver compacto de programacion lineal y entera mixta (LP/MILP), implementado en un solo archivo ISO C17 (pixie.c).

Soporta:

• Lectura de modelos en formato LP y MPS.
• Simplex primal de dos fases.
• Branch-and-bound determinista para variables enteras y binarias.

Requisitos

• Compilador C con soporte C17 (GCC, Clang o compatible).

Compilacion

Linux/macOS:

gcc -O3 -std=c17 -Wall -Wextra -pedantic pixie.c -o pixie

Windows (MinGW-w64):

gcc -O3 -std=c17 -Wall -Wextra -pedantic pixie.c -o pixie.exe

Modos de uso

1. Modo automatico (detecta LP/MPS por extension y contenido):

./pixie modelo.mps
./pixie modelo.lp

2. Modo LP forzado:

./pixie --lp modelo.lp

3. Modo MPS forzado:

./pixie --mps modelo.mps

4. Modo relajacion LP (sin branch-and-bound):

./pixie --mps modelo.mps --purelp

5. Modo auto-prueba interna:

./pixie --selftest

Opciones de linea de comandos

• --time <sec>: limite de tiempo en segundos.
• --node <n>: limite de nodos en branch-and-bound.
• --gap <g>: limite de gap relativo MIP.
• --seed <s>: semilla RNG para desempates aleatorizados.
• --verbose <k>: verbosidad de 0 a 3.
• --purelp: resuelve solo la relajacion LP.
• --selftest: ejecuta pruebas embebidas y termina.

Ejemplos

Windows (PowerShell):

.\pixie.exe --mps netlib-main/feasible/25fv47.mps
.\pixie.exe --mps netlib-main/feasible/woodw.mps --time 60 --verbose 1

Linux/macOS:

./pixie --lp examples/modelo.lp --node 10000 --gap 1e-4

Formato de salida

PIXIE imprime resultados en formato texto simple:

• s OPTIMUM FOUND + o <valor_objetivo> + v <x1> <x2> ...
• s INFEASIBLE
• s UNBOUNDED
• s UNKNOWN (opcionalmente con o <valor> si existe primal)

Licencia

MIT License

Copyright (c) 2026 Oscar Riveros

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.