A parallel lagrangian heuristic for the fractional chromatic number of a graph Paulo Henrique Macêdo de Araújo, Ricardo C. Corrêa and Manoel Campêlo RAIRO-Oper. Res., 57 4 (2023) 1821-1841 Published online: 14 July 2023 DOI: 10.1051/ro/2023062