R/readQP.R

In cafreeman/readQP: Handle Quadratic Programming problems with CPLEX_LP files

# readQP.R

#' @name readModelFile
#' @title Convert model files to ROI-compatible model objects
#' @description Read and parse a CPLEX model file (including quadratic objectives).
#' @param filePath The path to the model file
#' @param type File type. Defaults to "CPLEX_LP"
#' @return An ROI-compatible model object
#' @export
readModelFile <- function(filePath, type = "CPLEX_LP") {
  file <- readCPLEXFile(filePath)
  if (!isQP(file)) {
    message("No quadratic elements detected. Defaulting to Rglpk_read_file.\n")
    return(Rglpk_read_file(filePath, type = type))
  }
  list[model, vecMap] <- processQP(file, type)
  qMat <- createQMatrix(vecMap)
  return(createQPModel(model, qMat))
}

# Insert the Q matrix into the model object's `objective` element. model$objective will now have
# two child elements: c (the original/linear objective) and Q (the quadratic element)
createQPModel <- function(model, qMat) {
  c <- model$objective
  model$objective <- list(c = c, Q = qMat)
  return(model)
}

readCPLEXFile <- function(filePath) {
  if (!isLPFile(filePath)) {
    stop("You must use a CPLEX LP model file (ending in '.lp')")
  }
  file <- readChar(normalizePath(filePath), file.info(filePath)$size)
  return(file)
}