FICO
FICO Xpress Optimization Examples Repository
FICO Optimization Community FICO Xpress Optimization Home
Back to examples browserPrevious exampleNext example

Query Attributes of Xpress

Description

Query Attributes of Xpress



Further explanation of this example: Xpress R Reference Manual

query_attributes_R.zip[download all files]

Source Files
By clicking on a file name, a preview is opened at the bottom of this page.
query_attributes.R[download]

Data Files





query_attributes.R

#####################################
# This file is part of the          #
# Xpress-R interface examples       #
#                                   #
#   (c) 2021 Fair Isaac Corporation #
#####################################
#' ---
#' title: "Query Attributes"
#' author: Gregor Hendel
#' date: Dec. 2020
#' ---
#'

#'
#' This example shows how to query attributes of the FICO Xpress Optimizer. A list
#' of all public attributes can be found in the [Attributes
#' Reference](reference_attributes.html).
#'
#' One important thing first: You can access all controls and attributes with a
#' special syntax in R: Use `xpress:::ROWS` (yes, 3 colons) to access the integer
#' ID of the rows attribute of the optimizer. We provide the integer IDs for
#' controls and attributes in this way such that they do not pollute the namespace
#' upon loading the `xpress` package.
#'
#'
#' If you haven't done so already, please familiarize yourself with the Facility
#' Location Example, which we use throughout our quick examples.
#'
#' We read the Facility location problem from the introductory example, and print
#' it to verify its dimensions.
#'
## ----Reading in the Facility Location Problem---------------------------------
suppressMessages(library(xpress))
p <- createprob()
print(readprob(p, "flp.lp"))

#'
#' # Query Basic Problem Attributes
#'
#' Attributes can be accessed via the functions `getintattrib`, `getdblattrib`, and
#' `getstringattrib` from the xpress-package. All three functions receive an
#' integer ID as input.
#'
#' When we use the print()-function on our XPRSprob object, R internally calls
#' `print.XPRSprob` from the package. This functions uses the attribute querying
#' mechanism to inspect the currently loaded optimization problem.
#'
#' Let's have a look.
## ----Inspecting the Print Function of XPRSprob--------------------------------
print(xpress:::print.XPRSprob)

#'
#' # Query Attributes After a Solve
#'
#' Many attributes are only meaningful after the problem was solved, for example
#' search tree and solution information, or solving time. Let's optimize the loaded
#' facility location problem and print such information.
#'
## ----Query Attributes after The Solve-----------------------------------------
xprs_optimize(p)

# query some attributes
print(paste("Number of solutions: ", getintattrib(p, xpress:::MIPSOLS)))
print(paste("Number of B%B nodes: ", getintattrib(p, xpress:::NODES)))
print(paste("Solving Time: ", getintattrib(p, xpress:::TIME)))


Back to examples browserPrevious exampleNext example