Specify that the SYMPHONY
software (Ralphs & Güzelsoy 2005)  using the Rsymphony package 
should be used to solve a conservation planning problem()
.
This function can also be used to customize the behavior of the solver.
It requires the Rsymphony package to be installed.
add_rsymphony_solver( x, gap = 0.1, time_limit = .Machine$integer.max, first_feasible = FALSE, verbose = TRUE )
x 


gap 

time_limit 

first_feasible 

verbose 

Object (i.e. ConservationProblem
) with the solver
added to it.
SYMPHONY is an opensource mixed integer programming solver that is part of the Computational Infrastructure for Operations Research (COINOR) project. The Rsymphony package provides an interface to COINOR and  unlike dependencies for other solvers  is available on CRAN. For information on the performance of different solvers, please see Schuster et al. (2020) for benchmarks comparing the run time and solution quality of different solvers when applied to different sized datasets.
Ralphs TK and Güzelsoy M (2005) The SYMPHONY callable library for mixed integer programming. In The Next Wave in Computing, Optimization, and Decision Technologies (pp. 6176). Springer, Boston, MA.
Schuster R, Hanson JO, StrimasMackey M, and Bennett JR (2020). Exact integer linear programming solvers outperform simulated annealing for solving conservation planning problems. PeerJ, 8: e9258.
# \dontrun{ # load data data(sim_pu_raster, sim_features) # create problem p < problem(sim_pu_raster, sim_features) %>% add_min_set_objective() %>% add_relative_targets(0.1) %>% add_binary_decisions() %>% add_rsymphony_solver(time_limit = 10, verbose = FALSE) # generate solution s < solve(p) # plot solution plot(s, main = "solution", axes = FALSE, box = FALSE)# }