Gurobi FLK compatibility

mip/gurobi.py

@@ -112,6 +112,10 @@
 
  int GRBloadenv(GRBenv **envP, const char *logfilename);
 
+ int GRBemptyenv (GRBenv **envP);
+
+ int GRBstartenv (GRBenv *env);
+
  int GRBnewmodel(GRBenv *env, GRBmodel **modelP,
  const char *Pname, int numvars,
  double *obj, double *lb, double *ub, char *vtype,
@@ -180,6 +184,8 @@
 
  int GRBsetdblparam(GRBenv *env, const char *paramname, double value);
 
+ int GRBsetstrparam(GRBenv *env, const char *paramname, const char *newvalue);
+
  int GRBsetobjectiven(GRBmodel *model, int index,
  int priority, double weight,
  double abstol, double reltol, const char *name,
@@ -243,10 +249,14 @@
  int GRBdelconstrs (GRBmodel *model, int numdel, int *ind);
 
  int GRBreset (GRBmodel *model, int clearall);
+
+ char * GRBgeterrormsg (GRBenv *env);
  """
  )
 
  GRBloadenv = grblib.GRBloadenv
+ GRBemptyenv = grblib.GRBemptyenv
+ GRBstartenv = grblib.GRBstartenv
  GRBnewmodel = grblib.GRBnewmodel
  GRBfreeenv = grblib.GRBfreeenv
  GRBfreemodel = grblib.GRBfreemodel
@@ -279,6 +289,7 @@
  GRBgetdblattr = grblib.GRBgetdblattr
  GRBsetdblparam = grblib.GRBsetdblparam
  GRBgetdblparam = grblib.GRBgetdblparam
+ GRBsetstrparam = grblib.GRBsetstrparam
  GRBgetstrattrelement = grblib.GRBgetstrattrelement
  GRBcbget = grblib.GRBcbget
  GRBcbsetparam = grblib.GRBcbsetparam
@@ -293,6 +304,7 @@
  GRBsetstrattr = grblib.GRBsetstrattr
  GRBgetdblattrarray = grblib.GRBgetdblattrarray
  GRBreset = grblib.GRBreset
+ GRBgeterrormsg = grblib.GRBgeterrormsg
 
  GRB_CB_MIPSOL = 4
  GRB_CB_MIPNODE = 5
@@ -337,6 +349,11 @@
 
 
 class SolverGurobi(Solver):
+
+ # class dictionary to facilitate setting of Gurobi's Flexible Licensing Key parameters
+ # which are used in the __init__ method.
+ _env_params = {}
+
  def __init__(self, model: Model, name: str, sense: str, modelp: CData = ffi.NULL):
  """modelp should be informed if a model should not be created,
  but only allow access to an existing one"""
@@ -364,12 +381,53 @@ def __init__(self, model: Model, name: str, sense: str, modelp: CData = ffi.NULL
  self._ownsModel = True
  self._env = ffi.new("GRBenv **")
 
- # creating Gurobi environment
- st = GRBloadenv(self._env, "".encode("utf-8"))
- if st != 0:
- raise InterfacingError(
- "Gurobi environment could not be loaded, check your license."
- )
+ if self._env_params:
+ # The following is the only way in which environments relying on FLK licenses
+ # can be created.
+
+ st = GRBemptyenv(self._env)
+ if st != 0:
+ raise InterfacingError(
+ "Could not start (empty) Gurobi environment."
+ )
+
+ def _gurobi_param_error(param_type, key):
+ gurobi_err_msg = ffi.string(GRBgeterrormsg(self._env[0])).decode("utf-8")
+ return ParameterNotAvailable(
+ f"GurobiError: {gurobi_err_msg}.\nCould not set {param_type} parameter: {key}. Check parameter name. Check value type."
+ )
+
+ for key, val in self._env_params.items():
+ if isinstance(val, str):
+ st = GRBsetstrparam(self._env[0], key.encode("utf-8"), val.encode("utf-8"))
+ if st != 0:
+ raise _gurobi_param_error("str", key)
+ elif isinstance(val, int):
+ st = GRBsetintparam(self._env[0], key.encode("utf-8"), val)
+ if st != 0:
+ raise _gurobi_param_error("int", key)
+ elif isinstance(val, float):
+ st = GRBsetintparam(self._env[0], key.encode("utf-8"), val)
+ if st != 0:
+ raise _gurobi_param_error("float", key)
+ else:
+ raise ParameterNotAvailable(
+ f"Unrecognized type ({type(val)}) for parameter value {key}. Supported types: str, int, float."
+ )
+
+ st = GRBstartenv(self._env[0])
+ if st != 0:
+ gurobi_err_msg = ffi.string(GRBgeterrormsg(self._env[0])).decode("utf-8")
+ raise InterfacingError(
+ f"GurobiError: {gurobi_err_msg}.\nGurobi environment could not be started"
+ )
+ else:
+ # creating Gurobi environment
+ st = GRBloadenv(self._env, "".encode("utf-8"))
+ if st != 0:
+ raise InterfacingError(
+ "Gurobi environment could not be loaded, check your license."
+ )
  self._env = self._env[0]
 
  # creating Gurobi model
@@ -1540,6 +1598,15 @@ def var_get_x(self, var: Var):
 
  def __del__(self):
  return
+
+
+def set_env_params(**kwargs):
+ # Gurobi offers a licensing method called FLK (Flexible Licensing Key)
+ # Previously this was known as ISV. This license requires parameters
+ # to be set on an empty Gurobi environment. Gurobi users with FLK
+ # licenses will be instructed to use this method in order to be able
+ # to use their license.
+ SolverGurobi._env_params = kwargs
 
 
 class ModelGurobiCB(Model):