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run_engine.py
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1
11
12from io import StringIO
13import json
14import os
15import sys
16from threading import Thread
17import time
18from gams import GamsWorkspace, GamsEngineConfiguration, SolveLink
19
20
21GAMS_DATA = """
22Set
23 i 'canning plants' / seattle, san-diego /
24 j 'markets' / new-york, chicago, topeka /;
25
26Parameter
27 a(i) 'capacity of plant i in cases'
28 / seattle 350
29 san-diego 600 /
30
31 b(j) 'demand at market j in cases'
32 / new-york 325
33 chicago 300
34 topeka 275 /;
35
36Table d(i,j) 'distance in thousands of miles'
37 new-york chicago topeka
38 seattle 2.5 1.7 1.8
39 san-diego 2.5 1.8 1.4;
40
41Scalar
42 f 'freight in dollars per case per thousand miles' / 90 /
43 bmult 'demand multiplier' / 1 /;
44"""
45
46GAMS_MODEL = """
47Set
48 i 'canning plants'
49 j 'markets';
50
51Parameter
52 a(i) 'capacity of plant i in cases'
53 b(j) 'demand at market j in cases'
54 d(i,j) 'distance in thousands of miles';
55
56Scalar
57 f 'freight in dollars per case per thousand miles'
58 bmult 'demand multiplier';
59
60$if not set gdxincname $abort 'no include file name for data file provided'
61$gdxIn %gdxincname%
62$load i j a b d f bmult
63$gdxIn
64
65$echo "test" > test.txt
66
67Parameter c(i,j) 'transport cost in thousands of dollars per case';
68c(i,j) = f*d(i,j)/1000;
69
70Variable
71 x(i,j) 'shipment quantities in cases'
72 z 'total transportation costs in thousands of dollars';
73
74Positive Variable x;
75
76Equations
77 cost 'define objective function'
78 supply(i) 'observe supply limit at plant i'
79 demand(j) 'satisfy demand at market j';
80
81cost.. z =e= sum((i,j), c(i,j)*x(i,j));
82
83supply(i).. sum(j, x(i,j)) =l= a(i);
84
85demand(j).. sum(i, x(i,j)) =g= bmult*b(j);
86
87Model transport /all/;
88
89solve transport using lp minimizing z;
90
91Scalar
92 ms 'model status'
93 ss 'solve status';
94
95display x.l, x.m;
96"""
97
98if __name__ == "__main__":
99 sys_dir = sys.argv[1] if len(sys.argv) > 1 else None
100 ws = GamsWorkspace(system_directory=sys_dir)
101
102 # set up configuration required for any job on GAMS Engine
103
104 engine_configuration = GamsEngineConfiguration(
105 host=os.environ["ENGINE_URL"],
106 username=os.environ["ENGINE_USER"],
107 password=os.environ["ENGINE_PASSWORD"],
108 namespace=os.environ["ENGINE_NAMESPACE"],
109 )
110
111 job = ws.add_job_from_string(GAMS_DATA)
112 job.run_engine(engine_configuration)
113 gdx_file_path = os.path.join(ws.working_directory, "tdata.gdx")
114 job.out_db.export(gdx_file_path)
115 job = ws.add_job_from_string(GAMS_MODEL)
116
117 opt = ws.add_options()
118 opt.defines["gdxincname"] = "tdata"
119 opt.all_model_types = "xpress"
120 job.run_engine(
121 engine_configuration,
122 extra_model_files=gdx_file_path,
123 engine_options={
124 "inex_string": json.dumps({"type": "include", "files": ["*.gdx"]})
125 },
126 gams_options=opt,
127 )
128 expected_levels = {
129 ("seattle", "new-york"): 0.0,
130 ("seattle", "chicago"): 300.0,
131 ("seattle", "topeka"): 0.0,
132 ("san-diego", "new-york"): 325.0,
133 ("san-diego", "chicago"): 0.0,
134 ("san-diego", "topeka"): 275.0,
135 }
136
137 for rec in job.out_db["x"]:
138 print(
139 f"x({rec.key(0)},{rec.key(1)}): level={rec.level} marginal={rec.marginal}"
140 )
141 if expected_levels[tuple(rec.keys)] != rec.level:
142 raise Exception("Unexpected results.")
143
144 if os.path.exists(os.path.join(ws.working_directory, "test.txt")):
145 raise Exception("Did not expected to find 'test.txt' written by GAMS model supposed to run remotely.")
146
147 cp = ws.add_checkpoint()
148
149 job_a = ws.add_job_from_string(GAMS_DATA)
150 job_a.run_engine(engine_configuration)
151 opt.defines["gdxincname"] = job_a.out_db.name
152
153 job_b = ws.add_job_from_string(GAMS_MODEL)
154 job_b.run_engine(
155 engine_configuration, gams_options=opt, databases=job_a.out_db, checkpoint=cp
156 )
157
158 for rec in job.out_db["x"]:
159 if expected_levels[tuple(rec.keys)] != rec.level:
160 raise Exception("Unexpected results.")
161
162 expected_bmult = [
163 {"bmult": 0.9, "ms": 1, "ss": 1, "obj": 138.31},
164 {"bmult": 1.2, "ms": 4, "ss": 1, "obj": 184.41},
165 ]
166
167 # create a new GamsJob that is initialized from the GamsCheckpoint
168 for scen in expected_bmult:
169 job = ws.add_job_from_string(
170 f"bmult={scen['bmult']}; solve transport min z use lp; ms=transport.modelstat; ss=transport.solvestat;",
171 cp,
172 )
173 job.run_engine(engine_configuration)
174 print(f"Scenario bmult={scen['bmult']}:")
175 print(f" Modelstatus: {job.out_db['ms'].find_record().value}")
176 print(f" Solvestatus: {job.out_db['ss'].find_record().value}")
177 print(f" Obj: {job.out_db['z'].find_record().level}")
178
179 if job.out_db["bmult"].find_record().value != scen["bmult"]:
180 raise Exception("Unexpected bmult.")
181 if job.out_db["ms"].find_record().value != scen["ms"]:
182 raise Exception("Unexpected model status.")
183 if job.out_db["ss"].find_record().value != scen["ss"]:
184 raise Exception("Unexpected solve status.")
185 if round(job.out_db["z"].find_record().level, 2) != scen["obj"]:
186 raise Exception("Unexpected obj.")
187
188 # example how to interrupt Engine job
189
190 ws.gamslib("clad")
191 job = ws.add_job_from_file("clad")
192
193 # define an option file for the solver to be used
194 option_file1_path = os.path.join(ws.working_directory, "cplex.opt")
195 with open(option_file1_path, "w") as f:
196 # set relative stopping tolerance to 0 initially
197 f.write("epgap 0\n")
198 # activate interactive option setting on interrupt
199 f.write("interactive 1\n")
200 # define new option file to read on interrupt
201 f.write("iafile cplex.op2\n")
202
203 # write new Cplex option file
204 option_file2_path = os.path.join(ws.working_directory, "cplex.op2")
205 with open(option_file2_path, "w") as f:
206 f.write("epgap 0.1")
207
208 opt = ws.add_options()
209 opt.mip = "cplex"
210 opt.optfile = 1
211 opt.solvelink = SolveLink.LoadLibrary
212
213 sw = StringIO()
214
215 # run GamsJob job in separate thread
216 opt_thread = Thread(
217 target=job.run_engine,
218 args=(engine_configuration,),
219 kwargs={
220 "output": sw,
221 "extra_model_files": [option_file1_path, option_file2_path, "claddat.gdx"],
222 "gams_options": opt,
223 },
224 )
225 opt_thread.start()
226
227 while True:
228 if sw.tell() == 0:
229 time.sleep(0.5)
230 continue
231 job.interrupt()
232 print("Interrupted Cplex to continue with new option")
233 break
234
235 # if job is still running, wait until it is finished
236 if opt_thread.is_alive():
237 opt_thread.join()
238 # check if everything worked as expected
239 log = sw.getvalue()
240 if not "Interrupted..." in log:
241 raise Exception("Expected the solver to be interrupted at least once.")