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Merged
jajhall merged 22 commits into from
Aug 6, 2025
Merged

IIS "light" #2456

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9ed99dd
Created Highs::getIisLp and testing in lp-incompatible-bounds
jajhall Jul 4, 2025
cf3d5e9
lp-incompatible-bounds passes
jajhall Jul 4, 2025
a84beb7
Switching to markov
jajhall Jul 4, 2025
9fda01e
Now setting just the bounds given by col/row_bounds in the IIS; formated
jajhall Jul 4, 2025
b7fe821
lp-empty-infeasible-row passes
jajhall Jul 4, 2025
f287093
All IIS unit tests pass for IIS LP
jajhall Jul 5, 2025
81fcd9d
Need to be able to generate the IIS LP internally for checking IIS
jajhall Jul 6, 2025
eab8b22
Form IIS LP with IIS, and hold it as a member of HighsIis
jajhall Jul 6, 2025
df6321b
Added HighsLp member to HighsIis as IIS LP, and eliminated Highs::get…
jajhall Jul 6, 2025
ab329a0
Cleaned up and updated FEATURES.md
jajhall Jul 6, 2025
d175741
Added IisStrategy and IisStatus enums contents to highs_c_api.h
jajhall Jul 7, 2025
dda695d
Added variable/constraint IIS status
jajhall Jul 7, 2025
5babefd
Commented out code for HighsIisStatus in highs_bindings.cpp: leave it…
jajhall Jul 7, 2025
37fb045
ctest passes
jajhall Jul 9, 2025
a23df45
ctest passes silently
jajhall Jul 9, 2025
2d0bb19
Created C API methods for IIS
jajhall Jul 9, 2025
4c1099f
C API compiles
jajhall Jul 9, 2025
d04c148
Need to have HighsIis::getLp working for row-wise incumbent LP
jajhall Jul 9, 2025
d6b8feb
Test C API exploses IIS creation bug
jajhall Jul 9, 2025
1aafc1b
Added 3-variable 2-constraint IIS test to TestCAPI.c; formatted
jajhall Jul 10, 2025
9b702ca
Merged latest into this branch and fixed minor conflicts
jajhall Aug 6, 2025
c6a70c5
Added to FEATURES.md, and corrected IIS docstring in Highs.h
jajhall Aug 6, 2025
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181 changes: 148 additions & 33 deletions check/TestCAPI.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1991,7 +1991,7 @@ void testDualRayTwice() {
void* highs = Highs_create();
Highs_setBoolOptionValue(highs, "output_flag", dev_run);
int ret;
double INF = Highs_getInfinity(highs);
double inf = Highs_getInfinity(highs);
ret = Highs_changeObjectiveOffset(highs, 0.0);
assert(ret == 0);
ret = Highs_setStringOptionValue(highs, "presolve", "off");
Expand All @@ -2000,9 +2000,9 @@ void testDualRayTwice() {
assert(ret == 0);
ret = Highs_addCol(highs, 0.0, 0.0, 0.0, 0, NULL, NULL);
assert(ret == 0);
ret = Highs_addCol(highs, -1.0, 0.0, INF, 0, NULL, NULL);
ret = Highs_addCol(highs, -1.0, 0.0, inf, 0, NULL, NULL);
assert(ret == 0);
ret = Highs_addCol(highs, -1.0, 0.0, INF, 0, NULL, NULL);
ret = Highs_addCol(highs, -1.0, 0.0, inf, 0, NULL, NULL);
assert(ret == 0);
HighsInt index[2] = {2, 3};
double value[2] = {1.0, -1.0};
Expand All @@ -2012,19 +2012,19 @@ void testDualRayTwice() {
index[1] = 3;
value[0] = 1.0;
value[1] = 1.0;
ret = Highs_addRow(highs, 1.0, INF, 2, index, value);
ret = Highs_addRow(highs, 1.0, inf, 2, index, value);
assert(ret == 0);
index[0] = 0;
index[1] = 2;
value[0] = -2.0;
value[1] = 1.0;
ret = Highs_addRow(highs, -INF, 0.0, 2, index, value);
ret = Highs_addRow(highs, -inf, 0.0, 2, index, value);
assert(ret == 0);
index[0] = 1;
index[1] = 3;
value[0] = -3.0;
value[1] = 1.0;
ret = Highs_addRow(highs, -INF, 0.0, 2, index, value);
ret = Highs_addRow(highs, -inf, 0.0, 2, index, value);
assert(ret == 0);
ret = Highs_run(highs);
assert(ret == 0);
Expand Down Expand Up @@ -2105,16 +2105,16 @@ void testDeleteRowResolveWithBasis() {
void* highs = Highs_create();
Highs_setBoolOptionValue(highs, "output_flag", dev_run);
HighsInt ret;
double INF = Highs_getInfinity(highs);
double inf = Highs_getInfinity(highs);
ret = Highs_addCol(highs, 0.0, 2.0, 2.0, 0, NULL, NULL);
ret = Highs_addCol(highs, 0.0, -INF, INF, 0, NULL, NULL);
ret = Highs_addCol(highs, 0.0, -INF, INF, 0, NULL, NULL);
ret = Highs_addCol(highs, 0.0, -inf, inf, 0, NULL, NULL);
ret = Highs_addCol(highs, 0.0, -inf, inf, 0, NULL, NULL);
HighsInt index_1[2] = {0, 2};
double value_1[2] = {2.0, -1.0};
ret = Highs_addRow(highs, 0.0, 0.0, 2, index_1, value_1);
HighsInt index_2[1] = {1};
double value_2[1] = {6.0};
ret = Highs_addRow(highs, 10.0, INF, 1, index_2, value_2);
ret = Highs_addRow(highs, 10.0, inf, 1, index_2, value_2);
Highs_run(highs);
double col_value[3] = {0.0, 0.0, 0.0};
Highs_getSolution(highs, col_value, NULL, NULL, NULL);
Expand All @@ -2129,30 +2129,145 @@ void testDeleteRowResolveWithBasis() {
Highs_destroy(highs);
}

void testIis() {
void* highs = Highs_create();
Highs_setBoolOptionValue(highs, "output_flag", dev_run);
HighsInt ret;
double inf = Highs_getInfinity(highs);
// For the constraints
//
// x + y - z = 2
//
// x + y + z <= 5
//
// x + 2y + z <= 1
//
// with variables in [0, 1], constraints 0 and 2 form an IIS with
//
// x free (so should be removed?); 0 <= y; 0 <= z
//
// x + y - z >= 2; x + 2y + z <= 1
//
ret = Highs_addCol(highs, 0.0, 0.0, 1.0, 0, NULL, NULL);
assert(ret == 0);
ret = Highs_addCol(highs, 0.0, 0.0, 1.0, 0, NULL, NULL);
assert(ret == 0);
ret = Highs_addCol(highs, 0.0, 0.0, 1.0, 0, NULL, NULL);
assert(ret == 0);
HighsInt index[3] = {0, 1, 2};
double value_1[3] = {1, 1, -1};
double value_2[3] = {1, 1, 1};
double value_3[3] = {1, 2, 1};
ret = Highs_addRow(highs, 2.0, 2.0, 3, index, value_1);
assert(ret == 0);
ret = Highs_addRow(highs, -inf, 5.0, 3, index, value_2);
assert(ret == 0);
ret = Highs_addRow(highs, -inf, 1.0, 3, index, value_3);
assert(ret == 0);

HighsInt num_col;
HighsInt num_row;
HighsInt num_nz;
HighsInt sense;
double offset;
ret = Highs_getLp(highs, kHighsMatrixFormatRowwise,
&num_col, &num_row, &num_nz,
&sense, &offset,
NULL, NULL, NULL,
NULL, NULL,
NULL, NULL, NULL,
NULL);

for (int k = 0 ; k < 2; k++) {
HighsInt iis_num_col;
HighsInt iis_num_row;
ret = Highs_getIis(highs,
&iis_num_col, &iis_num_row,
NULL, NULL,
NULL, NULL,
NULL, NULL);
assert(ret == 0);

if (k == 0) {
// No IIS from kHighsIisStrategyLight
assert(iis_num_col == 0);
assert(iis_num_row == 0);
Highs_setIntOptionValue(highs, "iis_strategy",
kHighsIisStrategyFromLpRowPriority);
} else {
assert(iis_num_col == 3);
assert(iis_num_row == 2);
HighsInt* col_index = (HighsInt*)malloc(sizeof(HighsInt) * iis_num_col);
HighsInt* row_index = (HighsInt*)malloc(sizeof(HighsInt) * iis_num_row);
HighsInt* col_bound = (HighsInt*)malloc(sizeof(HighsInt) * iis_num_col);
HighsInt* row_bound = (HighsInt*)malloc(sizeof(HighsInt) * iis_num_row);
HighsInt* col_status = (HighsInt*)malloc(sizeof(HighsInt) * num_col);
HighsInt* row_status = (HighsInt*)malloc(sizeof(HighsInt) * num_row);
ret = Highs_getIis(highs,
&iis_num_col, &iis_num_row,
col_index, row_index,
col_bound, row_bound,
col_status, row_status);
assert(ret == 0);

assert(col_index[0] == 0);
assert(col_index[1] == 1);
assert(col_index[2] == 2);

assert(row_index[0] == 0);
assert(row_index[1] == 2);

assert(col_bound[0] == kHighsIisBoundFree);
assert(col_bound[1] == kHighsIisBoundLower);
assert(col_bound[2] == kHighsIisBoundLower);

assert(row_bound[0] == kHighsIisBoundLower);
assert(row_bound[1] == kHighsIisBoundUpper);

assert(col_status[0] == kHighsIisStatusInConflict);
assert(col_status[1] == kHighsIisStatusInConflict);
assert(col_status[2] == kHighsIisStatusInConflict);

assert(row_status[0] == kHighsIisStatusInConflict);
assert(row_status[1] == kHighsIisStatusNotInConflict);
assert(row_status[2] == kHighsIisStatusInConflict);

free(col_index);
free(row_index);
free(col_bound);
free(row_bound);
free(col_status);
free(row_status);
}
}

Highs_destroy(highs);
}

int main() {
minimalApiIllegalLp();
testCallback();
versionApi();
fullApi();
minimalApiLp();
minimalApiMip();
minimalApiQp();
fullApiOptions();
fullApiLp();
fullApiMip();
fullApiQp();
passPresolveGetLp();
options();
testGetColsByRange();
testPassHessian();
testRanging();
testFeasibilityRelaxation();
testGetModel();
testMultiObjective();
testQpIndefiniteFailure();
testDualRayTwice();

testDeleteRowResolveWithBasis();
minimalApiIllegalLp();
testCallback();
versionApi();
fullApi();
minimalApiLp();
minimalApiMip();
minimalApiQp();
fullApiOptions();
fullApiLp();
fullApiMip();
fullApiQp();
passPresolveGetLp();
options();
testGetColsByRange();
testPassHessian();
testRanging();
testFeasibilityRelaxation();
testGetModel();
testMultiObjective();
testQpIndefiniteFailure();
testDualRayTwice();
testDeleteRowResolveWithBasis();
testIis();
return 0;
}
// testSetSolution();
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