fix: objective constant bug with presolve (#90)

* fix: objective constant bug with presolve

* update to version 0.2.9

Author: ZedongPeng

CMakeLists.txt

@@ -8,7 +8,7 @@ project(cupdlpx LANGUAGES C CXX CUDA)
 
 set(CUPDLPX_VERSION_MAJOR 0)
 set(CUPDLPX_VERSION_MINOR 2)
-set(CUPDLPX_VERSION_PATCH 8)
+set(CUPDLPX_VERSION_PATCH 9)
 
 set(CUPDLPX_VERSION "${CUPDLPX_VERSION_MAJOR}.${CUPDLPX_VERSION_MINOR}.${CUPDLPX_VERSION_PATCH}")
 add_compile_definitions(CUPDLPX_VERSION="${CUPDLPX_VERSION}")

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "scikit_build_core.build"
 
 [project]
 name = "cupdlpx"
-version = "0.2.8"
+version = "0.2.9"
 description = "Python bindings for cuPDLPx (GPU-accelerated first-order LP solver)"
 readme = "README.md"
 license = { text = "Apache-2.0" }

src/presolve.c

@@ -30,15 +30,15 @@ const char *get_presolve_status_str(enum PresolveStatus_ status)
     }
 }
 
-lp_problem_t *convert_pslp_to_cupdlpx(PresolvedProblem *reduced_prob)
+lp_problem_t *convert_pslp_to_cupdlpx(PresolvedProblem *reduced_prob, const lp_problem_t *original_prob)
 {
 
     lp_problem_t *cupdlpx_prob = (lp_problem_t *)safe_malloc(sizeof(lp_problem_t));
     // TODO: handle warmstart here
     cupdlpx_prob->primal_start = NULL;
     cupdlpx_prob->dual_start = NULL;
 
-    cupdlpx_prob->objective_constant = reduced_prob->obj_offset;
+    cupdlpx_prob->objective_constant = original_prob->objective_constant + reduced_prob->obj_offset;
     cupdlpx_prob->objective_vector = reduced_prob->c;
 
     cupdlpx_prob->constraint_lower_bound = reduced_prob->lhs;
@@ -114,7 +114,7 @@ cupdlpx_presolve_info_t *pslp_presolve(const lp_problem_t *original_prob, const
     else
     {
         info->problem_solved_during_presolve = false;
-        info->reduced_problem = convert_pslp_to_cupdlpx(info->presolver->reduced_prob);
+        info->reduced_problem = convert_pslp_to_cupdlpx(info->presolver->reduced_prob, original_prob);
     }
     return info;
 }