From 08d3a82ce01bfd594d375354f318ee2a354deea1 Mon Sep 17 00:00:00 2001
From: Lev Nachmanson <levnach@hotmail.com>
Date: Thu, 2 Nov 2023 11:09:01 -0700
Subject: [PATCH] simplify the jump on entering

---
 src/math/lp/lp_primal_core_solver.h           |  2 +-
 src/math/lp/lp_primal_core_solver_def.h       | 47 ++++---------------
 .../lp/lp_primal_core_solver_tableau_def.h    |  5 +-
 3 files changed, 10 insertions(+), 44 deletions(-)

diff --git a/src/math/lp/lp_primal_core_solver.h b/src/math/lp/lp_primal_core_solver.h
index a239f1472..d34569032 100644
--- a/src/math/lp/lp_primal_core_solver.h
+++ b/src/math/lp/lp_primal_core_solver.h
@@ -231,7 +231,7 @@ namespace lp {
             return rc.var();
         }
 
-    bool try_jump_to_another_bound_on_entering(unsigned entering, const X &theta, X &t, bool &unlimited);
+    bool try_jump_to_another_bound_on_entering(unsigned entering, X &t);
 
     bool try_jump_to_another_bound_on_entering_unlimited(unsigned entering, X &t);
 
diff --git a/src/math/lp/lp_primal_core_solver_def.h b/src/math/lp/lp_primal_core_solver_def.h
index 6ee265e39..f14d268a3 100644
--- a/src/math/lp/lp_primal_core_solver_def.h
+++ b/src/math/lp/lp_primal_core_solver_def.h
@@ -98,48 +98,17 @@ bool lp_primal_core_solver<T, X>::column_is_benefitial_for_entering_basis(unsign
     }
     return false;
 }
-
-template <typename T, typename X> bool lp_primal_core_solver<T, X>::try_jump_to_another_bound_on_entering(unsigned entering,
-                                                                                                          const X & theta,
-                                                                                                          X & t,
-                                                                                                          bool & unlimited) {
-    switch(this->m_column_types[entering]){
-    case column_type::boxed: 
-        if (m_sign_of_entering_delta > 0) {
-            t = this->m_upper_bounds[entering] - this->m_x[entering];
-            if (unlimited || t <= theta){
-                lp_assert(t >= zero_of_type<X>());
-                return true;
-            }
-        } else { // m_sign_of_entering_delta == -1
-            t = this->m_x[entering] - this->m_lower_bounds[entering];
-            if (unlimited || t <= theta) {
-                lp_assert(t >= zero_of_type<X>());
-                return true;
-            }
-        }
+// we assume that the columns are at their bounds
+template <typename T, typename X> bool lp_primal_core_solver<T, X>::try_jump_to_another_bound_on_entering(unsigned entering, X & theta) {
+    if (this->m_column_types[entering] != column_type::boxed)
         return false;
-    case column_type::upper_bound:
-        if (m_sign_of_entering_delta > 0) {
-            t = this->m_upper_bounds[entering] - this->m_x[entering];
-            if (unlimited || t <= theta){
-                lp_assert(t >= zero_of_type<X>());
-                return true;
-            }
-        }
-        return false;
-    case column_type::lower_bound:
-        if (m_sign_of_entering_delta < 0) {
-                t = this->m_x[entering] - this->m_lower_bounds[entering];
-                if (unlimited || t <= theta) {
-                    lp_assert(t >= zero_of_type<X>());
-                    return true;
-                }
-        }
-        return false;
-    default:return false;
+    X t = this->m_upper_bounds[entering] - this->m_lower_bounds[entering];
+    if (t <= theta) {
+        theta = t;
+        return true;
     }
     return false;
+    
 }
 
 template <typename T, typename X> bool lp_primal_core_solver<T, X>::
diff --git a/src/math/lp/lp_primal_core_solver_tableau_def.h b/src/math/lp/lp_primal_core_solver_tableau_def.h
index a700dbd29..437d27ae8 100644
--- a/src/math/lp/lp_primal_core_solver_tableau_def.h
+++ b/src/math/lp/lp_primal_core_solver_tableau_def.h
@@ -246,10 +246,7 @@ template <typename T, typename X> int lp_primal_core_solver<T, X>::find_leaving_
         }
     }
 
-    ratio = t;
-    unlimited = false;
-    if (try_jump_to_another_bound_on_entering(entering, t, ratio, unlimited)) {
-        t = ratio;
+    if (try_jump_to_another_bound_on_entering(entering, t)) {
         return entering;
     }
     if (m_leaving_candidates.size() == 1)