fix bfgs bug (#7483)

* fix bfgs bug

* fix bfgs bug

* fix bfgs bug

---------

Co-authored-by: Fei Yang <2501213217@stu.pku.edu.cn>

Author: 19hello

source/source_relax/ions_move_bfgs2.cpp

@@ -80,6 +80,13 @@ bool Ions_Move_BFGS2::relax_step(const ModuleBase::matrix& _force,UnitCell& ucel
     this->UpdatePos(ucell);
     this->CalculateLargestGrad(_force,ucell);
     bool converged = this->IsRestrain(); 
+    if (converged)
+    {
+        ofs_running << "\n Largest force is " << largest_grad * ModuleBase::Ry_to_eV / ModuleBase::BOHR_TO_A
+                    << " eV/Angstrom while threshold is "
+                    << PARAM.inp.force_thr_ev << " eV/Angstrom" << std::endl;
+        ofs_running << "\n Ion relaxation is converged!" << std::endl;
+    }
    // print out geometry information during bfgs_trad relax 
     unitcell::print_tau(ucell.atoms,ucell.Coordinate,ucell.ntype,ucell.lat0,ofs_running);
     return converged;
@@ -239,7 +246,12 @@ void Ions_Move_BFGS2::Update(std::vector<double>& pos,
         }
     }
     double threshold=1e-7;
-    if(*max_element(dpos.begin(), dpos.end()) < threshold)
+    double max_abs_dpos = 0.0;
+    for (const double value : dpos)
+    {
+        max_abs_dpos = std::max(max_abs_dpos, std::abs(value));
+    }
+    if (max_abs_dpos < threshold)
     {
         return;
     } 

source/source_relax/test/bfgs_test.cpp

@@ -118,6 +118,35 @@ TEST_F(BFGSTest, DetermineStepScaling)
     EXPECT_NEAR(dpos[1][2], 0.05, 1e-12);
 }
 
+TEST_F(BFGSTest, UpdateUsesAbsoluteDisplacementThreshold)
+{
+    UnitCell ucell;
+    ucell.ntype = 1;
+    ucell.nat = 1;
+    ucell.lat0 = 1.0;
+    ucell.latvec.Identity();
+    ucell.atoms = new Atom[ucell.ntype];
+    ucell.atoms[0].na = 1;
+    ucell.atoms[0].mbl = std::vector<ModuleBase::Vector3<int>>(1, {1, 1, 1});
+    ucell.iat2it = new int[ucell.nat];
+    ucell.iat2ia = new int[ucell.nat];
+    ucell.iat2it[0] = 0;
+    ucell.iat2ia[0] = 0;
+
+    bfgs.allocate(ucell.nat);
+    bfgs.sign = false;
+    bfgs.pos_taud[0].x = -1.0e-6;
+    bfgs.force0 = {0.0, 0.0, 0.0};
+
+    std::vector<double> pos = {0.0, 0.0, 0.0};
+    std::vector<double> force = {1.0, 0.0, 0.0};
+    const double initial_h00 = bfgs.H[0][0];
+
+    bfgs.Update(pos, force, bfgs.H, ucell);
+
+    EXPECT_NE(bfgs.H[0][0], initial_h00);
+}
+
 // Test GetPos and GetPostaud without creating extra helper class
 TEST_F(BFGSTest, GetPosAndPostaud)
 {
@@ -245,4 +274,4 @@ TEST_F(BFGSTest, RelaxStepBasic)
     // Check that positions are updated (not equal to initial)
     EXPECT_NEAR(bfgs.pos[0][0], 0.0, 1e-12);
     EXPECT_NE(bfgs.pos[1][0], 1.0);
-}
+}