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Refactor: reduce FFT calls in Leps2 #6839

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Merged
mohanchen merged 1 commit into from
Jan 9, 2026
Merged

Refactor: reduce FFT calls in Leps2 #6839

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50 changes: 16 additions & 34 deletions source/source_hamilt/module_surchem/minimize_cg.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -26,16 +26,12 @@ void surchem::minimize_cg(const UnitCell& ucell,

std::complex<double> *gradphi_G_work = new std::complex<double>[rho_basis->npw];

// Removed unused phi_work allocation
// std::complex<double> *phi_work = new std::complex<double>[rho_basis->npw];

// ==========================================================
// PRE-ALLOCATION FOR LEPS2 (Avoids allocation inside loop)
// ==========================================================
ModuleBase::Vector3<double> *aux_grad_phi = new ModuleBase::Vector3<double>[rho_basis->nrxx];
std::complex<double> *aux_grad_grad_phi_G = new std::complex<double>[rho_basis->npw];
double *aux_lp_real = new double[rho_basis->nrxx];
double *aux_grad_grad_phi_real = new double[rho_basis->nrxx];
// remove aux_grad_grad_phi_G and aux_lp_real

ModuleBase::GlobalFunc::ZEROS(resid, rho_basis->npw);
ModuleBase::GlobalFunc::ZEROS(z, rho_basis->npw);
Expand Down Expand Up @@ -68,7 +64,7 @@ void surchem::minimize_cg(const UnitCell& ucell,
// call leps to calculate div ( epsilon * grad ) phi
// Updated Leps2 call with new buffers
Leps2(ucell, rho_basis, phi, d_eps, gradphi_G_work, lp,
aux_grad_phi, aux_grad_grad_phi_G, aux_lp_real, aux_grad_grad_phi_real);
aux_grad_phi, aux_grad_grad_phi_real);

// the residue
// r = A*phi + (chtot + N)
Expand Down Expand Up @@ -106,7 +102,7 @@ void surchem::minimize_cg(const UnitCell& ucell,

// Updated Leps2 call inside loop
Leps2(ucell, rho_basis, d, d_eps, gradphi_G_work, lp,
aux_grad_phi, aux_grad_grad_phi_G, aux_lp_real, aux_grad_grad_phi_real);
aux_grad_phi, aux_grad_grad_phi_real);

// calculate alpha
alpha = -rinvLr / ModuleBase::GlobalFunc::ddot_real(rho_basis->npw, d, lp);
Expand Down Expand Up @@ -161,21 +157,20 @@ void surchem::minimize_cg(const UnitCell& ucell,

// Clean up auxiliary buffers
delete[] aux_grad_phi;
delete[] aux_grad_grad_phi_G;
delete[] aux_lp_real;
// delete[] aux_grad_grad_phi_G; // Removed
// delete[] aux_lp_real; // Removed
delete[] aux_grad_grad_phi_real;
}

// avoid creating large temporary matrices inside its iteration loop
// reduce the intermediate FFT related calls
void surchem::Leps2(const UnitCell& ucell,
const ModulePW::PW_Basis* rho_basis,
std::complex<double>* phi,
double* epsilon, // epsilon from shapefunc, dim=nrxx
std::complex<double>* gradphi_G_work,
std::complex<double>* lp,
ModuleBase::Vector3<double>* grad_phi_R, // size: nrxx
std::complex<double>* aux_G, // size: npw
double* lp_real, // size: nrxx
double* aux_R) // size: nrxx
{

Expand All @@ -190,45 +185,32 @@ void surchem::Leps2(const UnitCell& ucell,
}


ModuleBase::GlobalFunc::ZEROS(lp_real, rho_basis->nrxx);
ModuleBase::GlobalFunc::ZEROS(lp, rho_basis->npw);

// 1. R -> G
// R -> G
for (int ir = 0; ir < rho_basis->nrxx; ir++) aux_R[ir] = grad_phi_R[ir].x;
rho_basis->real2recip(aux_R, gradphi_G_work); //
rho_basis->real2recip(aux_R, gradphi_G_work);


for(int ig=0; ig<rho_basis->npw; ig++) {
aux_G[ig] = ModuleBase::IMAG_UNIT * gradphi_G_work[ig] * rho_basis->gcar[ig][0]; // 0 = x
}
rho_basis->recip2real(aux_G, aux_R);
for(int ir=0; ir<rho_basis->nrxx; ir++) {
lp_real[ir] += aux_R[ir] * ucell.tpiba;
// Divergence in G space: div(F) -> i * G * F(G)
lp[ig] += ModuleBase::IMAG_UNIT * gradphi_G_work[ig] * rho_basis->gcar[ig][0]; // 0 = x
}


for (int ir = 0; ir < rho_basis->nrxx; ir++) aux_R[ir] = grad_phi_R[ir].y;
rho_basis->real2recip(aux_R, gradphi_G_work);

for(int ig=0; ig<rho_basis->npw; ig++) {
aux_G[ig] = ModuleBase::IMAG_UNIT * gradphi_G_work[ig] * rho_basis->gcar[ig][1]; // 1 = y
}
rho_basis->recip2real(aux_G, aux_R);
for(int ir=0; ir<rho_basis->nrxx; ir++) {
lp_real[ir] += aux_R[ir] * ucell.tpiba;
lp[ig] += ModuleBase::IMAG_UNIT * gradphi_G_work[ig] * rho_basis->gcar[ig][1]; // 1 = y
}


for (int ir = 0; ir < rho_basis->nrxx; ir++) aux_R[ir] = grad_phi_R[ir].z;
rho_basis->real2recip(aux_R, gradphi_G_work);

for(int ig=0; ig<rho_basis->npw; ig++) {
aux_G[ig] = ModuleBase::IMAG_UNIT * gradphi_G_work[ig] * rho_basis->gcar[ig][2]; // 2 = z
}
rho_basis->recip2real(aux_G, aux_R);
for(int ir=0; ir<rho_basis->nrxx; ir++) {
lp_real[ir] += aux_R[ir] * ucell.tpiba;
lp[ig] += ModuleBase::IMAG_UNIT * gradphi_G_work[ig] * rho_basis->gcar[ig][2]; // 2 = z
}


rho_basis->real2recip(lp_real, lp);
for(int ig=0; ig<rho_basis->npw; ig++) {
lp[ig] *= ucell.tpiba;
}
}
7 changes: 2 additions & 5 deletions source/source_hamilt/module_surchem/surchem.h
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Original file line number Diff line number Diff line change
Expand Up @@ -100,11 +100,8 @@ class surchem
double* epsilon, // epsilon from shapefunc, dim=nrxx
std::complex<double>* gradphi_G_work,
std::complex<double>* lp,
// New buffers
ModuleBase::Vector3<double>* grad_phi_R,
std::complex<double>* grad_grad_phi_G,
double* lp_real,
double* grad_grad_phi_real);
ModuleBase::Vector3<double>* grad_phi_R, // size: nrxx
double* aux_R);

void v_correction(const UnitCell& cell,
const Parallel_Grid& pgrid,
Expand Down
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