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Adding parity flip and gamma 5 option for Block KS starting vector

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This commit is contained in:
Chulwoo Jung
2026-06-16 16:05:06 -04:00
parent e862dd662b
commit d2189d59e0
5 changed files with 126 additions and 15 deletions
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Grid/algorithms/Algorithms.h
+1 -1
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@@ -88,7 +88,7 @@ NAMESPACE_CHECK(multigrid);
#include <Grid/algorithms/iterative/KrylovSchur.h>
#include <Grid/algorithms/iterative/BlockKrylovSchur.h>
#include <Grid/algorithms/iterative/SplitGridBlockKrylovSchur.h>
//#include <Grid/algorithms/iterative/HarmonicBlockKrylovSchur.h>
#include <Grid/algorithms/iterative/HarmonicBlockKrylovSchur.h>
#include <Grid/algorithms/iterative/Gamma5BlockLanczos.h>
//#include <Grid/algorithms/iterative/Gamma5ScalarLanczos.h>
#include <Grid/algorithms/iterative/Arnoldi.h>
Grid/algorithms/iterative/BlockKrylovSchur.h
+63 -4
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@@ -124,7 +124,17 @@ protected:
public:
std::vector<Field> evecs;
bool doEvalCheck = false;
bool doEvalCheck = false;
// When true (and Nblock even), only Nblock/2 starting vectors are required.
// The remaining Nblock/2 slots are filled by pairing each supplied vector
// with its parity-flipped partner (sign negated on odd checkerboard sites).
bool useParityFlip = false;
// Same pairing behaviour but the partner is produced by gamma5Func(v).
// gamma5Func must be set by the caller before operator() is called.
// It is a std::function so that BlockKrylovSchur.h does not need to know
// about the Grid QCD Gamma class (which is defined at a later include layer).
bool useGamma5 = false;
std::function<void(const Field&, Field&)> gamma5Func;
//--------------------------------------------------------------------
// Constructor
@@ -161,10 +171,17 @@ public:
Nstop = _Nstop;
Nblock = _Nblock;
assert((int)v0.size() >= Nblock);
{
int divisor = 1;
if (useParityFlip) divisor *= 2;
if (useGamma5) divisor *= 2;
assert(Nblock % divisor == 0 && (int)v0.size() >= Nblock / divisor);
std::cout << GridLogMessage << "BlockKrylovSchur: divisor = " <<divisor << std::endl;
}
assert(Nm % Nblock == 0);
assert(Nk % Nblock == 0);
assert(Nk < Nm);
if (useGamma5) assert(gamma5Func && "useGamma5: gamma5Func must be set");
preRun(); // hook: derived classes add parameter assertions here
int N = Nm; // total Krylov dimension
@@ -179,8 +196,35 @@ public:
H = CMat::Zero(N, N);
B = CMat::Zero(N, Nblock);
// Build the starting block by expanding each seed with the requested
// symmetry partners. Order: {v, flip(v)} then doubled by {·, g5(·)}
// giving {v, flip(v), g5(v), g5(flip(v))} when both flags are set.
int divisor = (useParityFlip ? 2 : 1) * (useGamma5 ? 2 : 1);
std::cout << GridLogMessage << "BlockKrylovSchur: divisor = " <<divisor << std::endl;
int start = 0;
std::vector<Field> startBlock(v0.begin(), v0.begin() + Nblock);
std::vector<Field> startBlock;
startBlock.reserve(Nblock);
for (int i = 0; i < Nblock / divisor; i++) {
std::vector<Field> group;
group.push_back(v0[i]);
if (useParityFlip) {
int n = (int)group.size();
for (int j = 0; j < n; j++) {
Field fp(Grid_);
parityFlippedField(group[j], fp);
group.push_back(std::move(fp));
}
}
if (useGamma5) {
int n = (int)group.size();
for (int j = 0; j < n; j++) {
Field g5v(Grid_);
gamma5Func(group[j], g5v);
group.push_back(std::move(g5v));
}
}
for (auto& f : group) startBlock.push_back(std::move(f));
}
for (int iter = 0; iter < MaxIter; iter++) {
std::cout << GridLogMessage << "BlockKrylovSchur: restart iteration " << iter << std::endl;
@@ -253,7 +297,7 @@ public:
if (Nconv >= Nstop || iter == MaxIter - 1) {
std::cout << GridLogMessage << "BlockKrylovSchur: done after " << iter
<< " restarts, " << Nconv << " converged." << std::endl;
std::cout << GridLogMessage << "Eigenvalues: " << evals.transpose() << std::endl;
std::cout << GridLogMessage << "Eigenvalues: " << evals << std::endl;
if (doEvalCheck) {
Field w(Grid_);
@@ -279,6 +323,21 @@ public:
CVec getEvals() { return evals; }
std::vector<RealD> getRitzEstimates() { return ritzEstimates; }
// Negate the field on all odd-parity (checkerboard) sites.
// Uses pickCheckerboard/setCheckerboard so the SIMD layout is handled
// correctly and the negation runs in parallel.
static void parityFlippedField(const Field& v, Field& out) {
GridCartesian* cgrid = dynamic_cast<GridCartesian*>(v.Grid());
assert(cgrid != nullptr);
GridRedBlackCartesian rbgrid(cgrid);
Field veven(&rbgrid), vodd(&rbgrid);
pickCheckerboard(Even, veven, v);
pickCheckerboard(Odd, vodd, v);
vodd = -vodd;
setCheckerboard(out, veven);
setCheckerboard(out, vodd);
}
//--------------------------------------------------------------------
// Verification: print H and B, check A V = V H + F B^dag explicitly
//--------------------------------------------------------------------
Grid/algorithms/iterative/HarmonicBlockKrylovSchur.h
+47 -3
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@@ -126,7 +126,10 @@ class HarmonicBlockKrylovSchur {
public:
std::vector<Field> evecs;
bool doEvalCheck = false;
bool doEvalCheck = false;
bool useParityFlip = false;
bool useGamma5 = false;
std::function<void(const Field&, Field&)> gamma5Func;
//--------------------------------------------------------------------
// Constructor
@@ -153,10 +156,16 @@ public:
Nstop = _Nstop;
Nblock = _Nblock;
assert((int)v0.size() >= Nblock);
{
int divisor = 1;
if (useParityFlip) divisor *= 2;
if (useGamma5) divisor *= 2;
assert(Nblock % divisor == 0 && (int)v0.size() >= Nblock / divisor);
}
assert(Nm % Nblock == 0);
assert(Nk % Nblock == 0);
assert(Nk < Nm);
if (useGamma5) assert(gamma5Func && "useGamma5: gamma5Func must be set");
int N = Nm;
@@ -170,8 +179,31 @@ public:
H = CMat::Zero(N, N);
B = CMat::Zero(N, Nblock);
int divisor = (useParityFlip ? 2 : 1) * (useGamma5 ? 2 : 1);
int start = 0;
std::vector<Field> startBlock(v0.begin(), v0.begin() + Nblock);
std::vector<Field> startBlock;
startBlock.reserve(Nblock);
for (int i = 0; i < Nblock / divisor; i++) {
std::vector<Field> group;
group.push_back(v0[i]);
if (useParityFlip) {
int n = (int)group.size();
for (int j = 0; j < n; j++) {
Field fp(Grid_);
parityFlippedField(group[j], fp);
group.push_back(std::move(fp));
}
}
if (useGamma5) {
int n = (int)group.size();
for (int j = 0; j < n; j++) {
Field g5v(Grid_);
gamma5Func(group[j], g5v);
group.push_back(std::move(g5v));
}
}
for (auto& f : group) startBlock.push_back(std::move(f));
}
for (int iter = 0; iter < MaxIter; iter++) {
std::cout << GridLogMessage
@@ -280,6 +312,18 @@ public:
CVec getEvals() { return evals; }
std::vector<RealD> getRitzEstimates() { return ritzEstimates; }
static void parityFlippedField(const Field& v, Field& out) {
GridCartesian* cgrid = dynamic_cast<GridCartesian*>(v.Grid());
assert(cgrid != nullptr);
GridRedBlackCartesian rbgrid(cgrid);
Field veven(&rbgrid), vodd(&rbgrid);
pickCheckerboard(Even, veven, v);
pickCheckerboard(Odd, vodd, v);
vodd = -vodd;
setCheckerboard(out, veven);
setCheckerboard(out, vodd);
}
//--------------------------------------------------------------------
// Verification: check A V = V H + F B^dag explicitly
//--------------------------------------------------------------------
examples/Example_krylov_schur.cc
+12 -4
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@@ -334,12 +334,13 @@ int main (int argc, char ** argv)
// Run KrylovSchur and Arnoldi on a Hermitian matrix
RealD shift=LanParams.shift;
#if 1
#if 0
std::cout << GridLogMessage << "Running Krylov Schur" << std::endl;
KrylovSchur KrySchur (Dwilson, UGrid, resid,EvalImNormSmall);
// KrySchur(src[0], maxIter, Nm, Nk, Nstop);
KrySchur.doEvalCheck=true;
KrySchur(src[0], maxIter, Nm, Nk, Nstop,&shift);
// KrySchur(src[0], maxIter, Nm, Nk, Nstop,&shift);
KrySchur(src[0], maxIter, Nm, Nk, Nstop);
std::cout << GridLogMessage << "KrylovSchur evec.size= " << KrySchur.evecs.size()<< std::endl;
#else
std::cout << GridLogMessage << "Running BlockKrylovSchur" << std::endl;
@@ -347,9 +348,16 @@ int main (int argc, char ** argv)
Nblock=LanParams.Nblock;
bool if_verify=false;
if(LanParams.verify) if_verify=true;
BlockKrylovSchur KrySchur (Dwilson, UGrid, resid,EvalImNormSmall);
// HarmonicBlockKrylovSchur KrySchur (Dwilson, UGrid, resid,shift,EvalNormSmall);
// BlockKrylovSchur KrySchur (Dwilson, UGrid, resid,EvalImNormSmall);
HarmonicBlockKrylovSchur KrySchur (Dwilson, UGrid, resid,shift,EvalNormSmall);
KrySchur.doEvalCheck=true;
KrySchur.useParityFlip=true; std::cout << GridLogMessage << "useParityFlip= " <<KrySchur.useParityFlip<< std::endl;
KrySchur.useGamma5=true; std::cout << GridLogMessage << "useGamma5= " <<KrySchur.useGamma5<< std::endl;
KrySchur.gamma5Func = [](const FermionField& v, FermionField& out) {
Gamma g5(Gamma::Algebra::Gamma5);
out = g5 * v;
};
KrySchur(src, maxIter, Nm, Nk, Nstop,Nblock,true,if_verify);
std::cout << GridLogMessage << "BlockKrylovSchur evec.size= " << KrySchur.evecs.size()<< std::endl;
#endif
examples/LanParams.xml
+3 -3
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@@ -5,14 +5,14 @@
<mstep>-0.025</mstep>
<M5>1.8</M5>
<Ls>48</Ls>
<Nstop>800</Nstop>
<Nk>800</Nk>
<Nstop>100</Nstop>
<Nk>100</Nk>
<Np>100</Np>
<ReadEvec>0</ReadEvec>
<maxIter>1000</maxIter>
<reorthog>1</reorthog>
<Nblock>4</Nblock>
<verify>1</verify>
<verify>0</verify>
<shift>1.5</shift>
<resid>1e-8</resid>
<ChebyLow>1</ChebyLow>