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fixed ritz estimate bug

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This commit is contained in:
Patrick Oare
2025-11-07 18:56:08 +00:00
parent 68af1bba67
commit 0b457b9d52
1 changed files with 17 additions and 3 deletions
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Grid/algorithms/iterative/KrylovSchur.h
+17 -3
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@@ -531,7 +531,7 @@ class KrylovSchur {
{ {
std::cout << GridLogMessage << "Computing eigenvalues." << std::endl; std::cout << GridLogMessage << "Computing eigenvalues." << std::endl;
evals = S.diagonal(); // evals = S.diagonal();
int n = evals.size(); // should be regular Nm int n = evals.size(); // should be regular Nm
evecs.clear(); evecs.clear();
@@ -543,9 +543,12 @@ class KrylovSchur {
Eigen::ComplexEigenSolver<Eigen::MatrixXcd> es; Eigen::ComplexEigenSolver<Eigen::MatrixXcd> es;
// es.compute(Rayleigh); // es.compute(Rayleigh);
es.compute(S); es.compute(S);
evals = es.eigenvalues();
littleEvecs = es.eigenvectors(); littleEvecs = es.eigenvectors();
std::cout << GridLogDebug << "Little evecs: " << littleEvecs << std::endl; // std::cout << GridLogDebug << "Little evecs: " << littleEvecs << std::endl;
// std::cout << "Rayleigh diag: " << S.diagonal() << std::endl;
// std::cout << "Rayleigh evals: " << evals << std::endl;
// Convert evecs to lattice fields // Convert evecs to lattice fields
for (int k = 0; k < n; k++) { for (int k = 0; k < n; k++) {
@@ -629,7 +632,7 @@ class KrylovSchur {
} }
// Check that Ritz estimate is explicitly || D (Uy) - lambda (Uy) || // Check that Ritz estimate is explicitly || D (Uy) - lambda (Uy) ||
checkRitzEstimate(); // checkRitzEstimate();
return Nconv; return Nconv;
} }
@@ -717,12 +720,23 @@ class KrylovSchur {
*/ */
void checkRitzEstimate(RealD tol = 1e-8) { void checkRitzEstimate(RealD tol = 1e-8) {
std::cout << GridLogMessage << "*** CHECKING RITZ ESTIMATE *** " << std::endl; std::cout << GridLogMessage << "*** CHECKING RITZ ESTIMATE *** " << std::endl;
// The issue was that the Eigen::eigensolver occasionally returned the complex conjugate pairs in the wrong
// order compared to the diagonal, which is how I was reading them out. When this happened, the Ritz estimate would
// be wrong. So, just need to be more careful and actually read out the eigenvalues.
Field tmp (Grid); Field tmp (Grid);
// std::cout << "n evecs: " << evecs.size() << std::endl;
for (int k = 0; k < evecs.size(); k++) { for (int k = 0; k < evecs.size(); k++) {
tmp = Zero(); tmp = Zero();
Linop.Op(evecs[k], tmp); // D evec Linop.Op(evecs[k], tmp); // D evec
RealD ritz = std::sqrt(norm2(tmp - evals[k] * evecs[k])); RealD ritz = std::sqrt(norm2(tmp - evals[k] * evecs[k]));
std::cout << "Ritz estimate " << k << " = " << ritz << std::endl; std::cout << "Ritz estimate " << k << " = " << ritz << std::endl;
// Checking little Ritz estimate
// Eigen::VectorXcd littleEvec = littleEvecs.col(k);
// Eigen::VectorXcd dev = Rayleigh * littleEvec - evals[k] * littleEvec;
// std::cout << GridLogMessage << "Little Ritz estimate = " << dev.norm() << std::endl;
} }
return; return;
} }