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Purging: remove converged, unwanted vecs #140

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Feb 18, 2024
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Purging: remove converged, unwanted vecs #140

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37 changes: 26 additions & 11 deletions src/run.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -240,7 +240,7 @@ function _partialschur(
effective_nev = include_conjugate_pair(T, ritz, nev)

nlock = 0
for i = 1:effective_nev
@inbounds for i = 1:effective_nev
if isconverged(ritz.ord[i])
groups[ritz.ord[i]] = 1
nlock += 1
Expand All @@ -254,15 +254,30 @@ function _partialschur(
# larger than `mindim` when converged Ritz vectors have been locked.
# 2. But `k` can't be so large that the expansion would barely give new information;
# hence we meet in the middle: `k` is at most halfway `mindim` and `maxdim`.
# 3. If `k` ends up on the boundary of a conjugate pair, we increase `k` by 1.
k = include_conjugate_pair(T, ritz, min(nlock + mindim, (mindim + maxdim) ÷ 2))

for i = effective_nev+1:k
groups[ritz.ord[i]] = 2
end

for i = k+1:maxdim
groups[ritz.ord[i]] = 3
# 3. Further we don't want to split on a conjugate pair.
ideal_size = min(nlock + mindim, (mindim + maxdim) ÷ 2)
k = effective_nev
i = effective_nev + 1

@inbounds while i ≤ maxdim
is_pair = include_conjugate_pair(T, ritz, i) == i + 1
num = is_pair ? 2 : 1
if k < ideal_size && !isconverged(ritz.ord[i])
# Keep the best, unconverged Ritz pairs.
group = 2
k += num
else
# Purge converged, unwanted ones, as well as the worst unconverged values.
group = 3
end
if is_pair
groups[ritz.ord[i]] = group
groups[ritz.ord[i+1]] = group
i += 2
else
groups[ritz.ord[i]] = group
i += 1
end
end

# Typically eigenvalues converge in the desired order: closest to the target first and
Expand All @@ -275,7 +290,7 @@ function _partialschur(
# that `purge` can be any index in 1:active-1, because locked vectors are merely
# partitioned as locked vectors, they are never sorted until full convergence.
purge = 1
while purge < active && groups[purge] == 1
@inbounds while purge < active && groups[purge] == 1
purge += 1
end

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