Excited states

src/fciqmc.jl

@@ -188,4 +188,18 @@ end
 function advance!(algorithm, report, state::ReplicaState, replica::SpectralState{1})
  return advance!(algorithm, report, state, only(replica.single_states))
 end
-# TODO: add advance! for SpectralState{N} where N > 1
+
+function advance!(algorithm, report, state::ReplicaState, replica::SpectralState{N, NS, GramSchmidt{N}}) where {N, NS}
+ proceed = true
+ if state.step[] % replica.spectral_strategy.orthogonalisation_interval == 0
+ for i in 1:N
+ for j in 1:i-1
+ add!(replica[i].v, replica[j].v, -1*dot(replica[j].v,replica[i].v)/dot(replica[j].v, replica[j].v), One())
+ end
+ end
+ end
+ for i in 1:N
+ proceed &= advance!(algorithm, report, state, replica[i])
+ end
+ return proceed
+end

src/strategies_and_params/spectralstrategy.jl

@@ -18,11 +18,12 @@ num_spectral_states(::SpectralStrategy{S}) where {S} = S
  GramSchmidt{S} <: SpectralStrategy{S}
 
 Use the Gram-Schmidt procedure to orthogonalize the excited states. A total of `S` spectral
-states are used in the simulation.
+states are used in the simulation, and they are orthogonalised every `orthogonalisation_interval` steps.
 """
-struct GramSchmidt{S} <: SpectralStrategy{S} end
+struct GramSchmidt{S} <: SpectralStrategy{S}
+ orthogonalisation_interval::Int
+end
 
-function GramSchmidt(num_spectral_states = 1)
- num_spectral_states > 1 && throw(ArgumentError("num_spectral_states > 1 is currently not supported."))
- GramSchmidt{num_spectral_states}()
+function GramSchmidt(num_spectral_states = 1, orthogonalisation_interval = 1)
+ return GramSchmidt{num_spectral_states}(orthogonalisation_interval)
 end