Implement SolverCore.reset!(solver) function (#293)

* add _reset_power_norm function

* add LinearOperators.reset! to reset! quasi-Newton approximations

* fix _reset_power_method to correct output

* implement SolverCore.reset!(solver) functions

* add condition on B before resetting

Author: MaxenceGollier

src/R2DH.jl

@@ -81,6 +81,12 @@ function R2DHSolver(
   )
 end
 
+function SolverCore.reset!(solver::R2DHSolver)
+  LinearOperators.reset!(solver.D)
+end
+
+SolverCore.reset!(solver::R2DHSolver, model) = SolverCore.reset!(solver)
+
 """
     R2DH(reg_nlp; kwargs…)
 

src/R2N.jl

@@ -96,6 +96,14 @@ function R2NSolver(
   )
 end
 
+function SolverCore.reset!(solver::R2NSolver)
+  _reset_power_method!(solver.v0)
+  B = solver.subpb.model.B
+  isa(B, AbstractLinearOperator) && LinearOperators.reset!(B)
+end
+
+SolverCore.reset!(solver::R2NSolver, model) = SolverCore.reset!(solver)
+
 """
     R2N(reg_nlp; kwargs…)
 

src/TRDH_alg.jl

@@ -90,6 +90,12 @@ function TRDHSolver(
   )
 end
 
+function SolverCore.reset!(solver::TRDHSolver)
+  LinearOperators.reset!(solver.D)
+end
+
+SolverCore.reset!(solver::TRDHSolver, model) = SolverCore.reset!(solver)
+
 """
     TRDH(reg_nlp; kwargs…)
     TRDH(nlp, h, χ, options; kwargs...)

src/TR_alg.jl

@@ -95,6 +95,15 @@ function TRSolver(
   )
 end
 
+function SolverCore.reset!(solver::TRSolver)
+  _reset_power_method!(solver.v0)
+  reset_data!(solver.subpb.model)
+  LinearOperators.reset!(solver.subpb.model)
+end
+
+SolverCore.reset!(solver::TRSolver, model) = SolverCore.reset!(solver)
+
+
 """
     TR(reg_nlp; kwargs…)
     TR(nlp, h, χ, options; kwargs...)

src/utils.jl

@@ -2,6 +2,11 @@ export RegularizedExecutionStats
 
 import SolverCore.GenericExecutionStats
 
+# Reset the initial vector for the power method to [1/sqrt(n), -1/sqrt(n), 1/sqrt(n), ...].
+function _reset_power_method!(v0::AbstractVector)
+  v0 .= (isodd.(eachindex(v0)) .* 2 .- 1) ./ sqrt(length(v0))
+end
+
 function power_method!(B::M, v₀::S, v₁::S, max_iter::Int = 1) where {M, S}
   @assert max_iter >= 1 "max_iter must be at least 1."
   mul!(v₁, B, v₀)