Add a reinit function

Author: avik-pal

src/termination_conditions.jl

@@ -259,7 +259,7 @@ function SciMLBase.init(du::Union{AbstractArray{T}, T}, u::Union{AbstractArray{T
                           Vector{TT}(undef, mode.max_stalled_steps)
         best_value = initial_objective
         max_stalled_steps = mode.max_stalled_steps
-        if ArrayInterface.can_setindex(u_) && step_norm_trace !== nothing
+        if ArrayInterface.can_setindex(u_) && !(u_ isa Number) && step_norm_trace !== nothing
             u_diff_cache = similar(u_)
         else
             u_diff_cache = u_
@@ -286,37 +286,38 @@ function SciMLBase.init(du::Union{AbstractArray{T}, T}, u::Union{AbstractArray{T
         step_norm_trace, max_stalled_steps, u_diff_cache)
 end
 
-# function SciMLBase.reinit!(cache::NonlinearTerminationModeCache{uType, T, dep_retcode}, du,
-#         u, saved_value_prototype...; abstol = nothing, reltol = nothing,
-#         kwargs...) where {uType, T, dep_retcode}
-#     length(saved_value_prototype) != 0 && (cache.saved_values = saved_value_prototype)
-
-#     u_ = cache.mode isa AbstractSafeBestNonlinearTerminationMode ?
-#          (ArrayInterface.can_setindex(u) ? copy(u) : u) : nothing
-#     cache.u = u_
-#     cache.retcode = ifelse(dep_retcode, NonlinearSafeTerminationReturnCode.Default,
-#         ReturnCode.Default)
-
-#     cache.abstol = _get_tolerance(abstol, T)
-#     cache.reltol = _get_tolerance(reltol, T)
-#     cache.nsteps = 0
-
-#     if mode isa AbstractSafeNonlinearTerminationMode
-#         if mode isa AbsSafeTerminationMode || mode isa AbsSafeBestTerminationMode
-#             initial_objective = maximum(abs, du)
-#         else
-#             initial_objective = maximum(abs, du) / (maximum(abs, du .+ u) + eps(TT))
-#         end
-#         best_value = initial_objective
-#     else
-#         initial_objective = nothing
-#         objectives_trace = nothing
-#         best_value = __cvt_real(T, Inf)
-#     end
-#     cache.best_objective_value = best_value
-#     cache.initial_objective = initial_objective
-#     return cache
-# end
+function SciMLBase.reinit!(cache::NonlinearTerminationModeCache{uType, T, dep_retcode}, du,
+        u, saved_value_prototype...; abstol = nothing, reltol = nothing,
+        kwargs...) where {uType, T, dep_retcode}
+    length(saved_value_prototype) != 0 && (cache.saved_values = saved_value_prototype)
+
+    u_ = cache.mode isa AbstractSafeBestNonlinearTerminationMode ?
+         (ArrayInterface.can_setindex(u) ? copy(u) : u) : nothing
+    cache.u = u_
+    cache.retcode = ifelse(dep_retcode, NonlinearSafeTerminationReturnCode.Default,
+        ReturnCode.Default)
+
+    cache.abstol = _get_tolerance(abstol, T)
+    cache.reltol = _get_tolerance(reltol, T)
+    cache.nsteps = 0
+
+    if mode isa AbstractSafeNonlinearTerminationMode
+        if mode isa AbsSafeTerminationMode || mode isa AbsSafeBestTerminationMode
+            initial_objective = maximum(abs, du)
+        else
+            initial_objective = maximum(abs, du) / (maximum(abs, du .+ u) + eps(TT))
+            cache.max_stalled_steps !== nothing && (cache.u0_norm = norm(u_, 2))
+        end
+        best_value = initial_objective
+    else
+        initial_objective = nothing
+        objectives_trace = nothing
+        best_value = __cvt_real(T, Inf)
+    end
+    cache.best_objective_value = best_value
+    cache.initial_objective = initial_objective
+    return cache
+end
 
 # This dispatch is needed based on how Terminating Callback works!
 # This intentially drops the `abstol` and `reltol` arguments
@@ -399,7 +400,7 @@ function (cache::NonlinearTerminationModeCache{uType, TT, dep_retcode})(mode::Ab
 
     # Test for stalling if that is not disabled
     if cache.step_norm_trace !== nothing
-        if ArrayInterface.can_setindex(cache.u_diff_cache)
+        if ArrayInterface.can_setindex(cache.u_diff_cache) && !(u isa Number)
             @. cache.u_diff_cache = u - uprev
         else
             cache.u_diff_cache = u .- uprev