Add function requires_update

src/PointNeighbors.jl

@@ -24,7 +24,7 @@ export foreach_point_neighbor, foreach_neighbor
 export TrivialNeighborhoodSearch, GridNeighborhoodSearch, PrecomputedNeighborhoodSearch
 export DictionaryCellList, FullGridCellList
 export ParallelUpdate, SemiParallelUpdate, SerialUpdate
-export initialize!, update!, initialize_grid!, update_grid!
+export requires_update, initialize!, update!, initialize_grid!, update_grid!
 export PolyesterBackend, ThreadsDynamicBackend, ThreadsStaticBackend
 export PeriodicBox, copy_neighborhood_search
 

src/neighborhood_search.jl

@@ -2,6 +2,16 @@ abstract type AbstractNeighborhoodSearch end
 
 @inline search_radius(search::AbstractNeighborhoodSearch) = search.search_radius
 
+"""
+    requires_update(search::AbstractNeighborhoodSearch)
+
+Returns a tuple `(x_changed, y_changed)` indicating if this type of neighborhood search
+requires an update when the coordinates of the points in `x` or `y` change.
+"""
+function requires_update(::AbstractNeighborhoodSearch)
+    error("`requires_update` not implemented for this neighborhood search.")
+end
+
 """
     initialize!(search::AbstractNeighborhoodSearch, x, y)
 
@@ -206,13 +216,32 @@ end
     return nothing
 end
 
-@inline function foreach_neighbor(f, system_coords, neighbor_system_coords,
-                                  neighborhood_search, point;
-                                  search_radius = search_radius(neighborhood_search))
+@propagate_inbounds function foreach_neighbor(f, system_coords, neighbor_system_coords,
+                                              neighborhood_search::AbstractNeighborhoodSearch,
+                                              point;
+                                              search_radius = search_radius(neighborhood_search))
+    # Due to https://github.com/JuliaLang/julia/issues/30411, we cannot just remove
+    # a `@boundscheck` by calling this function with `@inbounds` because it has a kwarg.
+    # We have to use `@propagate_inbounds`, which will also remove boundschecks
+    # in the neighbor loop, which is not safe (see comment below).
+    # To avoid this, we have to use a function barrier to disable the `@inbounds` again.
+    point_coords = extract_svector(system_coords, Val(ndims(neighborhood_search)), point)
+
+    foreach_neighbor(f, neighbor_system_coords, neighborhood_search,
+                     point, point_coords, search_radius)
+end
+
+# This is the generic function that is called for `TrivialNeighborhoodSearch`.
+# For `GridNeighborhoodSearch`, a specialized function is used for slightly better
+# performance. `PrecomputedNeighborhoodSearch` can skip the distance check altogether.
+@inline function foreach_neighbor(f, neighbor_system_coords,
+                                  neighborhood_search::AbstractNeighborhoodSearch,
+                                  point, point_coords, search_radius)
     (; periodic_box) = neighborhood_search
 
-    point_coords = extract_svector(system_coords, Val(ndims(neighborhood_search)), point)
     for neighbor in eachneighbor(point_coords, neighborhood_search)
+        # Making the following `@inbounds` yields a ~2% speedup on an NVIDIA H100.
+        # But we don't know if `neighbor` (extracted from the cell list) is in bounds.
         neighbor_coords = extract_svector(neighbor_system_coords,
                                           Val(ndims(neighborhood_search)), neighbor)
 

src/nhs_grid.jl

@@ -103,6 +103,10 @@ function GridNeighborhoodSearch{NDIMS}(; search_radius = 0.0, n_points = 0,
                                   cell_size, update_buffer, update_strategy)
 end
 
+@inline Base.ndims(::GridNeighborhoodSearch{NDIMS}) where {NDIMS} = NDIMS
+
+@inline requires_update(::GridNeighborhoodSearch) = (false, true)
+
 """
     ParallelUpdate()
 
@@ -158,8 +162,6 @@ end
     push!(update_buffer, index_type(cell_list)[])
 end
 
-@inline Base.ndims(::GridNeighborhoodSearch{NDIMS}) where {NDIMS} = NDIMS
-
 function initialize!(neighborhood_search::GridNeighborhoodSearch,
                      x::AbstractMatrix, y::AbstractMatrix)
     initialize_grid!(neighborhood_search, y)
@@ -355,24 +357,11 @@ function update_grid!(neighborhood_search::GridNeighborhoodSearch{<:Any, Paralle
     return neighborhood_search
 end
 
-@propagate_inbounds function foreach_neighbor(f, system_coords, neighbor_system_coords,
-                                              neighborhood_search::GridNeighborhoodSearch,
-                                              point;
-                                              search_radius = search_radius(neighborhood_search))
-    # Due to https://github.com/JuliaLang/julia/issues/30411, we cannot just remove
-    # a `@boundscheck` by calling this function with `@inbounds` because it has a kwarg.
-    # We have to use `@propagate_inbounds`, which will also remove boundschecks
-    # in the neighbor loop, which is not safe (see comment below).
-    # To avoid this, we have to use a function barrier to disable the `@inbounds` again.
-    point_coords = extract_svector(system_coords, Val(ndims(neighborhood_search)), point)
-
-    __foreach_neighbor(f, system_coords, neighbor_system_coords, neighborhood_search,
-                       point, point_coords, search_radius)
-end
-
-@inline function __foreach_neighbor(f, system_coords, neighbor_system_coords,
-                                    neighborhood_search::GridNeighborhoodSearch,
-                                    point, point_coords, search_radius)
+# Specialized version of the function in `neighborhood_search.jl`, which is faster
+# than looping over `eachneighbor`.
+@inline function foreach_neighbor(f, neighbor_system_coords,
+                                  neighborhood_search::GridNeighborhoodSearch,
+                                  point, point_coords, search_radius)
     (; periodic_box) = neighborhood_search
 
     cell = cell_coords(point_coords, neighborhood_search)
@@ -393,8 +382,7 @@ end
             distance2 = dot(pos_diff, pos_diff)
 
             pos_diff, distance2 = compute_periodic_distance(pos_diff, distance2,
-                                                            search_radius,
-                                                            periodic_box)
+                                                            search_radius, periodic_box)
 
             if distance2 <= search_radius^2
                 distance = sqrt(distance2)

src/nhs_precomputed.jl

@@ -45,6 +45,8 @@ end
 
 @inline Base.ndims(::PrecomputedNeighborhoodSearch{NDIMS}) where {NDIMS} = NDIMS
 
+@inline requires_update(::PrecomputedNeighborhoodSearch) = (true, true)
+
 @inline function search_radius(search::PrecomputedNeighborhoodSearch)
     return search_radius(search.neighborhood_search)
 end
@@ -92,14 +94,17 @@ function initialize_neighbor_lists!(neighbor_lists, neighborhood_search, x, y)
     end
 end
 
-@inline function foreach_neighbor(f, system_coords, neighbor_system_coords,
+@inline function foreach_neighbor(f, neighbor_system_coords,
                                   neighborhood_search::PrecomputedNeighborhoodSearch,
-                                  point; search_radius = nothing)
+                                  point, point_coords, search_radius)
     (; periodic_box, neighbor_lists) = neighborhood_search
-    (; search_radius) = neighborhood_search.neighborhood_search
 
-    point_coords = extract_svector(system_coords, Val(ndims(neighborhood_search)), point)
-    for neighbor in neighbor_lists[point]
+    neighbors = @inbounds neighbor_lists[point]
+    for neighbor_ in eachindex(neighbors)
+        neighbor = @inbounds neighbors[neighbor_]
+
+        # Making the following `@inbounds` yields a ~2% speedup on an NVIDIA H100.
+        # But we don't know if `neighbor` (extracted from the cell list) is in bounds.
         neighbor_coords = extract_svector(neighbor_system_coords,
                                           Val(ndims(neighborhood_search)), neighbor)
 

src/nhs_trivial.jl

@@ -30,6 +30,8 @@ end
 
 @inline Base.ndims(::TrivialNeighborhoodSearch{NDIMS}) where {NDIMS} = NDIMS
 
+@inline requires_update(::TrivialNeighborhoodSearch) = (false, false)
+
 @inline initialize!(search::TrivialNeighborhoodSearch, x, y) = search
 
 @inline function update!(search::TrivialNeighborhoodSearch, x, y;