revamp range computation

Author: dkarrasch

src/blockmap.jl

@@ -24,6 +24,13 @@ BlockMap{T}(maps::As, rows::Rs) where {T, As<:LinearMapTuple, Rs} =
 
 MulStyle(A::BlockMap) = MulStyle(A.maps...)
 
+@inline function _getranges(maps, dim, inds::NTuple{N,Int}=ntuple(identity, Val(length(maps)))) where {N}
+    sizes = ntuple(i -> (@inbounds size(maps[inds[i]], dim)), Val(length(inds)))
+    ends = cumsum(sizes)
+    starts = (1, (1 .+ Base.front(ends))...)
+    return UnitRange.(starts, ends)
+end
+
 """
     rowcolranges(maps, rows)
 
@@ -32,24 +39,19 @@ map in `maps`, according to its position in a virtual matrix representation of t
 block linear map obtained from `hvcat(rows, maps...)`.
 """
 function rowcolranges(maps, rows)
-    rowranges::NTuple{length(rows),UnitRange{Int}} = ntuple(n->1:0, Val(length(rows)))
-    colranges::NTuple{length(maps),UnitRange{Int}} = ntuple(n->1:0, Val(length(maps)))
-    mapind = 0
-    rowstart = 1
-    for (i, row) in enumerate(rows)
-        mapind += 1
-        rowend = rowstart + Int(size(maps[mapind], 1))::Int - 1
-        rowranges = Base.setindex(rowranges, rowstart:rowend, i)
-        colstart = 1
-        colend = Int(size(maps[mapind], 2))::Int
-        colranges = Base.setindex(colranges, colstart:colend, mapind)
-        for colind in 2:row
-            mapind += 1
-            colstart = colend + 1
-            colend += Int(size(maps[mapind], 2))::Int
-            colranges = Base.setindex(colranges, colstart:colend, mapind)
-        end
-        rowstart = rowend + 1
+    # find indices of the row-wise first maps
+    firstmapinds = cumsum((1, Base.front(rows)...))
+    # compute rowranges from size(map, 1) of the row-wise first maps
+    rowranges = _getranges(maps, 1, firstmapinds)
+
+    # compute ranges from size(map, 1) as if all in one row
+    temp = _getranges(maps, 2)
+    # introduce "line breaks"
+    colranges = ntuple(Val(length(maps))) do i
+        # for each map find the index of the respective row-wise first map
+        firstmapind = firstmapinds[something(findlast(<=(i), firstmapinds), 1)]
+        # shift ranges by the first col-index of the row-wise first map
+        return temp[i] .- first(temp[firstmapind]) .+ 1
     end
     return rowranges, colranges
 end