bandwidth for piecewise derivative

Author: jishnub

src/Spaces/ProductSpaceOperators.jl

@@ -227,8 +227,11 @@ for (Op,OpWrap) in ((:Derivative,:DerivativeWrapper),(:Integral,:IntegralWrapper
         @inline function $_Op(S::PiecewiseSpace, k::Number)
             assert_integer(k)
             t = map(s->$Op(s,k),components(S))
+            allbanded = all(isbanded, t)
+            ds, rs = S, SumSpace(map(rangespace, t))
             D = Diagonal(convert_vector_or_svector(t))
-            O = InterlaceOperator(D, PiecewiseSpace)
+            bw = interlace_bandwidths(D, ds, rs, allbanded)
+            O = InterlaceOperator(D, ds, rs, bw)
             $OpWrap(O,k)
         end
         @inline function $_Op(S::ArraySpace, k::Number)
@@ -257,7 +260,7 @@ end
         allbanded = all(isbanded, t)
         D = Diagonal(convert_vector_or_svector(t))
         ds, rs = S, SumSpace(map(rangespace, t))
-        bw = interlace_bandwidths(D, ds, rs)
+        bw = interlace_bandwidths(D, ds, rs, allbanded)
         O = InterlaceOperator(D, ds, rs, bw)
         DerivativeWrapper(O,k)
     else