improve type inference in caching (#396)

* improve type inference in caching

* fix CachedOperator for blockbanded

* Add comments

Author: jishnub

Project.toml

@@ -1,6 +1,6 @@
 name = "ApproxFunBase"
 uuid = "fbd15aa5-315a-5a7d-a8a4-24992e37be05"
-version = "0.8.2"
+version = "0.8.3"
 
 [deps]
 AbstractFFTs = "621f4979-c628-5d54-868e-fcf4e3e8185c"

src/Caching/banded.jl

@@ -1,8 +1,10 @@
 function CachedOperator(::Type{BandedMatrix},op::Operator;padding::Bool=false)
-    l,u=bandwidths(op)
-    padding && (u+=l)
-    data = BandedMatrix{eltype(op)}(undef, (0,0), (l,u))
-    CachedOperator(op,data,size(data),domainspace(op),rangespace(op),(-l,u),padding)
+    bw = bandwidths(op)
+    l = first(bw)
+    # working on the tuples directly instead of the components helps with type-stability
+    padding && (bw = bw .+ (0,l))
+    data = BandedMatrix{eltype(op)}(undef, (0,0), bw)
+    CachedOperator(op,data,size(data),domainspace(op),rangespace(op), bw .* (-1,1),padding)
 end
 
 

src/Caching/bandedblockbanded.jl

@@ -1,12 +1,13 @@
 
 function CachedOperator(::Type{BandedBlockBandedMatrix}, op::Operator)
-    l,u = blockbandwidths(op)
-    λ,μ = subblockbandwidths(op)
+    lu = blockbandwidths(op)
+    λμ = subblockbandwidths(op)
+    # working on the tuples directly instead of the components helps with type-stability
     data = BandedBlockBandedMatrix{eltype(op)}(undef,
         blocklengths(rangespace(op))[1:0],blocklengths(domainspace(op))[1:0],
-        (l,u), (λ,μ))
+        lu, λμ)
 
-    CachedOperator(op,data,size(data),domainspace(op),rangespace(op),(-l,u),false)
+    CachedOperator(op,data,size(data),domainspace(op),rangespace(op),lu .* (-1,1),false)
 end
 
 # Grow cached operator

src/Caching/blockbanded.jl

@@ -71,12 +71,13 @@ diagblockshift(op::Operator) = diagblockshift(blocklengths(domainspace(op)),bloc
 
 
 function CachedOperator(::Type{BlockBandedMatrix},op::Operator;padding::Bool=false)
-    l,u=blockbandwidths(op)
-    padding && (u+=l+diagblockshift(op))
-    data=BlockBandedMatrix{eltype(op)}(undef,
-                                        Vector{Int}(), Vector{Int}(),
-                                        (l,u))
-    CachedOperator(op,data,(0,0),domainspace(op),rangespace(op),(-l,u),padding)
+    lu=blockbandwidths(op)
+    l = first(lu)
+    if padding # working on the tuple helps with type-stability
+        lu = lu .+ (0,l+diagblockshift(op))
+    end
+    data = BlockBandedMatrix{eltype(op)}(undef, Int[], Int[], lu)
+    CachedOperator(op,data,(0,0),domainspace(op),rangespace(op),lu .* (-1,1),padding)
 end