WIP: exploratory branch for fast array views

base/array/view.jl

@@ -0,0 +1,90 @@
+importall Base
+
+isdefined(:ArrayView) || immutable ArrayView{T,n,m} <: AbstractArray{T,n}
+    array::Array{T,m}
+    sizes::NTuple{n,Int}
+    strides::NTuple{n,Int}
+    origin::Int
+    magic::NTuple{n,Int}
+    coefs::NTuple{n,Int}
+end
+
+size(v::ArrayView) = v.sizes
+size(v::ArrayView, i::Int) = v.sizes[i]
+ndims{T,n}(v::ArrayView{T,n}) = n
+eltype(v::ArrayView) = eltype(v.array)
+
+function v2a{n}(strides::NTuple{n,Int}, o::Int, I::NTuple{n,Int})
+    @inbounds for k = 1:n
+        o += (I[k]-1)*strides[k]
+    end
+    return o
+end
+
+function v2a{n}(magic::NTuple{n,Int}, coefs::NTuple{n,Int}, o::Int, i::Int)
+    i -= 1
+    o += i*coefs[1]
+    @inbounds for k = 2:n
+        o += (magic[k]*i>>>32)*coefs[k]
+    end
+    return o
+end
+
+v2a{T,n}(v::ArrayView{T,n}, I::NTuple{n,Int}) = v2a(v.strides, v.origin, I)
+v2a{T,n}(v::ArrayView{T,n}, i::Int) = v2a(v.magic, v.coefs, v.origin, i)
+
+getindex(v::ArrayView, i::Int) = @inbounds return v.array[v2a(v,i)]
+getindex(v::ArrayView, I::Int...) = @inbounds return v.array[v2a(v,I)]
+setindex!(v::ArrayView, x, i::Int) = (@inbounds v.array[v2a(v,i)] = x)
+setindex!(v::ArrayView, x, I::Int...) = (@inbounds v.array[v2a(v,I)] = x)
+
+function ArrayView{n}(a::Array, R::NTuple{n,Ranges})
+    prod = origin = 1
+    strides = ntuple(n) do k
+        origin += prod*(first(R[k])-1)
+        stride = prod*step(R[k])
+        prod *= size(a,k)
+        return stride
+    end
+    sizes = map(length,R)
+    prod = 1
+    magic = ntuple(n) do k
+        m = div(1<<32+prod-1,prod)
+        prod *= sizes[k]
+        return m
+    end
+    coefs = ntuple(n) do k
+        k == 1 ? strides[k] : strides[k]-sizes[k-1]*strides[k-1]
+    end
+    ArrayView(a,sizes,strides,origin,magic,coefs)
+end
+
+function repeated_linear_indexing(a,cap=0.01)
+    n = 0
+    time = 0.0
+    total = zero(eltype(a))
+    while time < cap
+        time += @elapsed for i = 1:length(a)
+            total += a[i]
+        end
+        n += 1
+    end
+    total, time/n
+end
+
+function benchmark(z=100000,n=10,m=10)
+    results = Array(Float64,n,m,3)
+    for d = 1:n, x = 1:m
+        S = [ iround(3z^(1/d)+1) for _=1:d ]
+        A = rand(S...)
+        R = map(s->2:3:s-1,size(A))
+        a = A[R...]
+        v = ArrayView(A,R)
+        s = sub(A,R)
+        @show S, size(a), length(a)
+        results[d,x,1] = repeated_linear_indexing(a)[2]
+        results[d,x,2] = repeated_linear_indexing(v)[2]
+        results[d,x,3] = repeated_linear_indexing(s)[2]
+    end
+    return results
+end

src/intrinsics.cpp

@@ -743,37 +743,13 @@ static Value *emit_intrinsic(intrinsic f, jl_value_t **args, size_t nargs,
         return t == T_void ? x : y;
 
     Value *fy;
-    Value *den;
-    Value *typemin;
     switch (f) {
     HANDLE(neg_int,1) return builder.CreateSub(ConstantInt::get(t, 0), JL_INT(x));
     HANDLE(add_int,2) return builder.CreateAdd(JL_INT(x), JL_INT(y));
     HANDLE(sub_int,2) return builder.CreateSub(JL_INT(x), JL_INT(y));
     HANDLE(mul_int,2) return builder.CreateMul(JL_INT(x), JL_INT(y));
-    HANDLE(sdiv_int,2)
-        den = JL_INT(y);
-        x = JL_INT(x);
-
-        typemin = builder.CreateShl(ConstantInt::get(t,1),
-                                    x->getType()->getPrimitiveSizeInBits()-1);
-        raise_exception_unless(builder.
-                               CreateAnd(builder.
-                                         CreateICmpNE(den, ConstantInt::get(t,0)),
-                                         builder.
-                                         CreateOr(builder.
-                                                  CreateICmpNE(den,
-                                                               ConstantInt::get(t,-1,true)),
-                                                  builder.CreateICmpNE(x, typemin))),
-                               jldiverr_var, ctx);
-
-        return builder.CreateSDiv(x, den);
-    HANDLE(udiv_int,2)
-        den = JL_INT(y);
-        raise_exception_unless(builder.CreateICmpNE(den,
-                                                    ConstantInt::get(t,0)),
-                               jldiverr_var, ctx);
-        return builder.CreateUDiv(JL_INT(x), den);
-
+    HANDLE(sdiv_int,2) return builder.CreateSDiv(JL_INT(x), JL_INT(y));
+    HANDLE(udiv_int,2) return builder.CreateUDiv(JL_INT(x), JL_INT(y));
     HANDLE(srem_int,2) return builder.CreateSRem(JL_INT(x), JL_INT(y));
     HANDLE(urem_int,2) return builder.CreateURem(JL_INT(x), JL_INT(y));
     HANDLE(smod_int,2)