Deprecate generic stride implementation (#17812), allow AbstractArrays to use BLAS/LAPACK routines (#25247)

base/abstractarray.jl

@@ -219,46 +219,38 @@ julia> last([1; 2; 3; 4])
 last(a) = a[end]
 
 """
-    stride(A, k::Integer)
+    strides(A)
 
-Return the distance in memory (in number of elements) between adjacent elements in dimension `k`.
+Return a tuple of the memory strides in each dimension.
 
 # Examples
 ```jldoctest
 julia> A = ones(3,4,5);
 
-julia> stride(A,2)
-3
-
-julia> stride(A,3)
-12
+julia> strides(A)
+(1, 3, 12)
 ```
 """
-function stride(a::AbstractArray, i::Integer)
-    if i > ndims(a)
-        return length(a)
-    end
-    s = 1
-    for n = 1:(i-1)
-        s *= size(a, n)
-    end
-    return s
-end
+function strides end
 
 """
-    strides(A)
+    stride(A, k::Integer)
 
-Return a tuple of the memory strides in each dimension.
+Return the distance in memory (in number of elements) between adjacent elements in dimension `k`.
 
 # Examples
 ```jldoctest
 julia> A = ones(3,4,5);
 
-julia> strides(A)
-(1, 3, 12)
+julia> stride(A,2)
+3
+
+julia> stride(A,3)
+12
 ```
 """
-strides(A::AbstractArray) = size_to_strides(1, size(A)...)
+stride(A::AbstractArray, k::Integer) = strides(A)[k]
+
 @inline size_to_strides(s, d, sz...) = (s, size_to_strides(s * d, sz...)...)
 size_to_strides(s, d) = (s,)
 size_to_strides(s) = ()
@@ -2043,4 +2035,4 @@ function hash(a::AbstractArray{T}, h::UInt) where T
     end
     !isequal(x2, x1) && (h = hash(x2, h))
     return h
-end
+end

base/deprecated.jl

@@ -3489,6 +3489,19 @@ end
     @deprecate getq(F::Factorization) F.Q
 end
 
+# Issues #17812 Remove default stride implementation
+function strides(a::AbstractArray)
+    depwarn("""
+    `strides(a::AbstractArray)` is deprecated for general arrays.
+    Specialize `strides` for custom array types that have the appropriate representation in memory.
+    Warning: inappropriately implementing this method for an array type that does not use strided
+    storage may lead to incorrect results or segfaults.
+    """, :strides)
+    size_to_strides(1, size(a)...)
+end
+
+@deprecate substrides(s, parent, dim, I::Tuple) substrides(parent, strides(parent), I)
+
 # END 0.7 deprecations
 
 # BEGIN 1.0 deprecations

base/linalg/dense.jl

@@ -112,35 +112,21 @@ true
 isposdef(A::AbstractMatrix) = ishermitian(A) && isposdef(cholfact(Hermitian(A)))
 isposdef(x::Number) = imag(x)==0 && real(x) > 0
 
-"""
-    stride1(A) -> Int
-
-Return the distance between successive array elements
-in dimension 1 in units of element size.
-
-# Examples
-```jldoctest
-julia> A = [1,2,3,4]
-4-element Array{Int64,1}:
- 1
- 2
- 3
- 4
-
-julia> Base.LinAlg.stride1(A)
-1
-
-julia> B = view(A, 2:2:4)
-2-element view(::Array{Int64,1}, 2:2:4) with eltype Int64:
- 2
- 4
-
-julia> Base.LinAlg.stride1(B)
-2
-```
-"""
-stride1(x::Array) = 1
-stride1(x::StridedVector) = stride(x, 1)::Int
+# the definition of strides for Array{T,N} is tuple() if N = 0, otherwise it is
+# a tuple containing 1 and a cumulative product of the first N-1 sizes
+# this definition is also used for StridedReshapedArray and StridedReinterpretedArray
+# which have the same memory storage as Array
+function stride(a::Union{DenseArray,StridedReshapedArray,StridedReinterpretArray}, i::Int)
+    if i > ndims(a)
+        return length(a)
+    end
+    s = 1
+    for n = 1:(i-1)
+        s *= size(a, n)
+    end
+    return s
+end
+strides(a::Union{DenseArray,StridedReshapedArray,StridedReinterpretArray}) = size_to_strides(1, size(a)...)
 
 function norm(x::StridedVector{T}, rx::Union{UnitRange{TI},AbstractRange{TI}}) where {T<:BlasFloat,TI<:Integer}
     if minimum(rx) < 1 || maximum(rx) > length(x)