move BlockPermutedDiagonalAlgorithm and update docstring

Author: lkdvos

src/factorizations/svd.jl

@@ -3,23 +3,6 @@ using MatrixAlgebraKit:
   MatrixAlgebraKit, check_input, default_svd_algorithm, svd_compact!, svd_full!
 using TypeParameterAccessors: realtype
 
-"""
-    BlockPermutedDiagonalAlgorithm(A::MatrixAlgebraKit.AbstractAlgorithm)
-  
-A wrapper for `MatrixAlgebraKit.AbstractAlgorithm` that implements the wrapped algorithm on
-a block-by-block basis, which is possible if the input matrix is a block-diagonal matrix or
-a block permuted block-diagonal matrix.
-"""
-struct BlockPermutedDiagonalAlgorithm{F} <: MatrixAlgebraKit.AbstractAlgorithm
-  falg::F
-end
-function block_algorithm(alg::BlockPermutedDiagonalAlgorithm, a::AbstractMatrix)
-  return block_algorithm(alg, typeof(a))
-end
-function block_algorithm(alg::BlockPermutedDiagonalAlgorithm, A::Type{<:AbstractMatrix})
-  return alg.falg(A)
-end
-
 function MatrixAlgebraKit.default_svd_algorithm(
   ::Type{<:AbstractBlockSparseMatrix}; kwargs...
 )

src/factorizations/utility.jl

@@ -1,3 +1,5 @@
+using MatrixAlgebraKit: MatrixAlgebraKit
+
 function infimum(r1::AbstractUnitRange, r2::AbstractUnitRange)
   (isone(first(r1)) && isone(first(r2))) ||
     throw(ArgumentError("infimum only defined for ranges starting at 1"))
@@ -50,3 +52,23 @@ function isblockdiagonal(A::AbstractBlockSparseMatrix)
   # this is guaranteed as long as eachblockstoredindex is unique, which we assume
   return true
 end
+
+"""
+    BlockPermutedDiagonalAlgorithm([f]) <: MatrixAlgebraKit.AbstractAlgorithm
+
+Type for handling algorithms on a block-by-block basis, which is possible for
+block-diagonal or block-permuted-diagonal input matrices.
+Additionally this wrapper may take a function that, given the input type of the blocks,
+returns the actual algorithm that will be used. This can be leveraged to allow for different
+algorithms for each block.
+"""
+struct BlockPermutedDiagonalAlgorithm{F} <: MatrixAlgebraKit.AbstractAlgorithm
+  falg::F
+end
+
+function block_algorithm(alg::BlockPermutedDiagonalAlgorithm, a::AbstractMatrix)
+  return block_algorithm(alg, typeof(a))
+end
+function block_algorithm(alg::BlockPermutedDiagonalAlgorithm, A::Type{<:AbstractMatrix})
+  return alg.falg(A)
+end