rework gesdvd! to accept two copies of input but only modify one

Author: lkdvos

src/implementations/svd.jl

@@ -134,7 +134,7 @@ function svd_full!(A::AbstractMatrix, USVᴴ, alg::LAPACK_SVDAlgorithm)
     elseif alg isa LAPACK_SafeDivideAndConquer
         isempty(alg_kwargs) ||
             throw(ArgumentError("invalid keyword arguments for LAPACK_SafeDivideAndConquer"))
-        YALAPACK.gesdvd!(A, view(S, 1:minmn, 1), U, Vᴴ)
+        YALAPACK.gesdvd!(A, copy_input(svd_full, A), view(S, 1:minmn, 1), U, Vᴴ)
     elseif alg isa LAPACK_Bisection
         throw(ArgumentError("LAPACK_Bisection is not supported for full SVD"))
     elseif alg isa LAPACK_Jacobi
@@ -179,7 +179,7 @@ function svd_compact!(A::AbstractMatrix, USVᴴ, alg::LAPACK_SVDAlgorithm)
     elseif alg isa LAPACK_SafeDivideAndConquer
         isempty(alg_kwargs) ||
             throw(ArgumentError("invalid keyword arguments for LAPACK_SafeDivideAndConquer"))
-        YALAPACK.gesdvd!(A, diagview(S), U, Vᴴ)
+        YALAPACK.gesdvd!(A, copy_input(svd_compact, A), diagview(S), U, Vᴴ)
     elseif alg isa LAPACK_Bisection
         YALAPACK.gesvdx!(A, diagview(S), U, Vᴴ; alg_kwargs...)
     elseif alg isa LAPACK_Jacobi
@@ -218,7 +218,7 @@ function svd_vals!(A::AbstractMatrix, S, alg::LAPACK_SVDAlgorithm)
     elseif alg isa LAPACK_SafeDivideAndConquer
         isempty(alg_kwargs) ||
             throw(ArgumentError("invalid keyword arguments for LAPACK_SafeDivideAndConquer"))
-        YALAPACK.gesdvd!(A, S, U, Vᴴ)
+        YALAPACK.gesdvd!(A, copy_input(svd_vals, A), S, U, Vᴴ)
     elseif alg isa LAPACK_Bisection
         YALAPACK.gesvdx!(A, S, U, Vᴴ; alg_kwargs...)
     elseif alg isa LAPACK_Jacobi

src/yalapack.jl

@@ -2169,14 +2169,12 @@ for (gesvd, gesdd, gesvdx, gejsv, gesvj, elty, relty) in
             end
             return (S, U, Vᴴ), info[]
         end
-        #! format: off
         function gesdvd!( # SafeSVD implementation
-                A::AbstractMatrix{$elty},
+                A::AbstractMatrix{$elty}, Ac::AbstractMatrix{$elty} = copy(A), # only modifies Ac!
                 S::AbstractVector{$relty} = similar(A, $relty, min(size(A)...)),
                 U::AbstractMatrix{$elty} = similar(A, $elty, size(A, 1), min(size(A)...)),
                 Vᴴ::AbstractMatrix{$elty} = similar(A, $elty, min(size(A)...), size(A, 2))
             )
-            #! format: on
             require_one_based_indexing(A, U, Vᴴ, S)
             chkstride1(A, U, Vᴴ, S)
             m, n = size(A)
@@ -2192,10 +2190,10 @@ for (gesvd, gesdd, gesvdx, gejsv, gesvj, elty, relty) in
             else
                 rwork = nothing
             end
-            Ac = copy(A)
             (S, U, Vᴴ), info = _gesdd_body!(Ac, S, U, Vᴴ, work, rwork)
             if info > 0
-                (S, U, Vᴴ), info = _gesvd_body!(A, S, U, Vᴴ, work, rwork)
+                copy!(Ac, A)
+                (S, U, Vᴴ), info = _gesvd_body!(Ac, S, U, Vᴴ, work, rwork)
             end
             chklapackerror(info)
             return S, U, Vᴴ