Clean up and simplify optimization interface

src/algorithms/ctmrg/projectors.jl

@@ -57,13 +57,11 @@
 end
 
 # TODO: add `LinearAlgebra.cond` to TensorKit
-# Compute condition number σ_max / σ_min for diagonal singular value TensorMap
+# Compute condition number smax / smin for diagonal singular value TensorMap
 function _condition_number(S::AbstractTensorMap)
-    # Take maximal condition number over all blocks
-    return maximum(blocks(S)) do (_, b)
-        b_diag = diag(b)
-        return maximum(b_diag) / minimum(b_diag)
-    end
+    smax = maximum(first, last.(values(blocks(S))))
+    smin = minimum(last, last.(values(blocks(S))))
+    return smax / smin
 end
 @non_differentiable _condition_number(S::AbstractTensorMap)
 
@@ -77,7 +75,7 @@
     # SVD half-infinite environment
     halfinf = half_infinite_environment(enlarged_corners...)
     svd_alg = svd_algorithm(alg, coordinate)
     U, S, V, truncation_error = PEPSKit.tsvd!(halfinf, svd_alg; trunc=alg.trscheme)
 
     # Check for degenerate singular values
     Zygote.isderiving() && ignore_derivatives() do
@@ -88,9 +86,9 @@
     end
 
     P_left, P_right = contract_projectors(U, S, V, enlarged_corners...)
     truncation_error /= norm(S)
     condition_number = @ignore_derivatives(_condition_number(S))
     return (P_left, P_right), (; truncation_error, condition_number, U, S, V)
 end
 function compute_projector(enlarged_corners, coordinate, alg::FullInfiniteProjector)
     halfinf_left = half_infinite_environment(enlarged_corners[1], enlarged_corners[2])
@@ -99,7 +97,7 @@
     # SVD full-infinite environment
     fullinf = full_infinite_environment(halfinf_left, halfinf_right)
     svd_alg = svd_algorithm(alg, coordinate)
     U, S, V, truncation_error = PEPSKit.tsvd!(fullinf, svd_alg; trunc=alg.trscheme)
 
     # Check for degenerate singular values
     Zygote.isderiving() && ignore_derivatives() do
@@ -110,6 +108,6 @@
     end
 
     P_left, P_right = contract_projectors(U, S, V, halfinf_left, halfinf_right)
     condition_number = @ignore_derivatives(_condition_number(S))
     return (P_left, P_right), (; truncation_error, condition_number, U, S, V)
 end