From 1550f85489d58fed54a4e41ce20f726ca478e1c7 Mon Sep 17 00:00:00 2001
From: Hiroshi Shinaoka <h.shinaoka@gmail.com>
Date: Mon, 30 Mar 2026 22:32:27 +0900
Subject: [PATCH] refactor: migrate TreeTCI evaluate to IndexId-based C API

Replace t4a_treetn_evaluate_batch with the new IndexId-based
t4a_treetn_all_site_index_ids + t4a_treetn_evaluate flow.
The new _evaluate_batch first queries index IDs and vertex names,
reorders values to match the index ordering, then calls evaluate.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
---
 src/TreeTCI.jl | 40 +++++++++++++++++++++++++++++++++++-----
 1 file changed, 35 insertions(+), 5 deletions(-)

diff --git a/src/TreeTCI.jl b/src/TreeTCI.jl
index 4f0e659..781221c 100644
--- a/src/TreeTCI.jl
+++ b/src/TreeTCI.jl
@@ -532,16 +532,46 @@ function evaluate(ttn::TreeTensorNetwork, batch::AbstractMatrix{<:Integer})
     return _evaluate_batch(ttn, flat, n_sites, n_points)
 end
 
-"""Internal: call C API batch evaluate and return typed results."""
+"""Internal: call C API evaluate using IndexId-based interface and return typed results."""
 function _evaluate_batch(ttn::TreeTensorNetwork, flat::Vector{Csize_t}, n_sites::Int, n_points::Int)
+    # Step 1: Query the number of site indices
+    n_indices_ref = Ref{Csize_t}(0)
+    C_API.check_status(ccall(
+        C_API._sym(:t4a_treetn_all_site_index_ids), Cint,
+        (Ptr{Cvoid}, Ptr{UInt64}, Ptr{Csize_t}, Csize_t, Ptr{Csize_t}),
+        ttn.handle, C_NULL, C_NULL, 0, n_indices_ref,
+    ))
+    n_indices = Int(n_indices_ref[])
+
+    # Step 2: Fetch index IDs and their vertex names
+    index_ids = Vector{UInt64}(undef, n_indices)
+    vertex_names = Vector{Csize_t}(undef, n_indices)
+    C_API.check_status(ccall(
+        C_API._sym(:t4a_treetn_all_site_index_ids), Cint,
+        (Ptr{Cvoid}, Ptr{UInt64}, Ptr{Csize_t}, Csize_t, Ptr{Csize_t}),
+        ttn.handle, index_ids, vertex_names, n_indices, n_indices_ref,
+    ))
+
+    # Step 3: Reorder flat values to match index_ids order.
+    # `flat` is laid out by site order (0, 1, …, n_sites-1) for each point.
+    # `vertex_names[i]` tells us which site (0-based) index i belongs to.
+    reordered = Vector{Csize_t}(undef, n_indices * n_points)
+    for p in 0:(n_points - 1)
+        for i in 1:n_indices
+            site = Int(vertex_names[i])  # 0-based site number
+            reordered[i + n_indices * p] = flat[site + 1 + n_sites * p]  # +1 for Julia 1-based
+        end
+    end
+
+    # Step 4: Call evaluate
     out_re = Vector{Cdouble}(undef, n_points)
     out_im = Vector{Cdouble}(undef, n_points)
     C_API.check_status(ccall(
-        C_API._sym(:t4a_treetn_evaluate_batch),
-        Cint,
-        (Ptr{Cvoid}, Ptr{Csize_t}, Csize_t, Csize_t, Ptr{Cdouble}, Ptr{Cdouble}),
-        ttn.handle, flat, Csize_t(n_sites), Csize_t(n_points), out_re, out_im,
+        C_API._sym(:t4a_treetn_evaluate), Cint,
+        (Ptr{Cvoid}, Ptr{UInt64}, Csize_t, Ptr{Csize_t}, Csize_t, Ptr{Cdouble}, Ptr{Cdouble}),
+        ttn.handle, index_ids, n_indices, reordered, n_points, out_re, out_im,
     ))
+
     # Detect if complex by checking if any imaginary part is nonzero
     if all(iszero, out_im)
         return out_re