From 1348826661c33095c19393372a977076977f750b Mon Sep 17 00:00:00 2001
From: dance858 <danielcederberg1@gmail.com>
Date: Tue, 13 Oct 2026 06:20:43 +0200
Subject: [PATCH] convolve: own the convolution-matrix helpers

conv_matrix_fill_sparsity / conv_matrix_fill_values build the Toeplitz matrix
T(a) of convolve's 1D full convolution. convolve is their only caller, so
they move here from sparsediff_linalg as static helpers (verbatim copies),
and convolve no longer includes csr_kernels.h. This lets the library drop
them from its public API.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
---
 src/atoms/affine/convolve.c | 34 +++++++++++++++++++++++++++++++++-
 1 file changed, 33 insertions(+), 1 deletion(-)

diff --git a/src/atoms/affine/convolve.c b/src/atoms/affine/convolve.c
index 2b58d1f..61c91c7 100644
--- a/src/atoms/affine/convolve.c
+++ b/src/atoms/affine/convolve.c
@@ -17,7 +17,6 @@
  */
 #include "atoms/affine.h"
 #include "sparsediff_linalg/CSR_matrix.h"
-#include "sparsediff_linalg/csr_kernels.h"
 #include "sparsediff_linalg/matmul.h"
 #include "sparsediff_linalg/matrix.h"
 #include "sparsediff_linalg/tracked_alloc.h"
@@ -32,6 +31,39 @@
  * (m+n-1) x n Toeplitz/convolution matrix with T(a)[k, j] = a[k-j] when
  * 0 <= k-j < m. */
 
+/* Fill T_csr's row pointers and column indices for the 1D full-convolution
+   Toeplitz matrix T(a), sized (m+n-1) x n with m*n nonzeros. Values (x) are
+   not written; call conv_matrix_fill_values to populate them. */
+static void conv_matrix_fill_sparsity(CSR_matrix *T_csr, int m, int n)
+{
+    int nnz = 0;
+    for (int r = 0; r < T_csr->m; r++)
+    {
+        T_csr->p[r] = nnz;
+        int col_lo = r - m + 1 > 0 ? r - m + 1 : 0;
+        int col_hi = r < n - 1 ? r : n - 1;
+        for (int col = col_lo; col <= col_hi; col++)
+        {
+            T_csr->i[nnz] = col;
+            nnz++;
+        }
+    }
+    T_csr->p[T_csr->m] = nnz;
+}
+
+/* Overwrite T_csr->x from kernel a, using the sparsity already written by
+   conv_matrix_fill_sparsity. T[r, col] = a[r - col]. */
+static void conv_matrix_fill_values(CSR_matrix *T_csr, const double *a)
+{
+    for (int r = 0; r < T_csr->m; r++)
+    {
+        for (int k = T_csr->p[r]; k < T_csr->p[r + 1]; k++)
+        {
+            T_csr->x[k] = a[r - T_csr->i[k]];
+        }
+    }
+}
+
 static void forward(expr *node, const double *u)
 {
     expr *child = node->left;