Mark param_source subtrees dirty before the owning atom re-evaluates them

A param_source subtree is evaluated by the owning atom's gated recursion,
not the main forward walk, so expr_set_needs_refresh never reaches nodes
inside a composite source. Gated nodes there (promote, nested mults,
cached matmul coefficients) kept serving values cached at build time
after problem_update_params: p*A @ x and quad_form(x, g*Sig) both solved
with the original parameter values on every re-solve.

Fix: each source-owning atom marks its subtree dirty at the moment it is
about to re-evaluate it (one expr_set_needs_refresh call per atom, gated
on the flag the main walker already sets). Nested gated levels recurse
for free. No struct or walker changes; no behavior change for one-shot
solves or bare-parameter sources.

Tests: tests/problem/test_param_source_refresh.h pins the three failing
shapes (composite matmul coefficient, composite quad matrix, two nested
gated levels); each fails without the fix and passes with it.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: Transurgeon

src/atoms/affine/convolve.c

@@ -39,6 +39,9 @@ static void forward(expr *node, const double *u)
 
     if (cnode->base.needs_parameter_refresh)
     {
+        /* Composite sources hold gated nodes of their own (promote, nested
+           mults): mark the whole side subtree before re-evaluating it. */
+        expr_set_needs_refresh(cnode->param_source);
         cnode->param_source->forward(cnode->param_source, NULL);
         /* refresh the convolution matrix values if it exists (necessary to check
            for null in case someone calls forward before initializing the jacobian,

src/atoms/affine/kron.c

@@ -44,6 +44,9 @@ static void refresh_param_values(kron_expr *knode)
         return;
     }
 
+    /* Composite sources hold gated nodes of their own (promote, nested
+       mults): mark the whole side subtree before re-evaluating it. */
+    expr_set_needs_refresh(knode->param_source);
     knode->param_source->forward(knode->param_source, NULL);
     knode->base.needs_parameter_refresh = false;
 }

src/atoms/affine/left_matmul.c

@@ -70,6 +70,9 @@ static void forward(expr *node, const double *u)
     /* call forward on param_source if it exists and needs refresh */
     if (lnode->param_source != NULL && lnode->base.needs_parameter_refresh)
     {
+        /* Composite sources hold gated nodes of their own (promote, nested
+           mults): mark the whole side subtree before re-evaluating it. */
+        expr_set_needs_refresh(lnode->param_source);
         lnode->param_source->forward(lnode->param_source, NULL);
     }
 

src/atoms/affine/scalar_mult.c

@@ -35,6 +35,9 @@ static void forward(expr *node, const double *u)
        its values) */
     if (snode->base.needs_parameter_refresh)
     {
+        /* Composite sources hold gated nodes of their own (promote, nested
+           mults): mark the whole side subtree before re-evaluating it. */
+        expr_set_needs_refresh(snode->param_source);
         snode->param_source->forward(snode->param_source, NULL);
         snode->base.needs_parameter_refresh = false;
     }

src/atoms/affine/vector_mult.c

@@ -35,6 +35,9 @@ static void forward(expr *node, const double *u)
        its values) */
     if (vnode->base.needs_parameter_refresh)
     {
+        /* Composite sources hold gated nodes of their own (promote, nested
+           mults): mark the whole side subtree before re-evaluating it. */
+        expr_set_needs_refresh(vnode->param_source);
         vnode->param_source->forward(vnode->param_source, NULL);
         vnode->base.needs_parameter_refresh = false;
     }

src/atoms/other/quad_form.c

@@ -55,6 +55,9 @@ static void forward(expr *node, const double *u)
     /* refresh Q from the parameter if needed (no-op on the constant/sparse path) */
     if (qnode->param_source != NULL && node->needs_parameter_refresh)
     {
+        /* Composite sources hold gated nodes of their own (promote, nested
+           mults): mark the whole side subtree before re-evaluating it. */
+        expr_set_needs_refresh(qnode->param_source);
         qnode->param_source->forward(qnode->param_source, NULL);
     }
     refresh_param_values_qf(qnode);

tests/all_tests.c

@@ -60,6 +60,7 @@
 #include "old-code/test_old_permuted_dense.h"
 #include "problem/test_param_broadcast.h"
 #include "problem/test_param_prob.h"
+#include "problem/test_param_source_refresh.h"
 #include "problem/test_problem.h"
 #include "utils/test_COO_matrix.h"
 #include "utils/test_alloc_overflow.h"
@@ -550,6 +551,11 @@ int main(void)
     mu_run_test(test_param_scalar_mult_problem_with_constant, tests_run);
     mu_run_test(test_param_convolve_problem, tests_run);
 
+    printf("\n--- Composite param_source Refresh Tests ---\n");
+    mu_run_test(test_composite_source_left_matmul, tests_run);
+    mu_run_test(test_composite_source_quad_form, tests_run);
+    mu_run_test(test_composite_source_nested_gates, tests_run);
+
     printf("\n--- Parameter + Broadcast Tests ---\n");
     mu_run_test(test_constant_broadcast_vector_mult, tests_run);
     mu_run_test(test_constant_promote_vector_mult, tests_run);

tests/problem/test_param_source_refresh.h

@@ -0,0 +1,197 @@
+#ifndef TEST_PARAM_SOURCE_REFRESH_H
+#define TEST_PARAM_SOURCE_REFRESH_H
+
+/* Composite param_source refresh across problem_update_params.
+ *
+ * A param_source subtree is evaluated by the owning atom's gated recursion,
+ * not the main forward walk, so gated nodes *inside* a composite source
+ * (promote, nested mults, cached matmuls) are only re-evaluated if the owner
+ * marks the subtree before forwarding it. These tests pin the shapes that
+ * served stale values before that mark existed:
+ *
+ *   1. left_matmul whose coefficient is p (.) A     ("(p*A) @ x")
+ *   2. quad_form whose matrix is g (.) Sigma        ("quad_form(x, g*Sig)")
+ *   3. two gated levels: coefficient (c*p) (.) A    ("((2p)*A) @ x")
+ *
+ * Bare-parameter sources are covered by test_param_prob.h; these are the
+ * composite counterparts.
+ */
+
+#include <math.h>
+#include <stdio.h>
+
+#include "atoms/affine.h"
+#include "atoms/non_elementwise_full_dom.h"
+#include "expr.h"
+#include "minunit.h"
+#include "problem.h"
+#include "subexpr.h"
+#include "test_helpers.h"
+
+/* (p * A) @ x: the elementwise product of a promoted scalar parameter with a
+   constant matrix feeds left_matmul as its param_source. */
+const char *test_composite_source_left_matmul(void)
+{
+    int n = 2;
+
+    expr *x = new_variable(2, 1, 0, n);
+    expr *objective = new_sum(x, -1);
+
+    double theta[1] = {2.0};
+    expr *p = new_parameter(1, 1, 0, n, theta);
+    /* column-major A = [[1,2],[3,4]] */
+    double A_vals[4] = {1.0, 3.0, 2.0, 4.0};
+    expr *A_const = new_parameter(2, 2, PARAM_FIXED, n, A_vals);
+    expr *coeff = new_vector_mult(new_promote(p, 2, 2), A_const);
+
+    expr *constraint = new_left_matmul_dense(coeff, x, 2, 2, NULL);
+    expr *constraints[1] = {constraint};
+    problem *prob = new_problem(objective, constraints, 1, false);
+
+    expr *param_nodes[1] = {p};
+    problem_register_params(prob, param_nodes, 1);
+    problem_init_derivatives(prob);
+
+    double x_vals[2] = {1.0, 2.0};
+    int Ap[3] = {0, 2, 4};
+    int Ai[4] = {0, 1, 0, 1};
+
+    /* p = 2: effective A is 2*A, so A@x = 2*[5,11] */
+    problem_constraint_forward(prob, x_vals);
+    problem_jacobian(prob);
+    double constrs[2] = {10.0, 22.0};
+    double Ax[4] = {2.0, 4.0, 6.0, 8.0};
+    mu_assert("initial vals fail",
+              cmp_double_array(prob->constraint_values, constrs, 2));
+    mu_assert("initial jac fail", cmp_double_array(prob->jacobian->x, Ax, 4));
+    mu_assert("rows fail", cmp_int_array(prob->jacobian->p, Ap, 3));
+    mu_assert("cols fail", cmp_int_array(prob->jacobian->i, Ai, 4));
+
+    /* p = 10: the promote inside the source must re-evaluate */
+    theta[0] = 10.0;
+    problem_update_params(prob, theta);
+    problem_constraint_forward(prob, x_vals);
+    problem_jacobian(prob);
+    constrs[0] = 50.0;
+    constrs[1] = 110.0;
+    Ax[0] = 10.0;
+    Ax[1] = 20.0;
+    Ax[2] = 30.0;
+    Ax[3] = 40.0;
+    mu_assert("stale constraint values after update",
+              cmp_double_array(prob->constraint_values, constrs, 2));
+    mu_assert("stale jacobian values after update",
+              cmp_double_array(prob->jacobian->x, Ax, 4));
+
+    free_problem(prob);
+
+    return 0;
+}
+
+/* quad_form(x, g * Sigma): the scaled constant matrix feeds quad_form's
+   cached Q through its param_source. */
+const char *test_composite_source_quad_form(void)
+{
+    int n = 2;
+
+    expr *x = new_variable(2, 1, 0, n);
+
+    double theta[1] = {1.0};
+    expr *g = new_parameter(1, 1, 0, n, theta);
+    /* Sigma = diag(2, 3); symmetric, so major order is irrelevant */
+    double S_vals[4] = {2.0, 0.0, 0.0, 3.0};
+    expr *S_const = new_parameter(2, 2, PARAM_FIXED, n, S_vals);
+    expr *Q_src = new_vector_mult(new_promote(g, 2, 2), S_const);
+
+    expr *objective = new_quad_form_dense(x, 2, NULL, Q_src);
+    problem *prob = new_problem(objective, NULL, 0, false);
+
+    expr *param_nodes[1] = {g};
+    problem_register_params(prob, param_nodes, 1);
+    problem_init_derivatives(prob);
+
+    double x_vals[2] = {1.0, 2.0};
+
+    /* g = 1: x'(g Sigma)x = 2*1 + 3*4 = 14; gradient 2(g Sigma)x = [4, 12] */
+    double obj_val = problem_objective_forward(prob, x_vals);
+    problem_gradient(prob);
+    double grad[2] = {4.0, 12.0};
+    mu_assert("initial obj fail", fabs(obj_val - 14.0) < 1e-10);
+    mu_assert("initial grad fail", cmp_double_array(prob->gradient_values, grad, 2));
+
+    /* g = 5: Q's cached values must be re-copied from the re-evaluated source */
+    theta[0] = 5.0;
+    problem_update_params(prob, theta);
+    obj_val = problem_objective_forward(prob, x_vals);
+    problem_gradient(prob);
+    grad[0] = 20.0;
+    grad[1] = 60.0;
+    mu_assert("stale objective after update", fabs(obj_val - 70.0) < 1e-10);
+    mu_assert("stale gradient after update",
+              cmp_double_array(prob->gradient_values, grad, 2));
+
+    free_problem(prob);
+
+    return 0;
+}
+
+/* ((c * p) * A) @ x: two gated levels inside the source (scalar_mult under
+   promote under vector_mult) — the mark must recurse through all of them. */
+const char *test_composite_source_nested_gates(void)
+{
+    int n = 2;
+
+    expr *x = new_variable(2, 1, 0, n);
+    expr *objective = new_sum(x, -1);
+
+    double theta[1] = {1.0};
+    expr *p = new_parameter(1, 1, 0, n, theta);
+    double c_val = 2.0;
+    expr *c_const = new_parameter(1, 1, PARAM_FIXED, n, &c_val);
+    expr *scaled = new_scalar_mult(p, c_const); /* = c * p, a gated node */
+    /* column-major A = [[1,2],[3,4]] */
+    double A_vals[4] = {1.0, 3.0, 2.0, 4.0};
+    expr *A_const = new_parameter(2, 2, PARAM_FIXED, n, A_vals);
+    expr *coeff = new_vector_mult(new_promote(scaled, 2, 2), A_const);
+
+    expr *constraint = new_left_matmul_dense(coeff, x, 2, 2, NULL);
+    expr *constraints[1] = {constraint};
+    problem *prob = new_problem(objective, constraints, 1, false);
+
+    expr *param_nodes[1] = {p};
+    problem_register_params(prob, param_nodes, 1);
+    problem_init_derivatives(prob);
+
+    double x_vals[2] = {1.0, 2.0};
+
+    /* p = 1: effective A is 2*A */
+    problem_constraint_forward(prob, x_vals);
+    problem_jacobian(prob);
+    double constrs[2] = {10.0, 22.0};
+    double Ax[4] = {2.0, 4.0, 6.0, 8.0};
+    mu_assert("initial vals fail",
+              cmp_double_array(prob->constraint_values, constrs, 2));
+    mu_assert("initial jac fail", cmp_double_array(prob->jacobian->x, Ax, 4));
+
+    /* p = 5: effective A is 10*A; both gated levels must re-evaluate */
+    theta[0] = 5.0;
+    problem_update_params(prob, theta);
+    problem_constraint_forward(prob, x_vals);
+    problem_jacobian(prob);
+    constrs[0] = 50.0;
+    constrs[1] = 110.0;
+    Ax[0] = 10.0;
+    Ax[1] = 20.0;
+    Ax[2] = 30.0;
+    Ax[3] = 40.0;
+    mu_assert("stale constraint values after update",
+              cmp_double_array(prob->constraint_values, constrs, 2));
+    mu_assert("stale jacobian values after update",
+              cmp_double_array(prob->jacobian->x, Ax, 4));
+
+    free_problem(prob);
+
+    return 0;
+}
+
+#endif /* TEST_PARAM_SOURCE_REFRESH_H */