From 0b5c9d6993caa78bf9a8e63f0e562aca7019d378 Mon Sep 17 00:00:00 2001
From: Jaron Kent-Dobias <jaron@kent-dobias.com>
Date: Sun, 18 Aug 2024 13:43:42 +0200
Subject: Added linear model.

---
 topology.cpp | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/topology.cpp b/topology.cpp
index e89e3eb..6650ea6 100644
--- a/topology.cpp
+++ b/topology.cpp
@@ -60,7 +60,7 @@ public:
 
   virtual std::tuple<Vector, Matrix, Tensor> H_∂H_∂∂H(const Vector& x) const {
     Tensor t(M, N, N);
-    Tensor ∂∂H = t.setConstant(0);
+    Tensor ∂∂H = t.setZero();
     Matrix ∂H  = Matrix::Zero(M, N);
     Vector H   = Vector::Zero(M);
     return {H, ∂H, ∂∂H};
@@ -143,6 +143,26 @@ public:
   }
 };
 
+class ExtensiveLinear : public ConstraintModel {
+private:
+  Matrix A;
+
+public:
+  ExtensiveLinear(unsigned N, unsigned M, Real E, Rng& r) : ConstraintModel(N, M, E, r), A(M, N) {
+    for (Real& Aij : A.reshaped()) {
+      Aij = r.variate<Real, std::normal_distribution>(0, sqrt(1.0 / N));
+    }
+  }
+
+  std::tuple<Vector, Matrix, Tensor> H_∂H_∂∂H(const Vector& x) const override {
+    Tensor ∂∂H(M, N, N);
+    ∂∂H.setZero();
+    Matrix ∂H = A;
+    Vector  H = A * x;
+    return {H, ∂H, ∂∂H};
+  }
+};
+
 class ExtensiveQuadratic : public ConstraintModel {
 private:
   Tensor J;
-- 
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