From c7e75dcad3787ff56c5ee33fc59d437ca84dbb92 Mon Sep 17 00:00:00 2001
From: Jaron Kent-Dobias <jaron@kent-dobias.com>
Date: Sat, 10 May 2025 15:35:19 -0300
Subject: Force monotonicity of C and R

---
 log-fourier_integrator.cpp | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/log-fourier_integrator.cpp b/log-fourier_integrator.cpp
index 04dccfd..2d7d1f9 100644
--- a/log-fourier_integrator.cpp
+++ b/log-fourier_integrator.cpp
@@ -145,7 +145,22 @@ int main(int argc, char* argv[]) {
       std::vector<Real> Rₜ₊₁ = fft.inverse(Ȓₜ₊₁);
       std::vector<Real> Cₜ₊₁ = fft.inverse(Ĉₜ₊₁);
 
-      Real C₀ = (Cₜ₊₁[0] + Cₜ₊₁[1]) / 2;
+      Real Cmin = Cₜ₊₁[N-1];
+      for (unsigned i = 0; i < N; i++) {
+        if (Cₜ₊₁[N-1-i] > Cmin) {
+          Cmin = Cₜ₊₁[N-1-i];
+        }
+        Cₜ₊₁[N-1-i] = Cmin;
+      }
+      Real Rmin = Rₜ₊₁[N-1];
+      for (unsigned i = 0; i < N; i++) {
+        if (Rₜ₊₁[N-1-i] > Rmin) {
+          Rmin = Rₜ₊₁[N-1-i];
+        }
+        Rₜ₊₁[N-1-i] = Rmin;
+      }
+
+      Real C₀ = Cₜ₊₁[0];
 
       μₜ *= pow(tanh(C₀-1)+1, x);
 
-- 
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