From 8d1b316765587c5eb2cd5262e61220a9fa8e24a8 Mon Sep 17 00:00:00 2001
From: Oleksandr Pavlyk <21087696+oleksandr-pavlyk@users.noreply.github.com>
Date: Tue, 5 May 2026 07:44:25 -0500
Subject: [PATCH] Require at least 5 samples to begin estimating noise level

---
 nvbench/detail/stdrel_criterion.cxx | 22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)

diff --git a/nvbench/detail/stdrel_criterion.cxx b/nvbench/detail/stdrel_criterion.cxx
index f03409f..6fc42b3 100644
--- a/nvbench/detail/stdrel_criterion.cxx
+++ b/nvbench/detail/stdrel_criterion.cxx
@@ -41,16 +41,20 @@ void stdrel_criterion::do_add_measurement(nvbench::float64_t measurement)
   m_total_cuda_time += measurement;
   m_cuda_times.push_back(measurement);
 
-  // Compute convergence statistics using CUDA timings:
-  const auto [cuda_first_quartile, cuda_median, cuda_third_quartile] =
-    nvbench::detail::statistics::compute_percentiles(m_cuda_times.cbegin(),
-                                                     m_cuda_times.cend(),
-                                                     {25, 50, 75});
-  const auto cuda_noise = (cuda_third_quartile - cuda_first_quartile) / cuda_median;
-
-  if (std::isfinite(cuda_noise))
+  // require at least 5 samples for meaningful noise estimate
+  if (m_total_samples > 4)
   {
-    m_noise_tracker.push_back(cuda_noise);
+    // Compute convergence statistics using CUDA timings:
+    const auto [cuda_first_quartile, cuda_median, cuda_third_quartile] =
+      nvbench::detail::statistics::compute_percentiles(m_cuda_times.cbegin(),
+                                                       m_cuda_times.cend(),
+                                                       {25, 50, 75});
+    const auto cuda_noise = (cuda_third_quartile - cuda_first_quartile) / cuda_median;
+
+    if (std::isfinite(cuda_noise))
+    {
+      m_noise_tracker.push_back(cuda_noise);
+    }
   }
 }