From: Steinar H. Gunderson <sgunderson@bigfoot.com>
Date: Sat, 4 Aug 2018 19:20:26 +0000 (+0200)
Subject: Update the SOR comment about twinned buffering.
X-Git-Tag: 1.8.0~76^2~135
X-Git-Url: https://git.sesse.net/?a=commitdiff_plain;h=ab3b838374200c9050ac57c53d3c183fbb58a7be;p=nageru

Update the SOR comment about twinned buffering.
---

diff --git a/sor.frag b/sor.frag
index e1f86bb..ef431d3 100644
--- a/sor.frag
+++ b/sor.frag
@@ -45,8 +45,9 @@ void main()
 	// just immediately throws away half of the warp, but it helps convergence
 	// a _lot_ (rough testing indicates that five iterations of SOR is as good
 	// as ~50 iterations of Jacobi). We could probably do better by reorganizing
-	// the data into two-values-per-pixel, so-called “twinning buffering”,
-	// but it makes for rather annoying code in the rest of the pipeline.
+	// the data into two-values-per-pixel, so-called “twinned buffering”;
+	// seemingly, it helps Haswell by ~15% on the SOR code, but GTX 950 not at all
+	// (at least not on 720p). Presumably the latter is already bandwidth bound.
 	int color = int(round(element_sum_idx)) & 1;
 	if (color != phase) discard;