From: Martin Kronbichler <martin.kronbichler@uni-a.de>
Date: Mon, 14 Aug 2023 15:30:20 +0000 (+0200)
Subject: Add changelog
X-Git-Tag: relicensing~592^2
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=refs%2Fpull%2F15875%2Fhead;p=dealii.git

Add changelog
---

diff --git a/doc/news/changes/minor/20230814Kronbichler b/doc/news/changes/minor/20230814Kronbichler
new file mode 100644
index 0000000000..e1499eff0a
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+++ b/doc/news/changes/minor/20230814Kronbichler
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+Improved: deal.II now has a flag DEAL_II_USE_VECTORIZATION_GATHER to control
+the use of gather/scatter instructions on the x86 architecture. On a wide
+range of Intel hardware with microcode mitigation for the Intel Gather Data
+Speculation (GDS, aka Downfall) side channel vulnerability, in particular,
+server processors of the Broadwell, Skylake, Cascade Lake, and Ice Lake
+families released between 2015 and 2021, these instructions can be much slower
+than scalar loads. While the default behavior of deal.II is to aggressively
+enable these instructions in the intrinsics-class VectorizedArray, the new
+variable can be used to disable their use if deemed to give better
+performance.
+<br>
+(Martin Kronbichler, Matthias Maier, 2023/08/14)