From: Denis Davydov <davydden@gmail.com>
Date: Tue, 13 Feb 2018 18:32:08 +0000 (+0100)
Subject: return immediately if a==0 in p::d::Vector::add(a,V)
X-Git-Tag: v9.0.0-rc1~440^2
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=refs%2Fpull%2F5893%2Fhead;p=dealii.git

return immediately if a==0 in p::d::Vector::add(a,V)
---

diff --git a/include/deal.II/lac/la_parallel_vector.templates.h b/include/deal.II/lac/la_parallel_vector.templates.h
index 6cb5794d83..ea7369deee 100644
--- a/include/deal.II/lac/la_parallel_vector.templates.h
+++ b/include/deal.II/lac/la_parallel_vector.templates.h
@@ -849,6 +849,10 @@ namespace LinearAlgebra
       AssertIsFinite(a);
       AssertDimension (local_size(), v.local_size());
 
+      // nothing to do if a is zero
+      if (a == Number(0.))
+        return;
+
       internal::VectorOperations::Vectorization_add_av<Number> vector_add(values.get(), v.values.get(), a);
       internal::VectorOperations::parallel_for(vector_add, 0, partitioner->local_size(),
                                                thread_loop_partitioner);