From: Guido Kanschat <dr.guido.kanschat@gmail.com>
Date: Mon, 15 Jan 2001 09:57:34 +0000 (+0000)
Subject: scalar product of tensors
X-Git-Tag: v8.0.0~19823
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=fcba3a54abfcfba801577d6bd2a100509768be12;p=dealii.git

scalar product of tensors


git-svn-id: https://svn.dealii.org/trunk@3656 0785d39b-7218-0410-832d-ea1e28bc413d
---

diff --git a/deal.II/base/include/base/tensor.h b/deal.II/base/include/base/tensor.h
index 750bfc1b0a..92486dabe6 100644
--- a/deal.II/base/include/base/tensor.h
+++ b/deal.II/base/include/base/tensor.h
@@ -397,6 +397,25 @@ DeclException1 (ExcInvalidTensorIndex,
 		<< "Invalid tensor index " << arg1);
 
 
+/**
+ * Contract a tensor of rank 1 with a tensor of rank 1. The result is
+ * @p{sum_j src1[j] src2[j]}.
+ *
+ * @author Guido Kanschat, 2000
+ */
+template <int dim>
+inline
+double contract (const Tensor<1,dim> &src1,
+		 const Tensor<1,dim> &src2)
+{
+  double res = 0.;
+  for (unsigned int i=0; i<dim; ++i)
+    res += src1[i] * src2[i];
+
+  return res;
+}
+
+
 /**
  * Contract a tensor of rank 2 with a tensor of rank 1. The result is
  * @p{dest[i] = sum_j src1[i][j] src2[j]}.