Tensor<1, dim> initialization

[A.Z Ihsan]

Hi there, 

just a small question. 

suppose we want to construct a rank-1 tensor in 3 dim with values (1, 1, 0) : 

Tensor<1, 3> b();

i read a documentation we can use array_type as a parameter construction, but still i aml confused how to use it. 

any idea how to use it?

BR,

Ihsan

[Matthias Maier]

On Sun, Jan 5, 2020, at 07:15 CST, "A.Z Ihsan" <jurna...@gmail.com> wrote:

> Tensor<1, 3> b();

If you write this then you declare a function "b" returning a
Tensor<1,3>. Declare the tensor without the parentheses:

Tensor<1, 3> b;

You can access individual elements of the tensor via operator[]:

b[0] = 1;
b[1] = 1;
b[2] = 0;

And you can do meaningful mathematical tensor operations. Including,
scaling a tensor

auto a = 5. * b;

Adding two tensors together:

auto c = a + b;

Taking the inner product:

auto k = a * b;

etc.

Best,
Matthias

[A.Z Ihsan]

Thank you Matthias. 

It works perfectly!

BR, 

Ihsan

[Wolfgang Bangerth]

On 1/5/20 6:15 AM, A.Z Ihsan wrote:
> just a small question.
>
> suppose we want to construct a rank-1 tensor in 3 dim with values (1, 1, 0) :
> Tensor<1, 3> b();

In addition the other answer, you can also initialize the tensor like this:
Tensor<1,3> t2({1., 1., 0.});
or
Tensor<1,3> t4{{1., 1., 0.}};

Best
W.

--
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Wolfgang Bangerth email: bang...@colostate.edu
www: http://www.math.colostate.edu/~bangerth/