Tensor fields are used in differential geometry, algebraic geometry, general relativity, in the analysis of stress and strain in materials, and in numerous applications in the physical sciences.
A tensor is essentially a list of numbers that can be in any dimension. A one-dimensional tensor is a line of numbers, a two-dimensional tensor is a square of numbers, and a three-dimensional tensor is a cube of numbers. A code-oriented way to think about it is a multi-dimensional array.
Tensor calculus has many applications in physics, engineering and computer science including elasticity, continuum mechanics, electromagnetism (see mathematical descriptions of the electromagnetic field), general relativity (see mathematics of general relativity), quantum field theory, and machine learning.
What is a tensor in a deep learning framework? Tensors are the data structure used by machine learning systems, and getting to know them is an essential skill you should build early on. A tensor is a container for numerical data. It is the way we store the information that we'll use within our system.
Tensors are simply mathematical objects that can be used to describe physical properties, just like scalars and vectors. In fact tensors are merely a generalisation of scalars and vectors; a scalar is a zero rank tensor, and a vector is a first rank tensor.
There are four main tensor type you can create: tf. Variable.
Start from Tensor -- from Wolfram MathWorld . You will need to carefully and slowly work your way through the Wolfram Mathworld page a number of times - but all the essentials are there. Use the links where needed.
In physics and mathematics, a tensor is an algebraic construct that is defined with respect to an n-dimensional linear space V. Like a vector, a tensor has geometric or physical meaning—it exists independent of choice of basis for V—but can yet be expressed with respect to a basis.
Tensors have become important in physics because they provide a concise mathematical framework for formulating and solving physics problems in areas such as mechanics (stress, elasticity, fluid mechanics, moment of inertia, ...), electrodynamics (electromagnetic tensor, Maxwell tensor, permittivity, magnetic ...
A tensor is a container which can house data in N dimensions. Often and erroneously used interchangeably with the matrix (which is specifically a 2-dimensional tensor), tensors are generalizations of matrices to N-dimensional space. Mathematically speaking, tensors are more than simply a data container, however.
Tensors use matrix to represent. It makes it so much easy to represent information in an array. Consider a image of some resolution Y x Y. The pixel data can of the images can be so easily represented in an array.
A tensor is a generalization of vectors and matrices and is easily understood as a multidimensional array. In the general case, an array of numbers arranged on a regular grid with a variable number of axes is known as a tensor.
A tensor field has a tensor corresponding to each point space. An example is the stress on a material, such as a construction beam in a bridge. Other examples of tensors include the strain tensor, the conductivity tensor, and the inertia tensor.
Tensors. In layman's terms, a tensor is a way of representing the data in deep learning. A tensor can be a 1-dimensional, a 2-dimensional, a 3-dimensional array, etc. You can think of a tensor as a multidimensional array.
PyTorch: Tensors A PyTorch Tensor is basically the same as a numpy array: it does not know anything about deep learning or computational graphs or gradients, and is just a generic n-dimensional array to be used for arbitrary numeric computation.
Tensors are multi-dimensional arrays with a uniform type (called a dtype ). You can see all supported dtypes at tf. dtypes. DType . If you're familiar with NumPy, tensors are (kind of) like np.
Essentially Tensor cores are processing units that accelerate the process of matrix multiplication. It is a technology developed by Nvidia for its high-end consumer and professional GPUs. It is currently available on limited GPUs like the ones belonging to the Geforce RTX, Quadro RTX, and Titan family. It can offer improved performance in AI, gaming, and content creation.
CUDA cores have been present on every single GPU developed by Nvidia in the past decade while Tensor Cores have recently been introduced. Tensor cores can compute a lot faster than the CUDA cores. CUDA cores perform one operation per clock cycle, whereas tensor cores can perform multiple operations per clock cycle.
But a Tensor is not a generalization of scalars or vectors, but rather, scalars and vectors are a generalization of a tensor. It can be considered as an extension of a matrix. Matrices are two-dimensional structures containing numbers, but a tensor is a multidimensional set of numbers.
Tensor calculus is, at its most basic, the set of rules and methods for manipulating and calculating with tensors. Tensors are mathematical objects which have an arbitrary (but defined) number of indices. For example, a nth-rank tensor in m-dimensional space will have n indices, and it will have m n components.
The rank of a tensor is the number of indices. The first three ranks (also called orders) for tensors (0, 1, 2) are scalar, vector, and matrix. Although these three are technically simple tensors, a mathematical object isn’t usually called a “tensor” unless the rank is 3 or above. There are exceptions. For example, rank 2 tensors (which can be represented by a matrix) hold special importance in many areas of engineering and physics, including electromagnetism, mechanics and quantum theory, because of their practicality; Therefore, instead of calling them matrices, you might hear them referred to as rank 2 tensors instead.
Rank 0 Tensor: The familiar scalar is the simplest tensor and is a rank 0 tensor. Scalars are just single real numbers like ½, 99 or -1002 that are used to measure magnitude (size). Scalars can technically be written as a one-unit array: [½], [99] or [-1002], but it’s not usual practice to do so. Rank 1 Tensor: Vectors are rank 1 tensors.
They have a rank of 2 because of the two-dimensional array: Rank 2 tensors are usually represented by uppercase bold letters, e.g. U, V, W. More formally, a rank 2 tensor is a mathematical operator that acts on one vector and generates another (Kelly, 2015). For example:
Matrices have two indices, which can be raised or lowered. Tensors have two or more indices, which can also be raised or lowered. For example, the following matrix can be written with index notation as A ij: There are many sub-conventions here, which are extremely important to follow. For example, the Kronecker delta.
One special property of tensor calculus is that when physics problems are framed in it they are independent of coordinate systems on the manifold, which makes for much neater problem solving than infinitesimal calculus.
Although it may seem an abstract field of mathematics, tensors actually make up a very good framework for formulating and solving many physics problems; in areas like fluid mechanics, electromagnetism, quantum field theory and elasticity. Albert Einstein used it to work out his theory of general relativity, and since then it has been included in mathematical physics curriculum.
Tensors are multi-dimensional arrays with a uniform type (called a dtype ).
Notice how the coordinates of the covector are also transformed by S, which makes the covector covariant
What is a tensor in Layman’s terms? The mathematical concept of a tensor could be broadly explained in this way. A scalar has the lowest dimensionality and is always 1x1. It can be thought of as a vector of length 1, or a 1x1 matrix. It is followed by a vector, where each element of that vector is a scalar.
How did tensors become important you may ask? Well, not without the help of one of the biggest names in science – Albert Einstein! Einstein developed and formulated the whole theory of ‘ general relativity ’ entirely in the language of tensors. Having done that, Einstein, while not a big fan of tensors himself, popularized tensor calculus to more than anyone else could ever have.
After this short intro to tensors, a question still remains – why TensorFlow is called like that and why does this framework need tensors at all.
Tensors are simply a generalization of the concepts we have seen so far. An object we haven’t seen is a tensor of rank 3. Its dimensions could be signified by k,m, and n, making it a KxMxN object. Such an object can be thought of as a collection of matrices.
A scalar has the lowest dimensionality and is always 1x1. It can be thought of as a vector of length 1, or a 1x1 matrix. It is followed by a vector, where each element of that vector is a scalar.
Nowadays, we can argue that the word ‘tensor’ is still a bit ‘underground’. You won’t hear it in high school. In fact, your Math teacher may have never heard of it . However, state-of-the-art machine learning frameworks are doubling down on tensors. The most prominent example being Google’s TensorFlow.
In terms of programming, a tensor is no different than a NumPy ndarray. And in fact, tensors can be stored in ndarrays and that’s how we often deal with the issue.
Tensors are typically defined by their coordinate transformation properties. The transformation properties of tensors can be understood by realizing that the physical quantities they represent must appear in certain ways to different observers with different points of view.
Writing vector or tensor equations in generalized coordinate systems is a process familiar to students in classical mechanics. In order to successfully write such equations and use them to solve problems or to build models, the characteristics of generalized coordinate systems must be understood. Recall that in a generalized coordinate system:
The permeability µ is a tensor of rank 2. Remember that B and H are both vectors, but they now differ from one another in both magnitude and direction.
i.e., while the position vector itself is not a tensor, the difference between any two position vectors is a tensor of rank 1! Similarly, for any position vectors V and V*, dV = dV*; i.e., the differential of the position vector is a tensor of rank 1.
A Tensor is a generalization of Vectors and Matrices to higher dimensions.
The number of simultaneous directions a tensor can have in a N -dimensional space, is called the Rank of the tensor. The rank is denoted R. A Scalar is a single number. R = 0. A Vector is an array of numbers.
In linear algebra, the most simple math object is the Scalar :
A Matrix is a 2-dimensional array. R = 2.
Programming tensor operations in JavaScript, can easily become a spaghetti of loops.
Another example of a physical tensor is the moment of inertia. In Chapter 18 of Volume I we saw that a solid object rotating about a fixed axis has an angular momentum L proportional to the angular velocity ω, and we called the proportionality factor I, the moment of inertia: L = Iω. For an arbitrarily shaped object, the moment of inertia depends on its orientation with respect to the axis of rotation. For instance, a rectangular block will have different moments about each of its three orthogonal axes. Now angular velocity ω and angular momentum L are both vectors. For rotations about one of the axes of symmetry, they are parallel. But if the moment of inertia is different for the three principal axes, then ω and L are, in general, not in the same direction (see Fig. 31–4 ). They are related in a way analogous to the relation between E and P. In general, we must write Lx = Ixxωx + Ixyωy + Ixzωz, Ly = Iyxωx + Iyyωy + Iyzωz, Lz = Izxωx + Izyωy + Izzωz. The nine coefficients Iij are called the tensor of inertia. Following the analogy with the polarization, the kinetic energy for any angular momentum must be some quadratic form in the components ωx , ωy, and ωz : KE = 1 2 ∑ ij Iijωiωj. We can use the energy to define the ellipsoid of inertia. Also, energy arguments can be used to show that the tensor is symmetric—that Iij = Iji.
The mathematics of tensors is particularly useful for describing properties of substances which vary in direction —although that’s only one example of their use. Since most of you are not going to become physicists, but are going to go into the real world, where things depend severely upon direction, sooner or later you will need to use tensors. In order not to leave anything out, we are going to describe tensors, although not in great detail. We want the feeling that our treatment of physics is complete. For example, our electrodynamics is complete—as complete as any electricity and magnetism course, even a graduate course. Our mechanics is not complete, because we studied mechanics when you didn’t have a high level of mathematical sophistication, and we were not able to discuss subjects like the principle of least action, or Lagrangians, or Hamiltonians, and so on, which are more elegant ways of describing mechanics. Except for general relativity, however, we do have the complete laws of mechanics. Our electricity and magnetism is complete, and a lot of other things are quite complete. The quantum mechanics, naturally, will not be—we have to leave something for the future. But you should at least know what a tensor is.
The tensor αij should really be called a “tensor of second rank,” because it has two indexes. A vector—with one index—is a tensor of the first rank, and a scalar—with no index—is a tensor of zero rank.
The symmetric tensors we have described so far arose as coefficients in relating one vector to another. We would like to look now at a tensor which has a different physical significance—the tensor of stress. Suppose we have a solid object with various forces on it. We say that there are various “stresses” inside, by which we mean that there are internal forces between neighboring parts of the material. We have talked a little about such stresses in a two-dimensional case when we considered the surface tension in a stretched diaphragm in Section 12–3. We will now see that the internal forces in the material of a three-dimensional body can be described in terms of a tensor.
The subscripts of the polarization tensor range over three possible values—they are tensors in three dimensions. The mathematicians consider tensors in four, five, or more dimensions. We have already used a four-dimensional tensor Fμν in our relativistic description of the electromagnetic field (Chapter 26 ).
Now the ellipsoid of polarizability must share the internal geometric symmetries of the crystal. For example, a triclinic crystal has low symmetry—the ellipsoid of polarizability will have unequal axes, and its orientation will not, in general, be aligned with the crystal axes.
The energy density uP is a number independent of the choice of axes, so it is a scalar. A tensor has then the property that when it is summed over one index (with a vector), it gives a new vector; and when it is summed over both indexes (with two vectors), it gives a scalar.