Kothar Computing Documentation

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https://docs.kotharcomputing.com

Documentation for the Kothar platform, featuring the Forge automation environment, the Workshop for numerical experiments, and the Aleph language. Includes comprehensive library references for the standard library, tensor operations (RealTensor, ComplexTensor), and the AlephExpectation testing framework, as well as details on the Python SDK and REST API.

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What's inside Kothar

  1. Overview of the Cauchy distribution

    The Cauchy distribution represents the ratio of two normal distributions. It is defined by a location parameter a (default 0.0) and a half-width half-maximum parameter b (default 1.0).

    The probability density function is defined as: f(x | a, b) = (bπ(1 + ((x-a)/b)²))⁻¹

  2. Overview of PiecewiseLinear random distribution

    The PiecewiseLinear distribution (inheriting from Distribution) returns random real numbers distributed linearly within specified intervals and densities.

    • Default Intervals: [0.0, 1.0]
    • Default Densities: [1.0]

    The probability density function $f(x | I, w)$ for a value $x$ where $I_k \leq x < I_{k+1}$ is defined by the linear interpolation of densities $w$ over the intervals $I$.

  3. Overview of the Slice type

    The Slice object (inheriting from Object) represents a range specification for indexing operations. It defines a start index, stop index, and step size, allowing for flexible data access patterns such as reverse iteration, skipping elements, and extracting subsequences from arrays, strings, and other indexable containers.
  4. Overview of the PauliString class

    The PauliString class represents a Pauli string and its complex coefficient using a numerically efficient bitstring representation. It uses bit logic to perform operations faster than OperatorProducts or OperatorSums.

    Internally, each Pauli string is represented by a complex coefficient and two integers, xbits and zbits. The mapping for Pauli operators is:

    • 00: Identity (I)
    • 10: X
    • 01: Z
    • 11: Y

    The class automatically handles the phase accrued during the multiplication of different terms.

  5. Overview of NumpyFile for .npy and .npz files

    The NumpyFile class represents a handle to a NumPy file. It supports two formats: .npy files, which are used for a single direct array value, and .npz files, which are used for archives containing multiple named arrays.
    # Write a single array to a .npy file
    NumpyFile("values.npy", "w").write([1.0, 2.0, 3.0])
    
    # Read a .npy file as a list of reals
    var values = NumpyFile("values.npy").read(as_real | as_list)
    
    # Write a named array to a .npz archive
    NumpyFile("archive.npz", "w").write("samples", [1, 2, 3])
  6. Overview of The Forge scientific computing environment

    The Forge is an integrated environment for scientific computing that combines dedicated editors, tailored programming languages (such as Aleph), and high-performance libraries. It is designed for physicists, chemists, and engineers to prototype models, run simulations, and publish results. The ecosystem consists of the Workshop web application for authoring and visualization, managed agents for routing computations to hardware (CPUs, GPUs, QPUs), and REST endpoints for automation.
  7. Overview of PiecewiseConstant random distribution

    The PiecewiseConstant distribution returns random real numbers uniformly distributed within specified intervals (default: [0.0, 1.0]) and densities (default: [1.0]).

    The probability density function is defined as:

    $f(x | I, w) = \frac{w_k}{(I_{k+1} - I_k)\sum_k w_k}$ for $I_k \leq x < I_{k+1}$

    Where $I_k$ are the elements of the intervals parameter and $w_k$ are the elements of the densities parameter.

  8. Overview of the ChiSquared distribution

    The ChiSquared distribution models the distribution of the sum of squares of n independent standard normal variables (with a default value of 1.0). Its probability density function is defined as: f(x | n) = x^((n/2)-1) * e^(-x/2) / (Gamma(n/2) * 2^(n/2)). It inherits from the Distribution base class.
  9. Overview of Stochastic Series Expansion (SSE) in Aleph

    The Stochastic Series Expansion (SSE) is a Markov chain Monte Carlo formalism used to estimate expectation values of quantum systems in thermal equilibrium at an inverse temperature $\beta$. It works by performing a Taylor series expansion of the partition function and sampling over a local basis and an 'operator string' (a product of Hamiltonian terms or identity matrices) of a fixed cutoff length $M$. A critical constraint of SSE is that all vertex weights must be positive to avoid the sign problem.
  10. Overview of the real type

    The real type represents floating-point numbers with fractional parts, adhering to IEEE 754 double-precision semantics.

    Key characteristics:

    • Precision: Approximately 15-17 decimal digits.
    • Range: Minimum positive normalized value is 2.2250738585072014e-308; maximum value is 1.7976931348623157e308.
    • Subnormal numbers: Supported down to approximately 5e-324.
    • Behavior: Arithmetic may introduce small rounding errors. Overflow results in Infinity or -Infinity.
  11. Overview of Lattice geometries and parameters

    The Lattice class represents a crystal lattice consisting of a Bravais lattice and an atomic basis. When using predefined geometries, parameters typically follow the convention where a, b, and c represent side lengths, and theta and phi represent angles.

    GeometryParameters
    squarea (intercell spacing)
    rectangulara (intercell spacing dim 11), b (intercell spacing dim 22)
    triangulara (intercell spacing)
    obliquea (intercell spacing dim 11), b (side length dim 22), theta (angle between primitive vectors)
    honeycomba (intersite spacing)
    chain(Supported geometry)