SHEEP (symbolic computation system)
Encyclopedia
SHEEP is one of the earliest interactive symbolic computation systems
. It is specialized for computations with tensor
s, and was designed for the needs of researchers working with general relativity
and other theories involving extensive tensor calculus computations.
SHEEP is an open source
freeware
package (copyrighted, but free for educational and research use).
The name "SHEEP" is pun on the Lisp Algebraic Manipulator
or LAM on which SHEEP is based. The package was written by Inge Frick, using earlier work by Ian Cohen and Ray d'Inverno, who had written ALAM - Atlas LISP Algebraic Manipulation in earlier (designed in 1970). SHEEP was an interactive computer package whereas LAM and ALAM were batch processing
languages.
Jan E. Åman wrote an important package in SHEEP to carry out the Cartan-Karlhede algorithm
. A more recent version of SHEEP, written by Jim Skea, runs under Cambridge Lisp, which is also used for REDUCE.
Computer algebra system
A computer algebra system is a software program that facilitates symbolic mathematics. The core functionality of a CAS is manipulation of mathematical expressions in symbolic form.-Symbolic manipulations:...
. It is specialized for computations with tensor
Tensor
Tensors are geometric objects that describe linear relations between vectors, scalars, and other tensors. Elementary examples include the dot product, the cross product, and linear maps. Vectors and scalars themselves are also tensors. A tensor can be represented as a multi-dimensional array of...
s, and was designed for the needs of researchers working with general relativity
General relativity
General relativity or the general theory of relativity is the geometric theory of gravitation published by Albert Einstein in 1916. It is the current description of gravitation in modern physics...
and other theories involving extensive tensor calculus computations.
SHEEP is an open source
Open source
The term open source describes practices in production and development that promote access to the end product's source materials. Some consider open source a philosophy, others consider it a pragmatic methodology...
freeware
Freeware
Freeware is computer software that is available for use at no cost or for an optional fee, but usually with one or more restricted usage rights. Freeware is in contrast to commercial software, which is typically sold for profit, but might be distributed for a business or commercial purpose in the...
package (copyrighted, but free for educational and research use).
The name "SHEEP" is pun on the Lisp Algebraic Manipulator
Lisp Algebraic Manipulator
The Lisp Algebraic Manipulator was created by Ray d'Inverno, who had written Atlas LISP Algebraic Manipulation . LAM later became the basis for the interactive computer package SHEEP....
or LAM on which SHEEP is based. The package was written by Inge Frick, using earlier work by Ian Cohen and Ray d'Inverno, who had written ALAM - Atlas LISP Algebraic Manipulation in earlier (designed in 1970). SHEEP was an interactive computer package whereas LAM and ALAM were batch processing
Batch processing
Batch processing is execution of a series of programs on a computer without manual intervention.Batch jobs are set up so they can be run to completion without manual intervention, so all input data is preselected through scripts or command-line parameters...
languages.
Jan E. Åman wrote an important package in SHEEP to carry out the Cartan-Karlhede algorithm
Cartan-Karlhede algorithm
One of the most fundamental problems of Riemannian geometry is this: given two Riemannian manifolds of the same dimension, how can one tell if they are locally isometric? This question was addressed by Elwin Christoffel, and completely solved by Élie Cartan using his exterior calculus with his...
. A more recent version of SHEEP, written by Jim Skea, runs under Cambridge Lisp, which is also used for REDUCE.
External links
- SHEEP download directory at Queen Mary, University of LondonQueen Mary, University of LondonQueen Mary, University of London is a public research university located in London, United Kingdom and a constituent college of the federal University of London...
- Some sources of info on Sheep
- Review article by M.A.H.MacCallum in "Workshop on Dynamical Spacetimes and Numerical Relativity" edited by Joan M. Centrella