This section contains links to a variety of mathematical topics, methods algorithms and software. Much of the material is unique or not readily available elsewhere.

The contents of the navigation subsections are:

- LINEAR — a collection of linear solvers and ports from other languages,
- NON-LINEAR — non-linear solvers, including Newton's and Broyden's,
- INTEGRATION — integrators, including QUADPACK and double exponential,
- POLY ROOTS — advanced polynomial root-finders, original methods and ports,
- XBCD-MATH — an extended precision BCD math package for calculator use.

The polynomial root finders will find all real and complex roots of real polynomials and include a port of the Jenkins-Traub method from FORTRAN to C++. Some of the C/C++ code are translations of the original FORTRAN code found in Zhang and Jin, "Computation of Special Functions", John Wiley and Sons, 1996.

Here are some links to specific topics in this section.

- An extended precision scientific math package optimized for calculator applications,
- A collection of recursive-descent expression evaluators for real and complex, double and extended precision applications,
- High performance 32-bit assembler language linear algebra routines, FFTs, etc.
- Polynomial root finders for double precision and complex numeric types,
- A precision Gamma function in Intel assembler language based on the Lanczos method,
- A collection of numerical integrators using Gaussian integration and double exponential methods,

The following source files supporting the Gamma function are available in these links:

- Precision, high-performance Gamma function for real arguments in assembler language (TASM), based on Lanczos method.
- Gamma function in C/C++ for real arguments, ported from Zhang and Jin,
- Log Gamma function in C++ for real arguments, ported from Zhang and Jin.
- Gamma and Log Gamma function in C++ for complex arguments, ported from Zhang and Jin.
- Incomplete Gamma function (several types), ported from Zhang and Jin.

Routines for computing the psi function for real and complex arguments are provided here.

The file ell_ag.cpp is a port of the
subroutine for the integrals Elliptic 'F' (1st kind) and Elliptic 'E' (2nd kind)
from the FORTRAN code in the book by Zhang and Jin cited in the next paragraph.
This code uses a method based on the *arithmetic-geometric mean. *Several
minor changes have been made, including the change in the argument from degrees
to radians, and re-ordering of the input parameters so that the argument comes
first, followed by the modulus.

This archive contains a port of the Bessel functions in "Computation of Special Functions", by Zhang and Jin, John Wiley and Sons, 1996. The files include C++ versions of the algorithms and a header file. Please consult the above cited publication for details on input and output naming conventions and function usage.

Individual files are available in the following links:

- Bessjy -- Bessel functions J
_{n}and Y_{n}for real argument and integer or real order. - Bessik -- Modified Bessel function I
_{n}and K_{n}for real argument and integer or real order. - CBessjy -- Bessel functions J
_{v}and Y_{v}for real or complex arguments and real order. - CBessik -- Modified Bessel functions I
_{v}and K_{v}for complex arguments and real order.

This extended precision, high performance math library supports logs, exponentials, trig and inverse trig functions, hyperbolic and inverse hyperbolic functions, as well as generalized factorial and the gamma function. Details and downloads are in XBCD.

The following executables deal with prime numbers in the limited range of 32-bit unsigned integers. Because of the restricted range, they should only be considered as tools for benchmarking the accuracy or performance of similar algorithms.

This executable, *cbprimepi.exe,
*counts the number of primes which
are less than or equal to a given positive integer in the range from 0 to 4,294,967,295.
The restricted range is not be sufficient for general use
or research, but the implementation is modest in
size and reasonably fast. It is undemanding of system resources as it does not use recursion or
allocate additional external memory. The time required to compute the prime
count is displayed for benchmarking. The timer employs the Pentium CPU time
stamp counter so the application will not work on other platforms. No feature
testing is used, so make sure you have the proper hardware before running this
executable.

*cbprime.exe* finds the n^{th}
prime number, given the number 'n'. Again, the range of valid prime numbers is
restricted to those expressible by an unsigned 32-bit integer. The number of primes in
this range is such that the range of 'n' is from 1 to 203280221. This application uses a
method similar to that in the prime count program above. It is reasonably fast
and is not resource intensive. A benchmarking timer is included. The timer
employs the Pentium CPU time stamp counter so the application will not work on
other platforms. No feature testing is used, so make sure you have the proper
hardware before running this executable.

The following applications are not meant to be competitive with advanced factoring machines dealing with RSA sized integers. They should be considered only as 'toy' applications with severely limited range, suitable for benchmarking the accuracy or performance of similar programs.

This program *xfactor.exe* will
decompose any positive integer smaller than 2^32 into its prime factors.
Although the algorithm is only a simple variant of a sieve, its benchmark
timings reveal excellent performance over the range supported. Timing for each
invocation is indicated along with the list of prime factors. NOTE: This
executable requires the Pentium time stamp counter for benchmarking. Elapsed
time is
computed for a 2GHz Pentium and must be scaled for other platforms. No feature
checking is provided, so make certain your system includes the proper hardware.

A variant of Fermat's method for factoring integers is described in Knuth
as Algorithm C. It is implemented here as *xfermat.exe*
and in this executable support for integers larger than 32-bits is provided. It will
generally not outperform xfactor.exe for number smaller than 2^32 and only
outputs one pair of (not necessarily prime) factors, but for larger numbers it is
efficient and can be invoked recursively on any factors found to completely decompose a
composite integer into its prime factors. NOTE: This executable requires the Pentium time stamp counter
for benchmarking. Elapsed time is
computed for a 2Ghz Pentium and must be scaled for other
platforms. No feature checking is provided, so make certain your system
includes the proper hardware.

Source code for an extremely simple and compact version of *Knuth's Algorithm
C is available in *fermat.cpp*.
This code does not include benchmark timing capability, but its performance is much
better over the range of 32-bit integers than either of the above programs.

*Donald E. Knuth, "The Art of Computer Programming", *Vol.
2 / Seminumerical Algorithms, *2nd Ed., Addison-Wesley Publishing Co., 1980,
p.371.