                              IDAS
                     Release 3.1.0, Feb 2019
                           Radu Serban 
           Center for Applied Scientific Computing, LLNL


IDAS is a package for the solution of differential-algebraic equation (DAE) 
systems with sensitivity analysis capabilities (both forward and adjoint modes). 
It is written in ANSI standard C.

IDAS can be used both on serial and parallel computers.  The main
difference is in the NVECTOR module of vector kernels.  The desired
version is obtained when compiling the example files by linking the
appropriate library of NVECTOR kernels.  In the parallel versions,
communication between processors is done with MPI, with OpenMP, 
or with Pthreads.

When used with the serial NVECTOR module, IDAS provides both direct 
(dense and band) linear solvers and preconditioned Krylov (iterative) 
linear solvers. Three different iterative solvers are available: scaled 
preconditioned GMRES (SPGMR), scaled preconditioned BiCGStab (SPBCG), and 
scaled preconditioned TFQMR (SPTFQMR). When IDAS is used with the parallel 
NVECTOR module, only the Krylov linear solvers are available.  For the 
latter case, in addition to the basic solver, the IDA package also contains 
a preconditioner module called IDABBDPRE, which provides a band-block-diagonal 
preconditioner.

IDAS is part of a software family called SUNDIALS: SUite of Nonlinear and 
DIfferential/ALgebraic equation Solvers [3].  This suite consists of CVODE, 
CVODES, ARkode, IDA, IDAS, and KINSOL.  The directory structure of the 
package supplied reflects this family relationship.

Several examples problem programs are included, covering both serial
and parallel cases, both small and large problem sizes, and both
linear and nonlinear problems.

The notes below provide the location of documentation, directions for the 
installation of the IDAS package, and relevant references. Following that 
is a brief history of revisions to the package.


A. Documentation
----------------

/sundials/doc/idas/ contains PDF files for the IDAS User Guide [1] (idas_guide.pdf)
and the IDAS Examples [2] (idas_examples.pdf) documents.


B. Installation
---------------

For basic installation instructions see the file /sundials/INSTALL_GUIDE.pdf. 
For complete installation instructions see the "Installation Procedure"
chapter in the IDAS User Guide.


C. References
-------------

[1] R. Serban, C. Petra,and A. C. Hindmarsh,  "User Documentation for IDAS v1.3.0," 
    LLNL technical report UCRL-SM-234051, March 2016.

[2] R. Serban and A.C. Hindmarsh, "Example Programs for IDAS v1.3.0," 
    LLNL technical report LLNL-TR-437091, March 2016.

[3] A. C. Hindmarsh, P. N. Brown, K. E. Grant, S. L. Lee, R. Serban, 
    D. E. Shumaker, and C. S. Woodward, "SUNDIALS, Suite of Nonlinear and 
    Differential/Algebraic Equation Solvers," ACM Trans. Math. Softw., 
    31(3), pp. 363-396, 2005.


D. Releases
-----------

v. 3.1.0       - Feb. 2019
v. 3.0.2       - Jan. 2019
v. 3.0.1       - Dec. 2018
v. 3.0.0       - Dec. 2018
v. 2.2.1       - Oct. 2018
v. 2.2.0       - Sep. 2018
v. 2.1.2       - Jul. 2018
v. 2.1.1       - May  2018
v. 2.1.0       - Nov. 2017
v. 2.0.0       - Sep. 2017
v. 1.3.0       - Sep. 2016
v. 1.2.2       - Aug. 2015
v. 1.2.1       - Mar. 2015
v. 1.2.0       - Mar. 2015
v. 1.1.0       - Mar. 2012
v. 1.0.0       - May  2009
