DDRIV

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C                    D D R I V   P A C K A G E
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C
C   D. K. KAHANER, NATIONAL BUREAU OF STANDARDS, AND
C   C. D. SUTHERLAND, LOS ALAMOS SCIENTIFIC LABORATORY, OCTOBER 22, 1980
C
C  I.  C H O O S I N G  T H E  C O R R E C T  R O U T I N E ............
C
C      SDRIV
C      DDRIV
C      CDRIV
C             THESE ARE THE GENERIC NAMES OF THREE PACKAGES FOR
C             SOLVING ORDINARY DIFFERENTIAL EQUATIONS WITH INITIAL
C             CONDITIONS.
C              SDRIV: FOR SINGLE PRECISION DIFFERENTIAL EQUATIONS
C              DDRIV: FOR DOUBLE PRECISION DIFFERENTIAL EQUATIONS
C              CDRIV: FOR COMPLEX PRECISION DIFFERENTIAL EQUATIONS WITH
C                      A REAL INDEPENDENT VARIABLE
C
C    AS AN AID IN SELECTING THE PROPER PROGRAM, THE FOLLOWING IS A
C    DISCUSSION OF THE IMPORTANT OPTIONS OR RESTRICTIONS ASSOCIATED
C    WITH EACH PROGRAM..
C
C      A. DDRIV1 SHOULD BE TRIED FIRST FOR THOSE ROUTINE PROBLEMS WITH
C         NO MORE THAN 200 DIFFERENTIAL EQUATIONS.  INTERNALLY THIS
C         ROUTINE HAS TWO IMPORTANT TECHNICAL DEFAULTS..
C           1. NUMERICAL APPROXIMATION OF THE JACOBIAN MATRIX OF THE
C              RIGHT HAND SIDE IS USED.
C           2. THE STIFF SOLVER OPTION IS USED.
C         MOST USERS OF DDRIV1 SHOULD NOT HAVE TO CONCERN THEMSELVES
C         WITH THESE DETAILS.
C
C      B. DDRIV2 SHOULD BE CONSIDERED FOR THOSE PROBLEMS FOR WHICH
C         DDRIV1 IS INADEQUATE.  IT PROVIDES TWO IMPORTANT ADDITIONAL
C         OPTIONS..
C           1. THE NONSTIFF EQUATION SOLVER (AS WELL AS THE STIFF
C              SOLVER) IS AVAILABLE.
C           2. THE ROOT FINDING OPTION IS AVAILABLE.
C         INTERNALLY THIS ROUTINE ALSO DEFAULTS TO THE NUMERICAL
C         APPROXIMATION OF THE JACOBIAN MATRIX OF THE RIGHT HAND SIDE.
C
C      C. DDRIV3 IS THE MOST FLEXIBLE, AND HENCE THE MOST COMPLEX,
C         OF THE PROGRAMS.  ITS IMPORTANT FEATURES INCLUDE..
C           1. THE ABILITY TO EXPLOIT BAND STRUCTURE IN THE JACOBIAN
C              MATRIX.
C           2. THE ABILITY TO SOLVE SOME IMPLICIT DIFFERENTIAL
C              EQUATIONS, I.E., THOSE HAVING THE FORM..
C                   A(Y,T)*DY/DT = F(Y,T).
C           3. THE OPTION OF INTEGRATING IN THE ONE STEP MODE.
C           4. THE OPTION OF ALLOWING THE USER TO PROVIDE A ROUTINE
C              WHICH COMPUTES THE ANALYTIC JACOBIAN MATRIX OF THE
C              RIGHT HAND SIDE.
C           5. THE OPTION OF ALLOWING THE USER TO PROVIDE A ROUTINE
C              WHICH DOES ALL THE MATRIX ALGEBRA ASSOCIATED WITH
C              CORRECTIONS TO THE SOLUTION COMPONENTS.
C         ADDITIONALLY, DDRIV3 HAS THE SAME FEATURES AS DDRIV1,2.
C