fixed gfortran 11.1 crash in test case

minor changes and readme updates

Author: jacobwilliams

README.md

@@ -193,16 +193,16 @@ fpm test --profile release
 To generate the documentation using [ford](https://github.com/Fortran-FOSS-Programmers/ford), run:
 
 ```
-  FoBis.py rule --execute makedoc -f ddeabm.fobis
+  ford ddeabm.md
 ```
 
 ## Documentation
 
-The latest API documentation can be found [here](http://jacobwilliams.github.io/ddeabm/). This was generated from the source code using [FORD](https://github.com/Fortran-FOSS-Programmers/ford) (note that the included `build.sh` script will also generate these files).
+The latest API documentation can be found [here](http://jacobwilliams.github.io/ddeabm/). This was generated from the source code using [FORD](https://github.com/Fortran-FOSS-Programmers/ford).
 
 ## License
 
-The ddeabm source code and related files and documentation are distributed under a permissive free software [license](https://github.com/jacobwilliams/ddeabm/blob/master/LICENSE) (BSD-style).  The original DDEABM Fortran 77 code is [public domain](http://www.netlib.org/slatec/guide).
+The DDEABM source code and related files and documentation are distributed under a permissive free software [license](https://github.com/jacobwilliams/ddeabm/blob/master/LICENSE) (BSD-style).  The original DDEABM Fortran 77 code is [public domain](http://www.netlib.org/slatec/guide).
 
 ## Keywords
 

src/ddeabm_module.f90

@@ -239,6 +239,15 @@ module ddeabm_module
 
         subroutine deriv_func(me,t,x,xdot)
             !! Interface to the [[ddeabm_class]] derivative function.
+            !!
+            !! Known as `df` in the documentation. provided by the user 
+            !! to define the system of first order differential equations
+            !! which is to be solved.  for the given values of t and the
+            !! vector x(*)=(x(1),x(2),...,x(neq)), the subroutine must
+            !! evaluate the neq components of the system of differential
+            !! equations dx/dt=df(t,x) and store the derivatives in the
+            !! array xdot(*), that is, xdot(i) = dx(i)/dt for
+            !! equations i=1,...,neq.
             import :: wp,ddeabm_class
             implicit none
             class(ddeabm_class),intent(inout) :: me
@@ -1525,9 +1534,6 @@ end subroutine ddeabm_with_event_wrapper_vec
 !
 !   the parameters are
 !
-!      df -- this is the name of a subroutine which you provide to
-!             define the differential equations.
-!
 !      neq -- this is the number of (first order) differential
 !             equations to be integrated.
 !
@@ -1564,20 +1570,6 @@ end subroutine ddeabm_with_event_wrapper_vec
 !   appropriate variables for the initialization of the problem, and
 !   give information about how you want the problem to be solved.
 !
-!      df -- provide a subroutine of the form
-!                               df(x,u,uprime)
-!             to define the system of first order differential equations
-!             which is to be solved.  for the given values of x and the
-!             vector u(*)=(u(1),u(2),...,u(neq)), the subroutine must
-!             evaluate the neq components of the system of differential
-!             equations du/dx=df(x,u) and store the derivatives in the
-!             array uprime(*), that is, uprime(i) = du(i)/dx for
-!             equations i=1,...,neq.
-!
-!             subroutine df must not alter x or u(*).  you must declare
-!             the name df in an external statement in your program that
-!             calls ddeabm.  you must dimension u and uprime in df.
-!
 !      neq -- set it to the number of differential equations.
 !             (neq >= 1)
 !
@@ -1914,8 +1906,13 @@ subroutine ddeabm (me,neq,t,y,tout,info,rtol,atol,idid)
     implicit none
 
     class(ddeabm_class),intent(inout)     :: me
-    integer,intent(in)                    :: neq
-    real(wp),intent(inout)                :: t
+    integer,intent(in)                    :: neq    !! the number of (first order) differential
+                                                    !! equations to be integrated. (neq >= 1)
+    real(wp),intent(inout)                :: t      !! value of the independent variable. 
+                                                    !! on input, set it to the initial point of 
+                                                    !! the integration. the code changes its value.
+                                                    !! on output, the solution was successfully 
+                                                    !! advanced to the output value of t.
     real(wp),dimension(neq),intent(inout) :: y
     real(wp),intent(in)                   :: tout
     integer,dimension(4),intent(inout)    :: info

tests/ddeabm_test_vec.f90

@@ -176,6 +176,7 @@ subroutine twobody_event(me,t,x,g,ig)
         integer,intent(in),optional          :: ig  !! the event function to compute
 
         logical,dimension(ng) :: compute
+        integer :: i !! counter
 
         if (.not. present(ig)) then
             compute = .true. ! compute them all
@@ -184,7 +185,10 @@ subroutine twobody_event(me,t,x,g,ig)
             compute(ig) = .true. ! only compute this one
         end if
 
-        where (compute) g = r_target - x
+        !where (compute) g = r_target - x   ! gfortran 11.1 is crashing here.
+        do i = 1, ng 
+            if (compute(i)) g(i) = r_target(i) - x(i)
+        end do
 
         end subroutine twobody_event
     !*********************************************************