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Revision Log
Added simplified ASC_PANIC call that uses var-args, added throughout relation_util.c. Fixed var_filter_t stuff in djex and fvex. More assertions in integrator.c Added output of initial state from lsode.c (hoping that's a good idea?) Fixed output code from relman_diff2. Added asc_panic_nofunc for non var-arg CPPs. Disabled -O3 flag in building C++ API Added __getitem__ and __getattr__ methods in Simuluation for simplified python syntax (eg M.x instead M.sim.x) Integrator::analyse throws exceptions on error now.
| 1 | REQUIRE "ivpsystem.a4l"; |
| 2 | REQUIRE "atoms.a4l"; |
| 3 | |
| 4 | (* |
| 5 | An example problem used in the text by Zill, 4th Ed, p 472. |
| 6 | |
| 7 | Dennis G Zill, A First Course in Differential Equations with Applications, |
| 8 | PWS-KENTm Boston, 1989. |
| 9 | |
| 10 | Actually this is a single-variable integration and can be solved using the |
| 11 | Runge-Kutta method (as illustrated by Zill). |
| 12 | *) |
| 13 | MODEL zill; |
| 14 | x IS_A solver_var; |
| 15 | y IS_A solver_var; |
| 16 | dy_dx IS_A solver_var; |
| 17 | |
| 18 | xderiv: dy_dx = 2 * x * y; |
| 19 | |
| 20 | METHODS |
| 21 | |
| 22 | METHOD values; |
| 23 | y := 1; x := 1; (* initial conditions *) |
| 24 | dy_dx := 0; |
| 25 | END values; |
| 26 | |
| 27 | METHOD specify; |
| 28 | FIX x, y; |
| 29 | END specify; |
| 30 | |
| 31 | METHOD ode_init; |
| 32 | FREE x, y, dy_dx; |
| 33 | |
| 34 | x.ode_type := -1; |
| 35 | dy_dx.ode_id := 1; y.ode_id := 1; |
| 36 | dy_dx.ode_type := 2; y.ode_type := 1; |
| 37 | |
| 38 | x.obs_id := 1; |
| 39 | y.obs_id := 2; |
| 40 | END ode_init; |
| 41 | |
| 42 | METHOD on_load; |
| 43 | RUN reset; RUN values; |
| 44 | RUN ode_init; |
| 45 | END on_load; |
| 46 | |
| 47 | METHOD self_test; |
| 48 | (* assumes integration up to x = 1.5 *) |
| 49 | ASSERT abs(x - 1.5) < 1e-7; |
| 50 | ASSERT abs(y - 3.4904) < 0.001; (* this would be true if we used RK4, with h = 0.1 *) |
| 51 | END self_test; |
| 52 | |
| 53 | END zill; |
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