Time schemes¶

Time integration is expressed as a compiled pops.time.Program.

pops.time contains the language. pops.lib.time contains ready schemes.

from pops.time import Program
from pops.lib.time import ssprk3

time = Program("advance")
ssprk3(time, "plasma")
case = case.time(time)

Manual schemes use temporal handles:

from pops.numerics.terms import Flux

T = Program("forward_euler")
U = T.state("U", block="plasma")
fields = T.solve_fields(U.n)
R = T.rhs(state=U.n, fields=fields, terms=[Flux()])
T.define(U.next, U.n + T.dt * R)
T.commit("plasma", U.next)

Provided scheme families¶

Function	Package
`forward_euler`	`pops.lib.time`
`ssprk2`, `ssprk3`	`pops.lib.time`
`rk4`, `rk`, `explicit_rk`	`pops.lib.time`
`adams_bashforth`, `bdf`	`pops.lib.time`
`strang`, `lie`	`pops.lib.time`
`imex_local`, `imex_local_linear`	`pops.lib.time`
`condensed_schur`	`pops.lib.time`

These functions build IR nodes. They are not alternate runtime steppers.

CFL¶

The CFL value is a runtime policy passed to sim.run.

sim.run(t_final=1.0, cfl=0.4)

The time program should not reject a run only because the CFL is not a compile time default.