project_n_2: Project values with a predictor-corrector method

In mizer: Dynamic Multi-Species Size Spectrum Modelling

Project values with a predictor-corrector method

Description

This is an experimental second-order time stepping variant of project_n(). It first predicts the new consumer densities with project_n(), optionally recalculates rates from that prediction, and then applies a Crank-Nicolson corrector using midpoint rates.

Usage

project_n_2(
  params,
  r,
  n,
  dt,
  a,
  b,
  c,
  S,
  idx,
  w_min_idx_array_ref,
  no_sp,
  no_w,
  rates_fns = NULL,
  n_pp = NULL,
  n_other = NULL,
  t = 0,
  effort = NULL,
  r_hat = NULL,
  r_mid = NULL,
  n_hat = NULL,
  flux_limiter = "none",
  ...
)

Arguments

params	A MizerParams object.
r	A list of rates as returned by mizerRates().
n	An array (species x size) with the number density at the current time step.
dt	Time step.
a	A matrix (species x size) used in the solver (transport term).
b	A matrix (species x size) used in the solver (diagonal term).
c	A matrix (species x size) used in the solver (transport term).
S	A matrix (species x size) used in the solver (source term).
idx	Index vector for size bins (excluding the first one).
w_min_idx_array_ref	Index vector for the start of the size spectrum for each species.
no_sp	Number of species.
no_w	Number of size bins.
rates_fns	Optional named list of rate functions, as used by mizerRates(). If supplied together with n_pp, n_other and effort, provisional end-of-step rates are calculated from the predicted densities.
n_pp	Resource abundance used when recalculating provisional rates.
n_other	Other ecosystem components used when recalculating provisional rates.
t	Current time.
effort	Fishing effort used when recalculating provisional rates.
r_hat	Optional provisional end-of-step rates. If supplied, these are used instead of recalculating them.
r_mid	Optional midpoint rates. If supplied, these are used directly in the Crank-Nicolson corrector.
n_hat	Optional provisional end-of-step densities. When supplied with a flux limiter, the limiter is frozen at the midpoint field (n + n_hat) / 2; otherwise it falls back to the start-of-step n.
flux_limiter	Name of the flux limiter used for a deferred high-order correction of the upwind advective flux, or "none" for plain first-order upwind. See project().
...	Further arguments passed to the rate functions.

Details

If the rate recalculation arguments are not supplied, the corrector uses the supplied rates as fixed rates. In that case the corrector is second order only for the frozen-rate transport problem, not for the full nonlinear mizer dynamics.

Value

The updated abundance density matrix n.

See Also

project_n

mizer documentation built on Aug. 31, 2026, 5:08 p.m.