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Tweaked some stuff in app/Rcpp-interfaceR and FTCS

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This commit is contained in:
Marco De Lucia 2022-03-15 18:33:17 +01:00
parent fcef9553c9
commit 3ee1cd999c
2 changed files with 21 additions and 11 deletions
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28
app/Rcpp-interface.R
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@ -1,4 +1,4 @@
## Time-stamp: "Last modified 2022-03-15 18:04:27 delucia"
## Time-stamp: "Last modified 2022-03-15 18:31:55 delucia"
library(Rcpp)
library(RcppEigen)
library(ReacTran)
@ -18,7 +18,7 @@ sourceCpp("RcppFTCS.cpp")
## Grid 101
## Set initial conditions
N <- 501
N <- 1001
D.coeff <- 1E-3
C0 <- 1 ## Initial concentration (mg/L)
X0 <- 0 ## Location of initial concentration (m)
@ -34,25 +34,25 @@ Diffusion <- function (t, Y, parms){
## gaussian pulse as initial condition
sigma <- 0.01
Yini <- exp(-0.5*((x-1/2.0)**2)/sigma**2)
sigma <- 0.02
Yini <- 0.5*exp(-0.5*((x-1/2.0)**2)/sigma**2)
## plot(x, Yini, type="l")
parms1 <- list(D=D.coeff)
# 1 timestep, 10 s
times <- seq(from = 0, to = 1, by = 1)
times <- seq(from = 0, to = 1, by = 0.1)
system.time({
out1 <- ode.1D(y = Yini, times = times, func = Diffusion,
parms = parms1, dimens = N)[2,-1]
parms = parms1, dimens = N)[11,-1]
})
## Now with BTCS
alpha <- rep(D.coeff, N)
system.time({
out2 <- diff1D(n=N, length=1, field=Yini, alpha=alpha, timestep = 1, 0, 0, iterations = 1)
out2 <- diff1D(n=N, length=1, field=Yini, alpha=alpha, timestep = 0.1, 0, 0, iterations = 10)
})
## plot(out1, out2)
@ -75,8 +75,18 @@ mm <- colMeans(rbind(out2,out3))
matplot(cbind(Yini, out1, out2, out3, mm),type="l", col=c("black","grey","red","blue","green4"), lty=c("dashed", rep("solid",4)), lwd=2,
matplot(cbind(Yini,out1, out2, out3, mm),type="l", col=c("grey","black","red","blue","green4"), lty="solid", lwd=2,
xlab="grid element", ylab="Concentration", las=1)
legend("topright", c("Init","ReacTran ode1D", "BTCS 1d", "FTCS", "poor man's CN"), text.col=c("black","grey","red","blue","green4"), bty = "n")
legend("topright", c("init","ReacTran ode1D", "BTCS 1d", "FTCS", "poor man's CN"), text.col=c("grey","black","red","blue","green4"), bty = "n")
sum(Yini)
sum(out1)
sum(out2)
sum(out3)
sum(mm)
## Yini <- 0.2*sin(pi/0.1*x)+0.2
## plot(Yini)
## plot(out3)

4
app/RcppFTCS.cpp
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@ -1,4 +1,4 @@
// Time-stamp: "Last modified 2022-03-15 17:49:54 delucia"
// Time-stamp: "Last modified 2022-03-15 18:15:39 delucia"
#include <Rcpp.h>
#include <iostream> // for std
#include <vector> // for vector
@ -19,7 +19,7 @@ NumericVector RcppFTCS(int n,
// dimension of grid
NumericVector ext (clone(field));
double dx = length / ((double) n - 1.);
double dt = 0.5*dx*dx/alpha;
double dt = 0.25*dx*dx/alpha;
double afac = alpha*dt/dx/dx;