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/*---------------------------------------------------------------
* Programmer(s): Shelby Lockhart @ LLNL
*---------------------------------------------------------------
* Based on the serial code ark_heat1D_adapt.c developed
* by Daniel R. Reynolds and parallelized with OpenMP 4.5
*---------------------------------------------------------------
* SUNDIALS Copyright Start
* Copyright (c) 2002-2022, Lawrence Livermore National Security
* and Southern Methodist University.
* All rights reserved.
*
* See the top-level LICENSE and NOTICE files for details.
*
* SPDX-License-Identifier: BSD-3-Clause
* SUNDIALS Copyright End
*---------------------------------------------------------------
* Example problem:
*
* The following test simulates a simple 1D heat equation,
* u_t = k*u_xx + f
* for t in [0, 10], x in [0, 1], with initial conditions
* u(0,x) = 0
* Dirichlet boundary conditions, i.e.
* u_t(t,0) = u_t(t,1) = 0,
* and a heating term of the form
* f = 2*exp(-200*(x-0.25)*(x-0.25))
* - exp(-400*(x-0.7)*(x-0.7))
* + exp(-500*(x-0.4)*(x-0.4))
* - 2*exp(-600*(x-0.55)*(x-0.55));
*
* The spatial derivatives are computed using a three-point
* centered stencil (second order for a uniform mesh). The data
* is initially uniformly distributed over N points in the interval
* [0, 1], but as the simulation proceeds the mesh is adapted.
*
* This program solves the problem with a DIRK method, solved with
* a Newton iteration and SUNLinSol_PCG linear solver, with a
* user-supplied Jacobian-vector product routine.
*---------------------------------------------------------------*/
/* Header files */
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <arkode/arkode_arkstep.h> /* prototypes for ARKStep fcts., consts */
#include <nvector/nvector_openmpdev.h> /* OpenMPDEV N_Vector types, fcts., macros */
#include <sunlinsol/sunlinsol_pcg.h> /* access to PCG SUNLinearSolver */
#include <sundials/sundials_types.h> /* defs. of realtype, sunindextype, etc */
#include <sundials/sundials_math.h> /* def. of SUNRsqrt, etc. */
#ifdef _OPENMP
#include <omp.h> /* OpenMP functions */
#endif
#if defined(SUNDIALS_EXTENDED_PRECISION)
#define GSYM "Lg"
#define ESYM "Le"
#define FSYM "Lf"
#else
#define GSYM "g"
#define ESYM "e"
#define FSYM "f"
#endif
/* constants */
#define ZERO RCONST(0.0)
#define PT25 RCONST(0.25)
#define PT4 RCONST(0.4)
#define PT5 RCONST(0.5)
#define PT55 RCONST(0.55)
#define PT7 RCONST(0.7)
#define ONE RCONST(1.0)
#define TWO RCONST(2.0)
#define TWOHUNDRED RCONST(200.0)
#define FOURHUNDRED RCONST(400.0)
#define FIVEHUNDRED RCONST(500.0)
#define SIXHUNDRED RCONST(600.0)
/* user data structure */
typedef struct {
sunindextype N; /* current number of intervals */
realtype *x_host; /* current mesh on host */
realtype *x_dev; /* current mesh on device */
realtype k; /* diffusion coefficient */
realtype refine_tol; /* adaptivity tolerance */
} *UserData;
/* User-supplied Functions Called by the Solver */
static int f(realtype t, N_Vector y, N_Vector ydot, void *user_data);
static int Jac(N_Vector v, N_Vector Jv, realtype t, N_Vector y,
N_Vector fy, void *user_data, N_Vector tmp);
/* Private function to check function return values */
realtype * adapt_mesh(N_Vector y, sunindextype *Nnew, UserData udata);
static int project(sunindextype Nold, realtype *xold, N_Vector yold,
sunindextype Nnew, realtype *xnew, N_Vector ynew);
static int check_flag(void *flagvalue, const char *funcname, int opt);
/* Main Program */
int main() {
/* general problem parameters */
realtype T0 = RCONST(0.0); /* initial time */
realtype Tf = RCONST(1.0); /* final time */
realtype rtol = RCONST(1.e-3); /* relative tolerance */
realtype atol = RCONST(1.e-10); /* absolute tolerance */
realtype hscale = RCONST(1.0); /* time step change factor on resizes */
UserData udata = NULL;
realtype *data;
sunindextype N = 21; /* initial spatial mesh size */
realtype refine = RCONST(3.0e-3); /* adaptivity refinement tolerance */
realtype k = RCONST(0.5); /* heat conductivity */
sunindextype i;
long int nni, nni_tot=0, nli, nli_tot=0;
int iout=0;
/* general problem variables */
int flag; /* reusable error-checking flag */
N_Vector y = NULL; /* empty vector for storing solution */
N_Vector y2 = NULL; /* empty vector for storing solution */
N_Vector yt = NULL; /* empty vector for swapping */
SUNLinearSolver LS = NULL; /* empty linear solver object */
void *arkode_mem = NULL; /* empty ARKode memory structure */
FILE *XFID, *UFID;
realtype t, olddt, newdt;
realtype *xnew_host = NULL;
realtype *xnew_dev = NULL;
sunindextype Nnew;
int dev, host;
/* Create the SUNDIALS context object for this simulation */
SUNContext ctx;
flag = SUNContext_Create(NULL, &ctx);
if (check_flag(&flag, "SUNContext_Create", 1)) return 1;
/* get host and offloading device */
dev = omp_get_default_device();
host = omp_get_initial_device();
/* allocate and fill initial udata structure */
udata = (UserData) malloc(sizeof(*udata));
udata->N = N;
udata->k = k;
udata->refine_tol = refine;
udata->x_host = malloc(N * sizeof(realtype));
for (i=0; i<N; i++) udata->x_host[i] = ONE*i/(N-1);
udata->x_dev = omp_target_alloc(N * sizeof(realtype), dev);
omp_target_memcpy(udata->x_dev, udata->x_host, N * sizeof(realtype), 0, 0, dev, host);
/* Initial problem output */
printf("\n1D adaptive Heat PDE test problem:\n");
printf(" diffusion coefficient: k = %"GSYM"\n", udata->k);
printf(" initial N = %li\n", (long int) udata->N);
/* Initialize data structures */
y = N_VNew_OpenMPDEV(N, ctx); /* Create initial OpenMPDEV vector for solution */
if (check_flag((void *) y, "N_VNew_OpenMPDEV", 0)) return 1;
N_VConst(ZERO, y); /* Set initial conditions */
/* output mesh to disk */
XFID=fopen("heat_mesh.txt","w");
/* output initial mesh to disk */
for (i=0; i<udata->N; i++) fprintf(XFID," %.16"ESYM, udata->x_host[i]);
fprintf(XFID,"\n");
/* Open output stream for results, access data array */
UFID=fopen("heat1D.txt","w");
/* output initial condition to disk */
N_VCopyFromDevice_OpenMPDEV(y);
data = N_VGetHostArrayPointer_OpenMPDEV(y);
for (i=0; i<udata->N; i++) fprintf(UFID," %.16"ESYM, data[i]);
fprintf(UFID,"\n");
/* Initialize the ARK timestepper */
arkode_mem = ARKStepCreate(NULL, f, T0, y, ctx);
if (check_flag((void *) arkode_mem, "ARKStepCreate", 0)) return 1;
/* Set routines */
flag = ARKStepSetUserData(arkode_mem, (void *) udata); /* Pass udata to user functions */
if (check_flag(&flag, "ARKStepSetUserData", 1)) return 1;
flag = ARKStepSetMaxNumSteps(arkode_mem, 10000); /* Increase max num steps */
if (check_flag(&flag, "ARKStepSetMaxNumSteps", 1)) return 1;
flag = ARKStepSStolerances(arkode_mem, rtol, atol); /* Specify tolerances */
if (check_flag(&flag, "ARKStepSStolerances", 1)) return 1;
flag = ARKStepSetAdaptivityMethod(arkode_mem, 2, 1, 0, NULL); /* Set adaptivity method */
if (check_flag(&flag, "ARKStepSetAdaptivityMethod", 1)) return 1;
flag = ARKStepSetPredictorMethod(arkode_mem, 0); /* Set predictor method */
if (check_flag(&flag, "ARKStepSetPredictorMethod", 1)) return 1;
/* Specify linearly implicit RHS, with time-dependent Jacobian */
flag = ARKStepSetLinear(arkode_mem, 1);
if (check_flag(&flag, "ARKStepSetLinear", 1)) return 1;
/* Initialize PCG solver -- no preconditioning, with up to N iterations */
LS = SUNLinSol_PCG(y, 0, (int) N, ctx);
if (check_flag((void *)LS, "SUNLinSol_PCG", 0)) return 1;
/* Linear solver interface -- set user-supplied J*v routine (no 'jtsetup' required) */
flag = ARKStepSetLinearSolver(arkode_mem, LS, NULL); /* Attach linear solver to ARKStep */
if (check_flag(&flag, "ARKStepSetLinearSolver", 1)) return 1;
flag = ARKStepSetJacTimes(arkode_mem, NULL, Jac); /* Set the Jacobian routine */
if (check_flag(&flag, "ARKStepSetJacTimes", 1)) return 1;
/* Main time-stepping loop: calls ARKStepEvolve to perform the integration, then
prints results. Stops when the final time has been reached */
t = T0;
olddt = ZERO;
newdt = ZERO;
printf(" iout dt_old dt_new ||u||_rms N NNI NLI\n");
printf(" ----------------------------------------------------------------------------------------\n");
printf(" %4i %19.15"ESYM" %19.15"ESYM" %19.15"ESYM" %li %2i %3i\n",
iout, olddt, newdt, SUNRsqrt(N_VDotProd(y,y)/udata->N),
(long int) udata->N, 0, 0);
while (t < Tf) {
/* "set" routines */
flag = ARKStepSetStopTime(arkode_mem, Tf);
if (check_flag(&flag, "ARKStepSetStopTime", 1)) return 1;
flag = ARKStepSetInitStep(arkode_mem, newdt);
if (check_flag(&flag, "ARKStepSetInitStep", 1)) return 1;
/* call integrator */
flag = ARKStepEvolve(arkode_mem, Tf, y, &t, ARK_ONE_STEP);
if (check_flag(&flag, "ARKStepEvolve", 1)) return 1;
/* "get" routines */
flag = ARKStepGetLastStep(arkode_mem, &olddt);
if (check_flag(&flag, "ARKStepGetLastStep", 1)) return 1;
flag = ARKStepGetCurrentStep(arkode_mem, &newdt);
if (check_flag(&flag, "ARKStepGetCurrentStep", 1)) return 1;
flag = ARKStepGetNumNonlinSolvIters(arkode_mem, &nni);
if (check_flag(&flag, "ARKStepGetNumNonlinSolvIters", 1)) return 1;
flag = ARKStepGetNumLinIters(arkode_mem, &nli);
if (check_flag(&flag, "ARKStepGetNumLinIters", 1)) return 1;
/* print current solution stats */
iout++;
printf(" %4i %19.15"ESYM" %19.15"ESYM" %19.15"ESYM" %li %2li %3li\n",
iout, olddt, newdt, SUNRsqrt(N_VDotProd(y,y)/udata->N),
(long int) udata->N, nni, nli);
nni_tot += nni;
nli_tot += nli;
/* output results and current mesh to disk */
N_VCopyFromDevice_OpenMPDEV(y);
data = N_VGetHostArrayPointer_OpenMPDEV(y);
for (i=0; i<udata->N; i++) fprintf(UFID," %.16"ESYM, data[i]);
fprintf(UFID,"\n");
for (i=0; i<udata->N; i++) fprintf(XFID," %.16"ESYM, udata->x_host[i]);
fprintf(XFID,"\n");
/* adapt the spatial mesh */
xnew_host = adapt_mesh(y, &Nnew, udata);
if (check_flag(xnew_host, "ark_adapt", 0)) return 1;
/* create N_Vector of new length */
y2 = N_VNew_OpenMPDEV(Nnew, ctx);
if (check_flag((void *) y2, "N_VNew_OpenMPDEV", 0)) return 1;
/* copy new mesh from host array to device array */
xnew_dev = omp_target_alloc(Nnew * sizeof(realtype), dev);
omp_target_memcpy(xnew_dev, xnew_host, Nnew*sizeof(realtype), 0, 0, dev, host);
/* project solution onto new mesh */
flag = project(udata->N, udata->x_dev, y, Nnew, xnew_dev, y2);
if (check_flag(&flag, "project", 1)) return 1;
/* delete old vector, old mesh */
N_VDestroy(y);
free(udata->x_host);
omp_target_free(udata->x_dev, dev);
/* swap x and xnew so that new mesh is stored in udata structure */
udata->x_host = xnew_host;
xnew_host = NULL;
udata->N = Nnew; /* store size of new mesh */
udata->x_dev = xnew_dev;
xnew_dev = NULL;
/* swap y and y2 so that y holds new solution */
yt = y;
y = y2;
y2 = yt;
/* call ARKStepResize to notify integrator of change in mesh */
flag = ARKStepResize(arkode_mem, y, hscale, t, NULL, NULL);
if (check_flag(&flag, "ARKStepResize", 1)) return 1;
/* destroy and re-allocate linear solver memory; reattach to ARKStep interface */
SUNLinSolFree(LS);
LS = SUNLinSol_PCG(y, 0, (int) N, ctx);
if (check_flag((void *)LS, "SUNLinSol_PCG", 0)) return 1;
flag = ARKStepSetLinearSolver(arkode_mem, LS, NULL);
if (check_flag(&flag, "ARKStepSetLinearSolver", 1)) return 1;
flag = ARKStepSetJacTimes(arkode_mem, NULL, Jac);
if (check_flag(&flag, "ARKStepSetJacTimes", 1)) return 1;
}
printf(" ----------------------------------------------------------------------------------------\n");
/* print some final statistics */
printf(" Final solver statistics:\n");
printf(" Total number of time steps = %i\n", iout);
printf(" Total nonlinear iterations = %li\n", nni_tot);
printf(" Total linear iterations = %li\n\n", nli_tot);
/* Clean up and return with successful completion */
fclose(UFID);
fclose(XFID);
N_VDestroy(y); /* Free vectors */
free(udata->x_host); /* Free user data */
omp_target_free(udata->x_dev, dev);
free(udata);
ARKStepFree(&arkode_mem); /* Free integrator memory */
SUNLinSolFree(LS); /* Free linear solver */
SUNContext_Free(&ctx); /* Free context */
return 0;
}
/*--------------------------------
* Functions called by the solver
*--------------------------------*/
/* f routine to compute the ODE RHS function f(t,y). */
static int f(realtype t, N_Vector y, N_Vector ydot, void *user_data)
{
UserData udata = (UserData) user_data; /* access problem data */
sunindextype N = udata->N; /* set variable shortcuts */
realtype k = udata->k;
realtype *x = udata->x_dev;
realtype *Y=NULL, *Ydot=NULL;
realtype dxL, dxR;
sunindextype i;
int dev;
dev = omp_get_default_device();
/* access data arrays */
Y = N_VGetDeviceArrayPointer_OpenMPDEV(y);
if (check_flag((void *) Y, "N_VGetDeviceArrayPointer", 0)) return 1;
Ydot = N_VGetDeviceArrayPointer_OpenMPDEV(ydot);
if (check_flag((void *) Ydot, "N_VGetDeviceArrayPointer", 0)) return 1;
/* Initialize ydot to zero - also handles boundary conditions */
N_VConst(ZERO, ydot);
/* iterate over domain interior, computing all equations */
#pragma omp target map(to:N) is_device_ptr(x, Ydot, Y) device(dev)
#pragma omp teams distribute parallel for schedule(static, 1)
for (i=1; i<N-1; i++) { /* interior */
dxL = x[i]-x[i-1];
dxR = x[i+1]-x[i];
Ydot[i] = Y[i-1]*k*TWO/(dxL*(dxL+dxR))
- Y[i]*k*TWO/(dxL*dxR)
+ Y[i+1]*k*TWO/(dxR*(dxL+dxR))
+ TWO*SUNRexp(-TWOHUNDRED*(x[i]-PT25)*(x[i]-PT25)) /* source term */
- SUNRexp(-FOURHUNDRED*(x[i]-PT7)*(x[i]-PT7))
+ SUNRexp(-FIVEHUNDRED*(x[i]-PT4)*(x[i]-PT4))
- TWO*SUNRexp(-SIXHUNDRED*(x[i]-PT55)*(x[i]-PT55));
}
return 0; /* Return with success */
}
/* Jacobian routine to compute J(t,y) = df/dy. */
static int Jac(N_Vector v, N_Vector Jv, realtype t, N_Vector y,
N_Vector fy, void *user_data, N_Vector tmp)
{
UserData udata = (UserData) user_data; /* variable shortcuts */
sunindextype N = udata->N;
realtype k = udata->k;
realtype *x = udata->x_dev;
realtype *V=NULL, *JV=NULL;
realtype dxL, dxR;
sunindextype i;
int dev;
dev = omp_get_default_device();
/* access data arrays */
V = N_VGetDeviceArrayPointer_OpenMPDEV(v);
if (check_flag((void *) V, "N_VGetDeviceArrayPointer", 0)) return 1;
JV = N_VGetDeviceArrayPointer_OpenMPDEV(Jv);
if (check_flag((void *) JV, "N_VGetDeviceArrayPointer", 0)) return 1;
/* initialize Jv product to zero - also handles boundary conditions */
N_VConst(ZERO, Jv);
/* iterate over domain, computing all Jacobian-vector products */
#pragma omp target map(to:N) is_device_ptr(x, JV, V) device(dev)
#pragma omp teams distribute parallel for schedule(static, 1)
for (i=1; i<N-1; i++) {
dxL = x[i]-x[i-1];
dxR = x[i+1]-x[i];
JV[i] = V[i-1]*k*TWO/(dxL*(dxL+dxR))
- V[i]*k*TWO/(dxL*dxR)
+ V[i+1]*k*TWO/(dxR*(dxL+dxR));
}
return 0; /* Return with success */
}
/*-------------------------------
* Private helper functions
*-------------------------------*/
/* Adapts the current mesh, using a simple adaptivity strategy of
refining when an approximation of the scaled second-derivative is
too large. We only do this in one sweep, so no attempt is made to
ensure the resulting mesh meets these same criteria after adaptivity:
y [input] -- the current solution vector
Nnew [output] -- the size of the new mesh
udata [input] -- the current system information
The return for this function is a pointer to the new mesh. */
realtype* adapt_mesh(N_Vector y, sunindextype *Nnew, UserData udata)
{
sunindextype i, j;
int *marks=NULL;
realtype ydd, *xold=NULL, *Y=NULL, *xnew=NULL;
sunindextype num_refine, N_new;
/* Access current solution and mesh arrays */
xold = udata->x_host;
Y = N_VGetHostArrayPointer_OpenMPDEV(y); /* assumes copy to host already done */
if (check_flag((void *) Y, "N_VGetHostArrayPointer_OpenMPDEV", 0)) return NULL;
/* create marking array */
marks = calloc(udata->N-1, sizeof(int));
/* perform marking:
0 -> leave alone
1 -> refine */
for (i=1; i<udata->N-1; i++) {
/* approximate scaled second-derivative */
ydd = Y[i-1] - TWO*Y[i] + Y[i+1];
/* check for refinement */
if (fabs(ydd) > udata->refine_tol) {
marks[i-1] = 1;
marks[i] = 1;
}
}
/* allocate new mesh */
num_refine = 0;
for (i=0; i<udata->N-1; i++)
if (marks[i] == 1) num_refine++;
N_new = udata->N + num_refine;
*Nnew = N_new; /* Store new array length */
xnew = malloc((N_new) * sizeof(realtype));
/* fill new mesh */
xnew[0] = xold[0]; /* store endpoints */
xnew[N_new-1] = xold[udata->N-1];
j=1;
/* iterate over old intervals */
for (i=0; i<udata->N-1; i++) {
/* if mark is 0, reuse old interval */
if (marks[i] == 0) {
xnew[j++] = xold[i+1];
continue;
}
/* if mark is 1, refine old interval */
if (marks[i] == 1) {
xnew[j++] = PT5*(xold[i]+xold[i+1]);
xnew[j++] = xold[i+1];
continue;
}
}
/* verify that new mesh is legal */
for (i=0; i<N_new-1; i++) {
if (xnew[i+1] <= xnew[i]) {
fprintf(stderr,"adapt_mesh error: illegal mesh created\n");
free(xnew);
return NULL;
}
}
free(marks); /* Delete marking array */
return xnew; /* Return with success */
}
/* Projects one vector onto another:
Nold [input] -- the size of the old mesh
xold [input] -- the old mesh
yold [input] -- the vector defined over the old mesh
Nnew [input] -- the size of the new mesh
xnew [input] -- the new mesh
ynew [output] -- the vector defined over the new mesh
(allocated prior to calling project) */
static int project(sunindextype Nold, realtype *xold, N_Vector yold,
sunindextype Nnew, realtype *xnew, N_Vector ynew)
{
sunindextype iv, i, j;
realtype *Yold=NULL, *Ynew=NULL;
int dev = omp_get_default_device();
/* Access data arrays */
Yold = N_VGetDeviceArrayPointer_OpenMPDEV(yold); /* access data arrays */
if (check_flag((void *) Yold, "N_VGetDeviceArrayPointer_OpenMPDEV", 0)) return 1;
Ynew = N_VGetDeviceArrayPointer_OpenMPDEV(ynew);
if (check_flag((void *) Ynew, "N_VGetDeviceArrayPointer_OpenMPDEV", 0)) return 1;
/* loop over new mesh, finding corresponding interval within old mesh,
and perform piecewise linear interpolation from yold to ynew */
iv=0;
#pragma omp target map(to:iv) is_device_ptr(Yold,Ynew,xnew,xold) device(dev)
#pragma omp teams distribute parallel for schedule(static, 1)
{
for (i=0; i<Nnew; i++) {
/* find old interval, start with previous value since sorted */
for (j=iv; j<Nold-1; j++) {
if (xnew[i] >= xold[j] && xnew[i] <= xold[j+1]) {
iv = j;
break;
}
iv = Nold-1; /* just in case it wasn't found above */
}
/* perform interpolation */
Ynew[i] = Yold[iv]*(xnew[i]-xold[iv+1])/(xold[iv]-xold[iv+1])
+ Yold[iv+1]*(xnew[i]-xold[iv])/(xold[iv+1]-xold[iv]);
}
}
return 0; /* Return with success */
}
/* Check function return value...
opt == 0 means SUNDIALS function allocates memory so check if
returned NULL pointer
opt == 1 means SUNDIALS function returns a flag so check if
flag >= 0
opt == 2 means function allocates memory so check if returned
NULL pointer
*/
static int check_flag(void *flagvalue, const char *funcname, int opt)
{
int *errflag;
/* Check if SUNDIALS function returned NULL pointer - no memory allocated */
if (opt == 0 && flagvalue == NULL) {
fprintf(stderr, "\nSUNDIALS_ERROR: %s() failed - returned NULL pointer\n\n",
funcname);
return 1; }
/* Check if flag < 0 */
else if (opt == 1) {
errflag = (int *) flagvalue;
if (*errflag < 0) {
fprintf(stderr, "\nSUNDIALS_ERROR: %s() failed with flag = %d\n\n",
funcname, *errflag);
return 1; }}
/* Check if function returned NULL pointer - no memory allocated */
else if (opt == 2 && flagvalue == NULL) {
fprintf(stderr, "\nMEMORY_ERROR: %s() failed - returned NULL pointer\n\n",
funcname);
return 1; }
return 0;
}
/*---- end of file ----*/
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