static char help[] = "Plots the various potentials used in the examples.\n";

#include <petscdmda.h>
#include <petscts.h>
#include <petscdraw.h>

int main(int argc, char **argv)
{
  PetscDrawLG         lg;
  PetscInt            Mx = 100, i;
  PetscReal           x, hx = .1 / Mx, pause, xx[3], yy[3];
  PetscDraw           draw;
  const char *const   legend[] = {"(1 - u^2)^2", "1 - u^2", "-(1 - u)log(1 - u)"};
  PetscDrawAxis       axis;
  PetscDrawViewPorts *ports;

  PetscFunctionBegin;
  PetscFunctionBeginUser;
  PetscCall(PetscInitialize(&argc, &argv, 0, help));
  PetscCall(PetscViewerDrawResize(PETSC_VIEWER_DRAW_(PETSC_COMM_WORLD), 1200, 800));
  PetscCall(PetscViewerDrawGetDrawLG(PETSC_VIEWER_DRAW_(PETSC_COMM_WORLD), 0, &lg));
  PetscCall(PetscDrawLGGetDraw(lg, &draw));
  PetscCall(PetscDrawCheckResizedWindow(draw));
  PetscCall(PetscDrawViewPortsCreateRect(draw, 1, 2, &ports));
  PetscCall(PetscDrawLGGetAxis(lg, &axis));
  PetscCall(PetscDrawLGReset(lg));

  /*
      Plot the  energies
  */
  PetscCall(PetscDrawLGSetDimension(lg, 3));
  PetscCall(PetscDrawViewPortsSet(ports, 1));
  x = .9;
  for (i = 0; i < Mx; i++) {
    xx[0] = xx[1] = xx[2] = x;
    yy[0]                 = (1. - x * x) * (1. - x * x);
    yy[1]                 = (1. - x * x);
    yy[2]                 = -(1. - x) * PetscLogReal(1. - x);
    PetscCall(PetscDrawLGAddPoint(lg, xx, yy));
    x += hx;
  }
  PetscCall(PetscDrawGetPause(draw, &pause));
  PetscCall(PetscDrawSetPause(draw, 0.0));
  PetscCall(PetscDrawAxisSetLabels(axis, "Energy", "", ""));
  PetscCall(PetscDrawLGSetLegend(lg, legend));
  PetscCall(PetscDrawLGDraw(lg));

  /*
      Plot the  forces
  */
  PetscCall(PetscDrawViewPortsSet(ports, 0));
  PetscCall(PetscDrawLGReset(lg));
  x = .9;
  for (i = 0; i < Mx; i++) {
    xx[0] = xx[1] = xx[2] = x;
    yy[0]                 = x * x * x - x;
    yy[1]                 = -x;
    yy[2]                 = 1.0 + PetscLogReal(1. - x);
    PetscCall(PetscDrawLGAddPoint(lg, xx, yy));
    x += hx;
  }
  PetscCall(PetscDrawAxisSetLabels(axis, "Derivative", "", ""));
  PetscCall(PetscDrawLGSetLegend(lg, NULL));
  PetscCall(PetscDrawLGDraw(lg));

  PetscCall(PetscDrawSetPause(draw, pause));
  PetscCall(PetscDrawPause(draw));
  PetscCall(PetscDrawViewPortsDestroy(ports));
  PetscCall(PetscFinalize());
  return 0;
}

/*TEST

   test:
     requires: x

TEST*/