예제 #1
0
PETSC_EXTERN void PETSC_STDCALL  vecstepboundinfo_(Vec X,Vec DX,Vec XL,Vec XU,PetscReal *boundmin,PetscReal *wolfemin,PetscReal *boundmax, int *__ierr ){
*__ierr = VecStepBoundInfo(
	(Vec)PetscToPointer((X) ),
	(Vec)PetscToPointer((DX) ),
	(Vec)PetscToPointer((XL) ),
	(Vec)PetscToPointer((XU) ),boundmin,wolfemin,boundmax);
}
예제 #2
0
static PetscErrorCode TaoLineSearchApply_MT(TaoLineSearch ls, Vec x, PetscReal *f, Vec g, Vec s)
{
  PetscErrorCode   ierr;
  TaoLineSearch_MT *mt;

  PetscReal        xtrapf = 4.0;
  PetscReal        finit, width, width1, dginit, fm, fxm, fym, dgm, dgxm, dgym;
  PetscReal        dgx, dgy, dg, dg2, fx, fy, stx, sty, dgtest;
  PetscReal        ftest1=0.0, ftest2=0.0;
  PetscInt         i, stage1,n1,n2,nn1,nn2;
  PetscReal        bstepmin1, bstepmin2, bstepmax;
  PetscBool        g_computed=PETSC_FALSE; /* to prevent extra gradient computation */

  PetscFunctionBegin;
  PetscValidHeaderSpecific(ls,TAOLINESEARCH_CLASSID,1);
  PetscValidHeaderSpecific(x,VEC_CLASSID,2);
  PetscValidScalarPointer(f,3);
  PetscValidHeaderSpecific(g,VEC_CLASSID,4);
  PetscValidHeaderSpecific(s,VEC_CLASSID,5);

  /* comm,type,size checks are done in interface TaoLineSearchApply */
  mt = (TaoLineSearch_MT*)(ls->data);
  ls->reason = TAOLINESEARCH_CONTINUE_ITERATING;

  /* Check work vector */
  if (!mt->work) {
    ierr = VecDuplicate(x,&mt->work);CHKERRQ(ierr);
    mt->x = x;
    ierr = PetscObjectReference((PetscObject)mt->x);CHKERRQ(ierr);
  } else if (x != mt->x) {
    ierr = VecDestroy(&mt->work);CHKERRQ(ierr);
    ierr = VecDuplicate(x,&mt->work);CHKERRQ(ierr);
    ierr = PetscObjectDereference((PetscObject)mt->x);CHKERRQ(ierr);
    mt->x = x;
    ierr = PetscObjectReference((PetscObject)mt->x);CHKERRQ(ierr);
  }

  if (ls->bounded) {
    /* Compute step length needed to make all variables equal a bound */
    /* Compute the smallest steplength that will make one nonbinding variable
     equal the bound */
    ierr = VecGetLocalSize(ls->upper,&n1);CHKERRQ(ierr);
    ierr = VecGetLocalSize(mt->x, &n2);CHKERRQ(ierr);
    ierr = VecGetSize(ls->upper,&nn1);CHKERRQ(ierr);
    ierr = VecGetSize(mt->x,&nn2);CHKERRQ(ierr);
    if (n1 != n2 || nn1 != nn2) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_SIZ,"Variable vector not compatible with bounds vector");
    ierr = VecScale(s,-1.0);CHKERRQ(ierr);
    ierr = VecBoundGradientProjection(s,x,ls->lower,ls->upper,s);CHKERRQ(ierr);
    ierr = VecScale(s,-1.0);CHKERRQ(ierr);
    ierr = VecStepBoundInfo(x,s,ls->lower,ls->upper,&bstepmin1,&bstepmin2,&bstepmax);CHKERRQ(ierr);
    ls->stepmax = PetscMin(bstepmax,1.0e15);
  }

  ierr = VecDot(g,s,&dginit);CHKERRQ(ierr);
  if (PetscIsInfOrNanReal(dginit)) {
    ierr = PetscInfo1(ls,"Initial Line Search step * g is Inf or Nan (%g)\n",(double)dginit);CHKERRQ(ierr);
    ls->reason=TAOLINESEARCH_FAILED_INFORNAN;
    PetscFunctionReturn(0);
  }
  if (dginit >= 0.0) {
    ierr = PetscInfo1(ls,"Initial Line Search step * g is not descent direction (%g)\n",(double)dginit);CHKERRQ(ierr);
    ls->reason = TAOLINESEARCH_FAILED_ASCENT;
    PetscFunctionReturn(0);
  }


  /* Initialization */
  mt->bracket = 0;
  stage1 = 1;
  finit = *f;
  dgtest = ls->ftol * dginit;
  width = ls->stepmax - ls->stepmin;
  width1 = width * 2.0;
  ierr = VecCopy(x,mt->work);CHKERRQ(ierr);
  /* Variable dictionary:
   stx, fx, dgx - the step, function, and derivative at the best step
   sty, fy, dgy - the step, function, and derivative at the other endpoint
   of the interval of uncertainty
   step, f, dg - the step, function, and derivative at the current step */

  stx = 0.0;
  fx  = finit;
  dgx = dginit;
  sty = 0.0;
  fy  = finit;
  dgy = dginit;

  ls->step=ls->initstep;
  for (i=0; i< ls->max_funcs; i++) {
    /* Set min and max steps to correspond to the interval of uncertainty */
    if (mt->bracket) {
      ls->stepmin = PetscMin(stx,sty);
      ls->stepmax = PetscMax(stx,sty);
    } else {
      ls->stepmin = stx;
      ls->stepmax = ls->step + xtrapf * (ls->step - stx);
    }

    /* Force the step to be within the bounds */
    ls->step = PetscMax(ls->step,ls->stepmin);
    ls->step = PetscMin(ls->step,ls->stepmax);

    /* If an unusual termination is to occur, then let step be the lowest
     point obtained thus far */
    if ((stx!=0) && (((mt->bracket) && (ls->step <= ls->stepmin || ls->step >= ls->stepmax)) || ((mt->bracket) && (ls->stepmax - ls->stepmin <= ls->rtol * ls->stepmax)) ||
                     ((ls->nfeval+ls->nfgeval) >= ls->max_funcs - 1) || (mt->infoc == 0))) {
      ls->step = stx;
    }

    ierr = VecCopy(x,mt->work);CHKERRQ(ierr);
    ierr = VecAXPY(mt->work,ls->step,s);CHKERRQ(ierr);   /* W = X + step*S */

    if (ls->bounded) {
      ierr = VecMedian(ls->lower, mt->work, ls->upper, mt->work);CHKERRQ(ierr);
    }
    if (ls->usegts) {
      ierr = TaoLineSearchComputeObjectiveAndGTS(ls,mt->work,f,&dg);CHKERRQ(ierr);
      g_computed=PETSC_FALSE;
    } else {
      ierr = TaoLineSearchComputeObjectiveAndGradient(ls,mt->work,f,g);CHKERRQ(ierr);
      g_computed=PETSC_TRUE;
      if (ls->bounded) {
        ierr = VecDot(g,x,&dg);CHKERRQ(ierr);
        ierr = VecDot(g,mt->work,&dg2);CHKERRQ(ierr);
        dg = (dg2 - dg)/ls->step;
      } else {
        ierr = VecDot(g,s,&dg);CHKERRQ(ierr);
      }
    }

    if (0 == i) {
      ls->f_fullstep=*f;
    }

    if (PetscIsInfOrNanReal(*f) || PetscIsInfOrNanReal(dg)) {
      /* User provided compute function generated Not-a-Number, assume
       domain violation and set function value and directional
       derivative to infinity. */
      *f = PETSC_INFINITY;
      dg = PETSC_INFINITY;
    }

    ftest1 = finit + ls->step * dgtest;
    if (ls->bounded) {
      ftest2 = finit + ls->step * dgtest * ls->ftol;
    }
    /* Convergence testing */
    if (((*f - ftest1 <= 1.0e-10 * PetscAbsReal(finit)) &&  (PetscAbsReal(dg) + ls->gtol*dginit <= 0.0))) {
      ierr = PetscInfo(ls, "Line search success: Sufficient decrease and directional deriv conditions hold\n");CHKERRQ(ierr);
      ls->reason = TAOLINESEARCH_SUCCESS;
      break;
    }

    /* Check Armijo if beyond the first breakpoint */
    if (ls->bounded && (*f <= ftest2) && (ls->step >= bstepmin2)) {
      ierr = PetscInfo(ls,"Line search success: Sufficient decrease.\n");CHKERRQ(ierr);
      ls->reason = TAOLINESEARCH_SUCCESS;
      break;
    }

    /* Checks for bad cases */
    if (((mt->bracket) && (ls->step <= ls->stepmin||ls->step >= ls->stepmax)) || (!mt->infoc)) {
      ierr = PetscInfo(ls,"Rounding errors may prevent further progress.  May not be a step satisfying\n");CHKERRQ(ierr);
      ierr = PetscInfo(ls,"sufficient decrease and curvature conditions. Tolerances may be too small.\n");CHKERRQ(ierr);
      ls->reason = TAOLINESEARCH_HALTED_OTHER;
      break;
    }
    if ((ls->step == ls->stepmax) && (*f <= ftest1) && (dg <= dgtest)) {
      ierr = PetscInfo1(ls,"Step is at the upper bound, stepmax (%g)\n",(double)ls->stepmax);CHKERRQ(ierr);
      ls->reason = TAOLINESEARCH_HALTED_UPPERBOUND;
      break;
    }
    if ((ls->step == ls->stepmin) && (*f >= ftest1) && (dg >= dgtest)) {
      ierr = PetscInfo1(ls,"Step is at the lower bound, stepmin (%g)\n",(double)ls->stepmin);CHKERRQ(ierr);
      ls->reason = TAOLINESEARCH_HALTED_LOWERBOUND;
      break;
    }
    if ((mt->bracket) && (ls->stepmax - ls->stepmin <= ls->rtol*ls->stepmax)){
      ierr = PetscInfo1(ls,"Relative width of interval of uncertainty is at most rtol (%g)\n",(double)ls->rtol);CHKERRQ(ierr);
      ls->reason = TAOLINESEARCH_HALTED_RTOL;
      break;
    }

    /* In the first stage, we seek a step for which the modified function
     has a nonpositive value and nonnegative derivative */
    if ((stage1) && (*f <= ftest1) && (dg >= dginit * PetscMin(ls->ftol, ls->gtol))) {
      stage1 = 0;
    }

    /* A modified function is used to predict the step only if we
     have not obtained a step for which the modified function has a
     nonpositive function value and nonnegative derivative, and if a
     lower function value has been obtained but the decrease is not
     sufficient */

    if ((stage1) && (*f <= fx) && (*f > ftest1)) {
      fm   = *f - ls->step * dgtest;    /* Define modified function */
      fxm  = fx - stx * dgtest;         /* and derivatives */
      fym  = fy - sty * dgtest;
      dgm  = dg - dgtest;
      dgxm = dgx - dgtest;
      dgym = dgy - dgtest;

      /* if (dgxm * (ls->step - stx) >= 0.0) */
      /* Update the interval of uncertainty and compute the new step */
      ierr = Tao_mcstep(ls,&stx,&fxm,&dgxm,&sty,&fym,&dgym,&ls->step,&fm,&dgm);CHKERRQ(ierr);

      fx  = fxm + stx * dgtest; /* Reset the function and */
      fy  = fym + sty * dgtest; /* gradient values */
      dgx = dgxm + dgtest;
      dgy = dgym + dgtest;
    } else {
      /* Update the interval of uncertainty and compute the new step */
      ierr = Tao_mcstep(ls,&stx,&fx,&dgx,&sty,&fy,&dgy,&ls->step,f,&dg);CHKERRQ(ierr);
    }

    /* Force a sufficient decrease in the interval of uncertainty */
    if (mt->bracket) {
      if (PetscAbsReal(sty - stx) >= 0.66 * width1) ls->step = stx + 0.5*(sty - stx);
      width1 = width;
      width = PetscAbsReal(sty - stx);
    }
  }
  if ((ls->nfeval+ls->nfgeval) > ls->max_funcs) {
    ierr = PetscInfo2(ls,"Number of line search function evals (%D) > maximum (%D)\n",(ls->nfeval+ls->nfgeval),ls->max_funcs);CHKERRQ(ierr);
    ls->reason = TAOLINESEARCH_HALTED_MAXFCN;
  }

  /* Finish computations */
  ierr = PetscInfo2(ls,"%D function evals in line search, step = %g\n",(ls->nfeval+ls->nfgeval),(double)ls->step);CHKERRQ(ierr);

  /* Set new solution vector and compute gradient if needed */
  ierr = VecCopy(mt->work,x);CHKERRQ(ierr);
  if (!g_computed) {
    ierr = TaoLineSearchComputeGradient(ls,mt->work,g);CHKERRQ(ierr);
  }
  PetscFunctionReturn(0);
}
예제 #3
0
static PetscErrorCode TaoLineSearchApply_GPCG(TaoLineSearch ls, Vec x, PetscReal *f, Vec g, Vec s)
{
  TaoLineSearch_GPCG *neP = (TaoLineSearch_GPCG *)ls->data;
  PetscErrorCode     ierr;
  PetscInt           i;
  PetscBool          g_computed=PETSC_FALSE; /* to prevent extra gradient computation */
  PetscReal          d1,finit,actred,prered,rho, gdx;

  PetscFunctionBegin;
  /* ls->stepmin - lower bound for step */
  /* ls->stepmax - upper bound for step */
  /* ls->rtol     - relative tolerance for an acceptable step */
  /* ls->ftol     - tolerance for sufficient decrease condition */
  /* ls->gtol     - tolerance for curvature condition */
  /* ls->nfeval   - number of function evaluations */
  /* ls->nfeval   - number of function/gradient evaluations */
  /* ls->max_funcs  - maximum number of function evaluations */

  ls->reason = TAOLINESEARCH_CONTINUE_ITERATING;
  ls->step = ls->initstep;
  if (!neP->W2) {
    ierr = VecDuplicate(x,&neP->W2);CHKERRQ(ierr);
    ierr = VecDuplicate(x,&neP->W1);CHKERRQ(ierr);
    ierr = VecDuplicate(x,&neP->Gold);CHKERRQ(ierr);
    neP->x = x;
    ierr = PetscObjectReference((PetscObject)neP->x);CHKERRQ(ierr);
  } else if (x != neP->x) {
    ierr = VecDestroy(&neP->x);CHKERRQ(ierr);
    ierr = VecDestroy(&neP->W1);CHKERRQ(ierr);
    ierr = VecDestroy(&neP->W2);CHKERRQ(ierr);
    ierr = VecDestroy(&neP->Gold);CHKERRQ(ierr);
    ierr = VecDuplicate(x,&neP->W1);CHKERRQ(ierr);
    ierr = VecDuplicate(x,&neP->W2);CHKERRQ(ierr);
    ierr = VecDuplicate(x,&neP->Gold);CHKERRQ(ierr);
    ierr = PetscObjectDereference((PetscObject)neP->x);CHKERRQ(ierr);
    neP->x = x;
    ierr = PetscObjectReference((PetscObject)neP->x);CHKERRQ(ierr);
  }

  ierr = VecDot(g,s,&gdx);CHKERRQ(ierr);
   if (gdx > 0) {
     ierr = PetscInfo1(ls,"Line search error: search direction is not descent direction. dot(g,s) = %g\n",(double)gdx);CHKERRQ(ierr);
    ls->reason = TAOLINESEARCH_FAILED_ASCENT;
    PetscFunctionReturn(0);
  }
  ierr = VecCopy(x,neP->W2);CHKERRQ(ierr);
  ierr = VecCopy(g,neP->Gold);CHKERRQ(ierr);
  if (ls->bounded) {
    /* Compute the smallest steplength that will make one nonbinding variable  equal the bound */
    ierr = VecStepBoundInfo(x,s,ls->lower,ls->upper,&rho,&actred,&d1);CHKERRQ(ierr);
    ls->step = PetscMin(ls->step,d1);
  }
  rho=0; actred=0;

  if (ls->step < 0) {
    ierr = PetscInfo1(ls,"Line search error: initial step parameter %g< 0\n",(double)ls->step);CHKERRQ(ierr);
    ls->reason = TAOLINESEARCH_HALTED_OTHER;
    PetscFunctionReturn(0);
  }

  /* Initialization */
  finit = *f;
  for (i=0; i< ls->max_funcs; i++) {
    /* Force the step to be within the bounds */
    ls->step = PetscMax(ls->step,ls->stepmin);
    ls->step = PetscMin(ls->step,ls->stepmax);

    ierr = VecCopy(x,neP->W2);CHKERRQ(ierr);
    ierr = VecAXPY(neP->W2,ls->step,s);CHKERRQ(ierr);
    if (ls->bounded) {
      /* Make sure new vector is numerically within bounds */
      ierr = VecMedian(neP->W2,ls->lower,ls->upper,neP->W2);CHKERRQ(ierr);
    }

    /* Gradient is not needed here.  Unless there is a separate
       gradient routine, compute it here anyway to prevent recomputing at
       the end of the line search */
    if (ls->hasobjective) {
      ierr = TaoLineSearchComputeObjective(ls,neP->W2,f);CHKERRQ(ierr);
      g_computed=PETSC_FALSE;
    } else if (ls->usegts){
      ierr = TaoLineSearchComputeObjectiveAndGTS(ls,neP->W2,f,&gdx);CHKERRQ(ierr);
      g_computed=PETSC_FALSE;
    } else {
      ierr = TaoLineSearchComputeObjectiveAndGradient(ls,neP->W2,f,g);CHKERRQ(ierr);
      g_computed=PETSC_TRUE;
    }

    if (0 == i) {
        ls->f_fullstep = *f;
    }

    actred = *f - finit;
    ierr = VecCopy(neP->W2,neP->W1);CHKERRQ(ierr);
    ierr = VecAXPY(neP->W1,-1.0,x);CHKERRQ(ierr);    /* W1 = W2 - X */
    ierr = VecDot(neP->W1,neP->Gold,&prered);CHKERRQ(ierr);

    if (fabs(prered)<1.0e-100) prered=1.0e-12;
    rho = actred/prered;

    /*
       If sufficient progress has been obtained, accept the
       point.  Otherwise, backtrack.
    */

    if (actred > 0) {
      ierr = PetscInfo(ls,"Step resulted in ascent, rejecting.\n");CHKERRQ(ierr);
      ls->step = (ls->step)/2;
    } else if (rho > ls->ftol){
      break;
    } else{
      ls->step = (ls->step)/2;
    }

    /* Convergence testing */

    if (ls->step <= ls->stepmin || ls->step >= ls->stepmax) {
      ls->reason = TAOLINESEARCH_HALTED_OTHER;
      ierr = PetscInfo(ls,"Rounding errors may prevent further progress.  May not be a step satisfying\n");CHKERRQ(ierr);
      ierr = PetscInfo(ls,"sufficient decrease and curvature conditions. Tolerances may be too small.\n");CHKERRQ(ierr);
     break;
    }
    if (ls->step == ls->stepmax) {
      ierr = PetscInfo1(ls,"Step is at the upper bound, stepmax (%g)\n",(double)ls->stepmax);CHKERRQ(ierr);
      ls->reason = TAOLINESEARCH_HALTED_UPPERBOUND;
      break;
    }
    if (ls->step == ls->stepmin) {
      ierr = PetscInfo1(ls,"Step is at the lower bound, stepmin (%g)\n",(double)ls->stepmin);CHKERRQ(ierr);
      ls->reason = TAOLINESEARCH_HALTED_LOWERBOUND;
      break;
    }
    if ((ls->nfeval+ls->nfgeval) >= ls->max_funcs) {
      ierr = PetscInfo2(ls,"Number of line search function evals (%D) > maximum (%D)\n",ls->nfeval+ls->nfgeval,ls->max_funcs);CHKERRQ(ierr);
      ls->reason = TAOLINESEARCH_HALTED_MAXFCN;
      break;
    }
    if ((neP->bracket) && (ls->stepmax - ls->stepmin <= ls->rtol*ls->stepmax)){
      ierr = PetscInfo1(ls,"Relative width of interval of uncertainty is at most rtol (%g)\n",(double)ls->rtol);CHKERRQ(ierr);
      ls->reason = TAOLINESEARCH_HALTED_RTOL;
      break;
    }
  }
  ierr = PetscInfo2(ls,"%D function evals in line search, step = %g\n",ls->nfeval+ls->nfgeval,(double)ls->step);CHKERRQ(ierr);
  /* set new solution vector and compute gradient if necessary */
  ierr = VecCopy(neP->W2, x);CHKERRQ(ierr);
  if (ls->reason == TAOLINESEARCH_CONTINUE_ITERATING) {
    ls->reason = TAOLINESEARCH_SUCCESS;
  }
  if (!g_computed) {
    ierr = TaoLineSearchComputeGradient(ls,x,g);CHKERRQ(ierr);
  }
  PetscFunctionReturn(0);
}
예제 #4
0
파일: ipm.c 프로젝트: pombredanne/petsc
static PetscErrorCode TaoSolve_IPM(Tao tao)
{
  PetscErrorCode     ierr;
  TAO_IPM            *ipmP = (TAO_IPM*)tao->data;
  TaoConvergedReason reason = TAO_CONTINUE_ITERATING;
  PetscInt           its,i;
  PetscScalar        stepsize=1.0;
  PetscScalar        step_s,step_l,alpha,tau,sigma,phi_target;

  PetscFunctionBegin;
  /* Push initial point away from bounds */
  ierr = IPMInitializeBounds(tao);CHKERRQ(ierr);
  ierr = IPMPushInitialPoint(tao);CHKERRQ(ierr);
  ierr = VecCopy(tao->solution,ipmP->rhs_x);CHKERRQ(ierr);
  ierr = IPMEvaluate(tao);CHKERRQ(ierr);
  ierr = IPMComputeKKT(tao);CHKERRQ(ierr);
  ierr = TaoMonitor(tao,tao->niter++,ipmP->kkt_f,ipmP->phi,0.0,1.0,&reason);CHKERRQ(ierr);

  while (reason == TAO_CONTINUE_ITERATING) {
    tao->ksp_its=0;
    ierr = IPMUpdateK(tao);CHKERRQ(ierr);
    /*
       rhs.x    = -rd
       rhs.lame = -rpe
       rhs.lami = -rpi
       rhs.com  = -com
    */

    ierr = VecCopy(ipmP->rd,ipmP->rhs_x);CHKERRQ(ierr);
    if (ipmP->me > 0) {
      ierr = VecCopy(ipmP->rpe,ipmP->rhs_lamdae);CHKERRQ(ierr);
    }
    if (ipmP->nb > 0) {
      ierr = VecCopy(ipmP->rpi,ipmP->rhs_lamdai);CHKERRQ(ierr);
      ierr = VecCopy(ipmP->complementarity,ipmP->rhs_s);CHKERRQ(ierr);
    }
    ierr = IPMGatherRHS(tao,ipmP->bigrhs,ipmP->rhs_x,ipmP->rhs_lamdae,ipmP->rhs_lamdai,ipmP->rhs_s);CHKERRQ(ierr);
    ierr = VecScale(ipmP->bigrhs,-1.0);CHKERRQ(ierr);

    /* solve K * step = rhs */
    ierr = KSPSetOperators(tao->ksp,ipmP->K,ipmP->K);CHKERRQ(ierr);
    ierr = KSPSolve(tao->ksp,ipmP->bigrhs,ipmP->bigstep);CHKERRQ(ierr);

    ierr = IPMScatterStep(tao,ipmP->bigstep,tao->stepdirection,ipmP->ds,ipmP->dlamdae,ipmP->dlamdai);CHKERRQ(ierr);
    ierr = KSPGetIterationNumber(tao->ksp,&its);CHKERRQ(ierr);
    tao->ksp_its += its;
    tao->ksp_tot_its+=its;
     /* Find distance along step direction to closest bound */
    if (ipmP->nb > 0) {
      ierr = VecStepBoundInfo(ipmP->s,ipmP->ds,ipmP->Zero_nb,ipmP->Inf_nb,&step_s,NULL,NULL);CHKERRQ(ierr);
      ierr = VecStepBoundInfo(ipmP->lamdai,ipmP->dlamdai,ipmP->Zero_nb,ipmP->Inf_nb,&step_l,NULL,NULL);CHKERRQ(ierr);
      alpha = PetscMin(step_s,step_l);
      alpha = PetscMin(alpha,1.0);
      ipmP->alpha1 = alpha;
    } else {
      ipmP->alpha1 = alpha = 1.0;
    }

    /* x_aff = x + alpha*d */
    ierr = VecCopy(tao->solution,ipmP->save_x);CHKERRQ(ierr);
    if (ipmP->me > 0) {
      ierr = VecCopy(ipmP->lamdae,ipmP->save_lamdae);CHKERRQ(ierr);
    }
    if (ipmP->nb > 0) {
      ierr = VecCopy(ipmP->lamdai,ipmP->save_lamdai);CHKERRQ(ierr);
      ierr = VecCopy(ipmP->s,ipmP->save_s);CHKERRQ(ierr);
    }

    ierr = VecAXPY(tao->solution,alpha,tao->stepdirection);CHKERRQ(ierr);
    if (ipmP->me > 0) {
      ierr = VecAXPY(ipmP->lamdae,alpha,ipmP->dlamdae);CHKERRQ(ierr);
    }
    if (ipmP->nb > 0) {
      ierr = VecAXPY(ipmP->lamdai,alpha,ipmP->dlamdai);CHKERRQ(ierr);
      ierr = VecAXPY(ipmP->s,alpha,ipmP->ds);CHKERRQ(ierr);
    }

    /* Recompute kkt to find centering parameter sigma = (new_mu/old_mu)^3 */
    if (ipmP->mu == 0.0) {
      sigma = 0.0;
    } else {
      sigma = 1.0/ipmP->mu;
    }
    ierr = IPMComputeKKT(tao);CHKERRQ(ierr);
    sigma *= ipmP->mu;
    sigma*=sigma*sigma;

    /* revert kkt info */
    ierr = VecCopy(ipmP->save_x,tao->solution);CHKERRQ(ierr);
    if (ipmP->me > 0) {
      ierr = VecCopy(ipmP->save_lamdae,ipmP->lamdae);CHKERRQ(ierr);
    }
    if (ipmP->nb > 0) {
      ierr = VecCopy(ipmP->save_lamdai,ipmP->lamdai);CHKERRQ(ierr);
      ierr = VecCopy(ipmP->save_s,ipmP->s);CHKERRQ(ierr);
    }
    ierr = IPMComputeKKT(tao);CHKERRQ(ierr);

    /* update rhs with new complementarity vector */
    if (ipmP->nb > 0) {
      ierr = VecCopy(ipmP->complementarity,ipmP->rhs_s);CHKERRQ(ierr);
      ierr = VecScale(ipmP->rhs_s,-1.0);CHKERRQ(ierr);
      ierr = VecShift(ipmP->rhs_s,sigma*ipmP->mu);CHKERRQ(ierr);
    }
    ierr = IPMGatherRHS(tao,ipmP->bigrhs,NULL,NULL,NULL,ipmP->rhs_s);CHKERRQ(ierr);

    /* solve K * step = rhs */
    ierr = KSPSetOperators(tao->ksp,ipmP->K,ipmP->K);CHKERRQ(ierr);
    ierr = KSPSolve(tao->ksp,ipmP->bigrhs,ipmP->bigstep);CHKERRQ(ierr);

    ierr = IPMScatterStep(tao,ipmP->bigstep,tao->stepdirection,ipmP->ds,ipmP->dlamdae,ipmP->dlamdai);CHKERRQ(ierr);
    ierr = KSPGetIterationNumber(tao->ksp,&its);CHKERRQ(ierr);
    tao->ksp_its += its;
    tao->ksp_tot_its+=its;
    if (ipmP->nb > 0) {
      /* Get max step size and apply frac-to-boundary */
      tau = PetscMax(ipmP->taumin,1.0-ipmP->mu);
      tau = PetscMin(tau,1.0);
      if (tau != 1.0) {
        ierr = VecScale(ipmP->s,tau);CHKERRQ(ierr);
        ierr = VecScale(ipmP->lamdai,tau);CHKERRQ(ierr);
      }
      ierr = VecStepBoundInfo(ipmP->s,ipmP->ds,ipmP->Zero_nb,ipmP->Inf_nb,&step_s,NULL,NULL);CHKERRQ(ierr);
      ierr = VecStepBoundInfo(ipmP->lamdai,ipmP->dlamdai,ipmP->Zero_nb,ipmP->Inf_nb,&step_l,NULL,NULL);CHKERRQ(ierr);
      if (tau != 1.0) {
        ierr = VecCopy(ipmP->save_s,ipmP->s);CHKERRQ(ierr);
        ierr = VecCopy(ipmP->save_lamdai,ipmP->lamdai);CHKERRQ(ierr);
      }
      alpha = PetscMin(step_s,step_l);
      alpha = PetscMin(alpha,1.0);
    } else {
      alpha = 1.0;
    }
    ipmP->alpha2 = alpha;
    /* TODO make phi_target meaningful */
    phi_target = ipmP->dec * ipmP->phi;
    for (i=0; i<11;i++) {
      ierr = VecAXPY(tao->solution,alpha,tao->stepdirection);CHKERRQ(ierr);
      if (ipmP->nb > 0) {
        ierr = VecAXPY(ipmP->s,alpha,ipmP->ds);CHKERRQ(ierr);
        ierr = VecAXPY(ipmP->lamdai,alpha,ipmP->dlamdai);CHKERRQ(ierr);
      }
      if (ipmP->me > 0) {
        ierr = VecAXPY(ipmP->lamdae,alpha,ipmP->dlamdae);CHKERRQ(ierr);
      }

      /* update dual variables */
      if (ipmP->me > 0) {
        ierr = VecCopy(ipmP->lamdae,tao->DE);CHKERRQ(ierr);
      }

      ierr = IPMEvaluate(tao);CHKERRQ(ierr);
      ierr = IPMComputeKKT(tao);CHKERRQ(ierr);
      if (ipmP->phi <= phi_target) break;
      alpha /= 2.0;
    }

    ierr = TaoMonitor(tao,tao->niter,ipmP->kkt_f,ipmP->phi,0.0,stepsize,&reason);CHKERRQ(ierr);
    tao->niter++;
  }
  PetscFunctionReturn(0);
}