/*
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   SLEPc - Scalable Library for Eigenvalue Problem Computations
   Copyright (c) 2002-, Universitat Politecnica de Valencia, Spain

   This file is part of SLEPc.
   SLEPc is distributed under a 2-clause BSD license (see LICENSE).
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*/

#pragma once

/* IntervalOptions structure used by GetIntervals */
struct _n_FILTLAN_IOP {
  PetscReal   intervalWeights[5];  /* weight of the subintervals (5 in mid-pass, 3 in high-pass) */
  PetscReal   transIntervalRatio;  /* the (relative) length of transition interval */
  PetscBool   reverseInterval;     /* whether to reverse the interval or not; effective only for mid-pass filters */
  PetscReal   initialPlateau;      /* initial plateau relative to the length of interval */
  PetscReal   plateauShrinkRate;   /* the rate at which the plateau shrinks at each iteration */
  PetscReal   initialShiftStep;    /* initial shift step relative to the length of interval */
  PetscReal   shiftStepExpanRate;  /* the rate at which the shift step expands */
  PetscInt    maxInnerIter;        /* maximum number of inner iterations to determine the (transition) intervals */
  PetscReal   yLimitTol;           /* tolerance allowed for |p(inta)-p(intb)| in a mid-pass filter p(x) */
  PetscInt    maxOuterIter;        /* maximum number of outer iterations to determine the (transition) intervals */
  PetscInt    numGridPoints;       /* number of grid points, used to measure the maximum p(z) for z not in the interval*/
  PetscReal   yBottomLine;         /* p(x) should be greater than this value for x in the interval */
  PetscReal   yRippleLimit;        /* limit of height of ripples relative to the bottom of polynomial values */
};
typedef struct _n_FILTLAN_IOP *FILTLAN_IOP;

/* PolynomialFilterInfo structure filled by GetIntervals */
struct _n_FILTLAN_PFI {
  PetscInt    filterType;          /* 1 = high-pass filter (or low-pass filter with conversion); 2 = mid-pass filter */
  PetscInt    filterOK;            /* 0 = no acceptable found; 1 = OK filter found; 2 = optimal filter found */
  PetscReal   filterQualityIndex;  /* between 0.0 and 1.0; the higher the better quality of the filter */
  PetscInt    numIter;             /* number of iterations to get the (transition) intervals */
  PetscInt    totalNumIter;        /* total number of iterations performed */
  PetscReal   yLimit;              /* lowest polynomial value P(z) for z in the interval [a1,b1] of desired eigenvalues */
  PetscReal   ySummit;             /* height of (highest, if more than one) summit in interval [a1,b1] of desired evals */
  PetscInt    numLeftSteps;        /* number of steps moving leftward */
  PetscReal   yLeftSummit;         /* height of highest summit in the left-hand side of the interval of desired evals */
  PetscReal   yLeftBottom;         /* height of lowest bottom in the left-hand side of the interval of desired evals */
  PetscReal   yLimitGap;           /* |p(a1)-p(b1)|, where [a1,b1] is the interval of desired eigenvalues */
  PetscInt    numRightSteps;       /* number of steps moving rightward */
  PetscReal   yRightSummit;        /* height of highest summit in the right-hand side of the interval of desired evals */
  PetscReal   yRightBottom;        /* height of lowest bottom in the right-hand side of the interval of desired evals */
};
typedef struct _n_FILTLAN_PFI *FILTLAN_PFI;

typedef struct {
  /* user options */
  PetscReal   inta,intb;           /* bounds of the interval of desired eigenvalues */
  PetscReal   left,right;          /* approximate left and right bounds of the interval containing all eigenvalues */
  PetscInt    polyDegree;          /* degree of s(z), with z*s(z) the polynomial filter */
  PetscInt    baseDegree;          /* left and right degrees of the base filter for each interval */
  FILTLAN_IOP opts;                /* interval options */
  /* internal variables */
  FILTLAN_PFI filterInfo;          /* polynomial filter info */
  PetscReal   frame[4];            /* outer and inner intervals:
                                      [frame[0],frame[3]] (tightly) contains all eigenvalues
                                      [frame[1],frame[2]] is the interval in which the eigenvalues are sought */
  PetscReal   intervals[6];        /* the range of eigenvalues is partitioned into intervals which determine
                                      the base filter approximated by a polynomial filter;
                                      the j-th interval is [intervals(j),intervals(j+1)) */
  PetscReal   intervals2[6];       /* modified intervals */
  PetscReal   *baseFilter;         /* coefficients of the base filter (a piecewise polynomial) */
  Mat         T;                   /* the matrix used to build the filter */
  PetscBool   filtch;              /* filter parameters have changed since last setup */
  Mat         *W;                  /* work matrices for the matrix-matrix application of the filter */
  PetscInt    nW;                  /* number of W matrices */
} ST_FILTER;

SLEPC_INTERN PetscErrorCode STFilter_FILTLAN_Apply(ST,Vec,Vec);
SLEPC_INTERN PetscErrorCode STFilter_FILTLAN_setFilter(ST,Mat*);
