## File: PDL::CCS::Compat.pm
## Author: Bryan Jurish <moocow@cpan.org>
## Description: backwards-compatibility hacks for PDL::CCS

package PDL::CCS::Compat;
use PDL;
use PDL::VectorValued;
use PDL::CCS::Config qw(ccs_indx);
use PDL::CCS::Functions;
use PDL::CCS::Utils;
use PDL::CCS::Ufunc;
use PDL::CCS::Ops;
use strict;

our $VERSION = '1.23.18'; ##-- update with perl-reversion from Perl::Version module
our @ISA = ('PDL::Exporter');
our @ccs_binops = (qw(plus minus mult divide modulo power),
		   qw(gt ge lt le eq ne spaceship),
		   qw(and2 or2 xor shiftleft shiftright),
		  );
our @EXPORT_OK =
  (
   ##
   ##-- Encoding
   qw(ccs_encode_compat),
   qw(ccsencode ccsencode_nz ccsencodefull ccsencodefull_nz),
   qw(ccsencodea ccsencode_naz ccsencodefulla ccsencodefull_naz),
   qw(ccsencodeg ccsencode_g ccsencodefullg ccsencodefull_g),
   qw(ccsencodei ccsencode_i ccsencodefulli ccsencodefull_i),
   qw(ccsencodei2d ccsencode_i2d ccsencodefulli2d ccsencodefull_i2d),
   ##
   ##-- Decoding
   qw(_ccsdecodecols ccsdecodecols),
   qw(ccsdecode ccsdecodefull),
   qw(ccsdecode_g ccsdecodeg ccsdecodefull_g ccsdecodefullg),
   ##
   ##-- Indexing
   qw(ccsiNDtonzi ccsi2dtonzi ccsitonzi),
   qw(ccswhichND ccswhich2d ccswhichfull ccswhich),
   qw(ccstranspose ccstransposefull),
   ##
   ##-- Lookup
   qw(ccsget ccsget2d),
   ##
   ##-- Operations
   (map {("ccs${_}_cv","ccs${_}_rv")} (@ccs_binops,qw(add diff))),
   ##
   ##-- Ufuncs
   (map {("ccs${_}","ccs${_}t")} qw(sumover prodover)),
  );
our %EXPORT_TAGS =
  (
   Func => [@EXPORT_OK],               ##-- respect PDL conventions (hopefully)
  );

##======================================================================
## pod: headers
=pod

=head1 NAME

PDL::CCS::Compat - Backwards-compatibility module for PDL::CCS

=head1 SYNOPSIS

 use PDL;
 use PDL::CCS::Compat;

 ##-- source pdl
 $a = random($N=8,$M=7);

 ##---------------------------------------------------------------------
 ## Non-missing value counts
 $nnz    = $a->flat->nnz;         ##-- "missing" == 0
 $nnaz   = $a->flat->nnza(1e-6);  ##-- "missing" ~= 0
 #$ngood = $a->ngood;             ##-- "missing" == BAD (see PDL::Bad)

 ##---------------------------------------------------------------------
 ## CCS Encoding
 ($ptr,$rowids,$vals) = ccsencode_nz ($a);             # missing == 0
 ($ptr,$rowids,$vals) = ccsencode_naz($a,$eps);        # missing ~= 0
 ($ptr,$rowids,$vals) = ccsencode_g  ($a);             # missing == BAD
 ($ptr,$rowids,$vals) = ccsencode_i  ($i,$ivals,$N);   # generic flat
 ($ptr,$rowids,$vals) = ccsencode_i2d($xi,$yi,$ivals); # generic 2d

 ##---------------------------------------------------------------------
 ## CCS Decoding
 $cols = ccsdecodecols($ptr,$rowids,$nzvals, $xvals
 $a2   = ccsdecode  ($ptr,$rowids,$vals);              # missing == 0
 $a2   = ccsdecode_g($ptr,$rowids,$vals);              # missing == BAD

 ##---------------------------------------------------------------------
 ## CCS Index Conversion
 $nzi  = ccsitonzi  ($ptr,$rowids, $ix,     $missing); # ix => nzi
 $nzi  = ccsi2dtonzi($ptr,$rowids, $xi,$yi, $missing); # 2d => nzi

 $ix       = ccswhich  ($ptr,$rowids,$vals);           # CCS => ix
 ($xi,$yi) = ccswhichND($ptr,$rowids,$vals);           # CCS => 2d
 $xyi      = ccswhichND($ptr,$rowids,$vals);           # ...as scalar

 ##---------------------------------------------------------------------
 ## CCS Lookup

 $ixvals = ccsget  ($ptr,$rowids,$vals, $ix,$missing);     # ix => values
 $ixvals = ccsget2d($ptr,$rowids,$vals, $xi,$yi,$missing); # 2d => values

 ##---------------------------------------------------------------------
 ## CCS Operations
 ($ptrT,$rowidsT,$valsT) = ccstranspose($ptr,$rowids,$vals); # CCS<->CRS

 ##---------------------------------------------------------------------
 ## Vector Operations, by column
 $nzvals_out = ccsadd_cv ($ptr,$rowids,$nzvals, $colvec);
 $nzvals_out = ccsdiff_cv($ptr,$rowids,$nzvals, $colvec);
 $nzvals_out = ccsmult_cv($ptr,$rowids,$nzvals, $colvec);
 $nzvals_out = ccsdiv_cv ($ptr,$rowids,$nzvals, $colvec);

 ##---------------------------------------------------------------------
 ## Vector Operations, by row
 $nzvals_out = ccsadd_rv ($ptr,$rowids,$nzvals, $rowvec);
 $nzvals_out = ccsdiff_rv($ptr,$rowids,$nzvals, $rowvec);
 $nzvals_out = ccsmult_rv($ptr,$rowids,$nzvals, $rowvec);
 $nzvals_out = ccsdiv_rv ($ptr,$rowids,$nzvals, $rowvec);

 ##---------------------------------------------------------------------
 ## Scalar Operations
 $nzvals_out = $nzvals * 42;  # ... or whatever

 ##---------------------------------------------------------------------
 ## Accumulators
 $rowsumover  = ccssumover ($ptr,$rowids,$nzvals); ##-- like $a->sumover()
 $colsumovert = ccssumovert($ptr,$rowids,$nzvals); ##-- like $a->xchg(0,1)->sumover

=cut

##======================================================================
## Encoding
=pod

=head1 Encoding

=cut

##---------------------------------------------------------------
## Encoding: generic

=pod

=head2 ccs_encode_compat

=for sig

  Signature: (indx awhich(2,Nnz); avals(Nnz);
              indx $N; indx $M;
              indx [o]ptr(N); indx [o]rowids(Nnz); [o]nzvals(Nnz))

Generic wrapper for backwards-compatible ccsencode() variants.

=cut

*ccs_encode_compat = \&PDL::ccs_encode_compat;
sub PDL::ccs_encode_compat {
  my ($aw,$avals,$N,$M,$ptr,$rowids,$nzvals) = @_;

  $N = $aw->slice("(0),")->max+1 if (!defined($N));
  $M = $aw->slice("(1),")->max+1 if (!defined($M));

  my ($ptr1,$awi) = ccs_encode_pointers($aw->slice("(0),"), $N);

  if (defined($ptr))    { $ptr .= $ptr1->slice("0:-2"); }
  else                  { $ptr  = $ptr1->slice("0:-2"); $ptr->sever; }

  if (defined($rowids)) { $rowids .= $aw->slice("(1),")->index($awi); }
  else                  { $rowids  = $aw->slice("(1),")->index($awi); $rowids->sever; }

  if (defined($nzvals)) { $nzvals .= $avals->index($awi); }
  else                  { $nzvals  = $avals->index($awi); $nzvals->sever; }

  return ($ptr,$rowids,$nzvals);
}

##---------------------------------------------------------------
## Encoding: MISSING=zero
=pod

=head2 ccsencode

=head2 ccsencode_nz

=for sig

  Signature: (a(N,M); indx [o]ptr(N); indx [o]rowids(Nnz); [o]nzvals(Nnz))

Encodes matrix $a() in compressed column format, interpreting zeroes
as "missing" values.

Allocates output vectors if required.

=cut

*ccsencode
  = *ccsencodefull      = *ccsencodefull_nz
  = *PDL::ccsencode     = *PDL::ccsencode_nz
  = *PDL::ccsencodefull = *PDL::ccsencodefull_nz
  = \&ccsencode_nz;
sub ccsencode_nz {
  #my ($a,$ptr,$rowids,$nzvals) = @_;
  my $a  = shift;
  $a     = $a->clump(1+$a->ndims-2); ##-- clump(-2) broken in PDL-2.0.14
  my $aw = $a->whichND;
  return ccs_encode_compat($aw, $a->indexND($aw), $a->dims, @_);
}

##---------------------------------------------------------------
## Encoding: MISSING=ZERO (approx)
=pod

=head2 ccsencodea

=head2 ccsencode_naz

=for sig

  Signature: (a(N,M); eps(); indx [o]ptr(N); indx [o]rowids(Nnz); [o]nzvals(Nnz))

Encodes matrix $a() in CCS format interpreting approximate zeroes as "missing" values.
This function is just like ccsencode_nz(), but uses the tolerance parameter
$eps() to determine which elements are to be treated as zeroes.

Allocates output vectors if required.

=cut

*ccsencodea
  = *ccsencodefulla      = *ccsencodefull_naz
  = *PDL::ccsencodea     = *PDL::ccsencode_naz
  = *PDL::ccsencodefulla = *PDL::ccsencodefull_naz
  = \&ccsencode_naz;
sub ccsencode_naz {
  #my ($a,$eps,$ptr,$rowids,$nzvals) = @_;
  my $a   = shift;
  my $eps = shift;
  $a      = $a->clump(1+$a->ndims-2); ##-- clump(-2) is broken in PDL-2.014
  my $aw  = $a->approx(0,$eps)->inplace->not->whichND;          ##-- FIXME: optimize
  return ccs_encode_compat($aw, $a->indexND($aw), $a->dims, @_);
}

##---------------------------------------------------------------
## Encoding: MISSING=BAD
=pod

=head2 ccsencodeg

=head2 ccsencode_g

=for sig

  Signature: (a(N,M); indx [o]ptr(N); indx [o]rowids(Nnz); [o]nzvals(Nnz))

Encodes matrix $a() in CCS format interpreting BAD values
as "missing".  Requires bad-value support built into PDL.

Allocates output vectors if required.

=cut

*ccsencodeg
  = *ccsencodefullg      = *ccsencodefull_g
  = *PDL::ccsencodeg     = *PDL::ccsencode_g
  = *PDL::ccsencodefullg = *PDL::ccsencodefull_g
  = \&ccsencode_g;
sub ccsencode_g {
  #my ($a,$ptr,$rowids,$nzvals) = @_;
  my $a     = shift;
  $a        = $a->clump(1+$a->ndims-2);  ##-- clump(-2) is broken in PDL-v2.014
  my $amask = zeroes(byte,$a->dims);
  $a->isgood($amask);
  my $aw    = $amask->whichND;
  return ccs_encode_compat($aw, $a->indexND($aw), $a->dims, @_);
}

##---------------------------------------------------------------
## Encoding: from flat index
=pod

=head2 ccsencode_i

=for sig

  Signature: (indx ix(Nnz); nzvals(Nnz); indx $N; int [o]ptr(N); indx [o]rowids(Nnz); [o]nzvals_enc(Nnz))

General-purpose CCS encoding method for flat indices.
Encodes values $nzvals() from flat-index locations $ix() into a CCS matrix ($ptr(), $rowids(), $nzvals_enc()).

Allocates output vectors if required.

$N (~ $a-E<gt>dim(0)) must be specified.

=cut

*ccsencodei
  = *ccsencodefulli      = *ccsencodefull_i
  = *PDL::ccsencodei     = *PDL::ccsencode_i
  = *PDL::ccsencodefulli = *PDL::ccsencodefull_i
  = \&ccsencode_i;
sub ccsencode_i {
  #my ($iflat,$avals,$N_optional,$ptr,$rowids,$nzvals) = @_;
  my ($iflat,$avals) = splice(@_,0,2);
  my $N  = defined($_[0]) && (!ref($_[0]) || $_[0]->nelem==1) ? shift : $_[0]->nelem;
  my $aw = ($iflat % $N)->cat($iflat/$N)->xchg(0,1);
  return ccs_encode_compat($aw, $avals, $N, undef, @_);
}


##---------------------------------------------------------------
## Encoding: from 2d index
=pod

=head2 ccsencode_i2d

=for sig

  Signature: (
              indx    xvals(Nnz)     ;
              indx    yvals(Nnz)     ;
                      nzvals(Nnz)    ;
              indx    $N             ; ##-- optional
              indx [o]ptr(N)         ;
              indx [o]rowids(Nnz)    ;
                   [o]nzvals_enc(Nnz);
             )

General-purpose encoding method.
Encodes values $nzvals() from 2d-index locations ($xvals(), $yvals()) in an $N-by-(whatever) PDL
into a CCS matrix $ptr(), $rowids(), $nzvals_enc().

Allocates output vectors if required.
If $N is omitted, it defaults to the maximum column index given in $xvals().

=cut

*ccsencodei2d
  = *ccsencodefulli2d      = *ccsencodefull_i2d
  = *PDL::ccsencodei2d     = *PDL::ccsencode_i2d
  = *PDL::ccsencodefulli2d = *PDL::ccsencodefull_i2d
  = \&ccsencode_i2d;
sub ccsencode_i2d {
  #my ($whichx,$whichy,$avals,$N_optional,$ptr,$rowids,$nzvals) = @_;
  my ($whichx,$whichy,$avals) = splice(@_, 0, 3);
  my $aw = $whichx->cat($whichy)->xchg(0,1);
  my $N  = defined($_[0]) && (!ref($_[0]) || $_[0]->nelem==1) ? shift : ($whichx->max+1);
  return ccs_encode_compat($aw, $avals, $N, undef, @_);
}

##======================================================================
## Decoding
=pod

=head1 Decoding

=cut

##---------------------------------------------------------------
## Decoding: column-wise

=pod

=head2 ccsdecodecols

=for sig

  Signature: (
              indx   ptr    (N)  ;
              indx   rowids (Nnz);
                     nzvals (Nnz);
              indx   xvals  (I)  ; # default=sequence($N)
                     missing()   ; # default=0
                     M      ()   ; # default=rowids->max+1
                  [o]cols   (I,M); # default=new
              )

Extract dense columns from a CCS-encoded matrix (no dataflow).
Allocates output matrix if required.
If $a(N,M) was the dense source matrix for the CCS-encoding, and
if missing values are zeros, then the
following two calls are equivalent (modulo data flow):

  $cols = $a->dice_axis(1,$col_ix);
  $cols = ccsdecodecols($ptr,$rowids,$nzvals, $col_ix,0);

=cut


*PDL::_ccsdecodecols = \&_ccsdecodecols;
#Pars => 'indx ptr(N); indx rowids(Nnz); nzvals(Nnz); indx col_ix(I); missing(); [o]cols(I,M);',
sub _ccsdecodecols {
  ccsdecodecols(@_[0,1,2], $_[3],$_[4], undef, $_[5]);
}
*PDL::ccsdecodecols = \&ccsdecodecols;
sub ccsdecodecols {
  my ($ptr,$rowids,$nzvals, $coli,$missing,$M, $cols) = @_;
  $coli    = sequence(ccs_indx,$ptr->dim(0)) if (!defined($coli));
  $coli    = pdl(ccs_indx,$coli)             if (!ref($coli));
  my $ptr1 = zeroes(ccs_indx,$ptr->nelem+1);
  $ptr1->slice("0:-2") .= $ptr;
  $ptr1->set(-1 => $nzvals->nelem);
  $M = $rowids->max+1 if (!defined($M));
  my ($ptrix,$nzix) = ccs_decode_pointer($ptr1,$coli);
  my $which = $ptrix->cat($rowids->index($nzix))->xchg(0,1);
  if (!defined($cols)) {
    $cols = ccs_decode($which, $nzvals->index($nzix), $missing, [$coli->nelem,$M]);
    $cols->sever; ##-- compat
  } else {
    ccs_decode($which, $nzvals->index($nzix), $missing, [$coli->nelem,$M], $cols);
  }
  return $cols;
}


##---------------------------------------------------------------
## Decoding: MISSING=0
=pod

=head2 ccsdecode

=for sig

  Signature: (indx ptr(N); indx rowids(Nnz); nzvals(Nnz); $M; [o]dense(N,M))

Decodes compressed column format vectors $ptr(), $rowids(), and $nzvals()
into dense output matrix $a().
Allocates the output matrix if required.

Note that if the original
matrix (pre-encoding) contained trailing rows with no nonzero elements,
such rows will not be allocated by this method (unless you specify either $M or $dense).
In such cases, you might prefer to call ccsdecodecols() directly.

=cut

*PDL::ccsdecodefull = \&ccsdecodefull; ##-- (indx ptr(N); indx rowids(Nnz); nzvals(Nnz); [o]dense(N,M))
sub ccsdecodefull { ccsdecodecols(@_[0,1,2], undef,0,undef, @_[3..$#_]); }

*PDL::ccsdecode = \&ccsdecode;
sub ccsdecode {
  my ($ptr,$rowids,$nzvals, $M, $dense)=@_;
  if (!defined($dense)) {
    ##-- check for old calling convention (is $M a multi-dim PDL?)
    if (ref($M) && UNIVERSAL::isa($M, 'PDL') && $M->dim(0)==$ptr->dim(0)) {
      $dense = $M;
    } else {
      $M     = $rowids->max+1 if (!defined($M));
      $dense = zeroes($nzvals->type,$ptr->dim(0),$M);
    }
  }
  ccsdecodecols($ptr,$rowids,$nzvals, undef,0,$M, $dense);
  return $dense;
}


##---------------------------------------------------------------
## Decoding: MISSING=BAD
=pod

=head2 ccsdecode_g

=for sig

  Signature: (indx ptr(N); indx rowids(Nnz); nzvals(Nnz); $M; [o]dense(N,M))

Convenience method.
Like ccsdecode() but sets "missing" values to BAD.

=cut

*ccsdecodefullg = *PDL::ccsdecodefullg = *PDL::ccsdecodefull_g = \&ccsdecodefull_g;
sub ccsdecodefull_g {
  my $badval = pdl($_[2]->type,0)->setvaltobad(0);
  ccsdecodecols(@_[0,1,2], undef,$badval,undef,undef, @_[3..$#_]);
}

*ccsdecodeg = *PDL::ccsdecodeg = *PDL::ccsdecode_g = \&ccsdecode_g;
sub ccsdecode_g {
  my ($ptr,$rowids,$nzvals, $M, $dense)=@_;
  if (!defined($dense)) {
    ##-- check for old calling convention (is $M a multi-dim PDL?)
    if (ref($M) && UNIVERSAL::isa($M, 'PDL') && $M->dim(0)==$ptr->dim(0)) {
      $dense = $M;
    } else {
      $M     = $rowids->max+1 if (!defined($M));
      $dense = zeroes($nzvals->type,$ptr->dim(0),$M);
    }
  }
  my $badval = pdl($nzvals->type,0)->setvaltobad(0);
  ccsdecodecols($ptr,$rowids,$nzvals, undef,$badval,$M, $dense);
  return $dense;
}


##======================================================================
## Index Conversion
##======================================================================
=pod

=head1 Index Conversion

=cut

##------------------------------------------------------
## ccsiNDtonzi() : index conversion: N-dimensional

=pod

=for sig

  Signature: (indx ptr(N); indx rowids(Nnz); indx ind(2,I); indx missing(); indx [o]nzix(I))

=head2 ccsiNDtonzi

Convert N-dimensional index values $ind() appropriate for a dense matrix (N,M)
into indices $nzix() appropriate for the $rowids() and/or $nzvals() components
of the CCS-encoded matrix ($ptr(),$rowids(),$nzvals()).
Missing values are returned in $nzix() as $missing().

=cut

*PDL::ccsiNDtonzi = \&ccsiNDtonzi;
sub ccsiNDtonzi {
  my ($ptr,$rowids,$ind, $missing, $nzix) = @_;
  my ($ptri,$ptrnzi) = ccs_decode_pointer($ptr->append($rowids->nelem));
  my $ccswnd         = $ptri->cat($rowids->index($ptrnzi))->xchg(0,1)->vv_qsortvec;
  $nzix              = $ind->vsearchvec($ccswnd);
  my $nzix_mask      = ($ind==$ccswnd->dice_axis(1,$nzix))->andover;
  $nzix_mask->inplace->not;
  #(my $tmp = $nzix->where($nzix_mask)) .= $missing; ##-- fix "Can't modify non-lvalue subroutine call" in 5.15.x (perl bug #107366)
  $nzix->where($nzix_mask) .= $missing;
  return $nzix;
}

##------------------------------------------------------
## ccsi2dtonzi() : index conversion: 2d

=pod

=head2 ccsi2dtonzi

=for sig

  Signaure: (indx ptr(N); indx rowids(Nnz); indx col_ix(I); indx row_ix(I); indx missing(); indx [o]nzix(I))

Convert 2d index values $col_ix() and $row_ix() appropriate for a dense matrix (N,M)
into indices $nzix() appropriate for the $rowids() and/or $nzvals() components
of the CCS-encoded matrix ($ptr(),$rowids(),$nzvals()).
Missing values are returned in $nzix() as $missing().

=cut

*PDL::ccsi2dtonzi = \&ccsi2dtonzi;
sub ccsi2dtonzi {
  my ($ptr,$rowids,$xi,$yi, $missing, $nzix) = @_;
  return ccsiNDtonzi($ptr,$rowids, $xi->cat($yi)->xchg(0,1), $missing,$nzix);
}


##------------------------------------------------------
## ccsitonzi() : index conversion: flat

=pod

=for sig

  Signature: (indx ptr(N); indx rowids(Nnz); indx ix(I); indx missing(); indx [o]nzix(I))

=head2 ccsitonzi

Convert flat index values $ix() appropriate for a dense matrix (N,M)
into indices $nzix() appropriate for the $rowids() and/or $nzvals() components
of the CCS-encoded matrix ($ptr(),$rowids(),$nzvals()).
Missing values are returned in $nzix() as $missing().

=cut

*PDL::ccsitonzi = \&ccsitonzi;
sub ccsitonzi {
  my ($ptr,$rowids,$ix, $missing, $nzix) = @_;
  my $dummy    = pdl(byte,0)->slice("*".($ptr->dim(0)).",*".($rowids->max+1));
  my ($xi,$yi) = $dummy->one2nd($ix);
  return ccsiNDtonzi($ptr,$rowids, $xi->cat($yi)->xchg(0,1), $missing,$nzix);
}



##------------------------------------------------------
## ccswhichND: get indices (N-dimensional)

=pod

=head2 ccswhichND

=head2 ccswhich2d

=head2 ccswhichfull

=for sig

  Signature: (indx ptr(N); indx rowids(Nnz); nzvals(Nnz); indx [o]which_cols(Nnz); indx [o]which_rows(Nnz)',

In scalar context, returns concatenation of $which_cols() and $which_rows(),
similar to the builtin whichND().  Note however that ccswhichND() may return
its index PDLs sorted in a different order than the builtin whichND() method
for dense matrices.  Use the qsort() or qsorti() methods if you need sorted index PDLs.

=cut

*ccswhich2d = *PDL::which2d = *PDL::ccswhichND
  = *ccswhichfull = *PDL::ccswhichfull
  = \&ccswhichND;
sub ccswhichND {
  my ($ptr,$rowids,$nzvals, $which_cols,$which_rows) = @_;
  my ($ptrnzi);
  ($which_cols,$ptrnzi) = ccs_decode_pointer($ptr->append($rowids->nelem),
					     sequence(ccs_indx, $ptr->nelem),
					     $which_cols
					    );
  $which_rows  = zeroes(ccs_indx, $rowids->nelem) if (!defined($which_rows));
  $which_rows .= $rowids->index($ptrnzi);
  return wantarray ? ($which_cols,$which_rows) : $which_cols->cat($which_rows)->xchg(0,1);
}


##------------------------------------------------------
## ccswhich(): get indices (flat)

=head2 ccswhich

=for sig

  Signature: (indx ptr(N); indx rowids(Nnz); nzvals(Nnz); indx [o]which(Nnz); indx [t]wcols(Nnz)',

Convenience method.
Calls ccswhichfull(), and scales the output PDLs to correspond to a flat enumeration.
The output PDL $which() is B<not> guaranteed to be sorted in any meaningful order.
Use the qsort() method if you need sorted output.

=cut

*PDL::ccswhich = \&ccswhich;
sub ccswhich {
  my ($ptr,$rowids,$nzvals, $which, $wcols) = @_;
  my $nnz = $rowids->dim(0);
  $which = zeroes(ccs_indx,$nnz) if (!defined($which));
  $wcols = zeroes(ccs_indx,$nnz) if (!defined($wcols));
  ccswhichfull($ptr,$rowids,$nzvals, $wcols,$which);
  $which *= $ptr->dim(0);
  $which += $wcols;
  return $which;
}

##------------------------------------------------------
## ccstranspose() : transposition (convenience)

=pod

=head2 ccstranspose

=for sig

  Signature: (indx ptr(N); indx rowids(Nnz); nzvals(Nnz); indx [o]ptrT(M); indx [o]rowidsT(Nnz); [o]nzvalsT(Nnz)',

Transpose a compressed matrix.

=cut

*ccstransposefull = *PDL::ccstransposefull = *PDL::ccstranspose = \&ccstranspose;
sub ccstranspose {
  my ($ptr,$rowids,$nzvals, $ptrT,$rowidsT,$nzvalsT)=@_;
  my $N   = $ptr->dim(0);
  my $M   = defined($ptrT) ? $ptrT->dim(0) : $rowids->max+1;
  my $wnd = ccswhichND($ptr,$rowids,$nzvals)->slice("1:0,");
  return ccs_encode_compat($wnd,$nzvals,$M,$N, $ptrT,$rowidsT,$nzvalsT);
}


##======================================================================
## Lookup
##======================================================================

=pod

=head1 Lookup

=cut

##------------------------------------------------------
## ccsget2d() : lookup: 2d

=pod

=head2 ccsget2d

=for sig

  Signature: (indx ptr(N); indx rowids(Nnz); nzvals(Nnz); indx xvals(I); indx yvals(I); missing(); [o]ixvals(I))

Lookup values in a CCS-encoded PDL by 2d source index (no dataflow).
Pretty much like ccsi2dtonzi(), but returns values instead of indices.
If you know that your index PDLs $xvals() and $yvals() do not refer to any missing
values in the CCS-encoded matrix,
then the following two calls are equivalent (modulo dataflow):

  $ixvals =                ccsget2d   ($ptr,$rowids,$nzvals, $xvals,$yvals,0);
  $ixvals = index($nzvals, ccsi2dtonzi($ptr,$rowids,         $xvals,$yvals,0));

The difference is that only the second incantation will cause subsequent changes to $ixvals
to be propagated back into $nzvals.

=cut

*PDL::ccsget2d = \&ccsget2d;
sub ccsget2d {
  my ($ptr,$rowids,$nzvals, $xi,$yi, $missing, $ixnzvals) = @_;
  my $nzi        = ccsi2dtonzi($ptr,$rowids, $xi,$yi, -1);
  my $nzi_isgood = ($nzi != -1);
  $ixnzvals      = zeroes($nzvals->type, $xi->nelem) if (!defined($ixnzvals));
  if (!all($nzi_isgood)) {
    my $tmp;
    ($tmp=$ixnzvals->where( $nzi_isgood)) .= $nzvals->index($nzi->where($nzi_isgood));
    ($tmp=$ixnzvals->where(!$nzi_isgood)) .= $missing;
    $ixnzvals->badflag(1) if (PDL->topdl($missing)->badflag);
  }
  return $ixnzvals;
}


##------------------------------------------------------
## ccsget() : lookup: flat

=pod

=head2 ccsget

=for sig

  Signature: (indx ptr(N); indx rowids(Nnz); nzvals(Nnz); indx ix(I); missing(); [o]ixvals(I))

Lookup values in a CCS-encoded PDL by flat source index (no dataflow).
Pretty much like ccsitonzi(), but returns values instead of indices.
If you know that your index PDL $ix() does not refer to any missing
values in the CCS-encoded matrix,
then the following two calls are equivalent (modulo dataflow):

  $ixvals =                ccsget   ($ptr,$rowids,$nzvals, $ix,0);
  $ixvals = index($nzvals, ccsitonzi($ptr,$rowids,         $ix,0))

The difference is that only the second incantation will cause subsequent changes to $ixvals
to be propagated back into $nzvals.

=cut

*PDL::ccsget = \&ccsget;
sub ccsget {
  my ($ptr,$rowids,$nzvals, $ix, $missing, $ixnzvals) = @_;
  my $nzi        = ccsitonzi($ptr,$rowids, $ix,-1);
  my $nzi_isgood = ($nzi != -1);
  $ixnzvals      = zeroes($nzvals->type, $ix->nelem) if (!defined($ixnzvals));
  if (!all($nzi_isgood)) {
    my $tmp;
    ($tmp=$ixnzvals->where( $nzi_isgood)) .= $nzvals->index($nzi->where($nzi_isgood));
    ($tmp=$ixnzvals->where(!$nzi_isgood)) .= $missing;
    $ixnzvals->badflag(1) if (PDL->topdl($missing)->badflag);
  }
  return $ixnzvals;
}


##======================================================================
## Vector Operations
##======================================================================
=pod

=head1 Vector Operations

=cut

##======================================================================
## Vector Operations: Columns
##======================================================================
=pod

=head2 ccs${OP}_cv

=for sig

  Signature: (indx ptr(N); indx rowids(Nnz); nzvals_in(Nnz);  colvec(M);  [o]nzvals_out(Nnz))

Column-vector operation ${OP} on CCS-encoded PDL.

Should do something like the following
(without decoding the CCS matrix):

 ($colvec ${OP} ccsdecode(\$ptr,\$rowids,\$nzvals))->ccsencode;

Missing values in the CCS-encoded PDL are not affected by this operation.

${OP} is one of the following:

 plus       ##-- addition    (alias: 'add')
 minus      ##-- subtraction (alias: 'diff')
 mult       ##-- multiplication (NOT matrix-multiplication)
 divide     ##-- division    (alias: 'div')
 modulo     ##-- modulo
 power      ##-- potentiation

 gt         ##-- greater-than
 ge         ##-- greater-than-or-equal
 lt         ##-- less-than
 le         ##-- less-than-or-equal
 eq         ##-- equality
 ne         ##-- inequality
 spaceship  ##-- 3-way comparison

 and2       ##-- binary AND
 or2        ##-- binary OR
 xor        ##-- binary XOR
 shiftleft  ##-- left-shift
 shiftright ##-- right-shift

=cut

sub ccs_binop_compat_cv {
  my $ccsop = shift;
  return sub { $ccsop->(@_[1,2,3,4]) };
}
foreach my $op (@ccs_binops) {
  eval "*ccs${op}_cv = *PDL::ccs${op}_cv = ccs_binop_compat_cv(\\&PDL::ccs_${op}_vector_mia);";
}
*ccsadd_cv = *PDL::ccsadd_cv = \&ccsplus_cv;
*ccsdiff_cv = *PDL::ccsdiff_cv = \&ccsminus_cv;
*ccsdiv_cv = *PDL::ccsdiv_cv = \&ccsdivide_cv;

##======================================================================
## Vector Operations: Rows
##======================================================================
=pod

=head2 ccs${OP}_rv

=for sig

  Signature: (indx ptr(N); indx rowids(Nnz); nzvals_in(Nnz);  rowvec(N);  [o]nzvals_out(Nnz))

Row-vector operation ${OP} on CCS-encoded PDL.
Should do something like the following (without decoding the CCS matrix):

 ($column->slice("*1,") ${OP} ccsdecode($ptr,$rowids,$nzvals))->ccsencode;

Missing values in the CCS-encoded PDL are not effected by this operation.

See ccs${OP}_cv() above for supported operations.

=cut

sub ccs_binop_compat_rv {
  my $ccsop = shift;
  return sub {
    my $ptr = shift;
    my ($ptri,$ptrnzi) = ccs_decode_pointer($ptr->append($_[1]->nelem));
    $ccsop->($ptri, $_[1]->index($ptrnzi), @_[2,3]);
  };
}
foreach my $op (@ccs_binops) {
  eval "*ccs${op}_rv = *PDL::ccs${op}_rv = ccs_binop_compat_rv(\\&PDL::ccs_${op}_vector_mia);";
}
*ccsadd_rv = *PDL::ccsadd_rv = \&ccsplus_rv;
*ccsdiff_rv = *PDL::ccsdiff_rv = \&ccsminus_rv;
*ccsdiv_rv = *PDL::ccsdiv_rv = \&ccsdivide_rv;


##------------------------------------------------------
## Ufuncs (accumulators)

## \&ufuncsub = ccs_ufunc_compat(\&ccs_accum_sub)
sub ccs_ufunc_compat {
  my $sub = shift;
  return sub {
    my ($ptr,$rowids,$nzvals, $M,$rowvals) = @_;
    my ($ixout,$valsout) = $sub->($rowids->slice("*1,"),$nzvals, 0,0);
    $M       = $rowids->max+1 if (!defined($M));
    $rowvals = zeroes($nzvals->type,$M) if (!defined($rowvals));
    $rowvals->index($ixout->flat) .= $valsout;
    return $rowvals;
  };
}

## \&ufuncsub = ccs_ufunc_compat_t(\&ccs_accum_sub)
sub ccs_ufunc_compat_t {
  my $sub = shift;
  return sub {
    my ($ptr,$rowids,$nzvals, $colvals) = @_;
    my ($colids,$nzix) = ccs_decode_pointer($ptr->append($nzvals->nelem));
    ccs_ufunc_compat(undef,$colids,$nzvals->index($nzix), $ptr->dim(0),$colvals);
  };
}

*ccssumover  = *PDL::ccssumover  = ccs_ufunc_compat  (\&ccs_accum_sum);
*ccssumovert = *PDL::ccssumovert = ccs_ufunc_compat_t(\&ccs_accum_sum);

*ccprodover   = *PDL::ccsprodover  = ccs_ufunc_compat  (\&ccs_accum_prod);
*ccsprodovert = *PDL::ccsprodovert = ccs_ufunc_compat_t(\&ccs_accum_prod);


1; ##-- make perl happy

##======================================================================
## Footer Administrivia
##======================================================================

##---------------------------------------------------------------------
=pod

=head1 EXAMPLES

=head2 Compressed Column Format Example

 $a = pdl([
	   [10, 0, 0, 0,-2,  0],
	   [3,  9, 0, 0, 0,  3],
	   [0,  7, 8, 7, 0,  0],
	   [3,  0, 8, 7, 5,  0],
	   [0,  8, 0, 9, 9, 13],
	   [0,  4, 0, 0, 2, -1]
	  ]);

 ($ptr,$rowids,$nzvals) = ccsencode($a);

 print join("\n", "ptr=$ptr", "rowids=$rowids", "nzvals=$nzvals");

... prints something like:

 ptr=[0 3 7 9 12 16]
 rowids=[ 0 1 3 1 2 4 5 2 3 2 3 4  0 3 4 5 1  4  5]
 nzvals=[10 3 3 9 7 8 4 8 8 7 7 9 -2 5 9 2 3 13 -1]


=head2 Sparse Matrix Example

 ##-- create a random sparse matrix
 $a  = random(100,100);
 $a *= ($a>.9);

 ##-- encode it
 ($ptr,$rowids,$nzvals) = ccsencode($a);

 ##-- what did we save?
 sub pdlsize { return PDL::howbig($_[0]->type)*$_[0]->nelem; }
 print "Encoding saves us ",
       ($saved = pdlsize($a) - pdlsize($ptr) - pdlsize($rowids) - pdlsize($nzvals)),
       " bytes (", (100.0*$saved/pdlsize($a)), "%)\n";

... prints something like:

 Encoding saves us 71416 bytes (89.27%)


=head2 Decoding Example

 ##-- random matrix
 $a = random(100,100);

 ##-- make an expensive copy of $a by encoding & decoding
 ($ptr,$rowids,$nzvals) = ccsencode($a);
 $a2 = ccsdecode($ptr,$rowids,$nzvals);

 ##-- ...and make sure it's good
 print all($a==$a2) ? "Decoding is good!\n" : "Nasty icky bug!\n";

=cut

##---------------------------------------------------------------------
=pod

=head1 ACKNOWLEDGEMENTS

Perl by Larry Wall.

PDL by Karl Glazebrook, Tuomas J. Lukka, Christian Soeller, and others.

Original inspiration and algorithms from the SVDLIBC C library by Douglas Rohde;
which is itself based on SVDPACKC
by Michael Berry, Theresa Do, Gavin O'Brien, Vijay Krishna and Sowmini Varadhan.

=cut

##----------------------------------------------------------------------
=pod

=head1 KNOWN BUGS

Many.

=cut


##---------------------------------------------------------------------
=pod

=head1 AUTHOR

Bryan Jurish E<lt>moocow@cpan.orgE<gt>

=head2 Copyright Policy

Copyright (C) 2005-2022, Bryan Jurish. All rights reserved.

This package is free software, and entirely without warranty.
You may redistribute it and/or modify it under the same terms
as Perl itself.

=head1 SEE ALSO

perl(1),
PDL(3perl),
PDL::SVDLIBC(3perl),
PDL::CCS::Nd(3perl),

SVDLIBC: http://tedlab.mit.edu/~dr/SVDLIBC/

SVDPACKC: http://www.netlib.org/svdpack/

=cut
