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Bryan Jurish
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PDL::CCS::Ops - Low-level binary operations for compressed storage sparse PDLs


 use PDL;
 use PDL::CCS::Utils;

 ## ... stuff happens



  Signature: (
    indx ixa(Ndims,NnzA); indx ixb(Ndims,NnzB); indx    istate(State);
    indx [o]nzai(NnzC);   indx [o]nzbi(NnzC);   indx [o]ostate(State);

Partially aligns a pair of lexicographically sorted index-vector lists $ixa() and $ixb(), e.g. for block-wise incremental computation of binary operations over sparse index-encoded PDLs, assuming missing indices correspond to annihilators.

On return, the vectors $nzai and $nzbi hold indices into NnzA and NnzB respectively, and are constructed such that:

 ($ixa(,$nzai->slice("0:$nzci_max")) == $ixb(,$nzbi->slice("0:$nzci_max"))

At most NnzC alignments are performed, and alignment ceases as soon as any of the PDLs $ixa(), $ixb(), $nzai(), or $nzbi() has been exhausted.

The parameters $istate() and $ostate() hold the state of the algorithm, for incremental block-wise computation at the perl level. Each state PDL is a 7-element PDL containing the following values:

   0   nnzai       minimum offset in NnzA of current $ixa() value
   1   nnzai_nxt   minimum offset in NnzA of next $ixa() value
   2   nnzbi       minimum offset in NnzB of current $ixb() value
   3   nnzbi_nxt   minimum offset in NnzB of next $ixb() value
   4   nnzci       minimum offset in NnzC of current ($ixa(),$ixb()) value pair
   5   nnzci_nxt   minimum offset in NnzC of next ($ixa(),$ixb()) value pair
   6   cmpval      3-way comparison value for current ($ixa(),$ixb()) value pair

For computation of the first block, $istate() can be safely set to zeroes(long,7).

Repetitions may occur in input index PDLs $ixa() and $ixb(). If an index-match occurs on such a "run", all pairs of matching values are added to the output PDLs.

All alignments have been performed if:

 $ostate(0)==$NnzA && $ostate(1)==$NnzB

WARNING: this alignment method ignores index-vectors which are not present in both $ixa() and $ixb(), which is a Good Thing if your are feeding the aligned values into an operation for which missing values are annihilators:

 $missinga * $bval     == ($missinga * $missingb)  for each $bval \in $b, and
 $aval     * $missingb == ($missinga * $missingb)  for each $aval \in $a

This ought to be the case for all operations if missing values are BAD (see PDL::Bad), but might cause unexpected results if e.g. missing values are zero and the operation in question is addition.

ccs_binop_align_block_mia does not process bad values. It will set the bad-value flag of all output piddles if the flag is set for any of the input piddles.


Perl by Larry Wall.

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


No support for (pseudo)-threading.


Bryan Jurish <moocow@cpan.org>

All other parts Copyright (C) 2007-2013, 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.


perl(1), PDL(3perl)