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.\" ========================================================================
.\"
.IX Title "Ops 3pm"
.TH Ops 3pm "2023-04-15" "perl v5.36.0" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.nh
.SH "NAME"
PDL::CCS::Ops \- Low\-level binary operations for compressed storage sparse PDLs
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 2
\& use PDL;
\& use PDL::CCS::Utils;
\&
\& ##\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-
\& ## ... stuff happens
.Ve
.SH "FUNCTIONS"
.IX Header "FUNCTIONS"
.SS "ccs_binop_align_block_mia"
.IX Subsection "ccs_binop_align_block_mia"
.Vb 4
\&  Signature: (
\&    indx ixa(Ndims,NnzA); indx ixb(Ndims,NnzB); indx    istate(State);
\&    indx [o]nzai(NnzC);   indx [o]nzbi(NnzC);   indx [o]ostate(State);
\&    )
.Ve
.PP
Partially aligns a pair of lexicographically sorted index-vector lists \f(CW\*(C`$ixa()\*(C'\fR and \f(CW\*(C`$ixb()\*(C'\fR,
e.g. for block-wise incremental computation of binary operations over sparse index-encoded PDLs,
assuming missing indices correspond to annihilators.
.PP
On return, the vectors \f(CW$nzai\fR and \f(CW$nzbi\fR hold indices into \f(CW\*(C`NnzA\*(C'\fR and \f(CW\*(C`NnzB\*(C'\fR
respectively, and are constructed such that:
.PP
.Vb 1
\& ($ixa(,$nzai\->slice("0:$nzci_max")) == $ixb(,$nzbi\->slice("0:$nzci_max"))
.Ve
.PP
At most \f(CW\*(C`NnzC\*(C'\fR alignments are performed, and alignment ceases
as soon as any of the PDLs \f(CW\*(C`$ixa()\*(C'\fR, \f(CW\*(C`$ixb()\*(C'\fR, \f(CW\*(C`$nzai()\*(C'\fR, or \f(CW\*(C`$nzbi()\*(C'\fR
has been exhausted.
.PP
The parameters \f(CW\*(C`$istate()\*(C'\fR and \f(CW\*(C`$ostate()\*(C'\fR hold the state of the algorithm,
for incremental block-wise computation at the perl level.  Each state \s-1PDL\s0
is a 7\-element \s-1PDL\s0 containing the following values:
.PP
.Vb 9
\& INDEX LABEL       DESCRIPTION
\& \-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-
\&   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
.Ve
.PP
For computation of the first block, $\fBistate()\fR can be safely set to \f(CW\*(C`zeroes(long,7)\*(C'\fR.
.PP
Repetitions may occur in input index PDLs \f(CW\*(C`$ixa()\*(C'\fR and \f(CW\*(C`$ixb()\*(C'\fR.
If an index-match occurs on such a \*(L"run\*(R", \fIall pairs\fR of matching values are
added to the output PDLs.
.PP
All alignments have been performed if:
.PP
.Vb 1
\& $ostate(0)==$NnzA && $ostate(1)==$NnzB
.Ve
.PP
\&\fB\s-1WARNING:\s0\fR this alignment method ignores index-vectors which are not present
in \fIboth\fR \f(CW\*(C`$ixa()\*(C'\fR and \f(CW\*(C`$ixb()\*(C'\fR, which is a Good Thing if your are feeding
the aligned values into an operation for which missing values are annihilators:
.PP
.Vb 2
\& $missinga * $bval     == ($missinga * $missingb)  for each $bval \ein $b, and
\& $aval     * $missingb == ($missinga * $missingb)  for each $aval \ein $a
.Ve
.PP
This ought to be the case for all operations if missing values are \f(CW\*(C`BAD\*(C'\fR (see PDL::Bad),
but might cause unexpected results if e.g. missing values are zero and the operation
in question is addition.
.PP
ccs_binop_align_block_mia does not process bad values.
It will set the bad-value flag of all output ndarrays if the flag is set for any of the input ndarrays.
.SH "ACKNOWLEDGEMENTS"
.IX Header "ACKNOWLEDGEMENTS"
Perl by Larry Wall.
.PP
\&\s-1PDL\s0 by Karl Glazebrook, Tuomas J. Lukka, Christian Soeller, and others.
.SH "KNOWN BUGS"
.IX Header "KNOWN BUGS"
No support for (pseudo)\-threading.
.SH "AUTHOR"
.IX Header "AUTHOR"
Bryan Jurish <moocow@cpan.org>
.SS "Copyright Policy"
.IX Subsection "Copyright Policy"
All other parts Copyright (C) 2007\-2022, Bryan Jurish. All rights reserved.
.PP
This package is free software, and entirely without warranty.
You may redistribute it and/or modify it under the same terms
as Perl itself.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBperl\fR\|(1), \s-1\fBPDL\s0\fR\|(3perl)