PDL::CCS::Functions - Useful perl-level functions for PDL::CCS
use PDL; use PDL::CCS::Functions; ##--------------------------------------------------------------------- ## ... stuff happens
Signature: (indx ptr(N+1); indx [o]len(N))
Get number of non-missing values for each axis value from a CCS-encoded offset pointer vector $ptr().
Signature: (indx whichnd(Ndims,Nnz); nzvals(Nnz); missing(); \@Dims; [o]a(@Dims))
Decode a CCS-encoded matrix (no dataflow).
Scalar operations can be performed in parallel directly on $nzvals (and if applicable on $missing as well):
$nzvals
$missing
$c = 42; $nzvals2 = $nzvals + $c; $missing2 = $missing + $c; $nzvals2 = $nzvals - $c; $missing2 = $missing - $c; $nzvals2 = $nzvals * $c; $missing2 = $missing * $c; $nzvals2 = $nzvals / $c; $missing2 = $missing / $c; $nzvals2 = $nzvals ** $c; $missing2 = $missing ** $c; $nzvals2 = log($nzvals); $missing2 = log($missing); $nzvals2 = exp($nzvals); $missing2 = exp(missing); $nzvals2 = $nzvals->and2($c,0); $missing2 = $missing->and($c,0); $nzvals2 = $nzvals->or2($c,0); $missing2 = $missing->or2($c,0); $nzvals2 = $nzvals->not(); $missing2 = $missing->not();
Nothing prevents scalar operations from producing new "missing" values (e.g. $nzvals*0), so you might want to re-encode your compressed data after applying the operation.
Signature: (indx whichDimV(Nnz); nzvals(Nnz); vec(V); [o]nzvals_out(Nnz))
A number of row- and column-vector operations may be performed directly on encoded Nd-PDLs, without the need for decoding to a (potentially huge) dense temporary. These operations assume that "missing" values are annihilators with respect to the operation in question, i.e. that it holds for all $x in $vec that:
$x
$vec
($missing __OP__ $x) == $missing
This is in line with the usual PDL semantics if your $missing value is BAD, but may produce unexpected results when e.g. adding a vector to a sparse PDL with $missing==0. If you really need to do something like the latter, then you're probably better off decoding to a dense PDL anyway.
BAD
Predefined function names for encoded-PDL vector operations are all of the form: ccs_${OPNAME}_ma, where ${OPNAME} is the base name of the operation:
ccs_${OPNAME}_ma
plus ##-- addition minus ##-- subtraction mult ##-- multiplication (NOT matrix-multiplication) divide ##-- division 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
Returns a generic vector-operation subroutine which reports errors as $opName and uses \&PDLCODE to perform underlying computation.
$opName
Signature: (indx which(Ndims,Nnz); nzvals(Nnz); missing(); Dim0(); indx [o]nzix(Nnz); indx [o]nzenum(Nnz))
Underlying guts for PDL::CCS::Nd::qsort() and PDL::CCS::Nd::qsorti(). Given a set of $Nnz items $i each associated with a vector-key $which(:,$i) and a value $nzvals($i), returns a vector of $Nnz item indices $nzix() such that $which(:,$nzix) is vector-sorted in ascending order and $nzvals(:,$nzix) are sorted in ascending order for each unique key-vector in $which(), and an enumeration $nzenum() of items for each unique key-vector in terms of the sorted data: $nzenum($j) is the logical position of the item $nzix($j).
$which(:,$i)
$nzvals($i)
$nzix()
$which(:,$nzix)
$nzvals(:,$nzix)
$which()
$nzenum()
$nzenum($j)
$nzix($j)
If $missing and $Dim0 are defined, items $i=$nzix($j) with values $nzvals($i) > $missing will be logically enumerated at the end of the range [0,$Dim0-1] and there will be a gap between $nzenum() values for a $which()-key with fewer than $Dim0 instances; otherwise $nzenum() values will be enumerated in ascending order starting from 0.
$Dim0
$i=$nzix($j)
$nzvals($i) > $missing
For an unsorted index+value dataset ($which0,$nzvals0) with
($which0,$nzvals0)
($nzix,$nzenum) = ccs_qsort($which0("1:-1,"),$nzvals0,$missing,$which0("0,")->max+1)
qsort() can be implemented as:
$which = $nzenum("*1,")->glue(0,$which0("1:-1,")->dice_axis(1,$nzix)); $nzvals = $nzvals0->index($nzix);
and qsorti() as:
$which = $nzenum("*1,")->glue(0,$which0("1:-1,")->dice_axis(1,$nzix)); $nzvals = $which0("(0),")->index($nzix);
Perl by Larry Wall.
PDL by Karl Glazebrook, Tuomas J. Lukka, Christian Soeller, and others.
Bryan Jurish <moocow@cpan.org>
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), PDL::CCS::Nd(3perl),
To install PDL::CCS, copy and paste the appropriate command in to your terminal.
cpanm
cpanm PDL::CCS
CPAN shell
perl -MCPAN -e shell install PDL::CCS
For more information on module installation, please visit the detailed CPAN module installation guide.