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MooX-PDL-Role-Proxy-0.07
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/ MooX::PDL::Role::Proxy

NAME

MooX::PDL::Role::Proxy - treat a container of ndarrays (piddles) as if it were an ndarray (piddle)

VERSION

version 0.07

SYNOPSIS

  package My::Class;

  use Moo;
  use MooX::PDL::Role::Proxy;

  use PDL;

  has p1 => (
      is      => 'rw',
      default => sub { sequence( 10 ) },
      ndarray  => 1
  );

  has p2 => (
      is      => 'rw',
      default => sub { sequence( 10 ) + 1 },
      ndarray  => 1
  );


  sub clone_with_ndarrays {
      my ( $self, %ndarrays ) = @_;

      $self->new->_set_attr( %ndarrays );
  }


  my $obj = My::Class->new;

  # clone $obj and filter ndarrays.
  my $new = $obj->where( $obj->p1 > 5 );

DESCRIPTION

MooX::PDL::Role::Proxy is a Moo::Role which turns its consumer into a proxy object for some of its attributes, which are assumed to be PDL objects (or other proxy objects). A subset of PDL methods applied to the proxy object are applied to the selected attributes. (See PDL::QuckStart for more information on PDL and its objects (ndarrays)).

As an example, consider an object representing a set of detected events (think physics, not computing), which contains metadata describing the events as well as ndarrays representing event position, energy, and arrival time. The structure might look like this:

  {
      metadata => \%metadata,
      time   => $time,         # ndarray
      x      => $x,            # ndarray
      y      => $y,            # ndarray
      energy => $energy        # ndarray
  }

To filter the events on energy would traditionally be performed explicitly on each element in the structure, e.g.

  my $mask = which( $obj->{energy} > 20 );

  my $copy = {};
  $copy->{time}   = $obj->{time}->where( $mask );
  $copy->{x}      = $obj->{x}->where( $mask );
  $copy->{y}      = $obj->{y}->where( $mask );
  $copy->{energy} = $obj->{energy}->where( $mask );

Or, more succinctly,

  $new->{$_} = $obj->{$_}->where( $mask ) for qw( time x y energy );

With MooX::PDL::Role::Proxy this turns into

  my $copy = $obj->where( $mask );

Or, if the results should be stored in the same object,

  $obj->inplace->where( $mask );

Usage and Class requirements

Each attribute to be operated on by the common PDL-like operators should be given a ndarray option, e.g.

  has p1 => (
      is      => 'rw',
      default => sub { sequence( 10 ) },
      ndarray  => 1,
  );

(Treat the option value as an identifier for the group of ndarrays which should be operated on, rather than as a boolean).

Results of Operations

The results of operations may either be stored "In Place" or returned in "Cloned Objects". By default, operations return cloned objects.

In Place

Use one of the following methods, "inplace", "inplace_store", "inplace_set". to indicate that the next in-place aware operation should be performed in-place. After the operation is completed, the in-place flag will be reset.

To support inplace operations, attributes tagged with the ndarray option must have write accessors. They may be public or private.

Cloned Objects

The class must provide a a clone method. If cloning an object requires extra arguments, use "_set_clone_args" and "_clear_clone_args" to set or reset the arguments.

If the class provides the _clone_with_ndarrays method, then it will be called as

   $object->_clone_with_ndarrays( \%ndarrays, ?$arg);

where $arg will only be passed if "_set_clone_args" was called.

For backwards compatibility, the clone_with_piddles method is supported, but it is not possible to pass in extra arguments. It will be called as

   $object->clone_with_piddles ( %ndarrays );

Nested Proxy Objects

A class with the applied role should respond equivalently to a true ndarray when the supported methods are called on it (it's a bug otherwise). Thus, it is possible for a proxy object to contain another, and as long as the contained object has the ndarray attribute set, the supported method will be applied to the contained object appropriately.

METHODS

_ndarrays

  @ndarray_names = $obj->_ndarrays;

This returns a list of the names of the object's attributes with a ndarray (or for backwards compatibility, piddle ) tag set. The list is lazily created by the _build__ndarrays method, which can be modified or overridden if required. The default action is to find all tagged attributes with tags ndarray or piddle.

_clear_ndarrays

Clear the list of attributes which have been tagged as ndarrays. The list will be reset to the defaults when _ndarrays is next invoked.

_apply_to_tagged_attrs

   $obj->_apply_to_tagged_attrs( \&sub );

Execute the passed subroutine on all of the attributes tagged with ndarray (or piddle). The subroutine will be invoked as

   sub->( $attribute, $inplace )

where $inplace will be true if the operation is to take place inplace.

The subroutine should return the ndarray to be stored.

Returns $obj if applied in-place, or a new object if not.

inplace

  $obj->inplace( ?$how )

Indicate that the next inplace aware operation should be done inplace.

An optional argument indicating how the ndarrays should be updated may be passed (see "set_inplace" for more information). This API differs from from the inplace method.

It defaults to using the attributes' accessors to store the results, which will cause triggers, etc. to be called.

Returns $obj. See also "inplace_direct" and "inplace_accessor".

inplace_store

  $obj->inplace_store

Indicate that the next inplace aware operation should be done inplace. NDarrays are changed inplace via the .= operator, avoiding any side-effects caused by using the attributes' accessors.

It is equivalent to calling

  $obj->set_inplace( MooX::PDL::Role::Proxy::INPLACE_STORE );

Returns $obj. See also "inplace" and "inplace_accessor".

inplace_set

  $obj->inplace_set

Indicate that the next inplace aware operation should be done inplace. The object level attribute accessors will be used to store the results (which may be the same ndarray). This will cause Moo triggers, etc to be called.

It is equivalent to calling

  $obj->set_inplace( MooX::PDL::Role::Proxy::INPLACE_SET );

Returns $obj. See also "inplace_store" and "inplace".

set_inplace

  $obj->set_inplace( $value );

Change the value of the inplace flag. Accepted values are

MooX::PDL::Role::Proxy::INPLACE_SET

Use the object level attribute accessors to store the results (which may be the same ndarray). This will cause Moo triggers, etc to be called.

MooX::PDL::Role::Proxy::INPLACE_STORE

Store the results directly in the existing ndarray using the .= operator.

is_inplace

  $bool = $obj->is_inplace;

Test if the next inplace aware operation should be done inplace

copy

  $new = $obj->copy;

Create a copy of the object and its ndarrays. If the inplace flag is set, it returns $obj otherwise it is exactly equivalent to

  $obj->clone_with_ndarrays( map { $_ => $obj->$_->copy } @{ $obj->_ndarrays } );

sever

  $obj = $obj->sever;

Call "sever" in PDL::Core on tagged attributes. This is done inplace. Returns $obj.

index

   $new = $obj->index( NDARRAY );

Call "index" in PDL::Slices on tagged attributes. This is inplace aware. Returns $obj if applied in-place, or a new object if not.

at

   $obj = $obj->at( @indices );

Returns a simple object containing the results of running "index" in PDL::Core on tagged attributes. The object's attributes are named after the tagged attributes.

where

   $obj = $obj->where( $mask );

Apply "where" in PDL::Primitive to the tagged attributes. It is in-place aware. Returns $obj if applied in-place, or a new object if not.

_set_clone_args

   $obj->_set_clone_args( $args );

Pass the given value to the _clone_with_args_ndarrays method when an object must be implicitly cloned.

_clear_clone_args

   $obj->_clear_clone_args;

Clear out any value set by _set_clone_args.

_set_attr

   $obj->_set_attr( %attr )

Set the object's attributes to the values in the %attr hash.

Returns $obj.

qsort

  $obj->qsort;

Sort the ndarrays. This requires that the object has a qsorti method, which should return an ndarray index of the elements in ascending order.

For example, to designate the radius attribute as that which should be sorted on by qsort, include the handles option when declaring it:

  has radius => (
      is      => 'ro',
      ndarray  => 1,
      isa     => Piddle1D,
      handles => ['qsorti'],
  );

It is in-place aware. Returns $obj if applied in-place, or a new object if not.

qsort_on

  $obj->sort_on( $ndarray );

Sort on the specified $ndarray.

It is in-place aware. Returns $obj if applied in-place, or a new object if not.

clip_on

  $obj->clip_on( $ndarray, $min, $max );

Clip on the specified $ndarray, removing elements which are outside the bounds of [$min, $max). Either bound may be undef to indicate it should be ignore.

It is in-place aware.

Returns $obj if applied in-place, or a new object if not.

slice

  $obj->slice( $slice );

Slice. See "slice" in PDL::Slices for more information.

It is in-place aware. Returns $obj if applied in-place, or a new object if not.

LIMITATIONS

There are significant limits to this encapsulation.

  • The ndarrays operated on must be similar enough in structure so that the ganged operations make sense (and are valid!).

  • There is (currently) no way to indicate that there are different sets of ndarrays contained within the object.

  • The object must be able to be cloned relatively easily, so that non-inplace operations can create copies of the original object.

SUPPORT

Bugs

Please report any bugs or feature requests to or through the web interface at: https://rt.cpan.org/Public/Dist/Display.html?Name=MooX-PDL-Role-Proxy

Source

Source is available at

  https://gitlab.com/djerius/moox-pdl-role-proxy

and may be cloned from

  https://gitlab.com/djerius/moox-pdl-role-proxy.git

AUTHOR

Diab Jerius <djerius@cpan.org>

COPYRIGHT AND LICENSE

This software is Copyright (c) 2018 by Smithsonian Astrophysical Observatory.

This is free software, licensed under:

  The GNU General Public License, Version 3, June 2007