maxByKey

Finds the max of an input array according to an array of keys. More...

Functions
AFAPI void	maxByKey (array &keys_out, array &vals_out, const array &keys, const array &vals, const int dim=-1)
	C++ Interface for maximum values in an array according to a key.
AFAPI af_err	af_max_by_key (af_array *keys_out, af_array *vals_out, const af_array keys, const af_array vals, const int dim)
	C Interface for maximum values in an array according to key.

Detailed Description

Finds the max of an input array according to an array of keys.

The maximum will be found of all values corresponding to each group of consecutive equal keys. Keys can repeat, however only consecutive key values will be considered for each reduction. If a key value is repeated somewhere else in the keys array it will be considered the start of a new reduction. There are two outputs: the reduced set of consecutive keys and the corresponding final reduced values. An example demonstrating the reduction behavior can be seen in the following snippet.

 
    array keys(9, hkeys);  // keys = [ 0 0 1 1 1 0 0 2 2 ]
    array vals(9, hvals);  // vals = [ 1 2 3 4 5 6 7 8 9 ];
 
    array okeys, ovals;
    maxByKey(okeys, ovals, keys, vals);
 
    // okeys = [ 0 1 0 2 ]
    // ovals = [ 2 5 7 9 ]
 

The keys input type must be an integer type(s32 or u32). The values return type will be the same as the values input type.

The input keys must be a 1-D vector matching the size of the reduced dimension. In the case of multiple dimensions in the input values array, the dim parameter specifies which dimension to reduce along. An example of multi-dimensional reduce by key can be seen below:

 
    array keys(5, hkeys);
    array vals(2, 5, hvals);
 
    // keys = [ 1 0 0 2 2 ]
 
    // vals = [[ 1 2 3 4 5  ]
    //         [ 6 7 8 9 10 ]]
 
    const int reduce_dim = 1;
    array okeys, ovals;
    maxByKey(okeys, ovals, keys, vals, reduce_dim);
 
    // okeys = [ 1 0 2 ]
 
    // ovals = [[ 1  3  5 ],
    //          [ 6  8 10 ]]
 

Function Documentation

af_max_by_key()

AFAPI af_err af_max_by_key	(	af_array *	keys_out,
		af_array *	vals_out,
		const af_array	keys,
		const af_array	vals,
		const int	dim
	)

C Interface for maximum values in an array according to key.

Parameters

[out]	keys_out	will contain the reduced keys in vals along dim
[out]	vals_out	will contain the maximum of all values in vals along dim according to keys
[in]	keys	is the key array
[in]	vals	is the array containing the values to be reduced
[in]	dim	The dimension along which the maximum value is extracted

Returns

AF_SUCCESS if the execution completes properly

maxByKey()

AFAPI void maxByKey	(	array &	keys_out,
		array &	vals_out,
		const array &	keys,
		const array &	vals,
		const int	dim = -1
	)

C++ Interface for maximum values in an array according to a key.

Parameters

[out]	keys_out	will contain the reduced keys in vals along dim
[out]	vals_out	will contain the maximum of all values in vals along dim according to keys
[in]	keys	is the key array
[in]	vals	is the array containing the values to be reduced
[in]	dim	The dimension along which the max operation occurs

Note

dim is -1 by default. -1 denotes the first non-singleton dimension.

NaN values are ignored