Count non-zero values in an array, according to an array of keys. More...

Functions
AFAPI void	countByKey (array &keys_out, array &vals_out, const array &keys, const array &vals, const int dim=-1)
	C++ Interface to count non-zero values in an array, according to an array of keys. More...

AFAPI af_err	af_count_by_key (af_array keys_out, af_array vals_out, const af_array keys, const af_array vals, const int dim)
	C Interface to count non-zero values in an array, according to an array of keys. More...

Detailed Description

Count non-zero values in an array, according to an array of keys.

All non-zero values corresponding to each group of consecutive equal keys will be counted. 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 set of 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 1 0 1 1 0 0 1 0 ];
 
    array okeys, ovals;
    countByKey(okeys, ovals, keys, vals);
 
    // okeys = [ 0 1 0 2 ]
    // ovals = [ 2 2 0 1 ]
 

The keys' input type must be integer (s32 or u32).

The output type is u32.

The keys array must be 1-dimenstional matching the size of the reduced dimension. 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 1 1 0 1 ]
    //         [ 0 1 0 1 1 ]]
 
    const int reduce_dim = 1;
    array okeys, ovals;
    countByKey(okeys, ovals, keys, vals, reduce_dim);
 
    // okeys = [ 1 0 2 ]
 
    // ovals = [[ 1 2 1 ],
    //          [ 0 1 2 ]]
 

Function Documentation

◆ af_count_by_key()

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

C Interface to count non-zero values in an array, according to an array of keys.

NaN values are treated as non-zero.

Parameters

[out]	keys_out	reduced keys
[out]	vals_out	count
[in]	keys	keys array
[in]	vals	input array
[in]	dim	dimension along which the count occurs

Returns: AF_SUCCESS, if function returns successfully, else an af_err code is given

◆ countByKey()

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

C++ Interface to count non-zero values in an array, according to an array of keys.