sumByKey

Sum array elements over a given dimension, according to an array of keys. More...

Functions
AFAPI void	sumByKey (array &keys_out, array &vals_out, const array &keys, const array &vals, const int dim=-1)
	C++ Interface to sum array elements over a given dimension, according to an array of keys. More...
AFAPI void	sumByKey (array &keys_out, array &vals_out, const array &keys, const array &vals, const int dim, const double nanval)
	C++ Interface to sum array elements over a given dimension, replacing any NaNs with a specified value, according to an array of keys. More...
AFAPI af_err	af_sum_by_key (af_array *keys_out, af_array *vals_out, const af_array keys, const af_array vals, const int dim)
	C Interface to sum array elements over a given dimension, according to an array of keys. More...
AFAPI af_err	af_sum_by_key_nan (af_array *keys_out, af_array *vals_out, const af_array keys, const af_array vals, const int dim, const double nanval)
	C Interface to sum array elements over a given dimension, replacing any NaNs with a specified value, according to an array of keys. More...

Detailed Description

Sum array elements over a given dimension, according to an array of keys.

The values corresponding to each group of consecutive equal keys will be summed together. 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 2 3 4 5 6 7 8 9 ];
 
    array okeys, ovals;
    sumByKey(okeys, ovals, keys, vals);
 
    // okeys = [ 0  1  0  2 ]
    // ovals = [ 3 12 13 17 ]
 

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

This table defines output types for corresponding input types:

Input Type	Output Type
f32, f64, c32, c64	same as input
s32, s64, u32, u64	same as input
s16	s32
u16, u8, b8	u32
f16	f32

The keys array must be 1-dimensional 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 2 3 4 5  ]
    //         [ 6 7 8 9 10 ]]
 
    const int reduce_dim = 1;
    array okeys, ovals;
    sumByKey(okeys, ovals, keys, vals, reduce_dim);
 
    // okeys = [ 1 0 2 ]
 
    // ovals = [[ 1  5  9 ],
    //          [ 6 15 19 ]]
 

Function Documentation

af_sum_by_key()

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

C Interface to sum array elements over a given dimension, according to an array of keys.

Parameters

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

Returns

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

af_sum_by_key_nan()

AFAPI af_err af_sum_by_key_nan	(	af_array *	keys_out,
		af_array *	vals_out,
		const af_array	keys,
		const af_array	vals,
		const int	dim,
		const double	nanval
	)

C Interface to sum array elements over a given dimension, replacing any NaNs with a specified value, according to an array of keys.

Parameters

[out]	keys_out	reduced keys
[out]	vals_out	sum
[in]	keys	keys array
[in]	vals	input array
[in]	dim	dimension along which the summation occurs
[in]	nanval	value that replaces NaNs

Returns

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

sumByKey() [1/2]

AFAPI void sumByKey	(	array &	keys_out,
		array &	vals_out,
		const array &	keys,
		const array &	vals,
		const int	dim,
		const double	nanval
	)

C++ Interface to sum array elements over a given dimension, replacing any NaNs with a specified value, according to an array of keys.

Parameters

[out]	keys_out	reduced keys
[out]	vals_out	sum
[in]	keys	keys array
[in]	vals	input array
[in]	dim	dimension along which the summation occurs
[in]	nanval	value that replaces NaNs

sumByKey() [2/2]

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

C++ Interface to sum array elements over a given dimension, according to an array of keys.

Parameters

[out]	keys_out	reduced keys
[out]	vals_out	sum
[in]	keys	keys array
[in]	vals	input array
[in]	dim	dimension along which the summation occurs, -1 denotes the first non-singleton dimension