 A high-performance general-purpose compute library

Finds the sum of an input array 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 for sum of elements along given dimension by key.

AFAPI void sumByKey (array &keys_out, array &vals_out, const array &keys, const array &vals, const int dim, const double nanval)
C++ Interface for sum of elements along given dimension by key while replacing nan values.

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 for sum of elements in an array according to key.

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 for sum of elements in an array according to key while replacing nans.

## Detailed Description

Finds the sum of an input array 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 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 an integer type(s32 or u32). This table defines the return types for the corresponding values type

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

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;
sumByKey(okeys, ovals, keys, vals, reduce_dim);
// okeys = [ 1 0 2 ]
// ovals = [[ 1 5 9 ],
// [ 6 15 19 ]]

## ◆ 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 for sum of elements 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 sum 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 add operation occurs
Returns
AF_SUCCESS if the execution completes properly

## ◆ 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 for sum of elements in an array according to key while replacing nans.

Parameters
 [out] keys_out will contain the reduced keys in vals along dim [out] vals_out will contain the sum 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 add operation occurs [in] nanval The value that will replace the NaNs in vals
Returns
AF_SUCCESS if the execution completes properly

## ◆ 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 for sum of elements along given dimension by key while replacing nan values.

Parameters
 [out] keys_out Will contain the reduced keys in vals along dim [out] vals_out Will contain the sum 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 add operation occurs [in] nanval The value that will replace the NaNs in vals

## ◆ sumByKey() [2/2]

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

C++ Interface for sum of elements along given dimension by key.

Parameters
 [out] keys_out will contain the reduced keys in vals along dim [out] vals_out will contain the sum 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 add operation occurs
Note
dim is -1 by default. -1 denotes the first non-singleton dimension.