A high-performance general-purpose compute library

Evaluate the cumulative sum (inclusive) along a given dimension. More...

## Functions

AFAPI array accum (const array &in, const int dim=0)
C++ Interface to evaluate the cumulative sum (inclusive) along a given dimension. More...

AFAPI af_err af_accum (af_array *out, const af_array in, const int dim)
C Interface to evaluate the cumulative sum (inclusive) along a given dimension. More...

## Detailed Description

Evaluate the cumulative sum (inclusive) along a given dimension.

For a 1D array $$X$$, the inclusive cumulative sum calculates $$x_i = \sum_{p=0}^{i}x_p$$ for every $$x \in X$$. Here is a simple example for the 1D case:

float hA[] = {0, 1, 2, 3, 4};
array A(5, hA);
// 0.
// 1.
// 2.
// 3.
// 4.
array accumA = accum(A);
// 0.
// 1.
// 3.
// 6.
// 10.

For 2D arrays and higher dimensions, you can specify the dimension along which the cumulative sum will be calculated. Thus, the formula above will be calculated for all array slices along the specified dimension (in the 2D case for example, this looks like $$x_{i,j} = \sum_{p=0}^{j}x_{i,p}$$ if the second dimension (dim1) was chosen). If no dimension is specified, then the first dimension (dim0) is used by default (only in the C++ API; the dimension is required to be specified in the C API):

float hB[] = {0, 1, 2, 3, 4, 5, 6, 7, 8};
array B(3, 3, hB);
// 0. 3. 6.
// 1. 4. 7.
// 2. 5. 8.
array accumB_dim0 = accum(B);
// 0. 3. 6.
// 1. 7. 13.
// 3. 12. 21.
array accumB_dim1 = accum(B, 1);
// 0. 3. 9.
// 1. 5. 12.
// 2. 7. 15.

The output array type may be different from the input array type. The following table defines corresponding output types for each input type:

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

This function runs across all batches in the input simultaneously.

## ◆ accum()

 AFAPI array accum ( const array & in, const int dim = 0 )

C++ Interface to evaluate the cumulative sum (inclusive) along a given dimension.

Parameters
 [in] in input array [in] dim dimension along which the sum is accumulated, 0 denotes the first non-singleton dimension
Returns
cumulative sum

## ◆ af_accum()

 AFAPI af_err af_accum ( af_array * out, const af_array in, const int dim )

C Interface to evaluate the cumulative sum (inclusive) along a given dimension.

Parameters
 [out] out cumulative sum [in] in input array [in] dim dimension along which the sum is accumulated
Returns
AF_SUCCESS, if function returns successfully, else an af_err code is given