vsip_dvgather_p - Gather Elements from a Vector

Core

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While our Core implementation implements all functions given in the standard we are still working on completing this documentation.

Please refer to the VSIPL standard for a complete function reference of the Core profile until we have completed work on this documentation.

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4.6.4 vsip_dvgather_p - Gather Elements from a Vector

void vsip_vgather_i(const vsip_vview_i *a, const vsip_vview_vi *b, const vsip_vview_i *r); 
void vsip_vgather_f(const vsip_vview_f *a, const vsip_vview_vi *b, const vsip_vview_f *r); 
void vsip_cvgather_f(const vsip_cvview_f *a, const vsip_vview_vi *b, const vsip_cvview_f *r);

Description

This function gathers elements from an input integer vector $a$ according to the indices specified in vector $b$ , and stores the results in output vector $r$ . The operation performs:

ri= abi

for all $i$ from 0 to $n-1$ , where $n$ is the length of the index and output vectors.

Parameters

const vsip_dvview_p* a: Input integer vector from which elements are gathered.
const vsip_vview_vi* b: Index vector containing the positions of elements to gather from $a$ .
const vsip_dvview_p* r: Output integer vector that will store the gathered elements.

Example

vsip_vview_i *data, *result; 
vsip_vview_vi *indices; 
vsip_length n = 10;  // Number of elements to gather 
vsip_length data_size = 100;  // Size of input data vector 
 
// Create vectors 
data = vsip_vcreate_i(data_size, VSIP_MEM_NONE); 
result = vsip_vcreate_i(n, VSIP_MEM_NONE); 
indices = vsip_vcreate_vi(n, VSIP_MEM_NONE); 
 
// Initialize data vector with some values 
for (vsip_length i = 0; i < data_size; i++) { 
    vsip_vput_i(data, i, i * 10);  // Example data 
} 
 
// Set up indices to gather (e.g., every 10th element) 
for (vsip_length i = 0; i < n; i++) { 
    vsip_vput_vi(indices, i, i * 10); 
} 
 
// Gather elements from data vector 
vsip_vgather_i(data, indices, result); 
 
// The result vector now contains elements from data at positions: 
// 0, 10, 20, 30, 40, 50, 60, 70, 80, 90 
 
// Print results 
printf("Gathered elements:\n"); 
for (vsip_length i = 0; i < n; i++) { 
    printf("%d ", vsip_vget_i(result, i)); 
} 
printf("\n"); 
 
// Clean up 
vsip_valldestroy_i(data); 
vsip_valldestroy_i(result); 
vsip_valldestroy_vi(indices);

Notes

The index vector $b$ must contain valid indices for the input vector $a$ (i.e., $0 ≤bi< length(a)$ ).
The output vector $r$ must have the same length as the index vector $b$ .

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