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/*
* Copyright (c) 2018 Samsung Electronics Co., Ltd. All Rights Reserved
* Copyright (c) 2017 ARM Limited.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "helpers.h"
__global inline float* get_vec_elem(Vector* vec, int idx)
{
return (__global float*)(vec->ptr + idx * vec->stride_x);
}
__global inline int* get_vec_elem_int(Vector* vec, int idx)
{
return (__global int*)(vec->ptr + idx * vec->stride_x);
}
// A utility function to swap two elements
void swap(__global float *a, __global float *b)
{
float t = *a;
*a = *b;
*b = t;
}
void swap_idx(__global int *a, __global int *b)
{
int t = *a;
*a = *b;
*b = t;
}
/* This function is same in both iterative and recursive*/
int partition (Vector* arr, __global int* indices, int l, int h)
{
float x = *get_vec_elem(arr, h);
int i = (l - 1);
for (int j = l; j <= h- 1; j++)
{
if (*get_vec_elem(arr, j) >= x)
{
i++;
swap (get_vec_elem(arr,i), get_vec_elem(arr,j));
swap_idx(&indices[i], &indices[j]);
}
}
swap (get_vec_elem(arr, i + 1), get_vec_elem(arr, h));
swap_idx(&indices[i + 1], &indices[h]);
return (i + 1);
}
/* A[] --> Array to be sorted,
l --> Starting index,
h --> Ending index */
void quickSortIterative (Vector* arr, __global int* indices,
__global int *stack, int l, int h)
{
// Create an auxiliary stack
// initialize top of stack
int top = -1;
// push initial values of l and h to stack
stack[ ++top ] = l;
stack[ ++top ] = h;
// Keep popping from stack while is not empty
while ( top >= 0 )
{
// Pop h and l
h = stack[ top-- ];
l = stack[ top-- ];
// Set pivot element at its correct position
// in sorted array
int p = partition( arr, indices, l, h );
// If there are elements on left side of pivot,
// then push left side to stack
if ( p-1 > l )
{
stack[ ++top ] = l;
stack[ ++top ] = p - 1;
}
// If there are elements on right side of pivot,
// then push right side to stack
if ( p+1 < h )
{
stack[ ++top ] = p + 1;
stack[ ++top ] = h;
}
}
}
__kernel void topkv2_quicksort(VECTOR_DECLARATION(input),
VECTOR_DECLARATION(topk_values), VECTOR_DECLARATION(topk_indices),
__global int* indices, __global int* temp_stack, int k, int n)
{
Vector input = CONVERT_TO_VECTOR_STRUCT_NO_STEP(input);
Vector topk_values = CONVERT_TO_VECTOR_STRUCT_NO_STEP(topk_values);
Vector topk_indices = CONVERT_TO_VECTOR_STRUCT_NO_STEP(topk_indices);
for( int i = 0; i < n; ++i )
{
indices[i] = i;
}
quickSortIterative(&input, indices, temp_stack, 0, n-1);
// extract k items.
for(int i = 0; i < k; ++i)
{
*get_vec_elem(&topk_values, i) = *get_vec_elem(&input, i);
*get_vec_elem_int(&topk_indices, i) = indices[i];
}
}
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