* Copyright (c) 2014, ArrayFire
* All rights reserved.
* This file is distributed under 3-clause BSD license.
* The complete license agreement can be obtained at:
#include <arrayfire.h>
#include <math.h>
#include <stdio.h>
#include <af/util.h>
#include <string>
#include <vector>
#include "mnist_common.h"
using namespace af;
// Get accuracy of the predicted results
float accuracy(const array &predicted, const array &target) {
return 100 * count<float>(predicted == target) / target.elements();
// Calculate all the distances from testing set to training set
array distance(array train, array test) {
const int feat_len = train.dims(1);
const int num_train = train.dims(0);
const int num_test = test.dims(0);
array dist = constant(0, num_train, num_test);
// Iterate over each attribute
for (int ii = 0; ii < feat_len; ii++) {
// Get a attribute vectors
array train_i = train(span, ii);
array test_i = test(span, ii).T();
// Tile the vectors to generate matrices
array train_tiled = tile(train_i, 1, num_test);
array test_tiled = tile(test_i, num_train, 1);
// Add the distance for this attribute
dist = dist + abs(train_tiled - test_tiled);
dist.eval(); // Necessary to free up train_i, test_i
return dist;
array knn(array &train_feats, array &test_feats, array &train_labels) {
// Find distances between training and testing sets
array dist = distance(train_feats, test_feats);
// Find the neighbor producing the minimum distance
array val, idx;
min(val, idx, dist);
// Return the labels
return train_labels(idx);
void knn_demo(bool console, int perc) {
array train_images, train_labels;
array test_images, test_labels;
int num_train, num_test, num_classes;
// Load mnist data
float frac = (float)(perc) / 100.0;
setup_mnist<false>(&num_classes, &num_train, &num_test, train_images,
test_images, train_labels, test_labels, frac);
int feature_length = train_images.elements() / num_train;
array train_feats = moddims(train_images, feature_length, num_train).T();
array test_feats = moddims(test_images, feature_length, num_test).T();
// Get the predicted results
array res_labels = knn(train_feats, test_feats, train_labels);
double test_time = timer::stop();
// Results
printf("Accuracy on testing data: %2.2f\n",
accuracy(res_labels, test_labels));
printf("Prediction time: %4.4f\n", test_time);
if (!console) {
display_results<false>(test_images, res_labels, test_labels, 20);
int main(int argc, char **argv) {
int device = argc > 1 ? atoi(argv[1]) : 0;
bool console = argc > 2 ? argv[2][0] == '-' : false;
int perc = argc > 3 ? atoi(argv[3]) : 60;
try {
knn_demo(console, perc);
} catch (af::exception &ae) { std::cerr << ae.what() << std::endl; }
return 0;
dim4 dims() const
Get dimensions of the array.
array T() const
Get the transposed the array.
dim_t dims[4]
Definition: dim4.hpp:28
An ArrayFire exception class.
Definition: exception.h:22
virtual const char * what() const
Returns an error message for the exception in a string format.
Definition: exception.h:46
AFAPI array abs(const array &in)
C++ Interface for absolute value.
array constant(T val, const dim4 &dims, const dtype ty=(af_dtype) dtype_traits< T >::ctype)
AFAPI void info()
AFAPI void setDevice(const int device)
Sets the current device.
AFAPI array moddims(const array &in, const unsigned ndims, const dim_t *const dims)
AFAPI array tile(const array &in, const unsigned x, const unsigned y=1, const unsigned z=1, const unsigned w=1)
static af::array array(af::dim4 idims, cl_mem buf, af::dtype type, bool retain=false)
Create an af::array object from an OpenCL cl_mem buffer.
Definition: opencl.h:327
AFAPI array min(const array &in, const int dim=-1)
C++ Interface for minimum values in an array.
Definition: algorithm.h:15
AFAPI seq span
A special value representing the entire axis of an af::array.