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machine_learning/perceptron.cpp
/*******************************************************
* Copyright (c) 2014, ArrayFire
* All rights reserved.
*
* This file is distributed under 3-clause BSD license.
* The complete license agreement can be obtained at:
* http://arrayfire.com/licenses/BSD-3-Clause
********************************************************/
#include <arrayfire.h>
#include <math.h>
#include <stdio.h>
#include <af/util.h>
#include <string>
#include <vector>
#include "mnist_common.h"
using namespace af;
float accuracy(const array &predicted, const array &target) {
array val, plabels, tlabels;
max(val, tlabels, target, 1);
max(val, plabels, predicted, 1);
return 100 * count<float>(plabels == tlabels) / tlabels.elements();
}
// Predict based on given parameters
array predict(const array &X, const array &Weights) {
return sigmoid(matmul(X, Weights));
}
array train(const array &X, const array &Y, double alpha = 0.1,
double maxerr = 0.05, int maxiter = 1000, bool verbose = false) {
// Initialize parameters to 0
array Weights = constant(0, X.dims(1), Y.dims(1));
for (int i = 0; i < maxiter; i++) {
array P = predict(X, Weights);
array err = Y - P;
float mean_abs_err = mean<float>(abs(err));
if (mean_abs_err < maxerr) break;
if (verbose && (i + 1) % 25 == 0) {
printf("Iter: %d, Err: %.4f\n", i + 1, mean_abs_err);
}
Weights = Weights + alpha * matmulTN(X, err);
}
return Weights;
}
void benchmark_perceptron(const array &train_feats, const array &train_targets,
const array test_feats) {
timer::start();
array Weights = train(train_feats, train_targets, 0.1, 0.01, 1000);
af::sync();
printf("Training time: %4.4lf s\n", timer::stop());
timer::start();
const int iter = 100;
for (int i = 0; i < iter; i++) {
array test_outputs = predict(test_feats, Weights);
test_outputs.eval();
}
af::sync();
printf("Prediction time: %4.4lf s\n", timer::stop() / iter);
}
// Demo of one vs all logistic regression
int perceptron_demo(bool console, int perc) {
array train_images, train_targets;
array test_images, test_targets;
int num_train, num_test, num_classes;
// Load mnist data
float frac = (float)(perc) / 100.0;
setup_mnist<true>(&num_classes, &num_train, &num_test, train_images,
test_images, train_targets, test_targets, frac);
// Reshape images into feature vectors
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();
train_targets = train_targets.T();
test_targets = test_targets.T();
// Add a bias that is always 1
train_feats = join(1, constant(1, num_train, 1), train_feats);
test_feats = join(1, constant(1, num_test, 1), test_feats);
// Train logistic regression parameters
array Weights = train(train_feats, train_targets, 0.1, 0.01, 1000, true);
// Predict the results
array train_outputs = predict(train_feats, Weights);
array test_outputs = predict(test_feats, Weights);
printf("Accuracy on training data: %2.2f\n",
accuracy(train_outputs, train_targets));
printf("Accuracy on testing data: %2.2f\n",
accuracy(test_outputs, test_targets));
benchmark_perceptron(train_feats, train_targets, test_feats);
if (!console) {
test_outputs = test_outputs.T();
test_targets = test_targets.T();
// Get 20 random test images.
display_results<true>(test_images, test_outputs, test_targets, 20);
}
return 0;
}
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 {
af::setDevice(device);
af::info();
return perceptron_demo(console, perc);
} catch (af::exception &ae) { std::cerr << ae.what() << std::endl; }
return 0;
}
arrayfire.h
af::array
A multi dimensional data container.
Definition array.h:37
af::array::dims
dim4 dims() const
Get dimensions of the array.
af::array::eval
void eval() const
Evaluate any JIT expressions to generate data for the array.
af::array::T
array T() const
Get the transposed the array.
af::array::elements
dim_t elements() const
Get the total number of elements across all dimensions of the array.
af::exception
An ArrayFire exception class.
Definition exception.h:22
af::exception::what
virtual const char * what() const
Returns an error message for the exception in a string format.
Definition exception.h:46
af::abs
array abs(const array &in)
C++ Interface to calculate the absolute value.
af::matmulTN
AFAPI array matmulTN(const array &lhs, const array &rhs)
C++ Interface to multiply two matrices.
af::constant
array constant(T val, const dim4 &dims, const dtype ty=(af_dtype) dtype_traits< T >::ctype)
C++ Interface to generate an array with elements set to a specified value.
af::info
AFAPI void info()
af::setDevice
AFAPI void setDevice(const int device)
Sets the current device.
af::sync
AFAPI void sync(const int device=-1)
Blocks until the device is finished processing.
af::join
AFAPI array join(const int dim, const array &first, const array &second)
C++ Interface to join 2 arrays along a dimension.
af::moddims
AFAPI array moddims(const array &in, const dim4 &dims)
C++ Interface to modify the dimensions of an input array to a specified shape.
af
Definition algorithm.h:15
util.h