an array of Operations that we want the derivative of objective with respect to.
the value used to scale the size of the gradient used in the update rule
scaling factor for the previous update
A delegate that is used to actually perform the update steps. The optimised values are stored in the "default" attributes of the elements of wrt.
1 import std.random : uniform; 2 3 //Generate some points 4 auto xdata = new float[100]; 5 auto ydata = new float[100]; 6 7 foreach(i; 0 .. 100) 8 { 9 xdata[i] = uniform(-10.0f, 10.0f); 10 ydata[i] = 3.0f * xdata[i] + 2.0f; 11 } 12 13 //Create the model 14 auto x = float32([]); 15 auto m = float32([]); 16 auto c = float32([]); 17 18 auto yhat = m * x + c; 19 auto y = float32([]); 20 21 //Create an SGD updater 22 auto updater = sgd([(yhat - y) * (yhat - y)], [m, c], null, float32([], [0.001f]), float32([], [0.9f])); 23 24 //Iterate for a while 25 float loss; 26 27 for(size_t i = 0; i < 300; i++) 28 { 29 size_t j = i % 100; 30 31 loss = updater([ 32 x: Buffer(xdata[j .. j + 1]), 33 y: Buffer(ydata[j .. j + 1]) 34 ])[0].as!float[0]; 35 } 36 37 //Print the loss after 500 iterations. Let the user decide whether it's good enough to be considered a pass. 38 import std.stdio : writeln; 39 writeln( 40 "SGD loss: ", loss, " ", 41 "m=", m.value.as!float[0], ", ", 42 "c=", c.value.as!float[0], " ", 43 "(expected m=3, c=2)");
Creates a delegate that can be used to perform a step using the stochastic gradient descent update rule.
This function relies on automatic differentiation, so the objective (which must have a volume of 1) must be differentiable w.r.t. all elements of wrt. The returned delegate performs minimisation.