Class HelperFns

src/com/winvector/opt/impl/HelperFns.java:13–166

import com.winvector.util.ThreadedReducer;

public class HelperFns {


	public static int argmax(final double[] pred) {
		int choice = 0;
		final int n = pred.length;
		for(int i=1;i<n;++i) {
			if(pred[i]>pred[choice]) {
				choice = i;
			}
		}
		return choice;
	}
	
	public static boolean isGoodPrediction(final double[] pred, final ExampleRow ei) {
		final int predi = argmax(pred);
		final boolean good = predi==ei.category();
		return good;
	}
	
	private static final class AccuracyCounter<T extends ExampleRow> implements ReducibleObserver<T,AccuracyCounter<T>> {
		public long n = 0;
		public long nGood = 0;
		private final DModel<T> fn;
		private final double[] x;
		private final double[] pred;
		
		public AccuracyCounter(final DModel<T> fn, final double[] x) {
			this.fn = fn;
			this.x = x;
			pred = new double[fn.noutcomes()];
		}
		
		@Override
		public void observe(final T ei) {
			if(ei.category()>=0) {
				fn.predict(x,ei,pred);
				final boolean good = (pred!=null)&&isGoodPrediction(pred,ei);
				if(good) {
					++nGood;
				}
				++n;
			}
		}

		@Override
		public void observe(final AccuracyCounter<T> o) {
			n += o.n;
			nGood += o.nGood;
		}

		@Override
		public AccuracyCounter<T> newObserver() {
			return new AccuracyCounter<T>(fn,x);
		}
	}
	
	public static <T extends ExampleRow> double accuracy(final DModel<T> fn, final Iterable<T> as, final double[] x) {