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// 8.5 us for 10k doubles: 2.3 GFlops
public double dotProduct(double [] ws, double[] xs) {
   double result = 0.0;
    for (int i=0; i < ws.length; ++i) {
      result += ws[i] * xs[i];
    }
   return result;
}

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;; 8.5 us for 10k doubles: 2.3 GFlops
(require '[hiphip.double :as dbl])
(defn dot-product [ws xs]
  (dbl/asum [x xs w ws] (* x w)))

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(dbl/aset xs i (* 2.0 (dbl/aget xs (inc i)))))

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(defn add-in-place! 
  "Modify xs, incrementing each element by the corresponding element of ys"
  [xs ys]
  (dbl/afill! [x xs y ys] (+ x y)))

(defn pointwise-product 
  "Produce a new double array with the product of corresponding elements of xs and ys"
  [xs ys]
  (dbl/amap [x xs y ys] (* x y)))

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(defn pointwise-product 
  "Produce a new double array with the product of corresponding elements of xs and ys"
  [xs ys]
  (dbl/amap [x xs y ys] (* x y)))

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(defn standard-deviation [xs]
  (let [mean (dbl/amean xs)
        mean-sq (/ (dbl/asum [x xs] (* x x))
                   (dbl/alength xs))]
    (Math/sqrt (- mean-sq (* mean mean)))))

(= 1 (dbl/amax-index (double-array [1.0 3.0 2.0])))

(defn max-normalize [xs]
  (let [m (dbl/amax xs)]

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(defn top-k 
  "Return the top k elements of xs according to score-fn"
  [k score-fn xs]
  (let [n (count xs)
        scores (dbl/amake [i n] (score-fn (nth xs i)))
        ^ints idxs (dbl/amax-indices scores k)]
    (seq (hiphip.array/amake Object [i k] (nth xs (aget idxs (- n i 1)))))))

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(defn fill-string-pointwise-product
  [^{:tag "[Ljava.lang.String;"} os ^doubles xs ^longs ys]
  (array/afill! String [_ os x xs y ys] (str (* x y))))

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;; Initialize xs to (range (alength xs)).
(afill! [[i x] xs] i)

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;; Clear Leiningen's default jvm-opts.
:jvm-opts ^:replace []