public static FastLoadedDiceRollerDiscreteSampler of()

in commons-rng-sampling/src/main/java/org/apache/commons/rng/sampling/distribution/FastLoadedDiceRollerDiscreteSampler.java [397:428]

• 20 lines of code
• 4 McCabe index (conditional complexity)

    public static FastLoadedDiceRollerDiscreteSampler of(UniformRandomProvider rng,
                                                         double[] weights,
                                                         int alpha) {
        final int n = checkWeightsNonZeroLength(weights);

        // Convert floating-point double to a relative weight
        // using a shifted integer representation
        final long[] frequencies = new long[n];
        final int[] offsets = new int[n];
        convertToIntegers(weights, frequencies, offsets, alpha);

        // Obtain indices of non-zero weights
        final int[] indices = indicesOfNonZero(frequencies);

        // Edge case for 1 non-zero weight.
        if (indices.length == 1) {
            return new FixedValueDiscreteSampler(indexOfNonZero(frequencies));
        }

        final BigInteger m = sum(frequencies, offsets, indices);

        // Use long arithmetic if possible. This occurs when the weights are similar in magnitude.
        if (m.compareTo(MAX_LONG) <= 0) {
            // Apply the offset
            for (int i = 0; i < n; i++) {
                frequencies[i] <<= offsets[i];
            }
            return createSampler(rng, frequencies, indices, m.longValue());
        }

        return createSampler(rng, frequencies, offsets, indices, m);
    }