private double edgeSample()

in commons-rng-sampling/src/main/java/org/apache/commons/rng/sampling/distribution/ZigguratSampler.java [607:641]

• 19 lines of code
• 5 McCabe index (conditional complexity)

        private double edgeSample(long xx) {
            int j = selectRegion();
            if (j != 0) {
                // Expected overhang frequency = 0.966972
                return sampleOverhang(j, xx);
            }
            // Expected tail frequency = 0.033028 (recursion)

            // xx must be discarded as the lower bits have already been used to generate i

            // If the tail then exploit the memoryless property of the exponential distribution.
            // Perform a new sample and add it to the start of the tail.
            // This loop sums tail values until a sample can be returned from the exponential.
            // The sum is added to the final sample on return.
            double x0 = X_0;
            for (;;) {
                // Duplicate of the sample() method
                final long x = nextLong();
                final int i = ((int) x) & 0xff;

                if (i < I_MAX) {
                    // Early exit.
                    return x0 + X[i] * (x >>> 1);
                }

                // Edge of the ziggurat
                j = selectRegion();
                if (j != 0) {
                    return x0 + sampleOverhang(j, x);
                }

                // Add another tail sample
                x0 += X_0;
            }
        }