commons-numbers-arrays/src/main/java/org/apache/commons/numbers/arrays/QuickSelect.java [786:815]:
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        final int fp;
        final int s;
        int p;
        if (flags <= MODE_SAMPLING) {
            // Median into a 12th-tile
            fp = (r - l + 1) / 12;
            // Position the sample around the target k
            // Avoid bounds error due to rounding as (k-l)/(r-l) -> 1/12
            s = Math.max(k - mapDistance(k - l, l, r, fp), l + fp);
            p = k;
        } else {
            // i in 2nd quartile
            final int f = (r - l + 1) >> 2;
            final int f2 = f + f;
            final int end = l + f2;
            for (int i = l + f; i < end; i++) {
                Sorting.lowerMedian4(a, i - f, i, i + f, i + f2);
            }
            // i in 5th 12th-tile
            fp = f / 3;
            s = l + f + fp;
            // No adaption uses the middle to enforce strict margins
            p = s + (flags == MODE_ADAPTION ? mapDistance(k - l, l, r, fp) : (fp >>> 1));
        }
        final int e = s + fp - 1;
        for (int i = s; i <= e; i++) {
            Sorting.sort3(a, i - fp, i, i + fp);
        }
        p = quickSelectAdaptive(a, s, e, p, p, upper, MODE_FR_SAMPLING);
        return expandPartition(a, l, r, s, e, p, upper[0], upper);
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commons-numbers-arrays/src/main/java/org/apache/commons/numbers/arrays/QuickSelect.java [2045:2074]:
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        final int fp;
        final int s;
        int p;
        if (flags <= MODE_SAMPLING) {
            // Median into a 12th-tile
            fp = (r - l + 1) / 12;
            // Position the sample around the target k
            // Avoid bounds error due to rounding as (k-l)/(r-l) -> 1/12
            s = Math.max(k - mapDistance(k - l, l, r, fp), l + fp);
            p = k;
        } else {
            // i in 2nd quartile
            final int f = (r - l + 1) >> 2;
            final int f2 = f + f;
            final int end = l + f2;
            for (int i = l + f; i < end; i++) {
                Sorting.lowerMedian4(a, i - f, i, i + f, i + f2);
            }
            // i in 5th 12th-tile
            fp = f / 3;
            s = l + f + fp;
            // No adaption uses the middle to enforce strict margins
            p = s + (flags == MODE_ADAPTION ? mapDistance(k - l, l, r, fp) : (fp >>> 1));
        }
        final int e = s + fp - 1;
        for (int i = s; i <= e; i++) {
            Sorting.sort3(a, i - fp, i, i + fp);
        }
        p = quickSelectAdaptive(a, s, e, p, p, upper, MODE_FR_SAMPLING);
        return expandPartition(a, l, r, s, e, p, upper[0], upper);
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