nd4j-common/src/main/java/org/nd4j/linalg/util/BigDecimalMath.java
static public BigDecimal cbrt(final BigDecimal x) {
        if (x.compareTo(BigDecimal.ZERO) < 0) {
            return root(3, x.negate()).negate();
        } else {
            return root(3, x);
        }
    }
static public BigDecimal cbrt(final BigDecimal x) {
        if (x.compareTo(BigDecimal.ZERO) < 0) {
            return root(3, x.negate()).negate();
        } else {
            return root(3, x);
        }
    }
The cube root.

@param x The argument.
@return The cubic root of the BigDecimal rounded to the precision implied by x.
The sign of the result is the sign of the argument.