public Builder<G, C> survivorsFraction(final double fraction) {
			return offspringFraction(1 - fraction);
		}
The survivor fraction. <i>Default values is set to {@code 0.4}.</i>
This method call is equivalent to
{@code offspringFraction(1 - survivorsFraction)} and will override
any previously set offspring-fraction.

@since 3.8

@see #offspringFraction(double)

@param fraction the survivor fraction
@return {@code this} builder, for command chaining
@throws java.lang.IllegalArgumentException if the fraction is not
        within the range [0, 1].
jenetics/src/main/java/io/jenetics/engine/Engine.java