should be using placeholder instead of rate vertex directly.
@@ -85,7 +85,7 @@ public class ExponentialVertex extends DoubleVertex implements Differentiable, P
final DoubleVertex xLessThanZero = xPlaceholder.toLessThanMask(0.);
final DoubleVertex negXMinusADivB = xPlaceholder.unaryMinus().div(ratePlaceholder);
- final DoubleVertex negXMinusADivBMinusLogB = negXMinusADivB.minus(rate.log());
+ final DoubleVertex negXMinusADivBMinusLogB = negXMinusADivB.minus(ratePlaceholder.log());
final DoubleVertex logProbOutput = negXMinusADivBMinusLogB.setWithMask(xLessThanZero, Double.NEGATIVE_INFINITY);
