Hello all,

After reading the release notes of Stan 2.25 (!!) I am suddenly unsure if I am using `reduce_sum`

correctly.

For every `reduce_sum`

transition, I declare the accumulated log probability (`lp`

) to be 0 - `lp=0`

and accumulate it using `lp += ....`

until I return it. Please see the simplified example below:

```
functions {
real partial_sum(.....) {
real lp = 0;
lp += normal_lpdf(...);
lp += bernoulli_lpmf(...);
lp += wiener_lpdf(...);
.
.
return lp;
}
}
.
.
.
model {
target += reduce_sum(partial_sum, .......);
}
```

Is this correct? Or should I pass `target +=`

into `reduce_sum`

? Or am I completely off?

Thank you!