Listing 8.13 contains a mistake (on github and in the book as well)

If you run the parallel_partial_sum algorithm on the following data set: {1, 2, 3, 4, 5}, you will get the result {1, 3, 5, 10, 15} instead of {1, 3, 6, 10, 15}. This is because the first element of the buffer must be initialized with the *first value like this:
buffer[0] = *first;
after the following line:

ccia_code_samples/listings/listing_8.13.cpp

Line 86 in 6e7ae1d

std::vector<value_type> buffer(length);

There's also unfinished join_threads implementation, unused last parameter in operator(), and also unused block_start variable.

I'm using 1..100 as dataset, a few answer is incorrect even after initialization. :(

I see what's going on, buffer must keep updated when update_source is false in process_element.

if (update_source) {
  ith_element = buffer[i];
} else {
  buffer[i] = ith_element;
}

Thanks for helping with this, you two - PR attached above.