Number of MPI tasks as derived database column

[sarats]

It would be good to add a database column containing the total number of MPI ranks for an experiment.

Example:
https://pace.ornl.gov/exp-details/73942
Total MPI ranks = 5120

MariaDB [pace]> select * from pelayout where expid=73942;
+--------+-------+-----------+----------+---------+-------+---------+-----------+--------+
| id | expid | component | comp_pes | root_pe | tasks | threads | instances | stride |
+--------+-------+-----------+----------+---------+-------+---------+-----------+--------+
| 664831 | 73942 | cpl | 4160 | 0 | 4160 | 1 | 1 | 1 |
| 664832 | 73942 | atm | 4160 | 0 | 4160 | 1 | 1 | 1 |
| 664833 | 73942 | lnd | 320 | 3840 | 320 | 1 | 1 | 1 |
| 664834 | 73942 | ice | 3840 | 0 | 3840 | 1 | 1 | 1 |
| 664835 | 73942 | ocn | 960 | 4160 | 960 | 1 | 1 | 1 |
| 664836 | 73942 | rof | 320 | 3840 | 320 | 1 | 1 | 1 |
| 664837 | 73942 | glc | 1 | 0 | 1 | 1 | 1 | 1 |
| 664838 | 73942 | wav | 1 | 0 | 1 | 1 | 1 | 1 |
| 664839 | 73942 | iac | 1 | 0 | 1 | 1 | 1 | 1 |
+--------+-------+-----------+----------+---------+-------+---------+-----------+--------+
9 rows in set (0.001 sec)

On first cut, we can get the grouping of processors as follows:

select root_pe,MAX(tasks) from pelayout where expid= 73942 group by root_pe;
+---------+------------+
| root_pe | MAX(tasks) |
+---------+------------+
| 0 | 4160 |
| 3840 | 320 |
| 4160 | 960 |
+---------+------------+

Now, we have to sum up the third row: 4160 + 960 = 5120.
We can probably get a better SQL statement to compute this.