Use rounding for mortality

[wenzeslaus]

Replaced flooring by rounding in computation of mortality in index/cohort for a cell.

• PR in rpops with this change Use rounding for mortality rpops#204
• PR in r.pops.spread with this change Use rounding for mortality r.pops.spread#78

[wenzeslaus]

This causes the biggest changes in the outputs. Text output from r.pops.spread tests:

======================================================================
FAIL: test_outputs_mortality (__main__.TestSpread.test_outputs_mortality)
Check dead output of mortality
----------------------------------------------------------------------
...
AssertionError: r.univar map=average percentile=90.0 nprocs=1 separator== format=plain -g difference:
mismatch values (key, reference, actual): [('max', 6, 4.2), ('mean', 0.606, 0.14476843910806)]
command: r.univar map=average percentile=90.0 nprocs=1 separator== format=plain -g {'map': 'average', 'separator': '=', 'flags': 'g'}

======================================================================
FAIL: test_outputs_mortality_many_runs (__main__.TestSpread.test_outputs_mortality_many_runs)
Check mortality with many stochastic runs
----------------------------------------------------------------------
...
AssertionError: r.univar map=average percentile=90.0 nprocs=1 separator== format=plain -g difference:
mismatch values (key, reference, actual): [('mean', 0.653, 0.142562178387642)]
command: r.univar map=average percentile=90.0 nprocs=1 separator== format=plain -g {'map': 'average', 'separator': '=', 'flags': 'g'}

======================================================================
FAIL: test_outputs_mortality_pesticide_treatment (__main__.TestSpread.test_outputs_mortality_pesticide_treatment)
Check mortality together with pesticide treatment (all_infected_in_cell)
----------------------------------------------------------------------
...
AssertionError: r.univar map=dead_2022_12_31 percentile=90.0 nprocs=1 separator== format=plain -g difference:
mismatch values (key, reference, actual): [('mean', 0.675, 0.327151229273871)]
command: r.univar map=dead_2022_12_31 percentile=90.0 nprocs=1 separator== format=plain -g {'map': 'dead_2022_12_31', 'separator': '=', 'flags': 'g'}

======================================================================
FAIL: test_outputs_mortality_treatment (__main__.TestSpread.test_outputs_mortality_treatment)
Check mortality together with treatment
----------------------------------------------------------------------
...
AssertionError: r.univar map=dead_2019_12_31 percentile=90.0 nprocs=1 separator== format=plain -g difference:
mismatch values (key, reference, actual): [('sum', 782, 1196)]
command: r.univar map=dead_2019_12_31 percentile=90.0 nprocs=1 separator== format=plain -g {'map': 'dead_2019_12_31', 'separator': '=', 'flags': 'g'}

----------------------------------------------------------------------

[wenzeslaus]

The rounding causes higher mortality which with time causes lower infection counts.

(infected is an average of number of infected over 5 runs; dead is accumulated number of dead in the first run; 50 runs seed 90385)

[wenzeslaus]

The following figures are using mortality rate 0.4 for the new code which brings the results closer to the original code with mortality rate 0.5.