Added timestamp calculation to detsim city

Timestamp calculation is based on rate parameter and event number.

In this commit there are all the changes:
  - Added get_rate_safe() function to detsim/sensor_utils.py. This is
    a function to get rate value safely before generate timestamp (event_number / rate).
  - Implementation of calculated timestamp into MC_hits_from_files() and get rate safely
  - Added rate variable (0.5 Hz) to detsim.conf
  - Implemented rate parameter in detsim() function and MC_hits_from_files() call inside detsim()
  - Added test for get_rate_safe function.
  - Updated output file of test_detsim_exact

invisible_cities/cities/components.py

@@ -42,6 +42,7 @@
 from .. core   .random_sampling   import              NoiseSampler
 from .. detsim                    import          buffer_functions as  bf
 from .. detsim .sensor_utils      import             trigger_times
+from .. detsim .sensor_utils      import             get_rate_safe
 from .. detsim .sensor_utils      import          create_timestamp
 from .. reco                      import           calib_functions as  cf
 from .. reco                      import          sensor_functions as  sf
@@ -507,21 +508,23 @@ def hits_and_kdst_from_files(paths: List[str]) -> Iterator[Dict[str,Union[HitCol
                            timestamp = timestamp)
 
 
-def MC_hits_from_files(files_in : List[str]) -> Generator:
+def MC_hits_from_files(files_in : List[str], rate: float) -> Generator:
+    rate = get_rate_safe(rate)
     for filename in files_in:
         try:
             hits_df = load_mchits_df(filename)
         except tb.exceptions.NoSuchNodeError:
             continue
         for evt, hits in hits_df.groupby(level=0):
+            timestamp = create_timestamp(evt, rate)
             yield dict(event_number = evt,
                        x            = hits.x     .values,
                        y            = hits.y     .values,
                        z            = hits.z     .values,
                        energy       = hits.energy.values,
                        time         = hits.time  .values,
                        label        = hits.label .values,
-                       timestamp    = 0)
+                       timestamp    = timestamp)
 
 
 def sensor_data(path, wf_type):

invisible_cities/cities/detsim.py

@@ -121,7 +121,7 @@ def get_bin_edges(pmt_wfs, sipm_wfs):
 @city
 def detsim(*, files_in, file_out, event_range, print_mod, compression,
            detector_db, run_number, s1_lighttable, s2_lighttable, sipm_psf,
-           buffer_params, physics_params):
+           buffer_params, physics_params, rate):
 
     physics_params_ = physics_params.copy()
 
@@ -199,7 +199,7 @@ def detsim(*, files_in, file_out, event_range, print_mod, compression,
                                                        , int(buffer_params["length"] / buffer_params["sipm_width"]))
 
         write_nohits_filter   = fl.sink(event_filter_writer(h5out, "active_hits"), args=("event_number", "passed_active"))
-        result = fl.push(source= MC_hits_from_files(files_in),
+        result = fl.push(source= MC_hits_from_files(files_in, rate),
                          pipe  = fl.pipe( fl.slice(*event_range, close_all=True)
                                         , event_count_in.spy
                                         , print_every(print_mod)

invisible_cities/config/detsim.conf

@@ -34,3 +34,5 @@ compression = "ZLIB4"
 
 # How frequently to print events
 print_mod = 1
+
+rate = 0.5 * hertz

invisible_cities/detsim/sensor_utils.py

@@ -1,6 +1,7 @@
 import numpy  as np
 import tables as tb
 import pandas as pd
+import warnings
 
 from typing import Callable
 from typing import     List
@@ -14,6 +15,27 @@
 from .. io      .mcinfo_io import get_sensor_binning
 
 
+def get_rate_safe(rate: float) -> float:
+    """
+    Get rate value safely, and if it is zero, raise a warning.
+
+    Parameters
+    ----------
+    rate : float
+           Value of the rate.
+
+    Returns
+    -------
+    rate if rate != 0, else rate = 0.5
+    """
+    if rate == 0:
+        warnings.warn("Zero rate is unphysical, using default "
+                      "rate of 0.5 Hz instead")
+        return 0.5 / units.ms
+    else:
+        return rate
+
+
 def create_timestamp(event_number: Union[int, float],
                      rate        :            float ) -> float:
     """

invisible_cities/detsim/sensor_utils_test.py

@@ -12,6 +12,7 @@
 from . sensor_utils import pmt_and_sipm_bin_width
 from . sensor_utils import          trigger_times
 from . sensor_utils import       create_timestamp
+from . sensor_utils import          get_rate_safe 
 
 
 def test_trigger_times():
@@ -115,3 +116,15 @@ def test_create_timestamp_greater_with_greater_eventnumber():
     assert abs(timestamp_1) == timestamp_1
     assert timestamp_1      <  timestamp_2
     assert abs(timestamp_2) == timestamp_2
+
+
+@mark.filterwarnings("ignore:Zero rate")
+def test_get_rate_safe_allways_possitive():
+    """
+    Be sure that it woll always return the rate value such that
+    it is never unphysical.
+    """
+
+    rate = 0
+    assert get_rate_safe(rate) > 0
+