From d135faa35f6ca02b70db9764f85b57be64e8f299 Mon Sep 17 00:00:00 2001
From: Benedikt Volkel <benedikt.volkel@cern.ch>
Date: Thu, 21 Mar 2024 14:36:20 +0100
Subject: [PATCH] [SimWF] Recompute number of workers used in TFs

---
 MC/bin/o2dpg_sim_workflow.py   |  7 +++++--
 MC/bin/o2dpg_workflow_utils.py | 22 ++++++++++++++++++++++
 2 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/MC/bin/o2dpg_sim_workflow.py b/MC/bin/o2dpg_sim_workflow.py
index d1ae5ced4..0e8638259 100755
--- a/MC/bin/o2dpg_sim_workflow.py
+++ b/MC/bin/o2dpg_sim_workflow.py
@@ -34,7 +34,7 @@
 
 sys.path.append(join(dirname(__file__), '.', 'o2dpg_workflow_utils'))
 
-from o2dpg_workflow_utils import createTask, createGlobalInitTask, dump_workflow, adjust_RECO_environment, isActive, activate_detector, deactivate_detector
+from o2dpg_workflow_utils import createTask, createGlobalInitTask, dump_workflow, adjust_RECO_environment, isActive, activate_detector, deactivate_detector, compute_n_workers
 from o2dpg_qc_finalization_workflow import include_all_QC_finalization
 from o2dpg_sim_config import create_sim_config, create_geant_config, constructConfigKeyArg
 
@@ -638,6 +638,9 @@ def getDPL_global_options(bigshm=False, ccdbbackend=True):
      QEDdigiargs=' --simPrefixQED qed_' + str(tf) +  ' --qed-x-section-ratio ' + str(QEDXSecExpected/PbPbXSec)
      workflow['stages'].append(QED_task)
 
+   # recompute the number of workers to increase CPU efficiency
+   NWORKERS = compute_n_workers(INTRATE, COLTYPE)
+
    # produce the signal configuration
    SGN_CONFIG_task=createTask(name='gensgnconf_'+str(tf), tf=tf, cwd=timeframeworkdir)
    SGN_CONFIG_task['cmd'] = 'echo "placeholder / dummy task"'
@@ -1300,7 +1303,7 @@ def addQCPerTF(taskName, needs, readerCommand, configFilePath, objectsFile=''):
                    needs=[PHSRECOtask['name']],
                    readerCommand='o2-phos-reco-workflow --input-type cells --output-type clusters --disable-mc --disable-root-output',
                    configFilePath='json://${O2DPG_ROOT}/MC/config/QC/json/phs-cells-clusters-task.json')
-                   
+
      ### MID
      if isActive('MID'):
         addQCPerTF(taskName='MIDTaskQC',
diff --git a/MC/bin/o2dpg_workflow_utils.py b/MC/bin/o2dpg_workflow_utils.py
index 18fd600c9..6544c3a1b 100755
--- a/MC/bin/o2dpg_workflow_utils.py
+++ b/MC/bin/o2dpg_workflow_utils.py
@@ -24,6 +24,28 @@ def deactivate_detector(det):
 def isActive(det):
     return det not in INACTIVE_DETECTORS and ("all" in ACTIVE_DETECTORS or det in ACTIVE_DETECTORS)
 
+def compute_n_workers(interaction_rate, collision_system, n_workers_user=8, n_workers_min=1, interaction_rate_linear_below=300000):
+    """
+    Compute number of workers
+
+    n_workers = m * IR + b
+
+    based on
+    https://indico.cern.ch/event/1395900/contributions/5868567/attachments/2823967/4932440/20240320_slides_cpu_eff.pdf, slide 3
+
+    Assume n_workers_in=8 to be ideal for pp IR > interaction_rate_linear_below
+
+    Start with 1 worker at IR=0
+    Go linearly until interaction_rate_linear_below
+    """
+    if collision_system == "PbPb":
+        return n_workers_user
+
+    n_workers_min = max(1, n_workers_min)
+    m = (n_workers_user - n_workers_min) / interaction_rate_linear_below
+    # at least 1 worker
+    return min(1, round(m * interaction_rate + n_workers_min))
+
 def relativeCPU(n_rel, n_workers):
     # compute number of CPUs from a given number of workers
     # n_workers and a fraction n_rel