diff --git a/examples/run_small_heuristic.sh b/examples/run_small_heuristic.sh
new file mode 100755
index 0000000..069333a
--- /dev/null
+++ b/examples/run_small_heuristic.sh
@@ -0,0 +1,10 @@
+
+multiraxml=../multi-raxml/multi-raxml.py
+output=results/small_heuristic
+msa_directory=data/small/fasta_files/
+raxml_global_options=data/small/raxml_global_options.txt
+cores=4
+
+rm -rf ${output}
+python3 ${multiraxml} -a ${msa_directory} -o ${output} -r ${raxml_global_options} -c ${cores} --percentage-jobs-double-core 0
+
diff --git a/examples/run_small_onecore.sh b/examples/run_small_onecore.sh
new file mode 100755
index 0000000..305571a
--- /dev/null
+++ b/examples/run_small_onecore.sh
@@ -0,0 +1,10 @@
+
+multiraxml=../multi-raxml/multi-raxml.py
+output=results/small_onecore
+msa_directory=data/small/fasta_files/
+raxml_global_options=data/small/raxml_global_options.txt
+cores=4
+
+rm -rf ${output}
+python ${multiraxml} -a ${msa_directory} -o ${output} -r ${raxml_global_options} -c ${cores} --scheduler onecore
+
diff --git a/multi-raxml/mr_arguments.py b/multi-raxml/mr_arguments.py
index a8d7610..d14307a 100644
--- a/multi-raxml/mr_arguments.py
+++ b/multi-raxml/mr_arguments.py
@@ -46,6 +46,11 @@ def parse_arguments():
       choices=["split", "onecore"],
       default="split",
       help="Sceduling strategy. onecore might be interesting for debugging crashing jobs")
+  parser.add_argument("--core-assignment",
+      dest="core_assignment",
+      choices=["high", "medium", "low"],
+      default="medium",
+      help="Policy to decide the per-job number of cores (low favors a low per-job number of cores)")
   # raxml arguments
   parser.add_argument("--per-msa-raxml-parameters", 
       dest="per_msa_raxml_parameters", 
@@ -71,6 +76,11 @@ def parse_arguments():
       type=int,
       default=0,
       help="The number of bootstrap trees to compute")
+  parser.add_argument("--percentage-jobs-double-cores",
+      dest="percentage_jobs_double_cores",
+      type=float,
+      default=0.03,
+      help="Percentage (between 0 and 1) of jobs that will receive twice more cores")
   # modeltest arguments
   parser.add_argument("-m", "--use-modeltest",
       dest="use_modeltest",
@@ -94,11 +104,6 @@ def parse_arguments():
       action="store_true",
       default=False,
       help="For experimenting only! Removes the sorting step in the scheduler")
-  parser.add_argument("--core-assignment",
-      dest="core_assignment",
-      choices=["high", "medium", "low"],
-      default="medium",
-      help="Policy to decide the per-job number of cores (low favors a low per-job number of cores)")
   
 
   op = parser.parse_args()
diff --git a/multi-raxml/mr_raxml.py b/multi-raxml/mr_raxml.py
index 29ac381..c5bfa04 100644
--- a/multi-raxml/mr_raxml.py
+++ b/multi-raxml/mr_raxml.py
@@ -41,7 +41,7 @@ def parse_msa_info(log_file, msa, core_assignment):
   if (msa.sites * msa.taxa == 0):
     msa.valid = False
 
-def improve_cores_assignment(msas):
+def improve_cores_assignment(msas, op):
   average_taxa = 0
   max_taxa = 0
   average_sites = 0
@@ -54,18 +54,20 @@ def improve_cores_assignment(msas):
     max_taxa = max(max_taxa, msa.taxa)
     max_sites = max(max_sites, msa.patterns)
   taxa_numbers.sort()
-  limit_taxa = taxa_numbers[(len(msas) * 97) // 100]
-  print("Limit taxa: " + str(limit_taxa))
   average_taxa /= len(msas)
   average_sites /= len(msas)
   print("Average number of taxa: " + str(average_taxa))
   print("Max number of taxa: " + str(max_taxa))
   print("Average number of sites: " + str(average_sites))
   print("Max number of sites: " + str(max_sites))
-  for name, msa in msas.items():
-    if (msa.taxa < limit_taxa):
-      if (msa.cores > 1):
-        msa.cores = msa.cores // 2
+  if (op.percentage_jobs_double_cores > 0.0):
+    ratio = 1.0 - op.percentage_jobs_double_cores
+    limit_taxa = taxa_numbers[int(float(len(msas)) * ratio)]
+    print("Limit taxa: " + str(limit_taxa))
+    for name, msa in msas.items():
+      if (msa.taxa < limit_taxa):
+        if (msa.cores > 1):
+          msa.cores = msa.cores // 2
 
 
 def run_parsing_step(msas, library, scheduler, parse_run_output_dir, cores):
@@ -89,8 +91,9 @@ def run_parsing_step(msas, library, scheduler, parse_run_output_dir, cores):
       writer.write("\n")
   mr_scheduler.run_mpi_scheduler(library, scheduler, parse_commands_file, parse_run_output_dir, cores)  
  
-def analyse_parsed_msas(msas, core_assignment, output_dir):
+def analyse_parsed_msas(msas, op, output_dir):
   """ Analyse results from run_parsing_step and store them into msas """
+  core_assignment = op.core_assignment
   parse_run_output_dir = os.path.join(output_dir, "parse_run")
   parse_run_results = os.path.join(parse_run_output_dir, "results")
   invalid_msas = []
@@ -103,7 +106,7 @@ def analyse_parsed_msas(msas, core_assignment, output_dir):
     parse_result = parse_msa_info(parse_run_log, msa, core_assignment)
     if (not msa.valid):
       invalid_msas.append(msa)      
-  improve_cores_assignment(msas)
+  improve_cores_assignment(msas, op)
   if (len(invalid_msas) > 0):
     invalid_msas_file = os.path.join(output_dir, "invalid_msas.txt")
     print("[Warning] Found " + str(len(invalid_msas)) + " invalid MSAs (see " + invalid_msas_file + ")") 
diff --git a/multi-raxml/multi-raxml.py b/multi-raxml/multi-raxml.py
index 3885acb..b0bd698 100644
--- a/multi-raxml/multi-raxml.py
+++ b/multi-raxml/multi-raxml.py
@@ -54,7 +54,7 @@ def main_raxml_runner(op):
     mr_raxml.run_parsing_step(msas, raxml_library, op.scheduler, os.path.join(output_dir, "parse_run"), op.cores)
     mr_checkpoint.write_checkpoint(output_dir, 1)
     timed_print(start, "end of parsing mpi-scheduler run")
-  mr_raxml.analyse_parsed_msas(msas, op.core_assignment, output_dir)
+  mr_raxml.analyse_parsed_msas(msas, op, output_dir)
   timed_print(start, "end of anlysing parsing results") 
   if (op.use_modeltest):
     if (checkpoint < 2):