Add an option to log all failed parameter sets to a file

cosmosis/main.py

@@ -332,6 +332,14 @@ def run_cosmosis(ini, pool=None, pipeline=None, values=None, priors=None, overri
 
     number_samplers = len(sampler_classes)
 
+    if ini.has_option("pipeline", "failure_log"):
+        filename = ini.get("pipeline", "failure_log")
+        failure_log_file = mpi_pool.MPILogFile(filename, pool)
+        pipeline.set_failure_log_file(failure_log_file)
+    else:
+        failure_log_file = None
+
+
 
     #To start with we do not have any estimates of 
     #anything the samplers might give us like centers
@@ -440,6 +448,9 @@ def run_cosmosis(ini, pool=None, pipeline=None, values=None, priors=None, overri
     if cleanup_pipeline:
         pipeline.cleanup()
 
+    if failure_log_file is not None:
+        failure_log_file.close()
+
     if profile_cpu:
         profile.disable()
         if (pool is not None) and (not smp):

cosmosis/runtime/mpi_pool.py

@@ -124,3 +124,39 @@ def __enter__(self):
 
     def __exit__(self, *args):
         self.close()
+
+class MPILogFile:
+    def __init__(self, filename, pool=None):
+        if hasattr(pool, "comm"):
+            self.comm = pool.comm
+        elif pool is None:
+            self.comm = None
+        else:
+            raise ValueError("Failure logging from multiple processes does not yet work using multiprocessing with --smp, only MPI using --mpi")
+
+        self.filename = filename
+        if self.comm is None:
+            self.file = open(filename, "w")
+        else:
+            from mpi4py import MPI
+            self.MPI = MPI
+            self.file = MPI.File.Open(self.comm, filename, MPI.MODE_WRONLY | MPI.MODE_CREATE)
+
+    def write(self, message):
+        if self.comm is None:
+            self.file.write(message)
+        else:
+            message = message.encode("utf-8")
+            self.file.Write_shared(message)
+
+    def __del__(self):
+        if self.file is not None:
+            self.close()
+
+    def close(self):
+        if self.comm is None:
+            self.file.close()
+        else:
+            self.file.Close()
+        self.file = None
+

cosmosis/runtime/pipeline.py

@@ -411,8 +411,23 @@ def __init__(self, arg=None, load=True, modules=None):
                     print("and use the cached results from the first run for everything before that.")
                     print("except the input parameter values. Think about this to check it's what you want.")
                 self.shortcut_module = index
+        # Add a log file where failures are sent
+        # We only set this is a method instead of an init variable
+        # because we may want to activate it on pipelines created
+        # by the user and sent to run_cosmosis
+        self.failure_log_file = None
 
+    def set_failure_log_file(self, failure_log_file):
+        """
+        Set the file where the pipeline will log failures.
 
+        Parameters
+        ----------
+        failure_log_file : file-like object
+            The file where the pipeline will log failures.
+            This can be a regular file or an MPILogFile object
+        """
+        self.failure_log_file = failure_log_file
 
     def find_module_file(self, path):
         u"""Find a module file, which is assumed to be either absolute or relative to COSMOSIS_SRC_DIR"""
@@ -1113,6 +1128,9 @@ def run_parameters(self, p, check_ranges=False, all_params=False):
             return data
         else:
             sys.stderr.write("Pipeline failed on these parameters: {}\n".format(p))
+            if self.failure_log_file is not None:
+                msg = " ".join([str(x) for x in p])
+                self.failure_log_file.write(msg + "\n")
             return None
 
 

cosmosis/test/test_pipeline.py

@@ -3,7 +3,7 @@
 from cosmosis.samplers.sampler import Sampler
 from cosmosis.runtime.prior import TruncatedGaussianPrior, DeltaFunctionPrior
 from cosmosis.output.in_memory_output import InMemoryOutput
-from cosmosis.main import run_cosmosis, parser
+from cosmosis.main import run_cosmosis, parser, mpi_pool
 import numpy as np
 import os
 import tempfile
@@ -265,6 +265,46 @@ def log_like(p):
     assert len(r.extra) == 0
 
 
+def test_failure_log():
+    def log_like(p):
+        if p[0] < 0:
+            print("Deliberately failing pipeline ...")
+            raise ValueError("p0 must be positive")
+        return -0.5 * np.sum(p**2)
+
+    param_ranges = [
+        (-3.0,  0.0,  3.0),
+        (-3.0,  0.0,  3.0),
+        (-3.0,  0.0,  3.0),
+        (-3.0,  0.0,  3.0),
+    ]
+
+    with tempfile.TemporaryDirectory() as dirname:
+        logname = f"{dirname}/failure.log"
+        failure_log = mpi_pool.MPILogFile(logname)
+
+        pipeline = LikelihoodPipeline.from_likelihood_function(log_like, param_ranges)
+        pipeline.set_failure_log_file(failure_log)
+        # two that should work and produce nothing
+        # and two that should log some errors
+        param_sets = [
+            [0.0,0.0,0.0,0.0],
+            [1.0,0.0,0.0,0.0],
+            [-1.0,0.0,0.0,4.0],
+            [-2.0,0.0,0.0,8.0],
+        ]
+        print("Pipeline errors are expected below - we are testing logging of them")
+        for p in param_sets:
+            pipeline.run_parameters(p)
+
+        failure_log.close()
+        with open(logname) as f:
+            lines = f.readlines()
+        assert len(lines) == 2
+        assert lines[0].strip() == "-1.0 0.0 0.0 4.0"
+        assert lines[1].strip() == "-2.0 0.0 0.0 8.0"
+
+
 
 if __name__ == '__main__':
     test_script_skip()

cosmosis/version.py

@@ -1 +1 @@
-__version__ = '3.10'
+__version__ = '3.11'