#!/usr/bin/env python
# coding: utf-8

# # How to generate error bars for 2Q-GST
# 

# In[1]:


import pygsti
import time

#If we were using MPI
# from mpi4py import MPI
# comm = MPI.COMM_WORLD
comm = None

#Load the 2-qubit results (if you don't have this directory, run the 2Q-GST example)
results = pygsti.io.load_results_from_dir("example_files/My2QExample", "StandardGST")

#Set a memory limit
print("Memory limit was = ", results.estimates['CPTP'].parameters.get('memLimit',"none given"))
results.estimates['CPTP'].parameters['memLimit'] = 2.5*(1024.0)**3 # 2.5GB
print("Memory limit is now = ", results.estimates['CPTP'].parameters['memLimit'])


# In[2]:


# error bars in reports require the presence of a fully-initialized
# "confidence region factory" within the relevant Estimate object.
# In most cases "fully-initialized" means that a Hessian has been 
# computed and projected onto the non-gauge space.
start = time.time()

# initialize a factory for the 'go0' gauge optimization within the 'default' estimate
crfact = results.estimates['CPTP'].add_confidence_region_factory('stdgaugeopt', 'final')
crfact.compute_hessian(comm=comm) #optionally use multiple processors
crfact.project_hessian('intrinsic error')

end = time.time()
print("Total time=%f hours" % ((end - start) / 3600.0))


# Note above cell was executed for demonstration purposes, and was **keyboard-interrupted intentionally** since it would have taken forever on a single processor.

# In[ ]:


#write results back to disk
results.write()


# In[ ]: