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

# # Using LHS Value to Debug An Infeasible Problem
# 
# This notebook aims to show how to use the left-hand side (LHS) value (`Constraint.e`) to debug an infeasible problem.
# 
# The LHS value is the value of the left-hand side of the equation. It is useful to check which constraints are violated.

# In[1]:


import ams


# In[2]:


ams.config_logger(stream_level=20)


# First, let's solve a DCOPF.

# In[3]:


sp = ams.load(ams.get_case('matpower/case14.m'),
              no_output=True)


# In[4]:


sp.DCOPF.run(solver='CLARABEL')


# In[5]:


sp.DCOPF.pg.v.round(2)


# Then, we can lower down the generator maximum output to create an infeasible problem.

# In[6]:


sp.StaticGen.set(src='pmax', attr='v', idx=[1, 2, 3, 4, 5], value=0.5)


# Remember to update the corresponding parameters in the routine.

# In[7]:


sp.DCOPF.update('pmax')


# Now, we can see that the problem is infeasible.

# In[8]:


sp.DCOPF.run(solver='CLARABEL')


# Then, we can turn off some constraints and sovle it again.

# In[9]:


sp.DCOPF.disable(['pglb', 'pgub'])


# Note that since there are some constraints touched, the OModel will be updated automatically.

# In[10]:


sp.DCOPF.run(solver='CLARABEL')


# In[11]:


sp.DCOPF.pg.v


# Since all the inequality constraints are written in the form of $Ax -b \leq 0$, we can check the violated constraints by finding the those with positive `Constraint.e`.

# In[12]:


sp.DCOPF.pgub.e


# In[13]:


sp.DCOPF.pglb.e