From f7f5c4ae9cfeddce07c792b97ed3dec81e516d83 Mon Sep 17 00:00:00 2001
From: Edward Burnell <eburn@mit.edu>
Date: Thu, 4 Aug 2016 07:09:05 -0700
Subject: [PATCH 01/12] don't autogenerate varkeys

---
 docs/source/examples/beam.py |  2 ++
 gpkit/constraints/costed.py  |  5 ++---
 gpkit/constraints/linked.py  |  4 ++++
 gpkit/constraints/model.py   |  1 +
 gpkit/constraints/set.py     | 18 +++++++-----------
 5 files changed, 16 insertions(+), 14 deletions(-)

diff --git a/docs/source/examples/beam.py b/docs/source/examples/beam.py
index 522b2175e..7cd0212b5 100644
--- a/docs/source/examples/beam.py
+++ b/docs/source/examples/beam.py
@@ -47,6 +47,8 @@ def __init__(self, N=4, **kwargs):
         theta_eq[0] = (th[0] >= th_base)  # base boundary condition
         displ_eq = (w >= w.left + 0.5*dx*(th + th.left))
         displ_eq[0] = (w[0] >= w_base)
+        for constraint in [shear_eq, moment_eq, theta_eq, displ_eq]:
+            constraint.update_varkeys()
         # minimize tip displacement (the last w)
         Model.__init__(self, w[-1],
                        [shear_eq, moment_eq, theta_eq, displ_eq,
diff --git a/gpkit/constraints/costed.py b/gpkit/constraints/costed.py
index 09f93a3e9..c4afc0afa 100644
--- a/gpkit/constraints/costed.py
+++ b/gpkit/constraints/costed.py
@@ -24,10 +24,9 @@ def subinplace(self, subs):
         self.cost = self.cost.sub(subs)
         ConstraintSet.subinplace(self, subs)
 
-    @property
-    def varkeys(self):
+    def update_varkeys(self):
         "return all Varkeys present in this ConstraintSet"
-        return ConstraintSet._varkeys(self, self.cost.varlocs)
+        ConstraintSet.update_varkeys(self, self.cost.varlocs)
 
     def rootconstr_str(self, excluded=None):
         "The appearance of a ConstraintSet in addition to its contents"
diff --git a/gpkit/constraints/linked.py b/gpkit/constraints/linked.py
index 340bc461e..31189919a 100644
--- a/gpkit/constraints/linked.py
+++ b/gpkit/constraints/linked.py
@@ -66,6 +66,10 @@ def __init__(self, constraints, include_only=None, exclude=None):
             self.reverselinks[newvk] = vks
         with SignomialsEnabled():  # since we're just substituting varkeys.
             self.subinplace(self.linked)
+        for constraint in self:
+            if hasattr(constraint, "update_varkeys"):
+                constraint.update_varkeys()
+        self.update_varkeys()
 
     def process_result(self, result):
         super(LinkedConstraintSet, self).process_result(result)
diff --git a/gpkit/constraints/model.py b/gpkit/constraints/model.py
index b8f7ff726..882c1258b 100644
--- a/gpkit/constraints/model.py
+++ b/gpkit/constraints/model.py
@@ -98,6 +98,7 @@ def _add_modelname_tovars(self, name, num):
                 del self.substitutions[vk]
         with SignomialsEnabled():  # since we're just substituting varkeys.
             self.subinplace(add_model_subs)
+        self.update_varkeys()
 
     def subconstr_str(self, excluded=None):
         "The collapsed appearance of a ConstraintBase"
diff --git a/gpkit/constraints/set.py b/gpkit/constraints/set.py
index 83d72cc88..49407d1ad 100644
--- a/gpkit/constraints/set.py
+++ b/gpkit/constraints/set.py
@@ -28,6 +28,7 @@ def __init__(self, constraints, substitutions=None, recursesubs=True):
             # grab the substitutions dict from the top constraintset
             subs.update(constraints.substitutions)  # pylint: disable=no-member
         if recursesubs:
+            self.update_varkeys()
             self.substitutions = KeyDict.with_keys(self.varkeys,
                                                    self._iter_subs(subs))
         else:
@@ -127,19 +128,14 @@ def subinplace(self, subs):
         for constraint in self:
             constraint.subinplace(subs)
 
-    @property
-    def varkeys(self):
-        "return all Varkeys present in this ConstraintSet"
-        return self._varkeys()
-
-    def _varkeys(self, init_dict=None):
-        "return all Varkeys present in this ConstraintSet"
-        init_dict = {} if init_dict is None else init_dict
-        out = KeySet(init_dict)
+    def update_varkeys(self, init_dict={}):
+        varkeys = KeySet(init_dict)
         for constraint in self:
             if hasattr(constraint, "varkeys"):
-                out.update(constraint.varkeys)
-        return out
+                varkeys.update(constraint.varkeys)
+            # else:
+            #     print type(constraint) # getting numpy bools...
+        self.varkeys = varkeys
 
     def as_posyslt1(self):
         "Returns list of posynomials which must be kept <= 1"

From 5158ec48112c7f7f3c3b3334f56c54f3f10cf725 Mon Sep 17 00:00:00 2001
From: Edward Burnell <eburn@mit.edu>
Date: Thu, 4 Aug 2016 07:14:58 -0700
Subject: [PATCH 02/12] make it easy to add varkeys

---
 gpkit/keydict.py | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/gpkit/keydict.py b/gpkit/keydict.py
index aba2fe594..41018fc46 100644
--- a/gpkit/keydict.py
+++ b/gpkit/keydict.py
@@ -42,6 +42,10 @@ def __init__(self, *args, **kwargs):
         self.keymap = defaultdict(set)
         self.update(*args, **kwargs)
 
+    def add(self, *args):
+        for arg in args:
+            self[arg] = None
+
     def update(self, *args, **kwargs):
         "Iterates through the dictionary created by args and kwargs"
         for k, v in dict(*args, **kwargs).items():

From 66c588b6e8dac575f475247ce6b150e7a076cc8b Mon Sep 17 00:00:00 2001
From: Edward Burnell <eburn@mit.edu>
Date: Thu, 4 Aug 2016 07:46:23 -0700
Subject: [PATCH 03/12] lint and rename

---
 docs/source/examples/beam.py        |  2 +-
 gpkit/constraints/costed.py         |  7 +++++--
 gpkit/constraints/linked.py         | 13 ++++++-------
 gpkit/constraints/model.py          |  2 +-
 gpkit/constraints/prog_factories.py |  9 +++++----
 gpkit/constraints/set.py            |  9 ++++++---
 gpkit/keydict.py                    |  9 +++++----
 7 files changed, 29 insertions(+), 22 deletions(-)

diff --git a/docs/source/examples/beam.py b/docs/source/examples/beam.py
index 7cd0212b5..2af7f670c 100644
--- a/docs/source/examples/beam.py
+++ b/docs/source/examples/beam.py
@@ -48,7 +48,7 @@ def __init__(self, N=4, **kwargs):
         displ_eq = (w >= w.left + 0.5*dx*(th + th.left))
         displ_eq[0] = (w[0] >= w_base)
         for constraint in [shear_eq, moment_eq, theta_eq, displ_eq]:
-            constraint.update_varkeys()
+            constraint.reset_varkeys()
         # minimize tip displacement (the last w)
         Model.__init__(self, w[-1],
                        [shear_eq, moment_eq, theta_eq, displ_eq,
diff --git a/gpkit/constraints/costed.py b/gpkit/constraints/costed.py
index c4afc0afa..2a7750aab 100644
--- a/gpkit/constraints/costed.py
+++ b/gpkit/constraints/costed.py
@@ -24,9 +24,12 @@ def subinplace(self, subs):
         self.cost = self.cost.sub(subs)
         ConstraintSet.subinplace(self, subs)
 
-    def update_varkeys(self):
+    def reset_varkeys(self, init_dict=None):
         "return all Varkeys present in this ConstraintSet"
-        ConstraintSet.update_varkeys(self, self.cost.varlocs)
+        costkeys = dict(self.cost.varlocs)
+        if init_dict is not None:
+            costkeys.update(init_dict)
+        ConstraintSet.reset_varkeys(self, costkeys)
 
     def rootconstr_str(self, excluded=None):
         "The appearance of a ConstraintSet in addition to its contents"
diff --git a/gpkit/constraints/linked.py b/gpkit/constraints/linked.py
index 31189919a..d9b1d9c29 100644
--- a/gpkit/constraints/linked.py
+++ b/gpkit/constraints/linked.py
@@ -27,11 +27,10 @@ class LinkedConstraintSet(ConstraintSet):
     """
     def __init__(self, constraints, include_only=None, exclude=None):
         ConstraintSet.__init__(self, constraints)
-        varkeys = self.varkeys
         linkable = set()
-        for varkey in varkeys:
+        for varkey in self.varkeys:
             name_without_model = varkey.str_without(["models"])
-            if len(varkeys[name_without_model]) > 1:
+            if len(self.varkeys[name_without_model]) > 1:
                 linkable.add(name_without_model)
         if include_only:
             linkable &= set(include_only)
@@ -39,7 +38,7 @@ def __init__(self, constraints, include_only=None, exclude=None):
             linkable -= set(exclude)
         self.linked, self.reverselinks = {}, {}
         for name in linkable:
-            vks = varkeys[name]
+            vks = self.varkeys[name]
             sub, subbed_vk = None, None
             for vk in vks:
                 if vk in self.substitutions:
@@ -67,9 +66,9 @@ def __init__(self, constraints, include_only=None, exclude=None):
         with SignomialsEnabled():  # since we're just substituting varkeys.
             self.subinplace(self.linked)
         for constraint in self:
-            if hasattr(constraint, "update_varkeys"):
-                constraint.update_varkeys()
-        self.update_varkeys()
+            if hasattr(constraint, "reset_varkeys"):
+                constraint.reset_varkeys()
+        self.reset_varkeys()
 
     def process_result(self, result):
         super(LinkedConstraintSet, self).process_result(result)
diff --git a/gpkit/constraints/model.py b/gpkit/constraints/model.py
index 882c1258b..2104ab90c 100644
--- a/gpkit/constraints/model.py
+++ b/gpkit/constraints/model.py
@@ -98,7 +98,7 @@ def _add_modelname_tovars(self, name, num):
                 del self.substitutions[vk]
         with SignomialsEnabled():  # since we're just substituting varkeys.
             self.subinplace(add_model_subs)
-        self.update_varkeys()
+        self.reset_varkeys()
 
     def subconstr_str(self, excluded=None):
         "The collapsed appearance of a ConstraintBase"
diff --git a/gpkit/constraints/prog_factories.py b/gpkit/constraints/prog_factories.py
index 01e89fc1c..2cc599af7 100644
--- a/gpkit/constraints/prog_factories.py
+++ b/gpkit/constraints/prog_factories.py
@@ -1,10 +1,6 @@
 "Scripts for generating, solving and sweeping programs"
 from time import time
 import numpy as np
-from ..nomials.substitution import parse_subs
-from ..solution_array import SolutionArray
-from ..keydict import KeyDict
-from ..varkey import VarKey
 
 try:
     from ipyparallel import Client
@@ -16,6 +12,11 @@
 except (ImportError, IOError, AssertionError):
     POOL = None
 
+from ..nomials.substitution import parse_subs
+from ..solution_array import SolutionArray
+from ..keydict import KeyDict
+from ..varkey import VarKey
+
 
 def _progify_fctry(program, return_attr=None):
     "Generates function that returns a program() and optionally an attribute."
diff --git a/gpkit/constraints/set.py b/gpkit/constraints/set.py
index 49407d1ad..22f9fe5a2 100644
--- a/gpkit/constraints/set.py
+++ b/gpkit/constraints/set.py
@@ -28,7 +28,7 @@ def __init__(self, constraints, substitutions=None, recursesubs=True):
             # grab the substitutions dict from the top constraintset
             subs.update(constraints.substitutions)  # pylint: disable=no-member
         if recursesubs:
-            self.update_varkeys()
+            self.reset_varkeys()
             self.substitutions = KeyDict.with_keys(self.varkeys,
                                                    self._iter_subs(subs))
         else:
@@ -128,8 +128,11 @@ def subinplace(self, subs):
         for constraint in self:
             constraint.subinplace(subs)
 
-    def update_varkeys(self, init_dict={}):
-        varkeys = KeySet(init_dict)
+    def reset_varkeys(self, init_dict=None):
+        "Goes through constraints and collects their varkeys."
+        varkeys = KeySet()
+        if not init_dict is None:
+            varkeys.update(init_dict)
         for constraint in self:
             if hasattr(constraint, "varkeys"):
                 varkeys.update(constraint.varkeys)
diff --git a/gpkit/keydict.py b/gpkit/keydict.py
index 41018fc46..e6245aa50 100644
--- a/gpkit/keydict.py
+++ b/gpkit/keydict.py
@@ -42,10 +42,6 @@ def __init__(self, *args, **kwargs):
         self.keymap = defaultdict(set)
         self.update(*args, **kwargs)
 
-    def add(self, *args):
-        for arg in args:
-            self[arg] = None
-
     def update(self, *args, **kwargs):
         "Iterates through the dictionary created by args and kwargs"
         for k, v in dict(*args, **kwargs).items():
@@ -153,6 +149,11 @@ class KeySet(KeyDict):
     "KeySets are KeyDicts without values, serving only to filter and map keys"
     collapse_arrays = False
 
+    def add(self, *args):
+        "Adds all args to the keyset"
+        for arg in args:
+            self[arg] = None
+
     def __getitem__(self, key):
         "Gets the keys corresponding to a particular key."
         key, _ = self.parse_and_index(key)

From 32410c4d758f71ec244558ae14d86d0549bc749e Mon Sep 17 00:00:00 2001
From: Edward Burnell <eburn@mit.edu>
Date: Thu, 4 Aug 2016 09:10:31 -0700
Subject: [PATCH 04/12] implement set syntax

---
 gpkit/keydict.py | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/gpkit/keydict.py b/gpkit/keydict.py
index e6245aa50..f45bbb695 100644
--- a/gpkit/keydict.py
+++ b/gpkit/keydict.py
@@ -149,10 +149,14 @@ class KeySet(KeyDict):
     "KeySets are KeyDicts without values, serving only to filter and map keys"
     collapse_arrays = False
 
-    def add(self, *args):
-        "Adds all args to the keyset"
-        for arg in args:
-            self[arg] = None
+    def add(self, item):
+        "Adds an item to the keyset"
+        self[item] = None
+
+    def union(self, iterable):
+        "Adds an iterable to the keyset"
+        for item in iterable:
+            self.add(item)
 
     def __getitem__(self, key):
         "Gets the keys corresponding to a particular key."

From 236dacbd4268c5917aab6646d77510ad6ae33aa1 Mon Sep 17 00:00:00 2001
From: Edward Burnell <eburn@mit.edu>
Date: Thu, 4 Aug 2016 09:15:09 -0700
Subject: [PATCH 05/12] response to code review (docstring and beam fix)

---
 docs/source/examples/beam.py         |  6 +++--
 docs/source/examples/beam_output.txt | 33 ----------------------------
 gpkit/constraints/costed.py          |  2 +-
 3 files changed, 5 insertions(+), 36 deletions(-)

diff --git a/docs/source/examples/beam.py b/docs/source/examples/beam.py
index 2af7f670c..0af28a7d8 100644
--- a/docs/source/examples/beam.py
+++ b/docs/source/examples/beam.py
@@ -40,15 +40,17 @@ def __init__(self, N=4, **kwargs):
         # shear and moment increase from tip to base (left > right)
         shear_eq = (V >= V.right + 0.5*dx*(q + q.right))
         shear_eq[-1] = (V[-1] >= V_tip)  # tip boundary condition
+        shear_eq.varkeys.add(V_tip)
         moment_eq = (M >= M.right + 0.5*dx*(V + V.right))
         moment_eq[-1] = (M[-1] >= M_tip)
+        moment_eq.varkeys.add(M_tip)
         # slope and displacement increase from base to tip (right > left)
         theta_eq = (th >= th.left + 0.5*dx*(M + M.left)/EI)
         theta_eq[0] = (th[0] >= th_base)  # base boundary condition
+        theta_eq.varkeys.add(th_base)
         displ_eq = (w >= w.left + 0.5*dx*(th + th.left))
         displ_eq[0] = (w[0] >= w_base)
-        for constraint in [shear_eq, moment_eq, theta_eq, displ_eq]:
-            constraint.reset_varkeys()
+        displ_eq.varkeys.add(w_base)
         # minimize tip displacement (the last w)
         Model.__init__(self, w[-1],
                        [shear_eq, moment_eq, theta_eq, displ_eq,
diff --git a/docs/source/examples/beam_output.txt b/docs/source/examples/beam_output.txt
index b49476155..e69de29bb 100644
--- a/docs/source/examples/beam_output.txt
+++ b/docs/source/examples/beam_output.txt
@@ -1,33 +0,0 @@
-
-Cost
-----
- 1.62 [m] 
-
-Free Variables
---------------
-          dx : 1.2                                             [m]   Length of an element
-     \vec{M} : [ 1.98e+03  1.27e+03  713       317      ... ]  [N*m] Internal moment     
-     \vec{V} : [ 660       528       396       264      ... ]  [N]   Internal shear      
-\vec{\theta} : [  -        0.177     0.285     0.341    ... ]        Slope               
-     \vec{w} : [  -        0.106     0.384     0.759    ... ]  [m]   Displacement        
-
-Constants
----------
-           EI : 1.1e+04                                         [N*m**2]                               
-            L : 6                                               [m]      Overall beam length           
-      M_{tip} : 0                                               [N*m]    Tip moment                    
-      V_{tip} : 0                                               [N]      Tip loading                   
-\theta_{base} : 0                                                        Base angle                    
-     w_{base} : 0                                               [m]      Base deflection               
-      \vec{M} : [  -         -         -         -       ... ]  [N*m]    Internal moment               
-      \vec{V} : [  -         -         -         -       ... ]  [N]      Internal shear                
- \vec{\theta} : [ 0          -         -         -       ... ]           Slope                         
-      \vec{q} : [ 110       110       110       110      ... ]  [N/m]    Distributed load at each point
-      \vec{w} : [ 0          -         -         -       ... ]  [m]      Displacement                  
-
-Sensitivities
--------------
-      L : 4                                              Overall beam length           
-\vec{q} : [ 0.0072    0.0416    0.118     0.234    ... ] Distributed load at each point
-     EI : -1                                                                           
-
diff --git a/gpkit/constraints/costed.py b/gpkit/constraints/costed.py
index 2a7750aab..43fb114d6 100644
--- a/gpkit/constraints/costed.py
+++ b/gpkit/constraints/costed.py
@@ -25,7 +25,7 @@ def subinplace(self, subs):
         ConstraintSet.subinplace(self, subs)
 
     def reset_varkeys(self, init_dict=None):
-        "return all Varkeys present in this ConstraintSet"
+        "Resets varkeys to what is in the cost and constraints"
         costkeys = dict(self.cost.varlocs)
         if init_dict is not None:
             costkeys.update(init_dict)

From f5994530722bb29ce95b454afbb9c3a94c1b83b3 Mon Sep 17 00:00:00 2001
From: Edward Burnell <eburn@mit.edu>
Date: Thu, 4 Aug 2016 12:59:58 -0700
Subject: [PATCH 06/12] fix named unused variables

---
 gpkit/constraints/costed.py | 13 ++++++++++---
 gpkit/constraints/set.py    |  4 ++--
 2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/gpkit/constraints/costed.py b/gpkit/constraints/costed.py
index 43fb114d6..517dc062b 100644
--- a/gpkit/constraints/costed.py
+++ b/gpkit/constraints/costed.py
@@ -22,14 +22,21 @@ def __init__(self, cost, constraints, substitutions=None):
     def subinplace(self, subs):
         "Substitutes in place."
         self.cost = self.cost.sub(subs)
+        if hasattr(self, "unused_variables"):
+            unused_vars = []
+            for var in self.unused_variables:
+                if var.key in subs:
+                    unused_vars.append(subs[var.key])
+                else:
+                    unused_vars.append(var.key)
+            self.unused_variables = unused_vars
         ConstraintSet.subinplace(self, subs)
 
     def reset_varkeys(self, init_dict=None):
         "Resets varkeys to what is in the cost and constraints"
-        costkeys = dict(self.cost.varlocs)
+        ConstraintSet.reset_varkeys(self, self.cost.varlocs)
         if init_dict is not None:
-            costkeys.update(init_dict)
-        ConstraintSet.reset_varkeys(self, costkeys)
+            self.varkeys.union(init_dict)
 
     def rootconstr_str(self, excluded=None):
         "The appearance of a ConstraintSet in addition to its contents"
diff --git a/gpkit/constraints/set.py b/gpkit/constraints/set.py
index 22f9fe5a2..3aca6b51a 100644
--- a/gpkit/constraints/set.py
+++ b/gpkit/constraints/set.py
@@ -136,8 +136,8 @@ def reset_varkeys(self, init_dict=None):
         for constraint in self:
             if hasattr(constraint, "varkeys"):
                 varkeys.update(constraint.varkeys)
-            # else:
-            #     print type(constraint) # getting numpy bools...
+        if hasattr(self, "unused_variables"):
+            varkeys.union(self.unused_variables)
         self.varkeys = varkeys
 
     def as_posyslt1(self):

From 76dd54f0c3f1f83a638d8df22a2a24c2c09186bc Mon Sep 17 00:00:00 2001
From: Edward Burnell <eburn@mit.edu>
Date: Thu, 4 Aug 2016 13:26:31 -0700
Subject: [PATCH 07/12] reset varkeys on setitem

---
 docs/source/examples/beam.py         |  4 ----
 docs/source/examples/beam_output.txt | 33 ++++++++++++++++++++++++++++
 gpkit/constraints/set.py             |  4 ++++
 3 files changed, 37 insertions(+), 4 deletions(-)

diff --git a/docs/source/examples/beam.py b/docs/source/examples/beam.py
index 0af28a7d8..522b2175e 100644
--- a/docs/source/examples/beam.py
+++ b/docs/source/examples/beam.py
@@ -40,17 +40,13 @@ def __init__(self, N=4, **kwargs):
         # shear and moment increase from tip to base (left > right)
         shear_eq = (V >= V.right + 0.5*dx*(q + q.right))
         shear_eq[-1] = (V[-1] >= V_tip)  # tip boundary condition
-        shear_eq.varkeys.add(V_tip)
         moment_eq = (M >= M.right + 0.5*dx*(V + V.right))
         moment_eq[-1] = (M[-1] >= M_tip)
-        moment_eq.varkeys.add(M_tip)
         # slope and displacement increase from base to tip (right > left)
         theta_eq = (th >= th.left + 0.5*dx*(M + M.left)/EI)
         theta_eq[0] = (th[0] >= th_base)  # base boundary condition
-        theta_eq.varkeys.add(th_base)
         displ_eq = (w >= w.left + 0.5*dx*(th + th.left))
         displ_eq[0] = (w[0] >= w_base)
-        displ_eq.varkeys.add(w_base)
         # minimize tip displacement (the last w)
         Model.__init__(self, w[-1],
                        [shear_eq, moment_eq, theta_eq, displ_eq,
diff --git a/docs/source/examples/beam_output.txt b/docs/source/examples/beam_output.txt
index e69de29bb..b49476155 100644
--- a/docs/source/examples/beam_output.txt
+++ b/docs/source/examples/beam_output.txt
@@ -0,0 +1,33 @@
+
+Cost
+----
+ 1.62 [m] 
+
+Free Variables
+--------------
+          dx : 1.2                                             [m]   Length of an element
+     \vec{M} : [ 1.98e+03  1.27e+03  713       317      ... ]  [N*m] Internal moment     
+     \vec{V} : [ 660       528       396       264      ... ]  [N]   Internal shear      
+\vec{\theta} : [  -        0.177     0.285     0.341    ... ]        Slope               
+     \vec{w} : [  -        0.106     0.384     0.759    ... ]  [m]   Displacement        
+
+Constants
+---------
+           EI : 1.1e+04                                         [N*m**2]                               
+            L : 6                                               [m]      Overall beam length           
+      M_{tip} : 0                                               [N*m]    Tip moment                    
+      V_{tip} : 0                                               [N]      Tip loading                   
+\theta_{base} : 0                                                        Base angle                    
+     w_{base} : 0                                               [m]      Base deflection               
+      \vec{M} : [  -         -         -         -       ... ]  [N*m]    Internal moment               
+      \vec{V} : [  -         -         -         -       ... ]  [N]      Internal shear                
+ \vec{\theta} : [ 0          -         -         -       ... ]           Slope                         
+      \vec{q} : [ 110       110       110       110      ... ]  [N/m]    Distributed load at each point
+      \vec{w} : [ 0          -         -         -       ... ]  [m]      Displacement                  
+
+Sensitivities
+-------------
+      L : 4                                              Overall beam length           
+\vec{q} : [ 0.0072    0.0416    0.118     0.234    ... ] Distributed load at each point
+     EI : -1                                                                           
+
diff --git a/gpkit/constraints/set.py b/gpkit/constraints/set.py
index 3aca6b51a..8ea581103 100644
--- a/gpkit/constraints/set.py
+++ b/gpkit/constraints/set.py
@@ -48,6 +48,10 @@ def __getitem__(self, key):
                 variables.sort(key=_var_sort_key)
                 return variables
 
+    def __setitem__(self, key, value):
+        list.__setitem__(self, key, value)
+        self.reset_varkeys()
+
     __str__ = _str
     __repr__ = _repr
     _repr_latex_ = _repr_latex_

From 750edcb3f316a6497ea015330a6e00b3553abb9d Mon Sep 17 00:00:00 2001
From: Edward Burnell <eburn@mit.edu>
Date: Fri, 5 Aug 2016 10:48:25 -0700
Subject: [PATCH 08/12] union -> update, lint in response to code review

---
 gpkit/constraints/costed.py |  2 +-
 gpkit/constraints/set.py    |  4 ++--
 gpkit/keydict.py            | 12 ++++++++----
 3 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/gpkit/constraints/costed.py b/gpkit/constraints/costed.py
index 517dc062b..b12524ed7 100644
--- a/gpkit/constraints/costed.py
+++ b/gpkit/constraints/costed.py
@@ -36,7 +36,7 @@ def reset_varkeys(self, init_dict=None):
         "Resets varkeys to what is in the cost and constraints"
         ConstraintSet.reset_varkeys(self, self.cost.varlocs)
         if init_dict is not None:
-            self.varkeys.union(init_dict)
+            self.varkeys.update(init_dict)
 
     def rootconstr_str(self, excluded=None):
         "The appearance of a ConstraintSet in addition to its contents"
diff --git a/gpkit/constraints/set.py b/gpkit/constraints/set.py
index 8ea581103..d54305c02 100644
--- a/gpkit/constraints/set.py
+++ b/gpkit/constraints/set.py
@@ -135,13 +135,13 @@ def subinplace(self, subs):
     def reset_varkeys(self, init_dict=None):
         "Goes through constraints and collects their varkeys."
         varkeys = KeySet()
-        if not init_dict is None:
+        if init_dict is not None:
             varkeys.update(init_dict)
         for constraint in self:
             if hasattr(constraint, "varkeys"):
                 varkeys.update(constraint.varkeys)
         if hasattr(self, "unused_variables"):
-            varkeys.union(self.unused_variables)
+            varkeys.update(self.unused_variables)
         self.varkeys = varkeys
 
     def as_posyslt1(self):
diff --git a/gpkit/keydict.py b/gpkit/keydict.py
index f45bbb695..d39af3c1c 100644
--- a/gpkit/keydict.py
+++ b/gpkit/keydict.py
@@ -153,10 +153,14 @@ def add(self, item):
         "Adds an item to the keyset"
         self[item] = None
 
-    def union(self, iterable):
-        "Adds an iterable to the keyset"
-        for item in iterable:
-            self.add(item)
+    def update(self, *args, **kwargs):
+        "Iterates through the dictionary created by args and kwargs"
+        if len(args) == 1:
+            for item in args[0]:
+                self.add(item)
+        else:
+            for k, v in dict(*args, **kwargs).items():
+                self[k] = v
 
     def __getitem__(self, key):
         "Gets the keys corresponding to a particular key."

From 455e0b5368d6a2e7e9364f1e49373d7c09a0cab2 Mon Sep 17 00:00:00 2001
From: Edward Burnell <eburn@mit.edu>
Date: Fri, 5 Aug 2016 11:06:31 -0700
Subject: [PATCH 09/12] move unused_variables sub to a better location

---
 gpkit/constraints/costed.py | 8 --------
 gpkit/constraints/set.py    | 8 ++++++++
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/gpkit/constraints/costed.py b/gpkit/constraints/costed.py
index b12524ed7..70901a97f 100644
--- a/gpkit/constraints/costed.py
+++ b/gpkit/constraints/costed.py
@@ -22,14 +22,6 @@ def __init__(self, cost, constraints, substitutions=None):
     def subinplace(self, subs):
         "Substitutes in place."
         self.cost = self.cost.sub(subs)
-        if hasattr(self, "unused_variables"):
-            unused_vars = []
-            for var in self.unused_variables:
-                if var.key in subs:
-                    unused_vars.append(subs[var.key])
-                else:
-                    unused_vars.append(var.key)
-            self.unused_variables = unused_vars
         ConstraintSet.subinplace(self, subs)
 
     def reset_varkeys(self, init_dict=None):
diff --git a/gpkit/constraints/set.py b/gpkit/constraints/set.py
index d54305c02..2f6141e17 100644
--- a/gpkit/constraints/set.py
+++ b/gpkit/constraints/set.py
@@ -131,6 +131,14 @@ def subinplace(self, subs):
         "Substitutes in place."
         for constraint in self:
             constraint.subinplace(subs)
+        if hasattr(self, "unused_variables"):
+            unused_vars = []
+            for var in self.unused_variables:
+                if var.key in subs:
+                    unused_vars.append(subs[var.key])
+                else:
+                    unused_vars.append(var.key)
+            self.unused_variables = unused_vars
 
     def reset_varkeys(self, init_dict=None):
         "Goes through constraints and collects their varkeys."

From 7ea4b0f5910fdd877860ff0876617311d93ceacb Mon Sep 17 00:00:00 2001
From: Edward Burnell <eburn@mit.edu>
Date: Sat, 6 Aug 2016 02:15:10 -0700
Subject: [PATCH 10/12] recursively reset on subinplace

---
 gpkit/constraints/model.py | 1 -
 gpkit/constraints/set.py   | 1 +
 2 files changed, 1 insertion(+), 1 deletion(-)

diff --git a/gpkit/constraints/model.py b/gpkit/constraints/model.py
index 2104ab90c..b8f7ff726 100644
--- a/gpkit/constraints/model.py
+++ b/gpkit/constraints/model.py
@@ -98,7 +98,6 @@ def _add_modelname_tovars(self, name, num):
                 del self.substitutions[vk]
         with SignomialsEnabled():  # since we're just substituting varkeys.
             self.subinplace(add_model_subs)
-        self.reset_varkeys()
 
     def subconstr_str(self, excluded=None):
         "The collapsed appearance of a ConstraintBase"
diff --git a/gpkit/constraints/set.py b/gpkit/constraints/set.py
index 2f6141e17..4ec19d973 100644
--- a/gpkit/constraints/set.py
+++ b/gpkit/constraints/set.py
@@ -139,6 +139,7 @@ def subinplace(self, subs):
                 else:
                     unused_vars.append(var.key)
             self.unused_variables = unused_vars
+        self.reset_varkeys()
 
     def reset_varkeys(self, init_dict=None):
         "Goes through constraints and collects their varkeys."

From 30ff1bada95b8fe19e9b4274be8350f13332cfb6 Mon Sep 17 00:00:00 2001
From: Warren Hoburg <whoburg@mit.edu>
Date: Fri, 5 Aug 2016 16:36:29 -0400
Subject: [PATCH 11/12] add test for lack of modelname appending

---
 gpkit/tests/t_model.py | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/gpkit/tests/t_model.py b/gpkit/tests/t_model.py
index d44161c97..3c5b51fa3 100644
--- a/gpkit/tests/t_model.py
+++ b/gpkit/tests/t_model.py
@@ -418,7 +418,24 @@ def test_cvxopt_kwargs(self):
         self.assertAlmostEqual(sol["cost"], 12., NDIGS["cvxopt"])
 
 
-TESTS = [TestModelSolverSpecific]
+class Thing(Model):
+    "a thing, for model testing"
+    def __init__(self, n, **kwargs):
+        a = VectorVariable(n, "a", "g/m")
+        b = VectorVariable(n, "b", "m")
+        c = Variable("c", 17/4., "g")
+        Model.__init__(self, None, [a >= c/b], **kwargs)
+
+
+class TestModelNoSolve(unittest.TestCase):
+    """model tests that don't require a solver"""
+    def test_modelname_added(self):
+        t = Thing(2)
+        for vk in t.varkeys:
+            self.assertEqual(vk.models, ["Thing"])
+
+
+TESTS = [TestModelSolverSpecific, TestModelNoSolve]
 MULTI_SOLVER_TESTS = [TestGP, TestSP]
 
 for testcase in MULTI_SOLVER_TESTS:

From 9a7122d38129f756e1614d540e8b20428dca01a1 Mon Sep 17 00:00:00 2001
From: Warren Hoburg <whoburg@mit.edu>
Date: Sat, 6 Aug 2016 08:41:38 -0400
Subject: [PATCH 12/12] pylint attr accessed before def / defined outside init

---
 gpkit/constraints/set.py | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/gpkit/constraints/set.py b/gpkit/constraints/set.py
index 4ec19d973..33de27811 100644
--- a/gpkit/constraints/set.py
+++ b/gpkit/constraints/set.py
@@ -18,6 +18,7 @@ def __init__(self, constraints, substitutions=None, recursesubs=True):
             constraints = [constraints]
         list.__init__(self, constraints)
         subs = substitutions if substitutions else {}
+        self.unused_variables = None
         if not isinstance(constraints, ConstraintSet):
             # constraintsetify everything
             for i, constraint in enumerate(self):
@@ -131,7 +132,7 @@ def subinplace(self, subs):
         "Substitutes in place."
         for constraint in self:
             constraint.subinplace(subs)
-        if hasattr(self, "unused_variables"):
+        if self.unused_variables is not None:
             unused_vars = []
             for var in self.unused_variables:
                 if var.key in subs:
@@ -149,7 +150,7 @@ def reset_varkeys(self, init_dict=None):
         for constraint in self:
             if hasattr(constraint, "varkeys"):
                 varkeys.update(constraint.varkeys)
-        if hasattr(self, "unused_variables"):
+        if self.unused_variables is not None:
             varkeys.update(self.unused_variables)
         self.varkeys = varkeys