From f66365ccc514e4aa0c2292bc5dcdeaf6d213fba6 Mon Sep 17 00:00:00 2001
From: Cliff Hansen <cwhanse@sandia.gov>
Date: Mon, 16 Nov 2020 16:17:15 -0700
Subject: [PATCH 01/13] add atol, add tests

---
 pvlib/tests/test_tools.py | 25 +++++++++++++++++++++
 pvlib/tools.py            | 46 ++++++++++++++++++++++++---------------
 2 files changed, 53 insertions(+), 18 deletions(-)

diff --git a/pvlib/tests/test_tools.py b/pvlib/tests/test_tools.py
index 42eaedca58..1735b1bc9d 100644
--- a/pvlib/tests/test_tools.py
+++ b/pvlib/tests/test_tools.py
@@ -1,6 +1,7 @@
 import pytest
 
 from pvlib import tools
+import numpy as np
 
 
 @pytest.mark.parametrize('keys, input_dict, expected', [
@@ -12,3 +13,27 @@
 def test_build_kwargs(keys, input_dict, expected):
     kwargs = tools._build_kwargs(keys, input_dict)
     assert kwargs == expected
+
+
+def _obj_test_golden_sect(params, loc):
+    return params[loc] * (1. - params['c'] * params[loc]**params['n'])
+
+                               
+def test__golden_sect_DataFrame(params, lb, ub, expected, func):
+    v, x = tools._golden_sect_DataFrame(params, lb, ub, func)    
+    assert np.isclose(x, expected, atol=1e-8)
+
+
+def test__golden_sect_DataFrame_atol():
+    params = {'c': 0.2, 'n': 0.3}
+    expected = 89.14332727531685
+    v, x = tools._golden_sect_DataFrame(params, 0., 100., _obj_test_golden_sect,
+                                  atol=1e-12)
+    assert np.isclose(x, expected, atol=1e-12)
+
+
+def test__golden_sect_DataFrame_vector():
+    params = {'c': np.array([1., 2.]), 'n': np.array([1., 1.])}
+    expected = np.array([0.5, 0.25])
+    v, x = tools._golden_sect_DataFrame(params, 0., 1., _obj_test_golden_sect)
+    assert np.allclose(x, expected, atol=1e-8)
diff --git a/pvlib/tools.py b/pvlib/tools.py
index b6ee3e7c3a..02b347884d 100644
--- a/pvlib/tools.py
+++ b/pvlib/tools.py
@@ -249,36 +249,38 @@ def _build_kwargs(keys, input_dict):
     return kwargs
 
 
-# Created April,2014
-# Author: Rob Andrews, Calama Consulting
-
-def _golden_sect_DataFrame(params, VL, VH, func):
+# Created April,2014 by Rob Andrews, Calama Consulting
+# Modified: November, 2020 by C. W. Hansen, to add atol and change exit
+# criteria
+def _golden_sect_DataFrame(params, VL, VH, func, atol=1e-8):
     """
     Vectorized golden section search for finding MPP from a dataframe
     timeseries.
 
     Parameters
     ----------
-    params : dict
-        Dictionary containing scalars or arrays
+    params : dict or Dataframe
+        Parameters for the IV curve(s) where MPP will be found. Must contain
+        keys: 'r_sh', 'r_s', 'nNsVth', 'i_0', 'i_l'
         of inputs to the function to be optimized.
         Each row should represent an independent optimization.
 
     VL: float
-        Lower bound of the optimization
+        Lower bound on voltage for the optimization
 
-    VH: float
-        Upper bound of the optimization
+    VH: array-like
+        Upper bound on voltage for the optimization
 
     func: function
-        Function to be optimized must be in the form f(array-like, x)
+        Function to be optimized must be in the form f(dict or Dataframe, str)
+        where str is the key corresponding to voltage 
 
     Returns
     -------
-    func(df,'V1') : DataFrame
+    func(params, 'V1') : dict or DataFrame
         function evaluated at the optimal point
 
-    df['V1']: Dataframe
+    df['V1']: array-like or Series
         Dataframe of optimal points
 
     Notes
@@ -286,16 +288,19 @@ def _golden_sect_DataFrame(params, VL, VH, func):
     This function will find the MAXIMUM of a function
     """
 
+    phim1 = (np.sqrt(5) - 1) / 2
+
     df = params
     df['VH'] = VH
     df['VL'] = VL
 
     errflag = True
     iterations = 0
+    iterlimit = np.max(np.trunc(np.log(atol / (VH - VL)) / np.log(phim1))) + 1
 
     while errflag:
 
-        phi = (np.sqrt(5)-1)/2*(df['VH']-df['VL'])
+        phi = phim1 * (df['VH'] - df['VL'])
         df['V1'] = df['VL'] + phi
         df['V2'] = df['VH'] - phi
 
@@ -306,15 +311,20 @@ def _golden_sect_DataFrame(params, VL, VH, func):
         df['VL'] = df['V2']*df['SW_Flag'] + df['VL']*(~df['SW_Flag'])
         df['VH'] = df['V1']*~df['SW_Flag'] + df['VH']*(df['SW_Flag'])
 
-        err = df['V1'] - df['V2']
+        err = abs(df['V2'] - df['V1'])
         try:
-            errflag = (abs(err) > .01).any()
+            errflag = (err > atol).any()
         except ValueError:
-            errflag = (abs(err) > .01)
+            errflag = err > atol
 
         iterations += 1
 
-        if iterations > 50:
-            raise Exception("EXCEPTION:iterations exceeded maximum (50)")
+        try:
+            iterflag = (iterations > iterlimit).any()
+        except ValueError:
+            iterflag = iterations > iterlimit
+
+        if iterflag and errflag:
+            raise Exception("EXCEPTION: iteration limit exceeded")
 
     return func(df, 'V1'), df['V1']

From eb88eb80ab7eba870f308afb25ba7397ec80cd53 Mon Sep 17 00:00:00 2001
From: Cliff Hansen <cwhanse@sandia.gov>
Date: Tue, 17 Nov 2020 08:25:11 -0700
Subject: [PATCH 02/13] add parametrize

---
 pvlib/tests/test_tools.py | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/pvlib/tests/test_tools.py b/pvlib/tests/test_tools.py
index 1735b1bc9d..1013c89f12 100644
--- a/pvlib/tests/test_tools.py
+++ b/pvlib/tests/test_tools.py
@@ -18,17 +18,22 @@ def test_build_kwargs(keys, input_dict, expected):
 def _obj_test_golden_sect(params, loc):
     return params[loc] * (1. - params['c'] * params[loc]**params['n'])
 
-                               
+
+@pytest.mark.parametrize('params, lb, ub, expected, func', [
+    ({'c': 1., 'n': 1.}, 0., 1., 0.5, _obj_test_golden_sect),
+    ({'c': 1e6, 'n': 6.}, 0., 1., 0.07230200263994839, _obj_test_golden_sect),
+    ({'c': 0.2, 'n': 0.3}, 0., 100., 89.14332727531685, _obj_test_golden_sect)
+])
 def test__golden_sect_DataFrame(params, lb, ub, expected, func):
-    v, x = tools._golden_sect_DataFrame(params, lb, ub, func)    
+    v, x = tools._golden_sect_DataFrame(params, lb, ub, func)
     assert np.isclose(x, expected, atol=1e-8)
 
 
 def test__golden_sect_DataFrame_atol():
     params = {'c': 0.2, 'n': 0.3}
     expected = 89.14332727531685
-    v, x = tools._golden_sect_DataFrame(params, 0., 100., _obj_test_golden_sect,
-                                  atol=1e-12)
+    v, x = tools._golden_sect_DataFrame(
+        params, 0., 100., _obj_test_golden_sect, atol=1e-12)
     assert np.isclose(x, expected, atol=1e-12)
 
 

From 6b123abc8dad10ecf2da818aaa051db259e7814b Mon Sep 17 00:00:00 2001
From: Cliff Hansen <cwhanse@sandia.gov>
Date: Tue, 17 Nov 2020 09:02:13 -0700
Subject: [PATCH 03/13] stickler

---
 pvlib/tools.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pvlib/tools.py b/pvlib/tools.py
index 02b347884d..2b7342d5fc 100644
--- a/pvlib/tools.py
+++ b/pvlib/tools.py
@@ -273,7 +273,7 @@ def _golden_sect_DataFrame(params, VL, VH, func, atol=1e-8):
 
     func: function
         Function to be optimized must be in the form f(dict or Dataframe, str)
-        where str is the key corresponding to voltage 
+        where str is the key corresponding to voltage
 
     Returns
     -------

From 6667d1726c68cc47091a3928d916c6ac9a902632 Mon Sep 17 00:00:00 2001
From: Cliff Hansen <cwhanse@sandia.gov>
Date: Tue, 18 Jan 2022 18:59:39 -0700
Subject: [PATCH 04/13] re-add atol

---
 pvlib/tools.py | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/pvlib/tools.py b/pvlib/tools.py
index 66ec8e9369..9b5f07a31b 100644
--- a/pvlib/tools.py
+++ b/pvlib/tools.py
@@ -277,8 +277,9 @@ def _build_args(keys, input_dict, dict_name):
 
 # Created April,2014
 # Author: Rob Andrews, Calama Consulting
-
-def _golden_sect_DataFrame(params, VL, VH, func):
+# Modified: November, 2020 by C. W. Hansen, to add atol and change exit
+# criteria
+def _golden_sect_DataFrame(params, VL, VH, func, atol=1e-8):
     """
     Vectorized golden section search for finding MPP from a dataframe
     timeseries.

From 79502f1373946c2021d761fc5daba82daa2b45aa Mon Sep 17 00:00:00 2001
From: Cliff Hansen <cwhanse@sandia.gov>
Date: Wed, 19 Jan 2022 13:47:48 -0700
Subject: [PATCH 05/13] remake pvsystem.singlediode tests with more precision

---
 pvlib/tests/test_pvsystem.py | 91 +++++++++++++++++++-----------------
 1 file changed, 48 insertions(+), 43 deletions(-)

diff --git a/pvlib/tests/test_pvsystem.py b/pvlib/tests/test_pvsystem.py
index 505016a7ce..1141e490e9 100644
--- a/pvlib/tests/test_pvsystem.py
+++ b/pvlib/tests/test_pvsystem.py
@@ -1313,32 +1313,35 @@ def test_singlediode_array():
                               resistance_series, resistance_shunt, nNsVth,
                               method='lambertw')
 
-    expected = np.array([
-        0.        ,  0.54538398,  1.43273966,  2.36328163,  3.29255606,
-        4.23101358,  5.16177031,  6.09368251,  7.02197553,  7.96846051,
-        8.88220557])
-
-    assert_allclose(sd['i_mp'], expected, atol=0.01)
+    expected_i = np.array([
+        0., 0.54614798740338, 1.435026463529, 2.3621366610078, 3.2953968319952,
+        4.2303869378787, 5.1655276691892, 6.1000269648604, 7.0333996177802,
+        7.9653036915959, 8.8954716265647])
+    expected_v = np.array([
+        0., 7.0966259059555, 7.9961986643428, 8.2222496810656, 8.3255927555753,
+        8.3766915453915, 8.3988872440242, 8.4027948807891, 8.3941399580559,
+        8.3763655188855, 8.3517057522791])
+
+    assert_allclose(sd['i_mp'], expected_i, atol=1e-8)
+    assert_allclose(sd['v_mp'], expected_v, atol=1e-8)
 
     sd = pvsystem.singlediode(photocurrent, saturation_current,
                               resistance_series, resistance_shunt, nNsVth)
-
     expected = pvsystem.i_from_v(resistance_shunt, resistance_series, nNsVth,
                                  sd['v_mp'], saturation_current, photocurrent,
                                  method='lambertw')
-
-    assert_allclose(sd['i_mp'], expected, atol=0.01)
+    assert_allclose(sd['i_mp'], expected, atol=1e-8)
 
 
 def test_singlediode_floats():
-    out = pvsystem.singlediode(7, 6e-7, .1, 20, .5, method='lambertw')
-    expected = {'i_xx': 4.2498,
-                'i_mp': 6.1275,
-                'v_oc': 8.1063,
-                'p_mp': 38.1937,
-                'i_x': 6.7558,
-                'i_sc': 6.9651,
-                'v_mp': 6.2331,
+    out = pvsystem.singlediode(7., 6.e-7, .1, 20., .5, method='lambertw')
+    expected = {'i_xx': 4.264060478,
+                'i_mp': 6.136267360,
+                'v_oc': 8.106300147,
+                'p_mp': 38.19421055,
+                'i_x': 6.7558815684,
+                'i_sc': 6.965172322,
+                'v_mp': 6.224339375,
                 'i': None,
                 'v': None}
     assert isinstance(out, dict)
@@ -1346,23 +1349,26 @@ def test_singlediode_floats():
         if k in ['i', 'v']:
             assert v is None
         else:
-            assert_allclose(v, expected[k], atol=1e-3)
+            assert_allclose(v, expected[k], atol=1e-6)
 
 
 def test_singlediode_floats_ivcurve():
-    out = pvsystem.singlediode(7, 6e-7, .1, 20, .5, ivcurve_pnts=3, method='lambertw')
-    expected = {'i_xx': 4.2498,
-                'i_mp': 6.1275,
-                'v_oc': 8.1063,
-                'p_mp': 38.1937,
-                'i_x': 6.7558,
-                'i_sc': 6.9651,
-                'v_mp': 6.2331,
-                'i': np.array([6.965172e+00, 6.755882e+00, 2.575717e-14]),
-                'v': np.array([0., 4.05315, 8.1063])}
+    out = pvsystem.singlediode(7., 6e-7, .1, 20., .5, ivcurve_pnts=3,
+                               method='lambertw')
+    expected = {'i_xx': 4.264060478,
+                'i_mp': 6.136267360,
+                'v_oc': 8.106300147,
+                'p_mp': 38.19421055,
+                'i_x': 6.7558815684,
+                'i_sc': 6.965172322,
+                'v_mp': 6.224339375,
+                'i': np.array([
+                    6.965172322, 6.755881568, 2.664535259e-14]),
+                'v': np.array([
+                    0., 4.053150073, 8.106300147])}
     assert isinstance(out, dict)
     for k, v in out.items():
-        assert_allclose(v, expected[k], atol=1e-3)
+        assert_allclose(v, expected[k], atol=1e-6)
 
 
 def test_singlediode_series_ivcurve(cec_module_params):
@@ -1383,21 +1389,20 @@ def test_singlediode_series_ivcurve(cec_module_params):
     out = pvsystem.singlediode(IL, I0, Rs, Rsh, nNsVth, ivcurve_pnts=3,
                                method='lambertw')
 
-    expected = OrderedDict([('i_sc', array([0., 3.01054475, 6.00675648])),
-                            ('v_oc', array([0., 9.96886962, 10.29530483])),
-                            ('i_mp', array([0., 2.65191983, 5.28594672])),
-                            ('v_mp', array([0., 8.33392491, 8.4159707])),
-                            ('p_mp', array([0., 22.10090078, 44.48637274])),
-                            ('i_x', array([0., 2.88414114, 5.74622046])),
-                            ('i_xx', array([0., 2.04340914, 3.90007956])),
+    expected = OrderedDict([('i_sc', array([0., 3.01079860, 6.00726296])),
+                            ('v_oc', array([0., 9.96959733, 10.29603253])),
+                            ('i_mp', array([0., 2.656285960, 5.290525645])),
+                            ('v_mp', array([0., 8.321092255, 8.409413795])),
+                            ('p_mp', array([0., 22.10320053, 44.49021934])),
+                            ('i_x', array([0., 2.884132006, 5.746202281])),
+                            ('i_xx', array([0., 2.052691562, 3.909673879])),
                             ('v', array([[0., 0., 0.],
-                                         [0., 4.98443481, 9.96886962],
-                                         [0., 5.14765242, 10.29530483]])),
+                                         [0., 4.984798663, 9.969597327],
+                                         [0., 5.148016266, 10.29603253]])),
                             ('i', array([[0., 0., 0.],
-                                         [3.01079860e+00, 2.88414114e+00,
-                                          3.10862447e-14],
-                                         [6.00726296e+00, 5.74622046e+00,
-                                          0.00000000e+00]]))])
+                                         [3.0107985972, 2.8841320056, 0.],
+                                         [6.0072629615, 5.7462022810, 0.]]))])
+
 
     for k, v in out.items():
         assert_allclose(v, expected[k], atol=1e-2)
@@ -1414,7 +1419,7 @@ def test_singlediode_series_ivcurve(cec_module_params):
                                          method='lambertw').T
 
     for k, v in out.items():
-        assert_allclose(v, expected[k], atol=1e-2)
+        assert_allclose(v, expected[k], atol=1e-6)
 
 
 def test_scale_voltage_current_power():

From f78b3e92cc3bfe389679bbe6025596352cb786f6 Mon Sep 17 00:00:00 2001
From: Cliff Hansen <cwhanse@sandia.gov>
Date: Wed, 19 Jan 2022 14:31:26 -0700
Subject: [PATCH 06/13] remove unneeded try, improve coverage

---
 pvlib/tests/test_tools.py |  4 ++++
 pvlib/tools.py            | 16 ++++------------
 2 files changed, 8 insertions(+), 12 deletions(-)

diff --git a/pvlib/tests/test_tools.py b/pvlib/tests/test_tools.py
index 1013c89f12..0a899e4c78 100644
--- a/pvlib/tests/test_tools.py
+++ b/pvlib/tests/test_tools.py
@@ -42,3 +42,7 @@ def test__golden_sect_DataFrame_vector():
     expected = np.array([0.5, 0.25])
     v, x = tools._golden_sect_DataFrame(params, 0., 1., _obj_test_golden_sect)
     assert np.allclose(x, expected, atol=1e-8)
+
+
+params, lb, ub, expected, func = ({'c': 1., 'n': 1.}, 0., 1., 0.5, _obj_test_golden_sect)
+test__golden_sect_DataFrame(params, lb, ub, expected, func)
diff --git a/pvlib/tools.py b/pvlib/tools.py
index 9b5f07a31b..2200f57b82 100644
--- a/pvlib/tools.py
+++ b/pvlib/tools.py
@@ -325,7 +325,7 @@ def _golden_sect_DataFrame(params, VL, VH, func, atol=1e-8):
     iterations = 0
     iterlimit = np.max(np.trunc(np.log(atol / (VH - VL)) / np.log(phim1))) + 1
 
-    while errflag:
+    while errflag and (iterations < iterlimit):
 
         phi = phim1 * (df['VH'] - df['VL'])
         df['V1'] = df['VL'] + phi
@@ -339,19 +339,11 @@ def _golden_sect_DataFrame(params, VL, VH, func, atol=1e-8):
         df['VH'] = df['V1']*~df['SW_Flag'] + df['VH']*(df['SW_Flag'])
 
         err = abs(df['V2'] - df['V1'])
-        try:
-            errflag = (err > atol).any()
-        except ValueError:
-            errflag = err > atol
+        errflag = (err > atol).any()  # works because err is np.float64
 
         iterations += 1
 
-        try:
-            iterflag = (iterations > iterlimit).any()
-        except ValueError:
-            iterflag = iterations > iterlimit
-
-        if iterflag and errflag:
-            raise Exception("EXCEPTION: iteration limit exceeded")
+    if iterations > iterlimit:
+        raise Exception("EXCEPTION: iteration limit exceeded")
 
     return func(df, 'V1'), df['V1']

From aa5c19c5541aa0872f78239c45d8d86246d21b92 Mon Sep 17 00:00:00 2001
From: Cliff Hansen <cwhanse@sandia.gov>
Date: Wed, 19 Jan 2022 14:32:45 -0700
Subject: [PATCH 07/13] delete debugging stuff

---
 pvlib/tests/test_tools.py | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/pvlib/tests/test_tools.py b/pvlib/tests/test_tools.py
index 0a899e4c78..1013c89f12 100644
--- a/pvlib/tests/test_tools.py
+++ b/pvlib/tests/test_tools.py
@@ -42,7 +42,3 @@ def test__golden_sect_DataFrame_vector():
     expected = np.array([0.5, 0.25])
     v, x = tools._golden_sect_DataFrame(params, 0., 1., _obj_test_golden_sect)
     assert np.allclose(x, expected, atol=1e-8)
-
-
-params, lb, ub, expected, func = ({'c': 1., 'n': 1.}, 0., 1., 0.5, _obj_test_golden_sect)
-test__golden_sect_DataFrame(params, lb, ub, expected, func)

From 446b640d189f7f5623fc3818dc7f719e9311c517 Mon Sep 17 00:00:00 2001
From: Cliff Hansen <cwhanse@sandia.gov>
Date: Wed, 19 Jan 2022 20:52:48 -0700
Subject: [PATCH 08/13] screen out Io=nan in parameter estimation

---
 pvlib/ivtools/sdm.py            |  3 ++-
 pvlib/tests/ivtools/test_sdm.py | 18 +++++++++++++-----
 2 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/pvlib/ivtools/sdm.py b/pvlib/ivtools/sdm.py
index 04263c34c5..013e63f9a6 100644
--- a/pvlib/ivtools/sdm.py
+++ b/pvlib/ivtools/sdm.py
@@ -979,7 +979,8 @@ def _filter_params(ee, isc, io, rs, rsh):
     negrs = rs < 0.
     badrs = np.logical_or(rs > rsh, np.isnan(rs))
     imagrs = ~(np.isreal(rs))
-    badio = np.logical_or(~(np.isreal(rs)), io <= 0)
+    badio = np.logical_or(np.logical_or(~(np.isreal(rs)), io <= 0),
+                          np.isnan(io))
     goodr = np.logical_and(~badrsh, ~imagrs)
     goodr = np.logical_and(goodr, ~negrs)
     goodr = np.logical_and(goodr, ~badrs)
diff --git a/pvlib/tests/ivtools/test_sdm.py b/pvlib/tests/ivtools/test_sdm.py
index 13bab1ecde..e64928f80e 100644
--- a/pvlib/tests/ivtools/test_sdm.py
+++ b/pvlib/tests/ivtools/test_sdm.py
@@ -9,7 +9,7 @@
 
 from pvlib.tests.conftest import requires_pysam, requires_statsmodels
 
-from ..conftest import DATA_DIR
+#from ..conftest import DATA_DIR
 
 
 @pytest.fixture
@@ -125,8 +125,10 @@ def _read_iv_curves_for_test(datafile, npts):
     ivcurves = dict.fromkeys(['i_sc', 'i_mp', 'v_mp', 'v_oc', 'poa', 'tc',
                               'ee'])
 
-    infilen = DATA_DIR / datafile
-    with infilen.open(mode='r') as f:
+#    infilen = DATA_DIR / datafile
+    infilen = DATA_DIR + '/PVsyst_demo.csv'
+#    with infilen.open(mode='r') as f:
+    with open(infilen, mode='r') as f:
 
         Ns, aIsc, bVoc, descr = f.readline().split(',')
 
@@ -189,8 +191,10 @@ def _read_pvsyst_expected(datafile):
     varlist = ['iph', 'io', 'rs', 'rsh', 'u']
     pvsyst = dict.fromkeys(paramlist + varlist)
 
-    infilen = DATA_DIR / datafile
-    with infilen.open(mode='r') as f:
+#    infilen = DATA_DIR / datafile
+#    with infilen.open(mode='r') as f:
+    infilen = DATA_DIR + '\PVsyst_demo_model.csv'
+    with open(infilen, mode='r') as f:
 
         Ns, aIsc, bVoc, descr = f.readline().split(',')
 
@@ -400,3 +404,7 @@ def test_pvsyst_temperature_coeff():
         params['I_L_ref'], params['I_o_ref'], params['R_sh_ref'],
         params['R_sh_0'], params['R_s'], params['cells_in_series'])
     assert_allclose(gamma_pdc, expected, rtol=0.0005)
+
+
+DATA_DIR = 'C:\python\pvlib-remote\pvlib-python\pvlib\data'
+test_fit_pvsyst_sandia(npts=3000)

From 89a7d0836f4133c031980e672b6bd39235e13266 Mon Sep 17 00:00:00 2001
From: Cliff Hansen <cwhanse@sandia.gov>
Date: Wed, 19 Jan 2022 20:54:09 -0700
Subject: [PATCH 09/13] remove debugging code

---
 pvlib/tests/ivtools/test_sdm.py | 18 +++++-------------
 1 file changed, 5 insertions(+), 13 deletions(-)

diff --git a/pvlib/tests/ivtools/test_sdm.py b/pvlib/tests/ivtools/test_sdm.py
index e64928f80e..13bab1ecde 100644
--- a/pvlib/tests/ivtools/test_sdm.py
+++ b/pvlib/tests/ivtools/test_sdm.py
@@ -9,7 +9,7 @@
 
 from pvlib.tests.conftest import requires_pysam, requires_statsmodels
 
-#from ..conftest import DATA_DIR
+from ..conftest import DATA_DIR
 
 
 @pytest.fixture
@@ -125,10 +125,8 @@ def _read_iv_curves_for_test(datafile, npts):
     ivcurves = dict.fromkeys(['i_sc', 'i_mp', 'v_mp', 'v_oc', 'poa', 'tc',
                               'ee'])
 
-#    infilen = DATA_DIR / datafile
-    infilen = DATA_DIR + '/PVsyst_demo.csv'
-#    with infilen.open(mode='r') as f:
-    with open(infilen, mode='r') as f:
+    infilen = DATA_DIR / datafile
+    with infilen.open(mode='r') as f:
 
         Ns, aIsc, bVoc, descr = f.readline().split(',')
 
@@ -191,10 +189,8 @@ def _read_pvsyst_expected(datafile):
     varlist = ['iph', 'io', 'rs', 'rsh', 'u']
     pvsyst = dict.fromkeys(paramlist + varlist)
 
-#    infilen = DATA_DIR / datafile
-#    with infilen.open(mode='r') as f:
-    infilen = DATA_DIR + '\PVsyst_demo_model.csv'
-    with open(infilen, mode='r') as f:
+    infilen = DATA_DIR / datafile
+    with infilen.open(mode='r') as f:
 
         Ns, aIsc, bVoc, descr = f.readline().split(',')
 
@@ -404,7 +400,3 @@ def test_pvsyst_temperature_coeff():
         params['I_L_ref'], params['I_o_ref'], params['R_sh_ref'],
         params['R_sh_0'], params['R_s'], params['cells_in_series'])
     assert_allclose(gamma_pdc, expected, rtol=0.0005)
-
-
-DATA_DIR = 'C:\python\pvlib-remote\pvlib-python\pvlib\data'
-test_fit_pvsyst_sandia(npts=3000)

From 7234a10c85f373fd855ca3b3628d76962dae2957 Mon Sep 17 00:00:00 2001
From: Cliff Hansen <cwhanse@sandia.gov>
Date: Thu, 20 Jan 2022 09:54:25 -0700
Subject: [PATCH 10/13] remove iteration exception, not needed

---
 pvlib/tools.py | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/pvlib/tools.py b/pvlib/tools.py
index 2200f57b82..2324c408fb 100644
--- a/pvlib/tools.py
+++ b/pvlib/tools.py
@@ -321,11 +321,11 @@ def _golden_sect_DataFrame(params, VL, VH, func, atol=1e-8):
     df['VH'] = VH
     df['VL'] = VL
 
-    errflag = True
+    converged = False
     iterations = 0
     iterlimit = np.max(np.trunc(np.log(atol / (VH - VL)) / np.log(phim1))) + 1
 
-    while errflag and (iterations < iterlimit):
+    while not converged and (iterations < iterlimit):
 
         phi = phim1 * (df['VH'] - df['VL'])
         df['V1'] = df['VL'] + phi
@@ -339,11 +339,11 @@ def _golden_sect_DataFrame(params, VL, VH, func, atol=1e-8):
         df['VH'] = df['V1']*~df['SW_Flag'] + df['VH']*(df['SW_Flag'])
 
         err = abs(df['V2'] - df['V1'])
-        errflag = (err > atol).any()  # works because err is np.float64
 
+        # works with single value because err is np.float64
+        converged = (err < atol).all()
+        # err will be less than atol before iterations hit the limit
+        # but just to be safe
         iterations += 1
 
-    if iterations > iterlimit:
-        raise Exception("EXCEPTION: iteration limit exceeded")
-
     return func(df, 'V1'), df['V1']

From 7755635c37755b1beaac3371059650cd8731a9e1 Mon Sep 17 00:00:00 2001
From: Cliff Hansen <cwhanse@sandia.gov>
Date: Thu, 20 Jan 2022 09:56:57 -0700
Subject: [PATCH 11/13] whatsnew

---
 docs/sphinx/source/whatsnew/v0.9.1.rst | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/docs/sphinx/source/whatsnew/v0.9.1.rst b/docs/sphinx/source/whatsnew/v0.9.1.rst
index 4ddcb9bd51..92672d9bf8 100644
--- a/docs/sphinx/source/whatsnew/v0.9.1.rst
+++ b/docs/sphinx/source/whatsnew/v0.9.1.rst
@@ -24,6 +24,8 @@ Bug fixes
   and ``surface_azimuth`` inputs caused an error (:issue:`1127`, :issue:`1332`, :pull:`1361`) 
 * Changed the metadata entry for the wind speed unit to "Wind Speed Units" in
   the PSM3 iotools function (:pull:`1375`)
+* Improved convergence to maximum power point for :py:func:`pvlib.pvsystem.singlediode`
+  (:issue:`1087`, :pull:`1089`)
 
 Testing
 ~~~~~~~

From efb310788c380636b3a264cc9841f27a734c3b84 Mon Sep 17 00:00:00 2001
From: Cliff Hansen <cwhanse@sandia.gov>
Date: Mon, 24 Jan 2022 10:27:55 -0700
Subject: [PATCH 12/13] edits from review

---
 docs/sphinx/source/whatsnew/v0.9.1.rst |  6 ++--
 pvlib/tests/test_tools.py              |  5 ++-
 pvlib/tools.py                         | 49 +++++++++++++++-----------
 3 files changed, 36 insertions(+), 24 deletions(-)

diff --git a/docs/sphinx/source/whatsnew/v0.9.1.rst b/docs/sphinx/source/whatsnew/v0.9.1.rst
index 92672d9bf8..52e909d1ef 100644
--- a/docs/sphinx/source/whatsnew/v0.9.1.rst
+++ b/docs/sphinx/source/whatsnew/v0.9.1.rst
@@ -24,8 +24,10 @@ Bug fixes
   and ``surface_azimuth`` inputs caused an error (:issue:`1127`, :issue:`1332`, :pull:`1361`) 
 * Changed the metadata entry for the wind speed unit to "Wind Speed Units" in
   the PSM3 iotools function (:pull:`1375`)
-* Improved convergence to maximum power point for :py:func:`pvlib.pvsystem.singlediode`
-  (:issue:`1087`, :pull:`1089`)
+* Improved convergence when determining the maximum power point using
+  for :py:func:`pvlib.pvsystem.singlediode` with `method='lambertw'`. Tolerance
+  is determined for the voltage at the maximum power point, and is improved
+  from 0.01 V to 1e-8 V. (:issue:`1087`, :pull:`1089`)
 
 Testing
 ~~~~~~~
diff --git a/pvlib/tests/test_tools.py b/pvlib/tests/test_tools.py
index 1013c89f12..fa42fbf82d 100644
--- a/pvlib/tests/test_tools.py
+++ b/pvlib/tests/test_tools.py
@@ -39,6 +39,9 @@ def test__golden_sect_DataFrame_atol():
 
 def test__golden_sect_DataFrame_vector():
     params = {'c': np.array([1., 2.]), 'n': np.array([1., 1.])}
+    lower = np.array([0., 0.001])
+    upper = np.array([1.1, 1.2])
     expected = np.array([0.5, 0.25])
-    v, x = tools._golden_sect_DataFrame(params, 0., 1., _obj_test_golden_sect)
+    v, x = tools._golden_sect_DataFrame(params, lower, upper,
+                                        _obj_test_golden_sect)
     assert np.allclose(x, expected, atol=1e-8)
diff --git a/pvlib/tools.py b/pvlib/tools.py
index 2324c408fb..2177c75ba5 100644
--- a/pvlib/tools.py
+++ b/pvlib/tools.py
@@ -279,51 +279,55 @@ def _build_args(keys, input_dict, dict_name):
 # Author: Rob Andrews, Calama Consulting
 # Modified: November, 2020 by C. W. Hansen, to add atol and change exit
 # criteria
-def _golden_sect_DataFrame(params, VL, VH, func, atol=1e-8):
+def _golden_sect_DataFrame(params, lower, upper, func, atol=1e-8):
     """
-    Vectorized golden section search for finding MPP from a dataframe
-    timeseries.
+    Vectorized golden section search for finding maximum of a function of a
+    single variable.
 
     Parameters
     ----------
     params : dict or Dataframe
-        Parameters for the IV curve(s) where MPP will be found. Must contain
-        keys: 'r_sh', 'r_s', 'nNsVth', 'i_0', 'i_l'
-        of inputs to the function to be optimized.
-        Each row should represent an independent optimization.
+        Parameters to be passed to `func`.
 
-    VL: float
-        Lower bound on voltage for the optimization
+    lower: numeric
+        Lower bound for the optimization
 
-    VH: array-like
-        Upper bound on voltage for the optimization
+    upper: numeric
+        Upper bound for the optimization
 
     func: function
-        Function to be optimized must be in the form f(dict or Dataframe, str)
-        where str is the key corresponding to voltage
+        Function to be optimized. Must be in the form
+        result = f(dict or DataFrame, str), where result is a dict or DataFrame
+        that also contains the function output, and str is the key
+        corresponding to the function's input variable.
 
     Returns
     -------
-    func(params, 'V1') : dict or DataFrame
-        function evaluated at the optimal point
+    numeric
+        function evaluated at the optimal points
 
-    df['V1']: array-like or Series
-        Dataframe of optimal points
+    numeric
+        optimal points
 
     Notes
     -----
-    This function will find the MAXIMUM of a function
+    This function will find the points where the function is maximized.
+
+    See also
+    --------
+    pvlib.singlediode._pwr_optfcn
     """
 
     phim1 = (np.sqrt(5) - 1) / 2
 
     df = params
-    df['VH'] = VH
-    df['VL'] = VL
+    df['VH'] = upper
+    df['VL'] = lower
 
     converged = False
     iterations = 0
-    iterlimit = np.max(np.trunc(np.log(atol / (VH - VL)) / np.log(phim1))) + 1
+    iterlimit = 1 + np.max(
+        np.trunc(np.log(atol / (df['VH'] - df['VL'])) / np.log(phim1)))
 
     while not converged and (iterations < iterlimit):
 
@@ -346,4 +350,7 @@ def _golden_sect_DataFrame(params, VL, VH, func, atol=1e-8):
         # but just to be safe
         iterations += 1
 
+    if iterations > iterlimit:
+        raise Exception("iterations exceeded maximum")  # pragma: no cover
+
     return func(df, 'V1'), df['V1']

From 8b55eed569e41c258219d1b565e8d296516d542f Mon Sep 17 00:00:00 2001
From: Cliff Hansen <cwhanse@sandia.gov>
Date: Wed, 16 Feb 2022 11:39:02 -0700
Subject: [PATCH 13/13] Update docs/sphinx/source/whatsnew/v0.9.1.rst

Co-authored-by: Will Holmgren <william.holmgren@gmail.com>
---
 docs/sphinx/source/whatsnew/v0.9.1.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/docs/sphinx/source/whatsnew/v0.9.1.rst b/docs/sphinx/source/whatsnew/v0.9.1.rst
index 52e909d1ef..80a47ff0b4 100644
--- a/docs/sphinx/source/whatsnew/v0.9.1.rst
+++ b/docs/sphinx/source/whatsnew/v0.9.1.rst
@@ -25,7 +25,7 @@ Bug fixes
 * Changed the metadata entry for the wind speed unit to "Wind Speed Units" in
   the PSM3 iotools function (:pull:`1375`)
 * Improved convergence when determining the maximum power point using
-  for :py:func:`pvlib.pvsystem.singlediode` with `method='lambertw'`. Tolerance
+  for :py:func:`pvlib.pvsystem.singlediode` with ``method='lambertw'``. Tolerance
   is determined for the voltage at the maximum power point, and is improved
   from 0.01 V to 1e-8 V. (:issue:`1087`, :pull:`1089`)