From d99d853ef990df7d5589dc4c8ce69d9745f33367 Mon Sep 17 00:00:00 2001
From: Rob Taylor <rob@shape.build>
Date: Sun, 20 Dec 2020 23:19:31 +0000
Subject: [PATCH 1/2] Faster version of liberty_float - gives a 25% to 50%
 speedup

This also fixes a bug in liberty_float for numbers with a magnitute
between 9 and 15.

Previously:
    >>> liberty_float(1e15)
    '1000000000000000'
    >>> liberty_float(1e10)
    '10000000000.'
    >>> liberty_float(1e9)
    '1000000000.0'
    >>> liberty_float(1e16)
    '1.000000e+16'

Now:
    >>> liberty_float(1e15)
    '1.000000e+15'
    >>> liberty_float(1e10)
    '1.000000e+10'
    >>> liberty_float(1e9)
    '1000000000.0'
    >>> liberty_float(1e16)
    '1.000000e+16'
---
 .../skywater_pdk/liberty.py                   | 36 ++++++++-----------
 1 file changed, 14 insertions(+), 22 deletions(-)

diff --git a/scripts/python-skywater-pdk/skywater_pdk/liberty.py b/scripts/python-skywater-pdk/skywater_pdk/liberty.py
index 6cbda80..b14ec3e 100755
--- a/scripts/python-skywater-pdk/skywater_pdk/liberty.py
+++ b/scripts/python-skywater-pdk/skywater_pdk/liberty.py
@@ -31,12 +31,15 @@ from collections import defaultdict
 
 from typing import Tuple, List, Dict
 
+from math import frexp, log2
+
 from . import sizes
 from .utils import sortable_extracted_numbers
 
 
 debug = False
 
+LOG2_10 = log2(10)
 
 class TimingType(enum.IntFlag):
     """
@@ -792,36 +795,25 @@ def liberty_float(f):
 
     """
     try:
-        f2 = float(f)
+        r = float(f)
     except (ValueError, TypeError):
-        f2 = None
+        r = None
 
     if isinstance(f, bool):
-        f2 = None
+        r = None
 
-    if f is None or f2 != f:
+    if f is None or r != f:
         raise ValueError("%r is not a float" % f)
 
-    WIDTH = len(str(0.0083333333))
+    width = 11
 
-    s = json.dumps(f)
-    if 'e' in s:
-        a, b = s.split('e')
-        if '.' not in a:
-            a += '.'
-        while len(a)+len(b)+1 < WIDTH:
-            a += '0'
-        s = "%se%s" % (a, b)
-    elif '.' in s:
-        while len(s) < WIDTH:
-            s += '0'
+    mag = int(frexp(r)[1]/LOG2_10)
+    if mag > 9:
+        return f'%{width}e' % r
+    if mag < 0:
+        return f"%{width+1}.{width-1}f" % r
     else:
-        if len(s) < WIDTH:
-            s += '.'
-        while len(s) < WIDTH:
-            s += '0'
-    return s
-
+        return f"%{width+1}.{width-mag-1}f" % r
 
 LIBERTY_ATTRIBUTE_TYPES = {
     'boolean':  liberty_bool,

From 9d39c63f51ae10807711fe5be5e4baa796519b45 Mon Sep 17 00:00:00 2001
From: Rob Taylor <robtaylor@floopily.org>
Date: Mon, 21 Dec 2020 23:33:09 +0000
Subject: [PATCH 2/2] Add doctests for liberty_float edge case

Issue #280
---
 scripts/python-skywater-pdk/skywater_pdk/liberty.py | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/scripts/python-skywater-pdk/skywater_pdk/liberty.py b/scripts/python-skywater-pdk/skywater_pdk/liberty.py
index b14ec3e..77f2bb5 100755
--- a/scripts/python-skywater-pdk/skywater_pdk/liberty.py
+++ b/scripts/python-skywater-pdk/skywater_pdk/liberty.py
@@ -769,6 +769,15 @@ def liberty_float(f):
     >>> liberty_float(1)
     '1.0000000000'
 
+    >>> liberty_float(1e9)
+    '1000000000.0'
+
+    >>> liberty_float(1e10)
+    '1.000000e+10'
+
+    >>> liberty_float(1e15)
+    '1.000000e+15'
+
     >>> liberty_float(True)
     Traceback (most recent call last):
         ...