From b669834f8d5b015d67bb962c3d4287c49ca10257 Mon Sep 17 00:00:00 2001
From: Andrew Fitzgibbon <awf@graphcore.ai>
Date: Thu, 6 Jun 2024 13:54:08 +0100
Subject: [PATCH] Fix for K=64

---
 src/gfloat/round.py | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/src/gfloat/round.py b/src/gfloat/round.py
index 3f5b78b..b31f32c 100644
--- a/src/gfloat/round.py
+++ b/src/gfloat/round.py
@@ -62,8 +62,6 @@ def round_float(
         # Extract exponent
         expval = int(np.floor(np.log2(vpos)))
 
-        assert expval > -1024 + p  # not yet tested for float64 near-subnormals
-
         # Effective precision, accounting for right shift for subnormal values
         if fi.has_subnormals:
             expval = max(expval, 1 - bias)
@@ -71,7 +69,8 @@ def round_float(
         # Lift to "integer * 2^e"
         expval = expval - p + 1
 
-        fsignificand = vpos * 2.0**-expval
+        # use ldexp instead of vpos*2**-expval to avoid overflow
+        fsignificand = math.ldexp(vpos, -expval)
 
         # Round
         isignificand = math.floor(fsignificand)