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return remainder from sqrt() to see what it looks like
author
Luke Kenneth Casson Leighton
<lkcl@lkcl.net>
Tue, 30 Apr 2019 01:48:40 +0000
(
02:48
+0100)
committer
Luke Kenneth Casson Leighton
<lkcl@lkcl.net>
Tue, 30 Apr 2019 01:48:40 +0000
(
02:48
+0100)
src/add/fsqrt.py
patch
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diff --git
a/src/add/fsqrt.py
b/src/add/fsqrt.py
index 9b4c32dc8b7413b7bf7538ab989e2c490c6ae835..c88aea3991f119b29a9415396292ddf64d626773 100644
(file)
--- a/
src/add/fsqrt.py
+++ b/
src/add/fsqrt.py
@@
-46,7
+46,7
@@
def sqrt(num):
if (R<0):
R = R+((Q<<1)|1)
r = R
if (R<0):
R = R+((Q<<1)|1)
r = R
- return Q
+ return Q
, r
# grabbed these from unit_test_single (convenience, this is just experimenting)
# grabbed these from unit_test_single (convenience, this is just experimenting)
@@
-80,9
+80,10
@@
def decode_fp32(x):
def main(mantissa, exponent):
if exponent & 1 != 0:
# shift mantissa up, subtract 1 from exp to compensate
def main(mantissa, exponent):
if exponent & 1 != 0:
# shift mantissa up, subtract 1 from exp to compensate
- return sqrt(mantissa << 1), (exponent - 1) >> 1
- # mantissa as-is, no compensating needed on exp
- return sqrt(mantissa), (exponent >> 1)
+ mantissa <<= 1
+ exponent -= 1
+ m, r = sqrt(mantissa)
+ return m, r, exponent >> 1
def fsqrt_test(x):
def fsqrt_test(x):
@@
-99,12
+100,13
@@
def fsqrt_test(x):
m |= 1<<23 # set top bit (the missing "1" from mantissa)
m <<= 27
m |= 1<<23 # set top bit (the missing "1" from mantissa)
m <<= 27
- sm, se = main(m, e)
+ sm, s
r, s
e = main(m, e)
lowbits = sm & 0x3
sm >>= 2
sm = get_mantissa(sm)
#sm += 2
lowbits = sm & 0x3
sm >>= 2
sm = get_mantissa(sm)
#sm += 2
- print("our sqrt", s, se, sm, hex(sm), bin(sm), "lowbits", lowbits)
+ print("our sqrt", s, se, sm, hex(sm), bin(sm), "lowbits", lowbits,
+ "rem", hex(sr))
if lowbits >= 2:
print ("probably needs rounding (+1 on mantissa)")
if lowbits >= 2:
print ("probably needs rounding (+1 on mantissa)")
@@
-119,13
+121,13
@@
if __name__ == '__main__':
for Q in range(1, int(1e4)):
print(Q, sqrt(Q), sqrtsimple(Q), int(Q**0.5))
assert int(Q**0.5) == sqrtsimple(Q), "Q sqrtsimpl fail %d" % Q
for Q in range(1, int(1e4)):
print(Q, sqrt(Q), sqrtsimple(Q), int(Q**0.5))
assert int(Q**0.5) == sqrtsimple(Q), "Q sqrtsimpl fail %d" % Q
- assert int(Q**0.5) == sqrt(Q), "Q sqrt fail %d" % Q
+ assert int(Q**0.5) == sqrt(Q)
[0]
, "Q sqrt fail %d" % Q
# quick mantissa/exponent demo
for e in range(26):
for m in range(26):
# quick mantissa/exponent demo
for e in range(26):
for m in range(26):
- ms, es = main(m, e)
- print("m:%d e:%d sqrt: m:%d
e:%d" % (m, e, ms
, es))
+ ms,
mr,
es = main(m, e)
+ print("m:%d e:%d sqrt: m:%d
-%d e:%d" % (m, e, ms, mr
, es))
x = Float32(1234.123456789)
fsqrt_test(x)
x = Float32(1234.123456789)
fsqrt_test(x)
@@
-141,6
+143,8
@@
if __name__ == '__main__':
fsqrt_test(x)
x = Float32(12.99392923123123)
fsqrt_test(x)
fsqrt_test(x)
x = Float32(12.99392923123123)
fsqrt_test(x)
+ x = Float32(0.123456)
+ fsqrt_test(x)
"""
"""