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minor code-shuffle on sqrt() fn
[ieee754fpu.git]
/
src
/
add
/
fsqrt.py
diff --git
a/src/add/fsqrt.py
b/src/add/fsqrt.py
index 2171646c51a54e7da9284105698ab18b84fe8349..a87af61db4ded516df1f93d6cb3af933d6318af3 100644
(file)
--- a/
src/add/fsqrt.py
+++ b/
src/add/fsqrt.py
@@
-23,30
+23,24
@@
def sqrtsimple(num):
def sqrt(num):
D = num # D is input (from num)
Q = 0
def sqrt(num):
D = num # D is input (from num)
Q = 0
- R = 0
- r = 0 # remainder
+ R = 0 # remainder
for i in range(64, -1, -1): # negative ranges are weird...
for i in range(64, -1, -1): # negative ranges are weird...
- if (R>=0):
-
- R = (R<<2)|((D>>(i+i))&3)
- R = R-((Q<<2)|1) #/*-Q01*/
+ R = (R<<2)|((D>>(i+i))&3)
+ if R >= 0:
+ R -= ((Q<<2)|1) # -Q01
else:
else:
+ R += ((Q<<2)|3) # +Q11
- R = (R<<2)|((D>>(i+i))&3)
- R = R+((Q<<2)|3) #/*+Q11*/
-
- if (R>=0):
- Q = (Q<<1)|1 #/*new Q:*/
- else:
- Q = (Q<<1)|0 #/*new Q:*/
+ Q <<= 1
+ if R >= 0:
+ Q |= 1 # new Q
+ if R < 0:
+ R = R + ((Q<<1)|1)
- 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
+74,10
@@
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):
@@
-97,13
+92,17
@@
def fsqrt_test(x):
print("x decode", s, e, m, hex(m))
m |= 1<<23 # set top bit (the missing "1" from mantissa)
print("x decode", s, e, m, hex(m))
m |= 1<<23 # set top bit (the missing "1" from mantissa)
- m <<= 2
5
+ m <<= 2
7
- sm, se = main(m, e)
- sm >>= 1
+ sm, sr, se = main(m, e)
+ lowbits = sm & 0x3
+ sm >>= 2
sm = get_mantissa(sm)
#sm += 2
sm = get_mantissa(sm)
#sm += 2
- print("our sqrt", s, se, sm, hex(sm), bin(sm))
+ 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)")
sq_xbits = sq_test.bits
s, e, m = decode_fp32(sq_xbits)
sq_xbits = sq_test.bits
s, e, m = decode_fp32(sq_xbits)
@@
-116,13
+115,13
@@
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)
@@
-134,6
+133,12
@@
if __name__ == '__main__':
fsqrt_test(x)
x = Float32(8.5)
fsqrt_test(x)
fsqrt_test(x)
x = Float32(8.5)
fsqrt_test(x)
+ x = Float32(3.14159265358979323)
+ fsqrt_test(x)
+ x = Float32(12.99392923123123)
+ fsqrt_test(x)
+ x = Float32(0.123456)
+ fsqrt_test(x)
"""
"""