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micropython/tests/float/float_parse.py

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py/parsenum: Improve parsing of floating point numbers. This patch improves parsing of floating point numbers by converting all the digits (integer and fractional) together into a number 1 or greater, and then applying the correct power of 10 at the very end. In particular the multiple "multiply by 0.1" operations to build a fraction are now combined together and applied at the same time as the exponent, at the very end. This helps to retain precision during parsing of floats, and also includes a check that the number doesn't overflow during the parsing. One benefit is that a float will have the same value no matter where the decimal point is located, eg 1.23 == 123e-2.
2017-11-27 01:51:52 +00:00
# test parsing of floats
inf = float('inf')
# it shouldn't matter where the decimal point is if the exponent balances the value
print(float('1234') - float('0.1234e4'))
print(float('1.015625') - float('1015625e-6'))
# very large integer part with a very negative exponent should cancel out
tests/float: Adjust float-parsing tests to pass with only a small error. Float parsing (both single and double precision) may have a relative error of order the floating point precision, so adjust tests to take this into account by not printing all of the digits of the answer.
2018-02-26 04:54:03 +00:00
print('%.4e' % float('9' * 60 + 'e-60'))
print('%.4e' % float('9' * 60 + 'e-40'))
py/parsenum: Improve parsing of floating point numbers. This patch improves parsing of floating point numbers by converting all the digits (integer and fractional) together into a number 1 or greater, and then applying the correct power of 10 at the very end. In particular the multiple "multiply by 0.1" operations to build a fraction are now combined together and applied at the same time as the exponent, at the very end. This helps to retain precision during parsing of floats, and also includes a check that the number doesn't overflow during the parsing. One benefit is that a float will have the same value no matter where the decimal point is located, eg 1.23 == 123e-2.
2017-11-27 01:51:52 +00:00
# many fractional digits
print(float('.' + '9' * 70))
print(float('.' + '9' * 70 + 'e20'))
print(float('.' + '9' * 70 + 'e-50') == float('1e-50'))
# tiny fraction with large exponent
print(float('.' + '0' * 60 + '1e10') == float('1e-51'))
tests/float/float_parse: Allow test to run on 32-bit archs. Printing of uPy floats can differ by the floating-point precision on different architectures (eg 64-bit vs 32-bit x86), so it's not possible to using printing of floats in some parts of this test. Instead we can just check for equivalence with what is known to be the correct answer.
2018-05-11 04:51:18 +01:00
print(float('.' + '0' * 60 + '9e25') == float('9e-36'))
print(float('.' + '0' * 60 + '9e40') == float('9e-21'))
py/parsenum: Fix parsing of floats that are close to subnormal. Prior to this patch, a float literal that was close to subnormal would have a loss of precision when parsed. The worst case was something like float('10000000000000000000e-326') which returned 0.0.
2018-02-08 03:02:50 +00:00
# ensure that accuracy is retained when value is close to a subnormal
print(float('1.00000000000000000000e-37'))
print(float('10.0000000000000000000e-38'))
print(float('100.000000000000000000e-39'))
tests: Add some tests for bigint hash, float hash and float parsing. Following outcome of recent fuzz testing and sanitizing by @jepler.
2018-05-21 04:05:40 +01:00
# very large exponent literal
print(float('1e4294967301'))
print(float('1e-4294967301'))
print(float('1e18446744073709551621'))
print(float('1e-18446744073709551621'))