diff options
| -rw-r--r-- | py/parsenum.c | 14 | ||||
| -rw-r--r-- | tests/float/float_parse.py | 5 | ||||
| -rw-r--r-- | tests/float/float_parse_doubleprec.py | 5 |
3 files changed, 22 insertions, 2 deletions
diff --git a/py/parsenum.c b/py/parsenum.c index 98e773685..124489c66 100644 --- a/py/parsenum.c +++ b/py/parsenum.c @@ -172,10 +172,15 @@ mp_obj_t mp_parse_num_decimal(const char *str, size_t len, bool allow_imag, bool #if MICROPY_PY_BUILTINS_FLOAT // DEC_VAL_MAX only needs to be rough and is used to retain precision while not overflowing +// SMALL_NORMAL_VAL is the smallest power of 10 that is still a normal float #if MICROPY_FLOAT_IMPL == MICROPY_FLOAT_IMPL_FLOAT #define DEC_VAL_MAX 1e20F +#define SMALL_NORMAL_VAL (1e-37F) +#define SMALL_NORMAL_EXP (-37) #elif MICROPY_FLOAT_IMPL == MICROPY_FLOAT_IMPL_DOUBLE #define DEC_VAL_MAX 1e200 +#define SMALL_NORMAL_VAL (1e-307) +#define SMALL_NORMAL_EXP (-307) #endif const char *top = str + len; @@ -275,8 +280,13 @@ mp_obj_t mp_parse_num_decimal(const char *str, size_t len, bool allow_imag, bool exp_val = -exp_val; } - // apply the exponent - dec_val *= MICROPY_FLOAT_C_FUN(pow)(10, exp_val + exp_extra); + // apply the exponent, making sure it's not a subnormal value + exp_val += exp_extra; + if (exp_val < SMALL_NORMAL_EXP) { + exp_val -= SMALL_NORMAL_EXP; + dec_val *= SMALL_NORMAL_VAL; + } + dec_val *= MICROPY_FLOAT_C_FUN(pow)(10, exp_val); } // negate value if needed diff --git a/tests/float/float_parse.py b/tests/float/float_parse.py index 448eff3bc..de4ea455f 100644 --- a/tests/float/float_parse.py +++ b/tests/float/float_parse.py @@ -20,3 +20,8 @@ print(float('.' + '9' * 70 + 'e-50') == float('1e-50')) print(float('.' + '0' * 60 + '1e10') == float('1e-51')) print(float('.' + '0' * 60 + '9e25')) print(float('.' + '0' * 60 + '9e40')) + +# 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')) diff --git a/tests/float/float_parse_doubleprec.py b/tests/float/float_parse_doubleprec.py index 356601130..2ea7842f3 100644 --- a/tests/float/float_parse_doubleprec.py +++ b/tests/float/float_parse_doubleprec.py @@ -14,3 +14,8 @@ print(float('.' + '9' * 400 + 'e-100')) print(float('.' + '0' * 400 + '9e100')) print(float('.' + '0' * 400 + '9e200')) print(float('.' + '0' * 400 + '9e400')) + +# ensure that accuracy is retained when value is close to a subnormal +print(float('1.00000000000000000000e-307')) +print(float('10.0000000000000000000e-308')) +print(float('100.000000000000000000e-309')) |