Commit a73501b1 authored by Damien George's avatar Damien George
Browse files

py/objfloat: Add implementation of high-quality float hashing.

Disabled by default.
parent 816413e4
......@@ -548,6 +548,12 @@ typedef double mp_float_t;
#define MICROPY_PY_BUILTINS_COMPLEX (MICROPY_PY_BUILTINS_FLOAT)
#endif
// Whether to provide a high-quality hash for float and complex numbers.
// Otherwise the default is a very simple but correct hashing function.
#ifndef MICROPY_FLOAT_HIGH_QUALITY_HASH
#define MICROPY_FLOAT_HIGH_QUALITY_HASH (0)
#endif
// Enable features which improve CPython compatibility
// but may lead to more code size/memory usage.
// TODO: Originally intended as generic category to not
......
......@@ -730,7 +730,11 @@ void mp_str_print_quoted(const mp_print_t *print, const byte *str_data, size_t s
#if MICROPY_PY_BUILTINS_FLOAT
// float
#if MICROPY_FLOAT_HIGH_QUALITY_HASH
mp_int_t mp_float_hash(mp_float_t val);
#else
static inline mp_int_t mp_float_hash(mp_float_t val) { return (mp_int_t)val; }
#endif
mp_obj_t mp_obj_float_binary_op(mp_uint_t op, mp_float_t lhs_val, mp_obj_t rhs); // can return MP_OBJ_NULL if op not supported
// complex
......
......@@ -59,6 +59,55 @@ const mp_obj_float_t mp_const_float_pi_obj = {{&mp_type_float}, M_PI};
#endif
#if MICROPY_FLOAT_HIGH_QUALITY_HASH
// must return actual integer value if it fits in mp_int_t
mp_int_t mp_float_hash(mp_float_t src) {
#if MICROPY_FLOAT_IMPL == MICROPY_FLOAT_IMPL_DOUBLE
typedef uint64_t mp_float_uint_t;
#elif MICROPY_FLOAT_IMPL == MICROPY_FLOAT_IMPL_FLOAT
typedef uint32_t mp_float_uint_t;
#endif
union {
mp_float_t f;
#if MP_ENDIANNESS_LITTLE
struct { mp_float_uint_t frc:MP_FLOAT_FRAC_BITS, exp:MP_FLOAT_EXP_BITS, sgn:1; } p;
#else
struct { mp_float_uint_t sgn:1, exp:MP_FLOAT_EXP_BITS, frc:MP_FLOAT_FRAC_BITS; } p;
#endif
mp_float_uint_t i;
} u = {.f = src};
mp_int_t val;
const int adj_exp = (int)u.p.exp - MP_FLOAT_EXP_BIAS;
if (adj_exp < 0) {
// value < 1; must be sure to handle 0.0 correctly (ie return 0)
val = u.i;
} else {
// if adj_exp is max then: u.p.frc==0 indicates inf, else NaN
// else: 1 <= value
mp_float_uint_t frc = u.p.frc | ((mp_float_uint_t)1 << MP_FLOAT_FRAC_BITS);
if (adj_exp <= MP_FLOAT_FRAC_BITS) {
// number may have a fraction; xor the integer part with the fractional part
val = (frc >> (MP_FLOAT_FRAC_BITS - adj_exp))
^ (frc & ((1 << (MP_FLOAT_FRAC_BITS - adj_exp)) - 1));
} else if ((unsigned int)adj_exp < BITS_PER_BYTE * sizeof(mp_int_t) - 1) {
// the number is a (big) whole integer and will fit in val's signed-width
val = (mp_int_t)frc << (adj_exp - MP_FLOAT_FRAC_BITS);
} else {
// integer part will overflow val's width so just use what bits we can
val = frc;
}
}
if (u.p.sgn) {
val = -val;
}
return val;
}
#endif
STATIC void float_print(const mp_print_t *print, mp_obj_t o_in, mp_print_kind_t kind) {
(void)kind;
mp_float_t o_val = mp_obj_float_get(o_in);
......
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