Source code for gfloat.printing

# Copyright (c) 2024 Graphcore Ltd. All rights reserved.

import fractions

import numpy as np


[docs] def float_pow2str(v: float, min_exponent: float = -np.inf) -> str: """ Render floating point values as exact fractions times a power of two. Example: float_pow2str(127.0) is "127/64*2^6", That is (a significand between 1 and 2) times (a power of two). If `min_exponent` is supplied, then values with exponent below `min_exponent`, are printed as fractions less than 1, with exponent set to `min_exponent`. This is typically used to represent subnormal values. """ if not np.isfinite(v): return str(v) s = np.sign(v) x = np.abs(v) e = np.floor(np.log2(x)) sig = x * 2.0**-e if e < min_exponent: sig *= 2.0 ** (e - min_exponent) e = min_exponent significand = fractions.Fraction(sig) return ("-" if s < 0 else "") + f"{significand}*2^{int(e):d}"
[docs] def float_tilde_unless_roundtrip_str(v: float, width: int = 14, d: int = 8) -> str: """ Return a string representation of :paramref:`v`, in base 10, with maximum width :paramref:`width` and decimal digits :paramref:`d` """ # valstr: string representation of value in base 10 # If the representation does not roundtrip to the value, # it is preceded by a "~" to indicate "approximately equal to" s = f"{v}" if len(s) > width: if abs(v) < 1 and not "e" in s: s = f"{v:.{d}f}" else: s = f"{v:.{d}}" if np.isfinite(v) and float(s) != v: s = "~" + s return s