Class: Flt::DoubleFormat

Inherits:

FormatBase

• Object
• FormatBase
• Flt::DoubleFormat

Defined in:

lib/float-formats/classes.rb

Overview

Class to define formats such as “double double” by pairing two floating-point values which define a higher precision value by its sum. The :half parameter is a format class that defines the type of each part of the numbers. The formats defined here have a fixed precision, although these formats can actually have a variable precision. For binary formats there’s an option to gain one bit of precision by adjusting the sign of the second number. This is enabled by the :extra_prec option. For example, the “double double” format used in PowerPC is this

Flt.define :DoubleDouble, DoubleFormat, half: IEEE_binary64, extra_prec: true

Although this has a fixed 107 bits precision, the format as used in the PowerPC can have greater precision for specific values (by having greater separation between the exponents of both halves)

Constant Summary

Constants included from Flt

APPLE, IEEE_128, IEEE_128_BE, IEEE_DEC128, IEEE_DEC32, IEEE_DEC64, IEEE_DOUBLE, IEEE_D_BE, IEEE_EXTENDED, IEEE_HALF, IEEE_H_BE, IEEE_QUAD, IEEE_Q_BE, IEEE_SINGLE, IEEE_S_BE, IEEE_X_BE, IEEE_binaryx, RPL, RPL_X

Instance Attribute Summary

Attributes inherited from FormatBase

#exponent, #sign, #significand

Class Method Summary

• .define(params) ⇒ Object
• .half ⇒ Object
• .join_halfs(h1, h2) ⇒ Object
• .pack(s, m, e) ⇒ Object
• .radix ⇒ Object
• .total_bits ⇒ Object
• .total_bytes ⇒ Object
• .total_nibbles ⇒ Object
• .unpack(v) ⇒ Object

Instance Method Summary

• #split_halfs ⇒ Object

Methods inherited from FormatBase

#<=>, arithmetic, arithmetic_type, bias, canonicalized, context, #convert_to, decimal_digits_necessary, decimal_digits_stored, decimal_max_exp, decimal_min_exp, endianness, epsilon, #form_class, #fp_format, from, from_bits, from_bits_text, from_bytes, from_hex, from_number, from_text, gradual_underflow?, half_epsilon, #infinite?, infinity, #initialize, join, max_value, maximum_integral_significand, min_normalized_value, min_value, minimum_normalized_integral_significand, #minus, minus_sign_value, nan, #nan?, #next_minus, #next_plus, #normal?, num, num_class, numerals_conversion, pack_fields_hash, radix_log, radix_log10, radix_max_exp, radix_min_exp, radix_power, rounding_mode, sign_from_unit, sign_to_unit, #split, strict_epsilon, #subnormal?, switch_sign_value, #to, #to_a, #to_bits, #to_bits_text, #to_bytes, #to_hex, #to_num, #to_text, #ulp, unpack_fields_hash, zero, #zero?

Methods included from Flt

#*, #+, #-, #-@, #/, bcd2dpd, bitnot, convert_bytes, dbl_from_float, dbl_from_text, dbl_to_float, dpd2bcd, dpd_to_hexbcd, float_bin, float_dec, float_from_integral_sign_significand_exponent, float_from_integral_significand_exponent, float_shortest_dec, float_significant_dec, float_to_integral_sign_significand_exponent, float_to_integral_significand_exponent, hex_from_float, hex_to_float, hexbcd_to_dpd, sgl_from_float, sgl_from_text, sgl_to_float

Constructor Details

This class inherits a constructor from Flt::FormatBase

Class Method Details

.define(params) ⇒ Object

# File 'lib/float-formats/classes.rb', line 1794

def self.define(params)
  @half = params[:half]
  params = @half.parameters.merge(params)
  if @half.radix==2
    @extra_prec = params[:extra_prec]
  else
    @extra_prec = false
  end
  params[:significand_digits] = 2*@half.significand_digits
  params[:significand_digits] += 1 if @extra_prec
  @significand_digits = params[:significand_digits]

  @hidden_bit = params[:hidden_bit] = @half.hidden_bit

  fields1 = []
  fields2 = []
  params[:fields].each_slice(2) do |s,v|
    fields1 << s # (s.to_s+"_1").to_sym
    fields1 << v
    fields2 << (s.to_s+"_2").to_sym
    fields2 << v
  end
  params[:fields] = fields1 + fields2

  define_fields params[:fields]

  super params
end

.half ⇒ Object

# File 'lib/float-formats/classes.rb', line 1827

def self.half
  @half
end

.join_halfs(h1, h2) ⇒ Object

# File 'lib/float-formats/classes.rb', line 1866

def self.join_halfs(h1,h2)
  self.from_bytes(h1.to_bytes+h2.to_bytes)
end

.pack(s, m, e) ⇒ Object

# File 'lib/float-formats/classes.rb', line 1846

def self.pack(s,m,e)
  if e.kind_of?(Symbol)
    f1 = @half.pack(s,m,e)
    f2 = @half.pack(+1,0,:zero)
  else
    s1,m1,e1,s2,m2,e2 = split_fp(s,m,e)
    f1 = @half.pack(s1,m1,e1)
    f2 = @half.pack(s2,m2,e2)
  end
  f1+f2
end

.radix ⇒ Object

# File 'lib/float-formats/classes.rb', line 1823

def self.radix
  @half.radix
end

.total_bits ⇒ Object

# File 'lib/float-formats/classes.rb', line 1876

def self.total_bits
  8*total_bytes
end

.total_bytes ⇒ Object

# File 'lib/float-formats/classes.rb', line 1873

def self.total_bytes
  2*@half.total_bytes
end

.total_nibbles ⇒ Object

# File 'lib/float-formats/classes.rb', line 1870

def self.total_nibbles
  2*total_bytes
end

.unpack(v) ⇒ Object

# File 'lib/float-formats/classes.rb', line 1831

def self.unpack(v)
  sz = @half.total_bytes
  v1 = @half.unpack(v[0...sz])
  v2 = @half.unpack(v[sz..-1])
  if v1.last == :nan
    nan
  elsif v1.last == :infinity
    infinity(v1.sign)
  else
    v2 = @half.zero.split if @half.new(*v1).subnormal?
    params = v1 + v2
    join_fp(*params)
  end
end

Instance Method Details

#split_halfs ⇒ Object

# File 'lib/float-formats/classes.rb', line 1858

def split_halfs
  b = to_bytes
  sz = form_class.half.total_bytes
  b1 = b[0...sz]
  b2 = b[sz..-1]
  [form_class.half.from_bytes(b1), form_class.half.from_bytes(b2)]
end