Module: FPU

Defined in:
lib/fpu.rb,
ext/fpu.c

Overview

This module provides the way of controlling the rounding mode of the floating-point unit (FPU) and also provides mathematical functions that round their result consistently with the specified rounding mode.

Constant Summary collapse

StandardRounding =

:stopdoc:

rounding
PlusRounding =

:nodoc:

up { rounding }
MinusRounding =

:nodoc:

down{ rounding }

Class Method Summary collapse

Class Method Details

.down ⇒ Object

Perform a computation with the FPU rounding downwards.

Example:

FPU.down{1/5.0} < FPU.up{1/5.0}     # => true



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# File 'lib/fpu.rb', line 42

def FPU.down
  saved = roundingDown
  yield
ensure
  self.rounding = saved
end

.power(x, n) ⇒ Object

Raise x to the n-th power with correct rounding.



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# File 'lib/fpu.rb', line 63

def FPU.power(x, n)
  if Float === x && Integer === n
    return 1/FPU.power(x,-n) if n < 0
    l=[];
    while n > 0
      n,y=n.divmod(2);
      l=[y,l]
    end
    l.flatten.inject(1){|p,i| if i == 1 then p*p*x; else p*p; end}
  else
    x ** n
  end
end

.rounding ⇒ Object

Get the FPU’s rounding mode.



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# File 'ext/fpu.c', line 20

static VALUE mFPU_rounding(VALUE self)
{
  return UINT2NUM(fegetround());
}

.rounding=(mode) ⇒ Object

Set the FPU’s rounding mode.



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# File 'ext/fpu.c', line 28

static VALUE mFPU_rounding_set(VALUE self, VALUE mode)
{
  fesetround(NUM2UINT(mode));
  return UINT2NUM(fegetround());
}

.roundingDown ⇒ Object

Enable the FPU’s downward rounding.



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# File 'ext/fpu.c', line 47

static VALUE mFPU_rounding_down(VALUE self)
{
  int saved = fegetround();
  fesetround(FE_DOWNWARD);
  return UINT2NUM(saved);
}

.roundingUp ⇒ Object

Enable the FPU’s upward rounding.



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# File 'ext/fpu.c', line 37

static VALUE mFPU_rounding_up(VALUE self)
{
  int saved = fegetround();
  fesetround(FE_UPWARD);
  return UINT2NUM(saved);
}

.up ⇒ Object

Perform a computation with the FPU rounding upwards.

Example:

FPU.down{1/5.0} < FPU.up{1/5.0}     # => true



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# File 'lib/fpu.rb', line 55

def FPU.up
  saved = roundingUp
  yield
ensure
  self.rounding = saved
end