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Refinement for speedup.

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git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@4401 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
This commit is contained in:
shigek 2003-08-17 14:35:53 +00:00
parent 39c4886fe7
commit a8027639b8
1 changed files with 20 additions and 24 deletions
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44
ext/bigdecimal/lib/bigdecimal/math.rb
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@ -10,14 +10,15 @@
#
# where:
# x ... BigDecimal number to be computed.
# |x| must be small enough to get convergence.
# prec ... Number of digits to be obtained.
#
# Usage:
# require "bigdecimal"
# require "bigdecimal/math.rb"
# include BigMath
# a = BigDecimal((PI(1000)/2).to_s)
# puts sin(a,1000) # => 0.10000000000000000000......E1
# a = BigDecimal((PI(100)/2).to_s)
# puts sin(a,100) # => 0.10000000000000000000......E1
#
module BigMath
def sqrt(x,prec)
@ -28,11 +29,10 @@ module BigMath
raise ArgumentError, "Zero or negative precision for sin" if prec <= 0
return BigDecimal("NaN") if x.infinite? || x.nan?
n = prec + BigDecimal.double_fig
n2 = n+n
one = BigDecimal("1")
two = BigDecimal("2")
x1 = x
x2 = x * x
x2 = x.mult(x,n)
sign = 1
y = x
d = y
@ -41,7 +41,7 @@ module BigMath
while d.nonzero? && ((m = n - (y.exponent - d.exponent).abs) > 0)
m = BigDecimal.double_fig if m < BigDecimal.double_fig
sign = -sign
x1 = x2.mult(x1,n2)
x1 = x2.mult(x1,n)
i += two
z *= (i-one) * i
d = sign * x1.div(z,m)
@ -54,11 +54,10 @@ module BigMath
raise ArgumentError, "Zero or negative precision for sin" if prec <= 0
return BigDecimal("NaN") if x.infinite? || x.nan?
n = prec + BigDecimal.double_fig
n2 = n+n
one = BigDecimal("1")
two = BigDecimal("2")
x1 = one
x2 = x * x
x2 = x.mult(x,n)
sign = 1
y = one
d = y
@ -67,7 +66,7 @@ module BigMath
while d.nonzero? && ((m = n - (y.exponent - d.exponent).abs) > 0)
m = BigDecimal.double_fig if m < BigDecimal.double_fig
sign = -sign
x1 = x2.mult(x1,n2)
x1 = x2.mult(x1,n)
i += two
z *= (i-one) * i
d = sign * x1.div(z,m)
@ -81,15 +80,14 @@ module BigMath
return BigDecimal("NaN") if x.infinite? || x.nan?
raise ArgumentError, "x.abs must be less than 1.0" if x.abs>=1
n = prec + BigDecimal.double_fig
n2 = n+n
y = x;
d = y;
t = x;
r = BigDecimal("3");
x2 = x*x
y = x
d = y
t = x
r = BigDecimal("3")
x2 = x.mult(x,n)
while d.nonzero? && ((m = n - (y.exponent - d.exponent).abs) > 0)
m = BigDecimal.double_fig if m < BigDecimal.double_fig
t = -t.mult(x2,n2)
t = -t.mult(x2,n)
d = t.div(r,m)
y += d
r += 2
@ -101,7 +99,6 @@ module BigMath
raise ArgumentError, "Zero or negative precision for sin" if prec <= 0
return BigDecimal("NaN") if x.infinite? || x.nan?
n = prec + BigDecimal.double_fig
n2 = n+n
one = BigDecimal("1")
x1 = one
y = one
@ -110,7 +107,7 @@ module BigMath
i = 0
while d.nonzero? && ((m = n - (y.exponent - d.exponent).abs) > 0)
m = BigDecimal.double_fig if m < BigDecimal.double_fig
x1 = x1.mult(x,n2)
x1 = x1.mult(x,n)
i += 1
z *= i
d = x1.div(z,m)
@ -125,20 +122,19 @@ module BigMath
one = BigDecimal("1")
two = BigDecimal("2")
n = prec + BigDecimal.double_fig
n2 = n + n
x = (x - one).div(x + one,n)
x2 = x * x
y = two * x
x2 = x.mult(x,n)
y = x
d = y
i = one
while d.nonzero? && ((m = n - (y.exponent - d.exponent).abs) > 0)
m = BigDecimal.double_fig if m < BigDecimal.double_fig
x = x2.mult(x,n2)
x = x2.mult(x,n)
i += two
d = (two * x).div(i,m)
d = x.div(i,m)
y += d
end
y
y*two
end
def PI(prec)
@ -171,7 +167,7 @@ module BigMath
t = BigDecimal("956")
while d.nonzero? && ((m = n - (pi.exponent - d.exponent).abs) > 0)
m = BigDecimal.double_fig if m < BigDecimal.double_fig
t = t.div(m57121,m)
t = t.div(m57121,n)
d = t.div(k,m)
pi = pi + d
k = k+two