Micro optimizations

Author: edubart

Makefile

@@ -1,13 +1,14 @@
 ROCKSPEC=rockspecs/bint-0.*.rockspec
+LUA?=lua
 
 test:
-lua tests.lua
-lua examples/simple.lua
-lua examples/fibonacci.lua
-lua examples/factorial.lua
-lua examples/pi.lua
-lua examples/e.lua
-lua examples/rsa.lua
+$(LUA) tests.lua
+$(LUA) examples/simple.lua
+$(LUA) examples/fibonacci.lua
+$(LUA) examples/factorial.lua
+$(LUA) examples/pi.lua
+$(LUA) examples/e.lua
+$(LUA) examples/rsa.lua
 
 docs:
 ldoc -d docs -f markdown bint.lua

bint.lua

@@ -953,7 +953,7 @@ function bint:_add(y)
  local carry = 0
  for i=1,BINT_SIZE do
  local tmp = self[i] + y[i] + carry
- carry = tmp > BINT_WORDMAX and 1 or 0
+ carry = tmp >> BINT_WORDBITS
  self[i] = tmp & BINT_WORDMAX
  end
  return self
@@ -969,7 +969,7 @@ function bint.__add(x, y)
  local carry = 0
  for i=1,BINT_SIZE do
  local tmp = ix[i] + iy[i] + carry
- carry = tmp > BINT_WORDMAX and 1 or 0
+ carry = tmp >> BINT_WORDBITS
  z[i] = tmp & BINT_WORDMAX
  end
  return z
@@ -986,9 +986,9 @@ function bint:_sub(y)
  local borrow = 0
  local wordmaxp1 = BINT_WORDMAX + 1
  for i=1,BINT_SIZE do
- local res = (self[i] + wordmaxp1) - (y[i] + borrow)
+ local res = self[i] + wordmaxp1 - y[i] - borrow
  self[i] = res & BINT_WORDMAX
- borrow = res <= BINT_WORDMAX and 1 or 0
+ borrow = (res >> BINT_WORDBITS) ~ 1
  end
  return self
 end
@@ -1003,9 +1003,9 @@ function bint.__sub(x, y)
  local borrow = 0
  local wordmaxp1 = BINT_WORDMAX + 1
  for i=1,BINT_SIZE do
- local res = (ix[i] + wordmaxp1) - (iy[i] + borrow)
+ local res = ix[i] + wordmaxp1 - iy[i] - borrow
  z[i] = res & BINT_WORDMAX
- borrow = res <= BINT_WORDMAX and 1 or 0
+ borrow = (res >> BINT_WORDBITS) ~ 1
  end
  return z
  else
@@ -1036,7 +1036,7 @@ function bint.__mul(x, y)
  local carry = 0
  for k=i+j-1,BINT_SIZE do
  local tmp = z[k] + (a & BINT_WORDMAX) + carry
- carry = tmp > BINT_WORDMAX and 1 or 0
+ carry = tmp >> BINT_WORDBITS
  z[k] = tmp & BINT_WORDMAX
  a = a >> BINT_WORDBITS
  end
@@ -1138,9 +1138,9 @@ function bint.udivmod(x, y)
  -- subtract denominator from the portion of the numerator
  local borrow = 0
  for i=1,size do
- local res = (nume[i] + wordmaxp1) - (deno[i] + borrow)
+ local res = nume[i] + wordmaxp1 - deno[i] - borrow
  nume[i] = res & BINT_WORDMAX
- borrow = res <= BINT_WORDMAX and 1 or 0
+ borrow = (res >> BINT_WORDBITS) ~ 1
  end
  -- concatenate 1 to the right bit of the quotient
  local i = (bit // BINT_WORDBITS) + 1
@@ -1200,21 +1200,28 @@ end
 function bint.idivmod(x, y)
  local ix, iy = bint.tobint(x), bint.tobint(y)
  if ix and iy then
- local quot, rema = bint.udivmod(ix:abs(), iy:abs())
- local isnumneg, isdenomneg = ix:isneg(), iy:isneg()
- if isnumneg ~= isdenomneg then
+ local isnumeneg = ix[BINT_SIZE] & BINT_WORDMSB ~= 0
+ local isdenoneg = iy[BINT_SIZE] & BINT_WORDMSB ~= 0
+ if isnumeneg then
+ ix = -ix
+ end
+ if isdenoneg then
+ iy = -iy
+ end
+ local quot, rema = bint.udivmod(ix, iy)
+ if isnumeneg ~= isdenoneg then
  quot:_unm()
  -- round quotient towards minus infinity
  if not rema:iszero() then
  quot:_dec()
  -- adjust the remainder
- if isnumneg and not isdenomneg then
+ if isnumeneg and not isdenoneg then
  rema:_unm():_add(y)
- elseif isdenomneg and not isnumneg then
+ elseif isdenoneg and not isnumeneg then
  rema:_add(y)
  end
  end
- elseif isnumneg then
+ elseif isnumeneg then
  -- adjust the remainder
  rema:_unm()
  end
@@ -1235,8 +1242,16 @@ end
 function bint.__idiv(x, y)
  local ix, iy = bint.tobint(x), bint.tobint(y)
  if ix and iy then
- local quot, rema = bint.udivmod(ix:abs(), iy:abs())
- if ix:isneg() ~= iy:isneg() then
+ local isnumeneg = ix[BINT_SIZE] & BINT_WORDMSB ~= 0
+ local isdenoneg = iy[BINT_SIZE] & BINT_WORDMSB ~= 0
+ if isnumeneg then
+ ix = -ix
+ end
+ if isdenoneg then
+ iy = -iy
+ end
+ local quot, rema = bint.udivmod(ix, iy)
+ if isnumeneg ~= isdenoneg then
  quot:_unm()
  -- round quotient towards minus infinity
  if not rema:iszero() then