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go/test/divmod.go
Martin Olsson 5499034a71 all: fix a few spelling errors in source comments 
R=golang-codereviews, dave, iant
CC=golang-codereviews
https://golang.org/cl/45750044
2013-12-27 08:59:02 -08:00

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// run
// Copyright 2013 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Test division of variables. Generate many test cases,
// compute correct answer using shift and subtract,
// and then compare against results from division and
// modulus operators.
//
// Primarily useful for testing software div/mod.
package main
const long = false
func main() {
if long {
// About 3e9 test cases (calls to checkdiv3).
// Too long for everyday testing.
gen2(3, 64, 2, 64, checkdiv1)
println(ntest)
} else {
// About 4e6 test cases (calls to checkdiv3).
// Runs for 8 seconds on ARM chromebook, much faster elsewhere.
gen2(2, 64, 1, 64, checkdiv1)
}
}
// generate all uint64 values x where x has at most n bits set in the low w
// and call f(x) for each.
func gen1(n, w int, f func(uint64)) {
gen(0, 0, n, w-1, f)
}
func gen(val uint64, nbits, maxbits, pos int, f func(uint64)) {
if pos < 0 {
f(val)
return
}
gen(val, nbits, maxbits, pos-1, f)
if nbits < maxbits {
gen(val|1<<uint(pos), nbits+1, maxbits, pos-1, f)
}
}
// generate all uint64 values x, y where x has at most n1 bits set in the low w1
// and y has at most n2 bits set in the low w2 and call f(x, y) for each.
func gen2(n1, w1, n2, w2 int, f func(uint64, uint64)) {
gen1(n1, w1, func(x uint64) {
gen1(n2, w2, func(y uint64) {
f(x, y)
})
})
}
// x and y are uint64s with at most 2 bits set.
// Check those values and values above and below,
// along with bitwise inversions of the same (done in checkdiv2).
func checkdiv1(x, y uint64) {
checkdiv2(x, y)
// If the low bit is set in x or y, adding or subtracting 1
// produces a number that checkdiv1 is going to be called
// with anyway, so don't duplicate effort.
if x&1 == 0 {
checkdiv2(x+1, y)
checkdiv2(x-1, y)
}
if y&1 == 0 {
checkdiv2(x, y-1)
checkdiv2(x, y+1)
if x&1 == 0 {
checkdiv2(x+1, y-1)
checkdiv2(x-1, y-1)
checkdiv2(x-1, y+1)
checkdiv2(x+1, y+1)
}
}
}
func checkdiv2(x, y uint64) {
checkdiv3(x, y)
checkdiv3(^x, y)
checkdiv3(x, ^y)
checkdiv3(^x, ^y)
}
var ntest int64 = 0
func checkdiv3(x, y uint64) {
ntest++
if ntest&(ntest-1) == 0 && long {
println(ntest, "...")
}
checkuint64(x, y)
if (uint64(uint32(x)) == x || uint64(uint32(^x)) == ^x) && (uint64(uint32(y)) == y || uint64(uint32(^y)) == ^y) {
checkuint32(uint32(x), uint32(y))
}
if (uint64(uint16(x)) == x || uint64(uint16(^x)) == ^x) && (uint64(uint16(y)) == y || uint64(uint16(^y)) == ^y) {
checkuint16(uint16(x), uint16(y))
}
if (uint64(uint8(x)) == x || uint64(uint8(^x)) == ^x) && (uint64(uint8(y)) == y || uint64(uint8(^y)) == ^y) {
checkuint8(uint8(x), uint8(y))
}
sx := int64(x)
sy := int64(y)
checkint64(sx, sy)
if (int64(int32(sx)) == sx || int64(int32(^sx)) == ^sx) && (int64(int32(sy)) == sy || int64(int32(^sy)) == ^sy) {
checkint32(int32(sx), int32(sy))
}
if (int64(int16(sx)) == sx || int64(int16(^sx)) == ^sx) && (int64(int16(sy)) == sy || int64(int16(^sy)) == ^sy) {
checkint16(int16(sx), int16(sy))
}
if (int64(int8(sx)) == sx || int64(int8(^sx)) == ^sx) && (int64(int8(sy)) == sy || int64(int8(^sy)) == ^sy) {
checkint8(int8(sx), int8(sy))
}
}
// Check result of x/y, x%y for various types.
func checkuint(x, y uint) {
if y == 0 {
divzerouint(x, y)
modzerouint(x, y)
return
}
q, r := udiv(uint64(x), uint64(y))
q1 := x/y
r1 := x%y
if q1 != uint(q) {
print("uint(", x, "/", y, ") = ", q1, ", want ", q, "\n")
}
if r1 != uint(r) {
print("uint(", x, "%", y, ") = ", r1, ", want ", r, "\n")
}
}
func checkuint64(x, y uint64) {
if y == 0 {
divzerouint64(x, y)
modzerouint64(x, y)
return
}
q, r := udiv(x, y)
q1 := x/y
r1 := x%y
if q1 != q {
print("uint64(", x, "/", y, ") = ", q1, ", want ", q, "\n")
}
if r1 != r {
print("uint64(", x, "%", y, ") = ", r1, ", want ", r, "\n")
}
}
func checkuint32(x, y uint32) {
if y == 0 {
divzerouint32(x, y)
modzerouint32(x, y)
return
}
q, r := udiv(uint64(x), uint64(y))
q1 := x/y
r1 := x%y
if q1 != uint32(q) {
print("uint32(", x, "/", y, ") = ", q1, ", want ", q, "\n")
}
if r1 != uint32(r) {
print("uint32(", x, "%", y, ") = ", r1, ", want ", r, "\n")
}
}
func checkuint16(x, y uint16) {
if y == 0 {
divzerouint16(x, y)
modzerouint16(x, y)
return
}
q, r := udiv(uint64(x), uint64(y))
q1 := x/y
r1 := x%y
if q1 != uint16(q) {
print("uint16(", x, "/", y, ") = ", q1, ", want ", q, "\n")
}
if r1 != uint16(r) {
print("uint16(", x, "%", y, ") = ", r1, ", want ", r, "\n")
}
}
func checkuint8(x, y uint8) {
if y == 0 {
divzerouint8(x, y)
modzerouint8(x, y)
return
}
q, r := udiv(uint64(x), uint64(y))
q1 := x/y
r1 := x%y
if q1 != uint8(q) {
print("uint8(", x, "/", y, ") = ", q1, ", want ", q, "\n")
}
if r1 != uint8(r) {
print("uint8(", x, "%", y, ") = ", r1, ", want ", r, "\n")
}
}
func checkint(x, y int) {
if y == 0 {
divzeroint(x, y)
modzeroint(x, y)
return
}
q, r := idiv(int64(x), int64(y))
q1 := x/y
r1 := x%y
if q1 != int(q) {
print("int(", x, "/", y, ") = ", q1, ", want ", q, "\n")
}
if r1 != int(r) {
print("int(", x, "%", y, ") = ", r1, ", want ", r, "\n")
}
}
func checkint64(x, y int64) {
if y == 0 {
divzeroint64(x, y)
modzeroint64(x, y)
return
}
q, r := idiv(x, y)
q1 := x/y
r1 := x%y
if q1 != q {
print("int64(", x, "/", y, ") = ", q1, ", want ", q, "\n")
}
if r1 != r {
print("int64(", x, "%", y, ") = ", r1, ", want ", r, "\n")
}
}
func checkint32(x, y int32) {
if y == 0 {
divzeroint32(x, y)
modzeroint32(x, y)
return
}
q, r := idiv(int64(x), int64(y))
q1 := x/y
r1 := x%y
if q1 != int32(q) {
print("int32(", x, "/", y, ") = ", q1, ", want ", q, "\n")
}
if r1 != int32(r) {
print("int32(", x, "%", y, ") = ", r1, ", want ", r, "\n")
}
}
func checkint16(x, y int16) {
if y == 0 {
divzeroint16(x, y)
modzeroint16(x, y)
return
}
q, r := idiv(int64(x), int64(y))
q1 := x/y
r1 := x%y
if q1 != int16(q) {
print("int16(", x, "/", y, ") = ", q1, ", want ", q, "\n")
}
if r1 != int16(r) {
print("int16(", x, "%", y, ") = ", r1, ", want ", r, "\n")
}
}
func checkint8(x, y int8) {
if y == 0 {
divzeroint8(x, y)
modzeroint8(x, y)
return
}
q, r := idiv(int64(x), int64(y))
q1 := x/y
r1 := x%y
if q1 != int8(q) {
print("int8(", x, "/", y, ") = ", q1, ", want ", q, "\n")
}
if r1 != int8(r) {
print("int8(", x, "%", y, ") = ", r1, ", want ", r, "\n")
}
}
func divzerouint(x, y uint) uint {
defer checkudivzero("uint", uint64(x))
return x / y
}
func divzerouint64(x, y uint64) uint64 {
defer checkudivzero("uint64", uint64(x))
return x / y
}
func divzerouint32(x, y uint32) uint32 {
defer checkudivzero("uint32", uint64(x))
return x / y
}
func divzerouint16(x, y uint16) uint16 {
defer checkudivzero("uint16", uint64(x))
return x / y
}
func divzerouint8(x, y uint8) uint8 {
defer checkudivzero("uint8", uint64(x))
return x / y
}
func checkudivzero(typ string, x uint64) {
if recover() == nil {
print(typ, "(", x, " / 0) did not panic")
}
}
func divzeroint(x, y int) int {
defer checkdivzero("int", int64(x))
return x / y
}
func divzeroint64(x, y int64) int64 {
defer checkdivzero("int64", int64(x))
return x / y
}
func divzeroint32(x, y int32) int32 {
defer checkdivzero("int32", int64(x))
return x / y
}
func divzeroint16(x, y int16) int16 {
defer checkdivzero("int16", int64(x))
return x / y
}
func divzeroint8(x, y int8) int8 {
defer checkdivzero("int8", int64(x))
return x / y
}
func checkdivzero(typ string, x int64) {
if recover() == nil {
print(typ, "(", x, " / 0) did not panic")
}
}
func modzerouint(x, y uint) uint {
defer checkumodzero("uint", uint64(x))
return x % y
}
func modzerouint64(x, y uint64) uint64 {
defer checkumodzero("uint64", uint64(x))
return x % y
}
func modzerouint32(x, y uint32) uint32 {
defer checkumodzero("uint32", uint64(x))
return x % y
}
func modzerouint16(x, y uint16) uint16 {
defer checkumodzero("uint16", uint64(x))
return x % y
}
func modzerouint8(x, y uint8) uint8 {
defer checkumodzero("uint8", uint64(x))
return x % y
}
func checkumodzero(typ string, x uint64) {
if recover() == nil {
print(typ, "(", x, " % 0) did not panic")
}
}
func modzeroint(x, y int) int {
defer checkmodzero("int", int64(x))
return x % y
}
func modzeroint64(x, y int64) int64 {
defer checkmodzero("int64", int64(x))
return x % y
}
func modzeroint32(x, y int32) int32 {
defer checkmodzero("int32", int64(x))
return x % y
}
func modzeroint16(x, y int16) int16 {
defer checkmodzero("int16", int64(x))
return x % y
}
func modzeroint8(x, y int8) int8 {
defer checkmodzero("int8", int64(x))
return x % y
}
func checkmodzero(typ string, x int64) {
if recover() == nil {
print(typ, "(", x, " % 0) did not panic")
}
}
// unsigned divide and mod using shift and subtract.
func udiv(x, y uint64) (q, r uint64) {
sh := 0
for y+y > y && y+y <= x {
sh++
y <<= 1
}
for ; sh >= 0; sh-- {
q <<= 1
if x >= y {
x -= y
q |= 1
}
y >>= 1
}
return q, x
}
// signed divide and mod: do unsigned and adjust signs.
func idiv(x, y int64) (q, r int64) {
// special case for minint / -1 = minint
if x-1 > x && y == -1 {
return x, 0
}
ux := uint64(x)
uy := uint64(y)
if x < 0 {
ux = -ux
}
if y < 0 {
uy = -uy
}
uq, ur := udiv(ux, uy)
q = int64(uq)
r = int64(ur)
if x < 0 {
r = -r
}
if (x < 0) != (y < 0) {
q = -q
}
return q, r
}
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