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bf: add cmp(), join(), slice(), popcount() and hamming()

pull/1110/head
Vitalie Ciubotaru 2019-07-13 03:46:37 +09:00 committed by Alexander Medvednikov
parent 2538a7e752
commit ef899b7c09
2 changed files with 231 additions and 10 deletions
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148
vlib/bf/bf.v
View File

@ -13,7 +13,7 @@ const (
)
fn bitmask(bitnr int) u32 {
return u32(1 << (bitnr % SLOT_SIZE))
return u32(u32(1) << u32(bitnr % SLOT_SIZE))
}
fn bitslot(size int) int {
@ -150,6 +150,53 @@ pub fn bfxor(input1 BitField, input2 BitField) BitField {
return output
}
pub fn join(input1 BitField, input2 BitField) BitField {
output_size := input1.size + input2.size
mut output := new(output_size)
// copy the first input to output as is
for i := 0; i < bitnslots(input1.size); i++ {
output.field[i] = input1.field[i]
}
// find offset bit and offset slot
offset_bit := input1.size % SLOT_SIZE
offset_slot := input1.size / SLOT_SIZE
for i := 0; i < bitnslots(input2.size); i++ {
output.field[i + offset_slot] =
output.field[i + offset_slot] |
u32(input2.field[i] << u32(offset_bit))
}
/*
* If offset_bit is not zero, additional operations are needed.
* Number of iterations depends on the nr of slots in output. Two
* options:
* (a) nr of slots in output is the sum of inputs' slots. In this
* case, the nr of bits in the last slot of output is less than the
* nr of bits in second input (i.e. ), OR
* (b) nr of slots of output is the sum of inputs' slots less one
* (i.e. less iterations needed). In this case, the nr of bits in
* the last slot of output is greater than the nr of bits in second
* input.
* If offset_bit is zero, no additional copies needed.
*/
if (output_size - 1) % SLOT_SIZE < (input2.size - 1) % SLOT_SIZE {
for i := 0; i < bitnslots(input2.size); i++ {
output.field[i + offset_slot + 1] =
output.field[i + offset_slot + 1] |
u32(input2.field[i] >> u32(SLOT_SIZE - offset_bit))
}
} else if (output_size - 1) % SLOT_SIZE > (input2.size - 1) % SLOT_SIZE {
for i := 0; i < bitnslots(input2.size) - 1; i++ {
output.field[i + offset_slot + 1] =
output.field[i + offset_slot + 1] |
u32(input2.field[i] >> u32(SLOT_SIZE - offset_bit))
}
}
return output
}
pub fn print(instance BitField) {
mut i := 0
for i < instance.size {
@ -178,3 +225,102 @@ pub fn clone(input BitField) BitField {
return output
}
pub fn cmp(input1 BitField, input2 BitField) bool {
if input1.size != input2.size {return false}
for i := 0; i < bitnslots(input1.size); i++ {
if input1.field[i] != input2.field[i] {return false}
}
return true
}
pub fn (instance BitField) popcount() int {
size := instance.size
bitnslots := bitnslots(size)
tail := size % SLOT_SIZE
mut count := 0
for i := 0; i < bitnslots - 1; i++ {
for j := 0; j < SLOT_SIZE; j++ {
if u32(instance.field[i] >> u32(j)) & u32(1) == u32(1) {
count++
}
}
}
for j := 0; j < tail; j++ {
if u32(instance.field[bitnslots - 1] >> u32(j)) & u32(1) == u32(1) {
count++
}
}
return count
}
pub fn hamming (input1 BitField, input2 BitField) int {
input_xored := bfxor(input1, input2)
return input_xored.popcount()
}
pub fn (input BitField) slice(_start int, _end int) BitField {
// boundary checks
mut start := _start
mut end := _end
if end > input.size {
end = input.size // or panic?
}
if start > end {
start = end // or panic?
}
mut output := new(end - start)
start_offset := start % SLOT_SIZE
end_offset := (end - 1) % SLOT_SIZE
start_slot := start / SLOT_SIZE
end_slot := (end - 1) / SLOT_SIZE
output_slots := bitnslots(end - start)
if output_slots > 1 {
if start_offset != 0 {
for i := 0; i < output_slots - 1; i++ {
output.field[i] =
u32(input.field[start_slot + i] >> u32(start_offset))
output.field[i] = output.field[i] |
u32(input.field[start_slot + i + 1] <<
u32(SLOT_SIZE - start_offset))
}
}
else {
for i := 0; i < output_slots - 1; i++ {
output.field[i] =
u32(input.field[start_slot + i])
}
}
}
if start_offset > end_offset {
output.field[(end - start - 1) / SLOT_SIZE] =
u32(input.field[end_slot - 1] >> u32(start_offset))
mut mask := u32((1 << (end_offset + 1)) - 1)
mask = input.field[end_slot] & mask
mask = u32(mask << u32(SLOT_SIZE - start_offset))
output.field[(end - start - 1) / SLOT_SIZE] =
output.field[(end - start - 1) / SLOT_SIZE] | mask
}
else if start_offset == 0 {
mut mask := u32(0)
if end_offset == SLOT_SIZE - 1 {
mask = u32(-1)
}
else {
mask = u32(u32(1) << u32(end_offset + 1))
mask = mask - u32(1)
}
output.field[(end - start - 1) / SLOT_SIZE] =
(input.field[end_slot] & mask)
}
else {
mut mask := u32(((1 << (end_offset - start_offset + 1)) - 1) << start_offset)
mask = input.field[end_slot] & mask
mask = u32(mask >> u32(start_offset))
output.field[(end - start - 1) / SLOT_SIZE] =
output.field[(end - start - 1) / SLOT_SIZE] | mask
}
return output
}

93
vlib/bf/bf_test.v
View File

@ -3,18 +3,18 @@ import bf
import rand
fn test_bf_new_size() {
instance := bf.new(5)
assert instance.getsize() == 5
instance := bf.new(75)
assert instance.getsize() == 75
}
fn test_bf_set_clear_toggle_get() {
mut instance := bf.new(5)
instance.setbit(4)
assert instance.getbit(4) == 1
instance.clearbit(4)
assert instance.getbit(4) == 0
instance.togglebit(4)
assert instance.getbit(4) == 1
mut instance := bf.new(75)
instance.setbit(47)
assert instance.getbit(47) == 1
instance.clearbit(47)
assert instance.getbit(47) == 0
instance.togglebit(47)
assert instance.getbit(47) == 1
}
fn test_bf_and_not_or_xor() {
@ -43,3 +43,78 @@ fn test_bf_and_not_or_xor() {
}
assert result == 1
}
fn test_clone_cmp() {
rand.seed()
len := 80
mut input := bf.new(len)
for i := 0; i < len; i++ {
if rand.next(2) == 1 {
input.setbit(i)
}
}
output := bf.clone(input)
assert output.getsize() == len
assert bf.cmp(input, output) == true
}
fn test_slice_join() {
rand.seed()
len := 80
mut input := bf.new(len)
for i := 0; i < len; i++ {
if rand.next(2) == 1 {
input.setbit(i)
}
}
mut result := 1
for point := 1; point < (len - 1); point++ {
// divide a bitfield into two subfields
chunk1 := input.slice(0, point)
chunk2 := input.slice(point, input.getsize())
// concatenate them back into one and compare to the original
output := bf.join(chunk1, chunk2)
if !bf.cmp(input, output) {
result = 0
}
}
assert result == 1
}
fn test_popcount() {
rand.seed()
len := 80
mut count0 := 0
mut input := bf.new(len)
for i := 0; i < len; i++ {
if rand.next(2) == 1 {
input.setbit(i)
count0++
}
}
count1 := input.popcount()
assert count0 == count1
}
fn test_hamming() {
rand.seed()
len := 80
mut count := 0
mut input1 := bf.new(len)
mut input2 := bf.new(len)
for i := 0; i < len; i++ {
switch rand.next(4) {
case 0:
case 1:
input1.setbit(i)
count++
case 2:
input2.setbit(i)
count++
case 3:
input1.setbit(i)
input2.setbit(i)
}
}
assert count == bf.hamming(input1, input2)
}