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strconv: fix float_prec := 1.9999999999999999 + 0.0000000000000000005 being 0.5 (fix #16448) (#16495)

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Delyan Angelov 2022-11-21 02:57:51 +02:00 committed by GitHub
parent bffe7bd7ab
commit 6cd1723deb
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2 changed files with 41 additions and 10 deletions
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21
vlib/strconv/atof.c.v
View File

@ -289,7 +289,7 @@ fn converter(mut pn PrepNumber) u64 {
s0 = q0
pn.exponent++
}
// C.printf("mantissa before normalization: %08x%08x%08x binexp: %d \n", s2,s1,s0,binexp)
// C.printf(c"mantissa before normalization: %08x%08x%08x binexp: %d \n", s2,s1,s0,binexp)
// normalization, the 28 bit in s2 must the leftest one in the variable
if s2 != 0 || s1 != 0 || s0 != 0 {
for (s2 & mask28) == 0 {
@ -333,20 +333,20 @@ fn converter(mut pn PrepNumber) u64 {
s0=0x0
*/
// C.printf("mantissa before rounding: %08x%08x%08x binexp: %d \n", s2,s1,s0,binexp)
// C.printf(c"mantissa before rounding: %08x%08x%08x binexp: %d \n", s2,s1,s0,binexp)
// s1 => 0xFFFFFFxx only F are rapresented
nbit := 7
check_round_bit := u32(1) << u32(nbit)
check_round_mask := u32(0xFFFFFFFF) << u32(nbit)
if (s1 & check_round_bit) != 0 {
// C.printf("need round!! cehck mask: %08x\n", s1 & ~check_round_mask )
// C.printf(c"need round!! check mask: %08x\n", s1 & ~check_round_mask )
if (s1 & ~check_round_mask) != 0 {
// C.printf("Add 1!\n")
// C.printf(c"Add 1!\n")
s2, s1, s0 = add96(s2, s1, s0, 0, check_round_bit, 0)
} else {
// C.printf("All 0!\n")
// C.printf(c"All 0!\n")
if (s1 & (check_round_bit << u32(1))) != 0 {
// C.printf("Add 1 form -1 bit control!\n")
// C.printf(c"Add 1 form -1 bit control!\n")
s2, s1, s0 = add96(s2, s1, s0, 0, check_round_bit, 0)
}
}
@ -354,17 +354,18 @@ fn converter(mut pn PrepNumber) u64 {
s0 = u32(0)
// recheck normalization
if s2 & (mask28 << u32(1)) != 0 {
// C.printf("Renormalize!!")
// C.printf(c"Renormalize!!\n")
q2, q1, q0 = lsr96(s2, s1, s0)
binexp--
binexp++
// dump(binexp)
s2 = q2
s1 = q1
s0 = q0
}
}
// tmp := ( u64(s2 & ~mask28) << 24) | ((u64(s1) + u64(128)) >> 8)
// C.printf("mantissa after rounding : %08x%08x%08x binexp: %d \n", s2,s1,s0,binexp)
// C.printf("Tmp result: %016x\n",tmp)
// C.printf(c"mantissa after rounding : %08x %08x %08x binexp: %d \n", s2,s1,s0,binexp)
// C.printf(c"Tmp result: %016x\n",tmp)
// end rounding
// offset the binary exponent IEEE 754
binexp += 1023

30
vlib/strconv/converter_test.v Normal file
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@ -0,0 +1,30 @@
module main
fn test_issue_16448() {
float_prec := 1.9999999999999999 + 0.0000000000000000005
assert float_prec > 1.99
assert float_prec < 2.01
}
// Testing all the numbers between -100E6..100E6 takes over a minute with clang on i3
// while for just -1E5..1E5, it takes less than a second.
// const r = i64(100_000_001)
// const r = i64(17_000_001)
const r = i64(100_001)
fn test_renormalisation_inside_converter() {
for i in -r .. r {
s := '${i}.9999999999999999999'
fs := s.f64()
ifs := i64(fs)
if i % 10000 == 0 {
eprintln('>>> s: ${s:30s} | fs: ${fs:20.6f} | ifs: ${ifs:20}')
}
if i < 0 && ifs != i - 1 {
panic('invalid negative f64 value, i: ${i} | s: ${s} | fs: ${fs} | ifs: ${ifs}')
}
if i > 0 && ifs != i + 1 {
panic('invalid positive f64 value, i: ${i} | s: ${s} | fs: ${fs} | ifs: ${ifs}')
}
}
}