move conversions into a file
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2737974c8f
commit
9e23ce05a9
126
src/conv.rs
Normal file
126
src/conv.rs
Normal file
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@ -0,0 +1,126 @@
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use super::*;
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impl From<u8> for F8 {
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fn from(v: u8) -> Self {
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if v == 0 {
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return Self(0);
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}
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let e = v.ilog2() as u8;
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let off = e as i8 - M_BITS as i8;
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let m = if off >= 0 { v >> off } else { v << -off };
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if e > E_MAX {
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return Self(0xff);
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}
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Self::merge(m & M_STORAGE_MAX, e + E_BIAS)
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}
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}
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impl From<F8> for u8 {
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fn from(value: F8) -> Self {
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if value.0 == 0 {
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return 0;
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}
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let (m, e) = value.split_unbias();
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match e {
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0.. => m << e,
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-7..0 => m >> -e,
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..-7 => 0,
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}
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}
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}
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impl From<F8> for f32 {
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fn from(value: F8) -> Self {
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if value.0 == 0 {
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return 0.0;
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}
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let (m, e) = value.split_unbias();
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(m as f32) * (e as f32).exp2()
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}
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}
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impl F8 {
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/// Split self into the mantissa and exponent, as stored.
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pub(crate) fn split(self) -> (u8, u8) {
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(self.0 & M_MASK, self.0 >> M_BITS)
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}
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/// Split self into integers (m, e) such that `self == m * 2.pow(e)`.
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pub(crate) fn split_unbias(self) -> (u8, i8) {
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let (m, e) = self.split();
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(m | M_BIAS, e as i8 - (E_BIAS + M_BITS) as i8)
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}
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pub(crate) fn merge(m: u8, e: u8) -> Self {
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assert!(m <= M_STORAGE_MAX);
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assert!(e <= E_STORAGE_MAX);
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Self((e << M_BITS) | m)
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}
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pub(crate) fn merge_unbias(in_m: u32, in_e: i32) -> Self {
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if in_m == 0 {
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return Self(0);
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}
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let base_e = in_m.ilog2() as u8;
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let off = base_e as i8 - M_BITS as i8;
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let m = if off >= 0 { in_m >> off } else { in_m << -off };
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let e = (base_e as i32) + in_e + (E_BIAS as i32);
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if e < 0 {
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return Self(0);
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}
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if e > E_STORAGE_MAX as i32 {
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return Self(0xff);
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}
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Self::merge(m as u8 & M_STORAGE_MAX, e as u8)
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}
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn test_int_conv() {
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assert_eq!(u8::from(F8(0)), 0);
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assert_eq!(u8::from(F8::merge(0, 1)), 0);
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assert_eq!(u8::from(F8::merge(0, E_BIAS - 1)), 0);
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assert_eq!(u8::from(F8::merge(0, E_BIAS)), 1);
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assert_eq!(u8::from(F8::merge(0, E_BIAS + 1)), 2);
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assert_eq!(u8::from(F8::merge(0, E_STORAGE_MAX)), 1 << E_MAX);
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for k in 0..=EXACT_INT_MAX {
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assert_eq!(u8::from(F8::from(k)), k);
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}
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}
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#[test]
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fn test_float_conv() {
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assert_eq!(f32::from(F8(0)), 0.0);
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assert_eq!(f32::from(F8::merge(0, E_BIAS)), 1.0);
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assert_eq!(f32::from(F8::merge(0, E_BIAS - 1)), 0.5);
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assert_eq!(f32::from(F8::merge(0, E_BIAS + 1)), 2.0);
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assert_eq!(f32::from(F8::merge(1 << (M_BITS - 1), E_BIAS)), 1.5);
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assert_eq!(f32::from(F8::merge(1 << (M_BITS - 1), E_BIAS - 1)), 0.75);
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assert_eq!(
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f32::from(F8::merge(0, E_STORAGE_MAX)),
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(E_MAX as f32).exp2()
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);
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for k in 0..=EXACT_INT_MAX {
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assert_eq!(f32::from(F8::from(k)), k as f32);
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}
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}
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#[test]
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fn test_merge() {
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assert_eq!(f32::from(F8::merge_unbias(0, 0)), 0.0);
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assert_eq!(f32::from(F8::merge_unbias(1, 0)), 1.0);
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assert_eq!(f32::from(F8::merge_unbias(1, 1)), 2.0);
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assert_eq!(f32::from(F8::merge_unbias(1, -1)), 0.5);
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assert_eq!(f32::from(F8::merge_unbias(3, 0)), 3.0);
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assert_eq!(f32::from(F8::merge_unbias(3, 1)), 6.0);
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assert_eq!(f32::from(F8::merge_unbias(3, -1)), 1.5);
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assert_eq!(
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f32::from(F8::merge_unbias(EXACT_INT_MAX.into(), 0)),
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EXACT_INT_MAX as f32
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);
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}
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}
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121
src/lib.rs
121
src/lib.rs
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@ -1,3 +1,4 @@
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mod conv;
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mod ops;
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pub const M_BITS: u8 = 5;
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@ -23,42 +24,6 @@ const E_MASK: u8 = E_STORAGE_MAX << M_BITS;
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#[repr(transparent)]
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pub struct F8(u8);
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impl F8 {
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/// Split self into the mantissa and exponent, as stored.
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fn split(self) -> (u8, u8) {
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(self.0 & M_MASK, self.0 >> M_BITS)
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}
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/// Split self into integers (m, e) such that `self == m * 2.pow(e)`.
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fn split_unbias(self) -> (u8, i8) {
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let (m, e) = self.split();
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(m | M_BIAS, e as i8 - (E_BIAS + M_BITS) as i8)
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}
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fn merge(m: u8, e: u8) -> Self {
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assert!(m <= M_STORAGE_MAX);
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assert!(e <= E_STORAGE_MAX);
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Self((e << M_BITS) | m)
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}
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fn merge_unbias(in_m: u32, in_e: i32) -> Self {
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if in_m == 0 {
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return Self(0);
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}
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let base_e = in_m.ilog2() as u8;
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let off = base_e as i8 - M_BITS as i8;
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let m = if off >= 0 { in_m >> off } else { in_m << -off };
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let e = (base_e as i32) + in_e + (E_BIAS as i32);
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if e < 0 {
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return Self(0);
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}
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if e > E_STORAGE_MAX as i32 {
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return Self(0xff);
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}
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Self::merge(m as u8 & M_STORAGE_MAX, e as u8)
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}
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}
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impl std::fmt::Binary for F8 {
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fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
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if f.alternate() {
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@ -80,94 +45,10 @@ impl std::fmt::Debug for F8 {
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}
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}
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impl From<u8> for F8 {
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fn from(v: u8) -> Self {
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if v == 0 {
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return Self(0);
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}
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let e = v.ilog2() as u8;
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let off = e as i8 - M_BITS as i8;
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let m = if off >= 0 { v >> off } else { v << -off };
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if e > E_MAX {
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return Self(0xff);
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}
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Self::merge(m & M_STORAGE_MAX, e + E_BIAS)
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}
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}
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impl From<F8> for u8 {
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fn from(value: F8) -> Self {
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if value.0 == 0 {
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return 0;
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}
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let (m, e) = value.split_unbias();
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match e {
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0.. => m << e,
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-7..0 => m >> -e,
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..-7 => 0,
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}
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}
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}
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impl From<F8> for f32 {
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fn from(value: F8) -> Self {
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if value.0 == 0 {
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return 0.0;
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}
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let (m, e) = value.split_unbias();
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(m as f32) * (e as f32).exp2()
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}
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn test_int_conv() {
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assert_eq!(u8::from(F8(0)), 0);
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assert_eq!(u8::from(F8::merge(0, 1)), 0);
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assert_eq!(u8::from(F8::merge(0, E_BIAS - 1)), 0);
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assert_eq!(u8::from(F8::merge(0, E_BIAS)), 1);
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assert_eq!(u8::from(F8::merge(0, E_BIAS + 1)), 2);
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assert_eq!(u8::from(F8::merge(0, E_STORAGE_MAX)), 1 << E_MAX);
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for k in 0..=EXACT_INT_MAX {
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assert_eq!(u8::from(F8::from(k)), k);
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}
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}
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#[test]
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fn test_float_conv() {
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assert_eq!(f32::from(F8(0)), 0.0);
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assert_eq!(f32::from(F8::merge(0, E_BIAS)), 1.0);
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assert_eq!(f32::from(F8::merge(0, E_BIAS - 1)), 0.5);
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assert_eq!(f32::from(F8::merge(0, E_BIAS + 1)), 2.0);
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assert_eq!(f32::from(F8::merge(1 << (M_BITS - 1), E_BIAS)), 1.5);
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assert_eq!(f32::from(F8::merge(1 << (M_BITS - 1), E_BIAS - 1)), 0.75);
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assert_eq!(
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f32::from(F8::merge(0, E_STORAGE_MAX)),
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(E_MAX as f32).exp2()
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);
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for k in 0..=EXACT_INT_MAX {
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assert_eq!(f32::from(F8::from(k)), k as f32);
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}
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}
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#[test]
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fn test_merge() {
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assert_eq!(f32::from(F8::merge_unbias(0, 0)), 0.0);
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assert_eq!(f32::from(F8::merge_unbias(1, 0)), 1.0);
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assert_eq!(f32::from(F8::merge_unbias(1, 1)), 2.0);
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assert_eq!(f32::from(F8::merge_unbias(1, -1)), 0.5);
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assert_eq!(f32::from(F8::merge_unbias(3, 0)), 3.0);
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assert_eq!(f32::from(F8::merge_unbias(3, 1)), 6.0);
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assert_eq!(f32::from(F8::merge_unbias(3, -1)), 1.5);
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assert_eq!(
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f32::from(F8::merge_unbias(EXACT_INT_MAX.into(), 0)),
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EXACT_INT_MAX as f32
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);
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}
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#[test]
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fn test_display() {
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fn fmt_split(m: u8, e: u8) -> String {
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