Bug 632

Matching bug on Rust's std::simd bugtracker:
https://github.com/rust-lang/stdsimd/issues/109

provisionally assigning EUR 2000, to be adjusted as needed.

(In reply to Jacob Lifshay from comment #2)
> provisionally assigning EUR 2000, to be adjusted as needed.

be very careful about assigning funds: there is only around EUR 2500
left from the NLnet 2019 or it might actually be over-budget.
we *may* be able to receive some funds from NLnet if they have
spare, however it is not guaranteed.

very quick hack to get the total payments issued per top-level milestone
https://git.libre-soc.org/?p=utils.git;a=commitdiff;h=df61adb514d7e33819e3672eebf6fde279118d2c

Milestone(identifier='NLnet.2019.02', canonical_bug_id=191)

     27525


we're good.  it's a lot less than i thought.  at least 22,000 available.

ah.  just a reminder, jacob: we cannot deviate from the original
(agreed) Memorandum of Understanding.  we simply cannot arbitrarily
"add new tasks".

however, if during the course of implementing one such pre-agreed task,
a library happens to be needed which does not exist, then yes,
that's perfectly fine.

(In reply to Luke Kenneth Casson Leighton from comment #5)
> ah.  just a reminder, jacob: we cannot deviate from the original
> (agreed) Memorandum of Understanding.  we simply cannot arbitrarily
> "add new tasks".
> 
> however, if during the course of implementing one such pre-agreed task,
> a library happens to be needed which does not exist, then yes,
> that's perfectly fine.

Yup! We'd need this library because a SimpleV-capable math library doesn't exist, we need to build one. We can share the implementation costs with Rust's std::simd (which also wants a vector math library without libc, libm, or OS dependencies for use in Rust's `core` library). In particular, this means the math library will have generic vector-length-independent implementations written in Rust.

Started an implementation at https://salsa.debian.org/Kazan-team/vector-math

From https://github.com/rust-lang/stdsimd/issues/109#issuecomment-831196244
Got all the vector traits wired up for use with scalars (where all vectors are length 1 for testing purposes or otherwise) and with generating demo compiler IR. Still need to wire up `std::simd` support.

https://salsa.debian.org/Kazan-team/vector-math/-/blob/7975aa9639f3a5a702b130a7cf992ffe71c86e2a/src/ir.rs#L1547
The following Rust:
```rust
fn f<Ctx: Context>(ctx: Ctx, a: Ctx::VecU8, b: Ctx::VecF32) -> Ctx::VecF64 {
    let a: Ctx::VecF32 = a.into();
    (a - (a + b - ctx.make(5f32)).floor()).to()
}
```
(the `to()` function is a replacement for the `as` keyword)

Generates the following demo IR:
```
function(in<arg_0>: vec<U8>, in<arg_1>: vec<F32>) -> vec<F64> {
    op_0: vec<F32> = Cast in<arg_0>
    op_1: vec<F32> = Add op_0, in<arg_1>
    op_2: vec<F32> = Sub op_1, splat(0x40A00000_f32)
    op_3: vec<F32> = Floor op_2
    op_4: vec<F32> = Sub op_0, op_3
    op_5: vec<F64> = Cast op_4
    Return op_5
}
```

Opinions on ease of use for writing functions like `f`?

From https://github.com/rust-lang/stdsimd/issues/109#issuecomment-832573074
I added bindings for std::simd:
https://salsa.debian.org/Kazan-team/vector-math/-/commit/d77893b257c86d7ddc81f3772b5e143ce768d291
Looking at the assembly generated for stdsimd::tests::do_ilogb_f32x4, it looks pretty reasonable, everything's inlined, however there is still some branching that llvm didn't optimize out:
<snip>
Compiled using:

cargo rustc --release --tests --features=ir,fma,stdsimd -- --emit=asm -C target-cpu=native
on a Ryzen 3900X on Ubuntu

From https://github.com/rust-lang/stdsimd/issues/109#issuecomment-836310527
I added implementations of `sin_pi` and `cos_pi` for `f16` and `f32`, I tested all possible inputs, the functions are accurate to 2ULP though aren't guaranteed to give the correct sign for zeros.

Testing the `f32` functions required writing a custom reference implementation of `sin_cos_pi` since `(x * f64::consts::PI).sin_cos()` isn't accurate enough when the exact mathematical value of either `sin` or `cos` is close to zero (e.g. `sin_pi(1.0) == 0.0` but `f64::consts::PI.sin() != 0.0` due to round-off error).

https://salsa.debian.org/Kazan-team/vector-math/-/blob/d79f43bed2398cbc4f6b75b8e55ee317289599a1/src/algorithms/trig_pi.rs#L180

Added implementations for sin_pi/cos_pi/sin_cos_pi_f16/f32/f64

I added sin_pi and cos_pi for f64, as well as adding abs, copy_sign, and trunc for all of f16/f32/f64.

(In reply to Jacob Lifshay from comment #8)

> https://salsa.debian.org/Kazan-team/vector-math/-/blob/
> 7975aa9639f3a5a702b130a7cf992ffe71c86e2a/src/ir.rs#L1547

remember always always always request / create a git.libre-soc.org
repository.

done now
https://git.libre-soc.org/?p=vector-math.git;a=summary

(In reply to Luke Kenneth Casson Leighton from comment #13)
> remember always always always request / create a git.libre-soc.org
> repository.
> 
> done now
> https://git.libre-soc.org/?p=vector-math.git;a=summary

I'll manually keep that up to date (setting up mirroring is a pain), but, since vector-math is part of Kazan, the canonical repo location is https://salsa.debian.org/Kazan-team/vector-math

I added round_to_nearest_ties_to_even, ceil, floor, and tan_pi

Added count_leading_zeros, count_trailing_zeros, and count_ones