Additional arithmetic operations/variants

Hello
i get an type mismatch error when in do

let mut c_post: Array1<f32> = a.c.mapv(|x| x.tanh());
a.h = &a.o_gate * c_post;

Edit: o_gate has the type Array1<f32>

Error

error[E0271]: type mismatch resolving `<f32 as std::ops::Mul<ndarray::ArrayBase<ndarray::OwnedRepr<f32>, ndarray::dimension::dim::Dim<[usize; 1]>>>>::Output == f32`
   --> src/main.rs:188:25
    |
188 |         a.h = &a.o_gate * c_post;
    |                         ^ expected struct `ndarray::ArrayBase`, found f32
    |
    = note: expected type `ndarray::ArrayBase<ndarray::OwnedRepr<f32>, ndarray::dimension::dim::Dim<[usize; 1]>>`
               found type `f32`
    = note: required because of the requirements on the impl of `std::ops::Mul<ndarray::ArrayBase<ndarray::OwnedRepr<f32>, ndarray::dimension::dim::Dim<[usize; 1]>>>` for `&ndarray::ArrayBase<ndarray::OwnedRepr<f32>, ndarray::dimension::dim::Dim<[usize; 1]>>`

error[E0277]: the trait bound `ndarray::ArrayBase<ndarray::OwnedRepr<f32>, ndarray::dimension::dim::Dim<[usize; 1]>>: ndarray::impl_ops::ScalarOperand` is not satisfied
   --> src/main.rs:188:25
    |
188 |         a.h = &a.o_gate * c_post;
    |                         ^ the trait `ndarray::impl_ops::ScalarOperand` is not implemented for `ndarray::ArrayBase<ndarray::OwnedRepr<f32>, ndarray::dimension::dim::Dim<[usize; 1]>>`
    |
    = note: required because of the requirements on the impl of `std::ops::Mul<ndarray::ArrayBase<ndarray::OwnedRepr<f32>, ndarray::dimension::dim::Dim<[usize; 1]>>>` for `&ndarray::ArrayBase<ndarray::OwnedRepr<f32>, ndarray::dimension::dim::Dim<[usize; 1]>>`

i think it tries to do a scalar operation

When i don't try to do it inplace it works

let mut c_post: Array1<f32> = a.c.mapv(|x| x.tanh());
a.h = &a.o_gate * &c_post;

We use inplace operations when concerned about the memory usage right?

To my surprise I also have to write
momentum.bf += &(&gradient.bf * &gradient.bf);
instead of momentum.bf += &gradient.bf * &gradient.bf;
more or less the same error as above (trying to do a scalar operation). All variables are Array1<f32>
Do I lack some understanding of references Rust?

hi, we can look at this if you provide example code for the problem or tell us the types of all the incoming variables

    let a: Array2<f32> = arr2(&[[2.0, 3.0], [4.0, 5.0]]);
    let c: Array2<f32> = arr2(&[[1.0, 0.0], [0.0, 1.0]]);
    let mut d: Array2<f32> = Array2::zeros((2,2));

    d = 2.0 * (&a / c.map(|x| x+1.0)); // &B @ B missing?
    d += b.t().dot(&a); // C @= B missing?
    d += &a * &a; // also C @= B 

    {
        let e = &mut d;
        *e = a.dot(&c); // works
        *e = &a.dot(&c); // why do i need to remove the borrow
        *e = e + a.dot(&a); // &mut B @ B missing?
        *e = a.dot(&a) + e; // B @ &mut B missing?
        *e = e + e; // &mut B @ &mut B missing?
    }

I am not sure if this me not understanding Rust or if there are some variants missing in impl_ops.rs.
In the comment I wrote which implementations might be missing in term os doc.
If you think that I am right I would give the implementation a shot.

Thanks! You're probably right - the ones you ask about as missing are not listed in the docs as being present:

https://docs.rs/ndarray/0.12.1/ndarray/struct.ArrayBase.html#arithmetic-operations

I'm not sure all of these should exist. I know it seems silly to say it like that — but adding one rule might result in dozens of additional impl blocks per rule.

Playground link for your example https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=b5f6f01f0151d31d305a89e657810925

Are you concerned about the amount of code that will get generated?

Yes. Maybe there is a way to simplify it somehow.

@bluss

I do understand the bloat concern @bluss, but the error message you get from the compiler on this issue is particularly confusing compared to the simplicity of the operation you are trying to perform.

I bumped into it myself while I was working on another example for ndarray-examples and it took me a while to figure it out.

I'd be happy to work on this to expand the list of admitted operands combinations if you are willing to merge it/consider to merge it.

@LukeMathWalker

Let's make an issue to discuss this. There are loads of things that can be improved with the arithmetic ops.

@LukeMathWalker Let me know what you think. I've tried to make it specific #699

@LukeMathWalker

@LukeMathWalker I can't promise I have the bandwidth to approve it. We need to merge changes that I haven't approved too, otherwise we'll be stuck here :)

I guess what I meant was "unless you strongly feel against it" 👍 I'll contribute to the discussion in #699

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Additional arithmetic operations/variants #697

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Additional arithmetic operations/variants #697

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matzebond commented on Sep 3, 2019

bluss commented on Sep 4, 2019

matzebond commented on Sep 4, 2019

bluss commented on Sep 4, 2019

matzebond commented on Sep 4, 2019

bluss commented on Sep 4, 2019

LukeMathWalker commented on Sep 8, 2019

bluss commented on Sep 8, 2019

bluss commented on Sep 8, 2019

LukeMathWalker commented on Sep 8, 2019

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