FromScalar makes no sense with mask

[chewxy]

From @chewxy on July 3, 2017 23:12

// FromScalar is a construction option for representing a scalar value as a Tensor
func FromScalar(x interface{}, argMask ...[]bool) ConsOpt {
	var mask []bool
	if len(argMask) > 0 {
		mask = argMask[0]
	}

	f := func(t Tensor) {
		switch tt := t.(type) {
		case *Dense:
			xt := reflect.TypeOf(x)
			xv := reflect.New(xt)
			xvi := reflect.Indirect(xv)
			xvi.Set(reflect.ValueOf(x))
			ptr := xv.Pointer()
			uptr := unsafe.Pointer(ptr)

			tt.ptr = uptr
			tt.l = 1
			tt.c = 1
			tt.v = x
			tt.t = Dtype{xt}
			tt.mask = mask
			tt.shape = 

		default:
			panic("Unsupported Tensor Type")
		}
	}
	return f
}

A scalar value should not be masked. Is there a reason why a scalar value is maskable? @kabaka0

There are various instances where retVal = New(FromScalar(argmaxI(t.Ints(), t.mask))) or something similar is called, but I cannot for rhyme or reason figure out why.

Copied from original issue: gorgonia/gorgonia#132

[chewxy]

From @kabaka0 on July 3, 2017 23:20

My reasoning was that there could be cases in which a scalar is masked, such as, say, a reduction operation from a masked array (say all elements invalid) that results in an invalid scalar. I opted as a result to include the option of creating a scalar with a mask, given that it is not forbidden. I believe that numpy also supports masked 'scalars' (numpy/numpy#4332)

[chewxy]

From @kabaka0 on July 3, 2017 23:26

Also in the case you quote, retVal = New(FromScalar(argmaxI(t.Ints(), t.mask))), the return value is a regular (unmasked) scalar, the mask is only used in argmask. In fact, I should have modified those lines to be something like retVal = New(FromScalar(argmaxI(t.Ints(), t.mask), t.maskedAll())

[chewxy]

OK. Thanks. Very helpful. Can you craft a documentation for this? Thanks

[chewxy]

From @kabaka0 on July 3, 2017 23:35

Sure, I will do!

On Jul 3, 2017 7:34 PM, "Chewxy" notifications@github.com wrote:

Assigned #132 gorgonia/gorgonia#132 to @kabaka0
https://github.com/kabaka0.

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[chewxy]

(btw, just send a PR, I'll merge your documentation before #127