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This is a test issue to see if the GitHub Action to automatically add issues to the project board

Do we use GrB_Info or have LAGr_Info that contains (possibly) a GrB_Info and a much richer set of information.

Is there an LAGr_error() that does analogous tasks to GrB_error() or something completely different.

Base outline/format on GraphBLAS spec.

[18Mar2020] Should LAGraph return a GrB_Matrix that is deferred?

Related question: are the algorithms is composable for which the result of one is passed to another.

Is GraphBLAS execution mode orthogonal to the concerns of LAGraph?

In the 2020-04-22 meeting, property checking levels were discussed. I want to expand on that idea a bit more.

First, let's separate formal properties from informal properties.

Formal properties

• Are part of the struct
• Have multiple enumerated values, including the default Unknown
  • Might be simple: Unknown, True, False
  • Might be more complicated: Unknown, RealValues, NonNegative, StrictlyPositive

Informal properties

• Not part of the graph struct (although could be added in a future release)
• Always have an implied value of Unknown

LAGraph algorithms can indicate required property values (both formal and informal) in their description. Descriptor bits control property checking. There is one descriptor bit for formal properties and a separate one for informal properties.

Formal property checking levels

0. No checking performed. Property values ignored.
1. Raise an error if the property is not satisfied. Unknown is assumed to be a satisfied property.
2. Raise an error if the property is not satisfied or Unknown.
3. If property is Unknown, calculate the property. Raise an error if the property is not satisfied.
4. Recalculate the property. Raise an error if the property is not satisfied.
5. Recalculate the property. Raise an error if the property is not satisfied or if the property changes and was not originally Unknown.

Informal property checking levels

0. No checking performed.
1. Calculate the property. Raise an error if the property is not satisfied.

While all levels are useful in different situations, I think the two most common modes will be Run Fast (formal=0, informal=0) and Check as Needed (formal=3, informal=1).

How should signatures be named and structured.

One consideration, is carrying along property flags that can effect how algorithms are carried out:

GrB_Matrix + property flags --> LAGr_Matrix

Some thoughts on visualizing GraphBLAS operations in presentations.

Masks

Masks -- it might be worth making a distinction between〈M〉and〈¬M〉:

• regular mask: highlight elements which are to be computed with some background color, e.g. light grey
• complement of a mask: cross out matrix elements (×) where the computation should not be performed.

The rationale behind this distinction is that is we would use the same for〈¬M〉, that would often mean highlighting most of the matrix.

Additionally:

• replace mask: It should suggest that the elements outside the mask are deleted. This is often quite obvious visually so maybe just adding a note 'replace' could suffice.

Highlight elements

If using colors is possible, we can use circles with borders.

Lessons learnt

I've used Wingdings to capture circled numbers but it had a few problems:

• Changing from the basic state to a highlighted state is time-consuming as it is a different character.
• For the same reason, animated highlights also do not work.

Using regular numbers in a circle is a better approach.