Proper initialisation for the optional MeatAxe library

[simon-king-jena]

Modules using the optional MeatAxe package need the following initialisation:

• MeatAxe executables rely on an environment variable declaring where to find multiplication tables. Of course, this needs to be done only once.
• Each module that links against the MeatAxe library, which is a static library, has to define a certain C variable, which serves the same purpose as the aforementioned environment variable.

I suggest to add here a function that does the initialisation and must be called be each module using MeatAxe functions. For that purpose, a new module sage.libs.meataxe is created.

Depends on #23411
Depends on #23352

Component: packages: optional

Keywords: MeatAxe, matrix backend

Author: Simon King

Branch/Commit: 3401f04

Reviewer: Jeroen Demeyer

Issue created by migration from https://trac.sagemath.org/ticket/21437

[simon-king-jena]

Branch: u/SimonKing/fix-mtx-matrices

[simon-king-jena]

New commits:

9e0f5d4	Fix reading mtx-matrix from non-existent file
778df7d	Help using MeatAxe executables in Sage
02fa8a2	Make pickling machine independent
e861781	Add c(p)def functions to get/set horizontal matrix slices

[simon-king-jena]

Author: Simon King

[simon-king-jena]

Commit: e861781

[simon-king-jena]

Changed keywords from none to MeatAxe, matrix backend

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

4f3d56c

Fix index check in get_slice

[sagetrac-git]

Changed commit from e861781 to 4f3d56c

[videlec]

comment:4

I guess you forgot some # optional in the doctests

**********************************************************************
File "src/sage/matrix/matrix_gfpn_dense.pyx", line 657, in sage.matrix.matrix_gfpn_dense.Matrix_gfpn_dense.get_slice
Failed example:
    from sage.matrix.matrix_gfpn_dense import Matrix_gfpn_dense as MTX
Exception raised:
    Traceback (most recent call last):
    ...
    ImportError: No module named matrix_gfpn_dense
**********************************************************************

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

a4dded9

Make new tests optional

[sagetrac-git]

Changed commit from 4f3d56c to a4dded9

[simon-king-jena]

comment:6

Replying to @videlec:

I guess you forgot some # optional in the doctests

Done!

[simon-king-jena]

comment:7

The patchbot reports a timout. Is that reproducible?

Also, according to the coverage plugin, it seems that one function lacks testing.

And I found that the function FfTrueRowSize is uselessly called in a couple of places: It always holds true that FfCurrentRowSizeIo == FfTrueRowSize(FfNoc), where FfCurrentRowSizeIo and FfNoc are both some global variables. Nevertheless, there are calls to FfTrueRowSize(FfNoc) in various places. When profiling my cohomology computations, a measurable amount of time was spent on FfTrueRowSize; therefore I want to create another patch.

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

e17e4df	Document and test _rowlist_()
291f4dc	Some minor tweaks for performance

[sagetrac-git]

Changed commit from a4dded9 to 291f4dc

[videlec]

comment:10

There are strange doctest errors on arando. Could you have a look?

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

03ce5c0

Fix bad INPUT::/OUTPUT:: blocks

[sagetrac-git]

Changed commit from 291f4dc to 03ce5c0

[simon-king-jena]

comment:12

I have pushed another commit, since I made a typo in doc formatting.

Replying to @videlec:

There are strange doctest errors on arando. Could you have a look?

Maybe it isn't strange after all. It is about a random test. The values I provide in the test are what I get when I start a fresh Sage session, but probably I forgot that the random seed in doctests is different.

So, easy to fix...

[simon-king-jena]

comment:118

Replying to @jdemeyer:

Replying to @simon-king-jena:

In any case, can you tell me precisely what the line should be replaced with, so that it works both in Python2 and Python3?

It's not so easy, see [comment:114]

If I understand correctly, it currently has to stay as it is and needs to be addressed as soon as Sage really moves on.

So, for now, I will change the code only according to your other objections.

[simon-king-jena]

Changed branch from u/jdemeyer/fix-mtx-matrices to u/SimonKing/fix-mtx-matrices

[simon-king-jena]

comment:120

Replying to @simon-king-jena:

If I understand correctly, it currently has to stay as it is and needs to be addressed as soon as Sage really moves on.

So, for now, I will change the code only according to your other objections.

Done. Why did sage -git trac push not change the commit field but only the branch field? I changed the commit field manually.

[simon-king-jena]

Changed commit from 656dc9c to 063ad71

[embray]

comment:121

Replying to @jdemeyer:

Replying to @embray:

Let me think about this for a sec. While it's true there are many issues like this in Sage, if we're aware of one now it would be better to address it now rather than make people working on the Python 3 port (i.e. Frédéric) pull their hair out later.

Right, but we might want to consider implementing/using a general solution to the problem of converting filenames (or strings in general) from unicode to bytes. Something along the lines of https://github.com/defeo/cypari2/blob/master/cypari2/string_utils.pyx

I see. I didn't realize that wasn't already the case. Is there any reason these have to be written in Cython? I don't see functions like these getting much speedup from it. In any case , maybe I can just copy these directly into Sage and sprinkle them around the appropriate places.

[jdemeyer]

comment:122

Replying to @embray:

I don't see functions like these getting much speedup from it.

You do get the speedup from calling those functions (calling a cdef function vs. calling a Python function).

And for cypari2, Cython was an obvious choice since cypari2 is completely implemented in Cython.

[jdemeyer]

comment:123

Replying to @simon-king-jena:

Why did sage -git trac push not change the commit field but only the branch field? I changed the commit field manually.

Known bug: sagemath/sage_trac_plugin#10

[jdemeyer]

comment:124

[comment:85]

[jdemeyer]

Reviewer: Jeroen Demeyer

[jdemeyer]

comment:125

Also: please merge 8.1.beta4

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

900b33c	Merge branch 'develop' into t/21437/fix-mtx-matrices
f6bb5bd	Fix wrong comment: libmeataxe is static

[sagetrac-git]

Changed commit from 063ad71 to f6bb5bd

[simon-king-jena]

comment:127

Done, so "needs review", with the caveat that I didn't run tests again.

[jdemeyer]

comment:128

One detail:

    ## Define an environment variable that enables MeatAxe to find
    ## its multiplication tables.

It's not an environment variable, it's a string inside the meataxe library.

If you fix this comment, you can set this ticket to positive review.

[sagetrac-git]

Changed commit from f6bb5bd to 3401f04

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

3401f04

Fix misleading comment on a global MeatAxe variable

[simon-king-jena]

comment:130

Thank you! I hope the comment is fine now.

[vbraun]

Changed branch from u/SimonKing/fix-mtx-matrices to 3401f04