#6750: [with spkg, needs review] New version of optional Group Cohomology spkg
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Reporter: SimonKing | Owner: SimonKing
Type: enhancement | Status: assigned
Priority: major | Milestone:
Component: optional packages | Keywords: cohomology ring p-group
Reviewer: | Author: Simon King
Merged: |
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Comment(by SimonKing):
I try to summarize how I came to the idea to build libmtx.a twice.
- When I tried higher optimizations, I found out that at least one
executable of David Green (purpose: Computation of a particularly nice
basis of the group algebra) only works when linked against a version of
libmtx.a that was build with at most -O1.
- In order to have higher optimization available (and faster code?) I
separated things, so, I had one libmtx.a for David Green's executables and
another libmtx.a for the rest.
But after looking at my Makefile, I realize that in fact the second
version of libmtx.a is using -O1 as well. I remember that I made
performance tests with different optimizations, and it could be that in
fact -O2 or -O3 does not yield faster code.
Now, I suggest the following approach:
1. I test -O1, -O2, -O3 on sage.math and another machine.
2. Should it turn out that -O1 is the fastest anyway then I build
libmtx.a only once, an I reckon this would solve the problem.
3. If -O2 or -O3 is faster, then I should probably stick with two
versions of libmtx.a. But then I must find a way to work around the
sporadic build problems on a MacBook.
John, I still wonder about the error message in your report. Why can't
libmtx.a be accessed? Is it perhaps the case that the MacBook tries a
parallel build? If this is the case, how can I switch it off?
Cheers,
Simon
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/6750#comment:20>
Sage <http://sagemath.org/>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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