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Speed improvement 32 vs 64 bit
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Joined: 21 Feb 2005
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Location: Salford, UK

PostPosted: Fri Aug 09, 2019 5:47 pm    Post subject: Reply with quote

OK thanks. Either way the results are not for FTN95 64 bit optimised code.
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Joined: 30 Jul 2013
Posts: 1520
Location: Aerospace Valley

PostPosted: Sat Aug 10, 2019 9:52 pm    Post subject: Reply with quote

So, in summary, even though the results in the Polyhedron table my not be optimised, mecej4 results show that it's unlikely that they would start t approach those of th other compilers.

Ths key question seems to be, 'what do the other compilers do to speed up their compilers ?'

The yseem to have several options applied rather than just /OPT of ftn95.

I'm sure /OPT inclusėdes wėseveral techniques for speed-up but Sf need to aanalyse fėmore in depth what the others do in order to play catch-up with any real intent.

The obvious starting point is to obtin copies of all the other compilers, run all WITH NO optimization options first (the starting point) then add one at a time to see the effects.

To Build a bigger picture.
''Computers (HAL and MARVIN excepted) are incredibly rigid. They question nothing. Especially input data.Human beings are incredibly trusting of computers and don't check input data. Together cocking up even the simplest calculation ... Smile "
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Joined: 31 Oct 2006
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PostPosted: Sun Aug 11, 2019 2:05 pm    Post subject: Reply with quote

Jcherw: You may find this older thread relevant to your question regarding the performance of linear equation solvers.

In that thread, John Campbell, DanRRight and I ran tests on the performance of MKL, Pardiso and Laipe linear equation solvers during 2015 - 2017. Most of the posts in that thread predate the emergence of 64-bit FTN95, but whether the tests were run using 32-bit or 64-bit CPUs was not a major issue. Parallelism, FPU instuction sets and the ability to exploit matrix sparsity and structure were found to affect performance.
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Joined: 16 Feb 2006
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Location: Sydney

PostPosted: Sun Aug 18, 2019 5:21 am    Post subject: Reply with quote


You refer to an interesting thread. I should try to update this thread for using ftn95/64 and SSE/AVX instruction set routines. As a single thread solution, the approach of a "cache blocked' single thread solver should show significant improvement, due to being able to use these instructions in an efficient way.

Most of my applications are now running as 64-bit, although large memory solvers are not necessarily a faster solution, as they can be applied as a lazy cache inefficient approach.

As you note, the choice of linear equation solver approach will always be based on which one best exploits the matrix sparsity. These are available in both 32-bit or 64-bit.

A lot of the advantage expected from converting to 64-bit applications has been mitigated by simply using a 64-bit O/S with improved disk buffering.

The key advantages in moving to FTN95 /64 are availability of SIMD instructions and coding simplicity with larger arrays, providing it is not done in a cache lazy way. The old virtual memory coding approaches of the 70's are still very useful for /64.
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