Difficulty Compiling Magma in Fortran

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Re: Difficulty Compiling Magma in Fortran

Postby fletchjp » Wed Jan 05, 2011 5:19 am


Thank you. I think I need to be patient and wait for RC3 for the FORTRAN interfaces. That is not too bad as I am back to the university and have lots of other things to do. I was so frustrated not having any CUDA hardware last autumn that I went and bought my own so it is at home. I did a lot of the work over the holiday. I know a shop in London (Yoyotech) and last time I was down there for a meeting I went to see them and when I saw they had a 2 Gig version of the GTX 460 I bought one and a box to run it on.

I work with a colleague who has some large matrix problems which I help him to run. We currently run the larger ones on ScaLAPACK and Parpack. I am using this work as a pilot to work out how much quicker we could run things if we had some GPUs as well.

I agree with you about single precision speed and I think that for the larger sizes the mixed precision will be the best option for problems where I want to solve Ax=b type problems. See dsgesv results below.

Two thoughts there. For my particular problem, it is more efficient to store the transpose of the matrix because it is generated a row at a time. There is an option to solve the transpose problem when using DGETRF and DGETRS separately, and I see gains with that with GotoBLAS (without GPU). There is not the same option with DGESV and DSGESV. I suspect I could get inside the code and generate a transpose version, but would that be an option which could be added?

Also, in some codes I want to factorise once and then solve several times. What would be needed to use the mixed precision approach to that?

Here are some results. This may be a mix of magma_blas and CUblas.

Code: Select all
fletcher@fletcher-desktop:~/magma_1.0.0-rc2/testing$ ./testing_dsgesv_gpu
device 0: GeForce GTX 460, 1400.0 MHz clock, 2047.2 MB memory

  testing_dsgesv_gpu -nrhs 1 -N 1024

Epsilon(double): 1.110223e-16
Epsilon(single): 5.960464e-08

  N   DP-Factor  DP-Solve  SP-Factor  SP-Solve  MP-Solve  ||b-Ax||/||A||  NumIter
 1024 32.70     26.48     43.38      37.64      11.56     1.565239e-16      3
 2048 48.86     44.12    122.34     119.92      42.16     1.120209e-15      3
 3072 58.57     54.45    176.71     168.60      66.74     1.795437e-16      3
 4032 63.05     59.39    256.07     250.92      78.07     4.456418e-14      4
 5184 66.34     63.62    286.66     282.16     118.01     3.926494e-16      3
 6016 67.78     65.28    299.07     293.68     116.43     1.428188e-14      4
 7040 69.05     66.99    307.25     304.99     147.38     1.091337e-15      3
 8064 70.37     68.50    320.73     316.82     141.02     2.429935e-16      4
 9088 71.22     69.49    327.65     322.49     156.68     8.076463e-15      4
10240 71.50     70.01    331.08     327.58     168.54     1.963176e-14      4

Best wishes

Posts: 175
Joined: Mon Dec 27, 2010 7:29 pm

Re: Difficulty Compiling Magma in Fortran

Postby LINDENSEO3 » Mon Jan 10, 2011 12:24 pm

thank you for the advise.
Posts: 2
Joined: Mon Jan 10, 2011 12:07 pm

Re: Difficulty Compiling Magma in Fortran

Postby LINDENSEO3 » Mon Jan 10, 2011 12:27 pm

thank you for the info
Posts: 2
Joined: Mon Jan 10, 2011 12:07 pm


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