[AMBER-Developers] Problem with Fortran-CUDA interface

From: Yinglong Miao <yinglong.miao.gmail.com>
Date: Fri, 3 Nov 2017 09:35:03 -0500

Hi All,

I run into this problem with the Fortran-CUDA interface. Basically, in the pme_force.F90, I called a function in the cuda/gpu.cpp as shown below. The calculations inside the gpu function run fine, but it seems the potential energies got changed *strangely* in the first place when they are passed for calling the function:

       write(*,'(a,2f22.12)') "Debug-p1) (pot_ene%total, pot_ene%dihedral) = ", &
                       pot_ene%total, pot_ene%dihedral
       call gpu_calculate_and_apply_gamd_weights(pot_ene%total, pot_ene%dihedral, &

extern "C" void gpu_calculate_and_apply_gamd_weights_(double* pot_ene_tot, double* dih_ene_tot,
                                                      double* gamd_ene_tot,
                                                      double* num_gamd_lag)
  double tboost = 0.0;
  double fwgtd = 1.0;
  double fwgt = 1.0;
  double tboostall = 0.0;
  double temp0 = gpu->sim.gamd_temp0;
  double ONE_KB = 1.0 / (temp0 * KB);
  printf("Debug-GPU-p0) (pot_ene_tot, dih_ene_tot) = (%12.5f, %12.5f)\n", *pot_ene_tot, *dih_ene_tot);
Debug-p1) (pot_ene%total, pot_ene%dihedral) = -5991.862400868107 9.501277353615
Debug-GPU-p0) (pot_ene_tot, dih_ene_tot) = ( -5988.16828, 9.89661)

As you can see, the energy values before and after they are passed are different. And this problem appeared to depend on the simulation length. The energy differences are negligible when I test the code with several thousand steps, but get larger with hundreds of thousand steps or more like the above. Has anyone come across similar issues before? My workstation has a new NVIDIA Quadro P5000 GPU card. Could this be related to the hardware? If not, how may I fix it?

Any suggestions will be much appreciated,

Yinglong Miao, Ph.D.
Assistant Professor
Center for Computational Biology and
Department of Molecular Biosciences
University of Kansas

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Received on Fri Nov 03 2017 - 08:00:03 PDT
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