Reduced memory use for PME.

platforms/cuda/src/kernels/cudatypes.h

@@ -367,8 +367,6 @@ struct cudaGmxSimulation {
     float*          pPmeBsplineModuli[3];
     float4*         pPmeBsplineTheta;
     float4*         pPmeBsplineDtheta;
-    int4*           pPmeParticleIndex;              // The grid indices for each atom
-    float4*         pPmeParticleFraction;           // Fractional offset in the grid for each atom in all three dimensions.
     int*            pPmeAtomRange;                  // The range of sorted atoms at each grid point
     float2*         pPmeAtomGridIndex;              // The grid point each atom is at
     unsigned int    bonds;                          // Number of bonds

platforms/cuda/src/kernels/gpu.cpp

@@ -795,10 +795,6 @@ void gpuSetPMEParameters(gpuContext gpu, float alpha, int gridSizeX, int gridSiz
     gpu->sim.pPmeBsplineTheta = gpu->psPmeBsplineTheta->_pDevData;
     gpu->psPmeBsplineDtheta = new CUDAStream<float4>(PME_ORDER*gpu->natoms, 1, "PmeBsplineDtheta");
     gpu->sim.pPmeBsplineDtheta = gpu->psPmeBsplineDtheta->_pDevData;
-    gpu->psPmeParticleIndex = new CUDAStream<int4>(gpu->natoms, 1, "PmeParticleIndex");
-    gpu->sim.pPmeParticleIndex = gpu->psPmeParticleIndex->_pDevData;
-    gpu->psPmeParticleFraction = new CUDAStream<float4>(gpu->natoms, 1, "PmeParticleFraction");
-    gpu->sim.pPmeParticleFraction = gpu->psPmeParticleFraction->_pDevData;
     gpu->psPmeAtomRange = new CUDAStream<int>(gridSize.x*gridSize.y*gridSize.z+1, 1, "PmeAtomRange");
     gpu->sim.pPmeAtomRange = gpu->psPmeAtomRange->_pDevData;
     gpu->psPmeAtomGridIndex = new CUDAStream<float2>(gpu->natoms, 1, "PmeAtomGridIndex");
@@ -1703,8 +1699,6 @@ void* gpuInit(int numAtoms, unsigned int device, bool useBlockingSync)
     gpu->psPmeBsplineModuli[2]      = NULL;
     gpu->psPmeBsplineTheta          = NULL;
     gpu->psPmeBsplineDtheta         = NULL;
-    gpu->psPmeParticleIndex         = NULL;
-    gpu->psPmeParticleFraction      = NULL;
     gpu->psPmeAtomRange             = NULL;
     gpu->psPmeAtomGridIndex         = NULL;
     gpu->psShakeID                  = NULL;
@@ -1872,8 +1866,6 @@ void gpuShutDown(gpuContext gpu)
         delete gpu->psPmeBsplineModuli[2];
         delete gpu->psPmeBsplineTheta;
         delete gpu->psPmeBsplineDtheta;
-        delete gpu->psPmeParticleIndex;
-        delete gpu->psPmeParticleFraction;
         delete gpu->psPmeAtomRange;
         delete gpu->psPmeAtomGridIndex;
         delete gpu->psTabulatedErfc;

platforms/cuda/src/kernels/gputypes.h

@@ -111,8 +111,6 @@ struct _gpuContext {
     CUDAStream<float>* psPmeBsplineModuli[3];
     CUDAStream<float4>* psPmeBsplineTheta;
     CUDAStream<float4>* psPmeBsplineDtheta;
-    CUDAStream<int4>* psPmeParticleIndex;      // The grid indices for each atom
-    CUDAStream<float4>* psPmeParticleFraction; // Fractional offset in the grid for each atom in all three dimensions.
     CUDAStream<int>* psPmeAtomRange;           // The range of sorted atoms at each grid point
     CUDAStream<float2>* psPmeAtomGridIndex;    // The grid point each atom is at
     CUDAStream<float2>* psObcData;

platforms/cuda/src/kernels/kCalculatePME.cu

@@ -99,20 +99,14 @@ __global__ void kUpdateGridIndexAndFraction_kernel()
 
     for (int i = tid; i < cSim.atoms; i += tnb)
     {
-        float4 ftmp = cSim.pPosq[i];
-        float3 t = make_float3((ftmp.x/cSim.periodicBoxSizeX+1.0f)*cSim.pmeGridSize.x,
-                               (ftmp.y/cSim.periodicBoxSizeY+1.0f)*cSim.pmeGridSize.y,
-                               (ftmp.z/cSim.periodicBoxSizeZ+1.0f)*cSim.pmeGridSize.z);
-        float3 tix;
-        ftmp.x = modff(t.x, &tix.x);
-        ftmp.y = modff(t.y, &tix.y);
-        ftmp.z = modff(t.z, &tix.z);
-        cSim.pPmeParticleFraction[i] = ftmp;
-        int4 itmp = make_int4(fast_mod(__float2int_rd(tix.x), cSim.pmeGridSize.x),
-                              fast_mod(__float2int_rd(tix.y), cSim.pmeGridSize.y),
-                              fast_mod(__float2int_rd(tix.z), cSim.pmeGridSize.z), 0);
-        cSim.pPmeParticleIndex[i] = itmp;
-        cSim.pPmeAtomGridIndex[i] = make_float2(i, itmp.x*cSim.pmeGridSize.y*cSim.pmeGridSize.z+itmp.y*cSim.pmeGridSize.z+itmp.z);
+        float4 posq = cSim.pPosq[i];
+        float3 t = make_float3((posq.x/cSim.periodicBoxSizeX+1.0f)*cSim.pmeGridSize.x,
+                               (posq.y/cSim.periodicBoxSizeY+1.0f)*cSim.pmeGridSize.y,
+                               (posq.z/cSim.periodicBoxSizeZ+1.0f)*cSim.pmeGridSize.z);
+        int3 gridIndex = make_int3(((int) t.x) % cSim.pmeGridSize.x,
+                              ((int) t.y) % cSim.pmeGridSize.y,
+                              ((int) t.z) % cSim.pmeGridSize.z);
+        cSim.pPmeAtomGridIndex[i] = make_float2(i, gridIndex.x*cSim.pmeGridSize.y*cSim.pmeGridSize.z+gridIndex.y*cSim.pmeGridSize.z+gridIndex.z);
     }
 }
 
@@ -173,7 +167,11 @@ __global__ void kUpdateBsplines_kernel()
             ddata[j] = make_float4(0.0f);
         }
 
-        float4 dr = cSim.pPmeParticleFraction[i];
+        float4 posq = cSim.pPosq[tid];
+        float3 t = make_float3((posq.x/cSim.periodicBoxSizeX+1.0f)*cSim.pmeGridSize.x,
+                               (posq.y/cSim.periodicBoxSizeY+1.0f)*cSim.pmeGridSize.y,
+                               (posq.z/cSim.periodicBoxSizeZ+1.0f)*cSim.pmeGridSize.z);
+        float4 dr = make_float4(t.x-(int) t.x, t.y-(int) t.y, t.z-(int) t.z, 0.0f);
 
         data[PME_ORDER - 1] = make_float4(0.0f);
         data[1]            = dr;
@@ -295,7 +293,12 @@ __global__ void kGridInterpolateForce_kernel()
     {
         float3 force = make_float3(0.0f, 0.0f, 0.0f);
         float4 posq = cSim.pPosq[atom];
-        int4 gridIndex = cSim.pPmeParticleIndex[atom];
+        float3 t = make_float3((posq.x/cSim.periodicBoxSizeX+1.0f)*cSim.pmeGridSize.x,
+                               (posq.y/cSim.periodicBoxSizeY+1.0f)*cSim.pmeGridSize.y,
+                               (posq.z/cSim.periodicBoxSizeZ+1.0f)*cSim.pmeGridSize.z);
+        int3 gridIndex = make_int3(((int) t.x) % cSim.pmeGridSize.x,
+                              ((int) t.y) % cSim.pmeGridSize.y,
+                              ((int) t.z) % cSim.pmeGridSize.z);
         for (int ix = 0; ix < PME_ORDER; ix++)
         {
             int xindex = (gridIndex.x + ix) % cSim.pmeGridSize.x;
@@ -347,6 +350,6 @@ void kCalculatePME(gpuContext gpu)
     kReciprocalConvolution_kernel<<<gpu->sim.blocks, gpu->sim.nonbond_threads_per_block>>>();
     LAUNCHERROR("kReciprocalConvolution");
     cufftExecC2C(gpu->fftplan, gpu->psPmeGrid->_pDevData, gpu->psPmeGrid->_pDevData, CUFFT_INVERSE);
-    kGridInterpolateForce_kernel<<<gpu->sim.blocks, gpu->sim.update_threads_per_block>>>();
+    kGridInterpolateForce_kernel<<<2*gpu->sim.blocks, gpu->sim.update_threads_per_block>>>();
     LAUNCHERROR("kGridInterpolateForce");
 }