Refactoring

GPUSimulators/Autotuner.py

@@ -60,7 +60,7 @@ class Autotuner:
                     return
     
         # Set arguments to send to the simulators during construction
-        context = Common.CudaContext(autotuning=False)
+        context = CudaContext.CudaContext(autotuning=False)
         g = 9.81
         h0, hu0, hv0, dx, dy, dt = Autotuner.gen_test_data(nx=self.nx, ny=self.ny, g=g)
         arguments = {

GPUSimulators/Common.py

@@ -186,7 +186,7 @@ Class that holds 2D data
 """
 class CudaArray2D:
     """
-    Uploads initial data to the CL device
+    Uploads initial data to the CUDA device
     """
     def __init__(self, stream, nx, ny, x_halo, y_halo, cpu_data=None, dtype=np.float32):
         self.logger =  logging.getLogger(__name__)
@@ -217,10 +217,8 @@ class CudaArray2D:
         copy.set_dst_device(self.data.gpudata)
             
         #Set offsets of upload in destination
-        x_offset = (nx_halo - cpu_data.shape[1]) // 2
+        copy.dst_x_in_bytes = x_halo*self.data.strides[1]
-        y_offset = (ny_halo - cpu_data.shape[0]) // 2
+        copy.dst_y = y_halo
-        copy.dst_x_in_bytes = x_offset*self.data.strides[1]
-        copy.dst_y = y_offset
         
         #Set destination pitch
         copy.dst_pitch = self.data.strides[0]

GPUSimulators/CudaContext.py

@@ -78,8 +78,8 @@ class CudaContext(object):
         self.logger.info("Created context handle <%s>", str(self.cuda_context.handle))
         
         #Create cache dir for cubin files
-        if (self.use_cache):
         self.cache_path = os.path.join(self.module_path, "cuda_cache") 
+        if (self.use_cache):
             if not os.path.isdir(self.cache_path):
                 os.mkdir(self.cache_path)
             self.logger.info("Using CUDA cache dir %s", self.cache_path)

GPUSimulators/EE2D_KP07_dimsplit.py

@@ -21,6 +21,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 #Import packages we need
 from GPUSimulators import Simulator, Common
+from GPUSimulators.Simulator import BaseSimulator, BoundaryCondition
 import numpy as np
 
 
@@ -34,7 +35,7 @@ import numpy as np
 """
 Class that solves the SW equations using the Forward-Backward linear scheme
 """
-class EE2D_KP07_dimsplit (Simulator.BaseSimulator):
+class EE2D_KP07_dimsplit (BaseSimulator):
 
     """
     Initialization routine
@@ -47,6 +48,7 @@ class EE2D_KP07_dimsplit (Simulator.BaseSimulator):
     dx: Grid cell spacing along x-axis
     dy: Grid cell spacing along y-axis
     dt: Size of each timestep 
+    g: Gravitational constant
     gamma: Gas constant
     p: pressure
     """
@@ -55,8 +57,11 @@ class EE2D_KP07_dimsplit (Simulator.BaseSimulator):
                  rho, rho_u, rho_v, E, \
                  nx, ny, \
                  dx, dy, dt, \
+                 g, \
                  gamma, \
                  theta=1.3, \
+                 order=2, \
+                 boundaryConditions=BoundaryCondition(), \
                  block_width=16, block_height=8):
                  
         # Call super constructor
@@ -64,12 +69,15 @@ class EE2D_KP07_dimsplit (Simulator.BaseSimulator):
             nx, ny, \
             dx, dy, dt, \
             block_width, block_height)
+        self.g = np.float32(g)
         self.gamma = np.float32(gamma)
         self.theta = np.float32(theta) 
+        self.order = np.int32(order)
+        self.boundaryConditions = boundaryConditions.asCodedInt()
 
         #Get kernels
         self.kernel = context.get_prepared_kernel("cuda/EE2D_KP07_dimsplit.cu", "KP07DimsplitKernel", \
-                                        "iifffffiPiPiPiPiPiPiPiPi", \
+                                        "iiffffffiiPiPiPiPiPiPiPiPi", \
                                         defines={
                                             'BLOCK_WIDTH': self.block_size[0], 
                                             'BLOCK_HEIGHT': self.block_size[1]
@@ -100,9 +108,11 @@ class EE2D_KP07_dimsplit (Simulator.BaseSimulator):
         self.kernel.prepared_async_call(self.grid_size, self.block_size, self.stream, \
                 self.nx, self.ny, \
                 self.dx, self.dy, dt, \
+                self.g, \
                 self.gamma, \
                 self.theta, \
-                np.int32(0), \
+                Simulator.stepOrderToCodedInt(step=0, order=self.order), \
+                self.boundaryConditions, \
                 self.u0[0].data.gpudata, self.u0[0].data.strides[0], \
                 self.u0[1].data.gpudata, self.u0[1].data.strides[0], \
                 self.u0[2].data.gpudata, self.u0[2].data.strides[0], \
@@ -119,9 +129,11 @@ class EE2D_KP07_dimsplit (Simulator.BaseSimulator):
         self.kernel.prepared_async_call(self.grid_size, self.block_size, self.stream, \
                 self.nx, self.ny, \
                 self.dx, self.dy, dt, \
+                self.g, \
                 self.gamma, \
                 self.theta, \
-                np.int32(1), \
+                Simulator.stepOrderToCodedInt(step=0, order=self.order), \
+                self.boundaryConditions, \
                 self.u0[0].data.gpudata, self.u0[0].data.strides[0], \
                 self.u0[1].data.gpudata, self.u0[1].data.strides[0], \
                 self.u0[2].data.gpudata, self.u0[2].data.strides[0], \
@@ -140,3 +152,4 @@ class EE2D_KP07_dimsplit (Simulator.BaseSimulator):
     def check(self):
         self.u0.check()
         self.u1.check()
+        pass

GPUSimulators/Simulator.py

@@ -23,6 +23,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #Import packages we need
 import numpy as np
 import logging
+from enum import IntEnum
 
 import pycuda.compiler as cuda_compiler
 import pycuda.gpuarray
@@ -31,7 +32,68 @@ import pycuda.driver as cuda
 from GPUSimulators import Common
 
 
-class BaseSimulator:
+        
+
+
+class BoundaryCondition(object):    
+    """
+    Class for holding boundary conditions for global boundaries
+    """
+    
+    
+    class Type(IntEnum):
+        """
+        Enum that describes the different types of boundary conditions
+        WARNING: MUST MATCH THAT OF common.h IN CUDA
+        """
+        Dirichlet = 0,
+        Neumann = 1,
+        Periodic = 2,
+        Reflective = 3
+        
+        
+        
+    def __init__(self, types={ \
+                    'north': Type.Reflective, \
+                    'south': Type.Reflective, \
+                    'east': Type.Reflective, \
+                    'west': Type.Reflective \
+                 }):
+        """
+        Constructor
+        """
+        self.north = types['north']
+        self.south = types['south']
+        self.east = types['east']
+        self.west = types['west']
+
+        
+    def asCodedInt(self):
+        """
+        Helper function which packs four boundary conditions into one integer
+        """
+        bc = 0
+        bc = bc | (self.north & 0x000F) << 24
+        bc = bc | (self.south & 0x000F) << 16
+        bc = bc | (self.east & 0x000F) << 8
+        bc = bc | (self.west & 0x000F) 
+        
+        #for t in types:
+        #    print("{0:s}, {1:d}, {1:032b}, {1:08b}".format(t, types[t]))
+        #print("bc: {0:032b}".format(bc))
+        
+        return np.int32(bc)    
+    
+    
+    
+    
+class BaseSimulator(object):
+   
+    def __init__(self, \
+                 context, \
+                 nx, ny, \
+                 dx, dy, dt, \
+                 block_width, block_height):
         """
         Initialization routine
         context: GPU context to use
@@ -45,11 +107,6 @@ class BaseSimulator:
         dy: Grid cell spacing along y-axis (20 000 m)
         dt: Size of each timestep (90 s)
         """
-    def __init__(self, \
-                 context, \
-                 nx, ny, \
-                 dx, dy, dt, \
-                 block_width, block_height):
         #Get logger
         self.logger = logging.getLogger(__name__ + "." + self.__class__.__name__)
         
@@ -88,17 +145,19 @@ class BaseSimulator:
     def __str__(self):
         return "{:s} [{:d}x{:d}]".format(self.__class__.__name__, self.nx, self.ny)
                       
+    
+    def simulate(self, t_end):
         """
         Function which simulates forward in time using the default simulation type
         """
-    def simulate(self, t_end):
         raise(exceptions.NotImplementedError("Needs to be implemented in subclass"))
                       
+    
+    def simulateEuler(self, t_end):
         """ 
         Function which simulates t_end seconds using forward Euler
         Requires that the stepEuler functionality is implemented in the subclasses
         """
-    def simulateEuler(self, t_end):
         # Compute number of timesteps to perform
         n = int(t_end / self.dt + 1)
 
@@ -119,17 +178,21 @@ class BaseSimulator:
             print_string = printer.getPrintString(i)
             if (print_string):
                 self.logger.info("%s (Euler): %s", self, print_string)
+                try:
                     self.check()
+                except AssertionError as e:
+                    e.args += ("Step={:d}, time={:f}".format(self.simSteps(), self.simTime()))
+                    raise
     
             
         #self.logger.info("%s simulated %f seconds to %f with %d steps (Euler)", self, t_end, self.t, n)
         return self.t, n
         
+    def simulateRK(self, t_end, order):    
         """
         Function which simulates t_end seconds using Runge-Kutta 2
         Requires that the stepRK functionality is implemented in the subclasses
         """
-    def simulateRK(self, t_end, order):
         # Compute number of timesteps to perform
         n = int(t_end / self.dt + 1)
         
@@ -150,15 +213,20 @@ class BaseSimulator:
             print_string = printer.getPrintString(i)
             if (print_string):
                 self.logger.info("%s (RK2): %s", self, print_string)
+                try:
                     self.check()
+                except AssertionError as e:
+                    e.args += ("Step={:d}, time={:f}".format(self.simSteps(), self.simTime()))
+                    raise
     
         return self.t, n
         
+    
+    def simulateDimsplit(self, t_end):
         """
         Function which simulates t_end seconds using second order dimensional splitting (XYYX)
         Requires that the stepDimsplitX and stepDimsplitY functionality is implemented in the subclasses
         """
-    def simulateDimsplit(self, t_end):
         # Compute number of timesteps to perform
         n = int(t_end / (2.0*self.dt) + 1)
         
@@ -180,24 +248,37 @@ class BaseSimulator:
             print_string = printer.getPrintString(i)
             if (print_string):
                 self.logger.info("%s (Dimsplit): %s", self, print_string)
+                try:
                     self.check()
+                except AssertionError as e:
+                    e.args += ("Step={:d}, time={:f}".format(self.simSteps(), self.simTime()))
+                    raise
             
         return self.t, 2*n
         
     
+    def stepEuler(self, dt):
         """
         Function which performs one single timestep of size dt using forward euler
         """
-    def stepEuler(self, dt):
         raise(NotImplementedError("Needs to be implemented in subclass"))
         
     def stepRK(self, dt, substep):
+        """
+        Function which performs one single timestep of size dt using Runge-Kutta
+        """
         raise(NotImplementedError("Needs to be implemented in subclass"))
     
     def stepDimsplitXY(self, dt):
+        """
+        Function which performs one single timestep of size dt using dimensional splitting
+        """
         raise(NotImplementedError("Needs to be implemented in subclass"))
         
     def stepDimsplitYX(self, dt):
+        """
+        Function which performs one single timestep of size dt using dimensional splitting
+        """
         raise(NotImplementedError("Needs to be implemented in subclass"))
 
     def download(self):
@@ -215,3 +296,25 @@ class BaseSimulator:
     def simSteps(self):
         return self.nt
         
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        
+def stepOrderToCodedInt(step, order):
+    """
+    Helper function which packs the step and order into a single integer
+    """
+    step_order = (step << 16) ^ (order & 0x00ff)
+    #print("Step:  {0:032b}".format(step))
+    #print("Order: {0:032b}".format(order))
+    #print("Mix:   {0:032b}".format(step_order))
+    return np.int32(step_order)

GPUSimulators/cuda/EE2D_KP07_dimsplit.cu

@@ -122,14 +122,17 @@ void computeFluxG(float Q[4][BLOCK_HEIGHT+4][BLOCK_WIDTH+4],
   * This unsplit kernel computes the 2D numerical scheme with a TVD RK2 time integration scheme
   */
 extern "C" {
+    
 __global__ void KP07DimsplitKernel(
         int nx_, int ny_,
         float dx_, float dy_, float dt_,
+        float g_,
         float gamma_,
         
         float theta_,
         
-        int step_,
+        int step_order_,
+        int boundary_conditions_,
         
         //Input h^n
         float* rho0_ptr_, int rho0_pitch_,
@@ -142,7 +145,6 @@ __global__ void KP07DimsplitKernel(
         float* rho_u1_ptr_, int rho_u1_pitch_,
         float* rho_v1_ptr_, int rho_v1_pitch_,
         float* E1_ptr_, int E1_pitch_) {
-        
     const unsigned int w = BLOCK_WIDTH;
     const unsigned int h = BLOCK_HEIGHT;
     const unsigned int gc = 2;
@@ -153,8 +155,6 @@ __global__ void KP07DimsplitKernel(
     __shared__ float Qx[4][h+4][w+4];
     __shared__ float  F[4][h+4][w+4];
     
-    
-    
     //Read into shared memory
     readBlock<w, h, gc>(  rho0_ptr_,   rho0_pitch_, Q[0], nx_, ny_);
     readBlock<w, h, gc>(rho_u0_ptr_, rho_u0_pitch_, Q[1], nx_, ny_);
@@ -167,13 +167,10 @@ __global__ void KP07DimsplitKernel(
     noFlowBoundary<w, h, gc, -1,  1>(Q[1], nx_, ny_);
     noFlowBoundary<w, h, gc,  1, -1>(Q[2], nx_, ny_);
     noFlowBoundary<w, h, gc,  1,  1>(Q[3], nx_, ny_);
-    __syncthreads();
-    
-    const float g = 0.1f;
 
 
     //Step 0 => evolve x first, then y
-    if (step_ == 0) {
+    if (getStep(step_order_) == 0) {
         //Compute fluxes along the x axis and evolve
         minmodSlopeX<w, h, gc, vars>(Q, Qx, theta_);
         __syncthreads();
@@ -184,17 +181,11 @@ __global__ void KP07DimsplitKernel(
         evolveF<w, h, gc, vars>(Q, F, dx_, dt_);
         __syncthreads();
 
-        //Set boundary conditions
-        noFlowBoundary<w, h, gc,  1,  1>(Q[0], nx_, ny_);
-        noFlowBoundary<w, h, gc, -1,  1>(Q[1], nx_, ny_);
-        noFlowBoundary<w, h, gc,  1, -1>(Q[2], nx_, ny_);
-        noFlowBoundary<w, h, gc,  1,  1>(Q[3], nx_, ny_);
-        __syncthreads();
-
         //Compute fluxes along the y axis and evolve
         minmodSlopeY<w, h, gc, vars>(Q, Qx, theta_);
         __syncthreads();
 
+        
         computeFluxG(Q, Qx, F, gamma_, dy_, dt_);
         __syncthreads();
 
@@ -202,15 +193,14 @@ __global__ void KP07DimsplitKernel(
         __syncthreads();    
         
         //Gravity source term
-        {
+        if (g_ > 0.0f) {
             const int i = threadIdx.x + gc;
             const int j = threadIdx.y + gc;
             const float rho_v = Q[2][j][i];
-            Q[2][j][i] -= g*Q[0][j][i]*dt_;
+            Q[2][j][i] -= g_*Q[0][j][i]*dt_;
-            Q[3][j][i] -= g*rho_v*dt_;
+            Q[3][j][i] -= g_*rho_v*dt_;
-        }
             __syncthreads();
-
+        }
     }
     //Step 1 => evolve y first, then x
     else {
@@ -224,13 +214,6 @@ __global__ void KP07DimsplitKernel(
         evolveG<w, h, gc, vars>(Q, F, dy_, dt_);
         __syncthreads();
         
-        //Set boundary conditions
-        noFlowBoundary<w, h, gc,  1,  1>(Q[0], nx_, ny_);
-        noFlowBoundary<w, h, gc, -1,  1>(Q[1], nx_, ny_);
-        noFlowBoundary<w, h, gc,  1, -1>(Q[2], nx_, ny_);
-        noFlowBoundary<w, h, gc,  1,  1>(Q[3], nx_, ny_);
-        __syncthreads();
-        
         //Compute fluxes along the x axis and evolve
         minmodSlopeX<w, h, gc, vars>(Q, Qx, theta_);
         __syncthreads();
@@ -242,16 +225,17 @@ __global__ void KP07DimsplitKernel(
         __syncthreads();
         
         //Gravity source term
-        {
+        if (g_ > 0.0f) {
             const int i = threadIdx.x + gc;
             const int j = threadIdx.y + gc;
             const float rho_v = Q[2][j][i];
-            Q[2][j][i] -= g*Q[0][j][i]*dt_;
+            Q[2][j][i] -= g_*Q[0][j][i]*dt_;
-            Q[3][j][i] -= g*rho_v*dt_;
+            Q[3][j][i] -= g_*rho_v*dt_;
-        }
             __syncthreads();
+        }
         
         //This is the RK2-part
+        if (getOrder(step_order_) == 2) {
             const int tx = threadIdx.x + gc;
             const int ty = threadIdx.y + gc;
             const float q1 = Q[0][ty][tx];
@@ -271,6 +255,7 @@ __global__ void KP07DimsplitKernel(
             Q[2][ty][tx] = 0.5f*( Q[2][ty][tx] + q3 );
             Q[3][ty][tx] = 0.5f*( Q[3][ty][tx] + q4 );
         }        
+    }
 
     
     // Write to main memory for all internal cells

GPUSimulators/cuda/common.h

@@ -167,90 +167,116 @@ inline __device__ void writeBlock(float* ptr_, int pitch_,
 
 template<int block_width, int block_height, int ghost_cells, int scale_east_west=1, int scale_north_south=1>
 __device__ void noFlowBoundary(float Q[block_height+2*ghost_cells][block_width+2*ghost_cells], const int nx_, const int ny_) {
+    bcEastReflective<block_width, block_height, ghost_cells, scale_east_west>(Q, nx_, ny_);
+    bcWestReflective<block_width, block_height, ghost_cells, scale_east_west>(Q, nx_, ny_);
+    __syncthreads();
+    bcNorthReflective<block_width, block_height, ghost_cells, scale_north_south>(Q, nx_, ny_);
+    bcSouthReflective<block_width, block_height, ghost_cells, scale_north_south>(Q, nx_, ny_);
+    __syncthreads();
+}
 
+
+// West boundary
+template<int block_width, int block_height, int ghost_cells, int sign>
+__device__ void bcWestReflective(float Q[block_height+2*ghost_cells][block_width+2*ghost_cells], const int nx_, const int ny_) {
     for (int j=threadIdx.y; j<block_height+2*ghost_cells; j+= block_height) {
         const int i = threadIdx.x + ghost_cells;
         const int ti = blockDim.x*blockIdx.x + i;
-        const int tj = blockDim.y*blockIdx.y + j;
         
-        // West boundary
         if (ti == ghost_cells) {
-            Q[j][i-1] = scale_east_west*Q[j][i];
+            Q[j][i-1] = sign*Q[j][i];
         }
         if (ghost_cells >= 2 && ti == ghost_cells + 1) {
-            Q[j][i-3] = scale_east_west*Q[j][i];
+            Q[j][i-3] = sign*Q[j][i];
         }
         if (ghost_cells >= 3 && ti == ghost_cells + 2) {
-            Q[j][i-5] = scale_east_west*Q[j][i];
+            Q[j][i-5] = sign*Q[j][i];
         }
         if (ghost_cells >= 4 && ti == ghost_cells + 3) {
-            Q[j][i-7] = scale_east_west*Q[j][i];
+            Q[j][i-7] = sign*Q[j][i];
         }
         if (ghost_cells >= 5 && ti == ghost_cells + 4) {
-            Q[j][i-9] = scale_east_west*Q[j][i];
+            Q[j][i-9] = sign*Q[j][i];
+        }
+    }
 }
-        
 
 
 // East boundary
+template<int block_width, int block_height, int ghost_cells, int sign>
+__device__ void bcEastReflective(float Q[block_height+2*ghost_cells][block_width+2*ghost_cells], const int nx_, const int ny_) {
+    for (int j=threadIdx.y; j<block_height+2*ghost_cells; j+= block_height) {
+        const int i = threadIdx.x + ghost_cells;
+        const int ti = blockDim.x*blockIdx.x + i;
+        
         if (ti == nx_ + ghost_cells - 1) {
-            Q[j][i+1] = scale_east_west*Q[j][i];
+            Q[j][i+1] = sign*Q[j][i];
         }
         if (ghost_cells >= 2 && ti == nx_ + ghost_cells - 2) {
-            Q[j][i+3] = scale_east_west*Q[j][i];
+            Q[j][i+3] = sign*Q[j][i];
         }
         if (ghost_cells >= 3 && ti == nx_ + ghost_cells - 3) {
-            Q[j][i+5] = scale_east_west*Q[j][i];
+            Q[j][i+5] = sign*Q[j][i];
         }
         if (ghost_cells >= 4 && ti == nx_ + ghost_cells - 4) {
-            Q[j][i+7] = scale_east_west*Q[j][i];
+            Q[j][i+7] = sign*Q[j][i];
         }
         if (ghost_cells >= 5 && ti == nx_ + ghost_cells - 5) {
-            Q[j][i+9] = scale_east_west*Q[j][i];
+            Q[j][i+9] = sign*Q[j][i];
+        }
     }
 }
     
     
-
-    for (int i=threadIdx.x; i<block_width+2*ghost_cells; i+= block_width) {
-        const int j = threadIdx.y + ghost_cells;
-        const int ti = blockDim.x*blockIdx.x + i;
-        const int tj = blockDim.y*blockIdx.y + j;
-
 // South boundary
+template<int block_width, int block_height, int ghost_cells, int sign>
+__device__ void bcSouthReflective(float Q[block_height+2*ghost_cells][block_width+2*ghost_cells], const int nx_, const int ny_) {
+    for (int i=threadIdx.x; i<block_width+2*ghost_cells; i+= block_width) {
+        const int j = threadIdx.y + ghost_cells;
+        const int tj = blockDim.y*blockIdx.y + j;
+
         if (tj == ghost_cells) {
-            Q[j-1][i] = scale_north_south*Q[j][i];
+            Q[j-1][i] = sign*Q[j][i];
         }
         if (ghost_cells >= 2 && tj == ghost_cells + 1) {
-            Q[j-3][i] = scale_north_south*Q[j][i];
+            Q[j-3][i] = sign*Q[j][i];
         }
         if (ghost_cells >= 3 && tj == ghost_cells + 2) {
-            Q[j-5][i] = scale_north_south*Q[j][i];
+            Q[j-5][i] = sign*Q[j][i];
         }
         if (ghost_cells >= 4 && tj == ghost_cells + 3) {
-            Q[j-7][i] = scale_north_south*Q[j][i];
+            Q[j-7][i] = sign*Q[j][i];
         }
         if (ghost_cells >= 5 && tj == ghost_cells + 4) {
-            Q[j-9][i] = scale_north_south*Q[j][i];
+            Q[j-9][i] = sign*Q[j][i];
         }
+    }
+}
+        
         
         
     
 // North boundary
+template<int block_width, int block_height, int ghost_cells, int sign>
+__device__ void bcNorthReflective(float Q[block_height+2*ghost_cells][block_width+2*ghost_cells], const int nx_, const int ny_) {
+    for (int i=threadIdx.x; i<block_width+2*ghost_cells; i+= block_width) {
+        const int j = threadIdx.y + ghost_cells;
+        const int tj = blockDim.y*blockIdx.y + j;
+        
         if (tj == ny_ + ghost_cells - 1) {
-            Q[j+1][i] = scale_north_south*Q[j][i];
+            Q[j+1][i] = sign*Q[j][i];
         }
         if (ghost_cells >= 2 && tj == ny_ + ghost_cells - 2) {
-            Q[j+3][i] = scale_north_south*Q[j][i];
+            Q[j+3][i] = sign*Q[j][i];
         }
         if (ghost_cells >= 3 && tj == ny_ + ghost_cells - 3) {
-            Q[j+5][i] = scale_north_south*Q[j][i];
+            Q[j+5][i] = sign*Q[j][i];
         }
         if (ghost_cells >= 4 && tj == ny_ + ghost_cells - 4) {
-            Q[j+7][i] = scale_north_south*Q[j][i];
+            Q[j+7][i] = sign*Q[j][i];
         }
         if (ghost_cells >= 5 && tj == ny_ + ghost_cells - 5) {
-            Q[j+9][i] = scale_north_south*Q[j][i];
+            Q[j+9][i] = sign*Q[j][i];
         }
     }
 }
@@ -282,7 +308,7 @@ __device__ void evolveF(float Q[vars][block_height+2*ghost_cells][block_width+2*
               const float dx_, const float dt_) {
     for (int var=0; var < vars; ++var) {
         for (int j=threadIdx.y; j<block_height+2*ghost_cells; j+=block_height) {
-            for (int i=threadIdx.x+1; i<block_width+2*ghost_cells; i+=block_width) {
+            for (int i=threadIdx.x+ghost_cells; i<block_width+ghost_cells; i+=block_width) {
                 Q[var][j][i] = Q[var][j][i] + (F[var][j][i-1] - F[var][j][i]) * dt_ / dx_;
             }
         }
@@ -302,7 +328,7 @@ __device__ void evolveG(float Q[vars][block_height+2*ghost_cells][block_width+2*
               float G[vars][block_height+2*ghost_cells][block_width+2*ghost_cells],
               const float dy_, const float dt_) {
     for (int var=0; var < vars; ++var) {
-        for (int j=threadIdx.y+1; j<block_height+2*ghost_cells; j+=block_height) {
+        for (int j=threadIdx.y+ghost_cells; j<block_height+ghost_cells; j+=block_height) {
             for (int i=threadIdx.x; i<block_width+2*ghost_cells; i+=block_width) {
                 Q[var][j][i] = Q[var][j][i] + (G[var][j-1][i] - G[var][j][i]) * dt_ / dy_;
             }
@@ -329,11 +355,45 @@ __device__ void memset(float Q[vars][shmem_height][shmem_width], float value) {
 } 
 
 
-
+/**
-
+  * Returns the step stored in the leftmost 16 bits 
-
+  * of the 32 bit step-order integer
-
+  */
-
+inline __device__ int getStep(int step_order_) {
+    return step_order_ >> 16;
+}
+
+/**
+  * Returns the order stored in the rightmost 16 bits 
+  * of the 32 bit step-order integer
+  */
+inline __device__ int getOrder(int step_order_) {
+    return step_order_ & 0x0000FFFF;
+}
+
+
+enum BoundaryCondition {
+    Dirichlet = 0,
+    Neumann = 1,
+    Periodic = 2,
+    Reflective = 3
+};
+
+inline __device__ BoundaryCondition getBCNorth(int bc_) {
+    return static_cast<BoundaryCondition>(bc_ & 0x000F);
+}
+
+inline __device__ BoundaryCondition getBCSouth(int bc_) {
+    return static_cast<BoundaryCondition>((bc_ >> 8) & 0x000F);
+}
+
+inline __device__ BoundaryCondition getBCEast(int bc_) {
+    return static_cast<BoundaryCondition>((bc_ >> 16) & 0x000F);
+}
+
+inline __device__ BoundaryCondition getBCWest(int bc_) {
+    return static_cast<BoundaryCondition>(bc_ >> 24);
+}