add dot product example

src/cuda.nim

@@ -59,6 +59,8 @@ proc cudaLaunchKernel*(function_address: pointer; numBlocks: Dim3; dimBlocks: Di
 #                      args: ptr pointer; sharedMemBytes: csize_t; stream: cudaStream_t): cint {.
 #     importcpp: "cudaLaunchKernel(@)", header: "cuda_runtime.h".}
 proc cudaDeviceSynchronize*(): cudaError_t {.header: "cuda_runtime.h",importcpp: "cudaDeviceSynchronize(@)".}
+proc cudaSyncthreads*() {.importcpp: "__syncthreads()", header: "cuda_runtime.h".}
+proc hippoSyncthreads*() {.importcpp: "__syncthreads()", header: "cuda_runtime.h".}
 
 proc cudaLaunchKernelGGL*(
   function_address: proc;
@@ -116,4 +118,9 @@ template hippoDevice*(body: typed) =
 template hippoHost*(body: typed) =
   {.push stackTrace: off, checks: off, exportc, codegenDecl: "__host__ $# $#$#".}
   body
+  {.pop}
+
+template hippoShared*(body: typed) =
+  {.push stackTrace: off, checks: off, exportc, codegenDecl: "__shared__ $# $#$#".}
+  body
   {.pop}

src/hip.nim

@@ -56,6 +56,8 @@ proc hipLaunchKernel*(function_address: pointer; numBlocks: Dim3; dimBlocks: Dim
 #                      args: ptr pointer; sharedMemBytes: csize_t; stream: hipStream_t): cint {.
 #     importcpp: "hipLaunchKernel(@)", header: "hip/hip_runtime.h".}
 proc hipDeviceSynchronize*(): hipError_t {.header: "hip/hip_runtime.h",importcpp: "hipDeviceSynchronize(@)".}
+proc hipSyncthreads*() {.importcpp: "__syncthreads()", header: "hip/hip_runtime.h".}
+proc hippoSyncthreads*() {.importcpp: "__syncthreads()", header: "hip/hip_runtime.h".}
 
 proc hipLaunchKernelGGL*(
   function_address: proc;
@@ -112,4 +114,9 @@ template hippoDevice*(body: typed) =
 template hippoHost*(body: typed) =
   {.push stackTrace: off, checks: off, exportc, codegenDecl: "__host__ $# $#$#".}
   body
+  {.pop}
+
+template hippoShared*(body: typed) =
+  {.push stackTrace: off, checks: off, exportc, codegenDecl: "__shared__ $# $#$#".}
+  body
   {.pop}

src/hippo.nim

@@ -83,7 +83,7 @@ proc launchKernel*(
   kernel: proc,
   gridDim: Dim3 = newDim3(1,1,1), # default to a grid of 1 block
   blockDim: Dim3 = newDim3(1,1,1),  # default to 1 thread per block
-  sharedMemBytes: uint32 = 0,
+  sharedMemBytes: uint32 = 0, # TODO dynamic shared memory
   stream: HippoStream = nil,
   args: tuple
 ): HippoError =

tests/hip/dot.nim

@@ -0,0 +1,92 @@
+import hippo
+
+# GPU Dot product
+
+const 
+  N = 33 * 1024
+  ThreadsPerBlock: int = 256
+  BlocksPerGrid: int = min(32, ((N + ThreadsPerBlock - 1) div ThreadsPerBlock))
+
+proc dot(a, b, c: ptr[cfloat]){.hippoGlobal.} =
+
+  var cache {.hippoShared.}: ptr[cfloat]
+
+  # TODO figure out how to do this properly
+  let aArray = cast[ptr UncheckedArray[cfloat]](a)
+  let bArray = cast[ptr UncheckedArray[cfloat]](b)
+  let cArray = cast[ptr UncheckedArray[cfloat]](c)
+  let cacheArray = cast[ptr UncheckedArray[cfloat]](cache)
+
+  let cacheIndex = threadIdx.x
+  var tid = threadIdx.x + blockIdx.x * blockDim.x
+  var temp: cfloat = 0
+  while tid < N:
+    temp += aArray[tid] * bArray[tid]
+    tid += blockDim.x * gridDim.x
+
+  # set the cache values
+  cacheArray[cacheIndex] = temp
+
+  # synchronize threads in this block
+  hippoSyncthreads()
+
+  # for reductions, threadsPerBlock must be a power of 2
+  # because of the following code
+  var i = blockDim.x div 2
+  while i != 0:
+    if cacheIndex < i:
+      cacheArray[cacheIndex] += cacheArray[cacheIndex + i]
+    hippoSyncthreads()
+    i = i div 2
+
+  if cacheIndex == 0:
+    cArray[blockIdx.x] = cacheArray[0]
+
+
+proc main() =
+  var a, b, partial_c: array[N, int32]
+  var dev_a, dev_b, dev_partial_c: pointer
+
+  # allocate gpu memory
+  handleError(hipMalloc(addr dev_a, sizeof(float)*N))
+  handleError(hipMalloc(addr dev_b, sizeof(float)*N))
+  handleError(hipMalloc(addr dev_partial_c, BlocksPerGrid * sizeof(float)))
+
+  # fill in host memory with data
+  for i in 0 ..< N:
+    a[i] = i.int32
+    b[i] = (i * 2).int32
+
+  # copy data to device
+  handleError(hipMemcpy(dev_a, addr a[0], sizeof(float)*N, hipMemcpyHostToDevice))
+  handleError(hipMemcpy(dev_b, addr b[0], sizeof(float)*N, hipMemcpyHostToDevice))
+
+  # launch kernel
+  handleError(launchKernel(
+    dot,
+    gridDim = newDim3(BlocksPerGrid.uint32),
+    blockDim = newDim3(ThreadsPerBlock.uint32),
+    args = (dev_a, dev_b, dev_partial_c)
+  ))
+
+  # copy memory back from GPU to CPU
+  handleError(hipMemcpy(addr partial_c[0], dev_partial_c, BlocksPerGrid * sizeof(float), hipMemcpyDeviceToHost))
+
+  # finish up on the CPU
+  var c: int32 = 0
+  for i in 0 ..< BlocksPerGrid:
+    c += partial_c[i]
+
+
+  proc sum_squares(x: float): float =
+    result = x * (x + 1) * (2 * x + 1) / 6
+
+  echo "Does GPU value ", c.float, " = ", 2 * sum_squares((N - 1)), "?"
+
+  handleError(hipFree(dev_a))
+  handleError(hipFree(dev_b))
+  handleError(hipFree(dev_partial_c))
+
+
+when isMainModule:
+  main()