Add CUDA caching allocator accessor

README.md

@@ -51,6 +51,7 @@ With the caching memory allocator, device allocations and frees should logically
 - `cutorch.getState()` - Returns the global state of the cutorch package. This state is not for users, it stores the raw RNG states, cublas handles and other thread and device-specific stuff.
 - `cutorch.withDevice(devID, f)` - This is a convenience for multi-GPU code, that takes in a device ID as well as a function f. It switches cutorch to the new device, executes the function f, and switches back cutorch to the original device.
 - `cutorch.createCudaHostTensor([...])` - Allocates a `torch.FloatTensor` of [host-pinned memory](https://devblogs.nvidia.com/parallelforall/how-optimize-data-transfers-cuda-cc/), where dimensions can be given as an argument list of sizes or a `torch.LongStorage`.
+- `cutorch.isCachingAllocatorEnabled()` - Returns whether the caching CUDA memory allocator is enabled or not.
 
 #### Low-level streams functions (dont use this as a user, easy to shoot yourself in the foot):
 - `cutorch.reserveStreams(n [, nonblocking])`: creates n user streams for use on every device. NOTE: stream index `s` on device 1 is a different cudaStream_t than stream `s` on device 2. Takes an optional non-blocking flag; by default, this is assumed to be false. If true, then the stream is created with cudaStreamNonBlocking.

init.c

@@ -699,6 +699,14 @@ static int cutorch_setKernelPeerToPeerAccess(lua_State *L)
   return 0;
 }
 
+static int cutorch_isCachingAllocatorEnabled(lua_State *L)
+{
+  THCState *state = cutorch_getstate(L);
+  lua_pushboolean(L, THCState_isCachingAllocatorEnabled(state));
+
+  return 1;
+}
+
 static int cutorch_getMemoryUsage(lua_State *L) {
   size_t freeBytes = 0;
   size_t totalBytes = 0;
@@ -993,6 +1001,7 @@ static const struct luaL_Reg cutorch_stuff__ [] = {
   {"setPeerToPeerAccess", cutorch_setPeerToPeerAccess},
   {"setKernelPeerToPeerAccess", cutorch_setKernelPeerToPeerAccess},
   {"getKernelPeerToPeerAccess", cutorch_getKernelPeerToPeerAccess},
+  {"isCachingAllocatorEnabled", cutorch_isCachingAllocatorEnabled},
   {"getDeviceProperties", cutorch_getDeviceProperties},
   {"getRuntimeVersion", cutorch_getRuntimeVersion},
   {"getDriverVersion", cutorch_getDriverVersion},

lib/THC/THCGeneral.c

@@ -303,6 +303,10 @@ void THCState_setDeviceAllocator(THCState* state, THCDeviceAllocator* allocator)
   state->cudaDeviceAllocator = allocator;
 }
 
+int THCState_isCachingAllocatorEnabled(THCState* state) {
+  return state->cudaHostAllocator == &THCCachingHostAllocator;
+}
+
 int THCState_getNumDevices(THCState *state)
 {
   return state->numDevices;

lib/THC/THCGeneral.h.in

@@ -141,6 +141,7 @@ THC_API THAllocator* THCState_getCudaHostAllocator(THCState* state);
 THC_API THAllocator* THCState_getCudaUVAAllocator(THCState* state);
 THC_API THCDeviceAllocator* THCState_getDeviceAllocator(THCState* state);
 THC_API void THCState_setDeviceAllocator(THCState* state, THCDeviceAllocator* allocator);
+THC_API int THCState_isCachingAllocatorEnabled(THCState* state);
 
 THC_API void THCMagma_init(THCState *state);