Fix cuda 7.5 error with cublas GEMM (#9811)

* fix gemm error for cuda 7.5

* fix version number

Author: kexinzhao

paddle/fluid/operators/math/math_function.cu

@@ -39,13 +39,14 @@ void gemm<platform::CUDADeviceContext, float16>(
   cublasOperation_t cuTransB =
       (transB == CblasNoTrans) ? CUBLAS_OP_N : CUBLAS_OP_T;
 
-  float h_alpha = static_cast<float>(alpha);
-  float h_beta = static_cast<float>(beta);
-
   // TODO(kexinzhao): add processing code for compute capability < 53 case
   PADDLE_ENFORCE_GE(context.GetComputeCapability(), 53,
                     "cublas fp16 gemm requires GPU compute capability >= 53");
 
+#if CUDA_VERSION >= 8000
+  float h_alpha = static_cast<float>(alpha);
+  float h_beta = static_cast<float>(beta);
+
   cublasGemmAlgo_t algo = CUBLAS_GEMM_DFALT;
 #if CUDA_VERSION >= 9000
   if (context.GetComputeCapability() >= 70) {
@@ -56,7 +57,7 @@ void gemm<platform::CUDADeviceContext, float16>(
     PADDLE_ENFORCE(platform::dynload::cublasSetMathMode(context.cublas_handle(),
                                                         CUBLAS_DEFAULT_MATH));
   }
-#endif
+#endif  // CUDA_VERSION >= 9000
 
   // cublasHgemm does true FP16 computation which is slow for non-Volta
   // GPUs. So use cublasGemmEx instead which does pesudo FP16 computation:
@@ -66,6 +67,18 @@ void gemm<platform::CUDADeviceContext, float16>(
       context.cublas_handle(), cuTransB, cuTransA, N, M, K, &h_alpha, B,
       CUDA_R_16F, ldb, A, CUDA_R_16F, lda, &h_beta, C, CUDA_R_16F, N,
       CUDA_R_32F, algo));
+#else
+  // CUDA 7.5 does not support cublasGemmEx, hence we fall back to use hgemm
+  const half h_alpha = static_cast<const half>(alpha);
+  const half h_beta = static_cast<const half>(beta);
+  const half* h_A = reinterpret_cast<const half*>(A);
+  const half* h_B = reinterpret_cast<const half*>(B);
+  half* h_C = reinterpret_cast<half*>(C);
+
+  PADDLE_ENFORCE(platform::dynload::cublasHgemm(
+      context.cublas_handle(), cuTransB, cuTransA, N, M, K, &h_alpha, h_B, ldb,
+      h_A, lda, &h_beta, h_C, N));
+#endif  // CUDA_VERSION >= 8000
 }
 
 template <>

paddle/fluid/platform/dynload/cublas.cc

@@ -28,6 +28,10 @@ CUBLAS_BLAS_ROUTINE_EACH(DEFINE_WRAP);
 CUBLAS_BLAS_ROUTINE_EACH_R2(DEFINE_WRAP);
 #endif
 
+#ifdef CUBLAS_BLAS_ROUTINE_EACH_R3
+CUBLAS_BLAS_ROUTINE_EACH_R3(DEFINE_WRAP);
+#endif
+
 }  // namespace dynload
 }  // namespace platform
 }  // namespace paddle

paddle/fluid/platform/dynload/cublas.h

@@ -71,7 +71,6 @@ extern void *cublas_dso_handle;
   __macro(cublasDgemm_v2);                \
   __macro(cublasHgemm);                   \
   __macro(cublasSgemmEx);                 \
-  __macro(cublasGemmEx);                  \
   __macro(cublasSgeam_v2);                \
   __macro(cublasDgeam_v2);                \
   __macro(cublasCreate_v2);               \
@@ -83,22 +82,31 @@ extern void *cublas_dso_handle;
   __macro(cublasDgemmBatched);            \
   __macro(cublasCgemmBatched);            \
   __macro(cublasZgemmBatched);            \
-  __macro(cublasSgemmStridedBatched);     \
-  __macro(cublasDgemmStridedBatched);     \
-  __macro(cublasCgemmStridedBatched);     \
-  __macro(cublasZgemmStridedBatched);     \
-  __macro(cublasHgemmStridedBatched);     \
   __macro(cublasSgetrfBatched);           \
   __macro(cublasSgetriBatched);           \
   __macro(cublasDgetrfBatched);           \
   __macro(cublasDgetriBatched);
 
 CUBLAS_BLAS_ROUTINE_EACH(DECLARE_DYNAMIC_LOAD_CUBLAS_WRAP)
 
+// APIs available after CUDA 8.0
+#if CUDA_VERSION >= 8000
+#define CUBLAS_BLAS_ROUTINE_EACH_R2(__macro) \
+  __macro(cublasGemmEx);                     \
+  __macro(cublasSgemmStridedBatched);        \
+  __macro(cublasDgemmStridedBatched);        \
+  __macro(cublasCgemmStridedBatched);        \
+  __macro(cublasZgemmStridedBatched);        \
+  __macro(cublasHgemmStridedBatched);
+
+CUBLAS_BLAS_ROUTINE_EACH_R2(DECLARE_DYNAMIC_LOAD_CUBLAS_WRAP)
+#endif
+
 // APIs available after CUDA 9.0
 #if CUDA_VERSION >= 9000
-#define CUBLAS_BLAS_ROUTINE_EACH_R2(__macro) __macro(cublasSetMathMode);
-CUBLAS_BLAS_ROUTINE_EACH_R2(DECLARE_DYNAMIC_LOAD_CUBLAS_WRAP)
+#define CUBLAS_BLAS_ROUTINE_EACH_R3(__macro) __macro(cublasSetMathMode);
+
+CUBLAS_BLAS_ROUTINE_EACH_R3(DECLARE_DYNAMIC_LOAD_CUBLAS_WRAP)
 #endif
 
 #undef DECLARE_DYNAMIC_LOAD_CUBLAS_WRAP