Add bfloat16 support in RCCL

Preprocessor symbol RCCL_BFLOAT16 is used as feature indicator

src/include/core.h

@@ -48,6 +48,7 @@ static __inline__ int ncclTypeSize(ncclDataType_t type) {
     case ncclUint8:
       return 1;
     case ncclFloat16:
+    case ncclBfloat16:
       return 2;
     case ncclInt32:
     case ncclUint32:

src/include/devcomm.h

@@ -9,6 +9,7 @@
 #define NCCL_DEVICE_H_
 
 #include "nccl.h"
+#include "rccl_bfloat16.h"
 #include <stdint.h>
 
 // Convert volatile access to atomic

src/include/rccl_bfloat16.h

@@ -0,0 +1,253 @@
+/**
+ * MIT License
+ *
+ * Copyright 2019 Advanced Micro Devices, Inc. All rights reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+/*!\file
+ * \brief rccl_bfloat16.h provides struct for rccl_bfloat16 typedef
+ */
+
+#ifndef _RCCL_BFLOAT16_H_
+#define _RCCL_BFLOAT16_H_
+
+#if __cplusplus < 201402L || (!defined(__HCC__) && !defined(__HIPCC__))
+
+// If this is a C compiler, C++ compiler below C++14, or a host-only compiler, we only
+// include a minimal definition of rccl_bfloat16
+
+#include <stdint.h>
+/*! \brief Struct to represent a 16 bit brain floating point number. */
+typedef struct
+{
+    uint16_t data;
+} rccl_bfloat16;
+
+#else // __cplusplus < 201402L || (!defined(__HCC__) && !defined(__HIPCC__))
+
+#include <cmath>
+#include <cstddef>
+#include <cstdint>
+#include <hip/hip_runtime.h>
+#include <ostream>
+#include <type_traits>
+
+struct rccl_bfloat16
+{
+    uint16_t data;
+
+    __host__ __device__ rccl_bfloat16() = default;
+
+    // round upper 16 bits of IEEE float to convert to bfloat16
+    explicit constexpr __host__ __device__ rccl_bfloat16(float f)
+        : data(float_to_bfloat16(f))
+    {
+    }
+
+    // zero extend lower 16 bits of bfloat16 to convert to IEEE float
+    constexpr __host__ __device__ operator float() const
+    {
+        union
+        {
+            uint32_t int32;
+            float    fp32;
+        } u = {uint32_t(data) << 16};
+        return u.fp32;
+    }
+
+private:
+    static constexpr __host__ __device__ uint16_t float_to_bfloat16(float f)
+    {
+        union
+        {
+            float    fp32;
+            uint32_t int32;
+        } u = {f};
+        if(~u.int32 & 0x7f800000)
+        {
+            // When the exponent bits are not all 1s, then the value is zero, normal,
+            // or subnormal. We round the bfloat16 mantissa up by adding 0x7FFF, plus
+            // 1 if the least significant bit of the bfloat16 mantissa is 1 (odd).
+            // This causes the bfloat16's mantissa to be incremented by 1 if the 16
+            // least significant bits of the float mantissa are greater than 0x8000,
+            // or if they are equal to 0x8000 and the least significant bit of the
+            // bfloat16 mantissa is 1 (odd). This causes it to be rounded to even when
+            // the lower 16 bits are exactly 0x8000. If the bfloat16 mantissa already
+            // has the value 0x7f, then incrementing it causes it to become 0x00 and
+            // the exponent is incremented by one, which is the next higher FP value
+            // to the unrounded bfloat16 value. When the bfloat16 value is subnormal
+            // with an exponent of 0x00 and a mantissa of 0x7F, it may be rounded up
+            // to a normal value with an exponent of 0x01 and a mantissa of 0x00.
+            // When the bfloat16 value has an exponent of 0xFE and a mantissa of 0x7F,
+            // incrementing it causes it to become an exponent of 0xFF and a mantissa
+            // of 0x00, which is Inf, the next higher value to the unrounded value.
+            u.int32 += 0x7fff + ((u.int32 >> 16) & 1); // Round to nearest, round to even
+        }
+        else if(u.int32 & 0xffff)
+        {
+            // When all of the exponent bits are 1, the value is Inf or NaN.
+            // Inf is indicated by a zero mantissa. NaN is indicated by any nonzero
+            // mantissa bit. Quiet NaN is indicated by the most significant mantissa
+            // bit being 1. Signaling NaN is indicated by the most significant
+            // mantissa bit being 0 but some other bit(s) being 1. If any of the
+            // lower 16 bits of the mantissa are 1, we set the least significant bit
+            // of the bfloat16 mantissa, in order to preserve signaling NaN in case
+            // the bloat16's mantissa bits are all 0.
+            u.int32 |= 0x10000; // Preserve signaling NaN
+        }
+        return uint16_t(u.int32 >> 16);
+    }
+};
+
+typedef struct
+{
+    uint16_t data;
+} rccl_bfloat16_public;
+
+static_assert(std::is_standard_layout<rccl_bfloat16>{},
+              "rccl_bfloat16 is not a standard layout type, and thus is "
+              "incompatible with C.");
+
+static_assert(std::is_trivial<rccl_bfloat16>{},
+              "rccl_bfloat16 is not a trivial type, and thus is "
+              "incompatible with C.");
+
+static_assert(sizeof(rccl_bfloat16) == sizeof(rccl_bfloat16_public)
+                  && offsetof(rccl_bfloat16, data) == offsetof(rccl_bfloat16_public, data),
+              "internal rccl_bfloat16 does not match public rccl_bfloat16");
+
+inline std::ostream& operator<<(std::ostream& os, const rccl_bfloat16& bf16)
+{
+    return os << float(bf16);
+}
+constexpr __host__ __device__ rccl_bfloat16 operator+(rccl_bfloat16 a)
+{
+    return a;
+}
+constexpr __host__ __device__ rccl_bfloat16 operator-(rccl_bfloat16 a)
+{
+    a.data ^= 0x8000;
+    return a;
+}
+constexpr __host__ __device__ rccl_bfloat16 operator+(rccl_bfloat16 a, rccl_bfloat16 b)
+{
+    return rccl_bfloat16(float(a) + float(b));
+}
+constexpr __host__ __device__ rccl_bfloat16 operator-(rccl_bfloat16 a, rccl_bfloat16 b)
+{
+    return rccl_bfloat16(float(a) - float(b));
+}
+constexpr __host__ __device__ rccl_bfloat16 operator*(rccl_bfloat16 a, rccl_bfloat16 b)
+{
+    return rccl_bfloat16(float(a) * float(b));
+}
+constexpr __host__ __device__ rccl_bfloat16 operator/(rccl_bfloat16 a, rccl_bfloat16 b)
+{
+    return rccl_bfloat16(float(a) / float(b));
+}
+constexpr __host__ __device__ bool operator<(rccl_bfloat16 a, rccl_bfloat16 b)
+{
+    return float(a) < float(b);
+}
+constexpr __host__ __device__ bool operator==(rccl_bfloat16 a, rccl_bfloat16 b)
+{
+    return float(a) == float(b);
+}
+constexpr __host__ __device__ bool operator>(rccl_bfloat16 a, rccl_bfloat16 b)
+{
+    return b < a;
+}
+constexpr __host__ __device__ bool operator<=(rccl_bfloat16 a, rccl_bfloat16 b)
+{
+    return !(a > b);
+}
+constexpr __host__ __device__ bool operator!=(rccl_bfloat16 a, rccl_bfloat16 b)
+{
+    return !(a == b);
+}
+constexpr __host__ __device__ bool operator>=(rccl_bfloat16 a, rccl_bfloat16 b)
+{
+    return !(a < b);
+}
+constexpr __host__ __device__ rccl_bfloat16& operator+=(rccl_bfloat16& a, rccl_bfloat16 b)
+{
+    return a = a + b;
+}
+constexpr __host__ __device__ rccl_bfloat16& operator-=(rccl_bfloat16& a, rccl_bfloat16 b)
+{
+    return a = a - b;
+}
+constexpr __host__ __device__ rccl_bfloat16& operator*=(rccl_bfloat16& a, rccl_bfloat16 b)
+{
+    return a = a * b;
+}
+constexpr __host__ __device__ rccl_bfloat16& operator/=(rccl_bfloat16& a, rccl_bfloat16 b)
+{
+    return a = a / b;
+}
+constexpr __host__ __device__ rccl_bfloat16& operator++(rccl_bfloat16& a)
+{
+    return a += rccl_bfloat16(1.0f);
+}
+constexpr __host__ __device__ rccl_bfloat16& operator--(rccl_bfloat16& a)
+{
+    return a -= rccl_bfloat16(1.0f);
+}
+constexpr __host__ __device__ rccl_bfloat16 operator++(rccl_bfloat16& a, int)
+{
+    rccl_bfloat16 orig = a;
+    ++a;
+    return orig;
+}
+constexpr __host__ __device__ rccl_bfloat16 operator--(rccl_bfloat16& a, int)
+{
+    rccl_bfloat16 orig = a;
+    --a;
+    return orig;
+}
+
+namespace std
+{
+    constexpr __host__ __device__ bool isinf(rccl_bfloat16 a)
+    {
+        return !(~a.data & 0x7f80) && !(a.data & 0x7f);
+    }
+    constexpr __host__ __device__ bool isnan(rccl_bfloat16 a)
+    {
+        return !(~a.data & 0x7f80) && +(a.data & 0x7f);
+    }
+    constexpr __host__ __device__ bool iszero(rccl_bfloat16 a)
+    {
+        return !(a.data & 0x7fff);
+    }
+    inline rccl_bfloat16 sin(rccl_bfloat16 a)
+    {
+        return rccl_bfloat16(sinf(float(a)));
+    }
+    inline rccl_bfloat16 cos(rccl_bfloat16 a)
+    {
+        return rccl_bfloat16(cosf(float(a)));
+    }
+}
+
+#endif // __cplusplus < 201402L || (!defined(__HCC__) && !defined(__HIPCC__))
+
+#endif // _RCCL_BFLOAT16_H_