FP8 splitgemm user defined triton kernel (pytorch#263)

* FP8 splitgemm user defined triton kernel

* yolo

* Trigger CI

* yolo

* yolo

* yolo

* yolo

* Update test_fp8.py

test/dtypes/test_fp8.py

@@ -0,0 +1,45 @@
+import os
+import unittest
+import torch
+from torch.testing._internal.common_utils import (
+    TestCase,
+    instantiate_parametrized_tests,
+    parametrize,
+    run_tests,
+)
+from torchao.quantization.utils import TORCH_VERSION_AFTER_2_4
+try:
+    from torchao.prototype.fp8 import gemm_split_k
+    triton_available = True
+except ImportError:
+    triton_available = False
+
+@unittest.skipIf(not triton_available, "Triton is required but not available")
+@unittest.skipIf(not torch.cuda.is_available(), "CUDA is required")
+class TestFP8Gemm(TestCase):
+    # @parametrize("dtype", [torch.bfloat16, torch.float16, torch.float32])
+    def test_gemm_split_k(self):
+        m, n, k = 256, 256, 512
+
+        a = torch.randn((m, k), dtype=torch.float16, device="cuda")
+        b = torch.randn((k, n), dtype=torch.float16, device="cuda")
+        c = gemm_split_k(a, b)
+        c_expected = torch.matmul(a, b)
+        assert torch.allclose(c, c_expected, atol=0.07) # less than this and the accuracy check fails
+
+    # https://pytorch.org/tutorials/recipes/torch_compile_user_defined_triton_kernel_tutorial.html
+    @unittest.skip("fp8 kernel compilation does not work on a10g")
+    def test_user_defined_triton_function(self):
+        import torch._inductor.config
+        torch._inductor.config.force_disable_caches = True
+        os.environ['TORCHINDUCTOR_COMPILE_THREADS'] = '1'
+        m, n, k = 256, 256, 512
+
+        a = torch.randn((m, k), dtype=torch.float16, device="cuda")
+        b = torch.randn((k, n), dtype=torch.float16, device="cuda")
+        compiled_function = torch.compile(gemm_split_k, fullgraph=True)(a,b)
+
+
+
+if __name__ == "__main__":
+    run_tests()

torchao/prototype/fp8/__init__.py

@@ -0,0 +1 @@
+from .splitk_gemm import gemm_split_k

torchao/prototype/fp8/splitk_gemm.py

@@ -0,0 +1,119 @@
+# Code from https://github.com/pytorch-labs/applied-ai/blob/main/kernels/triton/inference/fp8/splitk_gemm_fp8.py
+import torch
+import triton
+import triton.language as tl
+
+@triton.jit
+def grouped_launch(pid,
+                m, n,
+                block_m: tl.constexpr, block_n: tl.constexpr, group_m: tl.constexpr):
+
+    grid_m = tl.cdiv(m, block_m)
+    grid_n = tl.cdiv(n, block_n)
+
+    width = group_m * grid_n
+    group_id = pid // width
+    group_size = tl.minimum(grid_m - group_id * group_m, group_m)
+
+    pid_m = group_id * group_m + (pid % group_size)
+    pid_n = (pid % width) // group_size
+
+    return pid_m, pid_n
+
+
+@triton.jit()
+def col_major(pid,
+              m, n,
+              block_m: tl.constexpr, block_n: tl.constexpr):
+
+    grid_m = tl.cdiv(m, block_m)
+
+    pid_m = pid % grid_m
+    pid_n = pid // grid_m
+
+    return pid_m, pid_n
+
+
+@triton.jit
+def gemm_split_k_kernel(a_ptr, b_ptr, c_ptr,
+            stride_am, stride_ak,
+            stride_bk, stride_bn,
+            stride_cm, stride_cn,
+            m, n, k,
+            block_m: tl.constexpr, block_n: tl.constexpr, block_k: tl.constexpr,
+            split_k: tl.constexpr, group_m: tl.constexpr):
+
+    pid = tl.program_id(0)
+    pid_k = tl.program_id(1)
+    grid_k = tl.cdiv(k, block_k*split_k)
+
+    pid_m, pid_n = grouped_launch(pid,
+                                  m, n,
+                                  block_m, block_n, group_m)
+
+    offs_m = pid_m*block_m + tl.arange(0, block_m)
+    offs_n = pid_n*block_n + tl.arange(0, block_n)
+    offs_k = pid_k*block_k + tl.arange(0, block_k)
+
+    offs_am = tl.max_contiguous(tl.multiple_of(offs_m, block_m), block_m)
+    offs_bn = tl.max_contiguous(tl.multiple_of(offs_n, block_n), block_n)
+
+    a_ptrs = a_ptr + (offs_am[:, None] * stride_am + offs_k[None, :] * stride_ak)
+    b_ptrs = b_ptr + (offs_k[:, None] * stride_bk + offs_bn[None, :] * stride_bn)
+
+    acc = tl.zeros((block_m, block_n), dtype=tl.float32)
+    for k_ in range(0, grid_k):
+
+        k_remaining = k - k_ * (block_k * split_k)
+
+        a = tl.load(a_ptrs, mask=offs_k[None, :] < k_remaining, other=0.0)
+        b = tl.load(b_ptrs, mask=offs_k[:, None] < k_remaining, other=0.0)
+
+        acc = tl.dot(a, b, acc, out_dtype=tl.float32)
+
+        a_ptrs += block_k * split_k * stride_ak
+        b_ptrs += block_k * split_k * stride_bk
+
+    acc = acc.to(tl.float16)
+
+    offs_m = pid_m*block_m + tl.arange(0, block_m)
+    offs_n = pid_n*block_n + tl.arange(0, block_n)
+
+    c_ptrs = c_ptr + (offs_m[:, None] * stride_cm + offs_n[None, :] * stride_cn)
+    mask = (offs_m < m)[:, None] & (offs_n < n)[None, :]
+
+    tl.atomic_add(c_ptrs, acc, mask=mask)
+
+def gemm_split_k(a, b):
+
+    m, k = a.shape
+    _, n = b.shape
+
+    # Need to change these otherwise was getting
+    # triton.runtime.errors.OutOfResources: out of resource: shared memory, Required: 393216, Hardware limit: 232448. Reducing block sizes or `num_stages` may help.
+    # TODO: Should we tune this differently for different hardware?
+    block_m = 32
+    block_n = 32
+    block_k = 256
+    num_stages = 2
+    num_warps = 4
+    split_k = 4
+    group_m = 8
+
+    total_blocks_m = triton.cdiv(m, block_m)
+    total_blocks_n = triton.cdiv(n, block_n)
+    total_programs_mn = total_blocks_m * total_blocks_n
+    total_programs_k = split_k
+
+    grid = (total_programs_mn, total_programs_k)
+
+    c = torch.zeros((m, n), device=a.device, dtype=torch.float16)
+    gemm_split_k_kernel[grid](a, b, c,
+                              a.stride(0), a.stride(1),
+                              b.stride(0), b.stride(1),
+                              c.stride(0), c.stride(1),
+                              m, n, k,
+                              block_m, block_n, block_k,
+                              split_k, group_m, num_stages=num_stages, num_warps=num_warps)
+
+    return c

torchao/quantization/utils.py

@@ -99,6 +99,7 @@ def get_model_size_in_bytes(model):
         s += b.nelement() * b.element_size()
     return s
 
+# TODO: quantization namespace is not the right place ot have this
 if version.parse(torch.__version__) >= version.parse("2.4.0.dev"):
     TORCH_VERSION_AFTER_2_4 = True
 else: