Merge branch 'github_fused_softmax' into 'main'

Fused softmax checks and additions from Github (#133)

See merge request ADLR/megatron-lm!312

megatron/fused_kernels/scaled_masked_softmax.cpp

@@ -32,6 +32,12 @@ torch::Tensor bwd_cuda(
     torch::Tensor const& softmax_results,
     float scale_factor);
 
+int get_batch_per_block_cuda(
+    int query_seq_len,
+    int key_seq_len,
+    int batches,
+    int attn_heads);
+
 torch::Tensor fwd(
     torch::Tensor const& input,
     torch::Tensor const& mask,
@@ -63,6 +69,14 @@ torch::Tensor bwd(
   return bwd_cuda(output_grads, softmax_results, scale_factor);
 }
 
+int get_batch_per_block(
+    int query_seq_len,
+    int key_seq_len,
+    int batches,
+    int attn_heads) {
+    return get_batch_per_block_cuda(query_seq_len, key_seq_len, batches, attn_heads);
+}
+
 } // end namespace scaled_masked_softmax
 } // end namespace fused_softmax
 } // end namespace multihead_attn
@@ -71,7 +85,13 @@ PYBIND11_MODULE(TORCH_EXTENSION_NAME, m) {
   m.def("forward", 
         &multihead_attn::fused_softmax::scaled_masked_softmax::fwd, 
 	"Self Multihead Attention scaled, time masked softmax -- Forward.");
-  m.def("backward", 
+
+  m.def("backward",
         &multihead_attn::fused_softmax::scaled_masked_softmax::bwd,
 	"Self Multihead Attention scaled, time masked softmax -- Backward.");
+
+  m.def("get_batch_per_block",
+        &multihead_attn::fused_softmax::scaled_masked_softmax::get_batch_per_block,
+        "Return Batch per block size."
+  );
 }

megatron/fused_kernels/scaled_masked_softmax.h

@@ -310,9 +310,22 @@ __global__ void scaled_masked_softmax_warp_backward(
         }
     }
 }
-
 } // end of anonymous namespace
 
+int get_batch_per_block(int query_seq_len, int key_seq_len, int batches, int attn_heads){
+    int log2_elements = log2_ceil(key_seq_len);
+    const int next_power_of_two = 1 << log2_elements;
+
+    int warp_size = (next_power_of_two < C10_WARP_SIZE) ? next_power_of_two : C10_WARP_SIZE;
+    int batches_per_warp = (next_power_of_two <= 128) ? 2 : 1;
+
+    constexpr int threads_per_block = 128;
+    int warps_per_block = (threads_per_block / warp_size);
+    int batches_per_block = warps_per_block * batches_per_warp;
+
+    return batches_per_block;
+}
+
 template<typename input_t, typename output_t, typename acc_t>
 void dispatch_scaled_masked_softmax_forward(
     output_t *dst, 

megatron/fused_kernels/scaled_masked_softmax_cuda.cu

@@ -28,6 +28,11 @@ namespace multihead_attn {
 namespace fused_softmax {
 namespace scaled_masked_softmax {
 
+int get_batch_per_block_cuda(int query_seq_len, int key_seq_len, int batches, int attn_heads){
+    return get_batch_per_block(query_seq_len, key_seq_len, batches, attn_heads);
+}
+
+
 torch::Tensor fwd_cuda(
     torch::Tensor const& input,
     torch::Tensor const& mask,

megatron/fused_kernels/scaled_upper_triang_masked_softmax.h

@@ -361,6 +361,7 @@ void dispatch_scaled_upper_triang_masked_softmax_forward(
         int warps_per_block = (threads_per_block / warp_size);
         int batches_per_block = warps_per_block * batches_per_warp;
         TORCH_INTERNAL_ASSERT(attn_batches % batches_per_block == 0);
+
         int blocks_per_seq = attn_batches / batches_per_block;
         dim3 blocks(seq_len, blocks_per_seq, 1);
         dim3 threads(warp_size, warps_per_block, 1);
@@ -451,6 +452,7 @@ void dispatch_scaled_upper_triang_masked_softmax_backward(
         int warps_per_block = (threads_per_block / warp_size);
         int batches_per_block = warps_per_block * batches_per_warp;
         TORCH_INTERNAL_ASSERT(attn_batches % batches_per_block == 0);
+
         int blocks_per_seq = attn_batches / batches_per_block;
         dim3 blocks(seq_len, blocks_per_seq, 1);
         dim3 threads(warp_size, warps_per_block, 1);

megatron/fused_kernels/tests/test_fused_kernels.py

@@ -0,0 +1,300 @@
+import math
+
+import torch
+from torch.nn import LayerNorm
+
+from megatron.model.enums import AttnMaskType
+from megatron.model.fused_layer_norm import MixedFusedLayerNorm
+from megatron.model.fused_softmax import FusedScaleMaskSoftmax
+from megatron.model.utils import attention_mask_func
+
+
+def test_load_fused_kernels():
+    try:
+        import fused_mix_prec_layer_norm_cuda
+        import scaled_masked_softmax_cuda
+        import scaled_upper_triang_masked_softmax_cuda
+        import torch
+
+        print("[Success] load_fused_kernels")
+    except ImportError as e:
+        print("[Fail] load_fused_kernels")
+        raise e
+
+
+def test_fused_softmax():
+    bert = BertModel.from_pretrained("bert-base-cased").cuda().half()
+    tokenizer = BertTokenizer.from_pretrained("bert-base-cased")
+    test_text = (
+        "Hello. How are you? I am fine thank you and you? yes Good. "
+        "hi hi hi hi hi hi hi hi hi hi hi hi hi"  # 32
+    )
+
+    tokens = tokenizer(
+        [test_text] * 4,
+        return_tensors="pt",
+    )
+
+    embedding_output = bert.embeddings(
+        input_ids=tokens["input_ids"].cuda(),
+        position_ids=None,
+        token_type_ids=tokens["token_type_ids"].cuda(),
+        inputs_embeds=None,
+        past_key_values_length=0,
+    )
+
+    # (bsz, 1, 1, seq_len)
+    mask = bert.get_extended_attention_mask(
+        attention_mask=tokens["attention_mask"].cuda(),
+        input_shape=tokens["input_ids"].shape,
+        device=bert.device,
+    )
+    # (bsz, 1, seq_len, seq_len)
+    mask = mask.repeat(1, 1, mask.size()[-1], 1)
+
+    attention = bert.encoder.layer[0].attention.self
+    key_layer = attention.transpose_for_scores(attention.key(embedding_output))
+    query_layer = attention.transpose_for_scores(attention.query(embedding_output))
+
+    attention_scores = torch.matmul(query_layer, key_layer.transpose(-1, -2))
+    attention_scores /= math.sqrt(key_layer.size()[-1])
+
+    fused_softmax = (
+        FusedScaleMaskSoftmax(
+            input_in_fp16=True,
+            input_in_bf16=False,
+            mask_func=attention_mask_func,
+            scale=None,
+            softmax_in_fp32=False,
+            attn_mask_type=AttnMaskType.padding,
+            scaled_masked_softmax_fusion=True,
+        )
+        .cuda()
+        .half()
+    )
+
+    fused_softmax_output = fused_softmax(
+        attention_scores,
+        (mask != 0),
+    )
+
+    torch_softmax = (
+        FusedScaleMaskSoftmax(
+            input_in_fp16=True,
+            input_in_bf16=False,
+            mask_func=attention_mask_func,
+            scale=None,
+            softmax_in_fp32=False,
+            attn_mask_type=AttnMaskType.padding,
+            scaled_masked_softmax_fusion=False,
+        )
+        .cuda()
+        .half()
+    )
+
+    torch_softmax_output = torch_softmax(
+        attention_scores,
+        (mask != 0),
+    )
+
+    test_result = (fused_softmax_output - torch_softmax_output).abs()
+
+    while test_result.dim() != 1:
+        test_result = test_result.mean(dim=-1)
+
+    diff = test_result.mean(dim=-1)
+
+    if diff <= 1e-3:
+        print(
+            f"\n[Success] test_fused_softmax"
+            f"\n > mean_difference={diff}"
+            f"\n > fused_values={fused_softmax_output[-1][-1][-1][:5].tolist()}"
+            f"\n > torch_values={torch_softmax_output[-1][-1][-1][:5].tolist()}"
+        )
+    else:
+        print(
+            f"\n[Fail] test_fused_softmax"
+            f"\n > mean_difference={diff}, "
+            f"\n > fused_values={fused_softmax_output[-1][-1][-1][:5].tolist()}, "
+            f"\n > torch_values={torch_softmax_output[-1][-1][-1][:5].tolist()}"
+        )
+
+
+def test_fused_upper_triangle_mask_softmax():
+    gpt = GPT2Model.from_pretrained("gpt2").cuda().half()
+    tokenizer = GPT2Tokenizer.from_pretrained("gpt2")
+    test_text = (
+        "Hello. How are you? I am fine thank you and you? yes Good. "
+        "hi hi hi hi hi hi hi"  # 24
+    )
+
+    tokens = tokenizer(
+        [test_text] * 4,
+        return_tensors="pt",
+    )
+
+    attention_mask = tokens["attention_mask"].cuda()
+    attention_mask = attention_mask.view(attention_mask.size(0), -1)
+    attention_mask = attention_mask[:, None, None, :]
+    attention_mask = (1.0 - attention_mask) * -10000.0
+    attention_mask = attention_mask.repeat(1, 1, attention_mask.size()[-1], 1)
+    attn = gpt.h[0]
+
+    hidden_states = gpt.wte(tokens["input_ids"].cuda())
+    q, k, v = attn.attn.c_attn(hidden_states).split(768, dim=-1)
+    q = attn.attn._split_heads(q, attn.attn.num_heads, attn.attn.head_dim)
+    k = attn.attn._split_heads(k, attn.attn.num_heads, attn.attn.head_dim)
+    attn_weights = torch.matmul(q, k.transpose(-1, -2))
+
+    sq, sk = q.size(-2), k.size(-2)
+    causal_mask = attn.attn.bias[:, :, sk - sq : sk, :sk].bool()
+    total_mask = ~(causal_mask & (attention_mask == 0))
+    """
+    tensor([[[[False,  True,  True,  ...,  True,  True,  True],
+              [False, False,  True,  ...,  True,  True,  True],
+              [False, False, False,  ...,  True,  True,  True],
+              ...,
+              [False, False, False,  ..., False,  True,  True],
+              [False, False, False,  ..., False, False,  True],
+              [False, False, False,  ..., False, False, False]]]
+    """
+
+    fused_softmax = (
+        FusedScaleMaskSoftmax(
+            input_in_fp16=True,
+            input_in_bf16=False,
+            mask_func=attention_mask_func,
+            scale=None,
+            softmax_in_fp32=False,
+            attn_mask_type=AttnMaskType.causal,
+            scaled_masked_softmax_fusion=True,
+        )
+        .cuda()
+        .half()
+    )
+
+    fused_softmax_output = fused_softmax(
+        attn_weights,
+        total_mask,
+    )
+
+    torch_softmax = (
+        FusedScaleMaskSoftmax(
+            input_in_fp16=True,
+            input_in_bf16=False,
+            mask_func=attention_mask_func,
+            scale=None,
+            softmax_in_fp32=False,
+            attn_mask_type=AttnMaskType.causal,
+            scaled_masked_softmax_fusion=False,
+        )
+        .cuda()
+        .half()
+    )
+
+    torch_softmax_output = torch_softmax(
+        attn_weights,
+        total_mask,
+    )
+
+    test_result = (fused_softmax_output - torch_softmax_output).abs()
+
+    while test_result.dim() != 1:
+        test_result = test_result.mean(dim=-1)
+
+    diff = test_result.mean(dim=-1)
+
+    if diff <= 1e-3:
+        print(
+            f"\n[Success] test_fused_upper_triangle_mask_softmax"
+            f"\n > mean_difference={diff}"
+            f"\n > fused_values={fused_softmax_output[-1][-1][-1][:5].tolist()}"
+            f"\n > torch_values={torch_softmax_output[-1][-1][-1][:5].tolist()}"
+        )
+    else:
+        print(
+            f"\n[Fail] test_fused_upper_triangle_mask_softmax"
+            f"\n > mean_difference={diff}, "
+            f"\n > fused_values={fused_softmax_output[-1][-1][-1][:5].tolist()}, "
+            f"\n > torch_values={torch_softmax_output[-1][-1][-1][:5].tolist()}"
+        )
+
+
+def test_layer_norm():
+    bert = BertModel.from_pretrained("bert-base-cased").cuda().half()
+    tokenizer = BertTokenizer.from_pretrained("bert-base-cased")
+    test_text = (
+        "Hello. How are you? I am fine thank you and you? yes Good. "
+        "hi hi hi hi hi hi hi hi hi hi hi hi hi"  # 32
+    )
+
+    tokens = tokenizer(
+        [test_text] * 4,
+        return_tensors="pt",
+    )
+
+    # [bsz, seq_len, d_model]
+    embedding_output = (
+        bert.embeddings(
+            input_ids=tokens["input_ids"].cuda(),
+            position_ids=None,
+            token_type_ids=tokens["token_type_ids"].cuda(),
+            inputs_embeds=None,
+            past_key_values_length=0,
+        )
+        .cuda()
+        .half()
+    )
+
+    fused_layernorm_layer = (
+        MixedFusedLayerNorm(normalized_shape=embedding_output.size(-1)).cuda().half()
+    )
+
+    torch_layernorm_layer = (
+        LayerNorm(normalized_shape=embedding_output.size(-1)).cuda().half()
+    )
+
+    fused_output = fused_layernorm_layer(embedding_output)
+    torch_output = torch_layernorm_layer(embedding_output)
+    test_result = (fused_output - torch_output).abs()
+
+    while test_result.dim() != 1:
+        test_result = test_result.mean(dim=-1)
+
+    diff = test_result.mean(dim=-1)
+
+    if diff <= 1e-3:
+        print(
+            f"\n[Success] test_layer_norm"
+            f"\n > mean_difference={diff}"
+            f"\n > fused_values={fused_output[-1][-1][:5].tolist()}"
+            f"\n > torch_values={torch_output[-1][-1][:5].tolist()}"
+        )
+    else:
+        print(
+            f"\n[Fail] test_layer_norm"
+            f"\n > mean_difference={diff}, "
+            f"\n > fused_values={fused_output[-1][-1][:5].tolist()}, "
+            f"\n > torch_values={torch_output[-1][-1][:5].tolist()}"
+        )
+
+
+if __name__ == "__main__":
+    try:
+        from transformers import BertTokenizer, GPT2Tokenizer
+        from transformers.models.bert.modeling_bert import BertModel
+        from transformers.models.gpt2.modeling_gpt2 import GPT2Model
+        import transformers
+
+        transformers.logging.set_verbosity(
+            transformers.logging.FATAL,
+        )
+
+    except:
+        print("\n[Fail] Please install `transformers` package to test fused kernels\n")
+        exit(-1)
+
+    test_load_fused_kernels()
+    test_fused_softmax()
+    test_fused_upper_triangle_mask_softmax()
+    test_layer_norm()