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TheRock/rocm-libraries/projects/hipdnn/frontend/include/hipdnn_frontend/node/SdpaBwdNode.hpp
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derek.holloway 7502bf64a4
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Flatten subprojects into a single base monorepo
2026-09-02 16:34:47 -07:00

424 lines
20 KiB
C++

// Copyright © Advanced Micro Devices, Inc., or its affiliates.
// SPDX-License-Identifier: MIT
#pragma once
#include "Node.hpp"
#include <hipdnn_data_sdk/utilities/ShapeUtilities.hpp>
#include <hipdnn_frontend/Error.hpp>
#include <hipdnn_frontend/attributes/GraphAttributes.hpp>
#include <hipdnn_frontend/attributes/SdpaBackwardAttributes.hpp>
#include <hipdnn_frontend/detail/ScopedHipdnnBackendDescriptor.hpp>
#include <hipdnn_frontend/detail/SdpaBwdPacker.hpp>
#include <hipdnn_frontend/detail/SdpaBwdUnpacker.hpp>
#include <hipdnn_frontend/node/detail/Utilities.hpp>
namespace hipdnn_frontend::graph
{
/**
* @class SdpaBwdNode
* @brief Node implementing scaled dot-product attention backward pass
*
* Computes gradients dQ, dK, dV given:
* - Forward inputs Q, K, V, O
* - Upstream gradient dO
* - Softmax statistics (logsumexp) from the forward pass
*
* The backward pass uses the flash attention algorithm to compute:
* dV = softmax(Q * K^T / sqrt(d_k))^T * dO
* dP = dO * V^T (where P = softmax(Q * K^T / sqrt(d_k)))
* dS = P * (dP - rowsum(dO * O))
* dQ = dS * K / sqrt(d_k)
* dK = dS^T * Q / sqrt(d_k)
*/
class SdpaBwdNode : public BaseNode<SdpaBwdNode, NodeType::SDPA_BWD>
{
public:
SdpaBackwardAttributes attributes;
SdpaBwdNode(SdpaBackwardAttributes&& sdpaAttrs, const GraphAttributes& graphAttrs)
: BaseNode(graphAttrs)
, attributes(std::move(sdpaAttrs))
{
}
Error pre_validate_node() const override
{
HIPDNN_RETURN_IF_TRUE(attributes.hasUnsupportedUsage(),
ErrorCode::INVALID_VALUE,
attributes.getUnsupportedReason());
const auto q = attributes.get_q();
const auto k = attributes.get_k();
const auto v = attributes.get_v();
const auto o = attributes.get_o();
const auto dOut = attributes.get_do();
const auto stats = attributes.get_stats();
const auto dq = attributes.get_dq();
const auto dk = attributes.get_dk();
const auto dv = attributes.get_dv();
// Validate required input tensors
HIPDNN_RETURN_IF_FALSE(
q, ErrorCode::ATTRIBUTE_NOT_SET, std::string("SdpaBwdNode missing Q input"));
HIPDNN_RETURN_IF_FALSE(
k, ErrorCode::ATTRIBUTE_NOT_SET, std::string("SdpaBwdNode missing K input"));
HIPDNN_RETURN_IF_FALSE(
v, ErrorCode::ATTRIBUTE_NOT_SET, std::string("SdpaBwdNode missing V input"));
HIPDNN_RETURN_IF_FALSE(
o, ErrorCode::ATTRIBUTE_NOT_SET, std::string("SdpaBwdNode missing O input"));
HIPDNN_RETURN_IF_FALSE(
dOut, ErrorCode::ATTRIBUTE_NOT_SET, std::string("SdpaBwdNode missing dO input"));
HIPDNN_RETURN_IF_FALSE(
stats, ErrorCode::ATTRIBUTE_NOT_SET, std::string("SdpaBwdNode missing Stats input"));
// Validate required output tensors
HIPDNN_RETURN_IF_FALSE(
dq, ErrorCode::ATTRIBUTE_NOT_SET, std::string("SdpaBwdNode missing dQ output"));
HIPDNN_RETURN_IF_FALSE(
dk, ErrorCode::ATTRIBUTE_NOT_SET, std::string("SdpaBwdNode missing dK output"));
HIPDNN_RETURN_IF_FALSE(
dv, ErrorCode::ATTRIBUTE_NOT_SET, std::string("SdpaBwdNode missing dV output"));
const auto& qDims = q->get_dim();
const auto& kDims = k->get_dim();
const auto& vDims = v->get_dim();
// Rule 1: Q, K, V must be exactly rank-4
const size_t reqRank = 4;
HIPDNN_RETURN_IF_NE(qDims.size(),
reqRank,
ErrorCode::INVALID_VALUE,
"SdpaBwdNode: Query tensor Q must be rank-4, got rank="
+ std::to_string(qDims.size()));
HIPDNN_RETURN_IF_NE(kDims.size(),
reqRank,
ErrorCode::INVALID_VALUE,
"SdpaBwdNode: Key tensor K must be rank-4, got rank="
+ std::to_string(kDims.size()));
HIPDNN_RETURN_IF_NE(vDims.size(),
reqRank,
ErrorCode::INVALID_VALUE,
"SdpaBwdNode: Value tensor V must be rank-4, got rank="
+ std::to_string(vDims.size()));
// Rule 2: batch size consistency
HIPDNN_RETURN_IF_NE(qDims[0],
kDims[0],
ErrorCode::INVALID_VALUE,
"SdpaBwdNode: batch size mismatch between Q and K: "
+ std::to_string(qDims[0]) + " vs " + std::to_string(kDims[0]));
HIPDNN_RETURN_IF_NE(qDims[0],
vDims[0],
ErrorCode::INVALID_VALUE,
"SdpaBwdNode: batch size mismatch between Q and V: "
+ std::to_string(qDims[0]) + " vs " + std::to_string(vDims[0]));
// Rule 3: head_dim: Q[-1] == K[-1]
const auto headDimQ = qDims[3];
const auto headDimK = kDims[3];
HIPDNN_RETURN_IF_NE(headDimQ,
headDimK,
ErrorCode::INVALID_VALUE,
"SdpaBwdNode: head_dim mismatch between Q and K: "
+ std::to_string(headDimQ) + " vs " + std::to_string(headDimK));
// Rule 4: seq_kv: K[-2] == V[-2]
const auto seqKvK = kDims[2];
const auto seqKvV = vDims[2];
HIPDNN_RETURN_IF_NE(seqKvK,
seqKvV,
ErrorCode::INVALID_VALUE,
"SdpaBwdNode: seq_kv mismatch between K and V: "
+ std::to_string(seqKvK) + " vs " + std::to_string(seqKvV));
// Rule 5: num_heads % K_heads == 0; num_heads % V_heads == 0 (GQA/MQA)
const auto numHeads = qDims[1];
const auto numHeadsK = kDims[1];
const auto numHeadsV = vDims[1];
HIPDNN_RETURN_IF_TRUE(numHeadsK <= 0,
ErrorCode::INVALID_VALUE,
"SdpaBwdNode: num_heads_k must be positive, got "
+ std::to_string(numHeadsK));
HIPDNN_RETURN_IF_TRUE(numHeads % numHeadsK != 0,
ErrorCode::INVALID_VALUE,
"SdpaBwdNode: num_heads must be divisible by num_heads_k for "
"GQA/MQA. num_heads="
+ std::to_string(numHeads)
+ ", num_heads_k=" + std::to_string(numHeadsK));
HIPDNN_RETURN_IF_TRUE(numHeadsV <= 0,
ErrorCode::INVALID_VALUE,
"SdpaBwdNode: num_heads_v must be positive, got "
+ std::to_string(numHeadsV));
HIPDNN_RETURN_IF_TRUE(numHeads % numHeadsV != 0,
ErrorCode::INVALID_VALUE,
"SdpaBwdNode: num_heads must be divisible by num_heads_v for "
"GQA/MQA. num_heads="
+ std::to_string(numHeads)
+ ", num_heads_v=" + std::to_string(numHeadsV));
// Rule 6: dO must match O shape [batch, num_heads, seq_q, head_dim_v]
const auto& oDims = o->get_dim();
if(!oDims.empty())
{
const auto& dOutDims = dOut->get_dim();
if(!dOutDims.empty())
{
HIPDNN_RETURN_IF_NE(dOutDims.size(),
reqRank,
ErrorCode::INVALID_VALUE,
"SdpaBwdNode: dO must be rank-4, got rank="
+ std::to_string(dOutDims.size()));
HIPDNN_RETURN_IF_NE(dOutDims[0],
oDims[0],
ErrorCode::INVALID_VALUE,
"SdpaBwdNode: dO batch mismatch with O");
HIPDNN_RETURN_IF_NE(dOutDims[1],
oDims[1],
ErrorCode::INVALID_VALUE,
"SdpaBwdNode: dO num_heads mismatch with O");
HIPDNN_RETURN_IF_NE(dOutDims[2],
oDims[2],
ErrorCode::INVALID_VALUE,
"SdpaBwdNode: dO seq_q mismatch with O");
HIPDNN_RETURN_IF_NE(dOutDims[3],
oDims[3],
ErrorCode::INVALID_VALUE,
"SdpaBwdNode: dO head_dim mismatch with O");
}
}
// Rule 7: Optional attention mask validation
const auto attnMask = attributes.get_bias();
if(attnMask)
{
const auto& maskDims = attnMask->get_dim();
const auto maskRank = maskDims.size();
HIPDNN_RETURN_IF_TRUE(maskRank > static_cast<size_t>(4),
ErrorCode::INVALID_VALUE,
"SdpaBwdNode: ATTN_MASK rank must be <= 4, got rank="
+ std::to_string(maskRank));
const auto seqQ = qDims[2];
const auto seqKv = kDims[2];
const auto maskLast = maskDims[maskRank - 1];
HIPDNN_RETURN_IF_TRUE(maskLast != seqKv && maskLast != 1,
ErrorCode::INVALID_VALUE,
"SdpaBwdNode: ATTN_MASK last dim must equal seq_kv ("
+ std::to_string(seqKv) + ") or 1, got "
+ std::to_string(maskLast));
if(maskRank >= 2)
{
const auto maskSecondLast = maskDims[maskRank - 2];
HIPDNN_RETURN_IF_TRUE(maskSecondLast != seqQ && maskSecondLast != 1,
ErrorCode::INVALID_VALUE,
"SdpaBwdNode: ATTN_MASK second-to-last dim must equal "
"seq_q ("
+ std::to_string(seqQ) + ") or 1, got "
+ std::to_string(maskSecondLast));
}
}
// Rule 8: Optional dropout mask validation
// Shape must be rank-4 (B or 1, H_q or 1, S_q, S_kv) — last two dims are exact,
// first two dims may broadcast (1 allowed).
const auto dropoutMask = attributes.get_dropout_mask();
if(dropoutMask)
{
const auto& dmDims = dropoutMask->get_dim();
HIPDNN_RETURN_IF_NE(dmDims.size(),
static_cast<size_t>(4),
ErrorCode::INVALID_VALUE,
"SdpaBwdNode: DROPOUT_MASK must be rank-4, got rank="
+ std::to_string(dmDims.size()));
const auto seqQ = qDims[2];
const auto seqKv = kDims[2];
const auto batch = qDims[0];
HIPDNN_RETURN_IF_TRUE(dmDims[0] != batch && dmDims[0] != 1,
ErrorCode::INVALID_VALUE,
"SdpaBwdNode: DROPOUT_MASK dim[0] must equal batch ("
+ std::to_string(batch) + ") or 1, got "
+ std::to_string(dmDims[0]));
HIPDNN_RETURN_IF_TRUE(dmDims[1] != numHeads && dmDims[1] != 1,
ErrorCode::INVALID_VALUE,
"SdpaBwdNode: DROPOUT_MASK dim[1] must equal num_heads ("
+ std::to_string(numHeads) + ") or 1, got "
+ std::to_string(dmDims[1]));
HIPDNN_RETURN_IF_NE(dmDims[2],
seqQ,
ErrorCode::INVALID_VALUE,
"SdpaBwdNode: DROPOUT_MASK dim[2] must equal seq_q ("
+ std::to_string(seqQ) + "), got " + std::to_string(dmDims[2]));
HIPDNN_RETURN_IF_NE(dmDims[3],
seqKv,
ErrorCode::INVALID_VALUE,
"SdpaBwdNode: DROPOUT_MASK dim[3] must equal seq_kv ("
+ std::to_string(seqKv) + "), got "
+ std::to_string(dmDims[3]));
}
// Rule 9: Padding mask — when padding_mask=true, seq_len_q and seq_len_kv must
// be provided as rank-4 tensors with shape (B, 1, 1, 1) and INT32 data type.
if(attributes.padding_mask)
{
const auto seqLenQ = attributes.get_seq_len_q();
const auto seqLenKv = attributes.get_seq_len_kv();
HIPDNN_RETURN_IF_FALSE(
seqLenQ,
ErrorCode::ATTRIBUTE_NOT_SET,
std::string("SdpaBwdNode: padding_mask=true requires seq_len_q tensor to be set"));
HIPDNN_RETURN_IF_FALSE(
seqLenKv,
ErrorCode::ATTRIBUTE_NOT_SET,
std::string("SdpaBwdNode: padding_mask=true requires seq_len_kv tensor to be set"));
const auto& sqDims = seqLenQ->get_dim();
const auto& skvDims = seqLenKv->get_dim();
const auto batch = qDims[0];
HIPDNN_RETURN_IF_NE(sqDims.size(),
static_cast<size_t>(4),
ErrorCode::INVALID_VALUE,
"SdpaBwdNode: seq_len_q must be rank-4, got rank="
+ std::to_string(sqDims.size()));
HIPDNN_RETURN_IF_NE(sqDims[0],
batch,
ErrorCode::INVALID_VALUE,
"SdpaBwdNode: seq_len_q dim[0] must equal batch ("
+ std::to_string(batch) + "), got "
+ std::to_string(sqDims[0]));
HIPDNN_RETURN_IF_NE(sqDims[1],
static_cast<int64_t>(1),
ErrorCode::INVALID_VALUE,
"SdpaBwdNode: seq_len_q dim[1] must be 1, got "
+ std::to_string(sqDims[1]));
HIPDNN_RETURN_IF_NE(sqDims[2],
static_cast<int64_t>(1),
ErrorCode::INVALID_VALUE,
"SdpaBwdNode: seq_len_q dim[2] must be 1, got "
+ std::to_string(sqDims[2]));
HIPDNN_RETURN_IF_NE(sqDims[3],
static_cast<int64_t>(1),
ErrorCode::INVALID_VALUE,
"SdpaBwdNode: seq_len_q dim[3] must be 1, got "
+ std::to_string(sqDims[3]));
HIPDNN_RETURN_IF_TRUE(seqLenQ->get_data_type() != DataType::INT32,
ErrorCode::INVALID_VALUE,
std::string("SdpaBwdNode: seq_len_q must have INT32 data "
"type"));
HIPDNN_RETURN_IF_NE(skvDims.size(),
static_cast<size_t>(4),
ErrorCode::INVALID_VALUE,
"SdpaBwdNode: seq_len_kv must be rank-4, got rank="
+ std::to_string(skvDims.size()));
HIPDNN_RETURN_IF_NE(skvDims[0],
batch,
ErrorCode::INVALID_VALUE,
"SdpaBwdNode: seq_len_kv dim[0] must equal batch ("
+ std::to_string(batch) + "), got "
+ std::to_string(skvDims[0]));
HIPDNN_RETURN_IF_NE(skvDims[1],
static_cast<int64_t>(1),
ErrorCode::INVALID_VALUE,
"SdpaBwdNode: seq_len_kv dim[1] must be 1, got "
+ std::to_string(skvDims[1]));
HIPDNN_RETURN_IF_NE(skvDims[2],
static_cast<int64_t>(1),
ErrorCode::INVALID_VALUE,
"SdpaBwdNode: seq_len_kv dim[2] must be 1, got "
+ std::to_string(skvDims[2]));
HIPDNN_RETURN_IF_NE(skvDims[3],
static_cast<int64_t>(1),
ErrorCode::INVALID_VALUE,
"SdpaBwdNode: seq_len_kv dim[3] must be 1, got "
+ std::to_string(skvDims[3]));
HIPDNN_RETURN_IF_TRUE(seqLenKv->get_data_type() != DataType::INT32,
ErrorCode::INVALID_VALUE,
std::string("SdpaBwdNode: seq_len_kv must have INT32 data "
"type"));
}
// Rule 10: attn_scale may be given as a tensor or a baked value, not both
const auto scale = attributes.get_attn_scale();
HIPDNN_RETURN_IF_TRUE(
scale && attributes.attn_scale_value.has_value(),
ErrorCode::INVALID_VALUE,
"SdpaBwdNode: attn_scale tensor and attn_scale_value cannot both be set");
// Rule 10b: Optional attention scale must be a scalar tensor
if(scale)
{
HIPDNN_CHECK_ERROR(detail::validateScalarParameter(scale, "SCALE tensor"));
}
return {};
}
Error infer_properties_node() override
{
const auto q = attributes.get_q();
const auto k = attributes.get_k();
const auto v = attributes.get_v();
const auto dq = attributes.get_dq();
const auto dk = attributes.get_dk();
const auto dv = attributes.get_dv();
HIPDNN_CHECK_ERROR(attributes.fill_from_context(graph_attributes));
// dQ has same shape as Q: [batch, num_heads, seq_q, head_dim]
if(dq->get_dim().empty())
{
dq->set_dim(q->get_dim());
}
if(dq->get_stride().empty())
{
dq->set_stride(hipdnn_data_sdk::utilities::generateStrides(dq->get_dim()));
}
// dK has same shape as K: [batch, num_kv_heads, seq_kv, head_dim]
if(dk->get_dim().empty())
{
dk->set_dim(k->get_dim());
}
if(dk->get_stride().empty())
{
dk->set_stride(hipdnn_data_sdk::utilities::generateStrides(dk->get_dim()));
}
// dV has same shape as V: [batch, num_kv_heads, seq_kv, head_dim_v]
if(dv->get_dim().empty())
{
dv->set_dim(v->get_dim());
}
if(dv->get_stride().empty())
{
dv->set_stride(hipdnn_data_sdk::utilities::generateStrides(dv->get_dim()));
}
return {};
}
Error create_operation(
std::unordered_map<int64_t, detail::ScopedHipdnnBackendDescriptor>& tensorDescs,
std::vector<detail::ScopedHipdnnBackendDescriptor>& operations) const override
{
return detail::createSdpaBwdOperation(attributes, tensorDescs, operations);
}
Error unpack_from_descriptor(
hipdnnBackendDescriptor_t opDesc,
std::unordered_map<int64_t, std::shared_ptr<TensorAttributes>>& tensorMap) override
{
SdpaBackwardAttributes sdpaAttr;
HIPDNN_CHECK_ERROR(detail::unpackSdpaBwdOperation(opDesc, tensorMap, sdpaAttr));
attributes = std::move(sdpaAttr);
return {};
}
};
} // namespace hipdnn_frontend::graph