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gemma.cpp/gemma/activations.h

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// Copyright 2024 Google LLC
// SPDX-License-Identifier: Apache-2.0
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#ifndef THIRD_PARTY_GEMMA_CPP_GEMMA_ACTIVATIONS_H_
#define THIRD_PARTY_GEMMA_CPP_GEMMA_ACTIVATIONS_H_
#include <math.h> // sqrtf
#include <stddef.h>
#include <stdint.h>
#include <atomic>
#include <vector>
#include "gemma/configs.h" // ModelConfig
#include "ops/ops.h" // CreateInvTimescale
#include "util/basics.h" // BF16
#include "util/mat.h" // MatStorageT
#include "util/threading_context.h"
namespace gcpp {
// Returns the scale value to use for the query in the attention computation.
// Also called by ops_test.
static inline float ChooseQueryScale(const ModelConfig& config) {
const LayerConfig& layer_config = config.layer_configs[0];
if (config.query_scale == QueryScaleType::SqrtModelDimDivNumHeads)
return 1.0f /
sqrtf(static_cast<float>(config.model_dim / layer_config.heads));
// QueryScaleType::SqrtKeySize
return 1.0f / sqrtf(static_cast<float>(layer_config.qkv_dim));
}
struct AttentionActivations {
AttentionActivations(
const ModelConfig& config, const LayerConfig& layer_config,
size_t batch_size, size_t seq_len, const Allocator& allocator,
std::vector<hwy::AlignedFreeUniquePtr<uint8_t*[]>>& row_ptrs)
: // `vocab_size == 0` means it is for Vit part, VitAttention is still
// MHA and does not use an external KV cache.
q(MatFactory("q", batch_size,
config.vocab_size == 0
? layer_config.heads * 3 * layer_config.qkv_dim
: layer_config.heads * layer_config.qkv_dim,
allocator)),
q_T(MatFactory("q_T", layer_config.qkv_dim,
config.vocab_size == 0
? batch_size * layer_config.heads * 3
: batch_size * layer_config.heads,
allocator)),
pre_att_rms_out(MatFactory("pre_att_rms_out", batch_size,
config.model_dim, allocator)),
att(MatFactory("att", batch_size, layer_config.heads * seq_len,
allocator)),
att_out(MatFactory("att_out", batch_size,
layer_config.heads * layer_config.qkv_dim,
allocator)),
att_sums(
MatFactory("att_sums", batch_size, config.model_dim, allocator)),
inv_timescale(
CreateInvTimescale(allocator, layer_config.qkv_dim,
layer_config.post_qk == PostQKType::HalfRope)),
inv_timescale_global(CreateInvTimescale(
allocator, layer_config.qkv_dim,
layer_config.post_qk == PostQKType::HalfRope, 1000000.0)) {
// Batch size can be 0 in experimental code so do not assert.
if (batch_size == 0) {
static std::atomic_flag warned = ATOMIC_FLAG_INIT;
if (!warned.test_and_set()) {
HWY_WARN("Creating mostly empty activations with a batch_size of 0.");
}
return;
}
// For MatMul outputs, precompute their row pointers.
// If we forget any MatMul outputs here, debug builds print a warning but
// fill them in each MatMul call.
q.AllocateAndAttachRowPtrs(row_ptrs);
q_T.AllocateAndAttachRowPtrs(row_ptrs);
att_sums.AllocateAndAttachRowPtrs(row_ptrs);
}
void SetBatchSize(size_t batch_size) {
q.OverrideRows(batch_size);
// q_T rows are always qkv_dim!
pre_att_rms_out.OverrideRows(batch_size);
att.OverrideRows(batch_size);
att_out.OverrideRows(batch_size);
att_sums.OverrideRows(batch_size);
}
MatStorageT<float> q; // query
MatStorageT<float> q_T; // Transposed to maximize attention speed.
MatStorageT<float> pre_att_rms_out;
MatStorageT<float> att; // attention vector
MatStorageT<float> att_out; // attention output
// Accumulation of attention outputs over heads
MatStorageT<BF16> att_sums;
// Rope
MatStorageT<float> inv_timescale;
MatStorageT<float> inv_timescale_global;
};
// A non-owning view of AttentionActivations.
struct AttentionActivationsPtrs {
AttentionActivationsPtrs(const ModelConfig& config, size_t seq_len)
: config(config),
div_seq_len(static_cast<uint32_t>(seq_len)),
div_heads(static_cast<uint32_t>(config.layer_configs[0].heads)),
query_scale(ChooseQueryScale(config)) {}
AttentionActivationsPtrs(const ModelConfig& config, size_t seq_len,
const AttentionActivations& activations)
: AttentionActivationsPtrs(config, seq_len) {
q = activations.q;
q_T = activations.q_T;
pre_att_rms_out = activations.pre_att_rms_out;
att = activations.att;
att_out = activations.att_out;
att_sums = activations.att_sums;
inv_timescale = activations.inv_timescale;
inv_timescale_global = activations.inv_timescale_global;
}
const ModelConfig& config;
MatPtrT<float> q;
MatPtrT<float> q_T;
MatPtrT<float> pre_att_rms_out;
MatPtrT<float> att;
MatPtrT<float> att_out;
MatPtrT<BF16> att_sums;
MatPtrT<float> inv_timescale;
MatPtrT<float> inv_timescale_global;
hwy::Divisor div_seq_len;
hwy::Divisor div_heads;
float query_scale;
};
struct Activations {
Activations(const ModelConfig& config, size_t batch_size, size_t seq_len,
ThreadingContext& ctx,
std::vector<hwy::AlignedFreeUniquePtr<uint8_t*[]>>& row_ptrs)
: layer_config(config.layer_configs[0]),
x(MatFactory("x", batch_size, config.model_dim, ctx.allocator)),
x_bf(MatFactory("x_bf", batch_size, config.model_dim, ctx.allocator)),
logits(
MatFactory("logits", batch_size, config.vocab_size, ctx.allocator)),
sampled(MatFactory("sampled", batch_size, 3, ctx.allocator)),
pre_ffw_rms_out(MatFactory("pre_ffw_rms_out", batch_size,
config.model_dim, ctx.allocator)),
C1(MatFactory("C1", batch_size, layer_config.ff_hidden_dim,
ctx.allocator)),
C2(MatFactory("C2", batch_size, layer_config.ff_hidden_dim,
ctx.allocator)),
ffw_out(
MatFactory("ffw_out", batch_size, config.model_dim, ctx.allocator)),
attention_storage(config, layer_config, batch_size, seq_len,
ctx.allocator, row_ptrs),
attention(config, seq_len, attention_storage) {
HWY_ASSERT(batch_size != 0);
// For MatMul outputs, precompute their row pointers.
// If we forget any MatMul outputs here, debug builds print a warning but
// fill them in each MatMul call.
x.AllocateAndAttachRowPtrs(row_ptrs);
x_bf.AllocateAndAttachRowPtrs(row_ptrs);
logits.AllocateAndAttachRowPtrs(row_ptrs);
C1.AllocateAndAttachRowPtrs(row_ptrs);
C2.AllocateAndAttachRowPtrs(row_ptrs);
ffw_out.AllocateAndAttachRowPtrs(row_ptrs);
// Note that BindC on any MatMul output considerably slows down Prefill.
}
// Negligible CPU time.
void SetBatchSize(size_t batch_size) {
x.OverrideRows(batch_size);
x_bf.OverrideRows(batch_size);
logits.OverrideRows(batch_size);
sampled.OverrideRows(batch_size);
pre_ffw_rms_out.OverrideRows(batch_size);
C1.OverrideRows(batch_size);
C2.OverrideRows(batch_size);
ffw_out.OverrideRows(batch_size);
attention_storage.SetBatchSize(batch_size);
attention.q = attention_storage.q;
attention.q_T = attention_storage.q_T;
attention.pre_att_rms_out = attention_storage.pre_att_rms_out;
attention.att = attention_storage.att;
attention.att_out = attention_storage.att_out;
attention.att_sums = attention_storage.att_sums;
}
const LayerConfig& layer_config;
MatStorageT<float> x; // input
MatStorageT<BF16> x_bf; // output of final RMSNorm, input to EmbeddingMatmul
MatStorageT<float> logits; // TODO: BF16 after Softmax supports that.
MatStorageT<uint32_t> sampled; // batch_size x 3 (padded)
// Gated FFW
MatStorageT<BF16> pre_ffw_rms_out;
MatStorageT<BF16> C1;
MatStorageT<BF16> C2;
MatStorageT<float> ffw_out;
AttentionActivations attention_storage;
AttentionActivationsPtrs attention;
};
} // namespace gcpp
#endif // THIRD_PARTY_GEMMA_CPP_GEMMA_ACTIVATIONS_H_
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