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whisper.cpp/examples/talk-llama/llama-sampling.cpp

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talk-llama : sync llama.cpp
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#include "llama-sampling.h"
#include <algorithm>
#include <cstring>
#include <ctime>
#include <cfloat>
#include <numeric>
#include <unordered_map>
static void llama_log_softmax(float * array, size_t size) {
float max_l = *std::max_element(array, array + size);
float sum = 0.f;
for (size_t i = 0; i < size; ++i) {
float p = expf(array[i] - max_l);
sum += p;
array[i] = p;
}
for (size_t i = 0; i < size; ++i) {
array[i] = logf(array[i] / sum);
}
}
void llama_set_rng_seed_impl(struct llama_sampling * smpl, uint32_t seed) {
if (seed == LLAMA_DEFAULT_SEED) {
seed = time(NULL);
}
smpl->rng.seed(seed);
}
void llama_sample_softmax_impl(struct llama_sampling * smpl, llama_token_data_array * candidates) {
GGML_ASSERT(candidates->size > 0);
const int64_t t_start_sample_us = ggml_time_us();
// Sort the logits in descending order
if (!candidates->sorted) {
std::sort(candidates->data, candidates->data + candidates->size, [](const llama_token_data & a, const llama_token_data & b) {
return a.logit > b.logit;
});
candidates->sorted = true;
}
float max_l = candidates->data[0].logit;
float cum_sum = 0.0f;
for (size_t i = 0; i < candidates->size; ++i) {
float p = expf(candidates->data[i].logit - max_l);
candidates->data[i].p = p;
cum_sum += p;
}
for (size_t i = 0; i < candidates->size; ++i) {
candidates->data[i].p /= cum_sum;
}
if (smpl) {
smpl->t_sample_us += ggml_time_us() - t_start_sample_us;
}
}
void llama_sample_top_k_impl(struct llama_sampling * smpl, llama_token_data_array * candidates, int32_t k, size_t min_keep) {
// TODO: move bucket sort to separate function so that top_p/tail_free/typical/softmax first is equally fast
// if (k >= (int32_t)candidates->size) {
// return;
// }
const int64_t t_start_sample_us = ggml_time_us();
if (k <= 0) {
k = candidates->size;
}
k = std::max(k, (int) min_keep);
k = std::min(k, (int) candidates->size);
// Sort scores in descending order
if (!candidates->sorted) {
auto comp = [](const llama_token_data & a, const llama_token_data & b) {
return a.logit > b.logit;
};
if (k <= 128) {
std::partial_sort(candidates->data, candidates->data + k, candidates->data + candidates->size, comp);
} else {
constexpr int nbuckets = 128;
constexpr float bucket_low = -10.0f;
constexpr float bucket_high = 10.0f;
constexpr float bucket_scale = nbuckets/(bucket_high - bucket_low);
talk-llama : sync llama.cpp
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constexpr float bucket_inter = -bucket_low * bucket_scale;
talk-llama : sync llama.cpp
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std::vector<int> bucket_idx(candidates->size);
std::vector<int> histo(nbuckets, 0);
for (int i = 0; i < (int)candidates->size; ++i) {
const float val = candidates->data[i].logit;
talk-llama : sync llama.cpp
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int ib = int(bucket_scale * val + bucket_inter); //nbuckets * (val - bucket_low) / (bucket_high - bucket_low);
talk-llama : sync llama.cpp
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ib = std::max(0, std::min(nbuckets-1, ib));
bucket_idx[i] = ib;
++histo[ib];
}
int nhave = 0;
int ib = nbuckets - 1;
for ( ; ib >= 0; --ib) {
nhave += histo[ib];
if (nhave >= k) break;
}
std::vector<llama_token_data> tmp_tokens(nhave);
auto ptr = tmp_tokens.data();
std::vector<llama_token_data*> bucket_ptrs;
bucket_ptrs.reserve(nbuckets - ib);
for (int j = nbuckets - 1; j >= ib; --j) {
bucket_ptrs.push_back(ptr);
ptr += histo[j];
}
for (int i = 0; i < (int)candidates->size; ++i) {
int j = bucket_idx[i];
if (j >= ib) {
*bucket_ptrs[nbuckets-1-j]++ = candidates->data[i];
}
}
ptr = tmp_tokens.data();
int ndone = 0;
for (int j = nbuckets-1; j > ib; --j) {
std::sort(ptr, ptr + histo[j], comp);
ptr += histo[j];
ndone += histo[j];
}
std::partial_sort(ptr, ptr + k - ndone, ptr + histo[ib], comp);
std::memcpy(candidates->data, tmp_tokens.data(), k*sizeof(llama_token_data));
}
candidates->sorted = true;
}
candidates->size = k;
if (smpl) {
smpl->t_sample_us += ggml_time_us() - t_start_sample_us;
}
}
void llama_sample_top_p_impl(struct llama_sampling * smpl, llama_token_data_array * candidates, float p, size_t min_keep) {
if (p >= 1.0f) {
return;
}
llama_sample_softmax_impl(smpl, candidates);
const int64_t t_start_sample_us = ggml_time_us();
// Compute the cumulative probabilities
float cum_sum = 0.0f;
size_t last_idx = candidates->size;
for (size_t i = 0; i < candidates->size; ++i) {
cum_sum += candidates->data[i].p;
// Check if the running sum is at least p or if we have kept at least min_keep tokens
// we set the last index to i+1 to indicate that the current iterate should be included in the set
if (cum_sum >= p && i + 1 >= min_keep) {
last_idx = i + 1;
break;
}
}
// Resize the output vector to keep only the top-p tokens
candidates->size = last_idx;
if (smpl) {
smpl->t_sample_us += ggml_time_us() - t_start_sample_us;
}
}
void llama_sample_min_p_impl(struct llama_sampling * smpl, llama_token_data_array * candidates, float p, size_t min_keep) {
if (p <= 0.0f || !candidates->size) {
return;
}
const int64_t t_start_sample_us = ggml_time_us();
bool min_p_applied = false;
// if the candidates aren't sorted, try the unsorted implementation first
if (!candidates->sorted) {
std::vector<llama_token_data> filtered_tokens;
float max_logit = -FLT_MAX;
for (size_t i = 0; i < candidates->size; ++i) {
max_logit = std::max(max_logit, candidates->data[i].logit);
}
const float min_logit = max_logit + logf(p); // min logit for p_i >= p * p_max
for (size_t i = 0; i < candidates->size; ++i) {
if (candidates->data[i].logit >= min_logit) {
filtered_tokens.push_back(candidates->data[i]);
}
}
// if we have enough values the operation was a success
if (filtered_tokens.size() >= min_keep) {
memcpy(candidates->data, filtered_tokens.data(), filtered_tokens.size()*sizeof(llama_token_data));
candidates->size = filtered_tokens.size();
min_p_applied = true;
}
}
// if the candidates are sorted or the unsorted implementation failed, use this implementation
if (!min_p_applied) {
// Sort the logits in descending order
if (!candidates->sorted) {
std::sort(candidates->data, candidates->data + candidates->size, [](const llama_token_data & a, const llama_token_data & b) {
return a.logit > b.logit;
});
candidates->sorted = true;
}
const float min_logit = candidates->data[0].logit + logf(p); // min logit for p_i >= p * p_max
size_t i = 1; // first token always matches
for (; i < candidates->size; ++i) {
if (candidates->data[i].logit < min_logit && i >= min_keep) {
break; // prob too small
}
}
// Resize the output vector to keep only the matching tokens
candidates->size = i;
}
if (smpl) {
smpl->t_sample_us += ggml_time_us() - t_start_sample_us;
}
}
void llama_sample_tail_free_impl(struct llama_sampling * smpl, llama_token_data_array * candidates, float z, size_t min_keep) {
if (z >= 1.0f || candidates->size <= 2) {
return;
}
llama_sample_softmax_impl((struct llama_sampling *) nullptr, candidates);
const int64_t t_start_sample_us = ggml_time_us();
// Compute the first and second derivatives
std::vector<float> first_derivatives(candidates->size - 1);
std::vector<float> second_derivatives(candidates->size - 2);
for (size_t i = 0; i < first_derivatives.size(); ++i) {
first_derivatives[i] = candidates->data[i].p - candidates->data[i + 1].p;
}
for (size_t i = 0; i < second_derivatives.size(); ++i) {
second_derivatives[i] = first_derivatives[i] - first_derivatives[i + 1];
}
// Calculate absolute value of second derivatives
for (size_t i = 0; i < second_derivatives.size(); ++i) {
second_derivatives[i] = std::abs(second_derivatives[i]);
}
// Normalize the second derivatives
{
const float second_derivatives_sum = std::accumulate(second_derivatives.begin(), second_derivatives.end(), 0.0f);
if (second_derivatives_sum > 1e-6f) {
for (float & value : second_derivatives) {
value /= second_derivatives_sum;
}
} else {
for (float & value : second_derivatives) {
value = 1.0f / second_derivatives.size();
}
}
}
float cum_sum = 0.0f;
size_t last_idx = candidates->size;
for (size_t i = 0; i < second_derivatives.size(); ++i) {
cum_sum += second_derivatives[i];
// Check if the running sum is greater than z or if we have kept at least min_keep tokens
if (cum_sum > z && i >= min_keep) {
last_idx = i;
break;
}
}
// Resize the output vector to keep only the tokens above the tail location
candidates->size = last_idx;
if (smpl) {
smpl->t_sample_us += ggml_time_us() - t_start_sample_us;
}
}
void llama_sample_typical_impl(struct llama_sampling * smpl, llama_token_data_array * candidates, float p, size_t min_keep) {
// Reference implementation:
// https://github.com/huggingface/transformers/compare/main...cimeister:typical-sampling:typical-pr
if (p >= 1.0f) {
return;
}
// Compute the softmax of logits and calculate entropy
llama_sample_softmax_impl((struct llama_sampling *) nullptr, candidates);
const int64_t t_start_sample_us = ggml_time_us();
float entropy = 0.0f;
for (size_t i = 0; i < candidates->size; ++i) {
entropy += -candidates->data[i].p * logf(candidates->data[i].p);
}
// Compute the absolute difference between negative log probability and entropy for each candidate
std::vector<float> shifted_scores;
for (size_t i = 0; i < candidates->size; ++i) {
float shifted_score = fabsf(-logf(candidates->data[i].p) - entropy);
shifted_scores.push_back(shifted_score);
}
// Sort tokens based on the shifted_scores and their corresponding indices
std::vector<size_t> indices(candidates->size);
std::iota(indices.begin(), indices.end(), 0);
std::sort(indices.begin(), indices.end(), [&](size_t a, size_t b) {
return shifted_scores[a] < shifted_scores[b];
});
// Compute the cumulative probabilities
float cum_sum = 0.0f;
size_t last_idx = indices.size();
for (size_t i = 0; i < indices.size(); ++i) {
size_t idx = indices[i];
cum_sum += candidates->data[idx].p;
// Check if the running sum is greater than typical or if we have kept at least min_keep tokens
if (cum_sum > p && i >= min_keep - 1) {
last_idx = i + 1;
break;
}
}
// Resize the output vector to keep only the locally typical tokens
std::vector<llama_token_data> new_candidates;
for (size_t i = 0; i < last_idx; ++i) {
size_t idx = indices[i];
new_candidates.push_back(candidates->data[idx]);
}
// Replace the data in candidates with the new_candidates data
std::copy(new_candidates.begin(), new_candidates.end(), candidates->data);
candidates->size = new_candidates.size();
candidates->sorted = false;
if (smpl) {
smpl->t_sample_us += ggml_time_us() - t_start_sample_us;
}
}
void llama_sample_entropy_impl(struct llama_sampling * smpl, llama_token_data_array * candidates, float min_temp, float max_temp, float exponent_val) {
const int64_t t_start_sample_us = ggml_time_us();
// no need to do anything if there is only one (or zero) candidates
if(candidates->size <= 1) {
return;
}
// Calculate maximum possible entropy
float max_entropy = -logf(1.0f / candidates->size);
llama_sample_softmax_impl((struct llama_sampling *) nullptr, candidates);
// Calculate entropy of the softmax probabilities
float entropy = 0.0f;
for (size_t i = 0; i < candidates->size; ++i) {
float prob = candidates->data[i].p;
if (prob > 0.0f) { // Ensure no log(0)
entropy -= prob * logf(prob);
}
}
// Normalize the entropy (max_entropy cannot be 0 here because we checked candidates->size != 1 above)
float normalized_entropy = entropy / max_entropy;
// Map the normalized entropy to the desired temperature range using the power function
float dyn_temp = min_temp + (max_temp - min_temp) * powf(normalized_entropy, exponent_val);
#ifdef DEBUG
LLAMA_LOG_INFO("Your text maxtemp value is: %f\n", max_temp);
LLAMA_LOG_INFO("Entropy: %f\n", entropy);
LLAMA_LOG_INFO("Max Possible Entropy: %f\n", max_entropy);
LLAMA_LOG_INFO("Normalized Entropy: %f\n", normalized_entropy);
LLAMA_LOG_INFO("Exponent: %f\n", exponent_val);
LLAMA_LOG_INFO("Dynamic Temperature (dyn_temp): %f\n", dyn_temp);
#endif
// Apply the dynamically calculated temperature scaling
for (size_t i = 0; i < candidates->size; ++i) {
candidates->data[i].logit /= dyn_temp;
}
// Re-compute softmax probabilities after scaling logits with dynamic temperature
double max_l_double = candidates->data[0].logit;
double cum_sum_double = 0.0;
for (size_t i = 0; i < candidates->size; ++i) {
double p = exp(candidates->data[i].logit - max_l_double);
candidates->data[i].p = p; // Store the scaled probability
cum_sum_double += p;
}
for (size_t i = 0; i < candidates->size; ++i) {
candidates->data[i].p /= cum_sum_double; // Re-normalize the probabilities
}
#ifdef DEBUG
// Print the updated top 25 probabilities after temperature scaling
LLAMA_LOG_INFO("\nUpdated Top 25 Probabilities After Dynamic Temperature Scaling (in percentages):\n");
for (size_t i = 0; i < 25 && i < candidates->size; ++i) {
LLAMA_LOG_INFO("Token %zu: %f%%\n", i + 1, candidates->data[i].p * 100.0f);
}
#endif
if (smpl) {
smpl->t_sample_us += ggml_time_us() - t_start_sample_us;
}
}
void llama_sample_temp_impl(struct llama_sampling * smpl, llama_token_data_array * candidates, float temp) {
const int64_t t_start_sample_us = ggml_time_us();
for (size_t i = 0; i < candidates->size; ++i) {
candidates->data[i].logit /= temp;
}
if (smpl) {
smpl->t_sample_us += ggml_time_us() - t_start_sample_us;
}
}
void llama_sample_repetition_penalties_impl(
struct llama_sampling * smpl,
llama_token_data_array * candidates,
const llama_token * last_tokens,
size_t penalty_last_n,
float penalty_repeat,
float penalty_freq,
float penalty_present) {
if (penalty_last_n == 0 || (penalty_repeat == 1.0f && penalty_freq == 0.0f && penalty_present == 0.0f)) {
return;
}
const int64_t t_start_sample_us = ggml_time_us();
// Create a frequency map to count occurrences of each token in last_tokens
std::unordered_map<llama_token, int> token_count;
for (size_t i = 0; i < penalty_last_n; ++i) {
token_count[last_tokens[i]]++;
}
// Apply frequency and presence penalties to the candidates
for (size_t i = 0; i < candidates->size; ++i) {
const auto token_iter = token_count.find(candidates->data[i].id);
if (token_iter == token_count.end()) {
continue;
}
const int count = token_iter->second;
// The academic publication that described this technique actually just only divided, but that would cause tokens with negative logits to become more likely, which is obviously wrong.
// This is common fix for this problem, which is to multiply by the penalty instead of dividing.
if (candidates->data[i].logit <= 0) {
candidates->data[i].logit *= penalty_repeat;
} else {
candidates->data[i].logit /= penalty_repeat;
}
candidates->data[i].logit -= float(count) * penalty_freq + float(count > 0) * penalty_present;
}
candidates->sorted = false;
if (smpl) {
smpl->t_sample_us += ggml_time_us() - t_start_sample_us;
}
}
void llama_sample_apply_guidance_impl(
struct llama_sampling * smpl,
float * logits,
float * logits_guidance,
float scale) {
GGML_ASSERT(smpl);
const auto t_start_sample_us = ggml_time_us();
const auto n_vocab = smpl->n_vocab;
llama_log_softmax(logits, n_vocab);
llama_log_softmax(logits_guidance, n_vocab);
for (int i = 0; i < n_vocab; ++i) {
auto & l = logits[i];
const auto & g = logits_guidance[i];
l = scale * (l - g) + g;
}
smpl->t_sample_us += ggml_time_us() - t_start_sample_us;
}
llama_token llama_sample_token_mirostat_impl(struct llama_sampling * smpl, llama_token_data_array * candidates, float tau, float eta, int32_t m, float * mu) {
GGML_ASSERT(smpl);
const int32_t n_vocab = float(smpl->n_vocab);
int64_t t_start_sample_us = ggml_time_us();
llama_sample_softmax_impl((struct llama_sampling *) nullptr, candidates);
// Estimate s_hat using the most probable m tokens
float s_hat = 0.0;
float sum_ti_bi = 0.0;
float sum_ti_sq = 0.0;
for (size_t i = 0; i < size_t(m - 1) && i < candidates->size - 1; ++i) {
float t_i = logf(float(i + 2) / float(i + 1));
float b_i = logf(candidates->data[i].p / candidates->data[i + 1].p);
sum_ti_bi += t_i * b_i;
sum_ti_sq += t_i * t_i;
}
s_hat = sum_ti_bi / sum_ti_sq;
// Compute k from the estimated s_hat and target surprise value
float epsilon_hat = s_hat - 1;
float k = powf((epsilon_hat * powf(2, *mu)) / (1 - powf(n_vocab, -epsilon_hat)), 1 / s_hat);
// Sample the next word X using top-k sampling
llama_sample_top_k_impl((struct llama_sampling *) nullptr, candidates, int(k), 1);
smpl->t_sample_us += ggml_time_us() - t_start_sample_us;
llama_token X = llama_sample_token_impl(smpl, candidates);
t_start_sample_us = ggml_time_us();
// Compute error as the difference between observed surprise and target surprise value
size_t X_idx = std::distance(candidates->data, std::find_if(candidates->data, candidates->data + candidates->size, [&](const llama_token_data & candidate) {
return candidate.id == X;
}));
float observed_surprise = -log2f(candidates->data[X_idx].p);
float e = observed_surprise - tau;
// Update mu using the learning rate and error
*mu = *mu - eta * e;
smpl->t_sample_us += ggml_time_us() - t_start_sample_us;
return X;
}
llama_token llama_sample_token_mirostat_v2_impl(struct llama_sampling * smpl, llama_token_data_array * candidates, float tau, float eta, float * mu) {
int64_t t_start_sample_us;
t_start_sample_us = ggml_time_us();
llama_sample_softmax_impl(smpl, candidates);
// Truncate the words with surprise values greater than mu
candidates->size = std::distance(candidates->data, std::find_if(candidates->data, candidates->data + candidates->size, [&](const llama_token_data & candidate) {
return -log2f(candidate.p) > *mu;
}));
if (candidates->size == 0) {
candidates->size = 1;
}
if (smpl) {
smpl->t_sample_us += ggml_time_us() - t_start_sample_us;
}
// Normalize the probabilities of the remaining words
llama_sample_softmax_impl(smpl, candidates);
// Sample the next word X from the remaining words
llama_token X = llama_sample_token_impl(smpl, candidates);
t_start_sample_us = ggml_time_us();
// Compute error as the difference between observed surprise and target surprise value
size_t X_idx = std::distance(candidates->data, std::find_if(candidates->data, candidates->data + candidates->size, [&](const llama_token_data & candidate) {
return candidate.id == X;
}));
float observed_surprise = -log2f(candidates->data[X_idx].p);
float e = observed_surprise - tau;
// Update mu using the learning rate and error
*mu = *mu - eta * e;
if (smpl) {
smpl->t_sample_us += ggml_time_us() - t_start_sample_us;
}
return X;
}
llama_token llama_sample_token_greedy_impl(struct llama_sampling * smpl, llama_token_data_array * candidates) {
const int64_t t_start_sample_us = ggml_time_us();
// Find max element
auto * max_iter = std::max_element(candidates->data, candidates->data + candidates->size, [](const llama_token_data & a, const llama_token_data & b) {
return a.logit < b.logit;
});
llama_token result = max_iter->id;
if (smpl) {
smpl->t_sample_us += ggml_time_us() - t_start_sample_us;
smpl->n_sample++;
}
return result;
}
llama_token llama_sample_token_with_rng_impl(struct llama_sampling * smpl, llama_token_data_array * candidates, std::mt19937 & rng) {
GGML_ASSERT(smpl);
const int64_t t_start_sample_us = ggml_time_us();
llama_sample_softmax_impl((struct llama_sampling *) nullptr, candidates);
std::vector<float> probs;
probs.reserve(candidates->size);
for (size_t i = 0; i < candidates->size; ++i) {
probs.push_back(candidates->data[i].p);
}
std::discrete_distribution<> dist(probs.begin(), probs.end());
int idx = dist(rng);
llama_token result = candidates->data[idx].id;
smpl->t_sample_us += ggml_time_us() - t_start_sample_us;
smpl->n_sample++;
return result;
}
llama_token llama_sample_token_impl(struct llama_sampling * smpl, llama_token_data_array * candidates) {
return llama_sample_token_with_rng_impl(smpl, candidates, smpl->rng);
}
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