extern/whisper.cpp
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whisper : add precalculated values of sin/cos for speeding up FFT (#1142)

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* Add sin/cos precalculated values to speedup FFT

* Update whisper.cpp

Co-authored-by: bobqianic <129547291+bobqianic@users.noreply.github.com>

* Update whisper.cpp

Co-authored-by: bobqianic <129547291+bobqianic@users.noreply.github.com>

---------

Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>
Co-authored-by: bobqianic <129547291+bobqianic@users.noreply.github.com>
This commit is contained in:
Alexandr Graschenkov 2023-08-25 16:51:14 +04:00 committed by GitHub
parent c5f9acf4b7
commit c84cf87261
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1 changed files with 26 additions and 7 deletions
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whisper.cpp
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@ -2347,6 +2347,23 @@ static std::string to_timestamp(int64_t t, bool comma = false) {
return std::string(buf);
}
#define SIN_COS_N_COUNT WHISPER_N_FFT
static float sin_vals[SIN_COS_N_COUNT];
static float cos_vals[SIN_COS_N_COUNT];
// In FFT, we frequently use sine and cosine operations with the same values.
// We can use precalculated values to speed up the process.
static void fill_sin_cos_table() {
static bool is_filled = false;
if (is_filled) return;
for (int i = 0; i < SIN_COS_N_COUNT; i++) {
double theta = (2*M_PI*i)/SIN_COS_N_COUNT;
sin_vals[i] = sinf(theta);
cos_vals[i] = cosf(theta);
}
is_filled = true;
}
// naive Discrete Fourier Transform
// input is real-valued
// output is complex-valued
@ -2354,15 +2371,16 @@ static void dft(const std::vector<float> & in, std::vector<float> & out) {
int N = in.size();
out.resize(N*2);
const int sin_cos_step = SIN_COS_N_COUNT / N;
for (int k = 0; k < N; k++) {
float re = 0;
float im = 0;
for (int n = 0; n < N; n++) {
float angle = 2*M_PI*k*n/N;
re += in[n]*cos(angle);
im -= in[n]*sin(angle);
int idx = (k * n * sin_cos_step) % (SIN_COS_N_COUNT); // t = 2*M_PI*k*n/N
re += in[n]*cos_vals[idx]; // cos(t)
im -= in[n]*sin_vals[idx]; // sin(t)
}
out[k*2 + 0] = re;
@ -2410,11 +2428,11 @@ static void fft(const std::vector<float> & in, std::vector<float> & out) {
fft(even, even_fft);
fft(odd, odd_fft);
const int sin_cos_step = SIN_COS_N_COUNT / N;
for (int k = 0; k < N/2; k++) {
float theta = 2*M_PI*k/N;
float re = cos(theta);
float im = -sin(theta);
int idx = k * sin_cos_step; // t = 2*M_PI*k/N
float re = cos_vals[idx]; // cos(t)
float im = -sin_vals[idx]; // sin(t)
float re_odd = odd_fft[2*k + 0];
float im_odd = odd_fft[2*k + 1];
@ -2694,6 +2712,7 @@ static std::string whisper_openvino_get_path_cache(std::string path_bin) {
#endif
struct whisper_state * whisper_init_state(whisper_context * ctx) {
fill_sin_cos_table();
whisper_state * state = new whisper_state;
const size_t scale = ctx->model.hparams.ftype ? 1 : 2;