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Add STDP learning support #1

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21 changes: 21 additions & 0 deletions examples/stdp_example.c
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Original file line number Diff line number Diff line change
@@ -0,0 +1,21 @@
#include "../src/cbrain.h"
#include <unistd.h>

int main()
{
srand((unsigned int)time(NULL));
struct brain* b = brain_init(2, 0.1f);
neuron_set_type(b->neurons[0], sensory);
neuron_set_type(b->neurons[1], motor);
neuron_link(b->neurons[0], b->neurons[1], 5);

for (int t = 0; t < 10; t++) {
if (t == 1) neuron_fire(b->neurons[0]);
if (t == 3) neuron_fire(b->neurons[1]);
neuron_update_range(0, 1, b);
printf("step %u weight=%d\n", b->step, b->neurons[0]->wts[0]);
usleep(100000);
}
return 0;
}

4 changes: 2 additions & 2 deletions examples/test.sh
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,6 @@ make uninstall
make clean
make -j15 install
cd examples
gcc tem_test.c -o tem_test -lSDL2 -lcbrain
gcc stdp_example.c -o stdp_example -lSDL2 -lcbrain
echo
./tem_test
./stdp_example
106 changes: 71 additions & 35 deletions src/brain.c
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Expand Up @@ -22,6 +22,8 @@ SOFTWARE.

#include "cbrain.h"

pthread_mutex_t lock;

/* initialize new neuron */
struct neuron* neuron_init(uint id, float decay)
{
Expand All @@ -37,10 +39,11 @@ struct neuron* neuron_init(uint id, float decay)
n->thisstate = 0.0;
n->nextstate = 0.0;
n->state_decay = decay;
n->fired = 0;
n->n_fired = 0;
n->n_type = undefined;
return n;
n->fired = 0;
n->n_fired = 0;
n->n_type = undefined;
n->last_fired = -STDP_WINDOW;
return n;
}

/* link neuron 'n' to neuron 'src' with given weight 'wt' */
Expand Down Expand Up @@ -111,10 +114,37 @@ void neuron_unlink(struct neuron* src, struct neuron* n)
/* accumulate passed weight to neuron's nextstate */
void neuron_accum(struct neuron* n, uint wt)
{
cbrain_print(2, "accumulating neuron %d with weight %d\n", n->id, wt);
pthread_mutex_lock(&lock);
n->nextstate += wt;
pthread_mutex_unlock(&lock);
cbrain_print(2, "accumulating neuron %d with weight %d\n", n->id, wt);
pthread_mutex_lock(&lock);
n->nextstate += wt;
pthread_mutex_unlock(&lock);
}

void neuron_stdp(struct brain* b, struct neuron* n)
{
/* potentiation for recently active presynaptic neurons */
for (int i = 0; i < n->inc; i++) {
int pre_id = n->incoming[i];
struct neuron* pre = b->neurons[pre_id];
int dt = b->step - pre->last_fired;
if (dt > 0 && dt <= STDP_WINDOW) {
int idx = checkexist(n->id, pre->links, pre->lc);
if (idx != -1) {
pre->wts[idx] += STDP_INC;
if (pre->wts[idx] > WEIGHT_MAX) pre->wts[idx] = WEIGHT_MAX;
}
}
}

/* depression for synapses where postsynaptic neuron fired recently */
for (int i = 0; i < n->lc; i++) {
struct neuron* post = b->neurons[n->links[i]];
int dt = b->step - post->last_fired;
if (dt > 0 && dt <= STDP_WINDOW) {
n->wts[i] -= STDP_DEC;
if (n->wts[i] < -WEIGHT_MAX) n->wts[i] = -WEIGHT_MAX;
}
}
}

/* check if neuron's thisstate exceeds the threshold,
Expand All @@ -126,17 +156,19 @@ int neuron_update(struct neuron* n, struct brain* b)
assert(n->id <= (b->nc - 1));

// fire neuron if thisstate exceeds THRESHOLD
if (n->thisstate >= THRESHOLD) {
n->f_type = self;
for (int i = 0; i < n->lc; i++) {
cbrain_print(4, "sending %d from %d to %d\n", n->wts[i], n->id, n->links[i]);
b->neurons[n->links[i]]->nextstate += n->wts[i];
}
n->fired = 1;
n->thisstate = 0;
n->nextstate = 0;
n->n_fired += 1;
} else {
if (n->thisstate >= THRESHOLD) {
n->f_type = self;
for (int i = 0; i < n->lc; i++) {
cbrain_print(4, "sending %d from %d to %d\n", n->wts[i], n->id, n->links[i]);
b->neurons[n->links[i]]->nextstate += n->wts[i];
}
n->fired = 1;
n->thisstate = 0;
n->nextstate = 0;
n->n_fired += 1;
neuron_stdp(b, n);
n->last_fired = b->step;
} else {
n->thisstate += n->nextstate;

// thisstate decay if next state is zero
Expand All @@ -154,14 +186,15 @@ int neuron_update(struct neuron* n, struct brain* b)

int neuron_update_range(uint s, uint e, struct brain* b)
{
int nf = 0;
for (int i = s; i <= e; i++) {
int fired = neuron_update(b->neurons[i], b);
if (fired == 1) {
nf += 1;
}
}
return nf;
int nf = 0;
for (int i = s; i <= e; i++) {
int fired = neuron_update(b->neurons[i], b);
if (fired == 1) {
nf += 1;
}
}
b->step += 1;
return nf;
}

void neuron_set_type(struct neuron* n, type t)
Expand Down Expand Up @@ -207,9 +240,10 @@ struct brain* brain_init(int s, float decay)
struct brain* b = (struct brain*)malloc(sizeof(struct brain));
b->neurons = (struct neuron**)malloc(sizeof(struct neuron) * s);
b->nc = s;
b->nmax = s;
b->fitness = 0.0;
b->state_decay = decay;
b->nmax = s;
b->fitness = 0.0;
b->state_decay = decay;
b->step = 0;

// make neurons
for (int i = 0; i < s; i++) {
Expand All @@ -220,11 +254,13 @@ struct brain* brain_init(int s, float decay)

void brain_reset(struct brain* b)
{
for (int i = 0; i < b->nc; i++) {
b->neurons[i]->thisstate = 0;
b->neurons[i]->nextstate = 0;
b->neurons[i]->fired = 0;
}
for (int i = 0; i < b->nc; i++) {
b->neurons[i]->thisstate = 0;
b->neurons[i]->nextstate = 0;
b->neurons[i]->fired = 0;
b->neurons[i]->last_fired = -STDP_WINDOW;
}
b->step = 0;
}

void brain_neuron_type(struct brain* b, type t)
Expand Down
61 changes: 34 additions & 27 deletions src/cbrain.h
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Original file line number Diff line number Diff line change
Expand Up @@ -41,6 +41,10 @@ SOFTWARE.
#define MUTATE_PROB 0.00001
#define WEIGHT_MIN 1
#define WEIGHT_MAX 20
/* STDP parameters */
#define STDP_WINDOW 5
#define STDP_INC 1
#define STDP_DEC 1
#define WIN_WIDTH 800
#define WIN_HEIGHT 400
#define E 2.71828182
Expand All @@ -51,9 +55,9 @@ typedef unsigned int uint;
typedef enum { undefined, sensory, intermediate, motor } type;
typedef enum { user, self } fire_type;

pthread_mutex_t lock;
extern pthread_mutex_t lock;

struct neuron {
typedef struct neuron {
int id;
int *links;
int *incoming;
Expand All @@ -68,53 +72,55 @@ struct neuron {
float thisstate;
float nextstate;
float state_decay;
uint fired;
uint n_fired;
uint fired;
uint n_fired;
int last_fired;
} neuron;

struct brain {
typedef struct brain {
uint nc;
uint nmax;
float state_decay;
float fitness;
struct neuron** neurons;
float fitness;
struct neuron** neurons;
uint step;
} brain;

struct nthread {
typedef struct nthread {
pthread_t tid;
uint s;
uint e;
uint status;
} nthread;

struct thread_bank {
typedef struct thread_bank {
uint tc;
uint tmax;

struct nthread** threads;
struct nthread** threads;
} thread_bank;

struct sdlctx {
SDL_Window* win;
SDL_Renderer* ren;
SDL_Event event;
typedef struct sdlctx {
SDL_Window* win;
SDL_Renderer* ren;
SDL_Event event;
} sdlctx;

struct vect {
float x;
float y;
typedef struct vect {
float x;
float y;
} vect;

struct entityctx {
int mlstart;
int mrstart;
int mlend;
int mrend;
int width;
int height;
float rot;
float x;
float y;
typedef struct entityctx {
int mlstart;
int mrstart;
int mlend;
int mrend;
int width;
int height;
float rot;
float x;
float y;
} entityctx;

/* src/brain.c */
Expand All @@ -129,6 +135,7 @@ void neuron_accum(struct neuron*, uint);
void neuron_fire(struct neuron*);
int neuron_update(struct neuron*, struct brain*);
int neuron_update_range(uint, uint, struct brain*);
void neuron_stdp(struct brain*, struct neuron*);
void neuron_set_type(struct neuron*, type);
void neuron_add(struct brain*);
void neuron_show_stat(struct neuron*);
Expand Down