timing_pair_impl.h

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/*
 * Copyright (c) 2015 The University of Manchester
 *
 * 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 _TIMING_PAIR_IMPL_H_
#define _TIMING_PAIR_IMPL_H_
 
//---------------------------------------
// Typedefines
//---------------------------------------
typedef int16_t post_trace_t;
typedef int16_t pre_trace_t;
 
#include <neuron/plasticity/stdp/synapse_structure/synapse_structure_weight_impl.h>
#include "timing.h"
#include <neuron/plasticity/stdp/weight_dependence/weight_one_term.h>
 
// Include debug header for log_info etc
#include <debug.h>
 
// Include generic plasticity maths functions
#include <neuron/plasticity/stdp/maths.h>
#include <neuron/plasticity/stdp/stdp_typedefs.h>
 
//---------------------------------------
// Timing dependence inline functions
//---------------------------------------
static inline post_trace_t timing_get_initial_post_trace(void) {
    return 0;
}
 
static inline post_trace_t timing_decay_post(
        uint32_t time, uint32_t last_time, post_trace_t last_trace) {
    extern int16_lut *tau_minus_lookup;
    // Get time since last spike
    uint32_t delta_time = time - last_time;
 
    // Decay previous trace
    return (post_trace_t) STDP_FIXED_MUL_16X16(last_trace,
            maths_lut_exponential_decay(delta_time, tau_minus_lookup));
}
 
//---------------------------------------
static inline post_trace_t timing_add_post_spike(
        uint32_t time, uint32_t last_time, post_trace_t last_trace) {
 
    // Decay previous trace
    int16_t decayed_trace = timing_decay_post(time, last_time, last_trace);
 
    // Add energy caused by new spike to trace
    int16_t new_trace = decayed_trace + STDP_FIXED_POINT_ONE;
 
    // Return new pre- synaptic event with decayed trace values with energy
    // for new spike added
    return (post_trace_t) new_trace;
}
 
//---------------------------------------
static inline pre_trace_t timing_add_pre_spike(
        uint32_t time, uint32_t last_time, pre_trace_t last_trace) {
    extern int16_lut *tau_plus_lookup;
    // Get time since last spike
    uint32_t delta_time = time - last_time;
 
    // Decay previous trace
    int32_t decayed_trace = STDP_FIXED_MUL_16X16(last_trace,
        maths_lut_exponential_decay(delta_time, tau_plus_lookup));
 
    // Add energy caused by new spike to trace
    int32_t new_trace = decayed_trace + STDP_FIXED_POINT_ONE;
 
    log_debug("\tdelta_time=%u, trace=%d\n", delta_time, new_trace);
 
    // Return new pre-synaptic event with decayed trace values with energy
    // for new spike added
    return (pre_trace_t) new_trace;
}
 
//---------------------------------------
static inline update_state_t timing_apply_pre_spike(
        uint32_t time, UNUSED pre_trace_t trace, UNUSED uint32_t last_pre_time,
        UNUSED pre_trace_t last_pre_trace, uint32_t last_post_time,
        post_trace_t last_post_trace, update_state_t previous_state) {
    extern int16_lut *tau_minus_lookup;
 
    // Get time of event relative to last post-synaptic event
    uint32_t time_since_last_post = time - last_post_time;
    int32_t decayed_trace = STDP_FIXED_MUL_16X16(last_post_trace,
        maths_lut_exponential_decay(time_since_last_post, tau_minus_lookup));
 
    log_debug("\t\t\ttime_since_last_post_event=%u, decayed_trace=%d\n",
            time_since_last_post, decayed_trace);
 
    // Apply depression to state (which is a weight_state)
    return weight_one_term_apply_depression(previous_state, decayed_trace);
}
 
//---------------------------------------
static inline update_state_t timing_apply_post_spike(
        uint32_t time, UNUSED post_trace_t trace, uint32_t last_pre_time,
        pre_trace_t last_pre_trace, UNUSED uint32_t last_post_time,
        UNUSED post_trace_t last_post_trace, update_state_t previous_state) {
    extern int16_lut *tau_plus_lookup;
 
    // Get time of event relative to last pre-synaptic event
    uint32_t time_since_last_pre = time - last_pre_time;
    if (time_since_last_pre > 0) {
        int32_t decayed_trace = STDP_FIXED_MUL_16X16(last_pre_trace,
            maths_lut_exponential_decay(time_since_last_pre, tau_plus_lookup));
 
        log_debug("\t\t\ttime_since_last_pre_event=%u, decayed_trace=%d\n",
                time_since_last_pre, decayed_trace);
 
        // Apply potentiation to state (which is a weight_state)
        return weight_one_term_apply_potentiation(previous_state, decayed_trace);
    } else {
        return previous_state;
    }
}
 
#endif // _TIMING_PAIR_IMPL_H_