decay.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 _DECAY_H_
#define _DECAY_H_
 
#include <common/maths-util.h>
#include <common/neuron-typedefs.h>
 
typedef UFRACT decay_t;
 
static inline s1615 decay_s1615(s1615 x, decay_t decay) {
    int64_t s = (int64_t) bitsk(x);
    int64_t u = (int64_t) bitsulr(decay);
 
    return kbits((int_k_t) ((s * u) >> 32));
}
 
static inline u1616 decay_u1616(u1616 x, decay_t decay) {
    uint64_t s = (uint64_t) bitsuk(x);
    uint64_t u = (uint64_t) bitsulr(decay);
 
    return ukbits((uint_uk_t) ((s * u) >> 32));
}
 
static inline s015 decay_s015(s015 x, decay_t decay) {
    int64_t s = (int64_t) bitsk(x);
    int64_t u = (int64_t) bitsulr(decay);
 
    return rbits((int_r_t) ((s * u) >> 32));
}
 
static inline u016 decay_u016(u016 x, decay_t decay) {
    uint64_t s = (uint64_t) bitsuk(x);
    uint64_t u = (uint64_t) bitsulr(decay);
 
    return urbits((uint_ur_t) ((s * u) >> 32));
}
 
static inline u032 decay_s1615_to_u032(s1615 x, decay_t decay) {
    uint64_t s = (uint64_t) bitsk(x);
    uint64_t u = (uint64_t) bitsulr(decay);
 
    return ulrbits((uint_ulr_t) ((s * u) >> 15));
}
 
// The following permits us to do a type-generic macro for decay manipulation
/*----------------------------------
 * This method is currently assumed to be faulty. Please do not use it yet.
 * Plan is to fix method and not need to use the private methods directly.
 * issue seems to be in __builtin_types_compatible_p always returning False
 * or at least, that there's the impression that on some types it results in
 * the abort statement and therefore kills scripts dead on SpiNNaker.
 * ---------------------------------
 */
#define decay(x, d) ({ \
    __typeof__(x) tmp = (x); \
    if (__builtin_types_compatible_p(__typeof__(x), s1615)) {\
        tmp = decay_s1615(x, d); \
    } else if (__builtin_types_compatible_p(__typeof__(x), u1616)) {\
        tmp = decay_u1616(x, d); \
    } else if (__builtin_types_compatible_p(__typeof__(x), s015)) {\
        tmp = decay_s015(x, d); \
    } else if (__builtin_types_compatible_p(__typeof__(x), u016)) {\
        tmp = decay_u016(x, d); \
    } else {\
        abort(1); \
    }\
    tmp; \
})
 
#endif // _DECAY_H_