Functions to compute energy per operation on a chip

on_chip_energy.py

"""Data taken from paper: Computing's Energy Problem (and what we can do about it) - Mark Horowitz

All output energies are in pJ (pico Joule)
"""

import math

E_INT_ADD_PER_BIT = (0.03 / 8 + 0.1 / 32) / 2


def int_add(n_bits: int):
    if n_bits == 8:
        return 0.03
    if n_bits == 32:
        return 0.1

    return E_INT_ADD_PER_BIT * n_bits


E_INT_MUL_PER_BIT = (0.2 / 8**2 + 3.1 / 32**2) / 2


def int_mul(n_bits: int):
    if n_bits == 8:
        return 0.2
    if n_bits == 32:
        return 3.1

    return E_INT_MUL_PER_BIT * n_bits**2


E_FP_ADD_PER_BIT = (0.4 / 16 + 0.9 / 32) / 2


def fp_add(n_bits: int):
    if n_bits == 16:
        return 0.4
    if n_bits == 32:
        return 0.9

    return E_FP_ADD_PER_BIT * n_bits


E_FP_MUL_PER_BIT = (1.1 / 16**2 + 3.7 / 32**2) / 2


def fp_mul(n_bits: int):
    if n_bits == 16:
        return 1.1
    if n_bits == 32:
        return 3.7

    return E_FP_MUL_PER_BIT * n_bits**2


E_DRAM = (1.3 + 2.6) / 2 * 1000
E_CACHE = (10 / math.sqrt(8) + 20 / math.sqrt(32) + 100 / math.sqrt(1000)) / 3


def memory_access(n_bytes: int, location: str):
    """Assuming 64-bit word size"""

    if location == "cache":
        return E_CACHE * math.sqrt(n_bytes / 1000)
    if location == "DRAM":
        return
    else:
        raise ValueError(f"Unknown location {location}")