# Copyright (c) 2011 Advanced Micro Devices, Inc.
#               2011 Massachusetts Institute of Technology
# All rights reserved.
#
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# modification, are permitted provided that the following conditions are
# met: redistributions of source code must retain the above copyright
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# redistributions in binary form must reproduce the above copyright
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# documentation and/or other materials provided with the distribution;
# neither the name of the copyright holders nor the names of its
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# this software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#
# Authors: Brad Beckmann
#          Tushar Krishna

from m5.params import *
from m5.objects import *

class Torus(Topology):
    description='Torus'

# Makes a generic torus assuming an equal number of cache and directory cntrls
# Assuming a folded-torus on-chip layout (as shown on gem5 wiki).
# All links (including the wrap-around ones) are of equal length, double that
# of a mesh. Thus, each link is assigned a latency of 2 cycles.

def makeTopology(nodes, options, IntLink, ExtLink, Router):

    num_routers = options.num_cpus
    num_rows = options.mesh_rows

    # There must be an evenly divisible number of cntrls to routers
    # Also, obviously the number or rows must be <= the number of routers
    cntrls_per_router, remainder = divmod(len(nodes), num_routers)
    assert(num_rows <= num_routers)
    num_columns = int(num_routers / num_rows)
    assert(num_columns * num_rows == num_routers)

    # Create the torus object
    torus = Torus()

    # Create the routers in the torus
    torus.routers = [Router(router_id=i) for i in range(num_routers)]

    # link counter to set unique link ids
    link_count = 0

    # Add all but the remainder nodes to the list of nodes to be uniformly
    # distributed across the network.
    network_nodes = []
    remainder_nodes = []
    for node_index in xrange(len(nodes)):
        if node_index < (len(nodes) - remainder):
            network_nodes.append(nodes[node_index])
        else:
            remainder_nodes.append(nodes[node_index])

    # Connect each node to the appropriate router
    ext_links = []
    for (i, n) in enumerate(network_nodes):
        cntrl_level, router_id = divmod(i, num_routers)
        assert(cntrl_level < cntrls_per_router)
        ext_links.append(ExtLink(link_id=link_count, ext_node=n, 
                                 int_node=torus.routers[router_id]))
        link_count += 1

    # Connect the remainding nodes to router 0.  These should only be
    # DMA nodes.
    for (i, node) in enumerate(remainder_nodes):
        assert(node.type == 'DMA_Controller')
        assert(i < remainder)
        ext_links.append(ExtLink(link_id=link_count, ext_node=node,
                                 int_node=torus.routers[0]))
        link_count += 1

    # Create the torus links.  First row (east-west) links then column
    # (north-south) links
    # column links are given higher weights to implement XY routing
    int_links = []
    for row in xrange(num_rows):
        for col in xrange(num_columns):
            west_id = col + (row * num_columns)
            if (col + 1 < num_columns):
                east_id = (col + 1) + (row * num_columns)
            else:
                east_id = (row * num_columns)
            int_links.append(IntLink(link_id=link_count,
                                     node_a=torus.routers[east_id],
                                     node_b=torus.routers[west_id],
                                     latency=2,
                                     weight=1))
            link_count += 1

    for col in xrange(num_columns):
        for row in xrange(num_rows):
            north_id = col + (row * num_columns)
            if (row + 1 < num_rows):
                south_id = col + ((row + 1) * num_columns)
            else:
                south_id = col
            int_links.append(IntLink(link_id=link_count,
                                     node_a=torus.routers[north_id],
                                     node_b=torus.routers[south_id],
                                     latency=2,
                                     weight=2))
            link_count += 1

    torus.ext_links = ext_links
    torus.int_links = int_links

    return torus