// since each cell is connected via gap junctions to its four neighbors
// it makes sense to divide the network into blocks with each host
// handling a separate block with as equal as possible the same number
// of blocks in a row as in a column.
// ie. balance would be perfect if nh2=sqrt(pc.nhost) is an integer (the
// usual case) and also if Nx/nh2 and Ny/nh2 are both integers
// But to get things working, for now try roundrobin.
// ie easy balance at the expense of excessive communication
ncell = Nx*Ny
iterator pcitr() {local i, gid
i = 0
for (gid = pc.id; gid < ncell; gid += pc.nhost) {
$&1 = gid
$&2 = i
iterator_statement
i += 1
}
}
// Here is the block implementation, keep the blocks roughly square
// If we eventully use section connect in place of HalfGap as much
// as possible then we would want the block to be as long as possible.
// There are pc.nhost blocks. Assume Nx, Ny, and nblock are powers of 2.
// No attempt at optimality.
// args: Nx, Ny, nblocks
// output fills the global variables: Nx, Ny, nblock, ncell, ncellperlock,
// blockNx, blockNy, xblock, yblock
func is_power2() { local x
x = log($1)/log(2)
return x == int(x)
}
func blocksizes() {
Nx = $1
if (!is_power2(Nx)) return 0
Ny = $2
if (!is_power2(Ny)) return 0
nblock = $3
if (!is_power2(nblock)) return 0
ncell = Nx*Ny
ncellperblock = ncell/nblock
// Assume ncellperblock is a nonnegative power of 2
// need blockNx * blockNy = ncellperblock
// with contraint that Nx/blockNx and Ny/blockNy are integers.
blockNy = 1
blockNx = ncellperblock/blockNy
for (blockNy = 1; Ny%blockNy == 0 ; blockNy *= 2) {
blockNx = ncellperblock/blockNy
if (Nx%blockNx != 0) { continue }
if (blockNy >= blockNx) { break }
}
return 1
}
if (block_distrib != 0) {
block_distrib = blocksizes(Nx, Ny, pc.nhost)
if (block_distrib) {
load_file("block_distrib.hoc") // replace iterator pcitr
if (pc.id == 0) {
printf("Block gid distribution blockNx = %d blockNy = %d\n", blockNx, blockNy)
}
}else{
if (pc.id == 0) {
printf("One or more of Nx, Ny, rank is not a power of 2. Use round robin gid distribution\n")
}
}
pc.barrier()
}
