triangle_reader.py

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"""Provides functions for reading triangle files into OP2 data structures."""

from pyop2 import op2
import numpy as np

def read_triangle(f):
    """Read the triangle file with prefix f into OP2 data strctures. Presently
    only .node and .ele files are read, attributes are ignored, and there may
    be bugs. The dat structures are returned as:

        (nodes, coords, elements, elem_node)

    These items have type:

        (Set, Dat, Set, Map)
    """
    # Read nodes
    with open(f+'.node') as h:
        num_nodes = int(h.readline().split()[0])
        node_values = [0]*num_nodes
        for line in h:
            if line[0] == '#':
                continue
            vals = line.split()
            node = int(vals[0])-1
            x, y = [ float(x) for x in vals[1:3] ]
            node_values[node] = (x,y)

    nodes = op2.Set(num_nodes,"nodes")
    coords = op2.Dat(nodes, 2, np.asarray(node_values,dtype=np.float64), np.float64, "coords")

    # Read elements
    with open(f+'.ele') as h:
        num_tri, nodes_per_tri, num_attrs = \
            map(lambda x: int(x), h.readline().split())
        map_values = [0]*num_tri
        for line in h:
            if line[0] == '#':
                continue
            vals = line.split()
            tri = int(vals[0])
            ele_nodes = [ int(x)-1 for x in vals[1:nodes_per_tri+1] ]
            map_values[tri-1] = ele_nodes
    # Ref: http://stackoverflow.com/questions/952914/making-a-flat-list-out-of-list-of-lists-in-python
    flat_map = [ item for sublist in map_values for item in sublist ]

    elements = op2.Set(num_tri, "elements")
    elem_node = op2.Map(elements, nodes, 3, flat_map, "elem_node")

    return nodes, coords, elements, elem_node