test_recarray.py

"""
Simulate a read_where() query on a pytables table

Issue: Using MKL 11.3 the numexpr NumExpr query is wrong
works with without MKL.
works with and without MKL using a single column.

It seems the VML log10 function is not correctly called.
The table has different memory mapping as a single column.
It seems the VML call does not account for this correctly.

"""
import numpy
import numexpr
from numexpr.necompiler import NumExpr, stringToExpression

INPUT = [1.e12, 1.e13, 1.e14, 1.e15, 1.e16]
RESULT = 3

def make_NumExpr():
    """ Make a NumExpr object exactly as pytables """

    mysig = [('f1', float)]
    typemap = {'f1': float}
    strexpr = stringToExpression('log10(f1) >= 14.', typemap, {})
    print "DEBUG: strexpr ", strexpr

    return NumExpr(strexpr, mysig)

def make_recarray(val):
    """ make a pytables table-like numpy.rec.array """

    l = len(val)
    data = numpy.rec.array(None, formats=('f4,f4,f4'), shape=(l,))
    data['f0']= l*[1.]
    data['f1']= val
    data['f2']= l*[1.e14]

    return data

if __name__ == '__main__':
    print "numexpr version: ", numexpr.__version__
    print "VML: ", numexpr.get_vml_version()

    expr = make_NumExpr()
    table = make_recarray(INPUT)

    dt = [('f1', numpy.float32)]
    single_column = numpy.array(table['f1'], dtype=dt)

    recarrs = [single_column, table]
    for recarr in recarrs:
        # simulate pytables get_nested_field() 
        field = recarr['f1']
        # this is the call pytables makes in tables.conditions.call_on_recarray()
        result = expr(*[field])
        print "DEBUG: strides of this recarray: ", field.strides
        if sum(result) == RESULT:
            print "Succes!: ", result
        else:
            print "FAIL!: ", result