generate-trig-table.py

#!/usr/bin/env python
#
# Copyright 2013 the V8 project authors. All rights reserved.
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# modification, are permitted provided that the following conditions are
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# This is a utility for populating the lookup table for the
# approximation of trigonometric functions.

import sys, math

SAMPLES = 1800

TEMPLATE = """\
// Copyright 2013 Google Inc. All Rights Reserved.

// This file was generated from a python script.

#include "v8.h"
#include "trig-table.h"

namespace v8 {
namespace internal {

  const double TrigonometricLookupTable::kSinTable[] =
      { %(sine_table)s };
  const double TrigonometricLookupTable::kCosXIntervalTable[] =
      { %(cosine_table)s };
  const int TrigonometricLookupTable::kSamples = %(samples)i;
  const int TrigonometricLookupTable::kTableSize = %(table_size)i;
  const double TrigonometricLookupTable::kSamplesOverPiHalf =
      %(samples_over_pi_half)s;

} }  // v8::internal
"""

def main():
  pi_half = math.pi / 2
  interval = pi_half / SAMPLES
  sin = []
  cos_times_interval = []
  table_size = SAMPLES + 2

  for i in range(0, table_size):
    sample = i * interval
    sin.append(repr(math.sin(sample)))
    cos_times_interval.append(repr(math.cos(sample) * interval))

  output_file = sys.argv[1]
  output = open(str(output_file), "w")
  output.write(TEMPLATE % {
    'sine_table': ','.join(sin),
    'cosine_table': ','.join(cos_times_interval),
    'samples': SAMPLES,
    'table_size': table_size,
    'samples_over_pi_half': repr(SAMPLES / pi_half)
  })

if __name__ == "__main__":
  main()