49f81d5046
The existing test for `math.e` and `math.pi` constants can fail on certain targets if the functions `math.exp()` and/or `math.cos()` are not accurate enough (eg out by an LSB of float precision). For example this test currently fails on PYBD_SF6 which uses double precision floats (and that's due to the `lib/libm_dbl/exp.c` implementation not being exact). This commit changes this constant test so that it tests the actual constant value, not the evaluation of `exp()` and `cos()` functions. Signed-off-by: Damien George <damien@micropython.org>
30 lines
1 KiB
Python
30 lines
1 KiB
Python
# Tests various constants of the math module.
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import sys
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try:
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from array import array
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from math import e, pi
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except ImportError:
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print("SKIP")
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raise SystemExit
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# Hexadecimal representations of e and pi constants.
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e_truth_single = 0x402DF854
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pi_truth_single = 0x40490FDB
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e_truth_double = 0x4005BF0A8B145769
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pi_truth_double = 0x400921FB54442D18
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# Detect the floating-point precision of the system, to determine the exact values of
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# the constants (parsing the float from a decimal string can lead to inaccuracies).
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if float("1e300") == float("inf"):
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# Single precision floats.
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e_truth = array("f", e_truth_single.to_bytes(4, sys.byteorder))[0]
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pi_truth = array("f", pi_truth_single.to_bytes(4, sys.byteorder))[0]
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else:
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# Double precision floats.
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e_truth = array("d", e_truth_double.to_bytes(8, sys.byteorder))[0]
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pi_truth = array("d", pi_truth_double.to_bytes(8, sys.byteorder))[0]
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print("e:", e == e_truth or (e, e_truth, e - e_truth))
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print("pi:", pi == pi_truth or (pi, pi_truth, pi - pi_truth))
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