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Commit49f81d5

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tests/float/math_constants.py: Test actual e and pi constant values.
The existing test for `math.e` and `math.pi` constants can fail on certaintargets if the functions `math.exp()` and/or `math.cos()` are not accurateenough (eg out by an LSB of float precision). For example this testcurrently fails on PYBD_SF6 which uses double precision floats (and that'sdue to the `lib/libm_dbl/exp.c` implementation not being exact).This commit changes this constant test so that it tests the actual constantvalue, not the evaluation of `exp()` and `cos()` functions.Signed-off-by: Damien George <damien@micropython.org>
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‎tests/float/math_constants.py

Lines changed: 23 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -1,11 +1,30 @@
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# Tests various constants of the math module.
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importsys
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try:
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importmath
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frommathimportexp,cos
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fromarrayimportarray
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frommathimporte,pi
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exceptImportError:
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print("SKIP")
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raiseSystemExit
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print(math.e==exp(1.0))
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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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iffloat("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(cos(math.pi))
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print("e:",e==e_truthor (e,e_truth,e-e_truth))
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print("pi:",pi==pi_truthor (pi,pi_truth,pi-pi_truth))

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