Adjust degree-based trig functions for more portability.
The buildfarm isn't very happy with the results of commit e1bd684a34.
To try to get the expected exact results everywhere:
* Replace M_PI / 180 subexpressions with a precomputed constant, so that
the compiler can't decide to rearrange that division with an adjacent
operation. Hopefully this will fix failures to get exactly 0.5 from
sind(30) and cosd(60).
* Add scaling to ensure that tand(45) and cotd(45) give exactly 1; there
was nothing particularly guaranteeing that before.
* Replace minus zero by zero when tand() or cotd() would output that;
many machines did so for tand(180) and cotd(270), but not all. We could
alternatively deem both results valid, but that doesn't seem likely to
be what users will want.
This commit is contained in:
Tom Lane
parent
6ae4c8de00
commit
73193d82d7
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@ -31,6 +31,9 @@
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#define M_PI 3.14159265358979323846
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#endif
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/* Radians per degree, a.k.a. PI / 180 */
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#define RADIANS_PER_DEGREE 0.0174532925199432957692
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/* Visual C++ etc lacks NAN, and won't accept 0.0/0.0. NAN definition from
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* http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vclang/html/vclrfNotNumberNANItems.asp
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*/
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@ -1919,7 +1922,7 @@ datan2d(PG_FUNCTION_ARGS)
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static double
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sind_0_to_30(double x)
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{
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return (sin(x * (M_PI / 180.0)) / sin(30.0 * (M_PI / 180.0))) / 2.0;
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return (sin(x * RADIANS_PER_DEGREE) / sin(30.0 * RADIANS_PER_DEGREE)) / 2.0;
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}
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@ -1931,8 +1934,8 @@ sind_0_to_30(double x)
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static double
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cosd_0_to_60(double x)
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{
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return 1.0 - ((1.0 - cos(x * (M_PI / 180.0))) /
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(1.0 - cos(60.0 * (M_PI / 180.0)))) / 2.0;
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return 1.0 - ((1.0 - cos(x * RADIANS_PER_DEGREE)) /
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(1.0 - cos(60.0 * RADIANS_PER_DEGREE))) / 2.0;
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}
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@ -2030,8 +2033,9 @@ Datum
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dcotd(PG_FUNCTION_ARGS)
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{
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float8 arg1 = PG_GETARG_FLOAT8(0);
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int sign = 1;
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float8 result;
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int sign = 1;
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static float8 cot45 = 0.0;
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/*
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* Per the POSIX spec, return NaN if the input is NaN and throw an error
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@ -2071,6 +2075,26 @@ dcotd(PG_FUNCTION_ARGS)
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result = sign * cosd_q1(arg1) / sind_q1(arg1);
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/*
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* We want cotd(45) to be exactly 1, but the above computation might've
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* produced something different, so scale to get the right result. To
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* avoid redoing cosd_q1(45) / sind_q1(45) many times, and to prevent the
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* compiler from maybe rearranging the calculation, cache that value in a
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* static variable.
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*/
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if (cot45 == 0.0)
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cot45 = cosd_q1(45.0) / sind_q1(45.0);
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result /= cot45;
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/*
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* On some machines, we get cotd(270) = minus zero, but this isn't always
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* true. For portability, and because the user constituency for this
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* function probably doesn't want minus zero, force it to plain zero.
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*/
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if (result == 0.0)
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result = 0.0;
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CHECKFLOATVAL(result, true /* cotd(0) == Inf */ , true);
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PG_RETURN_FLOAT8(result);
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}
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@ -2133,8 +2157,9 @@ Datum
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dtand(PG_FUNCTION_ARGS)
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{
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float8 arg1 = PG_GETARG_FLOAT8(0);
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int sign = 1;
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float8 result;
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int sign = 1;
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static float8 tan45 = 0.0;
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/*
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* Per the POSIX spec, return NaN if the input is NaN and throw an error
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@ -2174,6 +2199,26 @@ dtand(PG_FUNCTION_ARGS)
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result = sign * sind_q1(arg1) / cosd_q1(arg1);
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/*
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* We want tand(45) to be exactly 1, but the above computation might've
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* produced something different, so scale to get the right result. To
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* avoid redoing sind_q1(45) / cosd_q1(45) many times, and to prevent the
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* compiler from maybe rearranging the calculation, cache that value in a
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* static variable.
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*/
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if (tan45 == 0.0)
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tan45 = sind_q1(45.0) / cosd_q1(45.0);
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result /= tan45;
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/*
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* On some machines, we get tand(180) = minus zero, but this isn't always
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* true. For portability, and because the user constituency for this
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* function probably doesn't want minus zero, force it to plain zero.
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*/
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if (result == 0.0)
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result = 0.0;
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CHECKFLOATVAL(result, true /* tand(90) == Inf */ , true);
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PG_RETURN_FLOAT8(result);
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}
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@ -2188,7 +2233,7 @@ degrees(PG_FUNCTION_ARGS)
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float8 arg1 = PG_GETARG_FLOAT8(0);
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float8 result;
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result = arg1 * (180.0 / M_PI);
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result = arg1 / RADIANS_PER_DEGREE;
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CHECKFLOATVAL(result, isinf(arg1), arg1 == 0);
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PG_RETURN_FLOAT8(result);
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@ -2214,7 +2259,7 @@ radians(PG_FUNCTION_ARGS)
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float8 arg1 = PG_GETARG_FLOAT8(0);
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float8 result;
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result = arg1 * (M_PI / 180.0);
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result = arg1 * RADIANS_PER_DEGREE;
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CHECKFLOATVAL(result, isinf(arg1), arg1 == 0);
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PG_RETURN_FLOAT8(result);
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@ -467,13 +467,13 @@ FROM generate_series(0, 360, 15) AS t(x);
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135 | | | -1 | -1
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150 | 0.5 | | |
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165 | | | |
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180 | 0 | -1 | -0 | -Infinity
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180 | 0 | -1 | 0 | -Infinity
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195 | | | |
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210 | -0.5 | | |
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225 | | | 1 | 1
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240 | | -0.5 | |
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255 | | | |
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270 | -1 | 0 | -Infinity | -0
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270 | -1 | 0 | -Infinity | 0
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285 | | | |
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300 | | 0.5 | |
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315 | | | -1 | -1
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@ -465,13 +465,13 @@ FROM generate_series(0, 360, 15) AS t(x);
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135 | | | -1 | -1
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150 | 0.5 | | |
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165 | | | |
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180 | 0 | -1 | -0 | -Infinity
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180 | 0 | -1 | 0 | -Infinity
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195 | | | |
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210 | -0.5 | | |
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225 | | | 1 | 1
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240 | | -0.5 | |
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255 | | | |
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270 | -1 | 0 | -Infinity | -0
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270 | -1 | 0 | -Infinity | 0
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285 | | | |
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300 | | 0.5 | |
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315 | | | -1 | -1
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@ -465,13 +465,13 @@ FROM generate_series(0, 360, 15) AS t(x);
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135 | | | -1 | -1
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150 | 0.5 | | |
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165 | | | |
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180 | 0 | -1 | -0 | -Infinity
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180 | 0 | -1 | 0 | -Infinity
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195 | | | |
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210 | -0.5 | | |
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225 | | | 1 | 1
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240 | | -0.5 | |
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255 | | | |
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270 | -1 | 0 | -Infinity | -0
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270 | -1 | 0 | -Infinity | 0
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285 | | | |
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300 | | 0.5 | |
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315 | | | -1 | -1
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@ -467,13 +467,13 @@ FROM generate_series(0, 360, 15) AS t(x);
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135 | | | -1 | -1
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150 | 0.5 | | |
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165 | | | |
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180 | 0 | -1 | -0 | -Infinity
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180 | 0 | -1 | 0 | -Infinity
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195 | | | |
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210 | -0.5 | | |
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225 | | | 1 | 1
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240 | | -0.5 | |
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255 | | | |
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270 | -1 | 0 | -Infinity | -0
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270 | -1 | 0 | -Infinity | 0
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285 | | | |
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300 | | 0.5 | |
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315 | | | -1 | -1
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