std.math.frexp wrong on ARM
The frexp test fails on ARM. I think the mask in line 1491 is wrong: https://github.com/D-Programming-Language/phobos/blob/master/std/math.d#L1491 For doubles, the 63 bit is sign, 62-52 are exponent and 51-0 are mantissa. The mask manipulates the bits 63-48 (ushort, 16bit) 0x8000 is 0b1000 so it preserves the sign, but not the 4 bits of the mantissa? I think it should be 0b1000 (0x800F)? This also fixes the test case on ARM. But I don't know much about this stuff, so I wonder if this is correct? (BTW: Shouldn't we use the binary representation for bitmasks instead?)
Re: std.math.frexp wrong on ARM
On 26/09/12 17:13, Johannes Pfau wrote: The frexp test fails on ARM. I think the mask in line 1491 is wrong: https://github.com/D-Programming-Language/phobos/blob/master/std/math.d#L1491 For doubles, the 63 bit is sign, 62-52 are exponent and 51-0 are mantissa. The mask manipulates the bits 63-48 (ushort, 16bit) 0x8000 is 0b1000 so it preserves the sign, but not the 4 bits of the mantissa? I think it should be 0b1000 (0x800F)? This also fixes the test case on ARM. But I don't know much about this stuff, so I wonder if this is correct? You are correct. I will fix. At least, it's good that the tests caught that.
Re: std.math.frexp wrong on ARM
Am Wed, 26 Sep 2012 17:35:18 +0200 schrieb Don Clugston : > On 26/09/12 17:13, Johannes Pfau wrote: > > The frexp test fails on ARM. I think the mask in line 1491 is > > wrong: > > > > https://github.com/D-Programming-Language/phobos/blob/master/std/math.d#L1491 > > For doubles, the 63 bit is sign, 62-52 are exponent and 51-0 are > > mantissa. > > The mask manipulates the bits 63-48 (ushort, 16bit) > > 0x8000 is 0b1000 > > so it preserves the sign, but not the 4 bits of the mantissa? I > > think it should be > > 0b1000 (0x800F)? > > This also fixes the test case on ARM. > > > > But I don't know much about this stuff, so I wonder if this is > > correct? > > You are correct. I will fix. > > At least, it's good that the tests caught that. OK, thanks. Maybe we could also enhance the tests to test NaN, -NaN, +infinity, -infinity, +0,-0 and probably a denormal?
