## digitalmars.D - std.math.frexp wrong on ARM

- Johannes Pfau (13/13) Sep 26 2012 The frexp test fails on ARM. I...
- Don Clugston (3/15) Sep 26 2012 You are correct. I will fix....
- Johannes Pfau (5/25) Sep 27 2012 OK, thanks....

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 0b1000000000000000 so it preserves the sign, but not the 4 bits of the mantissa? I think it should be 0b1000000000001111 (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?)

Sep 26 2012

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 0b1000000000000000 so it preserves the sign, but not the 4 bits of the mantissa? I think it should be 0b1000000000001111 (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.

Sep 26 2012

Am Wed, 26 Sep 2012 17:35:18 +0200 schrieb Don Clugston <dac nospam.com>: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 0b1000000000000000 so it preserves the sign, but not the 4 bits of the mantissa? I think it should be 0b1000000000001111 (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?

Sep 27 2012