[Help-gsl] Check for DENORMAL (subnormal) numbers failed (iee-utils/test.c (185))

[Stephan Petzchen]

Hi,

I am checking gsl for IEEE denormal resp. subnormal numbers. I took the
test case from gsl in: iee-utils/test.c (185).

Unfortunately I do not get the expected results:
1. Exponent is -126 instead -127
2. Mantisse should be: 10000000000000000000000 instead of
00000000000000000000000
3. IEEE Type is Normal instead of denormal.



*Expected output:*
Run: 0
Float: FLT_MIN/2^1
Sign: +
Exponent: -127
Mantisse: 10000000000000000000000
Type: GSL_IEEE_TYPE_DENORMAL

*Actual output:*
Run: 0
Float: FLT_MIN/2^1: 5,877472E-39
Sign: +
Exponent: -126
Mantisse: 00000000000000000000000
Type: GSL_IEEE_TYPE_NORMAL


Maybe someone can give me a hint whats going wrong here.
I am working with the mono framework/C# and gsl 1.15. Testcases for normal
numbers passed as expected.

Thanks in advance.

best,
Stephan

Here is my code:

public const float  GSL_FLT_MIN       = 1.1754943508222875e-38f       ;

float f = (float)gsl_machine.GSL_FLT_MIN;
char[] cmantissa = new
char[]{'1','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0'};
string mantissa="10000000000000000000000";
gsl_ieee_float_rep r = new gsl_ieee_float_rep ();

for (int i = 0; i < 23; i++) {
float x = (float)(f / (float)System.Math.Pow (2.0f, 1f + (float) i));
cmantissa[i] = '1';
mantissa=new String(cmantissa);

gsl_ieee_utils.gsl_ieee_float_to_rep (&f, ref r);

Assert.AreEqual (0, r.sign);
Assert.AreEqual (-127, r.exponent);
Assert.AreEqual (mantissa, r.mantissa);
Assert.AreEqual ((int)GSL_IEEE_TYPE.GSL_IEEE_TYPE_DENORMAL, r.type);