I have a strange bug and i cant find where and what it causes it, i wonder if there are any specs that say anything about floating point calculations and when possible NaNs occur for diffrent cpus (mainly on sony and samsung), i have issues with samsung grand prime where on sony xperia j i have no issues.

Usually CPUs target an IEEE spec, but the manufacturer docs are authoritative if they're available. If they're not then I think experimentation is the only reliable path. You can make a tester that attempts several different types of calculations and captures the results in a short log with a CPU identifier, then emails it to you. Pass that around to various users to gather a database and then post it somewhere (like GDN) so that people don't have to mess with it. You can probably find willing testers with a wide variety of devices at XDA.

If you just need to transfer float values between platforms that are handling them differently you may want to resort to multiplying by a precision factor, truncating to an integer type and then reversing that process on the other end of the connection.

Looks like Samsung Galaxy Grand Prime is a ARM Cortex-A53 and sony xperia j is a ARM Cortex-A5 CPU. So hunting on the ARM site is your best bet if you can find the spec there. From what i can see the cortex-a5 has a 'optional Cortex-A5 FPU' and support ANSI/IEEE Std 754-1985 floating point. A53 has a FPU and support IEE754-2008 and i guess its newer and better. The different ways to runt it might get different result.

http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0041c/Ciheagah.html
http://hugofeng.info/2014/04/25/float-operations-on-arm/

Found where problem lies:

output log:
/**************************************************
vel: 1.4984 m/s
surf_choordlen: 1.78408
Vfi: X 0.0102074 Y 0.00227052 Z 0.999945
ACTUAL_FRAME[i].surface: 4.11654
CFRn: 4134.78 <-- here
skin_percentage_coeff: 0.320026
skin: X 27775.8 Y 6178.39 Z 2.72098e+06
***************************************************/

code:

for (int i=0; i < submerged_tri_count; i++)
if (ACTUAL_FRAME[i].surface > 0.1) //do not coun't anything that is less than 10 cm^2
{

	vec3 element_form_drag = vec3(0.0, 0.0, 0.0);
	vec3 element_skin_drag = vec3(0.0, 0.0, 0.0);
	vec3 cog2pC 	= vectorAB(pos + ROTATION_MAT * CENTER_OF_GRAVITY, ACTUAL_FRAME[i].pC);
	vec3 local_vel = vel + AngVel * cog2pC;
	vec3 vn = Normalize(local_vel);
	float vv = VectorLength(local_vel);
	float v2 = vv;
	vv = vv * vv;
float form_percentage_coeff = absnf( acos(dot(ACTUAL_FRAME[i].normal, vn)) / float(pi) );
if (dot(ACTUAL_FRAME[i].normal, vn) <= 0.0) form_percentage_coeff = form_percentage_coeff*0.8; //suction force
float skin_percentage_coeff = absnf(1.0 - form_percentage_coeff); //due to float inaccuracy
element_form_drag = (-vn) * (form_percentage_coeff * 999.1026 * 0.5 * vv * ACTUAL_FRAME[i].surface); //form drag
ALOG("vel: "+FloatToStr(v2) +" m/s");

/*
 * This is a bit complicated, we project velocity vector onto a tested surface, check choord length and calc reynolds num etc
 * ****************************************************************************************************
 * ****************************************************************************************************
 */

//get choord length
float surf_choordlen = getTriangleChoordLength(
-local_vel, ACTUAL_FRAME[i].normal, ACTUAL_FRAME[i].pC,
ACTUAL_FRAME[i].V[0], ACTUAL_FRAME[i].V[1], ACTUAL_FRAME[i].V[2], true, ACTUAL_FRAME[i].pC);
ALOG("surf_choordlen: "+FloatToStr(surf_choordlen));
if (surf_choordlen > 20.0) surf_choordlen = 3.0;

//calc reynolds number
float Rn = ReynoldsNum(VectorLength(local_vel), surf_choordlen, 0.894);
if (Rn > 2.0)
{
float lg = log10(Rn - 2.0);

float CFRn = 0.075 / (lg * lg);

vec3 Vfi = Normalize( ProjectVectorOnPlane(ACTUAL_FRAME[i].normal, -local_vel) );
ALOG("Vfi: "+POINT_TO_TEXT(Vfi));
ALOG("ACTUAL_FRAME[i].surface: " + FloatToStr(ACTUAL_FRAME[i].surface));
ALOG("CFRn: " + FloatToStr(CFRn));
ALOG("skin_percentage_coeff: " + FloatToStr(skin_percentage_coeff));
element_skin_drag = Vfi * (0.5 * 999.1026 * CFRn * ACTUAL_FRAME[i].surface * skin_percentage_coeff);
ALOG("skin: "+POINT_TO_TEXT(element_skin_drag));
}

Now:

this part of code gives wrong results on samsung:

float Rn = ReynoldsNum(VectorLength(local_vel), surf_choordlen, 0.894);
if (Rn > 2.0)
{
float lg = log10(Rn - 2.0);

float CFRn = 0.075 / (lg * lg);
}



where:

inline float ReynoldsNum(float V, float choord_len, float kinematic_viscosity_of_fluid)
{
return (V*choord_len) / kinematic_viscosity_of_fluid;
}

:/