literal double value output by omc exceeds DBL_MAX

[john.pye@…]

Hi there

While using omc from the Nightly builds, OpenModelica 1.13.0~dev-536-g587d18b, as well as with previous version 1.12, we receive compiler warnings as follows:

SimpleSystem.c:1160:90: warning: magnitude of floating-point constant too large

for type 'double'; maximum is 1.7976931348623157E+308 [-Wliteral-range]

.../* pri.nextTimeEventScaled DISCRETE */,1.797693134862316e+308);

SimpleSystem.c:1161:152: warning: magnitude of floating-point constant too large

for type 'double'; maximum is 1.7976931348623157E+308 [-Wliteral-range]

.../* pri.nextTimeEventScaled DISCRETE */:1.797693134862316e+308);

The function that is causing this problem in the OMC C-code output is:

/*

equation index: 150
type: WHEN

when {$whenCondition1} then

pri._nextTimeEvent = if pri.nextTimeEventScaled < 1.797693134862316e+308 then pri.nextTimeEventScaled else 1.797693134862316e+308;

end when;
*/

void SimpleSystem_eqFunction_150(DATA *data, threadData_t *threadData)
{

TRACE_PUSH
const int equationIndexes[2] = {1,150};
modelica_boolean tmp29;
if((data->localData[0]->booleanVars[0] /* $whenCondition1 DISCRETE */ && !data->simulationInfo->booleanVarsPre[0] /* $whenCondition1 DISCRETE */ /* edge */))
{

tmp29 = Less(data->localData[0]->realVars[70] /* pri.nextTimeEventScaled DISCRETE */,1.797693134862316e+308);
data->localData[0]->realVars[69] /* pri.nextTimeEvent DISCRETE */ = (tmp29?data->localData[0]->realVars[70] /* pri.nextTimeEventScaled DISCRETE */:1.797693134862316e+308);

}
TRACE_POP

}

On close inspection, you can see that the literal double value in the code is slightly rounded up from DBL_MAX.

I think the best solution here would be for the C code from Modelica to output either the macro 'DBL_MAX' or else a value that is safely less than DBL_MAX eg half its value.

Cheers
JP

PS if more details are needed, you can reproduce this bug directly following the instructions at ​https://github.com/SolarTherm/SolarTherm/wiki/Building-SolarTherm.

[john.pye@…]

Further to this, we found that by adjusting the value of DBL_MAX, which is hard-wired into the code of /usr/lib/omlibrary/Modelica 3.2.2/Blocks/Sources.mo (line 2288) "const Real DBL_MAX = 1.79....e+308", we were able to make the compiler warning go away. We rounded the last decimal in the mantissa down to 0.

Hope that helps!

[Martin Sjölund]

The MSL code is probably wrong and should ideally use Constants.inf (and if that is too small, ModelicaServices.Machine.inf should be increased). MSL issues go to: ​https://github.com/modelica/Modelica/issues/new

From OpenModelica's point of view, perhaps we could tweak the value to be output such that GCC doesn't give warnings, but the code still runs fine, right?

[john.pye@…]

Filed (sort of) as ​https://github.com/modelica/Modelica/issues/2435

[john.pye@…]

Another option would be to explicitly suppress this particular warning from GCC... but only if we can be sure it won't cause issues else where. One question I had was what value GCC casts this overflowing DBL_MAX to? No risk of overflow, is there?

I don't know how you can tweak the value without changing the Modelica Sources.mo file...?