2407 fix safe as check power8

Created by: bartlettroscoe

CC: @trilinos/teuchos, @mhoemmen

Description

This PR branch improves the outputting of some of the Teuchos type conversion code unit tests and it fixes a problem with a safeAs() test on power8 systems. This addresses issue #2407 (closed).

Now, building and running with:

./TeuchosCore_TypeConversions_UnitTest.exe --test=stringToReal --details=ALL

passes as shown below on two systems.

With this change, on my Linux machine crf450 the unit test output shows:

1. asSafe_stringToReal_UnitTest ... 
 minLD = -1.19e+4932
 minusOneLD = -1
 maxLD = 1.19e+4932
 ...
 sizeof_long_double = 16
 sizeof_double = 8
 max_exponent10_long_double = 4932
 max_exponent10_double = 308
 Testing converting from 'long double' to 'double' that does not fit ...
 Test that code {valD = asSafe<double>(valToString(minLD));} throws std::range_error: passed
 
 Exception message for expected exception:
 
  /ascldap/users/rabartl/Trilinos.base/Trilinos/packages/teuchos/core/src/Teuchos_as.hpp:558:
  
  Throw number = 3
  
  Throw test that evaluated to true: errno == ERANGE && (val != 0)
  
  Teuchos::ValueTypeConversionTraits<double, std::string>::convert: The value in the given string "-1.189731495357231765021263853e+4932" overflows double.
  
 valD = -1
 Test that code {valD = asSafe<double>(valToString(maxLD));} throws std::range_error: passed
 
 Exception message for expected exception:
 
  /ascldap/users/rabartl/Trilinos.base/Trilinos/packages/teuchos/core/src/Teuchos_as.hpp:558:
  
  Throw number = 4
  
  Throw test that evaluated to true: errno == ERANGE && (val != 0)
  
  Teuchos::ValueTypeConversionTraits<double, std::string>::convert: The value in the given string "1.189731495357231765021263853e+4932" overflows double.
  
 valD = -1
 Testing string -> long double conversions ...
 ...
 [Passed] (0.000535 sec)

Total Time: 0.000829 sec

Summary: total = 116, run = 1, passed = 1, failed = 0

End Result: TEST PASSED

So it runs the unit tests Testing converting from 'long double' to 'double' that does not fit gets run since both the sizeof() and max_exponent10 values for long double are larger than for double. So these important tests run.

But when I run this unit test now on the power8 machine ride with the the gnu-debug-openmp build as shown above, it shows:

1. asSafe_stringToReal_UnitTest ... 
 minLD = -1.8e+308
 minusOneLD = -1
 maxLD = 1.8e+308
 ...
 sizeof_long_double = 16
 sizeof_double = 8
 max_exponent10_long_double = 308
 max_exponent10_double = 308
 Testing string -> long double conversions ...
  ...
 [Passed] (0.000418 sec)

Total Time: 0.000783 sec

Summary: total = 116, run = 1, passed = 1, failed = 0

End Result: TEST PASSED

See, that shows that on this machine max_exponent10_long_double = max_exponent10_double = 308 and the checks printed in the section Testing converting from 'long double' to 'double' that does not fit are skipped and instead it goes straight to Testing string -> long double conversions.

I think this is the right thing to do to fix these tests and it informs something about this system.