Overflows and underflows are logged as warnings for all assignment,
plus, minus, and multiplication operations when the
is set to
on. For example, try the following:
Create a signed
that is a vector of values from 1 to 5, with 8-bit word length and
6-bit fraction length.
a = fi(1:5,1,8,6);
a, and indicate that you will specify
the sum and product word and fraction lengths.
F = a.fimath; F.SumMode = 'SpecifyPrecision'; F.ProductMode = 'SpecifyPrecision'; a.fimath = F;
and turn on overflow and underflow logging.
P = fipref; P.LoggingMode = 'on';
P.NumericTypeDisplay = 'none'; P.FimathDisplay = 'none';
Specify the sum and product word and fraction lengths.
a.SumWordLength = 16; a.SumFractionLength = 15; a.ProductWordLength = 16; a.ProductFractionLength = 15;
Warnings are displayed for overflows and underflows in assignment operations. For example, try:
a(1) = pi Warning: 1 overflow occurred in the fi assignment operation. a = 1.9844 1.9844 1.9844 1.9844 1.9844 a(1) = double(eps(a))/10 Warning: 1 underflow occurred in the fi assignment operation. a = 0 1.9844 1.9844 1.9844 1.9844
Warnings are displayed for overflows and underflows in addition and subtraction operations. For example, try:
a+a Warning: 12 overflows occurred in the fi + operation. ans = 0 1.0000 1.0000 1.0000 1.0000 a-a Warning: 8 overflows occurred in the fi - operation. ans = 0 0 0 0 0
Warnings are displayed for overflows and underflows in multiplication operations. For example, try:
a.*a Warning: 4 product overflows occurred in the fi .* operation. ans = 0 1.0000 1.0000 1.0000 1.0000 a*a' Warning: 4 product overflows occurred in the fi * operation. Warning: 3 sum overflows occurred in the fi * operation. ans = 1.0000
The final example above is a complex multiplication that requires both multiplication and addition operations. The warnings inform you of overflows and underflows in both.
Because overflows and underflows are logged as warnings, you
can use the
dbstop MATLAB® function
with the syntax
dbstop if warning
to find the exact lines in a file that are causing overflows or underflows.
dbstop if warning fi:underflow
to stop only on lines that cause an underflow. Use
dbstop if warning fi:overflow
to stop only on lines that cause an overflow.
is set to
on, you can use the following functions
to return logged information about assignment and creation operations
to the MATLAB command line:
Returns the maximum real-world value
Returns the minimum value
Returns the number of overflows
Returns the number of underflows
LoggingMode must be set to
you perform any operation in order to log information about it. To
clear the log, use the function
For example, consider the following. First turn logging on, then perform operations, and then finally get information about the operations:
fipref('LoggingMode','on'); x = fi([-1.5 eps 0.5], true, 16, 15); x(1) = 3.0; maxlog(x) ans = 1.0000 minlog(x) ans = -1 noverflows(x) ans = 2 nunderflows(x) ans = 1
Next, reset the log and request the same information again. Note that the functions return empty , because logging has been reset since the operations were run:
resetlog(x) maxlog(x) ans =  minlog(x) ans =  noverflows(x) ans =  nunderflows(x) ans =