Problems with multiplications of doubles and/or floats

[Matt]

Hi there,

I am trying to multiply doubles with floats (actually I tried every
possible combination by now) and it never works (well, it does something
but it is always wrong). I have no idea what it is and where to look for
help, maybe some of you know?

double=float*double; (or every possible combination of it). An example:

0.3 * 0.7 would result in 1.7 (with lots more digits). Anyone any idea?
If I change the types of the variables I think the result stays the same
(but I am not 100% sure)...

Jens

Show us the format string for the print statement that prints the
incorrect value.

 

[Michiel Salters]

Hi there,

I am trying to multiply doubles with floats (actually I tried every
possible combination by now) and it never works (well, it does something
but it is always wrong). I have no idea what it is and where to look for
help, maybe some of you know?

double=float*double; (or every possible combination of it). An example:

0.3 * 0.7 would result in 1.7 (with lots more digits). Anyone any idea?
If I change the types of the variables I think the result stays the same
(but I am not 100% sure)...

Jens

Well, you can't actually multiply a double and a float. However, if you
write 0.3 * 0.7f, you will get a float->double conversion, so in fact
you will multiply two doubles. Why don't you add a few lines to your
main printing this? If it fails, remove parts of your program until
it work. If it works, move these test lines closer to your problem area
until it fails.

Regards,
Michiel Salters

 

[Benoit Mathieu]

Hi there,

I am trying to multiply doubles with floats (actually I tried every
possible combination by now) and it never works (well, it does something
but it is always wrong). I have no idea what it is and where to look for
help, maybe some of you know?

double=float*double; (or every possible combination of it). An example:

0.3 * 0.7 would result in 1.7 (with lots more digits). Anyone any idea?
If I change the types of the variables I think the result stays the same
(but I am not 100% sure)...

Jens

Some ideas :

Maybe you have macros redefining something (i had a look at
the code on cvs, and i saw things like #define XY 0, so
maybe some very common names are defined somewhere...

Stack overflow ? (does that kind of thing still exist
nowadays ?) (try adding some dummy variable declarations in
the function (double bigarray[1000] or so)

Check again that optimizations are turned off (I don't see
other reasons for the debugger to hop back and forth in the
code...)

Also, try to turn off cpu specific assembly code generation
(-i686 or so...)

 

[Matt]

Hi there,

I am trying to multiply doubles with floats (actually I tried every
possible combination by now) and it never works (well, it does something
but it is always wrong). I have no idea what it is and where to look for
help, maybe some of you know?

double=float*double; (or every possible combination of it). An example:

0.3 * 0.7 would result in 1.7 (with lots more digits). Anyone any idea?
If I change the types of the variables I think the result stays the same
(but I am not 100% sure)...

Jens

What was the resolution of this?