MATLAB: Invalid use of operator.

invalid operator

I'm try to perfom the simple equation:

i.e. the square root of the integral of the square of the signal (averaged av(t)).

But I keep getting the error message "Invalid use of operator.". Please help, I'm very new to MATLAB

Where av(t) = -8.1284e-05

t_full = 1.2726e+04

av(t) = -8.1284e-05
T = 1.2726e+04
int = sqrt(@(t).* (av(t))^2);
MSDV = quadgk(int,0,t_full);

Best Answer

int = sqrt(@(t).* (av(t))^2);

That is not valid. You're not multiplying the square of av(t) by anything.

int = sqrt(@(t) (av(t))^2);

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MATLAB: Conditional statements and ODEs

Numerical ODE solvers don’t like discontinuities, so you have to ‘break’ the integration into two parts, using the last output of the first integration as the initial condition for the second. I coded ‘rhs’ as an anonymous function because it’s easier.

See if this does what you want:

Funderin = 1.7153;
Funderout = 1.7153;
Fsep= 0.9406;
MassUnders = 12.0069;
rhs = @(t,Cu,Cu_in) (Funderin* Cu_in - Funderout*Cu - Fsep*Cu)/MassUnders;
N = 25;
tspan1 = linspace(0, 3, N);
tspan2 = linspace(3, 5, N);
Cu_in = 0.9717
Cui = 0;
[t,Cu]=ode45( @(t,Cu) rhs(t,Cu,Cu_in), tspan1, Cui);
Cu_int = [t, Cu];
Cu_in = 0;
Cui = Cu(end);
[t,Cu]=ode45( @(t,Cu) rhs(t,Cu,Cu_in), tspan2, Cui);
Cu_int = [Cu_int; t, Cu];
plot(Cu_int(:,1),Cu_int(:,2));
xlabel('t'); ylabel('Cu');

EDIT — Forgot to include the plot call. Added it.

MATLAB: Using a templated CUDA kernel via MATLAB

Alex,

Allow me to quote from the help for parallel.gpu.CUDAKernel and try to parse it for you. If you have suggestions for how to improve the wording, please let me know! "If specified, FUNC must be a string that unambiguously defines the appropriate kernel entry name in the PTX file. If FUNC is omitted, the PTX file must contain only a single entry point"

In your case, the get_nans.cu defines two global functions:

get_nans<double>
get_nans<float>

and the get_nans.ptx defines the corresponding two entry points:

Z16get_nansIdEvPT_PKS0_S3_S3_PKiS5 (For the double function)
Z16get_nansIfEvPT_PKS0_S3_S3_PKiS5 (For the float function)

When you create the parallel.gpu.CUDAKernel, it is ambiguous whether you want to invoke the double or the float function. Therefore, you must provide the name of the entry point you want to use and construct either the double or the float version:

kDouble = parallel.gpu.CUDAKernel( 'get_nans.ptx', 'get_nans.cu', '_Z16get_nansIdEvPT_PKS0_S3_S3_PKiS5_'); kFloat = parallel.gpu.CUDAKernel( 'get_nans.ptx', 'get_nans.cu', '_Z16get_nansIfEvPT_PKS0_S3_S3_PKiS5_');

Now, this almost works, but not quite because the parser in parallel.gpu.CUDAKernel cannot parse the template function definition. Therefore, we stop using this way of constructing the CUDAKernel:

KERN = parallel.gpu.CUDAKernel(PTXFILE, CUFILE, FUNC)

and use this one instead:

KERN = parallel.gpu.CUDAKernel(PTXFILE, CPROTO, FUNC)

We then end up with:

kDouble = parallel.gpu.CUDAKernel( 'get_nans.ptx', 'double* out, const int* dims', '_Z16get_nansIdEvPT_PKS0_S3_S3_PKiS5_');

kFloat = parallel.gpu.CUDAKernel( 'get_nans.ptx', 'float* out, const int * dims', '_Z16get_nansIfEvPT_PKS0_S3_S3_PKiS5_');

Does this make sense?

Best,

Narfi

Best Answer

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MATLAB: Conditional statements and ODEs

MATLAB: Using a templated CUDA kernel via MATLAB

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