[ADOL-C] OpenMP within an active section

[Kshitij Kulshreshtha]

Hello Chris,

In order to use OpenMP as it is currently implemented in ADOL-C your
parallel section must contain the whole of tracing and the subsequent
derivative evaluation. Otherwise some of the internal data structures
required get lost. The driver functions like jacobian and gradient
currently assume that they are within some parallel section, and unable
to start one on their own.

Best wishes
Kshitij Kulshreshtha

On 03/27/17 20:57, Chris Dembia wrote:
> Hey all:
> 
> I would like to use OpenMP with ADOL-C. I have looked at the OpenMP examples in the ADOL-C source code,
> and I have read the relevant section of the manual. However, I would like to use OpenMP *within* the active
> section, not surrounding the active section. For example:
> 
> 
> ------
> 
> int N = 5;
> short int tag = 0;
> trace_on(tag);
> 
> double* px = new double[N];
> for (int i = 0; i < N; ++i) px[i] = 1.5;
> adouble* x = new adouble[N];
> double* py = new double[N];
> adouble* y = new adouble[N];
> 
> for (int i = 0; i < N; ++i) x[i] <<= px[i];
> 
> #pragma omp parallel ADOLC_OPENMP_NC
> {
>     #pragma omp for
>     for (int i = 0; i < N; ++i) {
>         y[i] = x[i]*x[i];
>     }
> }
> 
> for (int i = 0; i < N; ++i) y[i] >>= py[i];
> 
> trace_off();
> 
> double** J = myalloc(N, N);
> int success = jacobian(tag, N, N, px, J);
> assert(success == 3);
> 
> for (int i = 0; i < N; ++i) {
>     std::cout << "J[" << i << "][" << i << "]: " << J[i][i]
>             << std::endl;
> }
> 
> 
> ------
> 
> This code compiled and ran, but produced an incorrect Jacobian (all zeros). Commenting out the pragmas produced the correct Jacobian.
> 
> Is this possible?
> 
> Thank you,
> Chris Dembia
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-- 
Dr. Kshitij Kulshreshtha

Institut für Mathematik,
Universität Paderborn,
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