1*57c64913Sjeremylt // Test polynomial interpolation in 1D 2*57c64913Sjeremylt #include <ceed.h> 3*57c64913Sjeremylt #include <math.h> 4*57c64913Sjeremylt 5*57c64913Sjeremylt #define ALEN(a) (sizeof(a) / sizeof((a)[0])) 6*57c64913Sjeremylt 7*57c64913Sjeremylt static CeedScalar PolyEval(CeedScalar x, CeedInt n, const CeedScalar *p) { 8*57c64913Sjeremylt CeedScalar y = p[n-1]; 9*57c64913Sjeremylt for (CeedInt i=n-2; i>=0; i--) y = y*x + p[i]; 10*57c64913Sjeremylt return y; 11*57c64913Sjeremylt } 12*57c64913Sjeremylt 13*57c64913Sjeremylt int main(int argc, char **argv) { 14*57c64913Sjeremylt Ceed ceed; 15*57c64913Sjeremylt CeedBasis bxl, bxg, bug; 16*57c64913Sjeremylt CeedInt Q = 6; 17*57c64913Sjeremylt const CeedScalar p[] = {1, 2, 3, 4, 5, 6}; // 1 + 2x + 3x^2 + ... 18*57c64913Sjeremylt const CeedScalar x[] = {-1, 1}; 19*57c64913Sjeremylt CeedScalar xq[Q], u[Q], uq[Q], w[Q], sum, error, pint[ALEN(p)+1]; 20*57c64913Sjeremylt 21*57c64913Sjeremylt CeedInit(argv[1], &ceed); 22*57c64913Sjeremylt CeedBasisCreateTensorH1Lagrange(ceed, 1, 1, 2, Q, CEED_GAUSS_LOBATTO, &bxl); 23*57c64913Sjeremylt CeedBasisApply(bxl, 1, CEED_NOTRANSPOSE, CEED_EVAL_INTERP, x, xq); 24*57c64913Sjeremylt for (CeedInt i=0; i<Q; i++) u[i] = PolyEval(xq[i], ALEN(p), p); 25*57c64913Sjeremylt 26*57c64913Sjeremylt CeedBasisCreateTensorH1Lagrange(ceed, 1, 1, 2, Q, CEED_GAUSS, &bxg); 27*57c64913Sjeremylt CeedBasisCreateTensorH1Lagrange(ceed, 1, 1, Q, Q, CEED_GAUSS, &bug); 28*57c64913Sjeremylt CeedBasisApply(bxg, 1, CEED_NOTRANSPOSE, CEED_EVAL_INTERP, x, xq); 29*57c64913Sjeremylt CeedBasisApply(bug, 1, CEED_NOTRANSPOSE, CEED_EVAL_INTERP, u, uq); 30*57c64913Sjeremylt CeedBasisApply(bug, 1, CEED_NOTRANSPOSE, CEED_EVAL_WEIGHT, NULL, w); 31*57c64913Sjeremylt sum = 0; 32*57c64913Sjeremylt for (CeedInt i=0; i<Q; i++) { 33*57c64913Sjeremylt sum += w[i] * uq[i]; 34*57c64913Sjeremylt } 35*57c64913Sjeremylt pint[0] = 0; 36*57c64913Sjeremylt for (CeedInt i=0; i<(CeedInt)ALEN(p); i++) pint[i+1] = p[i] / (i+1); 37*57c64913Sjeremylt error = sum - PolyEval(1, ALEN(pint), pint) + PolyEval(-1, ALEN(pint), pint); 38*57c64913Sjeremylt if (!(error < 1e-10)) 39*57c64913Sjeremylt printf("Error %e sum %g exact %g\n", error, sum, 40*57c64913Sjeremylt PolyEval(1, ALEN(pint), pint) - PolyEval(-1, ALEN(pint), pint)); 41*57c64913Sjeremylt 42*57c64913Sjeremylt CeedBasisDestroy(&bxl); 43*57c64913Sjeremylt CeedBasisDestroy(&bxg); 44*57c64913Sjeremylt CeedBasisDestroy(&bug); 45*57c64913Sjeremylt CeedDestroy(&ceed); 46*57c64913Sjeremylt return 0; 47*57c64913Sjeremylt } 48