29 lines
642 B
C
29 lines
642 B
C
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// This is from 'Writing R Extensions' section 5.10.1
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// BUT slowed down by using REAL() on each access which proves to be rather costly
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#include <R.h>
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#include <Rdefines.h>
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SEXP convolve7(SEXP a, SEXP b)
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{
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int i, j, na, nb, nab;
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SEXP ab;
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PROTECT(a = AS_NUMERIC(a));
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PROTECT(b = AS_NUMERIC(b));
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na = LENGTH(a); nb = LENGTH(b); nab = na + nb - 1;
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PROTECT(ab = NEW_NUMERIC(nab));
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for(i = 0; i < nab; i++) REAL(ab)[i] = 0.0;
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for(i = 0; i < na; i++)
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for(j = 0; j < nb; j++) REAL(ab)[i + j] += REAL(a)[i] * REAL(b)[j];
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UNPROTECT(3);
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return(ab);
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}
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#include "loopmacro.h"
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LOOPMACRO_C(convolve7)
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