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+/* $OpenBSD: s_cpow.c,v 1.6 2013/07/03 04:46:36 espie Exp $ */
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+/*
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+ * Copyright (c) 2008 Stephen L. Moshier <[email protected]>
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+ *
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+ * Permission to use, copy, modify, and distribute this software for any
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+ * purpose with or without fee is hereby granted, provided that the above
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+ * copyright notice and this permission notice appear in all copies.
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+ *
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+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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+ */
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+
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+/* cpow
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+ *
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+ * Complex power function
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+ *
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+ *
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+ *
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+ * SYNOPSIS:
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+ *
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+ * double complex cpow();
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+ * double complex a, z, w;
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+ *
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+ * w = cpow (a, z);
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+ *
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+ *
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+ *
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+ * DESCRIPTION:
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+ *
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+ * Raises complex A to the complex Zth power.
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+ * Definition is per AMS55 # 4.2.8,
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+ * analytically equivalent to cpow(a,z) = cexp(z clog(a)).
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+ *
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+ * ACCURACY:
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+ *
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+ * Relative error:
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+ * arithmetic domain # trials peak rms
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+ * IEEE -10,+10 30000 9.4e-15 1.5e-15
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+ *
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+ */
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+
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+#include <complex.h>
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+#include <float.h>
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+#include <math.h>
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+
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+double complex
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+cpow(double complex a, double complex z)
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+{
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+ double complex w;
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+ double x, y, r, theta, absa, arga;
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+
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+ x = creal (z);
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+ y = cimag (z);
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+ absa = cabs (a);
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+ if (absa == 0.0) {
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+ return (0.0 + 0.0 * I);
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+ }
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+ arga = carg (a);
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+ r = pow (absa, x);
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+ theta = x * arga;
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+ if (y != 0.0) {
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+ r = r * exp (-y * arga);
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+ theta = theta + y * log (absa);
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+ }
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+ w = r * cos (theta) + (r * sin (theta)) * I;
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+ return (w);
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+}
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+
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+#if LDBL_MANT_DIG == DBL_MANT_DIG
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+__strong_alias(cpowl, cpow);
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+#endif /* LDBL_MANT_DIG == DBL_MANT_DIG */
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