Merge pull request #1877 from ChrisRackauckas-Claude/fix-ctarget-ssqrt

Map solver-safe functions (ssqrt/scbrt/slog) to math.h names in CTarget

Author: ChrisRackauckas

src/build_function.jl

@@ -675,6 +675,11 @@ numbered_expr(c,args...;kwargs...) = c
 numbered_expr(c::Num,args...;kwargs...) = error("Num found")
 
 
+# The solver introduces "safe" variants of some math functions that handle
+# negative/complex inputs in Julia. They have no C equivalent, so map them back
+# to the standard math.h names when generating C code.
+const c_safe_function_renames = Dict(:ssqrt => :sqrt, :scbrt => :cbrt, :slog => :log)
+
 # Replace certain multiplication and power expressions so they form valid C code
 # Extra factors of 1 are hopefully eliminated by the C compiler
 function coperators(expr)
@@ -684,6 +689,9 @@ function coperators(expr)
             coperators(e)
         end
     end
+    if expr.head == :call && expr.args[1] isa Symbol
+        expr.args[1] = get(c_safe_function_renames, expr.args[1], expr.args[1])
+    end
     for i in eachindex(expr.args)
         if expr.args[i] isa Rational
             expr.args[i] = float(expr.args[i]) # Evaluate rational numbers to floating-point

test/build_targets.jl

@@ -70,6 +70,22 @@ let
 end
 
 
+# Safe solver functions (ssqrt/scbrt/slog) must map to their math.h names in C
+# (https://github.com/JuliaSymbolics/Symbolics.jl/issues/1873)
+let
+    @variables y
+    expression = (1//2) * Symbolics.term(Symbolics.ssqrt, 4y) +
+                 Symbolics.term(Symbolics.scbrt, y) + Symbolics.term(Symbolics.slog, y)
+    cfunc = build_function([expression], y; target = Symbolics.CTarget(), expression = Val{true})
+
+    @test occursin("sqrt(", cfunc)
+    @test occursin("cbrt(", cfunc)
+    @test occursin("log(", cfunc)
+    @test !occursin("ssqrt", cfunc)
+    @test !occursin("scbrt", cfunc)
+    @test !occursin("slog", cfunc)
+end
+
 # Matrix StanTarget test
 let
     @variables x[1:4] y[1:4] z[1:4]